Selective effects of enzyme treatment used for dissociating single cells on their GABA-receptor activities

Abstract

Frog dorsal root ganglion (DRG) cells treated with collagenase and trypsin were dissociated mechanically. The characteristics of dose-response curves of GABA-induced Cl − currents ( I Cl) were mainly studied using the “concentration-clamp” technique, by which the external solution around isolated single neurons was rapidly changed within a few milliseconds. The saturating maximum currents induced by various concentrations of GABA normalized to the peak I Cl induced by 10 −5 M GABA on the same neuron varied from 1.5 to 5.5 among the neurons, though the absolute maximum currents varied little. The Hill coefficients ( n = 1.92 ± 0.09, mean ± S.D.) also varied little on the neurons. The time constants of the desensitization phase of fully activated GABA responses were not so markedly different among the neurons. The present results suggested a possibility that the enzyme treatment produced a selective inactivation of α 1 unit, a high affinity subtype of the GABA-receptor.