Effects of Ethanol Cocktailon Startle in Selectively Bred Rats

Abstract

Alcohol is widely used in society. Understanding its effects on the body and emotions and why people drink is important. Alcohol research with people is difficult, so rats are useful models. Like people, rats drink little plain alcohol but will drink more of a sweetened cocktail. Also like people, rats vary in alcohol intake and anxiety. The present study explored the effects of alcohol on anxiety in Occidental Low Saccharin (LoS) and High Saccharin (HiS) rats and Outbred rats. In prior research, HiS rats drank more alcohol and startled less than LoS rats; effects of alcohol have not been compared. Anxiety and its modulation by alcohol and distracting stimuli were measured as startle amplitude. Startle, a defensive reflex found in diverse species, is affected by variables such as drugs, prior stress, where and when it occurs, and genetics. Of interest here is that startle amplitude is positively related to anxiety. Also of interest is prepulse inhibition (PPI), a measure of sensory gating. In two similar experiments, rats drank a sucrose, vanilla, and ethanol (0-10%) cocktail; startle was measured after the 0% and 10% cocktail. Predictions were that (1) LoS > Outbred > HiS for startle amplitude and (2) alcohol would reduce startle most among HiS rats. These predictions were not confirmed. More sensitive tests of the hypotheses with procedures to increase blood alcohol levels prior to startle testing would be worthwhile.