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The Journal of Neuroscience, May 15, 1998, 18(10):3589-3596
Evidence for Involvement of the cGMP-Protein Kinase G Signaling
System in the Induction of Long-Term Depression, But Not Long-Term
Potentiation, in the Dentate Gyrus In Vitro
Jianqun
Wu1,
Yue
Wang1,
Michael J.
Rowan2, and
Roger
Anwyl1
Departments of 1 Physiology and
2 Pharmacology and Therapeutics, Trinity College, Dublin 2, Ireland
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ABSTRACT |
The involvement of the cGMP-protein kinase G (PKG) signaling
pathway in the induction of long-term depression (LTD) and long-term potentiation (LTP) was investigated in the medial perforant path of the
dentate gyrus in vitro. Low-frequency stimulation
(LFS)-induced LTD of field EPSPs was inhibited by bath perfusion of the
selective soluble guanylyl cyclase inhibitor 1H-[1,2,4]
oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). LFS-induced LTD of EPSPs
and whole-cell patch-clamped EPSCs was also blocked by bath perfusion
and postsynaptic intracellular injection, respectively, of the
selective PKG inhibitor KT5823. Elevation of intracellular cGMP by
perfusion of the cGMP phosphodiesterase inhibitor zaprinast resulted in
induction of LTD of field EPSPs and EPSCs. Occlusion experiments showed
mutual inhibition between LFS-induced LTD and zaprinast-induced LTD.
The zaprinast-induced LTD of field EPSPs was inhibited by perfusion
of ODQ and KT5823. In addition, zaprinast-induced LTD of EPSCs was
inhibited by postsynaptic application of KT5823. Glutamate receptor
stimulation, especially that of metabotropic glutamate receptors
(mGluRs), was required for zaprinast-induced LTD, because cessation of
test stimulation or perfusion with the mGluR antagonist
(+)- -methyl-4-carboxyphenylglycine (MCPG) inhibited
zaprinast-induced LTD. No inhibitory effect of ODQ or KT5823 on the
induction of LTP of EPSPs or EPSCs was found. These data indicate that
the cGMP-guanyly cyclase-PKG signaling pathway in the dentate gyrus
is essential for induction of LTD, although not of LTP, in the dentate
gyrus.
Key words:
long-term depression; hippocampus; cGMP; protein kinase
G; EPSP; long-term potentiation
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INTRODUCTION |
Considerable evidence now exists for
a role of the diffusible molecule nitric oxide (NO) as an intercellular
messenger in the CNS (Schumann and Madison, 1994 ; Garthwaite and
Boulton, 1995). NO has been proposed to act as an intercellular
messenger in the induction of synaptic plasticity, including long-term
potentiation (LTP) and long-term depression (LTD), in the hippocampus.
A role of NO in LTP induction has been proposed from several lines of evidence. These include the ability of nitric oxide synthase (NOS) inhibitors, or agents which bind NO, to block the induction of LTP in
CA1 (Bohme et al., 1991; O'Dell et al., 1991; Schumann and Madison,
1991; Bon et al., 1992; Haley et al., 1992; Doyle et al., 1996) and
dentate gyrus (Wu et al., 1997), of NO donors to induce LTP in CA1
(Bohme et al., 1991), of endothelial (e) and neuronal (n) NOS knockout
mice to have reduced LTP in CA1 (Son et al., 1996), and also of
adenovirus-mediated inhibition and rescue of eNOS to have reduced or
normal LTP respectively in CA1 stratum radiatum (Kantor et al., 1996).
Recent evidence suggests that NO may be particularly important in
regulating the threshold of LTP induction, because NOS inhibitors
blocked LTP induced by weak, but not strong, afferent stimulation in
CA1 (Chetkovitch et al., 1993; Haley et al., 1993; O'Dell et al.,
1994; Malen and Chapman, 1997), and NO (Zhuo et al., 1993, 1994a) or NO
donors (Malen and Chapman, 1997) lowered the threshold for LTP
induction in CA1. There is also evidence that NO participates in the
induction of LTD. In CA1, NO was found to induce LTD when paired with
low-frequency stimulation of 0.25 Hz, a frequency that alone did not
induce LTD (Zhuo et al., 1994a). Moreover, NOS inhibitors blocked LTD induction in the CA1 (Izumi and Zorumski, 1995) and the dentate gyrus
(Wu et al., 1997).
Two intracellular targets have been proposed to mediate the action of
NO in its involvement in the induction of LTP and LTD: soluble
guanylase cyclase, resulting in elevation of cGMP and stimulation of
PKG (Gartwaite and Boulton, 1995), and ADP-ribosyltransferase (ADPRT)
(Schumann et al., 1994). Several studies have supported the involvement
of the former pathway in the induction of LTP. Inhibitors of soluble
guanylyl cyclase or of PKG prevented the induction of LTP in CA1 (Zhuo
et al., 1994b; Boulton et al., 1995), and cGMP analogs or activators of
PKG lowered the threshold for the induction of LTP (Zhuo et al., 1994b;
Arancio et al., 1995). One study has also presented evidence for the
involvement of ADPRT, with ADPRT activity stimulated by NO, and
inhibitors of ADPRT activity, blocking the induction of LTP (Schumann
et al., 1994).
