ABSENCE OF TOLERANCE TO THE AVERSIVE STIMULUS PROPERTIES OF ETHANOL FOLLOWING ORAL ETHANOL SELF-ADMINISTRATION

Depending on the situation, ethanol can serve as a reinforcer in one p aradigm and an aversive stimulus in another. The relationships between the two stimuli are not clear, particularly the behavioural adaptatio n following chronic ethanol exposure. We report on two experiments usi ng an oral-self administration (OSA) paradigm and a conditioned taste aversion (CTA) paradigm. Male Wistar rats were exposed to ethanol usin g either the OSA or the CTA paradigm, and the consequences were examin ed in the same groups of rats by performing the other corresponding ex periment. Thus, sensitisation or tolerance to the respective stimulus properties of ethanol would be detectable. For OSA experiments, rats w ere presented, under a free-choice setting, tap water and an ascending series of ethanol concentrations (2-10%) for up to 4 days per concent ration. The amounts of ethanol and water consumed in 23-h sessions wer e measured. For CTA, a two-bottle procedure was employed. Distinctivel y flavoured solutions (saccharin or saline) were paired with IP inject ions of either ethanol (1.5 g/kg) or saline (1 ml/kg). Tests for avers ion were made after two pairings, when both solutions were presented s imultaneously for 10 min. At low concentrations of ethanol, drinking s olution consumption was high, decreasing gradually with increasing con centrations; however, daily intake of orally self-administered ethanol remained stable. No significant differences could be established betw een the two groups tested. Ethanol preference [EtOH/EtOH + H2O] was at tenuated in rats experienced with the CTA procedure before the OSA exp eriment. Injections of ethanol produced marked CTAs, even in rats that had consumed ethanol in the OSA experiment. The absence of tolerance to the aversive stimulus effects suggests that this stimulus property may not play a significant role in the consumption of ethanol.