Reduced palatability in drug-induced taste aversion: II. Aversive and rewarding unconditioned stimuli.

Drugs of abuse are known to reduce intake of a taste conditioned stimulus (CS), a behavioral response sometimes seen as paradoxical because the same drugs also serve as rewards in other behavioral procedures. In the present study we compared patterns of intake and palatability (assessed using microstructural analysis of licking) for a standard saccharin CS paired with: lithium chloride, morphine, amphetamine, or sucrose. We found that morphine and amphetamine, like lithium-induced illness, each suppressed CS intake and caused a reduction in saccharin palatability. Sucrose, a rewarding stimulus, did not reduce the palatability of the saccharin CS. We interpret these finds as evidence that drugs of abuse induce conditioned taste aversions.