In a recent study, we demonstrated an involvement of NO in the
induction of LTP and LTD in the dentate gyrus in vitro by
showing that NOS inhibitors blocked the induction of LTP and LTD (Wu et al., 1997). To elucidate the intracellular target of the NO, we have
investigated the effects of agents acting on the guanylyl cyclase-cGMP-PKG pathway. Our results indicate that the induction of
LTD, but not LTP, is dependent on the activation of the guanylyl cyclase-cGMP-PKG pathway.
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MATERIALS AND METHODS |
All experiments were performed on transverse slices of the rat
hippocampus (weight 40-80 gm). The brains were rapidly removed after
decapitation and placed in cold oxygenated (95%
O2/5% CO2) media. Slices were
cut at a thickness of 350 µm using a Campden vibroslice and placed in
a holding vessel containing oxygenated media at room temperature
(20-22°C). The slices were then transferred as required to a
submerged recording chamber and superfused continuously at a rate of 8 ml/min at 32°C.
The control media contained (in mM): NaCl 120, KCl 2.5, NaH2PO4 1.25, NaHCO3 26, MgSO4 2.0, CaCl2 2.0, D-glucose 10. All solutions contained 100 µM picrotoxin (Sigma, St.
Louis, MO) to block GABAA-mediated activity. Additional
drugs used were D-2-amino-phosphonopentanoate (AP5; Tocris
Cookson), 1-(2-trifluoromethyl-phenyl)imidazole (TRIM) (Lancaster
Synthesis), zaprinast (Sigma), (+)--methyl-4-carboxyphenylglycine (MCPG) (Tocris Cookson), 1H-[1,2,4]
oxadiazolo[4,3,-a] quinoxalin-1-one (ODQ) (Tocris Cookson), and
KT5823 (Calbiochem, La Jolla, CA). The patch-clamp electrode,
resistance 5-8 M , contained (in mM): potassium
gluconate 130, KCl 10, EGTA 10, CaCl2 1, MgCl2
3, HEPES 20, MgATP 5, NaGTP 0.5, QX 314 5, pH 7.2 (using KOH).
Whole-cell recordings from dentate granule cells were made using an
Axopatch 1D amplifier (5 kHz low-pass Bessel filter), as described
previously (O'Connor et al., 1995). The capacitative current was
always cancelled electronically, and the series resistance (15-30
M, as measured directly from the amplifier) was compensated by
60-70%. The mean input resistance was 295 ± 15 M, and the mean resting potential was  71 ± 3 mV. The input resistance was monitored continuously, and the recording was terminated if it varied
by >10%. Test EPSCs were recorded at a holding potential of 70 mV
in response to stimulation of the medial perforant path at a control
frequency of 0.033 Hz, with the stimulation intensity adjusted to evoke
an EPSC that was ~30% of the maximum amplitude, usually ~50-100
pA. LTD of EPSCs was evoked by low-frequency stimulation (LFS); 60 stimuli at 1 Hz were applied at 40 mV. The amplitude of LTD of EPSCs
was measured at 25 min after LFS. LTP of EPSCs was induced either by
eight trains of eight stimuli at 200 Hz, intertrain interval 0.5 Hz,
under current-clamp conditions, or by a pairing protocol consisting of
one train of eight stimuli applied at 0 mV under voltage-clamp
conditions. Full experiments were performed, providing that certain
criteria were met. These included a resting membrane potential of at
least 65 mV, a high input resistance (at least 200 M), and a low
threshold and steep input-output curve for the EPSCs.
Field EPSPs were recorded at a control test frequency of 0.033 Hz from
the medial perforant path in response to stimulation of this path. In
each experiment, an input-output curve (afferent stimulus intensity vs
EPSP amplitude) was plotted at the test frequency. For all experiments,
the amplitude of the test EPSP was adjusted to one-third of maximum,
usually ~1.0-1.2 mV. Paired-pulse stimulation was given at 0.017 Hz
with 25 msec intervals. Paired-pulse ratio was calculated as E1/E2 (E1,
the amplitude of the first EPSP; E2, the amplitude of the second EPSP)
and expressed as a percentage. LTD of field EPSPs was evoked by LFS
consisting of 900 stimuli at 1 Hz for 15 min, with the test stimulation
voltage remaining at the same amplitude during the LFS. The LTD of
field EPSPs was measured at 60-80 min after LFS or zaprinast
perfusion. LTP of field EPSPs was induced by eight trains of eight
stimuli at 200 Hz; intertrain interval was 0.2 Hz. Control and
experimental slices were routinely taken from the same hippocampus.
Recordings were analyzed using the pClamp6 (Axon Instruments).
Values are the mean ± SEM, and Student's t test was
used for statistical comparisons.
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RESULTS |
Inhibition of guanylyl cyclase prevents LTD, but not
LTP, induction
ODQ has been shown to be a selective inhibitor of soluble guanylyl
cyclase, with half-maximal inhibition of ~100 nM in the hippocampus (Garthwaite et al., 1995). ODQ has been shown previously to
inhibit the induction of both LTP in CA1 (Boulton et al., 1995) and LTD
in Purkinje cells of the cerebellum (Boxall and Garthwaite, 1996).
