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Next Article 
The Journal of Neuroscience, April 15, 1999, 19(8):2843-2851
Regulation of Intracellular Chloride by Cotransporters in
Developing Lateral Superior Olive Neurons
Yasuhiro
Kakazu1, 2,
Norio
Akaike1,
Soutaro
Komiyama2, and
Junichi
Nabekura1
Departments of 1 Physiology and
2 Otorhinolaryngology, Faculty of Medicine, Kyushu
University, Fukuoka 812-8582, Japan
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ABSTRACT |
The regulatory mechanisms of intracellular Cl
concentration ([Cl ]i) were
investigated in the lateral superior olive (LSO) neurons of various
developmental stages by taking advantage of gramicidin perforated patch
recording mode, which enables neuronal
[Cl ]i measurement. Responses to
glycine changed from depolarization to hyperpolarization during the
second week after birth, resulting from
[Cl ]i decrease. Furosemide equally
altered the [Cl ]i of both immature
and mature LSO neurons, indicating substantial contributions of
furosemide-sensitive intracellular Cl regulators;
i.e., K+-Cl cotransporter
(KCC) and
Na+-K+-Cl
cotransporter (NKCC), throughout this early development. Increase of
extracellular K+ concentration and replacement of
intracellular K+ with Cs+
resulted in [Cl ]i elevation at
postnatal days 13-15 (P13-P15), but not at P0-P2, indicating that
the mechanism of neuronal Cl extrusion is
sensitive to both furosemide and K+-gradient and
poorly developed in immature LSO neurons. In addition, removal of
extracellular Na+ decreased
[Cl ]i at P0-P2, suggesting the
existence of extracellular Na+-dependent and
furosemide-sensitive Cl accumulation in immature
LSO neurons. These data show clearly that developmental changes of
Cl cotransporters alter
[Cl ]i and are responsible for the
switch from the neonatal Cl efflux to the mature
Cl influx in LSO neurons. Such maturational
changes in Cl cotransporters might have the
important functional roles for glycinergic and GABAergic synaptic
transmission and the broader implications for LSO and auditory development.
Key words:
Cl -cotransporter; lateral superior
olive neurons; development; glycine; intracellular
Cl concentration; gramicidin perforated patch
clamp
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INTRODUCTION |
The lateral superior olive (LSO) is
the first auditory center that processes differences in the sound level
between the two ears (Wu and Kelly, 1992 ; Sanes, 1993 ). The LSO
receives glutamatergic innervation directly from the ipsilateral
cochlea nucleus and glycinergic inputs indirectly from the
contralateral cochlea nucleus via the medial nucleus of the trapezoid
body (Suneja et al., 1995 ; Vater, 1995). Removal of glycinergic
inputs before the onset of hearing results in a hypertrophic response
in the LSO (Sanes and Chokshi, 1992 ), suggesting that the glycinergic
transmission may play an important role in the development of LSO.
Several studies have recently shown that GABA and glycine evoke
membrane depolarization mediated by the efflux of
Cl in immature animals, resulting from a high
intracellular Cl concentration
([Cl ]i) in CNS during early
postnatal life (Luhmann and Prince, 1991 ; Chen et al., 1996 ; Backus et
al., 1998 ). This depolarization activates voltage-dependent
Ca2+ channels and reduces voltage-dependent
Mg2+ block of NMDA channels, resulting in
Ca2+ influx (Obrietan and van den Pol, 1997 ;
Leinekugel et al., 1997 ; Flint et al., 1998 ). This increase of
intracellular Ca2+ concentration
([Ca2+]i) plays an important
role in neuronal development (LoTurco et al., 1995 ; Ikeda et al., 1997 ;
Kirsch and Betz, 1998 ). With neuronal maturation, in turn,
[Cl ]i becomes lower, which results
in the hyperpolarization by GABA and glycine. The high and low
[Cl ]i in immature and in mature
neurons cannot be explained simply by a passive
Cl distribution (Alvarez-Leefmans, 1990 ). Although
the developmental change in [Cl ]i
might be caused by alterations of active mechanisms such as Na+-K+-Cl
(NKCC) and K+-Cl (KCC)
cotransporters,
Cl -HCO3
exchanger, Cl -ATPase and
Na+-dependent
Cl -HCO3
exchanger (Kaila, 1994 ), the exact mechanism has not yet been identified.
In the present study, the functional involvement of NKCC and KCC in
[Cl ]i control was examined in
developing rat LSO neurons between postnatal day 0 (P0) and P15. KCC
cotransports K+ and Cl
electroneutrally (1:1) and has been identified to neurons (Payne et
al., 1996 ). Using K+ gradient produced by
Na+-K+-ATPase, KCC expels
Cl with K+ out of the neuron
(Alvarez-Leefmans, 1990 ). On the other hand, NKCC, which carries
Na+, K+, and
Cl simultaneously and electroneutrally (1:1:2) in
the same direction, has been well characterized in a wide variety of
non-nervous (Haas, 1994 ) and nervous tissue (Ballanyi and Grafe, 1985 ;
Rohrbough and Spizter, 1996 ). NKCC is thought to contribute to
[Cl ]i increase. However, its
functional role in mammalian CNS is still unknown. Furthermore, it is
difficult to directly evaluate the functional roles of NKCC and KCC by
using traditional electrophysiological methods such as conventional
nystatin and amphotericin B perforated patch recordings because the net
ion movements by KCC and NKCC are electrically neutral and because
of the internal dialysis of the cell by the recording pipette in
these configurations (Ebihara et al., 1995 ). For this reason, we used a
gramicidin perforated patch recording mode, which allows electrical
recording without disruption of native
[Cl ]i (Akaike, 1997 ).
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MATERIALS AND METHODS |
Dissociated LSO neurons. The experimental protocol
was approved by the Ethics Review Committee for Animal Experimentation of our institution. Wistar rats aged P0-P15 (either sex) were decapitated under anesthesia with pentobarbitone sodium (55 mg/kg, i.p.), and 300 µm transverse slices of the brain, including the LSO,
were prepared with a microslicer (model DTK-1000, D.S.K.; model
VT-1000S, Leica, Nussloch, Germany). The slices were incubated for
10-20 min in incubation solution saturated with 95% O2
and 5% CO2 gas mixture at room temperature. They were then
treated with pronase (1 mg/6-20 ml) at 31°C for 20-45 min and
subsequently with thermolysin (1 mg/6-20 ml) under the same
conditions. The LSO region was identified on both sides under a
binocular microscope (model SMZ-1, Nikon) and punched out from the
slice using an electrolytically polished injection needle. The
micropunched pieces were triturated mechanically with fine glass
pipettes in the standard solution under a phase-contrast microscope
(model TMS-1, Nikon). The dissociated LSO neurons adhered to the bottom
of the Petri dish within 30 min. Neurons having their original
morphological features, such as the dendritic processes, were used in
the present experiments.
