[Electroacupuncture suppresses morphine--induced conditioned place preference (CPP) in rats].

OBJECTIVE To examine the effects produced by electroacupuncture (EA) of different frequencies on the expression of morphine conditioned place preference (CPP) in rats. METHODS SD rats were given 4 days consecutive trials in a computerized three-chamber "unbiased" CPP apparatus. Twenty-four hours later, the time spent on drug-pairing compartment of the rat was examined. Rats trained with CPP paradigms were then given EA of 2 Hz or 100 Hz once a day for 3 days. Twenty-four hours after the final EA session, they were again put to the CPP chamber, and the time spent on drug-pairing compartment was measured. RESULTS Rats receiving morphine at a dose of 4 mg.kg-1 (i.p.) showed significantly enhanced preference scores in drug-pairing side than that of the control group. In other words, rats preferred the drug-pairing environment to the nondrug-pairing place. In addition, rats that received treatment with EA of 2 Hz or 100 Hz spent significantly less time on the drug pairing side than that of the CPP control group. CONCLUSION Morphine-induced CPP paradigms were stably established in rats using a computer-controlled 3-chamber CPP experimental system. The expression of CPP could be significantly inhibited by multiple treatments with EA of either 2 Hz or 100 Hz.