In the present experiments, ODQ was found to inhibit the induction of
LTD, but not of LTP. Figure
1A shows that after
perfusion with ODQ (10 µM) for 1 hr, which did not cause
a change in the field EPSP, application of LFS (900 stimuli at 1 Hz)
resulted in a markedly reduced amplitude of LTD of the field EPSP,
which measured 6 ± 5% (p < 0.01;
n = 7) compared with a set of control slices in which
LTD measured 36 ± 4% (n = 6). Short-term
depression, at 1 min after the LFS, was also reduced by ODQ, from
32 ± 3% in control to 15 ± 4% (p < 0.01; n = 7). In contrast, Figure
1B shows that ODQ did not inhibit the induction of
LTP of field EPSPs, with high-frequency (HFS)-induced LTP measuring
132 ± 6% in control and 129 ± 7% in slices perfused with
ODQ.
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Figure 1.
The soluble guanylase inhibitor ODQ prevents the
induction of LTD but not of LTP. A, In a control set of
slices, LFS (900 stimuli, 1 Hz) induced LTD of field EPSPs ( );
n = 6. In a second set of experimental slices, ODQ
(10 µM) perfused for 1 hr before LFS inhibited the
induction of LTD of field EPSPs ( ); n = 7. a-d show original traces of field EPSPs in control
baseline recording (a, b) after induction of LTD in
control slices (d) and after block of LTD
induction in the presence of ODQ. B, In a control set of
slices, HFS consisting of eight trains of eight stimuli at 200 Hz
induced LTP of field EPSPs (). In a second set of experimental
slices, ODQ perfused for 1 hr before HFS did not inhibit the induction
of LTP of field EPSPs ().
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Inhibition of PKG prevents induction of LTD but not of LTP
KT5823 is a selective PKG inhibitor with a
Ki of 234 nM (Kase, 1988; Nakanishi,
1989). It has been shown previously to inhibit LTP induction in CA1
(Zhou et al., 1994b) and to inhibit LTD in cerebellum Purkinje cells
(Ito and Karochet, 1990; Hartell, 1996).
KT5823 (10 µM) was found to inhibit the induction of LTD,
but not LTP. Figure 2A
shows that after extracellular application of KT5823 for 1 hr,
LFS-induced LTD of EPSPs was strongly inhibited and measured 5 ± 3.% (p < 0.01; n = 8) compared
with LTD of 29 ± 5% (n = 7) in control
slices.
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Figure 2.
The PKG inhibitor KT5823 (10 µM)
inhibits the induction of LTD but not of LTP. A, In a
control set of slices, LFS induced LTD of field EPSPs ();
n = 7. In a second set of experimental slices,
KT5823 prevented the induction of LTD of field EPSPs ();
n = 8. B, In a control set of
slices, LFS consisting of 60 stimuli at 1 Hz applied at 40 mV induced
LTD of EPSCs recorded under whole-cell patch-clamp conditions ();
n = 5. In a second set of experimental slices, LTD
of EPSCs was inhibited in cells filled with KT5823 by diffusion from
the patch pipette (); n = 5. C,
D, In control slices, HFS consisting of one train of eight
stimuli at 200 Hz (C) or eight trains of eight
stimuli at 200 Hz (D) induced LTP ();
n = 5. In experimental slices, LTP of EPSCs was not
inhibited in cells filled with KT5823 by diffusion from the patch
pipette when LTP was induced by one or eight trains of HFS (C,
D) (); n = 5. The original traces in
C show paired-pulse recordings of EPSCs in control
baseline recordings (a, b) and after induction of LTP
(c, d). E, The graph shows
that LTP of field EPSPs induced by HFS (8 trains of 8 stimuli at 200 Hz) is not blocked by extracellular bath application of KT5823, with
the amplitude of LTP induced in control () not significantly
different from that in KT5823 ().
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The action of KT5823 was also examined in whole-cell patch-clamp
recordings in which KT5823 was allowed to diffuse from the patch
pipette into the postsynaptic cell. In a previous study from this
laboratory, it has been shown that LTD in the dentate gyrus can be
induced by a brief LFS under mildly depolarized conditions (Wang et
al., 1997). In control patch-clamp recordings, LTD of EPSCs induced by
LFS (60 stimuli at 1 Hz, 40 mV) measured 36 ± 3%
(n = 5). However, LTD induction was strongly inhibited
in cells loaded with KT5823 (10 µM), with LTD measuring
2 ± 3% (n = 5; p < 0.01) (Fig.
2B).
LTP induced by HFS was not inhibited by KT5823, either applied to the
postsynaptic cell or perfused in the bath. Control LTP of EPSCs induced
by HFS consisting of either a series of eight trains of eight stimuli
(200 Hz) under current clamp (Fig. 2C) or one train of eight
stimuli (200 Hz) at 0 mV (Fig. 2D) induced LTP of
145 ± 3.7% (n = 5) and 138 ± 5.4%
(n = 5), respectively. In the presence of KT5823 (10 µM) in the patch pipette, HFS consisting of eight trains
of eight stimuli applied under current clamp (Fig. 2C) or
one train of eight stimuli at 0 mV (Fig. 2D) resulted
in LTP induction measuring 143 ± 5% (n = 5) and
141 ± 4% (n = 5), respectively, and the levels
of LTP were not significantly different from control. Bath perfusion of
KT5823 (10 µM) also did not block induction of LTP of
field EPSPs. In control slices, LTP induced by HFS measured 146 ± 12%, whereas in slices perfused with KT5823 for 1 hr, LTP measured
138 ± 7% (p > 0.05; n = 5) (Fig. 2E).
