An Analysis of Alcohol-Concentration Preference Curves in Rats

Abstract

The present study was conducted to test alcohol preference in rats. Its main purpose was to analyze the changes occurring in some measures of alcohol preference with increasing concentrations of alcohol solution.The apparatus consisted of a metal individual cage equipped with two RICHTER type drinking bottles (in the case, of the Two-Bottle tests). One of the bottles contained water, and the other alcohol solution. Every day, the volume of each fluid consumed during a period of 23 hours was recorded. Ss were 10 male Wistar rats 130 days old.This was continued for 4 days with the concentration of alcohol solution unchanged. The same 4-day procedure was repeated for each concentration of alcohol solution, and each time the concentration went up (only ascending series were used in this study). The test session was divided into 3 sub-sessions. First, all subjects underwent the Two-Bottle test with alcohol concentration increasing from 0% to 15% (in steps of 1 %). B-group members (cf. Fig. 1-2), however, were re-tested with 08 % concentration instead of 1115%. Second, after an interval of 37 days, all subjects were tested again with the Two-Bottle test, the concentration ranging from 0% to 14% (in steps of 2%), to check the reproducibility of the results of the first session. Third, the Single-Bottle test followed the second session with a rest period fo 17 days.The main results were as follows : i) There were marked individual differences in the alcohol-concentration preference curves (Fig. 1-1). Correlation matrices were computed of the same data, and a sharp division was found between the concentration ranges 1-5% and 8-10% (Table 1-1). ii) When a sufficient interval was interposed, the same pattern of the initial test reappeared (Fig. 1-3). However, there was a general upward trend in the curves. iii) Another index for alcohol preference, the 'net' alcohol concentration, was calculated (Fig. 3). The results suggest that this measure might be a useful tool for the detection of transition to a negative preference as concentration increases. iv) There were relatively minor individual differences in the results of the Single-Bottle test (Fig. 2-1), and hence this test might be used to check rat's capacity in the alcohol metabolism at its daily life situation (Fig. 2-2).