The effects of (−)‐Δ9‐tetrahydrocannabinol on reserpine‐induced hypothermia in rats

Abstract

An intravenous injection into rats of 1 mg/kg (—)‐Δ9‐tetrahydrocannabinol Δ9‐THC) had no effect on rectal temperature and produced in the subcellular fractions of the brain a shift of 5‐hydroxytryptamine (5‐HT) from the particulate or ‘bound’ 5‐HT to the supernatant or ‘free’ fraction, whereas the noradrenaline (NA) decreased in both fractions. Pretreatment of rats by an intravenous injection of 1 mg/kg Δ9‐THC three times a week for four weeks, prevented the hypothermia and the reduction in brain 5‐HT produced by an intraperitoneal injection of 15 mg/kg reserpine given 24 h after the last Δ9‐THC injection. Pretreatment of rats by a single intravenous injection of 1 mg/kg Δ9‐THC prevented the hypothermia and reduction in brain 5‐HT produced by an intraperitoneal injection of reserpine given 1 h before. The reduction in brain NA was not prevented except at the 18 h time interval. An injection of 1 mg/kg Δ9‐THC intravenously into rats 3 h after an intraperitoneal injection of reserpine accentuated the reserpine hypothermia as well as the reduction of 5‐HT but not of NA in the brain. The reserpine hypothermia was not prevented by a single intravenous injection of 1 mg/kg Δ9‐THC when cinanserin, a 5‐HT inhibitor, was injected 30 min before the reserpine. 1973 British Pharmacological Society