Ethanol tolerance developed during intoxicated operant performance in rats prevents subsequent ethanol-induced...

Four groups of Sprague-Dawley rats (n = 10 per group) were trained in a two-phase conditioning experiment. All rats were initially trained in an FR30 operant task (phase 1), and subsequently trained in a conditioned taste aversion (CTA) task. The groups of rats differed in their ETOH exposure. All rats received 2-week chronic exposure in phase 1. Two groups received chronic presession ETOH and, therefore, the opportunity for intoxicated practice; another group, yoked to this latter group, received postsession ETOH; the final group received presession saline injections. The presession ETOH groups were conditioned in the CTA task with either ETOH or saline; both increased their intakes of the conditioned tastant. The presession saline and the postsession ETOH groups received ETOH CTA; both developed a robust CTA. Thus, prior history of intoxicated practice under the operant task prevented the development of ETOH-induced CTA. We argue that ETOH exposure may be a necessary but not sufficient condition for tolerance to develop to the aversive attributes of ETOH.