Ethanol-induced Changes in Proenkephalin mRNA Expression in the Rat Nigrostriatal Pathway |
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Authors: | Milagros Méndez Marcela Morales-Mulia José Manuel Pérez-Luna |
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Institution: | (1) Instituto Nacional de Psiquiatría Ramón de la Fuente, Subdirección de Investigaciones Clínicas, Departamento de Neuroquímica, Calzada México Xochimilco 101, Col. San Lorenzo Huipulco, 14370 México D.F., México |
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Abstract: | Endogenous opioid systems have been suggested to play a key role in ethanol reinforcement mechanisms and alcohol-drinking
behavior. Ethanol induces differential alterations in opioid peptide expression in brain areas of the reward circuits, which
may be linked to the reinforcing effects of ethanol. In addition, ethanol-induced alterations in opioidergic nigrostriatal
transmission could be involved in brain sensitivity to ethanol and play a role in addictive processes. The aim of this work
was to study the effects of acute ethanol administration on proenkephalin (proenk) mRNA expression in the rat substantia nigra
and caudate–putamen (CP) for up to 24 h post treatment. Male Wistar rats received ethanol (2.5 g/kg) or distilled water by
intragastric administration, and proenk mRNA expression was studied by in situ hybridization and densitometry. Ethanol transiently
increased proenk mRNA expression in the CP 1 h after drug administration. Proenk mRNA levels remained elevated 2 h post treatment
in the anterior–medial and medial–posterior regions of the CP. In contrast, ethanol decreased proenk mRNA expression in the
substantia nigra pars compacta and pars reticulata 2 h after drug exposure. Alterations in enkephalin expression in the substantia
nigra and CP in response to ethanol exposure could be involved in the mechanisms underlying brain sensitivity to the drug. |
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Keywords: | Ethanol Opioid peptides Enkephalins Proenkephalin mRNA Nigrostriatal pathway |
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