Interference with taste familiarization by several drugs in rats

Abstract

Attenuation of conditioned taste aversion by prior exposure to the conditioned stimulus (CS) has been called “learned safety.” Injection of imipramine, chlordiazepoxide, pentobarbital, scopolamine, or penicillin after the first CS exposure interfered with learned safety. Further experiments showed that this drug effect was not due to aversiveness of the drugs, generalized neophobia, retroactive state dependence, gustatory interference, impaired memory, or overshadowing of the CS and that the drug effect could be abolished by familiarization. Conditioned suspicion due to alteration of the internal milieu was proposed as a possible mechanism of the drug effect. Such suspicion can facilitate subsequent taste aversion but is not aversive in itself. Time-course studies suggested that conditioned suspicion may be yet another form of long-delay learning.