Muscarinic and nicotinic ACh receptor activation differentially mobilize Ca2+ in rat intracardiac ganglion neurons.

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Journal of neurophysiology, ISSN: 0022-3077, Vol: 90, Issue: 3, Page: 1956-64

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Beker, Friederike; Weber, Martin; Fink, Rainer H A; Adams, David J
American Physiological Society
Neuroscience; Biochemistry, Genetics and Molecular Biology; Medicine and Health Sciences
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The origin of intracellular Ca2+ concentration ([Ca2+]i) transients stimulated by nicotinic (nAChR) and muscarinic (mAChR) receptor activation was investigated in fura-2-loaded neonatal rat intracardiac neurons. ACh evoked [Ca2+]i increases that were reduced to approximately 60% of control in the presence of either atropine (1 microM) or mecamylamine (3 microM) and to <20% in the presence of both antagonists. Removal of external Ca2+ reduced ACh-induced responses to 58% of control, which was unchanged in the presence of mecamylamine but reduced to 5% of control by atropine. The nAChR-induced [Ca2+]i response was reduced to 50% by 10 microM ryanodine, whereas the mAChR-induced response was unaffected by ryanodine, suggesting that Ca2+ release from ryanodine-sensitive Ca2+ stores may only contribute to the nAChR-induced [Ca2+]i responses. Perforated-patch whole cell recording at -60 mV shows that the rise in [Ca2+]i is concomitant with slow outward currents on mAChR activation and with rapid inward currents after nAChR activation. In conclusion, different signaling pathways mediate the rise in [Ca2+]i and membrane currents evoked by ACh binding to nicotinic and muscarinic receptors in rat intracardiac neurons.