Trifluoperazine and calcium antagonists accelerate cholinergic desensitization in Aplysia neurons.

The onset of desensitization of excitatory acetylcholine responses in isolated, voltage clamped Aplysia RB neurons to microperfused agonist was accelerated by trifluoperazine and the calcium antagonists SKF-525A and D-600. In the absence of these drugs the time course of desensitization is described as the sum of two exponentials plus a constant. All 3 compounds accelerated the fast exponential component of desensitization, but had opposite effects on the slow component: trifluoperazine and SKF-525A accelerated the slow component, whereas this phase was greatly slowed by D-600. These results provide further evidence that the two components of cholinergic desensitization may be independent and influenced by agents which may affect calcium binding to the acetylcholine receptor.