The dopamine receptor antagonist SCH 23390 attenuates feeding induced by Delta9-tetrahydrocannabinol.

A large body of evidence supports the notion that Delta9-tetrahydrocannabinol (THC) stimulates food intake by its actions on CB1 cannabinoid receptors. Indirect evidence also suggests a role for dopamine (DA) receptors in mediating THC-induced feeding. In the present study, a series of experiments involving intraperitoneal drug administration in rats were conducted to further investigate the interaction between cannabinoid and dopamine receptors in feeding behaviour. Male Wistar rats were habituated to the test environment and injection procedure, and then were injected with vehicle alone, the dopamine D1-like receptor antagonist SCH 23390 (0.005, 0.01, 0.5 or 0.1 mg/kg), THC (0.1, 0.5 or 1.0 mg/kg) or SCH 23390 and THC combined. Food intake and locomotor activity were then measured for 120 min. Results revealed that administration of SCH 23390 dose-dependently decreased food intake while THC dose-dependently increased feeding. Furthermore, SCH 23390 attenuated feeding induced by THC at a dose that did not affect feeding on its own. These findings provide direct evidence for the existence of cannabinoid-dopamine interactions in feeding behaviour and suggest that dopamine D1 signalling is necessary for cannabinoids to stimulate food intake.