Inhibition of intracellular cGMP breakdown induces LTD
To investigate the effects of increasing the intracellular level
of cGMP, we prevented intracellular cGMP breakdown with the use of the
agent zaprinast, which is a selective inhibitor of cGMP-specific
phosphodiesterase (Beavo and Reifsnyder, 1990). Zaprinast has been
shown previously to induce LTD in Purkinje cells of the cerebellum
(Hartell, 1996).
Perfusion of zaprinast (20 µM) for 20 min induced LTD of
the field EPSP measuring 27 ± 4% (p < 0.01; n = 10) at 80 min after commencement of zaprinast
perfusion (Fig. 3A). Recording
of paired-pulse changes during the perfusion of zaprinast showed that
the paired-pulse depression present in control (19 ± 3%
depression) was reduced during the initial period of perfusion of
zaprinast (to 3 ± 2%), indicating that the initial period of
depression induced by zaprinast was mediated by a presynaptic decrease
in the probability of transmitter release. However, the decrease in
paired-pulse depression was transient, and it returned to control value
(18 ± 3%) by 40 min after perfusion of zaprinast was started,
although LTD was maintained for >80 min. Occlusion experiments showed
mutual block between the LFS-induced and the zaprinast-induced LTD.
First, zaprinast-induced LTD was found to occlude LFS-induced LTD. Thus
zaprinast-induced (20 µM) LTD measuring 29 ± 2%
(n = 5) resulted in a block of further LTD by LFS
(2 ± 2%; n = 5; p < 0.001)
(Fig. 3B). Second, LFS-induced LTD was found to occlude
zaprinast-induced LTD. Thus LFS-induced LTD measuring 38 ± 7%
resulted in a block of further LTD by zaprinast (3 ± 2%;
n = 5; p < 0.005) (Fig.
3C). These occlusion experiments demonstrate convincingly
that the long-lasting depression induced by zaprinast has
maintenance mechanisms identical to LFS-induced LTD.
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Figure 3.
The cGMP phosphodiesterase inhibitor cGMP induces
LTD. A, The top graph shows that the
perfusion of zaprinast (20 µM for 20 min) resulted in the
induction of LTD of the field EPSP; n = 10. The
bottom graph shows that the initial depression lasting
~30 min was accompanied by a decrease in paired-pulse depression,
indicating a presynaptic site of action. However, the remaining LTD was
not accompanied by a change in paired-pulse depression. The original
traces above the top graph show paired
pulse-recordings of EPSPs in control baseline recordings
(a), 10 min after washout of zaprinast
(b) and 50 min after washout of zaprinast
(c). The original traces below the
bottom graph are the superimposed traces of
a and the normalized first EPSP of b,
showing the early change in paired-pulse depression during the
zaprinast perfusion. a and c are
a and the normalized first EPSP of c,
showing the lack of change of paired pulse depression during LTD.
B, Occlusion experiment showing that after induction of
LTD by zaprinast, LFS did not induce further significant LTD;
n = 5. The original traces are paired-pulse
recordings of field EPSPs in control baseline recordings
(a), 40 min after application of zaprinast
(b), and 40 min after LFS
(c). C, Occlusion experiment
showing that after induction of LTD by LFS, zaprinast did not induce
further significant LTD; n = 5. The original traces
are paired-pulse recordings of field EPSPs in control baseline
recordings (a), 15 min after LFS
(b) and 40 min after application of zaprinast
(c).
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To investigate whether the zaprinast-induced LTD, like the LFS-induced
LTD, involved activation of soluble guanylyl cyclase and PKG, zaprinast
was applied in the presence of the inhibitor of soluble guanylyl
cyclase ODQ (10 µM) or the PKG inhibitor KT5823 (10 µM). After perfusion of ODQ or KT5823 for 1 hr, zaprinast induced a short-term depression, but LTD was strongly inhibited. In
ODQ, zaprinast-induced LTD measured 5 ± 5%
(p < 0.01; n = 5) (Fig.
4A), and in KT5823,
zaprinast induced a small potentiation rather than LTD (to 107 ± 7%; p < 0.01; n = 7) (Fig.
4B). Short-term depression at 1 min after washout of
zaprinast was not inhibited by ODQ (33 ± 4% in control vs
30 ± 3% in ODQ) but was reduced in KT5823 (17 ± 2%;
p < 0.05; n = 7). KT5823 applied
postsynaptically (10 µM in the patch pipette) also
blocked LTD induction. In control experiments, zaprinast induced LTD
measuring 36 ± 3% (n = 5) (Fig. 4C).
In cells loaded with KT5823, zaprinast-induced LTD was strongly inhibited, measuring 2 ± 3% (p < 0.01;
n = 5). Simultaneous measurements of the field EPSP
were made in three experiments in which the cell was loaded with
KT5823. Zaprinast induced LTD of the field EPSP at a level similar to
that found previously, although LTD induction of the EPSC was blocked
(Fig. 4D).
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Figure 4.
Zaprinast-induced LTD is blocked by the inhibitors
of soluble guanylyl cyclase ODQ and PKG inhibitor KT5823.