Solutions. The incubation solution for slices contained (in
mM): NaCl, 124; KCl, 5;
KH2PO4, 1.2; MgSO4,
1.3; CaCl2, 2.4; glucose, 10; and
NaHCO3, 24, pH 7.45, with 95% O2 and
5% CO2. External solutions used for electrical recordings
are listed in Table 1. For
Na+-free extracellular solution (NMDG solution),
Na+ was replaced with
N-methyl-D-glucosamine (NMDG)-OH, which was first dissolved in water and titrated with HCl at pH 7.0 ± 0.1. Active Cl concentration in the extracellular
solutions ( [Cl ]o) were
measured by Cl -sensitive electrode fabricated
using a liquid ion exchanger (WPI model IE-170) according to the method
reported by Komune et al. (1993) . The osmolarity of each solution was
measured by the osmometer (model OM802; Vogel). The patch pipette
solution for gramicidin perforated patch recording contained (in
mM) KCl, 150 and HEPES, 10. For the
Cs+-containing pipette, KCl was simply substituted
with CsCl. The patch pipette solution for nystatin perforated patch
recording contained (in mM): KCl, 50; K-gluconate, 100; and
HEPES, 10. All pipette solutions were buffered to pH 7.2 with Tris-OH.
Gramicidin was first dissolved in methanol to prepare a stock solution
of 10 mg/ml and then diluted to a final concentration of 100 µg/ml in
the pipette solutions. The gramicidin-containing solution was prepared
just before the experiment. When nystatin perforated patch mode was
used, the 10 mg/ml stock solution of nystatin (Akaike and Harata, 1994 )
was diluted to a final concentration of 400 µg/ml in the pipette
solutions.
Electrophysiological measurements. Ionic currents and
voltages were measured with a patch-clamp amplifier (EPC-7; List
Electronic), low-pass filtered at 1 kHz (FV-665; NF Electronic
Instruments), and monitored on both an oscilloscope (HS-5100A; Iwatsu)
and a pen recorder (Recti-Horiz-8K21; Nihondenki San-ei). In ramp
experiments, 3 × 10 7 M
tetrodotoxin (TTX) and 10 5 M
LaCl3 were added to the extracellular solutions. Ramp
voltage steps were applied by using a function generator (VP-7402A;
National). Data were also simultaneously recorded on a digital FM tape
recorder (RD-120TE; TEAC). Patch pipettes were constructed of
glass capillary tubes with an outer diameter of 1.5 mm prepared using a
vertical puller (PB-7; Narishige, Tokyo, Japan). The tip resistance of the electrodes was 4-8 M . The junction potential between the patch
pipettes and bath solution was nulled before gigaohm seal formation. After establishing contact with the cell surface, a gigaohm
seal was established by applying gentle suction to the patch pipette
interior. After the cell-attached configuration had been attained,
patch pipette potential was held at 50 mV, and 10 mV
hyperpolarizing step pulses with 300 msec duration were periodically
delivered to monitor the access resistance. In the gramicidin
perforated patch recording mode, the access resistance reached a steady
level of 20 M within 40 min after making the G seal. In the
conventional whole-cell configuration after rupturing gramicidin
perforated patch membrane by adding greater negative pressure to the
pipette interior, EGly moved to ~0 mV (+4.7 mV
by Nernst equation using active Cl concentration
in standard solution and 150 mM KCl pipette solution). Thus, the difference in EGly between gramicidin
perforated patch and conventional whole-cell recordings is a good
indicator for monitoring the recording condition. In all experiments,
75-80% series resistance compensation was used. All experiments were performed at room temperature (22-26°C).
Drugs. Rapid "square-wave" change of external solution
was performed with the "Y-tube" method described previously
(Nakagawa et al., 1990 ). Using this method, the external solution could be completely exchanged within 20 msec. Drugs used in the experiments were gramicidin D, thermolysin, ethacrynic acid (Sigma, St. Louis, MO),
pronase (Calbiochem, San Diego, CA), glycine (Kanto, Tokyo, Japan),
furosemide (Tokyo Kasei, Tokyo, Japan), and TTX (Sankyo, Tokyo, Japan).
Furosemide was dissolved in dimethyl sulfoxide (DMSO) at a
concentration of 1 M for the preparation of a stock solution, and the final DMSO concentration in the experiments did not
exceed 0.1%.
Statistical analysis. Data were expressed as mean ± SEM. Differences between groups were analyzed for statistical
significance using the Student's t test. A p
value <0.05 denoted the presence of a statistically significant difference.
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RESULTS |
Glycine responses in developing LSO neurons
Either conventional "open" patch whole-cell recording leads to
a rapid equilibration of intracellular cytoplasm with the pipette solution. Perforated patch recordings using nystatin or amphotericin B
while limiting dialysis nevertheless alter
[Cl ]i because of their
Cl permeability (Ebihara et al., 1995 ; Rhee
et al., 1994 ). Thus, in the present study, we used the gramicidin for
perforated patch recording on LSO neurons acutely dissociated from rats
aged between P0 and P15, because it allows selective permeation to
monovalent cations without fluxing any anions (Ebihara et al.,
1995 ).
To observe the developmental change in glycine responses, the rats were
divided into three age groups (P0-P2, P6-P8, and P13-P15). In the
current-clamp mode, 3 × 10 5 M
glycine induced a depolarization in 4 of 5 isolated LSO neurons at
P0-P2 (Fig.
1Aa) and a
hyperpolarization in four of four neurons at P13-P15 (Fig.
1Ab) in the standard extracellular solution.
The glycine-induced depolarization was associated with action
potentials. Both the glycine-induced depolarization (n = 2) and hyperpolarization (n = 2) were completely
blocked by 10 6 M strychnine,
suggesting that both responses were mediated by strychnine-sensitive
glycine receptors. During voltage-clamp at a VH of 50 mV,
3 × 10 5 M glycine elicited
inward currents at P0-P2 (20 of 37, Fig.
1Ba) and outward currents at P13-P15 (37 of
37, Fig. 1Bb) in the standard extracellular
solution.

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Figure 1.
Developmental changes in glycine responses in
isolated LSO neurons. Aa, At P0, 3 × 10 5 M glycine (Gly,
closed bars) induced depolarization associated with an
action potential (vertical line) in a current-clamp mode
under gramicidin perforated patch recording configuration.
Ab, At P15, glycine induced a hyperpolarization,
leading to the blockage of spontaneous action potentials. Resting
membrane potentials (Vrests) were 53 and
60 mV in a and b, respectively. In the
present study, test solutions were applied by the Y-tube method.
Ba, Left, In a voltage-clamp
mode, glycine-induced current (IGly)
at a holding potential (VH) of 50
mV was inward at P0 (bottom trace, I). Transient
vertical lines (i and ii) indicate the
current responses to steps in ramp voltage. The experimental protocol
for ramp voltage steps from 100 to 0 mV with 2 sec duration was made
before and during application of 3 × 10 5
M glycine (top trace,
V). Right, Current-voltage
relationships obtained from ramp voltage steps (i and
ii). The reversal potential of
IGly
(EGly) indicated by the intersection
of i and ii was 35 mV at P0.
Bb, Left, Glycine induced an
outward current at a VH of 50 mV at P14.
Right, EGly was 70 mV.
EGlys were obtained using the protocol
described above.
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Developmental changes in reversal potential of glycine responses
and [Cl ]i
The reversal potential of glycine responses
(EGly) was measured by voltage ramps
applied before and during 3 × 10 5
M glycine under voltage-clamp conditions (Fig.
