Prevalence and influence of cys407* Grm2 mutation in Hannover-derived Wistar rats: mGlu2 receptor loss links to alcohol intake, risk taking and emotional behaviour.

Modulation of metabotropic glutamate 2 (mGlu2) receptor function has huge potential for treating psychiatric and neurological diseases. Development of drugs acting on mGlu2 receptors depends on the development and use of translatable animal models of disease. We report here a stop codon mutation at cysteine 407 in Grm2 (cys407*) that is common in some Wistar rats. Therefore, researchers in this field need to be aware of strains with this mutation. Our genotypic survey found widespread prevalence of the mutation in commercial Wistar strains, particularly those known as Han Wistar. Such Han Wistar rats are ideal for research into the separate roles of mGlu2 and mGlu3 receptors in CNS function. Previous investigations, unknowingly using such mGlu2 receptor-lacking rats, provide insights into the role of mGlu2 receptors in behaviour. The Grm2 mutant rats, which dominate some selectively bred lines, display characteristics of altered emotionality, impulsivity and risk-related behaviours and increased voluntary alcohol intake compared with their mGlu2 receptor-competent counterparts. In addition, the data further emphasize the potential therapeutic role of mGlu2 receptors in psychiatric and neurological disease, and indicate novel methods of studying the role of mGlu2 and mGlu3 receptors. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Accumbal µ-Opioid Receptors Modulate Ethanol Intake in Alcohol-Preferring Alko Alcohol Rats.

BACKGROUND: The nucleus accumbens shell is a key brain area mediating the reinforcing effects of ethanol (EtOH). Previously, it has been shown that the density of µ-opioid receptors in the nucleus accumbens shell is higher in alcohol-preferring Alko Alcohol (AA) rats than in alcohol-avoiding Alko Non-Alcohol rats. In addition, EtOH releases opioid peptides in the nucleus accumbens and opioid receptor antagonists are able to modify EtOH intake, all suggesting an opioidergic mechanism in the control of EtOH consumption. As the exact mechanisms of opioidergic involvement remains to be elucidated, the aim of this study was to clarify the role of accumbal µ- and κ-opioid receptors in controlling EtOH intake in alcohol-preferring AA rats. METHODS: Microinfusions of the µ-opioid receptor antagonist CTOP (0.3 and 1 µg/site), µ-opioid receptor agonist DAMGO (0.03 and 0.1 µg/site), nonselective opioid receptor agonist morphine (30 µg/site), and κ-opioid receptor agonist U50488H (0.3 and 1 µg/site) were administered via bilateral guide cannulas into the nucleus accumbens shell of AA rats that voluntarily consumed 10% EtOH solution in an intermittent, time-restricted (90-minute) 2-bottle choice access paradigm. RESULTS: CTOP (1 µg/site) significantly increased EtOH intake. Conversely, DAMGO resulted in a decreasing trend in EtOH intake. Neither morphine nor U50488H had any effect on EtOH intake in the used paradigm. CONCLUSIONS: The results provide further evidence for the role of accumbens shell µ-opioid receptors but not κ-opioid receptors in mediating reinforcing effects of EtOH and in regulating EtOH consumption. The results also provide support for views suggesting that the nucleus accumbens shell has a major role in mediating EtOH reward.

Addiction research centres and the nurturing of creativity: the Department of Alcohol, Drugs and Addiction at the National Institute for Health and Welfare in Finland: diverse problems, diverse perspectives.

The Department of Alcohol, Drugs and Addiction started operations on 1 January 2009, when the National Institute of Public Health (KTL) and the National Research and Development Centre for Welfare and Health (STAKES) were merged. The newly formed institute, called the National Institute for Health and Welfare (THL), operates under the Finnish Ministry of Social Affairs and Health. The scope of the research and preventive work conducted in the Department covers alcohol, drugs, tobacco and gambling issues. The two main tasks of the Department are (i) to research, produce and disseminate information on alcohol and drugs, substance use, addictions and their social and health-related effects and (ii) to develop prevention and good practices with a view to counteracting the onset and development of alcohol and drug problems and the damaging effects of smoking and other addictions. The number of staff hovers at approximately 60 people. The Department is organized into three units, one specialized in social sciences (the Alcohol and Drug Research Unit), another in laboratory analytics (the Alcohol and Drug Analytics Unit) and the third primarily in preventive work (the Addiction Prevention Unit). These units incorporate a rich variety and long traditions of both research and preventive work. The mixture of different disciplines creates good opportunities for interdisciplinary research projects and collaboration within the Department. Also, the fact that in the same administrative context there are both researchers and people specialized in preventive work opens up interesting possibilities for combining efforts from these two branches. Nationally, the Department is a key player in all its fields of interest. It engages in a great deal of cooperation both nationally and internationally, and among its strengths are the high-quality, regularly collected long-term data sets.

