Loss of flexibility in alcohol-taking rats: promoting factors.

Alcohol consumption in humans can move from a flexible pattern of intake to an inflexible (addictive) one. Several endogenous and exogenous factors are discussed to be involved in this transition. The purpose of this study was to examine factors that might promote the development of inflexibility. Over a period of 52 weeks (long-term) rats had continuously free choice between differently concentrated alcohol solutions and tap water (four-bottle paradigm). After 4 months of alcohol deprivation, a retest with free choice of alcohol was performed. Bitter-taste conditions were used to test the flexibility of alcohol taking. In the retest alcohol-experienced rats revealed a much higher alcohol intake than previously alcohol-naive ones. Part of the alcohol-experienced animals showed impairment of flexibility in alcohol taking. During long-term choice, some groups were submitted to experimental interventions that might affect addiction development (stress, withdrawal, limited access, adverse consequences). Rats with limited access to alcohol at the end of the long-term choice period took more alcohol and were less flexible in the retest than any other group. It is suggested that an unsatisfied urge for alcohol leads to impairment of control over alcohol drinking.