The authors tested direct effect of selected ergot alkaloids (lisuride, terguride, DH-ergotoxine, DH-ergotamine and DH-ergocristine) on specific 3H-naloxone binding in the rat striatum and hippocampus. In the striatum they found that DH-ergotoxine (a substance with high affinity for noradrenergic receptors) inhibited specific 3H-naloxone binding much more strongly than lisuride and terguride (substances with a greater affinity for dopaminergic and serotoninergic receptors). DH-ergotoxine, which inhibited binding significantly more in the striatum than in the hippocampus, displayed the greatest activity. The results show differences in the degree of inhibition by the various groups of ergot alkaloids in the striatum. In the case of DH-ergotoxine there was also a difference in the degree of inhibition in the striatum and the hippocampus.