A, Perfusion of the soluble guanylyl cyclase inhibitor
ODQ (10 µM) inhibited the LTD of field EPSPs induced by
perfusion of zaprinast (20 µM); n = 5. B, Perfusion of the PKG inhibitor KT5823 (10 µM) inhibited the LTD induced by perfusion of zaprinast
(20 µM); n = 7. C, In
a set of control experiments, zaprinast (20 µM) induced
LTD of EPSCs (). In the presence of postsynaptic KT5823 (10 µM in the patch pipette), zaprinast-induced LTD was
inhibited (); n = 5. D, An
experiment in which the presence of KT5823 in the patch pipette
inhibited the zaprinast-induced LTD of EPSCs but did not inhibit the
zaprinast-induced LTD of the field EPSP. The original traces show
paired-pulse recordings of field EPSPs in control baseline recordings
(a) and after perfusion of zaprinast
(c), which induced LTD, and also of EPSCs in
control baseline recordings and in the postsynaptic presence of KT5823
(d), which blocked the induction of LTD.
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Activation of mGluRs is required for zaprinast-induced LTD
To identify the receptor involved in the zaprinast-induced LTD,
experiments were performed involving application of zaprinast in the
presence of inhibitors of NMDA receptor (NMDAR) and mGluR and also with
cessation of test stimuli during zaprinast application. Cessation of
test stimuli during zaprinast application resulted in an inhibition of
LTD induction (4 ± 3%; n = 5; p > 0.05) at 80 min after zaprinast application (Fig.
5A). The mGluR antagonist MCPG
(500 µM), perfused for 1 hr before zaprinast application, also prevented LTD induction (8 ± 8%; n = 5;
p > 0.05) at 80 min after zaprinast application (Fig.
5B). However, the NMDAR antagonist AP5 did not inhibit LTD
induction. After perfusion of AP5 for 1 hr, application of zaprinast
induced LTD measuring 33 ± 2% (p < 0.01;
n = 5) (Fig. 5C).
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Figure 5.
The induction of LTD by zaprinast (20 µM) requires test stimulation and activation of mGluRs,
but not NMDAR. A, Cessation of test stimulation during
perfusion of zaprinast significantly reduced the induction of LTD by
zaprinast, although not of a short-term depression;
n = 5. The original traces show recordings of EPSPs
in control baseline recording (a) and after the
induction of LTD by zaprinast (b).
B, The mGluR antagonist MCPG (500 µM)
significantly reduced the induction of LTD by zaprinast;
n = 5. The original traces show recordings of EPSPs
in control baseline recordings (a) and after the
induction of LTD by zaprinast (b).
C, The NMDAR antagonist AP5 did not significantly
prevent LTD induction by zaprinast; n = 5. The
original traces show field EPSPs in the control baseline recording
(a) and after the induction of LTD by zaprinast
(b).
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DISCUSSION |
The results of this study present evidence that the induction of
LTD in the dentate gyrus involves the soluble guanylyl
cyclase-cGMP-PKG signaling pathway. The initial step in this
intracellular pathway, the production of NO, was shown to be important
in LTD induction in the dentate gyrus in a previous study from this
laboratory, with the NOS inhibitors TRIM and 3-bromo-7-nitro-indazole
blocking the induction of LTD (Wu et al., 1997). The involvement of
cGMP in LTD induction was demonstrated in the present study by the ability of raised levels of cGMP (by the use of the selective cGMP
phosphodiesterase inhibitor zaprinast) to induce LTD, whereas an
involvement of soluble guanylyl cyclase and PKG was demonstrated by ODQ
and KT5823, respectively, inhibitors of these messengers, to strongly
inhibit LTD induction produced by both LFS and zaprinast. In the CA1
hippocampus, evidence for a role of the cGMP signaling pathway in LTD
induction is more debatable. NOS inhibitors were found to block the
induction of LTD (Izumi and Zorumski, 1995), and NO directly induced
LTD when paired with low-frequency stimulation (Zhuo et al., 1994a) in
CA1. In addition, a very recent study has shown that ODQ inhibits LTD
induction in CA1 (Gage et al., 1997). However, in other studies in CA1,
NOS inhibitors did not prevent LTD induction (Cummings et al., 1994),
NO donors were shown to induce only a short-term depression and not LTD
(Boulton et al., 1994), and moreover NO donors did not enhance either
maximal or weak LTD (Malen and Chapman, 1997). In addition, in CA1,
double knockout for nNOS and eNOS did not show significantly reduced LTD (Son et al., 1996), and zaprinast induced only a short-term depression (Boulton et al., 1994). We therefore suggest that the NO-cGMP signaling pathway may play a much more prominent role in LTD
induction in the dentate gyrus than in CA1, perhaps because of a higher
concentration of nNOS in the dentate gyrus than in CA1 (see below).
The involvement of the NO-cGMP signaling pathway in the induction of
LTD in the dentate gyrus shows striking similarities with the induction
of LTD in Purkinje cells of the cerebellum. There is very strong
evidence for the involvement of NO in the induction of Purkinje cell
LTD (Garthwaite and Boulton, 1995; Lev-Ram et al., 1997). In addition,
induction of LTD in Purkinje cells was blocked by the guanylyl cyclase
inhibitor ODQ (Boxall and Garthwaite, 1996) and by PKG inhibitors,
including KT5823 (Lev-Ram et al., 1997), and LTD was induced by
photorelease of caged cGMP (Lev-Ram et al., 1997) and by zaprinast
(Hartell, 1996).
