Department of Anesthesiology

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Distinct rat neurohypophysial nerve terminal populations identified by size, electrophysiological properties and neuropeptide content.

TitleDistinct rat neurohypophysial nerve terminal populations identified by size, electrophysiological properties and neuropeptide content.
Publication TypeJournal Article
Year of Publication2004
AuthorsOuYang W, Wang G, Hemmings HC
JournalBrain Res
Volume1024
Issue1-2
Pagination203-11
Date Published2004 Oct 22
ISSN0006-8993
KeywordsAction Potentials, Animals, Cell Size, Electrophysiology, Male, Neuropeptides, Presynaptic Terminals, Rats, Rats, Sprague-Dawley
Abstract

Voltage-gated ion channels are critical to excitation-secretion coupling in nerve terminals. We have identified two distinct populations of rat neurohypophysial (NHP) terminals distinguished by size, neuropeptide content and electrophysiological properties, including resting membrane potential, action potential (AP) properties, and K+ current and Na+ current characteristics. In large terminals (10-16 microm diameter), resting membrane potential was more negative than in small terminals (5-9.9 microm; -61+/-4 mV vs. -55+/-3 mV; p<0.01), action potential amplitude was larger (69+/-4 mV vs. 53+/-3 mV; p<0.01), peak IK was larger (1460+/-90 pA vs. 1140+/-70 pA; p<0.05) with a more negative V1/2 for activation (-3.1 mV vs. -0.6 mV; p<0.05), and Na+ current density was greater (approximately 470 pA/pF vs. approximately 300 pA/pF; p<0.01) with more negative V1/2 values for activation from -70 or -90 mV holding potentials (-44 mV vs. -24 mV; p<0.01). A positive linear correlation between INa amplitude and terminal size showed an inflection at a diameter of 9.2 microm. Neuropeptide content was generally segregated into a population of small terminals (<10 microm diameter) containing predominantly vasopressin and a population of large terminals (> or =10 microm diameter) containing predominantly oxytocin (OT); a small fraction of terminals in each group contained both peptides. These findings suggest that electrophysiological differences between small vasopressin-containing and large oxytocin-containing neurohypophysial terminals may contribute to their observed differential firing and peptide release patterns.

DOI10.1016/j.brainres.2004.07.068
Alternate JournalBrain Res.
PubMed ID15451383
Grant ListGM 58055 / GM / NIGMS NIH HHS / United States