Links between intake of ethanol and nicotine and reward-related mechanisms

Abstract

1. Examination was made of the effects of housing conditions on the preference of mice for dilute ethanol or water in a two-bottle choice. Isolating mice from groups of five after 10 days significantly increased their ethanol preference, compared to mice remaining group- housed or mice accustomed to single housing.2. The effects of sucrose choice, followed by ethanol administration, were examined on behaviour on the plus maze, to determine whether the use of sucrose as a "comparison” solution altered behaviour. It was found that behaviour did not vary significantly with the level of mean daily voluntary sucrose consumption. Ethanol decreased anxiety-related behaviours of mice independent of their level of daily sucrose consumption.3. Dilute nicotine was offered to mice in a two-bottle choice test. The effect of subsequent administration of ethanol was examined on behaviour on the plus maze. Ethanol exerted some behavioural effects indicative of decreased anxiety after nicotine choice, but a wider range of these behaviours were seen in control mice (water drinkers.)4. The effects of offering dilute nicotine, dilute ethanol, or a mixture of the two, in a chronic two-bottle choice paradigm, were measured. The mean daily ethanol intake of mice with and without the addition of nicotine to the drinking solution did not significantly differ. However, the mean daily intake of nicotine alone was significantly lower than the intake of nicotine where ethanol was added to the solution. All mice were exposed to the elevated plus-maze twice: once whilst in withdrawal and once when not in withdrawal. Plus-maze results indicated that withdrawal from both chronic ethanol and nicotine simultaneously showed a wider range of anxiety-indicative behaviours than withdrawing from chronic ethanol alone.5. Alterations were made to the conditioned place preference paradigm but it did not prove possible to obtain conditioned preference to morphine within the time available.