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Neural mechanisms underlying a conditioned place preference induced by morphine

The present study used the conditioned place preference (CPP) paradigm to examine the neural mechanisms underlying morphine's rewarding effect in the rat. Of thirteen sites tested with intra-cerebral morphine injections, only the ventral tegmental area (VTA) and periaqueductal gray (PAG) produced a CPP, suggesting that morphine's rewarding effect is initiated by an action at these sites. The CPPs induced by intra-VTA and intra-PAG morphine may be produced by different mechanisms because animals conditioned with these two injections exhibited different patterns of behaviour during testing. Injections of a quaternary opioid antagonist into either the VTA or PAG blocked a CPP to systemic morphine, confirming that opiate-induced reward is mediated via opioid receptors in these sites. Lesions of the pedunculopontine tegmental nucleus (PPT$ rm sb{g}),$ ventral striatum (VS), PAG, or fornix reduced a CPP to morphine, although PAG and fornix lesioned animals displayed a CPP when tested in a drugged state. These findings suggest that PPT$ rm sb{g}$ and VS lesions reduce the rewarding effect of morphine, and that PAG and fornix lesions disrupt the ability to retrieve information about the relationship between conditioned and unconditioned stimuli.

Identiferoai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.29102
Date January 1995
CreatorsOlmstead, Mary C.
ContributorsFranklin, Keith B. J. (advisor)
PublisherMcGill University
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
LanguageEnglish
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Formatapplication/pdf
CoverageDoctor of Philosophy (Department of Psychology.)
RightsAll items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated.
Relationalephsysno: 001480798, proquestno: NN08142, Theses scanned by UMI/ProQuest.

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