Ethanol Reward and Aversion in Mice Bred for Sensitivity to Ethanol Withdrawal

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Abstract

The present study examined mice selectively bred for sensitivity to ethanol withdrawal for differences in the conditioned place preference (CPP) and conditioned taste aversion (CTA) paradigms. Withdrawal Seizure-Prone (WSP) and Withdrawal Seizure-Resistant (WSR) mice and High Alcohol Withdrawal (HAW) and Low Alcohol Withdrawal (LAW) mice were selectively bred for differences in chronic and acute ethanol withdrawal, respectively. For the CPP experiment, male HAW and LAW (generation 5) mice received four pairings of ethanol (2 g/kg), with a distinctive floor stimulus. On intervening days, mice received saline paired with an alternate floor type. During the preference test, all mice received an injection of saline before 60-min access to both floor types. HAW mice showed conditioned preference for the ethanol-paired floor, whereas LAW mice did not. For the CTA experiments, male HAW, LAW, WSP, and WSR mice were adapted to a 2-hr/day water restriction regimen and subsequently received ethanol injections (0, 2, 2.5, or 4 g/kg, ip) immediately after 1-hr access to a NaCl-flavored solution. Dose-dependent reductions in NaCl intake reflected the development of CTA in both HAW/LAW and WSP/WSR lines. However, a smaller magnitude of CTA was observed in WSP mice relative to WSR mice after the first ethanol-NaCl pairing. WSP/WSR mice showed similar reductions of NaCl intake on subsequent conditioning trials. Overall, these data suggest that HAW mice selectively bred for high sensitivity to acute ethanol withdrawal are more sensitive to the rewarding effects of ethanol in the CPP paradigm. This outcome is consistent with a previous study showing greater CPP in WSP mice relative to WSR mice. In the CTA paradigm, sensitivity to ethanol withdrawal in the HAW/LAW selected lines does not appear to be genetically correlated with sensitivity to the aversive properties of ethanol. However, the difference in acquisition of CTA in WSP/WSR lines suggest that some genes determining ethanol withdrawal severity may also influence initial sensitivity to ethanol's aversive effects.

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