Differential involvement of anxiety and novelty preference levels on oral ethanol consumption in rats

Rationale Drug addiction is defined as a recurring cycle of intoxication, abstinence and relapse. The behavioural trait of novelty seeking is frequently observed in alcohol abusers. Moreover, converging evidence indicates that anxious individuals are also predisposed to alcohol abuse. Objectives We have analyzed the respective implication of those two behavioural factors on vulnerability to ethanol intake on rats in situations designed to reflect drug intoxication and relapse phases in humans. Methods In a general population of Wistar rats, animals were tested in both the light/dark box and the novelty preference tests. Ethanol consumption was measured in a two-bottle free-choice procedure across three successive procedures. Animals were first exposed to increasing concentrations of ethanol (2, 4, 6, 8, 10, 12 % for 8 days at each concentration). Then, the concentration of the solution was diminished from 12 to 6 %. Finally, all rats were re-exposed to 6 % ethanol after 12 days of ethanol deprivation. Results Novelty preference predicted the amount of ethanol consumed across all phases. In contrast, anxiety was associated with a quicker recovery of ethanol consumption after the concentration drop and a greater increase in ethanol consumption after deprivation. Conclusions Novelty seeking and anxiety are both but differentially implicated in predisposition to ethanol abuse. Whereas novelty seeking is related to the amount of ethanol consumed, anxiety is associated to higher ethanol consumption when ethanol concentration is decreased or after ethanol deprivation.