Piperidine discriminates between the transient and the persistent components of the ACh-induced chloride current in Aplysia neurons.

ACh-induced Cl- -current (ICl) is well known to desensitize with two components: an initial fast phase followed by a second, more slowly developing phase. In the present study, the influence of piperidine, a normal constituent in vertebrates and invertebrates, on ACh-induced ICl in isolated neurons of Aplysia was investigated by using the concentration clamp in combination with the voltage clamp technique. Pretreatment with piperidine in doses greater than 2 X 10(-4)M depressed the transient ACh-induced ICl but had little effect on the persistent ICl. Kinetic study of the desensitization phase of ACh-induced ICl showed that the slow time constant of the desensitization phase of ACh-induced ICl was not altered by pretreatment with piperidine. The present results indicate that piperidine can discriminate between the fast transient and slow persistent components of ACh-induced ICl in Aplysia neurons, and also suggest that two components of the desensitization phase of ACh-induced ICl function in an independent manner.