Selective breeding of rats for differences in reactivity to alcohol. An approach to an animal model of alcoholism. II. Behavioral measures.

Abstract

Two lines of rats were bred for distinctly different motor responses to a subhypnotic dose of alcohol (1.5 g/kg of body wt); those most affected (MA) and those least affected (LA). Other traits which might distinguish the 2 lines were examined in a series of studies. In the 1st study blood alcohol concentrations were measured immediately after motor activity testing in the F1, F8 and F9 generations: there were no significant differences between lines or sexes. The 2nd study examined sleeping time after 2.5 or 3.0 g of alcohol/kg in F2, F5, F8 and F9 animals: in the F5, F8 and F9 generations MA rats slept 2 to 3 times longer than LA rats; sleeping time and motor activity did not correlate significantly in F9. The 3rd study tested behavior without alcohol: in F7 no differences due to line or sex were found in open-field activity; in F9 performance in the open field was similar in the lines, but females were more active in the running wheel than males, and LA rats more than MA. The 4th study examined the response of F9 rats to tests in dark and light conditions: females were more active than males in both tests; animals were more active in the open field in the dark than in the light; in the running wheel lighting made no difference but LA animals were still more active. In the 5th study, males in the 2 lines drank similar amounts of alcohol proportional to body wt when offered alcohol solutions (sweetened with 0.1% saccharin) of 5.6, 11.2 and 22.4% (wt/vol) for 12-14 days each. F9 males were given a choice of 5.6% alcohol solution and water for 49 days; no differences in percentage of daily fluid intake consumed as alcohol solution were found between lines. MA and LA rats differ in sensitivity to alcohol over a range of doses; the differences were not reflected in alcohol intake or selection. Differences in running wheel activity without alcohol may suggest a more sensitive neural apparatus in MA than in LA animals.