Changes in various neurotransmitter systems of the gerbil brain during ischemia and the effects of administration of mergocryptine, a new ergot derivative, were studied. Gerbils intraperitoneally administered 0.5 mg/kg of mergocryptine or the vehicle once a day for 14 days were used. The administration of mergocryptine to control animals had no effect on the contents of neurotransmitters or their metabolites in various regions of the brain, but it corrected abnormalities in the neurotransmitter systems caused by ischemia. These results suggest the usefulness of mergocryptine against the deleterious effects of brain ischemia.