Three distinct Ca(2+) influx pathways couple acetylcholine receptor activation to catecholamine secretion from PC12 cells.
Amperometry and microfluorimetry were employed to investigate the Ca(2+)-dependence of catecholamine release induced from PC12 cells by cholinergic agonists. Nicotine-evoked exocytosis was entirely dependent on extracellular Ca(2+) but was only partly blocked by Cd(2+), a nonselective blocker of voltage-gated Ca(2+) channels. Secretion and rises of [Ca(2+)](i) observed in response to nicotine could be almost completely blocked by methyllycaconitine and alpha-bungarotoxin, indicating that such release was mediated by receptors composed of alpha7 nicotinic acetylcholine receptor subunits. Secretion and [Ca(2+)](i) rises could also be fully blocked by co-application of Cd(2+) and Zn(2+). Release evoked by muscarine was also fully dependent on extracellular Ca(2+). Muscarinic receptor activation stimulated release of Ca(2+) from a caffeine-sensitive intracellular store, and release from this store induced capacitative Ca(2+) entry that could be blocked by La(3+) and Zn(2+). This Ca(2+) entry pathway mediated all secretion evoked by muscarine. Thus, activation of acetylcholine receptors stimulated rises of [Ca(2+)](i) and exocytosis via Ca(2+) influx through voltage-gated Ca(2+) channels, alpha7 subunit-containing nicotinic acetylcholine receptors, and channels underlying capacitative Ca(2+) entry.
Taylor
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Institute for Cardiovascular Research, University of Leeds, Leeds, England.
Peers
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D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003592:Cytophotometry; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis / Q000187:drug effects; D016257:Fura-2; D007811:Lanthanum / Q000494:pharmacology; D008839:Microelectrodes; D009116:Muscarine / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D016716:PC12 Cells; D051381:Rats; D011976:Receptors, Muscarinic / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002395:Catecholamines; D000697:Central Nervous System Stimulants; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; D002110:Caffeine; D007811:Lanthanum; D009538:Nicotine; D009116:Muscarine; D015032:Zinc; D002118:Calcium; D016257:Fura-2