Kinetic analysis of acetylcholine-induced XXXX current in isolated Aplysia neurones.

@entity1617 @entity2865
(1) Kinetics of activation and desensitization phases of the @entity1617 -induced @entity2865 current (ICl) were studied in isolated single neurones of Aplysia kurodai, using the 'concentration clamp' technique which combines internal perfusion and rapid exchange of the external solution within a few milliseconds (2) The dose-response curve for the peak ICl gave a dissociation constant of 6.7 X 10(-6) M and a Hill coefficient of 1.7. (3) The current-voltage relationship was linear in the voltage range examined (-70 to +30 mV). The reversal potential (EACh) was -7.1 +/- 1.8 mV (n = 14). The value was close to the calculated equilibrium potential for @entity2865 ions (ECl). (4) The activation phase of the ICl was single exponential and the desensitization proceeded double exponentially to a steady state level. The time constants of both phases decreased with increasing concentrations of @entity1617 but showed no potential dependency. The desensitizing component of the ICl was generated by activation of a single population of the receptor-channel complex. (5) The recovery from desensitization of the ICl induced by 6 X 10(-6) M @entity1617 proceeded double exponentially, with time constants of 6.5 and 43 s at a holding potential of -30 mV. (6) Noise analysis performed on the steady state of ICl induced by low concentrations of @entity1617 (3 X 10(-7) M to 3 X 10(-6) M) showed that the steady ICl was due to activation of a single population of the receptor-channel complex with a single channel conductance of 23.3 +/- 4.3 pS (n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)
