Evidence against serotonin involvement in the tonic component of electrically induced convulsions and in carbamazepine anticonvulsant activity.

Intraventricular injection of 5,7-dihydroxytryptamine, selective destruction of descending serotoninergic neurons by 5,6-dihydroxytryptamine or electrolytic and chemical lesions of the nucleus raphe dorsalis did not affect the electroconvulsive threshold in rats. No effect was observed after the systemic administration of drugs known to increase central serotonin transmission, such as quipazine, m-chlorophenylpiperazine, and moderate doses of d-fenfluramine, whereas p-chlorophenylalanine, an inhibitor of serotonin synthesis, decreased seizure susceptibility. The anticonvulsant activity of carbamazepine was not modified in animals with the same experimental lesions. The results, in relation to the high selectivity of the experimental procedures employed to deplete brain and spinal cord serotonin, do not bear out any involvement of serotonin in the tonic component of electrically induced convulsions or in the action of carbamazepine.