LATE ONSET AND LONG-LASTING SUPPRESSIVE EFFECTS OF CERULETIDE, AN ANALOG OF CHOLECYSTOKININ, ON C-FOS MESSENGER-RNA EXPRESSION IN THE RAT STRIATUM

C-fos mRNA expression by stimulation with subcutaneous (s.c.) administration of saline or cycloheximide (CHX) was examined in the rat striatum with or without pretreatment with ceruletide, an analogue of cholecystokinin. The c-fos mRNA induction 1 h after CHX stimulation (25 mg/kg, s.c.) was significantly suppressed by ceruletide pretreatment (80-mu-g/kg, s.c.) 2 h before CHX stimulation in the striatum, and tended to be suppressed by ceruletide pretreatment 4 h before saline or CHX stimulation. Long-lasting and inhibitory effects of ceruletide on dyskinesia and on dopaminergic (DAergic) neuronal systems, and c-fos mRNA expression by activation of the DAergic system have been reported. The present findings together with previous reports suggest that ceruletide might have late onset and long-lasting suppressive effects on the expression of c-fos mRNA in the striatum and that these effects might be related to its effects on DAergic neuronal transmission.