The effect of 5-HT2A receptor stimulation on morphine withdrawal symptoms in mice

Serotonergic system has a role in morphine dependence and withdrawal symptoms via its receptors. On the other hand, the effect of 5-HT2A receptor on withdrawal symptoms has not been evaluated completely. The aim of this study was to investigate the effect of 5-HT2A receptor stimulation on morphine withdrawal symptoms in male mice.

This experimental study included twenty eight male NMRI mice (20-25g). Morphine dependency was induced in a five- day schedule by 6, 16, 26, 36, 46, 56 and 66 mg/kg doses respectively. On the fifth day, 2 hours after a single dose of morphine, naloxone was injected (3 mg/kg) and the scores (from 0 to 3) of withdrawal symptoms including number of jumps, teeth chattering, writing, head shakes, limbs shakes, and percentage of body weight loss were recorded for 30min.The treatment group received different doses of TCB-2 (03, and 2.5mg/kg; Intraperitoneally).

Withdrawal symptoms in the morphine-dependent mice were significantly more frequent than those in the control mice. Different doses of TCB-2 significantly increased some of the morphine withdrawal symptoms in the experimental groups.

The present study indicated that stimulation of 5-HT2A receptor via its agonist exacerbated the morphine withdrawal symptoms. Further studies are recommended to better understand the role of the 5-HT2A receptor in morphine dependence and withdrawal.