1B). When the resting membrane potential
(Vrest) measured in the current-clamp mode was compared with EGly in each LSO neuron,
in >50% of LSO neurons at P0-P2 and P6-P8,
EGly was more depolarized than
Vrest (Fig. 2). On
the other hand, EGly was more hyperpolarized
than Vrest in ~90% of LSO neurons at P13-P15
(Fig. 2). Significant differences in the mean values of
Vrest were observed between P0-P2 and P13-P15
(p < 0.05) and between P6-P8 and P13-P15
(p < 0.05; Table
2). These findings agree with previous
studies showing more depolarized resting membrane potentials in
immature than in mature neurons (McCormick and Prince, 1987 ; Luhmann
and Prince, 1991 ).

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Figure 2.
Relationships between
Vrest and EGly in
developing LSO neurons. EGly is plotted as a
function of Vrest in each neuron examined at
P0-P2, P6-P8, and P13-P15 (n = 37, 19, and 37, respectively). Dashed lines indicate
EGly = Vrest. Open and
closed circles indicate the neurons with
EGly > Vrest and
EGly < Vrest, respectively. The percentages
of LSO neurons with EGly > Vrest are 65, 58, and 11% at P0-P2,
P6-P8, and P13-P15, respectively. Note that the number of neurons
with EGly > Vrest decreases with maturation.
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In our in vitro system, the glycine-induced responses in rat
LSO neurons were likely to result from a Cl
gradient favoring the flux of Cl through
glycine-operated Cl channels, and
EGly was considered to be the
Cl equilibrium potential, then the intact
intracellular Cl activity
( [Cl ]i) could be
calculated by the Nernst equation using the EGly and known extracellular Cl activities
( [Cl ]o; Table
1) for each LSO neuron (Ebihara et al.,
1995 ). The distributions of EGly and
[Cl ]i were skewed at P13~P15
(Fig. 3). Statistically significant differences in [Cl ]i were present
between P0-P2 and P13-P15 (p < 0.01), and
between P6-P8 and P13-P15 (p < 0.01; Table
2). These results indicate that glycine switched from an excitatory to
an inhibitory neurotransmitter because of a fall in
[Cl ]i during the second week after
birth in LSO neurons.

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Figure 3.
Developmental changes in the active intracellular
Cl concentration
( [Cl ]i) in LSO neurons.
Histograms of the percentages of LSO neurons are indicated as a
function of EGly (A)
and [Cl ]i
(B) at P0-P2, P6-P8, and P13-P15,
respectively. LSO neurons examined totaled 37, 19, and 37 at P0-P2,
P6-P8, and P13-P15, respectively.
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Regulation of [Cl ]i by
cation-chloride cotransporters during development
Several studies have demonstrated that KCC and NKCC cotransporters
play important roles in the maintenance of
[Cl ]i in both mature (Thompson and
Gähwiler, 1989 ; Zhang et al., 1991 ) and immature neurons
(Rohrbough and Spitzer, 1996 ). To examine the functional roles of these
cotransporters in maintaining [Cl ]i
in LSO neurons, we used the following strategies: (1) the
p-sulfamoylbenzoic acid loop diuretic furosemide is a potent
inhibitor of both cotransporters (Thompson and Gähwiler, 1989 ;
Haas, 1994 ); and (2) activation of KCC and NKCC requires the
simultaneous presence of K+ with
Cl , and of both Na+ and
K+ with Cl , respectively. The
absence of any cation inhibits the activity of these cotransporters
(Thompson and Gähwiler, 1989 ; Haas, 1994 ). The functional roles
of these cotransporters were examined using the recovery to glycine
responses and the resulting disruption of
[Cl ]i by the opening of
glycine-operated Cl channel.
Effect of furosemide
At P0-P2, the majority of IGlys exhibited
inward currents at a VH of 50 mV (Fig.
4A, top
trace). In the presence of 1 mM furosemide, the
amplitude of IGly gradually decreased and
finally became almost null. At P13-P15, furosemide gradually
diminished the outward IGly at a
VH of 50 mV (Fig. 4A,
bottom trace). These IGlys suppressed by
furosemide reappeared when VH was changed from
50 mV to a different membrane potential ( 30 mV at P0-P2 and 70
mV at P13-P15). Reappearance of IGlys was also
associated with a gradual decrease in the amplitude in the presence of
furosemide (Fig. 4A). Differences between
EGlys and VH became less
in the presence of furosemide at both ages (Fig. 4B).
These results indicate that furosemide-sensitive mechanisms, such as
KCC and NKCC, play a major role in maintaining
[Cl ]i in both immature and mature
LSO neurons.

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Figure 4.
Effects of furosemide on
EGly at two different ages.
A, Changes in IGlys during
application of 1 mM furosemide (shaded bar)
at P1 (top trace) and P14 (bottom trace).
In all following experiments, glycine was applied at an interval of 3 min (closed bars). The amplitude of inward (P0) and
outward IGlys (P14) became smaller at a
VH of 50 mV. A shift of
VH from 50 to 30 mV at P1 (top
trace) or to 70 mV at P14 (bottom trace)
allowed the reappearance of IGlys. However,
the amplitude of the reappeared IGlys also
decreased in both neurons. B, Changes in the driving
force
(EGly-VH)
for the glycine response are plotted as a function of time before,
during, and after application of 1 mM furosemide. Data are
the mean ± SEM of four to six neurons at each age. *Significant
difference in driving force between just before ( 2 min) and during
(10 min) the application of furosemide at each age
(p < 0.01; paired t
test).
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In addition to its blocking effect of cotransporters, furosemide also
acts as a Cl channel blocker on GABAA
receptor-containing 4 and 6 subunits (Korpi and Luddens, 1997 ).
However, this was not the case in furosemide-induced reduction of
IGly because under a nystatin perforated patch
recording, in which [Cl ]i is equal
to Cl concentration in the pipette solution
([Cl ]pipette), furosemide had little
effects on IGlys or EGlys
at both P0-P2 and P13-P15 (n = 4; data not shown),
suggesting that the channel-blocking effect of furosemide on the
glycine receptor was unlikely in LSO neurons. Thus, furosemide
effectively blocked intracellular Cl regulators in
both ages.
Effect of extracellular K+ on
[Cl ]i
A change in extracellular K+ concentration
([K+]o) from 5 to 20 mM resulted in a gradual reduction in the amplitude of
outward IGly at a VH of
50 mV at P13-P15 (Fig. 5A,
top trace). Indeed, in 20 mM
[K+]o,
[Cl ]i calculated from
EGly gradually increased to reach a new value, which was significantly higher than that at 5 mM
[K+]o at a VH
of 50 mV (Fig. 5B; n = 5;
p < 0.01; paired t test). Unlike
furosemide, the outward IGly changed to an
inward one in the presence of 20 mM
[K+]o at a VH
of 60 mV (Fig. 5A, bottom trace). In
addition, [Cl ]i in 20 mM [K+]o at a
VH of 60 mV was similar to that at
VH of 50 mV, which was greater than passive
[Cl ]i calculated from
VH and
[Cl ]o (10.6 mM at a
VH of 60 mV, Fig. 5B). After
reversal of [K+]o from 20 to 5 mM, [Cl ]i gradually
recovered to values similar to that before 20 mM [K+]o. This result indicates that
[K+]o-dependent
[Cl ]i regulation, which might be
less influenced by the membrane potential, plays an important role in
extruding Cl at P13-P15. On the other hand,
[Cl ]i at P0-P2 was less affected
by change in [K+]o (n = 4; Fig. 5B). These results indicate that
[K+]o-dependent
[Cl ]i regulation is well developed
at P13-P15, but not at P0-P2 in LSO neurons.