Opioidergic modulation of ethanol self-administration in the ventral pallidum.

BACKGROUND: Striatopallidal medium spiny neurons have been viewed as a final common path for drug reward and the ventral pallidum as an essential convergent point for hedonic and motivational signaling in the brain. The medium spiny neurons are GABAergic, but they colocalize enkephalin. Purpose of this study was to investigate the role of the opioidergic mechanisms of the ventral pallidum in ethanol self-administration behavior. METHODS: Effects of bilateral microinjections of µ-, δ-, and κ-opioid receptor agonists and antagonists into the ventral pallidum on voluntary ethanol consumption were monitored in alcohol-preferring Alko Alcohol (AA) rats using the 90-minute limited access paradigm. RESULTS: Stimulation of µ-opioid receptors with DAMGO (0.01 to 0.1 µg) or morphine (1 to 10 µg) in the ventral pallidum decreased ethanol intake dose-dependently. Conversely, blocking µ-receptors with CTOP (0.3 to 3 µg) increased ethanol intake significantly. Unlike CTOP, DAMGO also increased locomotor activity. Consumption of ethanol was not modified significantly by a broad-spectrum opioid receptor antagonist naltrexone, by δ-opioid receptor agonist DPDPE or antagonist naltrindole, or by a κ-opioid receptor agonist U50,488H or antagonist nor-BNI. CONCLUSIONS: The study provides evidence for µ- but not δ- or κ-opioid receptors in the ventral pallidum playing a role in the regulation of voluntary ethanol consumption. Furthermore, present findings give support to earlier work, suggesting an essential role of pallidal opioidergic transmission in drug reward.

DARPP-32 and Akt regulation in ethanol-preferring AA and ethanol-avoiding ANA rats.

Ethanol and other addictive drugs affect many intracellular phosphorylation and dephosphorylation cascades. These cascades are thought to be highly important in the regulation of neuronal activity. The present experiments characterized the regulation of three key signaling molecules, DARPP-32 (dopamine and cAMP regulated phosphoprotein, 32kDa), Akt kinase and ERK1/2 (extracellular signal-regulated kinase 1 and 2) in ethanol-preferring AA (Alko, alcohol) and ethanol-avoiding ANA (Alko, non-alcohol) rat lines. Radioactive in situ hybridization was used in drug naïve animals and Western blotting after acute ethanol administration in striatum, hippocampus and prefrontal cortex. The mRNA levels of DARPP-32 in striatal areas were higher in ANA rats than in AA rats. There was no difference in the striatal enriched phosphatase (STEP61), the downstream target of DARPP-32 expression between the rat lines. Ethanol (1.5g/kg) increased phosphorylation of DARPP-32 at threonine 34 in both AA and in ANA rats indicating that acute ethanol activates DARPP-32 similarly in these rat lines. The expression of Akt kinase was higher in the CA1 of hippocampus in ANA than in AA rats and acute ethanol activated Akt in hippocampus in ANA but not in AA rats. No significant alterations in the regulation of ERK1/2 were found in either rat line. Our findings suggest that DARPP-32 and Akt are regulated by ethanol and differences in the regulation of these molecules might contribute to the dramatically different ethanol drinking patterns seen in AA and ANA rats.

Differences in basal and morphine-induced FosB/DeltaFosB and pCREB immunoreactivities in dopaminergic brain regions of alcohol-preferring AA and alcohol-avoiding ANA rats.

