Action of calcium ions on acetylcholine-sensitive channels in Aplysia neurones

1. This work deals with the effects of external divalent ions on the values of the mean open time, tau, and of the elementary current, iel, of channels activated by acetylcholine in Aplysia neurones. The action of Ca is mainly considered. 2. Ca ions were found to prolong tau and decrease iel under various experimental conditions. In isotonic Ca solution, tau is 12 times larger than in isotonic Na solution (divalent free sea water). On the other hand, iel is about 8 times smaller in the first solution than in the second. 3. A quantitative analysis of these effects is presented.