Involvement of nitric oxide in anticompulsive-like effect of agmatine on marble-burying behaviour in mice

In view of the reports that nitric oxide modulates the neurotransmitters implicated in obsessive–compulsive disorder (OCD), patients with OCD exhibit higher plasma nitrate levels, and drugs useful in OCD influence nitric oxide. Agmatine is a polyamine and widely distributed in mammalian brain which interacts with nitrergic systems. Hence, the present study was carried out to understand the involvement of nitrergic systems in the anticompulsive-like effect of agmatine. We used marble-burying behaviour (MBB) of mice as the animal model of OCD, and nitric oxide levels in hippocampus (HC) and cortex homogenate were measured. Results revealed that, agmatine (20 and 40 mg/kg, i.p) significantly inhibited the MBB. Intraperitoneal administration of nitric oxide enhancers viz. nitric oxide precursor – l-arginine (l-ARG) (400 mg/kg and 800 mg/kg) increased MBB as well as brain nitrites levels, whereas treatment with NG-nitro-l-arginine methyl ester (l-NAME) neuronal nitric oxide synthase inhibitor (30 mg/kg and 50 mg/kg, i.p.) and 7-nitroindazole (7-NI) (20 mg/kg and 40 mg/kg) attenuated MBB and nitrites levels in brain. Further, in combination studies, the anticompulsive-like effect of agmatine (20 mg/kg, ip) was exacerbated by prior administration of l-ARG (400 mg/kg) and conversely l-NAME (15 mg/kg) or 7-NI (10.0 mg/kg) attenuated OCD-like behaviour with HC and cortex changes in the levels of NO. None of the above treatment had any significant influence on locomotor activity. In conclusion, Agmatine is effective in ameliorating the compulsive-like behaviour in mice which appears to be related to nitric oxide in brain.