Effects of repeated administration with CP-55,940, a cannabinoid CB1 receptor agonist on the metabolism of the hepatic heme.

Drugs metabolised by cytochrome P450 (CYP) such as analgesics may induce acute attacks in patients with hepatic porphyrias. In recent years, preclinical and clinical studies have suggested that cannabinoid pharmaceutical preparations may be potentially useful in the treatment of pain. The purpose of the study was to examine the effects of CP-55,940, a cannabinoid CB1 receptor agonist, on the hepatic heme metabolism in mice. To this end, hepatic activities of aminolevulinic acid synthase (ALAS), heme oxygenase (HO) and CYP levels were determined in mice treated with CP-55,940 (0.5 mg/kg/day; i.p.; 5 or 24 days). Results showed that treatment with CP-55,940 decreased CYP concentrations by 80% and increased HO activity by 158%. However, ALAS activity also decreased by 37%, suggesting that regulatory free heme pool was not modified. Our findings indicate that CP-55,940 and its metabolites do not behave as porphyrinogenic drugs and may potentially be safe for treating pain in patients with acute porphyrias.

Extinction of cocaine self-administration produces alterations in corticotropin releasing factor gene expression in the paraventricular nucleus of the hypothalamus.

The long-term effect of cocaine self-administration on corticotropin releasing factor (CRF) mRNA content in the hypothalamic CRF-containing neurons has not yet been established. The purpose of this study was to examine the time course effects of the extinction of cocaine self-administration behavior on CRF gene expression in the paraventricular nucleus of the hypothalamus (PVN) using in situ hybridization histochemistry (IHHS). Seventy-two littermate male Lewis rats were randomly assigned in triads to one of three conditions: (a) contingent intravenous self-administration of 1 mg/kg/injection of cocaine (CONT), (b) non-contingent injections of either 1 mg/kg/injection of cocaine (NONCONT) or (c) saline yoked (SALINE) to the intake of the self-administering subject. The self-administering rats were trained to self-administer cocaine under a fixed ratio 5 (FR5) schedule of reinforcement for a minimum of 3 weeks. After stable baseline levels of drug intake had been reached, saline was substituted for drug. Following this first extinction period, cocaine self-administration was reinstated for an additional period of 2 weeks. Immediately after cessation of the last session of cocaine self-administration (Day 0) and 1, 5 and 10 days after the second extinction period, animal brains in each triad were removed to be processed for IHHS. CRF mRNA levels in the PVN were significantly lower in the NONCONT cocaine group at Day 0 compared to CONT or SALINE groups. On Day 1, hypothalamic CRF gene expression significantly decreased in the CONT cocaine group with respect to the SALINE group, but there were no differences between the cocaine groups or among the NONCONT cocaine and SALINE groups. After 5 and 10 days of extinction, no differences were found in CRF mRNA content in the PVN between the three conditions of this study. These results suggest that, after the extinction of cocaine self-administration, changes in hypothalamic CRF gene expression are differentially affected depending upon the type of cocaine administration, and that the stages of cocaine withdrawal might not be associated with enduring changes in hypothalamic CRF mRNA levels.