NO has been proposed to act as a retrograde messenger in the induction
of LTP in CA1 hippocampus, being released from the postsynaptic cell
and then diffusing to the presynaptic terminal for its action in
increasing transmitter release (O'Dell et al., 1991; Arancio et al.,
1996). In contrast, in the cerebellum, NO has been proposed to act as
an anterograde messenger, being released from parallel fiber terminals
and diffusing to the Purkinje cell where it mediates LTD (Lev-Ram et
al., 1995, 1997). The site of release of NO is likely to be
postsynaptic in the hippocampus (O'Dell et al., 1991; Arancio et al.,
1996), with NOS being expressed postsynaptically in hippocampal
pyramidal and granule cells in the mouse, rat, and human dentate gyrus
(Dinnerman et al., 1994; Brenman et al., 1996; Hara et al., 1996; Doyle
and Slater, 1997; Eliasson et al., 1997). In the present study,
postsynaptic application of the PKG inhibitor KT5823 blocked LFS- and
zaprinast-induced LTD. This suggests that the PKG is produced
postsynaptically, which would be consistent with NO acting as an
intercellular postsynaptic messenger in the dentate gyrus,
diffusing between adjacent postsynaptic cells in its involvement in
mediating LTD. However, the possibility that KT5823 diffused to the
presynaptic terminal after its postsynaptic application in the present
studies cannot be eliminated. In this case, NO would then act as a
retrograde messenger and stimulate presynaptic PKG and subsequently
affect transmitter release.
The NO involved in LTD induction in the dentate gyrus may be derived
from nNOS, because nNOS shows particularly dense immunohistochemical staining in the dentate gyrus, much higher than in CA1 (Brenman et al.,
1996; Eliasson et al., 1997). Moreover, the NOS inhibitor TRIM, which
was found to block LTD induction in the dentate gyrus in a previous
study (Wu et al., 1997), is selective for nNOS. It is of interest that
the similarity of the dentate gyrus and the cerebellum regarding LTD
induction also applies to the distribution of nNOS, with the molecular
and granular layers of the cerebellum having high levels of nNOS
(Brenman et al., 1996; Eliasson et al., 1997).
Stimulation at the test frequency was found to be essential for the
induction of LTD, and cessation of test stimulation prevented the
induction of LTD. Such stimulation may be necessary to activate mGluR,
because blocking of mGluR with the antagonist MCPG was found to inhibit
the induction of zaprinast-induced LTD. Previous studies from this
laboratory have shown that activation of mGluR is essential for the
induction of LTD in the dentate gyrus, with the mGluR group I and II
antagonist MCPG (O'Mara et al., 1995) and the mGluRII antagonist MCCG
(Huang et al., 1997) inhibiting LTD induction, and the mGluR agonist
1S,3R-ACPD directly inducing LTD (O'Mara et al., 1995). mGluR
activation is also known to be essential for the induction of
cerebellar LTD (Conquet et al., 1994; Hartell, 1994), including
zaprinast-induced LTD (Hartell, 1996).
The induction of LTP in the dentate gyrus was found to be prevented by
NOS inhibitors in a previous study in this laboratory, demonstrating an
involvement of NOS in LTP induction (Wang et al., 1997). However, in
this study, LTP induction was not prevented by inhibiting soluble
guanylyl cyclase with ODQ or inhibiting PKG with KT5823. These
experiments suggest that the target site for the action of NO is not
the cGMP pathway. A likely alternative target for NO is an ADP
ribosyltransferase. It has been proposed previously that an ADP
ribosyltransferase is the target of NO in CA1, because NO dramatically
increased ADP ribosyltransferase activity in CA1, whereas inhibitors of
ADP ribosyltransferase prevented LTP induction (Schumann et al.,
1994).
| |
FOOTNOTES |
Received Dec. 11, 1997; revised March 3, 1998; accepted March 5, 1998.
This work was supported by grants from the Health Research Board,
Ireland, the Wellcome Trust, and the European Union.
Correspondence should be addressed to J. Wu, Department of Physiology,
Trinity College, Dublin 2, Ireland.
| |
REFERENCES |
-
Arancio O,
Kandel ER,
Hawkins RD
(1995)
Activity-dependent long-term enhancement of transmitter release by presynaptic 3', 5'-cyclic GMP in cultured hippocampal neurons.
Nature
376:74-80[Medline].
-
Arancio O,
Kiebler M,
Lee J,
Lev-Ram V,
Tsien RY,
Kandel ER,
Hawkins RD
(1996)
Nitric oxide acts directly in the presynaptic neuron to produce long-term potentiation in cultured hippocampal neurons.
Cell
87:1025-1035[Web of Science][Medline].
-
Beavo JA,
Reifsnyder DH
(1990)
Primary sequence of cyclic nucleotide phosphodiesterase isozymes and the design of selective inhibitors.
Trends Pharmacol Sci
11:150-155[Medline].
-
Bohme GA,
Bon C,
Stutzmann JM,
Doble A,
Blanchard JC
(1991)
Possible involvement of nitric oxide in long-term potentiation.
Eur J Pharmacol
199:379-381[Web of Science][Medline].
-
Bon C,
Bohme A,
Doble A,
Blanchard JC
(1992)
A role for nitric oxide in long-term potentiation.
J Neurosci
4:420-424[Abstract].
-
Boxall AR,
Garthwaite J
(1996)
Long-term depression in rat cerebellum requires both NO synthase and NO-sensitive guanylyl cyclase.
Eur J Neurosci
8:2209-2212[Web of Science][Medline].
