Effect of Drinking History on Reinforced and Extinction Responding in Crossed High Alcohol-Preferring Mice

Abstract

Tolerance is a diagnostic criterion for alcohol use disorder (AUD) and dependence and is often measured metabolically or behaviorally by comparing blood ethanol concentrations (BEC) or locomotor performance to an ethanol (EtOH) challenge before and after a drinking history, respectively. To explore another aspect of chronic behavioral tolerance in a family history positive (FH+) model of AUD, crossed High Alcohol Preferring (cHAP) mice were allowed to respond instrumentally for an EtOH reinforcer after either a five-week history of continuous home cage two-bottle choice (2BC) drinking or a concurrent five-week water-drinking period. Additionally, some of these animals were placed back into the operant box after home cage drinking histories to respond in extinction, allowing for the quantification of alcohol-motivated seeking alone in the absence of EtOH taking and its intoxicating effects. The results demonstrate that an alcohol history does not lead to a subsequent increase in active lever responding or inactive lever responding when compared to water-drinking controls. However, female cHAP mice with an EtOH-drinking history respond more on the inactive lever in extinction compared to water controls, suggesting that home cage EtOH history potentiates variation in responding in extinction. Overall, female mice responded more on the active lever and drank more alcohol in the reinforced condition, but again, there was not an effect of drinking history on this sex-specific effect. Together these results suggest that while female cHAPs, regardless of drinking history, are more motivated to work to drink EtOH, reinforced and non-reinforced instrumental responding are not reliable readouts for tolerance in cHAP mice compared to other endpoints such as drinking in the dark (DID) assays.