Effect of morphine on circling behaviour in rats with 6-hydroxydopamine striatal lesions and electrolesions of the raphe nucleus.
Morphine antagonized d-amphetamine circling in rats which had received unilateral 6-OHDA lesions of the striatum but failed to reduce the circling in rats with both a unilateral 6-OHDA striatal lesion and a raphe (5-HT) lesion. Naloxone precipitated withdrawal of morphine tolerant rats greatly enhanced d-amphetamine circling when the rats had a 6-OHDA lesion but not when both 6-OHDA and raphe lesions were present. It is concluded that 5-HT is necessary for the morphine-induced inhibition of the circling. The effect of morphine tolerance and naloxone precipitated withdrawal on brain 5-HT function was investigated using a putative 5-HT rotation model in which both a dopamine and a 5-HT agonist were administered to rats with an asymmetrical medial raphe lesion. The findings suggest that chronic treatment with morphine increases striatal 5-HT function.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001933:Brain Stem / Q000502:physiology*; D003342:Corpus Striatum / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology; D005260:Female; D006801:Humans; D006892:Hydroxydopamines / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009474:Neurons / Q000502:physiology; D011814:Quipazine / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D012701:Serotonin / Q000502:physiology; D013239:Stereotyped Behavior / Q000187:drug effects*
D006892:Hydroxydopamines; D012701:Serotonin; D011814:Quipazine; D009020:Morphine; D001058:Apomorphine; D003913:Dextroamphetamine; D004298:Dopamine