Dual Effects of Exposure Therapy and Cannabis Sativa Extract on Extinction of Conditioned Fear Memory in PTSD Male Rats

Objectives Posttraumatic stress disorder is a severe anxiety disorder caused by exposure to traumatic events. Traumatic memory impairment is one of the clinical signs of this disorder. Cannabis sativa is full of cannabinoid compounds that are effective on memory extinction. We evaluated the combined effects of Cannabis leave extract and exposure therapy on memory extinction in this disease.
Methods Modified single prolonged stress model was used to induce PTSD. A week later, rats were placed in a shock chamber and received a shock. After 24 hours, for the first time exposure, rats were returned to the chamber for 9 minutes, without receiving any footstock. Two other exposures were performed with one day interval. Cannabis leave extract (at three different doses) was injected 30 minutes before exposures. 14 days later, for fear memory evaluation, again rats were placed in the chamber. In order to evaluate the participation of cannabinoid system in the effects of cannabis, second experiment was accomplished. Effective dose of cannabis extract and cannabinoid receptor antagonist (Rimonabant) were simultaneously injected, as in the first experiment.
Results Results of the first experiment showed that 25 mg/kg cannabis leave extract significantly decreased the percent of freezing as compared to control group. In the second experiment, percent of freezing in rats treated with extract and antagonist increased as compared to related control group.
Conclusion Simultaneous treatment with exposure therapy and cannabis leave extract, with 25 mg/kg dosage, intensely led to condition memory extinction. Maybe this kind of treatment enhanced and consolidated the memory extinction by affecting cannabinoid system through CB1 receptor.