Introduction: For the treatment of tuberculosis, a hydrazine derivative called isoniazid is considered as firstline medication. This drug may modulate GABAergic brain systems. Previous research has shown that modulation of GABAergic brain system by GABA agents might alter the naloxone-induced withdrawal signs in morphine-dependent animals. Therefore, the purpose of the present study was to evaluate the effects of isoniazid on withdrawal signs (jumping and diarrhea) induced by naloxone in morphine-dependent mice. Methods: The protocol for mice dependence induction involved 10 injections of high doses of morphine; in this method, mice received three times a day for three consecutive days morphine (50, 50, and 75 mg/kg, s.c.) and on the fourth day received only one morphine injection (50 mg/kg, s.c.). Two hour after the last dose of morphine each mouse received naloxone. Moreover, for evaluation of isoniazid effects on the expression of morphine dependence, four groups of mice (8 in each group) one hour before naloxone received saline or isoniazid (25, 50, and 75 mg/kg, i.p.). Results: Administration of isoniazid (25, 50 and 75 mg/kg) on the test day, compared to the saline-treated animals, could reduce the expression of morphine withdrawal signs (jumping behavior and diarrhea) in mice that are dependent on morphine, significantly. Conclusion: Isoniazid may be considered as a drug for the amelioration of morphine withdrawal signs.
