Chronic cannabinoid, CP-55,940, administration alters biotransformation in the rat.

The objective of this study was to investigate the effects of single and repeated administration of CP-55,940 [(-)-cis-3-[2-hydroxy-4-(1, 1-dimethylheptyl)-phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol)] on behaviour, energy metabolism and biotransformation. Single intraperitoneal administration to male Sprague-Dawley rats of CP-55,940 (0.4 mg/kg), induced a behavioural response characterized by 'splayed hind limbs', antinociception, hypothermia and a decrease in locomotor activity. Brain and liver mitochondria of the CP-55,940-treated rats exhibited an increase in respiration and no changes in ADP/O and citrate synthase specific activity. Repeated intraperitoneal administration of CP-55,940 (0.4 mg/kg, 11 days) induced behavioural tolerance, disappearance of the increase in the mitochondrial oxygen consumption as well as an increase in the monooxygenase activities and the content of liver microsomal cytochrome P450. Some hepatic metabolizing enzymes of the cytosolic glutathione-centre system were also affected. Previous studies had indicated that the tolerance after chronic administration of CP-55,940 could be due to down-regulation of brain cannabinoid receptors. The present findings demonstrate that the behavioural tolerance occurs together with modified biotransformation activities.