Role of 5-Hydroxytryptamine 1A Receptors in 6-Hydroxydopmaine-induced Catalepsy-like Immobilization in Rats: a Therapeutic Approach for Treating Catalepsy of Parkinson’s Disease

We have shown that buspirone, a partial agonist of 5-hydroxytryptamine 1a (5-ht1a) 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-ht1a receptors on catalepsy-like immobilization in rats, a model of parkinson’s disease. catalepsy was induced by unilateral infusion of 6-oh-dopamine (8 μg/2μl/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-ht1a receptors in 6-ohda-induced catalepsy was studied through intraperitoneal (0.25, 0.5 and 1mg/kg ip) and intrasubstantia nigra, compact part (10 μg/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 μg/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.