Two experiments examined the effect of 5 days of passive exposure to ethanol (or water) on later self-infusion of ethanol or water via surgically implanted intragastric catheters in mouse genotypes previously shown to drink high (C57BL/6J, HAP2) or low (DBA/2J, LAP2) amounts of ethanol in home-cage continuous access two-bottle choice procedures.
Intragastric ethanol self-infusion was affected by both genotype and a history of passive ethanol exposure, with greater intakes in the high drinking genotypes and in groups that received passive exposure to ethanol.
Passive ethanol exposure also increased preference for the flavor that signaled ethanol infusion (S+), eliminating genetic differences in this measure.
The increases in ethanol intake and S+ preference induced by ethanol exposure might have been mediated jointly by development of tolerance to aversive post-absorptive ethanol effects and negative reinforcement due to alleviation of withdrawal.
Bout analyses indicated that ethanol exposure increased ethanol self-infusion by increasing the total number of daily bouts rather than by increasing bout size. These analyses also showed that DBA/2J mice infused larger ethanol bouts and a greater percentage of their total intakes in large bouts than C57BL/6J mice.
Overall, these studies suggest that the intragastric self-infusion procedure is a potentially useful new tool for studying genetic and environmental influences on excessive ethanol intake and preference in mice.
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