Augmentation by chlordiazepoxide of the inhibitory effects of taurine, beta-alanine and gamma-aminobutyric acid on spike discharges in guinea-pig cerebellar slices.

1. Chlordiazepoxide (Cdp, 1 to 100 micrometer) enhanced the inhibitory action of externally applied gamma-aminobutyric acid (GABA) upon spontaneous spike discharges in guinea-pig cerebellar slices; the actions of externally applied beta-alanine and taurine, but not externally applied glycine, were also enhanced by Cdp. 2. It was suggested the Cdp might exert its action by enhancing the increase of membrane permeability to K+ induced by the amino acid, but not to Cl-. 3. Cdp (5 to 100 micrometer) reversed the antagonism of picrotoxin to the inhibitory action of externally applied GABA and also the antagonism of strychnine to the actions of externally applied beta-alanine and taurine. 4. The inhibition of the spontaneous spike discharges of Purkinje cells, evoked by electrical stimulation of the slice, was also enhanced by Cdp (10 to 100 micrometer). 5. The blocking action of picrotoxin (10 to 20 micrometer) on the stimulus-evoked inhibition of spike discharges was reversed by Cdp (10 micrometer). 6. In a similar manner, strychnine (10 or 20 micrometer) was also found to block the stimulus-evoked inhibition of spike discharges. It is suggested that in the cerebellum strychnine-sensitive amino acid(s) may be involved in synaptic transmission. Strychnine blockade was also reversed by Cdp (10 micrometer).