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Figure 5.
Effects of extracellular K+
concentration ([K+]o) on
[Cl ]i regulation. A,
An increase in [K+]o from 5 to 20 mM (shaded bar) shifted the base current to
inward direction and gradually decreased the amplitude of the outward
IGly at VHs of
50 mV (top trace) and 60 mV (bottom
trace). At VH of 60 mV, the
direction of IGly turned inward, but the
amplitude was stabilized later. After reversal of
[K+]o from 20 to 5 mM, the
level of base current and outward IGly
recovered. B, Changes in
[Cl ]i calculated from the Nernst
equation using EGly and
[Cl ]o (Table 1) were plotted as a
function of time. Solid and dashed horizontal
lines indicate the values of passive
[Cl ]i calculated from the Nernst
equation using [Cl ]o and a
VH of 50 mV (16.8 mM in 20 mM [K+]o) and 60
mV (11.3 mM in 20 mM
[K+]o), respectively. Note that
at P14, [Cl ]i in 20 mM [K+]o at
VH of 60 mV (closed
triangles) exceeded the passive
[Cl ]i (dashed
line). Two representative examples of
[Cl ]i at P0 (open
circles) were less influenced by 20 mM
[K+]o (n = 4).
Closed circles, Mean ± SEM of four neurons at
P13-P15. Other symbols show the data of each neuron. *Significant
difference in [Cl ]i between just
before ( 2 min) and during (10 min) the application of 20 mM [K+]o
(p < 0.01; paired t
test).
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Effect of intracellular K+ on
[Cl ]i
To examine the effect of intracellular K+
concentration ([K+]i) on
[Cl ]i, the 150 mM
K+ in the pipette solution
([K+]pipette) was replaced with 150 mM Cs+
([Cs+]pipette). Only after the access
resistance decreased to <20 M and became stable as confirmed by
rectangular pulses from 50 to 60 mV with 300 msec duration, we
measured IGly and EGly.
At P0-P2, [Cs+]pipette barely
influenced the inward IGly at a
VH of 50 mV (Fig. 6A, top
trace) and [Cl ]i (Fig.
6B) throughout recording period. On the other hand,
the amplitude of outward IGly gradually
decreased in [Cs+]pipette in all four
neurons examined at P13-P15 (Fig. 6A, bottom trace). In two of four neurons, IGly
turned inward at a VH of 50 mV. Furthermore,
although the initial values of
[Cl ]is in
[Cs+]pipette and
[K+]pipette were similar (Fig.
6B, arrow), which is consistent
with a low resting Cl permeability (Thompson and
Gähwiler, 1989 ), [Cl ]i in
[Cs+]pipette gradually reached a
significantly high value relative to that in
[K+]pipette. These results suggest
that [K+]i-dependent
[Cl ]i regulation exists at P13-P15,
assuming mainly extruding Cl out of the cell, but
is largely absent at P0-P2. When the results of high
[K+]o (Fig. 5) and
[Cs+]pipette experiments (Fig. 6) were
considered together, the mechanism of Cl
extrusion, which is sensitive to furosemide as well the
K+-gradient, i.e., KCC, is mainly responsible for
the lower [Cl ]i in mature LSO
neurons. However this Cl extrusion mechanism is
not well developed at P0-P2.

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Figure 6.
Effects of intracellular perfusion of
Cs+ on [Cl ]i
regulation. A, Top trace, The inward
IGly could be maintained at a
VH of 50 mV in 150 mM CsCl
pipette solution ([Cs+]pipette) at P0.
Bottom trace,
[Cs+]pipette gradually decreased the
amplitude of outward IGly at P14. In this
neuron, the direction of IGly was finally
changed to inward at a VH of 50 mV.
B, Changes in
[Cl ]i were plotted as a function
of time in 150 mM
[Cs+]pipette and 150 mM
KCl pipette solution ([K+]pipette).
Note that [Cl ]i in the
[Cs+]pipette obtained at the first
application of glycine was almost equal to that in
[K+]pipette at P13-P15
(arrow). However,
[Cl ]i in the
[Cs+]pipette gradually increased at
P13-P15. Data represent the mean ± SEM of four to five neurons
in each condition. * [Cl ]i after
the seventh application of glycine (18 min) was significantly higher
than the control (0 min) in P13-P15 LSO neurons in the
[Cs+]pipette
(p < 0.01; paired t
test).
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Effect of extracellular Na+ on
[Cl ]i
To explore the dependence of
[Cl ]i regulation on extracellular
Na+
([Na+]o),
[Na+]o was replaced by NMDG. However,
simple substitution of 150 mM Na+ with
150 mM NMDG decreased
[Cl ]o by 20 mM,
measured by the Cl -sensitive electrode (Table 1).
Indeed, this replacement changed the amplitude of
IGly and shifted EGly
even in nystatin perforated patch recordings (data not shown). To
maintain a constant [Cl ]o
throughout the experiment, we used a modified standard solution in
which 40 mM NaCl in standard solution was substituted with 80 mM mannitol. The osmolarity and
[Cl ]o of the modified standard
solution were almost equal to those in NMDG solution (Table 1). The
amplitudes of IGly and
EGly measured under a nystatin perforated patch
recording, in which [Cl ]i was
assumed to be equal to [Cl ]pipette,
using the modified standard solution was not different to that measured
using NMDG solution (n = 3; data not shown).
In gramicidin perforated patch recording, the amplitude of inward
IGly at a VH of 50 mV
gradually decreased after removal of
[Na+]o at P0-P2 (Fig.
7) but recovered to the initial values
after reversal of [Na+]o from 0 to 110 mM (n = 4). These results indicate that
[Na+]o-dependent
Cl accumulation into the cell exists at P0-P2. On
the other hand, the effect of removal of
[Na+]o on
[Cl ]i was variable at P13-P15
(n = 4). For example,
[Cl ]i gradually decreased and
then reached a plateau in [Na+]o-free
solution at P13-P15 (n = 2; Fig. 7B);
[Cl ]i gradually returned to that
before 0 mM [Na+]o.
However, in other neurons that exhibited a lower a
[Cl ]i in 110 mM
[Na+]o, removal of
[Na+]o did not affect
[Cl ]o (n = 2;
Fig. 7B). These data indicate that
[Na+]o-dependent
Cl accumulation plays an important role in
[Cl ]i regulation at P0-P2 but is
variable at P13-P15.

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Figure 7.
Effects of extracellular Na+
concentration ([Na+]o) on
[Cl ]i regulation. A,
At P0, glycine (closed bars) induced an inward current
at VH of 50 mV in the modified standard
solution (Table 1). A change of [Na+]o
from 110 to 0 mM (dotted bar) resulted in a
gradual reduction of inward IGly. Reversal
of [Na+]o to 110 mM
resulted in the return of amplitude of
IGly to basal levels. B,
Changes in [Cl ]i were plotted as
a function of time. In both two neurons at P0 (opened
circles), [Cl ]i gradually
decreased in the absence of [Na+]o. On
the other hand, the effect of 0 mM
[Na+]o on
[Cl ]i varied at P13
(n = 4). Two representative examples at P13-P15
showing the most and least affected neurons by 0 mM
[Na+]o (closed
circles).
|
|
These results indicate that the existence of
[Na+]o-dependent
Cl accumulation, i.e., NKCC, and lack of
K+ gradient-dependent Cl
extrusion, i.e., KCC, are responsible for the high
[Cl ]i in immature neurons. Indeed,
in LSO neurons at P0, which showed a stable amplitude of inward
IGly at a VH of 50 mV
in the standard extracellular solution, a shift of
VH to 30 mV altered the direction of
IGly to become outward in direction and led to a
gradual decrease in the amplitude of the outward
IGly. Finally, the IGly
became almost null (Fig.
