Changes in expression of cytochrome cholesterol side chain cleavage enzyme in the brain of morphine-dependent rats

Abstract

Objective To evaluate the changes in the expression of cytochrome cholesterol side chain cleavage enzyme (P450scc) in the brain of morphine-dependent rats. Methods Twenty-four male SD rats aged 4-8 months weighing 180-200 g were randomly divided into 3 groups (n = 8 each): group Ⅰ normal saline (group NS), group Ⅱ morphine dependence (group MD) and group Ⅲ morphine withdrawal (group MW). In group MD and MW, the rats were given intraperitoneally increasing doses of morphine starting from 5 mg/kg to 10, 15, 20, 30, 40 and 50 mg/kg twice a day for 7 days. In group NS, the rats were given equal volume of normal saline instead of morphine. The rats were decapitated 1 h after last injection in group NS and MD. In group MW, naloxone 2 mg/kg was given 1 h after last injection, and then the animals were decapitated 30 min after withdrawal symptoms were observed. The brains were immediately removed and the frontal cortex, hippocampus, striatum and thalamus were separated. The expression of P450see was determined by Western blot. Results The expression of P450scc in the frontal cortex, hippocampus and striatum was significantly decreased in group MD and MW compared with group NS (P<0.05). Conclusion The down-regulation of P450scc expression might be involved in the development of morphine dependence, but it is not involved in the morphine withdrawal. Key words: Morphine dependence; Brain; Cholesterol side-chain cleavage enzyme