| Abstract: | 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. |
