Muscarinic cholinergic enhancement of inositide turnover in cerebral nerve endings is not mediated by calcium uptake.
Muscarinic cholinergic stimulation of rat cerebral nerve endings incubated with 32Pi causes an enhancement of the labeling of phosphatidic acid (PA) and phosphatidylinositol (PI). The involvement of Ca2+ in the stimulation of PA and PI labeling by carbamylcholine (CCh) was investigated. Enhancement of Ca2+-influx with veratridine and the Ca2+-ionophore A23187 caused a vast decrease of the labeling of the polyphosphoinositides, which was not accompanied by an enhancement of the labeling of PA and PI. The dihydropyridine Ca2+-agonist BAY K8644 did not affect phospholipid labeling. A23187, veratridine and BAY K 8644 did not enhance stimulation of the labeling of PA and PI by CCh. When Ca2+ was omitted from the incubation, A23187 caused an enhancement of basal and CCh-stimulated labeling of PA and PI, possibly indicating a particular feature of A23187 unrelated to its iontophoretic properties. The Ca2+-channel antagonists nimodipine, verapamil and flunarizine were virtually without effect on basal and CCh-stimulated labeling of PI and PA. These data support the notion that the muscarinic cholinergic inositide response is not mediated or controlled by Ca2+-flux.
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D001921:Brain / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002936:Cinnarizine / Q000031:analogs & derivatives / Q000494:pharmacology; D005444:Flunarizine; D008297:Male; D009411:Nerve Endings / Q000378:metabolism*; D009539:Nicotinic Acids / Q000494:pharmacology; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D009553:Nimodipine; D010712:Phosphatidic Acids / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014700:Verapamil / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D009539:Nicotinic Acids; D010712:Phosphatidic Acids; D010716:Phosphatidylinositols; D000001:Calcimycin; D002936:Cinnarizine; D009553:Nimodipine; D014701:Veratridine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002217:Carbachol; D014700:Verapamil; D009543:Nifedipine; D005444:Flunarizine; D002118:Calcium