Background and Aim:marijuana is a narcotic increasingly has been used in recent decades and can cause damages in brain higher function such as attention and memory. These effects are mediated by phytocannabinoids. Entering the body and connecting to cannabinoid receptors, these compounds can activate the endocannabinoid system. This system is spread and active in the whole body and has interaction with the other systems such as opioid system. Anti-pain and anti-inflammatory effects are results of function of this system. This research investigates the effects of acute injection of hexane extracts of marijuana on anxiety and motor activity. Methods:First, 50g marijuana was heated in 180°C for 10 minutes and hexane extract was produced from it. Then 18 male wistar rats weighing 250-300g grouped into 3 (each consist of 6 rats) for injection: control group with no injection, sham group with i.p. injection of the solution used as vehicle (Tween 80, ethanol and saline with 1/1/8 proportions) and the last group with i.p. injection of the extract in 50mg/kg dosage. To investigate anxiety each group was tested with plus maze. Results:Data analyzing showed injection of marijuana cause significant decrease in time spent in the open arms (so increasing the level of anxiety) (p<0.01). Conclusion:marijuana like other narcotics may be able to affect anxiety and stress via probable altering synaptic activity of limbic neurons. Prelimbic region and medial prefrontal cortex are projected to parts of the brain involved in fear and anxiety, because of the presence of cannabinoid 〖CB〗_1 and non-cannabinoid Transient Receptor Potential Vanilloid Type 1 (TRPV1) receptors ,so, this regions is affected by both cannabinoid and endovanilloid systems. Probably cannabinoids of marijuana has more affinity to TRPV1 than 〖CB〗_1 in prelimbic region. Activation of TRPV1 elevates entrance of calcium and release of mediators such as glutamate and nitric oxide which involved in anxious responses. Affecting serotonin neurons is another reason for anxiety and decrease of motor activity. Serotonin decreases the release of ACTH and Corticostron and induces anti-anxiety behavior. But probably cannabinoids inhibits release of Serotonin via activation of 〖CB〗_1 receptors which presented in serotonin neurons.

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