Long-term suppression of central serotonergic activity by corticosteroids: a possible model of steroid-responsive myoclonic disorders.

Chronic administration of cortisol succinate (12.5 mg per kilogram per day) to guinea pigs suppressed jumping behavior induced by 1-5 hydroxytryptophan and abolished diurnal threshold variations of this behavior. Chronic corticosteroid administration did not alter threshold or diurnal variations of apomorphine-induced stereotypy. These observations suggest that the efficacy of corticosteroids in some human myoclonic movement disorders may be related to central serotonergic inhibition.