[3H]acetylcholine release and the change in cytosolic free calcium level induced by high K+ and ouabain in rat brain synaptosomes.
High K+ (50 mM) increased both [3H]acetylcholine ([3H]ACh) release and cytosolic free calcium level ([Ca2+]i) in rat brain synaptosomes in the presence of extracellular Ca2+. Ouabain (5 x 10(-8) to 5 x 10(-4) M) also caused a dose-dependent increase in [3H]ACh release, but not in [Ca2+]i, in the absence of Ca2+. The effects of high K+ and ouabain on [3H]ACh and/or [Ca2+]i, were inhibited by the intracellular Ca2+ antagonist TMB-8 (10(-4) M). These results suggest that unlike high K+, ouabain increases transmitter release from nerve endings through a mechanism which is independent of [Ca2+]i, but sensitive to TMB-8.
Satoh
E
E
Department of Veterinary Pharmacology, Obihiro University of Agriculture and Veterinary Medicine, Japan.
Nakazato
Y
Y
D000109:Acetylcholine / Q000493:pharmacokinetics*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D010042:Ouabain; D005707:Gallic Acid; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium