UNSPECIFIED. (2002) Active and passive membrane properties of rat sympathetic preganglionic neurones innervating the adrenal medulla. JOURNAL OF PHYSIOLOGY-LONDON, 545 (3). pp. 945-960. ISSN 0022-3751

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Abstract

The intravascular release of adrenal catecholamines is a fundamental homeostatic process mediated via thoracolumbar spinal sympathetic preganglionic neurones (AD-SPN). To understand mechanisms regulating their excitability, whole-cell patch-clamp recordings were obtained from 54 retrogradely labelled neonatal rat AD-SPN. Passive membrane properties included a mean resting membrane potential, input resistance and time constant of -62 +/- 6 mV, 410 +/- 241 MOmega and 104 53 ms, respectively. AD-SPN were homogeneous with respect to their active membrane properties. These active conductances included transient outward rectification, observed as a delayed return to rest at the offset of the membrane response to hyperpolarising current pulses, with two components: a fast 4-AP-sensitive component (A-type conductance), contributing to the after-hyperpolarisation (AHP) and spike repolarisation; a slower prolonged Ba2+-sensitive component (D-like conductance). All AD-SPN expressed a Ba2+-sensitive instantaneous inwardly rectifying conductance activated at membrane potentials more negative than around -80 mV. A potassium-mediated, voltage-dependent sustained outward rectification activated at membrane potentials between -35 and -15 mV featured an atypical pharmacology with a component blocked by quinine, reduced by low extracellular pH and arachidonic acid, but lacking sensitivity to Ba2+, TEA and intracellular Cs+. This quinine-sensitive outward rectification contributes to spike repolarisation. Following block of potassium conductances by Cs+ loading, AD-SPN revealed the capability for autorhythmicity and burst firing, mediated by a T-type Ca2+ conductance. These data suggest the output capability is dynamic and diverse, and that the range of intrinsic membrane conductances expressed endow AD-SPN with the ability to generate differential and complex patterns of activity. The diversity of intrinsic membrane properties expressed by AD-SPN may be key determinants of neurotransmitter release from SPN innervating the adrenal medulla. However, factors other than active membrane conductances of AD-SPN must ultimately regulate the differential ratio of noradrenaline (NA) versus adrenaline (A) release secreted in response to various physiological and environmental demands.

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:	CAMBRIDGE UNIV PRESS
ISSN:	0022-3751
Date:	15 December 2002
Volume:	545
Number:	3
Number of Pages:	16
Page Range:	pp. 945-960
Identification Number:	10.1113/jphysiol.2002.023390
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/10177

Data sourced from Thomson Reuters' Web of Knowledge

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