8A).
[Cl ]i increased to the passive
[Cl ]i calculated from
VH and
[Cl ]o (passive
[Cl ]i at a
VH of 30 mV: 34.8 mM, Fig.
8B). This finding was compatible with the result that
[Cl ]i decrease after the efflux of
Cl through the glycine receptor can be supplied
and maintained by Cl accumulation mechanism, but
[Cl ]i increase by the influx of
Cl through the channels cannot be carried out of
the cell because of the lack of Cl extrusion
mechanism at P0.

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Figure 8.
Effect of VH on
[Cl ]i regulation in an immature LSO
neuron. A, At P0, glycine (closed bars)
induced a constant amplitude of inward IGly
at a VH of 50 mV in a standard
extracellular solution and 150 mM
[K+]pipette. A shift of
VH from 50 (left) to 30
mV (right) altered the direction of
IGly to outward. The amplitude of the
outward IGly gradually decreased and finally
became almost null. B, Changes in
[Cl ]i in the same neuron shown in
A were plotted as a function of time (opened
circles). Dashed lines indicate passive
[Cl ]is calculated from the Nernst
equation using [Cl ]o in the
standard extracellular solution and the value of
VH, where passive
[Cl ]is are 15.7 mM
and 34.8 mM at VH of 50 and
30 mV, respectively. Note that although
[Cl ]i could be maintained greater
than the passive [Cl ]i at a
VH of 50 mV, it was not lower than the
passive [Cl ]i at a
VH of 30 mV.
|
|
 |
DISCUSSION |
Developmental changes in glycine responses
Electrophysiological studies indicate that, during early postnatal
life, neuronal responses to GABA and glycine, the two major inhibitory
neurotransmitters in mature CNS, consist of depolarization rather than
hyperpolarization (Luhmann and Prince, 1991 ; Chen et al., 1996 ; Backus
et al., 1998 ). Present results showed a variability in
EGlys from one cell to another at each stage of
development (Figs. 2, 3), and glycine-induced depolarization was
observed in 65% LSO neurons at P0-P2 in the present study (Fig. 2).
However, others reported that glycine and electrical stimulation of the glycinergic inputs to LSO depolarized all LSO neurons at P0-P4 (Kandler and Friauf, 1995 ). The difference in the prevalence of immature LSO neurons with a depolarizing response to glycine might be
caused by the following reasons. (1) Because Kandler and Friauf used
external solutions containing HCO3 and
brain slice preparation, depolarization was probably caused by
Cl efflux as well as
HCO3 efflux (Staley et al., 1995 ) and
[K+]o accumulation (Kaila et al.,
1997 ). However, such mechanisms are unlikely to contribute to
glycine-induced depolarizations in the present study, because we used
extracellular standard solutions buffered with HEPES, not
HCO3 , and the dissociated neurons were
well superfused in our in vitro system. (2) Despite
carefully micropunching our specimen within the LSO, we cannot exclude
the possibility that some neurons other than those of LSO might be
used. (3) Heterogeneous development of neuronal characteristics has
been reported in various CNS areas including LSO. The prolonged
depolarization mediated by metabotropic glutamatergic receptors is
reported in 60% of LSO neurons in immature gerbils (Kotak and Sanes,
1995 ). A heterogeneous development of NMDA receptor response has been
reported in neurons of the nucleus tractus solitarius (Nabekura et al.,
1994 ). Thus, 65% of LSO neurons with glycine-induced depolarizing
responses at P0-P2 may reflect an inherent variability within the LSO.
Possible mechanisms involved in regulation of
[Cl ]i
In our studies, [Cl ]i decreased
markedly between P6-P8 and P13-P15, suggesting a change in the
regulatory mechanisms of [Cl ]i
during this period. Cl -ATPase, KCC, NKCC,
Cl -HCO3 exchange
and Na+-dependent
Cl -HCO3 exchange
have been implicated in the regulation of
[Cl ]i in neurons (Kaila, 1994 ).
However, others suggest that
Cl -HCO3 exchange
and Na+-dependent
Cl -HCO3 exchange
contribute minimally to [Cl ]i
regulation (Ballanyi and Grafe, 1985 ; Thompson et al., 1988 ). Furthermore, because we used HEPES-buffered solutions without HCO3 ,
Cl -HCO3 exchange
and Na+-dependent
Cl -HCO3 exchange
are likely to be negligible in the present study.
Cl -ATPase is classified as a primary active
Cl transport system driven directly by the
consumption of ATP (Inagaki et al., 1996 ). However, there is little
information regarding Cl -ATPase in neurons
(Kaila, 1994 ). Ethacrynic acid, which inhibits Cl -ATPase (Shiroya et al., 1989 ), was applied to
LSO neurons in a similar protocol to the furosemide work (Fig. 4) with
variable effects on the glycine response (data not shown). Thus, a
significant contribution of Cl -ATPase to the
developmental regulation of [Cl ]i
could not be confirmed in the present study.
KCC (Gillen et al., 1996 ; Payne et al., 1996 ) and NKCC (Gamba et al.,
1994 ; Payne and Forbush, 1994 ) have been identified. Recently, using
ribonuclease protection analysis and in situ hybridization, the developmental increase in the cation-Cl
cotransporters, including KCC and NKCC, was demonstrated in rat neocortex (Clayton et al., 1998 ). However, the functional involvement of KCC and NKCC in the regulation of
[Cl ]i in developing neurons is still
unclear. To examine the functional roles of these cotransporters in
regulating [Cl ]i, we used
several interventions to manipulate KCC and NKCC function, e.g.,
furosemide and alternation of
[K+]o,
[K+]i, and
[Na+]o. Because resting
Cl permeability is very low in neurons (Thompson
and Gähwiler, 1989 ), opening of Cl channels
only allows flux based on the difference between
[Cl ]i and
[Cl ]o and the membrane potential.
The inherent [Cl ]i-regulating
mechanism is responsible for the recovery of
[Cl ]i to its original value.
Furosemide
Although both KCC and NKCC have different affinities to
furosemide, they are almost completely inhibited by 1 mM
furosemide (Gillen et al., 1996 ). In the presence of 1 mM
furosemide, repetitive application of glycine gradually decreased the
amplitude of IGlys and brought
EGlys close to VH both at
P0-P2 and P13-P15 (Fig. 4). However, furosemide never reversed the
polarity of IGly, indicating that in the
presence of furosemide, [Cl ]i in
LSO neurons seems to be passively determined by
VH and
[Cl ]o irrespective of
developmental age. The results suggest that the furosemide-sensitive
mechanisms, such as NKCC in immature and KCC in mature, play a
substantial role in the maintenance of
[Cl ]i in both ages.
