Strain Differences in Alcohol Preference of Guinea Pigs and Experimental Manipulation of Preference by Forced Alcohol Consumption
The study of the determinants of alcoholism, one of the most perplexing diseases of mankind, entered its most fruitful era of discovery in the laboratory of the animal researcher. A pioneering study of the determinants of alcohol consumption by Richter (1940) indicated that laboratory rats show a preference for alcohol over water beginning at 1.8 per cent ethanol (v/v) solution, and continue to prefer alcohol over water up to a 6 per cent ethanol (v/v) solution. Richter made two important contributions to alcohol research which had broader implications than the presentation of an index of alcohol consumption in rats. First, he hypothesized that the amount of alcohol consumed was determined by the nutritional needs of the organism, and, second, he pointed out that there existed a large degree of variation between the drinking habits of individual rats.
Interests in the study of alcoholism were given impetus by Williams and his co-workers (Williams, 1947; Williams, Berry & Beerstecher, 1949; Williams, 1951). They interpreted results of biochemical-genetic studies as indicating that the genetic development of each individual, as it affects metabolism and enzymatic patterns, is distinctly different from every other individual. Williams et al. (1949) dealt with alcoholism as a "genetotrophic" disease, implying an interaction between genetic and nutritional factors in the etiology of alcoholism. Individual differences in dietary needs, metabolism, and consumption were taken as confirmation of their genetotrophic hypothesis. Further support of the significance of individual differences (Segovia-Riquelme, Vitale, Hegsted, & Mardones, 1956) came from a comparison of rats on a free-choice schedule. Rats which drank 4 to 10 grams of alcohol per kilo of body weight per day were grouped as drinkers (D), and those which drank less than 1 gram per kilo of body weight per day as non-drinkers (ND). Metabolism of alcohol was measured by the radioactivity of the carbon dioxide which was collected after injections of various doses of grams of alcohol per kilo of body weight. They found no differences in oxidation rate between D and ND groups. However, they did find individual variations which led to the acceptance of the genetotrophic concept.