RESUMEN
Cuminum cyminum fruit essential oil [FEO] dose-dependently can attenuate the expression of morphine tolerance and dependence in morphine-dependent mice. In this study, the effects of Cuminum cyminum FEO on acquisition and expression of morphine-induced conditioned place preference [CPP] in morphine-sensitized mice were studied. Repeated subcutaneous [s.c.] administration of morphine [5 mg/kg], once daily for three and 5 days free of the opioid [sensitization period], increased conditioning response induced by ineffective doses of morphine [0.25, 0.5 and 0.75 mg/kg]. The results showed that intra-peritoneal [i.p.] injection of Cumin FEO [0. 001, 0.01, 0. 1, 0.5, 1 and 2%; 5 ml/kg] or Tween-80 [0.5%; 5 ml/kg], 60 mm before administration of morphine or saline during sensitization period [acquisition], decreased the conditioning response induced by ineffective dose of morphine [0.5 mg/kg; s.c.] at the doses of 1% [P<0.05] and 2% [P<0.001] while Cumin FEO [0.001-2%; i.p.], just 60 mm before the test on post-conditioning phase [expression experiments], did not alter the conditioning scores in morphine-and non-sensitized mice. Our findings showed that the Cuminum cyminum fruit essential oil reduces the acquisition but not expression of morphine-induced conditioned place preference in morphine-sensitized mice