Active and passive membrane properties of rat sympathetic preganglionic neurones innervating the adrenal medulla
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 0022-3751Full text not available from this repository.
Official URL: http://dx.doi.org/10.1113/jphysiol.2002.023390
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|
|Date:||15 December 2002|
|Number of Pages:||16|
|Page Range:||pp. 945-960|
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