Test for oral and postingestional factors mediating differential acceptability of morphine, methamphetamine, and chlordiazepoxide drinking solutions.

The relative degrees to which aversive oral (presumably gustatory) and postingestional variables attenuate the voluntary drinking of morphine, methamphetamine, and chlordiazepoxide solutions by rats were assessed by comparing immediate acceptability with subsequent acceptability. Results indicated that morphine solutions (0.01--0.05%) are avoided primarily because of unpalatability, while methamphetamine (0.005--0.02%) and chlordiazepoxide solutions (0.02--0.08%) are avoided primarily because of aversive postingestional effects.