Effects of Ca antagonists on the action potential and their relationship to the muscarinic ACh actions in isolated sympathetic neurons of rabbits.
Muscarinically induced depressions of the shoulder in the falling phase as well as the after-spike-hyperpolarization and -depolarization of the action potential in the isolated sympathetic neurons of rabbits were mimicked by a novel peptide Ca channel blocker, omega-conotoxin (synthetic; 0.1-0.5 microM). Cobalt ions (0.1-2 mM) showed bidirectional effects on the shoulder, an early depression followed by a later prolongation, while they consistently induced depressions of other components. Organic Ca channel blockers, verapamil and D-600 (1-50 microM) and nifedipine (0.1-1 microM) appeared to have other effects as they rather caused a prolongation of the falling phase that was shortened by further application of acetylcholine.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D003035:Cobalt / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000187:drug effects*; D008297:Male; D008978:Mollusk Venoms / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D008978:Mollusk Venoms; D011976:Receptors, Muscarinic; D005711:Gallopamil; D003035:Cobalt; D020866:omega-Conotoxin GVIA; D014700:Verapamil; D009543:Nifedipine