Contrasting effects of a convulsant (CHEB) and an anticonvulsant barbiturate (phenobarbitone) on amino acid release from rat brain slices.

The effects of a convulsant barbiturate, 5(2-cyclohexylidine-ethyl)-5-ethyl barbituric acid (CHEB), and phenobarbitone (PhB) on the release of exogenous D-aspartate and GABA from slices of rat cerebral cortex were investigated. While PhB inhibited potassium-evoked release of D-aspartate more so than that of GABA, CHEB potently inhibited potassium-evoked GABA release and stimulated evoked D-aspartate release, in a concentration-dependent manner. These actions are consistent with the observed in vivo convulsant and anticonvulsant properties of these barbiturates. CHEB, but not PhB also elevated spontaneous efflux of both amino acids. The actions of these barbiturates were further studied in calcium- and sodium-free media, and in the presence of tetrodotoxin and ruthenium red, agents known to alter ion flux across neuronal membranes. The results obtained indicate that different ionic mechanisms may be involved in the release of excitatory and inhibitory amino acid transmitters.