Suppressive action of cholecystokinin octapeptide on the behavioral effects of L-DOPA in the rat.

Intracerebroventricular (i.c.v.) administration of cholecystokinin octapeptide (CCK-8) appeared to suppress the effects of L-DOPA and antagonize the actions of thyrotropin-releasing hormone (TRH). This was not only proved by the behavioral rating, but also by locomotor activity counting. thus, the sedative action of CCK-8 and the antagonizing effect of this peptide on the central actions of TRH were clearly demonstrated.