BEHAVIORAL EVIDENCE FOR CHOLECYSTOKININ-DOPAMINE D-1 RECEPTOR INTERACTIONS IN THE RAT

The effects of cholecystokinin (CCK) on behavioural responses to the d opamine D-1 receptor agonist (+/-)SKF 38393 ((+/-)-2,3,4,5-tetrahydro- 7,8-dihydroxy- 1-phenyl-1H-3-benzazepine HCl) were studied in the rat. SKF 38393 (5 mg/kg s.c.) induced stereotyped grooming and vacuous che wing movements. Both responses were inhibited by CCK-8S (10-50 mu g/kg i.p.), but the preferential CCKB receptor agonist CCK-4 (20-100 mu g/ kg i.p.) attenuated SKF 38393-induced grooming only. Suppression of SK F 38393-induced grooming and vacuous chewing movements by CCK-8S was b locked by the selective CCKA receptor antagonist MK-329 (also known as devazepide or L-364,718) (0.1, 0.3 mg/kg i.p.) but unaffected by the CCKB receptor antagonist L-365,260 (0.1, 0.3 mg/kg i.p.). We conclude that CCK can modify dopamine-mediated behavioural responses, possibly reflecting an action post-synaptic to dopamine terminals. The effect o n dopamine D-1 receptor agonist-induced vacuous chewing movements is p robably mediated by CCKA receptors, while the effect on grooming may r eflect an interaction with the CCKA receptor and/or a novel CCKB recep tor subtype.