We investigated the effect of pentobarbital and diazepam on activities of GABA-receptor, using current clamp and voltage clamp methods. Perfusion of GABA was applied to the ganglion cells of Aplysia kurodai to induce the activities of GABA-receptor. GABAA-receptor was used in this studies. The GABA-induced Hcl-type response was suppressed by picrotoxin and bicuculine which had been antagonist of GABAA-receptor. The GABA-receptor of this type is called the GABAA-receptor. We used to do this experiment GABAA-receptor. Both pentobarbital and diazepam with the lower concentration (10-6M) enhanced Cl--dependent hyperpolarizing response to GABA. However, pentobarbital and diazepam with the concentration of above 10-5M suppressed Cl--dependent hyperpolarizing response to GABA. The mode of suppression was studied by plottings dose-inhibition curve for GABAA-type of receptor activities. The curve showed no shift in either direction with increase in GABA. These findings indicated that pentobarbital and diazepam suppressed the GABAA-receptor with noncompetitive mode.
These results suggest that neither pentobarbital nor diazepam compete with GABA for common binding site of the receptor, but it bind to a certain allosteric site, which controls the opening ionic channel, particularly for Cl-.
