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RELEASE OF NOREPINEPHRINE FROM NEURONS IN DISSOCIATED CELL CULTURES OF CHICK SYMPATHETIC GANGLIA VIA STIMULATION OF NICOTINIC AND MUSCARINIC ACETYLCHOLINE RECEPTORS
Author(s) -
Greene Lloyd A.,
Rein Glen
Publication year - 1978
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1978.tb07811.x
Subject(s) - muscarinic acetylcholine receptor , nicotinic agonist , endocrinology , medicine , acetylcholine , stimulation , cholinergic , chemistry , muscarinic agonist , muscarinic antagonist , muscarinic acetylcholine receptor m4 , muscarine , receptor , biology , carbachol
— Dissociated cell cultures of chick embryo sympathetic ganglia were incubated with [ 3 H]nor‐epinephrine ([ 3 H]NE) which was taken up and stored in reserpine‐sensitive sites. Exposure of the cultures to cholinergic agonists for 5 min intervals resulted in the releaseof a significant proportion (2–20%) of the intracellular stores of [ 3 H]NE. Studies with specific cholinergic agonists and antagonists indicated that release of [ 3 H]NE could be evoked by stimulation of either nicotinic or muscarinic receptors. Release evoked by both nicotinic and muscarinic agonists was totally blocked in the presence of 3 μM‐tetrodotoxin. thus indicating that release was mediated via active electrical responses. Release by both types of agonists was also blocked in the presence of elevated Mg 2+ or when free Ca 2+ was removed from the extracellular medium. These findings are consistent with the presence of a stimulus‐secretion coupling mechanism. Release evoked by nicotine was optimal in the presence of 1.2 mM‐Ca 2+ , whereas release evoked by the muscarinic agonist methacholine increased by about 2‐fold when the Ca 2+ concentration was decreased from 1.2 to 0.3 mM. The latter observation may be due to a lowered threshold for evocation of active responses at low concentrations of Ca 2+ . Finally, no evidence was observed for interaction between the two types of receptors. These findings (a)indicate that cultured chick sympathetic neurons possess functional nicotinic and muscarinic cholinergic receptors as well as the ability to release NE via a stimulus‐secretion coupling mechanism; (b) suggest that such cultures may be particularly useful for studying the molecular events which link stimulation of cholinergic receptors to neurotransmitter release; and (c) provide further evidence that muscarinic receptors may play aphysiological role in ganglionic transmission.