Milagros Méndez1, Marcela Morales-Mulia. 1. Departamento de Neuroquímica, Subdirección de Investigaciones Clínicas, Instituto Nacional de Psiquiatría Ramón de la Fuente, Calzada México Xochimilco 101, Col. San Lorenzo Huipulco, 14370, México DF, México. ubach@imp.edu.mx
Abstract
RATIONALE: Opioid peptides have been suggested to play a major role in ethanol reinforcement mechanisms and alcohol drinking behaviour. However, in non-selected strains of rodents, it is not known whether opioid biosynthesis is a critical event in these processes. OBJECTIVE: The aim of this work was to study the effects of a high dose of ethanol (2.5 g/kg body weight) on pro-enkephalin (pro-enk) mRNA expression in brain regions of the mesocorticolimbic system for up to 24 h after drug administration. MATERIALS AND METHODS: Male Wistar rats were administered with ethanol (2.5 g/kg body weight) or distilled water and were killed 30 min, 1, 2, 4, 8 or 24 h after treatment. Coronal brain sections (20 mu) were obtained and pro-enk mRNA expression was studied by in situ hybridization and densitometry. RESULTS: Acute ethanol administration induced a transient decrease and increase in pro-enk mRNA expression in the ventral tegmental area (33.2%) and prefrontal cortex (26.5%) 2 and 4 h after treatment, respectively. In contrast, ethanol induced prolonged increases in pro-enk mRNA expression in the core and shell regions of the nucleus accumbens, with different kinetics. Maximal effects were observed 2 h after ethanol exposure (core, 70.0%; shell, 60.0%). CONCLUSIONS: Our results indicate that enkephalin expression in regions of the rat mesocorticolimbic system is differentially altered by acute ethanol treatment and suggest that enkephalins may play a key role in ethanol reinforcement mechanisms.
RATIONALE: Opioid peptides have been suggested to play a major role in ethanol reinforcement mechanisms and alcohol drinking behaviour. However, in non-selected strains of rodents, it is not known whether opioid biosynthesis is a critical event in these processes. OBJECTIVE: The aim of this work was to study the effects of a high dose of ethanol (2.5 g/kg body weight) on pro-enkephalin (pro-enk) mRNA expression in brain regions of the mesocorticolimbic system for up to 24 h after drug administration. MATERIALS AND METHODS: Male Wistar rats were administered with ethanol (2.5 g/kg body weight) or distilled water and were killed 30 min, 1, 2, 4, 8 or 24 h after treatment. Coronal brain sections (20 mu) were obtained and pro-enk mRNA expression was studied by in situ hybridization and densitometry. RESULTS: Acute ethanol administration induced a transient decrease and increase in pro-enk mRNA expression in the ventral tegmental area (33.2%) and prefrontal cortex (26.5%) 2 and 4 h after treatment, respectively. In contrast, ethanol induced prolonged increases in pro-enk mRNA expression in the core and shell regions of the nucleus accumbens, with different kinetics. Maximal effects were observed 2 h after ethanol exposure (core, 70.0%; shell, 60.0%). CONCLUSIONS: Our results indicate that enkephalin expression in regions of the rat mesocorticolimbic system is differentially altered by acute ethanol treatment and suggest that enkephalins may play a key role in ethanol reinforcement mechanisms.
Authors: Guo-Qing Chang; Jessica R Barson; Olga Karatayev; Si-Yi Chang; Yu-Wei Chen; Sarah F Leibowitz Journal: Alcohol Clin Exp Res Date: 2010-02-24 Impact factor: 3.455