Cannabinoid administration modulates both dopaminergic and glutamatergic neurotransmission. The present study examines the effects of high and low dose WIN55,212-2, a CB1 receptor agonist, on extracellular dopamine and glutamate release in vivo via brain microdialysis in the nucleus accumbens (NAc), striatum and prefrontal cortex (PFC) in parallel to its effects on locomotor activity. WIN55,212-2 increased extracellular dopamine in the NAc (1 mg/kg i.p.), striatum (0.1 and 1 mg/kg i.p.) and PFC (1 mg/kg i.p.). Glutamate release was also elevated by WIN55,212-2 in the PFC (1 mg/kg i.p.) whereas in the NAc (0.1 and 1 mg/kg i.p.) and striatum, it was reduced (1 mg/kg i.p.). WIN55,212-2 administration produced hyperlocomotion at the lower dose (0.1 mg/kg i.p.) and hypolocomotion at the higher dose (1 mg/kg i.p.). Co-administration with the CB1 antagonist, SR-141716A (0.03 mg/kg i.p.), prevented the above effects. According to the present results, WIN55,212-2 affected locomotor activity biphasically while exerting converging effects on dopamine activity but diverging effects on glutamate release between cortical and subcortical regions, especially at the higher dose. These findings emphasize the involvement of the CB1 receptor in the simultaneous modulation of dopaminergic and glutamatergic neurotransmission in brain regions involved in reward and locomotion and suggest possible underlying mechanisms of acute cannabinoid exposure and its psychoactive and behavioural manifestations.