[Stress and alcohol: research with experimental animals].

Research on the interaction of ethanol and stress with experimental animals are briefly reviewed. There might be the two aspects of the interaction of stress and ethanol, i.e., how stress affects ethanol ingestion and response to ethanol, and how ethanol modifies stress response. In general, stress increases ingestion of ethanol in animals exposed to various stresses including electric shock, immobilization and psychological or emotional stresses, wherein the psychological or emotional factors were predominantly involved. However, in most cases, ethanol ingestion is increased after release from stress not during exposure to stress. A variety of stressful stimuli caused marked increases in the neurotransmitter release in many brain regions. Immobilization stress increased noradrenaline release in the extended brain regions in rats. These increases were significantly attenuated by pretreatment with ethanol in the rat amygdala and locus coeruleus, but not in the hypothalamus, although ethanol by itself increased noradrenaline release in the hypothalamus. Further, psychological stress, wherein the rats were given no electrical shock, but exposed to the emotional responses such as struggling, vocalization, jumping and defecation shown by the other electrically-shocked rats, increased noradrenaline release preferentially in the hypothalamus, amygdala and locus coeruleus. Among the former two regions, stress-induced increases in noradrenaline release were significantly attenuated by ethanol in the amygdala, but not in the hypothalamus. Together with the finding that increases, in noradrenaline release are closely related to the provocation of anxiety and/or fear, ethanol, in part, reduced tension, as mentioned in the tension reduction hypothesis, by attenuating stress-induced increases in noradrenaline release in the amygdala and locus coeruleus. Moreover, ethanol, administered i.p. and directly through the microdialysis probe, increased dopamine release in the nucleus accumbens assessed by in vivo microdialysis, similarly as addictive drugs such as amphetamine did. This might be, in part, neurochemical basis for motivation of repeated drinking of ethanol.