FLUOXETINE ATTENUATES MORPHINE-INDUCED LOCOMOTION AND BLOCKS MORPHINE-SENSITIZATION

Repeated morphine treatments result in sensitization, an increase in t he efficacy of morphine to stimulate locomotor activity. study examine d the effects of increasing serotonin (5-hydroxytryptamine, 5-HT) tran smission on morphine-sensitization. For five days rats were administer ed saline or 5.0 mg/kg fluoxetine prior to treatment with saline or 5. 0 mg/kg morphine. Twenty-one days later, rats were tested for their lo comotor response to 2.0 mg/kg morphine. Fluoxetine treatment attenuate d the locomotor activating effect of acute morphine treatments and blo cked the sensitized response to the morphine challenge. These results indicate that increased 5-HT transmission attenuates the locomotor sti mulating effects of morphine and prevents the development of morphine- sensitization. (C) 1997 Elsevier Science B.V.