Intracellular Ca2+ antagonist TMB-8 blocks catecholamine secretion evoked by caffeine and acetylcholine from perfused cat adrenal glands in the absence of extracellular Ca2+.
Unlike acetylcholine, caffeine was much more effective in releasing catecholamine in the absence of extracellular Ca2+ than in its presence in perfused cat adrenal glands. The intracellular Ca2+ antagonist, TMB-8 (10(-4) M), inhibited reversibly the catecholamine secretion evoked by caffeine (40 mM) and that induced by acetylcholine (10(-4) M) in the presence of hexamethonium (10(-3) M) during perfusion with Ca2+-free Locke solution containing EGTA (10(-5) M). These results support our view that muscarinic receptor activation causes catecholamine secretion by mobilizing Ca2+ from an intracellular pool just as caffeine does.
Department of Pharmacology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Y
Y
Yamada
H
H
Teraoka
Y
Y
Nakazato
A
A
Ohga
D000109:Acetylcholine / Q000494:pharmacology*; D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D002415:Cats; D004837:Epinephrine / Q000378:metabolism; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism
D002395:Catecholamines; D002110:Caffeine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D000109:Acetylcholine; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine