Abstract

A classical (Mendelian) genetic analysis of responses to ethanol and nicotine was conducted in crosses derived from mouse lines which were selectively bred for differential duration of loss of the righting response (sleep-time) after ethanol. Dose-response curves for these mice, the long- and short-sleep mouse lines, as well as the derived F1, F2 and backcross (F1 x long-sleep and F1 x short-sleep) generations were generated for several measures of nicotine and ethanol sensitivity. Ethanol sensitivity was assessed using the sleep-time measure. Nicotine sensitivity was tested using a battery of behavioral and physiological tests which included measures of seizure activity, respiration rate, acoustic startle response, Y-maze activities (both crossing and rearing activities), heart rate and body temperature. The inheritance of sensitivities to both of these agents appears to be polygenic and inheritance can be explained primarily by additive genetic effects with some epistasis. Sensitivity to the ethanol sleep-time measure was genetically correlated with sensitivity to both nicotine-induced hypothermia and seizures; the correlation was greater between sleep-time and hypothermia. These data indicate that there is overlap in the genetic regulation of sensitivity to both ethanol and nicotine as measured by some, but not all, tests.