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Active and passive membrane properties of rat sympathetic preganglionic neurones innervating the adrenal medulla
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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. doi:10.1113/jphysiol.2002.023390
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Official URL: http://dx.doi.org/10.1113/jphysiol.2002.023390
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 |
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| Journal or Publication Title: | JOURNAL OF PHYSIOLOGY-LONDON | ||||
| Publisher: | CAMBRIDGE UNIV PRESS | ||||
| ISSN: | 0022-3751 | ||||
| Official Date: | 15 December 2002 | ||||
| Dates: |
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| Volume: | 545 | ||||
| Number: | 3 | ||||
| Number of Pages: | 16 | ||||
| Page Range: | pp. 945-960 | ||||
| DOI: | 10.1113/jphysiol.2002.023390 | ||||
| Publication Status: | Published |
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