C57BL/6J mice will drink large amounts of, and display a highly positive preference for, morphine sulfate when it is dissolved in an aqueous solution of sodium saccharin. In identical test situations DBA/2J mice will drink very little of, and display a strong avoidance toward, the morphine-saccharin solution. This clear separation between morphine-accepting and morphine-rejecting animals within a single species combined with a quick and simple method of inducing high levels of morphine ingestion could facilitate the discovery of causal factors in opiate addiction.

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Acetaldehyde poisoning from ethanol ingestion may lead to aversion to ethanol among DBA mice but not among C57s, since the former are relatively deficient in aldehyde dehydrogenase activity. The present study paired ingestion of saccharin with a single intraperitoneal injection of one of four concentrations of ethanol for DBA/2J and C57BL/6J mice. Subjects were then given a two-bottle saccharin versus water preference test for 10 days. Substitution of saccharin for the taste of ethanol resulted in avoidance of saccharin with all concentrations of ethanol by DBAs but not by C57s, consistent with the conditioned taste aversion paradigm as a mo'del for genetically mediated ethanol avoidance.

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