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Aims and Methods: We have investigated proopiomelanocortin (POMC) and neuropeptide Y (NPY) gene expression in the arcuate nucleus of the hypothalamus comparing his alcohol preference (HAP) rats and low alcohol preference (LAP) rats under basal conditions using in situ hybridization histochemistry. Results: A significantly higher expression of POMC mRNA was observed in HAP rats compared with LAP rats. In contrast, no difference in NPY mRNA expression was observed between the two rat lines. Conclusions: These data suggest that an endogenous opioid system may contribute to alcohol preference in HAP/LAP rat lines. [ABSTRACT FROM AUTHOR]

— A significant difference in blood-acetaldehyde concentration was observed between high alcohol-preference (HAP) rats and low alcohol-preference (LAP) rats, newly developed different alcohol preference lines. This difference of acetaldehyde accumulation may be due to cytosolic aldehyde dehydrogenase (ALDH1) polymorphism, which has been reported previously. As the doses of ethanol we employed are higher than that of voluntary drinking, there may be little direct relationship between acetaldehyde accumulation and alcohol preference. We suggest therefore that the ALDH1 polymorphism is associated with alcohol preference in HAP/LAP lines through some other unidentified mechanism. [ABSTRACT FROM PUBLISHER]

We have investigated the effects of single administration of methamphetamine (MAP) (1.0 mg/kg, i.p.), and of combined administration of ethanol (EtOH) (2.0 g/kg, i.v.) and MAP (1.0 mg/kg, i.p.) on striatal extracellular dopamine (DA) and serotonin (5-HT) levels in chronic alcohol treated rats using a brain-microdialysis method. We used two different lines of rats with high and low alcohol preferences, (high alcohol preference rat (HAP) and low alcohol preference rat (LAP), respectively), which were chronically fed an alcohol containing liquid diet for 6 to 8 weeks. The percent change in DA and 5-HT in striatum following single administration of MAP was significantly higher in control-fed LAP than HAP. However, in the alcohol-fed group, the percent changes in DA and 5-HT were significantly elevated in the alcohol-fed HAP compared to LAP. There were no significant increases in striatal extracellular DA and 5-HT in alcohol-fed LAP. In combined administration of MAP and EtOH, extracellular DA and 5-HT levels increased slightly following EtOH administration in chronic alcohol-fed rats, especially in HAP. Dramatic increases of DA and 5-HT levels were observed in alcohol-fed HAP following EtOH and MAP administration. The percent change in DA and 5-HT in alcohol-fed HAP was further elevated to 4667.7 +/- 1095.5% and 3116.9 +/- 1162.7% of the maximal change, respectively. These percent changes ware higher than that observed with a single administration of MAP. Meanwhile, LAP were less sensitive to the influence of chronic EtOH administration and to single administration of MAP. These results demonstrate that a chronic treatment of EtOH enhances the sensitivity to MAP in a high alcohol preference rat line, when two drugs were administrated simultaneously, and that a significant difference of responsiveness to abused drugs was indicated between these two lines. It is necessary to consider the alcohol preference when investigating the interaction of alcohol and/or other abused drugs.