Ethanol-induced analgesia in rats selectively bred for ethanol sensitivity.

Two rat lines selectively bred for ethanol-induced depression of locomotor activity were studied for ethanol-induced analgesia. The effects of ethanol on startle amplitude, extent of overt movements and incidence of audible vocalizations in response to intermittent, noncontingent foot shock. All three responses were dose-dependently depressed by ethanol (0.66 to 2.0 g/kg, IP), and to greater extent in the "most affected" line (MA) than in "least affected" (LA) rats. Ethanol-induced response decrements were reinstated at higher shock intensities, indicating a sensory (i.e., analgesic) rather than a motoric or analgesic basis for these effects. Genes which influence ethanol's motoric effects might, in part, influence sensitivity to its sensory effects.