EFFECTS OF RITANSERIN ON HALOPERIDOL-INDUCED DOPAMINE (D-2) RECEPTOR UP-REGULATION IN THE RAT

Rats were treated with vehicle, ritanserin (5 mg/kg, i.p.), haloperido l (1 mg/kg, i.p.) or both ritanserin and haloperidol for 19 days to de termine whether chronic administration of the serotonin (5HT(2)) antag onist ritanserin affects D-2 receptor up-regulation produced by halope ridol. Brain sections were prepared for D-2 and 5HT(2) receptor autora diography with [H-3]spiperone and [H-3]ketanserin, respectively, Ritan serin significantly reduced 5HT(2) receptors to 80% of vehicle in the sulcal area of the frontal cortex but had no effect on D-2 receptors. Haloperidol significantly increased striatal and n. accumbens D-2 rece ptors with no effect on 5HT(2) receptors. In ritanserin/haloperidol-tr eated rats, D-2 receptors were significantly increased along with sign ificant decreases in 5HT(2) receptors of the frontal cortex. These res ults suggest 5HT(2) receptor antagonism by ritanserin does not signifi cantly affect D-2 receptor up-regulation produced by haloperidol. (C) 1997 Elsevier Science Ireland Ltd.