Attenuation of morphine tolerance and dependence in scopolamine-treated rats

MORPHINE tolerance and dependence were investigated in scopolamine-treated rats. The results showed that scopolamine treatment (up to 2 mg/kg) did not affect basal line or morphine-induced latency in the tail-flick test but s ignificantly increased the escape latency in the Morris water-maze task. Go -administration of scopolamine could considerably attenuate development of morphine tolerance and naloxone-precipitated with-drawal al syndrome. Pretr eatment of scopolamine for 7 days prior to morphine administration also sig nificantly reduced the tolerance and withdrawal symptoms. Scopolamine treat ment was further shown to attenuate morphine-induced conditioned place pref erence, an indicator of morphine psychological dependence. The present stud y demonstrated the attenuation of morphine tolerance and dependence in scop olamine-treated animals, probably related to scopolamine-produced learning and memory impairment. NeuroReport 10:2007-2010 (C) 1999 Lippincott William s & Wilkins.