Administration of Cannabis extracts causes alteration in brain and plasma nitric oxide concentration in rats

Nitric oxide is a biological messenger molecule that plays important roles in controlling neurotransmitter release, neurodevelopment, memory function, and regulation of gene expression. In this study, the time course effects of varying dose of Cannabis extract on nitric oxide in the brain and plasma was investigated. Twenty four hours after the last treatment, animals were sacrificed under anaesthesia, the brain of the animals were harvested, mopped dry and stored on ice. Nitric oxide activity was assayed according to Griess reaction assay. In the plasma, the results shows that at 4 weeks, there was a significant increase (p < 0.05) in the concentration of nitric oxide in all doses with compared with control. 25 mg/kg dose has a higher concentration compared with 12.5 mg/kg and 50 mg/kg body weight dose. However, at 8 weeks, there was a decrease in concentration of nitric oxide in all the doses compared to 4 weeks, but when compared with the control group, only 12 mg/kg dose significantly decreased. In the brain however, 12.5 mg/kg dose shows no significant difference in NO concentration through the duration of exposure compared to the control group. However, 25 mg/Kg and 50 mg/Kg body weight dose of Cannabis significantly decrease NO concentration in the brain of rat. The results suggest that at high doses, NO is reduced in the brain and at low dose its increased. The decrease in NO concentration may affect the regulatory function of NO in the brain as nitric oxide affect serotonergic transmission which could explain the imopaired cognitive function in chronic Cannabis users.