Age- and gender-related differences in GABAA receptor-mediated postsynaptic currents in GABAergic neurons of the substantia nigra reticulata in the rat

doi:10.1016/j.neuroscience.2009.06.025

Neuroscience

Volume 163, Issue 1, 29 September 2009, Pages 155-167

https://doi.org/10.1016/j.neuroscience.2009.06.025 Get rights and content

Abstract

The responsiveness of the rat anterior substantia nigra pars reticulata (SNR) GABAergic neurons to GABA_Aergic drugs changes with age and gender, altering its role in seizure control. To determine whether maturational and gender-specific differences in the properties of spontaneous GABA_ARs-mediated inhibitory postsynaptic currents (sIPSCs) underlie these events, we studied sIPSCs at baseline and after application of the α1 GABA_ARs subunit selective agonist zolpidem, at postnatal days (PN) 5–9, PN12–15, and PN28–32. Results were correlated with the α1 and α3 GABA_ARs subunit immunoreactivity (-ir) at PN5, PN15, and PN30, using immunochemistry. The mean frequency, amplitude and charge transfer increased whereas the 10–90% rise time and decay time accelerated with age in both genders. The faster sIPSC kinetics in older rats were paralleled by increased α1-ir and decreased α3-ir. At PN5–9, males had more robust sIPSCs (frequency, amplitude, charge carried per event and charge transfer) than females. At PN28–32, males exhibited higher amplitudes and faster kinetics than females. The zolpidem-induced increase of decay times, amplitude and charge transfer and α1-ir expression were the lowest in PN5–9 males but increased with age, in both genders. Our findings demonstrate that alterations in GABA_ARs subunit expression partially underlie age- and gender-specific sIPSC changes in SNR neurons. However, the observation of gender differences in sIPSC kinetics that cannot be attributed to changes in perisomatic α1 expression suggests the existence of additional gender-specific factors that control the sIPSC kinetics in rat SNR.

Section snippets

Experimental procedures

We used Sprague–Dawley rats of both genders divided into three different age groups PN5–9, PN12–15 and PN28–32, with the date of birth taken as PN0 (Taconic Farms, Inc., Hudson, NY, USA). Rats were kept at constant temperature (21–23 °C), relative humidity (40–60%) and a 12-h light/dark cycle (lights on at 7:00 am) with food and water ad libitum in our animal facility accredited by the American Association for the Accreditation of Laboratory Animal Care. Rats younger than 21 days were kept with

Baseline sIPSCs

Spontaneous IPSCs were recorded in the presence of CNQX 10 μM and d-AP5 50 μM. Under these conditions all sIPSCs were blocked by BIM, which confirms that they were GABA_ARs-mediated (Fig. 1A–C). The sIPSCs could be detected at all studied ages in both genders. The events reversed close to 0 mV, the theoretical equilibrium potential for Cl⁻ ions (Fig. 2A, B). All numeric values are summarized in Table 1.

The results of the two-way ANOVA for the studied sIPSC parameters and inter-group comparisons

Discussion

The current study describes age- and gender-related differences in the properties of sIPSCs in GABAergic neurons of the anterior SNR, a region that undergoes developmental changes in terms of its ability to modify seizure thresholds (Veliskova and Moshe, 2001). Our data show that the mean frequency, amplitude and charge transfer increase and 10–90% rise time and decay time accelerate in both genders with age. The developmental increase in GABA_ARs α1-ir and parallel decrease in GABA_ARs α3-ir may

Acknowledgments

The authors thank Drs. Jana Veliskova, Libor Velisek and James G. Heida for thoughtful comments and critiques. We would like to acknowledge the excellent technical assistance of Mrs. Qianyun Li. This project was supported by NIH NINDS grants NS20253, NS045243, NS58303, NS62947, and grants from the International Rett Syndrome Foundation, PACE, and Heffer Family Foundation. S.L.M. is a recipient of a Martin A. and Emily L. Fisher Fellowship in Neurology and Pediatrics.

References (54)

J.P. Andrade et al.
Sexual dimorphism in the subiculum of the rat hippocampal formation
Brain Res
(2000)
A.A. Caminero et al.
Sexual dimorphism in accessory olfactory bulb mitral cells: a quantitative Golgi study
Neuroscience
(1991)
C. Deransart et al.
The role of basal ganglia in the control of generalized absence seizures
Epilepsy Res
(1998)
M. Frerking et al.
Variation in GABA mini amplitude is the consequence of variation in transmitter concentration
Neuron
(1995)
A.M. Hosie et al.
Conserved site for neurosteroid modulation of GABA A receptors
Neuropharmacology
(2009)
A.M. Lavoie et al.
Activation and deactivation rates of recombinant GABA(A) receptor channels are dependent on alpha-subunit isoform
Biophys J
(1997)
J.A. Markham et al.
Aging and sex influence the anatomy of the rat anterior cingulate cortex
Neurobiol Aging
(2002)
S.L. Moshe et al.
Nigral muscimol infusions facilitate the development of seizures in immature rats
Brain Res
(1984)
S.L. Moshe et al.
Maturation and segregation of brain networks that modify seizures
Brain Res
(1994)
T. Ravizza et al.
Sex differences in GABA(A)ergic system in rat substantia nigra pars reticulata
Int J Dev Neurosci
(2003)

C.D. Richards et al.

