Evidence for the presence of D2 but not D1 dopamine receptors in rat hypothalamic perifornical area

Behavioural studies have shown that the perifornical hypothalamus (PFH) plays a fundamental role in mediating dopamine-induced anorexia. In the present report, we provide biochemical evidence for the occurrence of dopamine receptors in the PFH, but not in the paraventricular nucleus of the hypothalamus. Dopamine as well as bromocriptine, a D₂ dopamine receptor agonist, strongly reduced the adenylate cyclase activity in the PFH. This inhibitory effect was reversed by haloperidol and by (-)-sulpiride, but not by (+)-sulpiride. On the contrary, the selective D₁ dopamine agonist SKF 82526 was completely inactive in affecting adenylate cyclase activity. Our conclusion asserts the existence of dopamine D₂ but not D₁ receptors in the PFH, which therefore can be conceived as the only region in the brain where a single class of dopamine receptors is present.