Behavioural evidence for cholecystokinin-dopamine D1 receptor interactions in the rat

The effects of cholecystokinin (CCK) on behavioural responses to the dopamine D1 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 chewing movements. Both responses were inhibited by CCK-8S (10-50 micrograms/kg i.p.), but the preferential CCKB receptor agonist CCK-4 (20-100 micrograms/kg i.p.) attenuated SKF 38393-induced grooming only. Suppression of SKF 38393-induced grooming and vacuous chewing movements by CCK-8S was blocked 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 on dopamine D1 receptor agonist-induced vacuous chewing movements is probably mediated by CCKA receptors, while the effect on grooming may reflect an interaction with the CCKA receptor and/or a novel CCKB receptor subtype.