The orexinergic system supposedly plays a role in stress circuits for arousing behaviors during anxiety, suggesting that it may play a role also in neural circuits mediating the compulsive behavior characteristic of obsessive-compulsive disorder (OCD). This study aims to investigate the roles of the orexinergic system in the development of OCD behaviors, using as preparation the induction of compulsive checking by chronic treatment with the D2/D3 agonist, quinpirole. Repeated injections of quinpirole (0.5 mg/kg, twice per week for a total of 10 injections) were used to induce compulsive checking. In separate groups of rats, OX1R (SB334867-A; 10 μg i.c.v) and OX2R (TCS-OX2-29; 10 μg i.c.v) receptor antagonists were co-administered together with quinpirole. Checking behavior in a large open field was measured after the first, fifth, and tenth injections of the drugs. SB334867-A attenuated checking behavior and the level of anxiety. TCS-OX2-29 administration ameliorated anxiety but did not block the development of compulsive checking. Orexin 1 receptors seem to play a more critical role than orexin 2 receptors in the induction of compulsive checking. Considering that the quinpirole sensitization model of OCD involves activation of dopamine systems and sensitization to quinpirole, it is suggested that neural interaction between orexigenic and dopamine systems may be important in the pathogenesis of OCD.
Keywords: Obsessive-compulsive disorder; Orexin 1 receptor antagonist; Orexin 2 receptor antagonist; Quinpirole.