Effect of [K+]i,
[K+]o, and
[Na+]o on regulating
[Cl ]i
To evaluate the contribution of furosemide-sensitive
Cl extrusion mechanism to lower
[Cl ]i in LSO neurons, we used the
following two methods: (1) increases in
[K+]o, and (2) substitution of
[Cs+]i for
[K+]i. In high
[K+]o,
[Cl ]i gradually increased in LSO
neurons at P13~P15 (Fig. 5). The gradual increase of
[Cl ]i in
[Cs+]pipette was observed at P13~P15
(Fig. 6), which is consistent with the results of previous studies
demonstrating that EGABA and
EIPSP with Cs+-filled
microelectrodes are generally less negative than those with
K+-filled electrodes in adult CA3 hippocampal
neurons (Thompson and Gähwiler, 1989 ). In the experiments with
high [K+]o and the use of
[Cs+]pipette at P13~P15, the glycine
responses often reversed their polarities unlike furosemide (Figs.
5A, 6A, bottom trace).
Together these results indicate that the direction of
furosemide-sensitive Cl extrusion mechanism is
independent of VH and determined by
K+ gradient. On the other hand, high
[K+]o and
[Cs+]pipette did not affect
IGly and
[Cl ]i in immature LSO neurons
(Figs. 5B, 6B, open
circles). These findings suggest that the
K+ gradient-sensitive Cl
extrusion mechanism is not well developed in immature LSO neurons. Indeed, the amplitude of the outward IGly
decreased at a VH of 30 mV in immature neurons
in which inward IGly at a
VH of 50 mV was well maintained (Fig. 8).
These are agreeing that KCC2 expression appears perinatally and
increases dramatically after the first week of postnatal life (Clayton
et al., 1998 ).
NKCC catalyzes an electroneutral Cl uptake (Kaila,
1994 ) and has been identified in CNS neurons (Misgeld et al., 1986 ;
Rohrbough and Spitzer, 1996 ; Plotkin et al., 1997 ; Clayton et al.,
1998 ). Therefore, NKCC is a possible candidate transporter that
promotes accumulation of Cl into the cell and
whose activity is regulated by the Na+-gradient
(Ballanyi and Grafe, 1985 ). Indeed, displacement of [Na+]o with NMDG decreased
[Cl ]i in all immature LSO neurons
(Fig. 7), in which Na+-dependent mechanisms such as
NKCC were preferentially blocked because of the disappearance of
Na+ in both sides. In addition, although the
constant inward IGly was well maintained at a
VH of 50 mV at P0, the outward
IGly at a VH of 30 mV
became less evident and finally almost null (Fig. 8). The possible
explanations for the maintenance of Cl
accumulation at a VH of 50 mV and the
disappearance of Cl accumulation at a
VH of 30 mV in immature LSO neurons are: (1) a
flux of Cl through glycine-operated
Cl channels reduces the electrochemical gradients
of Cl at any VHs, but
[Cl ]i attained after the application
of glycine varies with VH. In the LSO neuron
shown in Figure 8, glycine induced an efflux of Cl
at a VH of 50 mV, which could decrease
[Cl ]i, resulting in
increasing a difference between
[Cl ]i and
[Cl ]o (Cl
chemical gradient) and thus increasing a driving force for inwardly directed NKCC. On the contrary, an influx of Cl by
glycine at a VH of 30 mV increased
[Cl ]i, resulting in reducing
a Cl chemical gradient and decreasing a driving
force for inwardly directed NKCC. Thus, Cl
accumulation adding to the passive
[Cl ]i by inward NKCC might not be
evident in function at a VH of 30 mV in the
LSO neuron shown in Figure 8; and (2) voltage dependency of NKCC
function could not be ruled out in the present study.
On the other hand, [Na+]o-dependent
accumulation varied at P13-P15. This is compatible with the report
that mRNA for NKCC1 (BSC2) shows a transient peak at early stages of
development but gradually declines with age in the rat brain (Plotkin
et al., 1997 ). Recent report demonstrates that
[Cl ]i is passively increased by
coincident membrane depolarization simultaneous with activation of
glycine-operated Cl channels in immature LSO
neurons (Backus et al., 1998 ). In our present study, however,
[Cl ]i was well maintained even at a
VH of 50 mV in immature neurons. Thus, our
data clearly indicate that genetically programmed changes of
[Cl ]i regulation occur during fetal
and postnatal LSO neurons.
In summary, our results indicate that in LSO neurons, (1)
[Cl ]i is mainly determined by a net
flux mediated by furosemide-sensitive mechanism, i.e., KCC and
NKCC, (2) high [Cl ]i in immature
neurons is caused by the presence of functional Na+-dependent cotransporter, i.e., NKCC and lack of
K+-dependent cotransporter, i.e., KCC, and (3) with
maturity, higher activity of K+-dependent
Cl extrusion relative to
Na+-dependent Cl accumulation
maintains [Cl ]i at low levels (Fig.
9).

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Figure 9.
A schematic illustration of the possible model
involved in the regulation of [Cl ]i
by cotransporters in developing LSO neurons. The function of NKCC,
furosemide, and [Na+]o-sensitive
inward Cl cotransporter decreases with age. KCC, a
furosemide-sensitive outward Cl cotransporter, is
only represented in mature LSO neurons. Thick arrows in
immature and mature LSO neurons indicate the direction of
Cl ion flux through the Cl
channels.
|
|
Functional implications of glycinergic inputs in developing
LSO neurons
The probability of firing action potentials in LSO neurons depends
on the timing differences of arrival from the contralateral (glycinergic) and ipsilateral (glutamatergic) inputs, a process that
encodes differences in interaural intensity and supplies the chief cues
to localize sounds in space (Wu and Kelly, 1992 ; Thomas et al.,
1996). Our present results suggest that there is a critical
transition in cotransporters, which occurs between P6-P8 and P13-P15.
As a result, [Cl ]i decreases and
glycine responses switch from depolarization to the adult pattern of
hyperpolarization. This transition occurs during a period at which
previous studies indicate that physiological hearing in rats and
gerbils begins (P12-P14; Sanes and Rubel, 1988 ; Kandler and Friauf,
1995 ). However, the physiological development of LSO neurons occurs
even in the absence of hearing experience (Kandler and Friauf, 1995 ).
The influence of hearing experience and synaptic activity to LSO in
controlling Cl transport remains to be elucidated.
GABA and glycine act neurotrophically in immature neurons (Ikeda et
al., 1997 ; Flint et al., 1998 ; Kirsch and Betz, 1998 ). Glycine-induced
depolarization might increase [Ca2+]i
through voltage-dependent Ca2+ channels and NMDA
channels in the LSO similar to its effects in other CNS areas during
development (LoTurco et al., 1995 ; Leinekugel et al., 1997 ; Obrietan
and van den Pol, 1997 ; Flint et al., 1998 ). Removal of glycinergic
inputs in LSO neurons in immature animals by cochlea ablation or
chronic strychnine application leads to a hypertrophic response in the
shape and length of their dendrites (Sanes and Chokshi, 1992 ) and
causes a depolarizing shift in IPSP reversal potential (Kotak and
Sanes, 1996 ). Thus, glycinergic depolarization may play an important
role in the development and refinement of LSO neurons. The appropriate
timing of changes in Cl transport with achieving
neuronal maturity assumes that glycinergic input will be inhibitory and
thus help mediate interaural intensity comparisons.
 |
FOOTNOTES |
Received Nov. 3, 1998; revised Jan. 19, 1999; accepted Jan. 26, 1999.
