Diverse effects of acute and chronic administrated levothyroxine on the morphine withdrawal syndrome in male mice

Introduction: Some studies indicate changes in the level of thyroid hormones in addicted people. Also, there are some reports concerning the modulation of hypothalamus-hypophysis-thyroid axis in the context of morphine addiction. In the present study, the effects of thyroid gland activation via the acute and chronic administration of levothyroxine on morphine withdrawal syndrome were investigated. Methods: Frothy two adult male mice were divided into 6 groups. Animals received three daily injections of morphine (20, 40, 80 mg/kg) alone or in combination with l-thyroxin (0.5 mg/kg, i.p: single dose, chronic for 4 days and chronic for 16 days). Morphine withdrawal syndrome was induced using naloxone. Withdrawal signs such as jumping, rearing, climbing and weight loss were recorded for 30 minutes. Results: The results showed that acute levothyroxine administration increased the morphine withdrawal signs. Four days administration of levothyroxine reduced the number of jumping and climbing and inhibited weight loss. Administration of levothyroxine for 16 days reduced only the number of rearing. Conclusions: It seems that levothyroxine via alteration of thyroid hormones level can affect morphine withdrawal signs and this effect of levothyroxine can be attenuated with its repetitive administration.