Buspirone improves 6-hydroxydopamine-induced catalepsy through stimulation of nigral 5-HT1A receptors in rats

Receptors for 5-HT1A are widely distributed throughout the basal ganglia, and their activation results in an inhibition of dopamine (DA) release. This study aimed to investigate the effect of buspirone, as a partial agonist of 5-HT1A receptors, on 6-hydroxydopamine (6-OHDA)-induced catalepsy in male Wistar rats. Catalepsy was induced by unilateral infusion of 6-OH-DA (6 μg/2 μl/rat) into the central region of the substantia nigra pars compacta (SNc) and assayed by the bar-test method 60,120 and 180 min after drug administration. The results demonstrated that intraperitoneal (ip) injection of buspirone at doses of 5,7.5 and 10 mg/kg decreased catalepsy compared with the control group. In addition, intra-SNc injection of 8-hydroxy-2-[di-n-propylamino]tetralin (8-OH-DPAT; 10 μg/rat), a 5-HT1A receptor agonist, decreased 6-OHDA-induced catalepsy. The effects of buspirone (7.5 mg/kg, ip) and 8-OH-DPAT (10 μg/rat, intra-SNc) were abolished by 1-(2-methoxyphenyl)-4-[4-(2-phthalimido) butyl]piperazine hydro-bromide (NAN-190; 10 μg/rat, intra-SNc), a 5-HT1A receptor antagonist. Our study indicates that buspirone improves catalepsy in a 6-OHDA-induced animal model of Parkinson's disease through activation of nigral 5-HT1A preceptors. However, further investigations should be undertaken to clarify the exact mechanism of interaction between 5-HT1A and DA receptors.