UNSPECIFIED. (2004) Activation and integration of bilateral GABA-mediated synaptic inputs in neonatal rat sympathetic preganglionic neurones in vitro. JOURNAL OF PHYSIOLOGY-LONDON, 555 (1). pp. 189-203. ISSN 0022-3751

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Abstract

The role of GABA receptors in synaptic transmission to neonatal rat sympathetic preganglionic neurones (SPNs) was investigated utilizing whole-cell patch clamp recording techniques in longitudinal and transverse spinal cord slice preparations. In the presence of glutamate receptor antagonists (NBQX, 5 mum and D-APV, 10 mum), electrical stimulation of the ipsilateral or contralateral lateral funiculi (iLF and cLF, respectively) revealed monosynaptic inhibitory postsynaptic potentials (IPSPs) in 75% and 65% of SPNs, respectively. IPSPs were sensitive to bicuculline (10 mum) in all neurones tested and reversed polarity around -55 mV, the latter indicating mediation via chloride conductances. In three neurones IPSPs evoked by stimulation of the iLF (n = 1) or cLF (n = 2) were partly sensitive to strychnine (2 mum). The expression of postsynaptic GABA(A) and GABA(B) receptors were confirmed by the sensitivity of SPNs to agonists, GABA (2 mm), muscimol (10-100 mum) or baclofen (10-100 mum), in the presence of TTX, each of which produced membrane hyperpolarization in all SPNs tested. Muscimol-induced responses were sensitive to bicuculline (1-10 mum) and SR95531 (10 mum) and baclofen-induced responses were sensitive to 2-hydroxy-saclofen (100-200 mum) and CGP55845 (200 nm). The GABA(C) receptor agonist CACA (200 mum) was without significant effect on SPNs. These results suggest that SPNs possess postsynaptic GABA(A) and GABA(B) receptors and that subsets of SPNs receive bilateral GABAergic inputs which activate GABA(A) receptors, coupled to a chloride conductance. At resting or holding potentials close to threshold either single or bursts (10-100 Hz) of IPSPs gave rise to a rebound excitation and action potential firing at the termination of the burst. This effect was mimicked by injection of small (10-20 pA) rectangular-wave current pulses, which revealed a time-dependent, Cs+-sensitive inward rectification and rebound excitation at the termination of the response to current injection. Synaptic activation of a rebound excitation mediated by a time-dependent inward rectification expressed intrinsically by SPNs may provide a novel mechanism enabling SPNs to be entrained to rhythms driven from the brainstem or higher centres.

Item Type:	Journal Article
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry Q Science > QP Physiology
Journal or Publication Title:	JOURNAL OF PHYSIOLOGY-LONDON
Publisher:	BLACKWELL PUBLISHING LTD
ISSN:	0022-3751
Date:	15 February 2004
Volume:	555
Number:	1
Number of Pages:	15
Page Range:	pp. 189-203
Identification Number:	10.1113/jphysiol.2003.055665
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/8683

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