This work was supported by Grant-in-Aids (Nos. 10156231 and 09670046 to
J.N., and Nos. 10470009 and 10044301 to N.A.) from the Ministry of
Education, Science and Culture, Japan. We thank Profs. M. Andressen and
K. Kaila for critical reading of this manuscript.
Correspondence should be addressed to Dr. J. Nabekura, Department of
Physiology, Faculty of Medicine, Kyushu University, Fukuoka 812-82, Japan.
 |
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[PDF]
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M. Watanabe, H. Wake, A. J. Moorhouse, and J. Nabekura
Clustering of Neuronal K+-Cl- Cotransporters in Lipid Rafts by Tyrosine Phosphorylation
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J. G. Mancilla and P. B. Manis
Two Distinct Types of Inhibition Mediated by Cartwheel Cells in the Dorsal Cochlear Nucleus
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M. Watanabe, Y. Sakuma, and M. Kato
GABAA Receptors Mediate Excitation in Adult Rat GnRH Neurons
Biol Reprod,
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C. W. Habela, N. J. Ernest, A. F. Swindall, and H. Sontheimer
Chloride Accumulation Drives Volume Dynamics Underlying Cell Proliferation and Migration
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February 1, 2009;
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C. Gonzalez-Islas, N. Chub, and P. Wenner
NKCC1 and AE3 Appear to Accumulate Chloride in Embryonic Motoneurons
J Neurophysiol,
February 1, 2009;
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C. W. Habela, M. L. Olsen, and H. Sontheimer
ClC3 Is a Critical Regulator of the Cell Cycle in Normal and Malignant Glial Cells
J. Neurosci.,
September 10, 2008;
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H. I. Rocha-Gonzalez, S. Mao, and F. J. Alvarez-Leefmans
Na+,K+,2Cl- Cotransport and Intracellular Chloride Regulation in Rat Primary Sensory Neurons: Thermodynamic and Kinetic Aspects
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July 1, 2008;
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I. Milenkovic, M. Witte, R. Turecek, M. Heinrich, T. Reinert, and R. Rubsamen
Development of Chloride-Mediated Inhibition in Neurons of the Anteroventral Cochlear Nucleus of Gerbil (Meriones unguiculatus)
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U. Kim and L.-y. Chung
Dual GABAergic Synaptic Response of Fast Excitation and Slow Inhibition in the Medial Habenula of Rat Epithalamus
J Neurophysiol,
September 1, 2007;
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K. Achilles, A. Okabe, M. Ikeda, C. Shimizu-Okabe, J. Yamada, A. Fukuda, H. J. Luhmann, and W. Kilb
Kinetic Properties of Cl Uptake Mediated by Na+-Dependent K+-2Cl Cotransport in Immature Rat Neocortical Neurons
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C. Jean-Xavier, G. Z. Mentis, M. J. O'Donovan, D. Cattaert, and L. Vinay
Dual personality of GABA/glycine-mediated depolarizations in immature spinal cord
PNAS,
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S. Duvarci and D. Pare
Glucocorticoids Enhance the Excitability of Principal Basolateral Amygdala Neurons
J. Neurosci.,
April 18, 2007;
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M. A. Howard, R. M. Burger, and E. W Rubel
A Developmental Switch to GABAergic Inhibition Dependent on Increases in Kv1-Type K+ Currents
J. Neurosci.,
February 21, 2007;
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H. Wake, M. Watanabe, A. J. Moorhouse, T. Kanematsu, S. Horibe, N. Matsukawa, K. Asai, K. Ojika, M. Hirata, and J. Nabekura
Early Changes in KCC2 Phosphorylation in Response to Neuronal Stress Result in Functional Downregulation
J. Neurosci.,
February 14, 2007;
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A. Mizokami, T. Kanematsu, H. Ishibashi, T. Yamaguchi, I. Tanida, K. Takenaka, K. I. Nakayama, K. Fukami, T. Takenawa, E. Kominami, et al.
Phosholipase C-Related Inactive Protein Is Involved in Trafficking of {gamma}2 Subunit-Containing GABAA Receptors to the Cell Surface
J. Neurosci.,
February 14, 2007;
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C. Jean-Xavier, J.-F. Pflieger, S. Liabeuf, and L. Vinay
Inhibitory Postsynaptic Potentials in Lumbar Motoneurons Remain Depolarizing After Neonatal Spinal Cord Transection in the Rat
J Neurophysiol,
November 1, 2006;
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P. Blaesse, I. Guillemin, J. Schindler, M. Schweizer, E. Delpire, L. Khiroug, E. Friauf, and H. G. Nothwang
Oligomerization of KCC2 Correlates with Development of Inhibitory Neurotransmission
J. Neurosci.,
October 11, 2006;
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J.-E. Turner, S. Sedej, and M. Rupnik
Cytosolic Cl- ions in the regulation of secretory and endocytotic activity in melanotrophs from mouse pituitary tissue slices
J. Physiol.,
July 15, 2005;
566(2):
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W. J. Moody and M. M. Bosma
Ion Channel Development, Spontaneous Activity, and Activity-Dependent Development in Nerve and Muscle Cells
Physiol Rev,
July 1, 2005;
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X. Jin, J. R. Huguenard, and D. A. Prince
Impaired Cl- Extrusion in Layer V Pyramidal Neurons of Chronically Injured Epileptogenic Neocortex
J Neurophysiol,
April 1, 2005;
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G. B. Awatramani, R. Turecek, and L. O. Trussell
Staggered Development of GABAergic and Glycinergic Transmission in the MNTB
J Neurophysiol,
February 1, 2005;
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S. Sipila, K. Huttu, J. Voipio, and K. Kaila
GABA Uptake via GABA Transporter-1 Modulates GABAergic Transmission in the Immature Hippocampus
J. Neurosci.,
June 30, 2004;
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Y. Mizoguchi, T. Kanematsu, M. Hirata, and J. Nabekura
A Rapid Increase in the Total Number of Cell Surface Functional GABAA Receptors Induced by Brain-derived Neurotrophic Factor in Rat Visual Cortex
J. Biol. Chem.,
November 7, 2003;
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R. A. Wardle and M.-m. Poo
Brain-Derived Neurotrophic Factor Modulation of GABAergic Synapses by Postsynaptic Regulation of Chloride Transport
J. Neurosci.,
September 24, 2003;
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A. Gulacsi, C. R. Lee, A. Sik, T. Viitanen, K. Kaila, J. M. Tepper, and T. F. Freund
Cell Type-Specific Differences in Chloride-Regulatory Mechanisms and GABAA Receptor-Mediated Inhibition in Rat Substantia Nigra
J. Neurosci.,
September 10, 2003;
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E. H. Chang, V. C. Kotak, and D. H. Sanes
Long-Term Depression of Synaptic Inhibition Is Expressed Postsynaptically in the Developing Auditory System
J Neurophysiol,
September 1, 2003;
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C. Vale, J. Schoorlemmer, and D. H. Sanes
Deafness Disrupts Chloride Transporter Function and Inhibitory Synaptic Transmission
J. Neurosci.,
August 20, 2003;
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S. Titz, M. Hans, W. Kelsch, A. Lewen, D. Swandulla, and U. Misgeld
