The effect of orexin-A on motor and cognitive functions in a rat model of Parkinson's disease

Objective:The aim of this study was to evaluate the effect of orexin-A (OX-A) and the orexin-1 receptor antagonist SB-334867 (SB) on motor and cognitive functions in a rat model of Parkinson's disease. Methods: Parkinson was induced by intracerebroventricular (i.c.v) injection of 6-hydroxydopamine (6-OHDA) (200 g/rat). 72h later, the treatment was initiated by i.c.v administration of SB (30 nmol/rat) and/or OX-A (0.3 nmol/rat) for 10 days. Motor functions were monitored using rotarod and hanging tests. Cognitive function was assessed by passive avoidance test (Shuttle box). Results: OX-A administration in 6-OHDA treated rats remarkably increased the time which animals run on rod (in rotarod test) and also the latency to fall (in hanging test) (P < 0.01 and P < 0.001, respectively). Conversely, administration of SB in 6-OHDA-treated rats decreased the mentioned indices (P < 0.05 for latency to fall). Administration of agonist and/or antagonist of orexin-1 receptors had no significant effect on 6-OHDA induced cognitive impairment in rats. Conclusion:Results of this study suggest that the orexinergic system might be involved in sensory-motor deficits of Parkinson's disease.