Genetic variability in adenosine deaminase-like contributes to variation in alcohol preference in mice.

BACKGROUND: A substantial part of the risk for alcohol use disorder (AUD) is determined by genetic factors. We previously used chromosome substitution (CSS) mice, to identify a QTL for alcohol preference on mouse chromosome 2. The aim of this study was to identify candidate genes within this QTL that confer the risk for alcohol preference. METHODS: In order to delineate the neurobiological underpinnings of alcohol consumption, we expanded on the QTL approach to identify candidate genes for high alcohol preference in mice. We narrowed down a QTL for alcohol preference on mouse chromosome 2, that we previously identified using chromosome substitution (CSS) mice, to four candidate genes in silico. Expression levels of these candidate genes in prefrontal cortex, amygdala and nucleus accumbens, brain regions implicated in reward and addiction, were subsequently compared for the CSS-2 and the C57BL/6J host strain. RESULTS: We observed increased expression of adenosine deaminase-like (Adal) in all three regions in CSS-2 mice. Moreover, we found that the adenosine deaminase inhibitor EHNA reduced the difference in alcohol preference between CSS-2 and C57Bl/6J mice. CONCLUSION: The current study identifies Adal as a genetically protective factor against alcohol consumption in mice, in which elevated Adal levels contribute to low alcohol preference. This article is protected by copyright. All rights reserved

Amygdala 14-3-3ζ as a Novel Modulator of Escalating Alcohol Intake in Mice

Alcoholism is a devastating brain disorder that affects millions of people worldwide. The development of alcoholism is caused by alcohol-induced maladaptive changes in neural circuits involved in emotions, motivation, and decision-making. Because of its involvement in these processes, the amygdala is thought to be a key neural structure involved in alcohol addiction. However, the molecular mechanisms that govern the development of alcoholism are incompletely understood. We have previously shown that in a limited access choice paradigm, C57BL/6J mice progressively escalate their alcohol intake and display important behavioral characteristic of alcohol addiction, in that they become insensitive to quinine-induced adulteration of alcohol. This study used the limited access choice paradigm to study gene expression changes in the amygdala during the escalation to high alcohol consumption in C57BL/6J mice. Microarray analysis revealed that changes in gene expression occurred predominantly after one week, i.e. during the initial escalation of alcohol intake. One gene that stood out from our analysis was the adapter protein 14-3-3ζ, which was up-regulated during the transition from low to high alcohol intake. Independent qPCR analysis confirmed the up-regulation of amygdala 14-3-3ζ during the escalation of alcohol intake. Subsequently, we found that local knockdown of 14-3-3ζ in the amygdala, using RNA interference, dramatically augmented alcohol intake. In addition, knockdown of amygdala 14-3-3ζ promoted the development of inflexible alcohol drinking, as apparent from insensitivity to quinine adulteration of alcohol. This study identifies amygdala 14-3-3ζ as a novel key modulator that is engaged during escalation of alcohol use

ERK1/2 activation in rat ventral tegmental area by the mu-opioid agonist fentanyl: An in vitro study

Opioid receptors in the ventral tegmental area, predominantly the mu-opioid receptors, have been suggested to modulate reinforcement sensitivity for both opioid and non-opioid drugs of abuse. The present study was conducted to study signal transduction proteins, which may mediate the functioning of mu-opioid receptors in the neurons of the ventral tegmental area. Therefore, brain slices of the ventral tegmental area were exposed in vitro to the specific mu-opioid agonist fentanyl and immunohistochemically stained for four different activated proteins using phospho-specific antibodies. Fentanyl dose-dependently activated extracellular signal-regulated protein in brain slices of the ventral tegmental area. This activation was reversible with naloxone. Furthermore, naloxone itself also activated extracellular signal-regulated protein kinase. Under the present conditions fentanyl did not affect extracellular signal-regulated protein kinase 1 and 2, Stat and cyclic AMP-response element-binding protein activity. The direct activation of extracellular signal-regulated protein kinase in ventral tegmental area slices by the mu-opioid agonist fentanyl may suggest a role of extracellular signal-regulated protein kinase in reward processes. (C) 2003 IBRO. Published by Elsevier Science Ltd. All rights reserved