ABSTRACT
We have shown that buspirone, a partial agonist of 5-hydroxytryptamine 1A [5-HT[1A]] receptors, improves motor dysfunctions induced by 6-hydroxydopamine [6-OHDA] and haloperidol in rats. The present work extends these findings by investigating the role of 5-HT[1A] receptors on catalepsy-like immobilization in rats, a model of Parkinson's disease. Catalepsy was induced by unilateral infusion of 6-OH-dopamine [8 micro g/2 micro L/rat] into the central region of the substantia nigra, compact part [SNc] and assayed by bar-test method 5, 60, 120 and 180 min after the drugs administration. The involvement of 5-HT[1A] receptors in 6-OHDA-induced catalepsy was studied through intraperitoneal [0.25, 0.5 and 1mg/Kg IP] and intrasubstantia nigra, compact part [10 micro g/rat, intra-SNc] injection of 8-hydroxy-2-[di-n-propylamino] tetralin [8-OHDPAT] as well as administration of 1-[2-methoxyphenyl]-4-[4-[2-pthalimmido] butyl] piperazine hydrobromide [0.1, 0.5 and 1 mg/Kg, NAN-190, IP]. NAN-190 [1 mg/Kg, IP] and 8-OHDPAT [1 mg/Kg, IP and 10 micro g/rat, intra-SNc] increased and decreased 6-OHDA-induced catalepsy respectively. In normal [non 6-OHDA-lesioned] rats, NAN-190 [1 mg/Kg, IP] increased the elapsed time in bar-test while 8-OHDPAT did not produce any significant effect. The anticataleptic effect of 8-OHDPAT [1 mg/Kg, IP] was reversed markedly by co-injection with NAN-190 [1 mg/Kg, IP]. These findings suggest that 5-HT1A receptors are involved in 6-OHDA-induced catalepsy-like immobilization