-
Boulton CL,
Irving AJ,
Southam E,
Potier B,
Garthwaite J,
Collingridge GL
(1994)
The nitric oxide-cyclic GMP pathway and synaptic depression in rat hippocampal slices.
Eur J Neurosci
6:1528-1535[Web of Science][Medline].
-
Boulton CL,
Southam E,
Garthwaite J
(1995)
Nitric oxide-dependent long-term potentiation is blocked by a specific inhibitor of soluble guanylyl cyclase.
Neuroscience
69:699-703[Web of Science][Medline].
-
Brenman JE,
Chao DS,
Gee SH,
McGee AW,
Craven SE,
Santillano DR,
Wu Z,
Huang F,
Xia H,
Peters MF,
Froehner SC,
Bredt DS
(1996)
Interaction of nitric oxide synthase with the postsynaptic density protein PSD-95 and -syntrophin mediated by PDZ domains.
Cell
84:757-767[Web of Science][Medline].
-
Chetkovitch DM,
Klann E,
Sweatt JD
(1993)
Nitric oxide synthase-independent long-term potentiation in area CA1 of hippocampus.
NeuroReport
4:919-922[Web of Science][Medline].
-
Conquet F,
Bashir ZA,
Davies CH,
Daniel H,
Feraguti F,
Bordi F,
Franz-Bacon K,
Reggiani A,
Matarese V,
Conde F,
Collingridge GL,
Crepel F
(1994)
Motor deficit and impairment of synaptic plasticity in mice lacing mGluRI.
Nature
372:237-243[Medline].
-
Cummings JA,
Nicola SM,
Malenka RC
(1994)
Induction in the rat hippocampus of long-term potentiation and long-term depression in the presence of a nitric oxide synthase inhibitor.
Neurosci Lett
176:110-114[Web of Science][Medline].
-
Dinnerman JL,
Dawson TD,
Scell MJ,
Snowman A,
Snyder SH
(1994)
Endothelial nitric oxide synthase localized to hippocampal pyramidal cells: implication for synaptic plasticity.
Proc Natl Acad Sci USA
91:4214-4218[Abstract/Free Full Text].
-
Doyle CA,
Slater P
(1997)
Localization of neuronal and endothelial nitric oxide synthase isoforms in human hippocampus.
Neuroscience
76:387-395[Medline].
-
Doyle C,
Holscher C,
Rowan MJ,
Anwyl R
(1996)
The selective neuronal NO synthase inhibitor 7-nitro-indazole blocks both long-term potentiation and depotentiation of field EPSPs in rat hippocampal CA1 in vivo.
J Neurosci
16:418-424[Abstract/Free Full Text].
-
Eliasson MJL,
Blackshaw S,
Schell MJ,
Snyder SH
(1997)
Neuronal nitric oxide synthase alternatively spliced forms: prominent functional localization in the brain.
Proc Natl Acad Sci USA
94:3396-3401[Abstract/Free Full Text].
-
Gage AT,
Reyes M,
Stanton PK
(1997)
Nitric oxide-guanylyl cyclase-dependent and independent components of multiple forms of long-term synaptic depression.
Hippocampus
7:286-295[Web of Science][Medline].
-
Garthwaite J,
Boulton CL
(1995)
Nitric oxide signaling in the central nervous system.
Annu Rev Physiol
57:683-706[Web of Science][Medline].
-
Garthwaite J,
Sotham E,
Boulton CL,
Neilson EB,
Schmidt K,
Mayer B
(1995)
Potent and selective inhibition of nitric oxide-sensitive guanylyl cyclase by (1H-[1,2,4] oxadiazolo[4,3,-a]quinoxalin-1-one).
Mol Pharmacol
48:184-188[Abstract].
-
Haley JE,
Wilcox GL,
Chapman PF
(1992)
The role of nitric oxide in hippocampal long-term potentiation.
Neuron
8:211-216[Web of Science][Medline].
-
Haley JE,
Malen P,
Chapman PF
(1993)
Nitric oxide synthase inhibitors block long-term potentiation induced by weak but not strong tetanic stimulation at physiological brain temperatures in rat hippocampal slices.
Neurosci Lett
160:85-88[Web of Science][Medline].
-
Hara H,
Waeber PL,
Huang PL,
Fuji M,
Fishman MC,
Moskowitz MA
(1996)
Brain distribution of nitric oxide synthase in neuronal or endothelial nitric oxide synthase mutant mice using [H]L-N-nitro-arginine autoradiography.
Neuroscience
75:881-890[Web of Science][Medline].
-
Hartell NA
(1994)
Induction of cerebellar long-term depression requires activation of glutamate metabotropic receptors.
NeuroReport
5:913-916[Web of Science][Medline].
-
Hartell NA
(1996)
Inhibition of cGMP breakdown promotes the induction of cerebellar long-term depression.
J Neurosci
16:2881-2890[Abstract/Free Full Text].
-
Huang LQ,
Rowan MJ,
Anwyl R
(1997)
mGluRII agonist inhibition of LTP induction, and mGluRII antagonist inhibition of LTD induction, in the dentate gyrus in vitro.
NeuroReport
8:687-693[Web of Science][Medline].
-
Ito M,
Karochet L
(1990)
Receptor subtypes involved in, and time course of, the long-term depression of glutamate receptors in cerebellar Purkinje cells.
Neurosci Res
14:27-38.
