A simple drinking test for measuring the effects of ethanol on the central nervous system

An objective behavioral test is described for determining different degrees of alcohol intoxication in rats and other small laboratory animals. It is based on a measure of the length of time taken for a water-deprived rat to drink (standing upright) following the administration of a challenge dose of ethanol. The differential effects on drinking impairment of various doses of ethanol IP were examined in either the same (group A) or different (group B) animals. The test was shown to be sensitive to dose differences as small as 0.25 g/kg and to be applicable over a wide range of doses (1–4 g/kg). Lower (0.5 g/kg) or higher doses (4.5 and 5.0 g/kg) were, respectively, either ineffective or generated relatively higher latency scores than those obtained with the intermediate range of doses. The dose-response curve thus showed two rectilinear segments; regression coefficients were 154 and 183 min/g/kg^-1 in the dose range up to 2.5 and up to 4.0 g/kg for groups A and B, respectively, 431 min/g/kg^-1 for doses greater than 4.0 g/kg (group B). Blood alcohol levels measured at the onset of drinking did not differ significantly as a function of dose, between 1.0 and 4.0 g/kg (mean 0.864±0.070 mg/ml), but were higher compared to those observed with doses of 4.5 and 5.0 g/kg (0.281±0.180 mg/ml). The applicability of the drinking test to measures of initial and acquired tolerance toward drug effects is discussed.