Hyperpolarizing Inhibition Develops without Trophic support by GABA in Cultured Rat Midbrain Neurons
J. Physiol.,
August 1, 2003;
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P. Van Damme, G. Callewaert, J. Eggermont, W. Robberecht, and L. Van Den Bosch
Chloride Influx Aggravates Ca2+-Dependent AMPA Receptor-Mediated Motoneuron Death
J. Neurosci.,
June 15, 2003;
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V. Balakrishnan, M. Becker, S. Lohrke, H. G. Nothwang, E. Guresir, and E. Friauf
Expression and Function of Chloride Transporters during Development of Inhibitory Neurotransmission in the Auditory Brainstem
J. Neurosci.,
May 15, 2003;
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Y. Mizoguchi, H. Ishibashi, and J. Nabekura
The action of BDNF on GABAA currents changes from potentiating to suppressing during maturation of rat hippocampal CA1 pyramidal neurons
J. Physiol.,
May 1, 2003;
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L. Nguyen, B. Malgrange, I. Breuskin, L. Bettendorff, G. Moonen, S. Belachew, and J.-M. Rigo
Autocrine/Paracrine Activation of the GABAA Receptor Inhibits the Proliferation of Neurogenic Polysialylated Neural Cell Adhesion Molecule-Positive (PSA-NCAM+) Precursor Cells from Postnatal Striatum
J. Neurosci.,
April 15, 2003;
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H. Toyoda, K. Ohno, J. Yamada, M. Ikeda, A. Okabe, K. Sato, K. Hashimoto, and A. Fukuda
Induction of NMDA and GABAA Receptor-Mediated Ca2+ Oscillations With KCC2 mRNA Downregulation in Injured Facial Motoneurons
J Neurophysiol,
March 1, 2003;
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R. A. DeFazio, S. Heger, S. R. Ojeda, and S. M. Moenter
Activation of A-Type {gamma}-Aminobutyric Acid Receptors Excites Gonadotropin-Releasing Hormone Neurons
Mol. Endocrinol.,
December 1, 2002;
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S. Uchida, E. Noda, Y. Kakazu, Y. Mizoguchi, N. Akaike, and J. Nabekura
Allopregnanolone enhancement of GABAergic transmission in rat medial preoptic area neurons
Am J Physiol Endocrinol Metab,
December 1, 2002;
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D. Billups and D. Attwell
Control of intracellular chloride concentration and GABA response polarity in rat retinal ON bipolar cells
J. Physiol.,
November 15, 2002;
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J. Nabekura, T. Ueno, A. Okabe, A. Furuta, T. Iwaki, C. Shimizu-Okabe, A. Fukuda, and N. Akaike
Reduction of KCC2 Expression and GABAA Receptor-Mediated Excitation after In Vivo Axonal Injury
J. Neurosci.,
June 1, 2002;
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I.-S. Jang, H.-J. Jeong, S. Katsurabayashi, and N. Akaike
Functional roles of presynaptic GABAA receptors on glycinergic nerve terminals in the rat spinal cord
J. Physiol.,
June 1, 2002;
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S. Boehm and H. Kubista
Fine Tuning of Sympathetic Transmitter Release via Ionotropic and Metabotropic Presynaptic Receptors
Pharmacol. Rev.,
March 1, 2002;
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T. Ueno, A. Okabe, N. Akaike, A. Fukuda, and J. Nabekura
Diversity of Neuron-specific K+-Cl- Cotransporter Expression and Inhibitory Postsynaptic Potential Depression in Rat Motoneurons
J. Biol. Chem.,
February 8, 2002;
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M. Shimura, N. Akaike, and N. Harata
Circadian rhythm in intracellular Cl- activity of acutely dissociated neurons of suprachiasmatic nucleus
Am J Physiol Cell Physiol,
February 1, 2002;
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M. Martina, S. Royer, and D. Pare
Cell-Type-Specific GABA Responses and Chloride Homeostasis in the Cortex and Amygdala
J Neurophysiol,
December 1, 2001;
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W. Kelsch, S. Hormuzdi, E. Straube, A. Lewen, H. Monyer, and U. Misgeld
Insulin-Like Growth Factor 1 and a Cytosolic Tyrosine Kinase Activate Chloride Outward Transport during Maturation of Hippocampal Neurons
J. Neurosci.,
November 1, 2001;
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M. Neunlist, K. Michel, D. Reiche, G. Dobreva, K. Huber, and M. Schemann
Glycine activates myenteric neurones in adult guinea-pigs
J. Physiol.,
November 1, 2001;
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J. Eilers, T. D Plant, N. Marandi, and A. Konnerth
GABA-mediated Ca2+ signalling in developing rat cerebellar Purkinje neurones
J. Physiol.,
October 15, 2001;
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P. Monsivais and E. W Rubel
Accommodation Enhances Depolarizing Inhibition in Central Neurons
J. Neurosci.,
October 1, 2001;
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Y.-F. Wang, X.-B. Gao, and A. N. van den Pol
Membrane Properties Underlying Patterns of GABA-Dependent Action Potentials in Developing Mouse Hypothalamic Neurons
J Neurophysiol,
September 1, 2001;
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I.-S. Jang, H.-J. Jeong, and N. Akaike
Contribution of the Na-K-Cl Cotransporter on GABAA Receptor-Mediated Presynaptic Depolarization in Excitatory Nerve Terminals
J. Neurosci.,
August 15, 2001;
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T. Lu and L. O Trussell
Mixed excitatory and inhibitory GABA-mediated transmission in chick cochlear nucleus
J. Physiol.,
August 15, 2001;
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A. Kulik, H. Nishimaru, and K. Ballanyi
Role of Bicarbonate and Chloride in GABA- and Glycine-Induced Depolarization and [Ca2+]i Rise in Fetal Rat Motoneurons In Situ
J. Neurosci.,
November 1, 2000;
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R. A. DeFazio, S. Keros, M. W. Quick, and J. J. Hablitz
Potassium-Coupled Chloride Cotransport Controls Intracellular Chloride in Rat Neocortical Pyramidal Neurons
J. Neurosci.,
November 1, 2000;
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V. C. Kotak and D. H. Sanes
Long-Lasting Inhibitory Synaptic Depression is Age- and Calcium-Dependent
J. Neurosci.,
August 1, 2000;
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Y. Kakazu, S. Uchida, T. Nakagawa, N. Akaike, and J. Nabekura
Reversibility and Cation Selectivity of the K+-Cl- Cotransport in Rat Central Neurons
J Neurophysiol,
July 1, 2000;
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C. Vale and D. H. Sanes
Afferent Regulation of Inhibitory Synaptic Transmission in the Developing Auditory Midbrain
J. Neurosci.,
March 1, 2000;
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C. Y. Chiang, C. L. Kwan, J. W. Hu, and B. J. Sessle
Effects of GABA Receptor Antagonist on Trigeminal Caudalis Nociceptive Neurons in Normal and Neonatally Capsaicin-Treated Rats
J Neurophysiol,
November 1, 1999;
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M.-R. Shen, C.-Y. Chou, K.-F. Hsu, H.-S. Liu, P. B. Dunham, E. J. Holtzman, and J. C. Ellory
The KCl cotransporter isoform KCC3 can play an important role in cell growth regulation
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