Effect of buspirone on morphine withdrawal syndrome in mice

Several studies indicate that central serotonergic neurons have important role in tolerance and dependency to morphine. The aim of this study was to investigate effect of buspirone (as a partial agonist of 5-HT1A receptors) in severity of morphine withdrawal syndrome in mice. Study was carried out on Swiss male albino mice weighing 25-30g. In order to induce dependency, we used daily subcutaneous injection of morphine at the schedule of: day 1=5 mg/kg; days 2-3=10 mg/kg; days 4-5=15 mg/kg; days 6-7=20 mg/kg and days 8-9= 25mg/kg. Withdrawal syndrome was induced by intraperitoneal (i.p.) injection of naloxone (5 mg/kg) and then straub tail and jumps were recorded during 40 min period as indicators of morphine withdrawal syndrome. In treated groups, buspirone (5, 7.5 and 10 mg/kg, i.p.) was co-injected daily with morphine and severity of naloxone induced withdrawal behaviors were recorded at day 9. Our results showed that naloxone induces sever (P<0.001) withdrawal behaviors (as indicated by straub tail and jumping behaviors) in morphine dependent mice. Daily coinjection of buspirone (5, 7.5 and 10 mg/kg) with morphine caused significant (P<0.001) reduction in straub tail and jumping behaviors. Buspirone (5, 7.5 and 10 mg/kg) did not produced any significant effect on morphine withdrawal syndrome. Results of this study show that buspirone attenuates morphine withdrawal behaviors.