Besides alcohol, alcohol-preferring AA and alcohol-avoiding ANA rats differ also with respect to other abused drugs. To study the molecular basis of these differences, we examined the expression of two transcription factors implicated in addiction, DeltaFosB and pCREB, in brain dopaminergic regions of AA and ANA rats. The effects of morphine and nicotine were studied to relate the behavioral and molecular changes induced by these drugs. Baseline FosB/DeltaFosB immunoreactivity (IR) in the nucleus accumbens core and pCREB IR in the prefrontal cortex (PFC) were elevated in AA rats. Morphine increased DeltaFosB-like IR more readily in the caudate-putamen of AA rats than in ANA rats. In the PFC morphine decreased pCREB IR in AA rats, but increased it in ANA rats. In addition to enhanced locomotor response, the development of place preference to morphine was enhanced in AA rats. The enhanced nicotine-induced locomotor sensitization found in AA compared with ANA rats seems to depend in addition to dopamine and DeltaFosB on other mechanisms. These findings suggest that enhanced sensitivity of AA rats to morphine is related to augmented morphine-induced expression of FosB/DeltaFosB and morphine-induced reduction of pCREB levels. Moreover, altered innate expression of FosB/DeltaFosB and pCREB in AA rats is likely to affect the sensitivity of these rats to abused drugs.

Accumbal FosB/DeltaFosB immunoreactivity and conditioned place preference in alcohol-preferring AA rats and alcohol-avoiding ANA rats treated repeatedly with cocaine.

Transcription factor DeltaFosB has been implicated in the psychomotor responses and rewarding effects of drugs of abuse. In the present study, we compared the effects of cocaine on the expression of DeltaFosB-like proteins by immunohistochemistry in striatal brain areas of alcohol-preferring (AA) and alcohol-avoiding (ANA) rats. Cocaine was administered using a previously verified treatment paradigm that sensitized the locomotor response to cocaine in AA but not in ANA rats. We also studied the rewarding effects of cocaine with a conditioned place preference (CPP) paradigm in both lines of rats. Cocaine treatment increased the FosB/DeltaFosB immunoreactivity (IR) in the nucleus accumbens of AA rats but not in ANA rats. In addition, after repeated saline injections the accumbal FosB/DeltaFosB IR was significantly greater in saline-injected AA rats than in ANA rats. In the caudate-putamen cocaine significantly increased FosB/DeltaFosB IR, but no differences were found between the rats of two lines. In the CPP experiment, AA rats treated with cocaine 2.5 mg/kg preferred the cocaine-associated compartment, in contrast to ANA rats, which did not show such a preference. In conclusion, our findings show that AA rats are more sensitive to cocaine than ANA rats, and suggest that one possible mediator for this increased sensitivity could be the increased expression of fosB-derived proteins in the nucleus accumbens of AA rats.

Survival of AA and ANA rats during lifelong ethanol exposure.

BACKGROUND: Study of the long-term effects of chronic alcohol consumption in human populations is confounded by genetic and environmental factors. METHODS: The study was intended to investigate the effects on morbidity and survival of lifetime forced ethanol consumption in male and female AA (Alko, Alcohol) and ANA (Alko, Non-Alcohol) rats. The ethanol-exposed rats had 12% ethanol as the only available fluid from 3 to 24 months of age. The control groups had water. Rats that died during the experiment and those that were killed at 24 months of age were all autopsied, and the pathologic findings were recorded. RESULTS: Lifelong ethanol consumption did not change the survival rate of the rats, and had no significant effect on the rates of any of the pathologic measures in either the AA or ANA line of rats, suggesting that this may not be a good animal model for studying the detrimental effects of chronic alcohol. An unexpected, highly significant finding was observed: the AA rats, bred for high voluntary ethanol drinking, lived much longer than the ANA rats, bred for ethanol avoidance. The death rate by 24 months in the AA line was less than one-third of that in the ANA line. This difference was found regardless of whether the animals were maintained on alcohol or water, and in both genders. The AA rats had significantly lower rates of kidney disease, benign tumors, and cardiovascular disease than the ANA animals. CONCLUSIONS: Lifelong ethanol consumption increased neither the mortality nor the morbidity of AA and ANA line of rats. Genes selected in the development of the high drinking AA line have additional effects producing rats that are healthier and living longer than the ANA rats possessing genes resulting in alcohol avoidance.