EVIDENCE FOR SPECIFIC INTERACTIONS BETWEEN 5-HT1A AND DOPAMINE D-2 RECEPTOR MECHANISMS IN THE MEDIATION OF EXTRAPYRAMIDAL MOTOR FUNCTIONS IN THE RAT

Administration of the 5-HxT(1A) receptor agonist 8-hydroxy-2-(di-n-pro pylamino)tetralin (8-OH-DPAT; 0.1 mg kg(-1) SC) completely antagonised the catalepsy produced by the dopamine (DA) D-2 receptor antagonist r aclopride (16 mg kg(-1) SC). This effect by 8-OH-DPAT was in turn comp letely antagonised by treatment with the new 5-HT1A receptor antagonis t S)-5-fluoro-8-hydroxy-2-(di-n-propylamino)tetralin [(S)-UH-301] (3.5 mg kg(-1) SC), but not by the mixed 5-HT1 receptor/beta-adrenoceptor antagonist (-)pindolol(2.0 mg kg(-1) SC). The failure by(-)pindolol to antagonise the effects of 8-OH-DPAT on raclopride-induced catalepsy c ould be due to its beta-receptor-blocking properties, since by themsel ves both (-)pindolol and the selective beta-adrenoceptor antagonist be taxolol (4 mg kg(-1) SC) at least partially antagonised the raclopride -induced catalepsy. The present results provide further support for sp ecific interactions between 5-HT1A and DA D-2 receptor mechanisms in t he mediation of extrapyramidal motor functions in the rat.