title: A study of the cholinolytic actions of strychnine using the technique of concentration jump relaxation analysis.
abstract: The blocking actions of strychnine on excitatory acetylcholine (ACh) responses in isolated, voltage clamped Aplysia neuronal cell bodies has been studied using a rapid drug application technique. Rapid microperfusion of strychnine (10-50 microM) produced a reduction of the steady-state ACh-induced inward current in Aplysia neurons which decayed exponentially with a highly dose-dependent time constant. At the cessation of strychnine perfusion the ACh-induced current recovered to its original value with an exponential time course which was not sensitive to the dose of strychnine previously applied. The calculated association (k1) and dissociation (k-1) constants for a pseudo-first-order reaction between strychnine and its binding site were k1 = 1.2 X 10(4) M-1. sec-1 and k-1 = 0.12 sec-1 (KD = 1 X 10(-5) M-1). These results demonstrate that concentration jump relaxation experiments can be performed on isolated neurons for the study of voltage-independent antagonists by the use of rapid microperfusion systems and provide the first direct estimates to date of the rate constants of the cholinolytic effect of strychnine.
mesh_terms: D000818:Animals; D001048:Aplysia; D005724:Ganglia / Q000187:drug effects*; D066298:In Vitro Techniques; D007700:Kinetics; D010276:Parasympatholytics / Q000494:pharmacology*; D013331:Strychnine / Q000494:pharmacology*
chemical_list: D010276:Parasympatholytics; D013331:Strychnine