Electrophysiological and immunocytochemical characterization of GABA and dopamine neurons in the substantia nigra of the rat

Neuroscience

(1997)

H. Shen et al.

Short-term steroid treatment increases delta GABAA receptor subunit expression in rat CA1 hippocampus: pharmacological and behavioral effects

Neuropharmacology

(2005)

Y. Smith et al.

Neurons of the substantia nigra reticulata receive a dense GABA-containing input from the globus pallidus in the rat

Brain Res

(1989)

Y. Smith et al.

Convergence of synaptic inputs from the striatum and the globus pallidus onto identified nigrocollicular cells in the rat: a double anterograde labelling study

Neuroscience

(1991)

S. Ueno et al.

Sites of positive allosteric modulation by neurosteroids on ionotropic gamma-aminobutyric acid receptor subunits

FEBS Lett

(2004)

J.N. Wurpel et al.

Age-related changes of muscimol binding in the substantia nigra

Brain Res

(1988)

E.A. Barnard et al.

International Union of PharmacologyXV. Subtypes of gamma-aminobutyric acidA receptors: classification on the basis of subunit structure and receptor function

Pharmacol Rev

(1998)

E.E. Benarroch

GABAA receptor heterogeneity, function, and implications for epilepsy

Neurology

(2007)

J.P. Bolam et al.

Synaptic organisation of the basal ganglia

J Anat

(2000)

S.G. Brickley et al.

Development of a tonic form of synaptic inhibition in rat cerebellar granule cells resulting from persistent activation of GABAA receptors

J Physiol

(1996)

D.D. Dunning et al.

GABA(A) receptor-mediated miniature postsynaptic currents and alpha-subunit expression in developing cortical neurons

J Neurophysiol

(1999)

J.M. Fritschy et al.

Switch in the expression of rat GABAA-receptor subtypes during postnatal development: an immunohistochemical study

J Neurosci

(1994)

A.S. Galanopoulou

Sex- and cell-type-specific patterns of GABAA receptor and estradiol-mediated signaling in the immature rat substantia nigra

Eur J Neurosci

(2006)

A.S. Galanopoulou

Dissociated gender-specific effects of recurrent seizures on GABA signaling in CA1 pyramidal neurons: role of GABA(A) receptors

J Neurosci

(2008)

K. Gale

Mechanisms of seizure control mediated by gamma-aminobutyric acid: role of the substantia nigra

Fed Proc

(1985)

K.J. Gingrich et al.

Dependence of the GABAA receptor gating kinetics on the alpha-subunit isoform: implications for structure-function relations and synaptic transmission

J Physiol

(1995)

P.A. Goldstein et al.

Prolongation of hippocampal miniature inhibitory postsynaptic currents in mice lacking the GABA(A) receptor alpha1 subunit

J Neurophysiol

(2002)

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Cellular NeuroscienceResearch PaperAge- and gender-related differences in GABAA receptor-mediated postsynaptic currents in GABAergic neurons of the substantia nigra reticulata in the rat

Abstract

Section snippets

Experimental procedures

Baseline sIPSCs

Discussion

Acknowledgments

Brain Res

Neuroscience

Epilepsy Res

Neuron

Neuropharmacology

Biophys J

Neurobiol Aging

Brain Res

Brain Res

Int J Dev Neurosci

Neuroscience

Neuropharmacology

Brain Res

Neuroscience

FEBS Lett

Brain Res

International Union of PharmacologyXV. Subtypes of gamma-aminobutyric acidA receptors: classification on the basis of subunit structure and receptor function

Pharmacol Rev

GABAA receptor heterogeneity, function, and implications for epilepsy

Neurology

Synaptic organisation of the basal ganglia

J Anat

Development of a tonic form of synaptic inhibition in rat cerebellar granule cells resulting from persistent activation of GABAA receptors

J Physiol

GABA(A) receptor-mediated miniature postsynaptic currents and alpha-subunit expression in developing cortical neurons

J Neurophysiol

Switch in the expression of rat GABAA-receptor subtypes during postnatal development: an immunohistochemical study

J Neurosci

Sex- and cell-type-specific patterns of GABAA receptor and estradiol-mediated signaling in the immature rat substantia nigra

Eur J Neurosci

Dissociated gender-specific effects of recurrent seizures on GABA signaling in CA1 pyramidal neurons: role of GABA(A) receptors

J Neurosci

Mechanisms of seizure control mediated by gamma-aminobutyric acid: role of the substantia nigra

Fed Proc

Dependence of the GABAA receptor gating kinetics on the alpha-subunit isoform: implications for structure-function relations and synaptic transmission

J Physiol

Prolongation of hippocampal miniature inhibitory postsynaptic currents in mice lacking the GABA(A) receptor alpha1 subunit

J Neurophysiol

Cellular Neuroscience
Research Paper
Age- and gender-related differences in GABA_A receptor-mediated postsynaptic currents in GABAergic neurons of the substantia nigra reticulata in the rat