Change in brain neurosteroid level of rats in morphine addiction and stress-induced addiction relapse condition / 中国药理学与毒理学杂志

ABSTRACT

AIM To investigate if morphine addiction and relapse to morphine-seeking is related to the change in neurosteroid levels in the brain of rats. METHODS Rats were injected ip morphine (5 mg·kg-1·d-1, 1800-2000) and trained in conditioned place preference (CPP) box, once daily for 10 d. CPP test was performed 24 h after the last training. After discontinuation of training for 7 d for CPP extinction, then intermittent and inescapable foot-shock (FS, 0.5 mA, 0.5 s on, 40 s off, 15 min) was applied to rats as the priming stimuli for relapse. CPP test was performed 2 h after FS. When CPP test finished, rats were decapitated and the levels of neurosteroids were analyzed using gas chromatography/mass spectrometry. RESULTS CPP was established when rats were injected morphine and trained for 10 d. At the same time, the levels of pregnenolone and allopregnanolone in the brain tissues of rats were significantly increased. When CPP was reinstated in morphine-treated rats by FS-stress after 7 d CPP extinction, the levels of dehydroepiandrosterone and dehydroepiandrosterone sulfate were significantly increased. CONCLUSIONThe development of morphine addiction and relapse may be related to endogenous neurosteroids in rat brain tissues.