Anxiety: a potential predictor of vulnerability to the initiation of ethanol self-administration in rats

Abstract

Anxiolytic effects of ethanol have been proposed to be important factors in the initiation of ethanol consumption. To examine this hypothesis, drug-naive Wistar rats were tested in the elevated plus-maze to determine their initial level of anxiety. Based on their response, we separated the animals into anxious and non-anxious groups. After that, animals went through an oral ethanol self-administration procedure. Rats that were initially classified as anxious showed a significantly (P < 0.01) higher intake and preference for ethanol during the initiation phase of the voluntary drinking procedure than non-anxious animals. In another experiment, intraperitoneal (IP) injections of ethanol (0.5-1.5 g/kg) produced dose-dependent anxiolytic effects in rats when tested in the elevated plus-maze procedure. Blood ethanol levels following IP injections during the plus-maze test were similar to those reached during the oral ethanol self-administration procedure, which shows that the rats indeed drank sufficient amounts of ethanol to experience its anxiolytic effects. These findings indicate that the basal level of anxiety plays an important role in vulnerability to alcohol drinking.

Local 5,7-Dihydroxytryptamine Lesions of Rat Amygdala Release of Punished Drinking, Unaffected Plus-Maze Behavior and Ethanol Consumption

“…Thus, modulatory effect of central serotonin on ethanol intake are likely to be mediated by brain structures other than the amygdala. Furthermore, basal levels of experimental anxiety, as approached by the elevated plus-maze, have been reported to predict alcohol preference (Spanagel et al 1995), and decreased voluntary ethanol consumption was observed in central amygdala lesioned rats, a treatment which produces anxiolyticlike effects (Möller et al 1997). Since both plus-maze behavior and ethanol preference were unchanged by our 5,7-DHT lesions, while direct lesions of the central nucleus have been shown to affect both these behaviors, we find here further support for a conclusion that central nucleus function is not a major regulatory target for the serotonergic input to the amygdala.…”

“…A two bottle, free choice procedure was used (Spanagel et al 1995). Animals were placed in single cages, and two bottles containing water or increasing concentrations of ethanol were made available continuously as a free choice of the animal.…”

Why We Like to Drink: A Functional Magnetic Resonance Imaging Study of the Rewarding and Anxiolytic Effects of Alcohol

“…Alcohol induces euphoria, relaxation, and disinhibition while reducing stress and anxiety. Consistent with human self-report, animal studies also suggest that alcohol produces a rewarding as well as an anxiolytic effect (Coop et al, 1990;Blanchard et al, 1993;Spanagel et al, 1995;Da Silva et al, 2005). Although its euphoric and stress-reducing effects have been known for centuries and are intuitively understood, how alcohol changes the function of human brain circuits has been explored only sparingly.…”

Experimental anxiety and the reinforcing effects of ethanol in rats

“…Moreover, basic studies on labora-tory animals attempting to validate the tension-reduction hypothesis have produced conflicting results. For example, in heterogeneous populations of Wistar rats, high baseline levels of experimental anxiety have been reported to predict high voluntary EtOH self-administration (14), whereas more contradictory results have been reported with rat lines bred for EtOH preference (15,16). Since little is known about the possible interaction between experimental anxiety and the effects of alcohol, in the present study we investigated the relationship between different levels of anxiety and the reinforcing effects of EtOH in rats.…”