Additive effect of 5-hydroxytryptophan and p-chloro-phenylalanine in preventing audiogenic seizures in inbred mice.

Convulsive responsiveness of O'Grady mice, inbred for susceptibility to audiogenic seizures, was decreased following treatment with the serotonin precursor, 5-hydroxytryptophan, or serotonin depletor, p-chlorophenylalanine. Neither agent exerted any antagonistic or synergistic action on the effect of the other. Upon sequential administration, their effects were additive. There was no indication that the increase in brain serotonin due to administration of its direct precursor interfered with the protective effect of p-chlorophenylalanine against seizures. Neither was there evidence that p-chlorophenylalanine-induced interruption of biosynthesis which led to severe depletion of brain serotonin affected the protective action of 5-hydroxytryptophan.