A behavioural comparison of acute and chronic Δ9- tetrahydrocannabinol and cannabidiol in C57BL/6JArc mice

Cannabis contains over 70 unique compounds and its abuse is linked to an increased risk of developing schizophrenia. The behavioural profiles of the psychotropic cannabis constituent 9-tetrahydrocannabinol ( 9-THC) and the non-psychotomimetic constituent cannabidiol (CBD) were investigated with a battery of behavioural tests relevant to anxiety and positive, negative and cognitive symptoms of schizophrenia. Male adult C57BL/6JArc mice were given 21 daily intraperitoneal injections of vehicle, 9-THC (0.3, 1, 3 or 10 mg/kg) or CBD (1, 5, 10 or 50 mg/kg). 9-THC produced the classic cannabinoid CB1 receptor-mediated tetrad of hypolocomotion, analgesia, catalepsy and hypothermia while CBD had modest hyperthermic effects. While sedative at this dose, 9-THC (10 mg/kg) produced locomotor-independent anxiogenic effects in the open-field and light-dark tests. Chronic CBD produced moderate anxiolytic-like effects in the open-field test at 50 mg/kg and in the light-dark test at a low dose (1 mg/kg). Acute and chronic 9-THC (10 mg/kg) decreased the startle response while CBD had no effect. Prepulse inhibition was increased by acute treatment with 9-THC (0.3, 3 and 10 mg/kg) or CBD (1, 5 and 50 mg/kg) and by chronic CBD (1 mg/kg). Chronic CBD (50 mg/kg) attenuated dexamphetamine (5 mg/kg)-induced hyperlocomotion, suggesting an antipsychotic-like action for this cannabinoid. Chronic 9-THC decreased locomotor activity before and after dexamphetamine administration suggesting functional antagonism of the locomotor stimulant effect. These data provide the first evidence of anxiolytic- and antipsychotic-like effects of chronic but not acute CBD in C57BL/6JArc mice, extending findings from acute studies in other inbred mouse strains and rats.