-
Izumi Y,
Zorumski CFX
(1995)
Nitric oxide and long-term synaptic depression in the rat hippocampus.
NeuroReport
4:1131-1134.
-
Kantor DB,
Lanzrein M,
Stary SJ,
Sandoval GM,
Smith WB,
Sullivan BM,
Davidson N,
Schuman EM
(1996)
A role for endothelial NO synthase in LTP revealed by adenovirus-mediated inhibition and rescue.
Science
274:1744-1748[Abstract/Free Full Text].
-
Kase H
(1988)
New inhibitors of protein kinases from microbial source.
In: Biology of actinomycetes. Proceedings of Seventh International Symposium on Biology of Actinomycetes (Okami Y,
Beppu T,
Ogawara H,
eds), pp 159-164. Tokyo: Japan Scientific Societies.
-
Lev-Ram V,
Makings LR,
Keitz PF,
Kao JP,
Tsien RY
(1995)
Long-term depression in cerebellar Purkinje neurons results from coincidence of nitric oxide and depolarization-induced Ca transients.
Neuron
15:408-414.
-
Lev-Ram V,
Jiang T,
Wood J,
Lawrence DS,
Tsien RY
(1997)
Synergies and coincidence requirements between NO, cGMP and Ca in the induction of cerebellar long-term depression.
Neuron
18:1025-1038[Web of Science][Medline].
-
Malen PL,
Chapman PF
(1997)
Nitric oxide facilitates long-term potentiation, but not long-term depression.
J Neurosci
17:2645-2651[Abstract/Free Full Text].
-
Nakanishi S
(1989)
K-252-derivatives K252a, K252b, KT5720, KT5962, KT5823.
Seitaino-Kagaku
40:364-365.
-
O'Connor JJ,
Rowan MJ,
Anwyl R
(1995)
Tetanically induced LTP involves a similar increase in the AMPA and NMDA receptor components of the excitatory postsynaptic current: investigations of the involvement of mGlu receptors.
J Neurosci
15:2013-2020[Abstract].
-
O'Dell TJ,
Hawkins RD,
Kandel ER,
Arancio O
(1991)
Tests of the roles of two diffusible substances in long-term potentiation: evidence for nitric oxide as a possible retrograde messenger.
Proc Natl Acad Sci USA
88:11285-11289[Abstract/Free Full Text].
-
O'Dell TJ,
Huang PL,
Danwson TM,
Dinerman JL,
Snyder SH,
Kandel ER,
Fishman MC
(1994)
Endothelial NOS and the blockade of LTP by NOS inhibitors in mice lacking neuronal NOS.
Science
265:542-546[Abstract/Free Full Text].
-
O'Mara SM,
Rowan MJ,
Anwyl R
(1995)
Metabotropic glutamate receptor-induced long-term depression and depotentiation in the dentate gyrus of the rat hippocampus in vitro.
Neuropharmacology
34:983-989[Web of Science][Medline].
-
Schumann EM,
Madison DV
(1991)
A requirement for the intercellular messenger nitric oxide in long-term potentiation.
Science
254:1503-1506[Abstract/Free Full Text].
-
Schumann EM,
Madison DV
(1994)
Nitric oxide and synaptic function.
Annu Rev Neurosci
17:153-183[Web of Science][Medline].
-
Schumann EM,
Meffert MK,
Schulman H,
Madison DV
(1994)
An ADP-ribosyltransferase as a potential target for nitric oxide action in hippocampal long-term potentiation.
Proc Natl Acad Sci USA
91:11958-11962[Abstract/Free Full Text].
-
Son H,
Hawkins RD,
Martin K,
Kiebler M,
Huang PL,
Fishman MC,
Kandel ER
(1996)
Long-term potentiation is reduced in mice that are doubly mutant in endothelial and neuronal nitric oxide synthase.
Cell
87:1015-1023[Web of Science][Medline].
-
Wang Y,
Rowan MJ,
Anwyl R
(1997)
Induction of LTD is NMDAR-independent, but dependent on Ca influx via low voltage activated Ca channels and release of Ca from intracellular stores in the dentate gyrus in vitro.
J Neurophysiol
77:812-825[Abstract/Free Full Text].
-
Wu J,
Wang Y,
Rowan MJ,
Anwyl R
(1997)
Evidence for involvement of the neuronal isoform of nitric oxide synthase during induction of long-term potentiation and long-term depression in the rat dentate gyrus in vitro.
Neuroscience
78:393-398[Web of Science][Medline].
-
Zhuo M,
Small SA,
Kandel ER,
Hawkins RD
(1993)
Nitric oxide and carbon monoxide produce activity-dependent long-term synaptic enhancement in hippocampus.
Science
260:1946-1950[Abstract/Free Full Text].
-
Zhou M,
Kandel ER,
Hawkins RD
(1994a)
Nitric oxide and cGMP can produce either synaptic depression or potentiation depending on the frequency of presynaptic stimulation in the hippocampus.
NeuroReport
5:1033-1036[Web of Science][Medline].
-
Zhuo M,
Hu Y,
Schultz C,
Kandel ER,
Hawkins RD
(1994b)
Role of guanylyl cyclase and cGMP-dependent protein kinase in long-term potentiation.
Nature
368:635-639[Medline].
Copyright © 1998 Society for Neuroscience 0270-6474/98/18103589-08$05.00/0
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Abstract
Introduction
