Attenuation of haloperidol-induced catalepsy by a 5-HT2C receptor antagonist

Atypical neuroleptics produce fewer extrapyramidal side-effects (EPS) than typical neuroleptics. The pharmacological profile of atypical neuroleptics is that they have equivalent or higher antagonist affinity for 5-HT2 than f or dopamine D-2 receptors, Our aim was to identify which 5-HT2 receptor con tributed to the atypical profile. Catalepsy was defined as rats remaining i mmobile over a horizontal metal bar for at least 30 st 90 min after dosing, Radioligand binding assays were carried out with homogenates of human reco mbinant 5-HT2A, 5-HT2B and 5-HT2C receptors expressed in Human Embryo Kidne y (HEK293) cells. Haloperidol (1.13 mg kg(-1) i.p.) induced catalepsy in al l experiments, The selective 5-HT2C 2B receptor antagonist, SB-228357 (0.32 -10 mg kg(-1) p.o.) significantly reversed haloperidol-induced catalepsy wh ereas the 5-HT2A and 5-HT2B receptor antagonists. MDL-100907 (0.003-0.1 mg kg(-1) p.o.) and SB-215505 (0.1-3.2 mg kg(-1) p.o.) respectively did not re verse haloperidol-induced catalepsy. The data suggest a role for 5-HT2C rec eptors in the anticataleptic action of SB-228357.