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European Neuroscience Association Pre‐ and post‐synaptic muscarinic receptors in thin slices of rat adrenal gland
Author(s) -
Barbara JeanGaël,
Lemos Virginia Soares,
Takeda Kenneth
Publication year - 1998
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1998.00349.x
Subject(s) - muscarine , muscarinic acetylcholine receptor , hyperpolarization (physics) , oxotremorine , chromaffin cell , depolarization , excitatory postsynaptic potential , chemistry , neuroscience , inhibitory postsynaptic potential , biophysics , muscarinic acetylcholine receptor m2 , charybdotoxin , endocrinology , medicine , membrane potential , adrenal medulla , receptor , biology , biochemistry , catecholamine , nuclear magnetic resonance spectroscopy , organic chemistry
The effects of activation of muscarinic receptors on chromaffin cells and splanchnic nerve terminals were studied in a rat adrenal slice preparation. In chromaffin cells, muscarine induced a transient hyperpolarization followed by a depolarization associated with cell spiking. The hyperpolarization was blocked by charybdotoxin (1 μ m ) and tetraethylammonium chloride (TEA, 1 m m ), but was not affected by 200 μ m Cd 2+ or removal of external Ca 2+ , consistent with activation of BK channels. This would follow internal Ca 2+ mobilization, as shown by Ca 2+ imaging with fura‐2 on isolated chromaffin cells in culture. Under voltage‐clamp, outward BK currents were insensitive to MT3 toxin, a specific muscarinic m4 receptor antagonist. In contrast, muscarine‐induced depolarization was due to a m4 receptor‐mediated inward current blocked by MT3 toxin. This current was permeable to cations and was associated with Ca 2+ entry and subsequently, Ca 2+ ‐induced Ca 2+ release. Finally, both muscarine (25 μ m ) and oxotremorine (10 μ m ) decreased the amplitude and frequency of KCl‐evoked excitatory postsynaptic currents, without affecting quantal size, consistent with a presynaptic inhibitory effect. Taken together, our data suggest that activation of m4 and probably m3 muscarinic receptors results in a strong, long‐lasting excitation of chromaffin cells, as well as an uncoupling of synaptic inputs onto these cells.