Effects of prior exposure on conditioned taste aversion in the rat: Androgen- and estrogen-dependent events.

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Abstract
The effects of preexposure and gonadal hormone manipulation on the extinction of a conditioned taste aversion were investigated. Male rats were given 1 prior exposure to sucrose at some selected time (days 4, 2 or 1) before a 2nd exposure (day 0) to sucrose and an LiCl injection. Controls received no prior exposure to sucrose but experienced only the sucrose+LiCl condition (day 0). Under the single exposure condition (day 0) castrated animals extinguished the aversion faster than either testosterone-treated castrated rats or sham-operated rats. Sham-operated and castrated rats that had received preexposure treatment (days 4, 2 or 1) were not distinguishable on a within-groups comparison of behavior but differed from their respective controls by exhibiting faster rates of extinction. In the testosterone-treated group only the day 4 preexposure group exhibited a faster extinction rate. Estradiol, dihydrotestosterone and testosterone were studied by using only a day 1 preexposure condition. The testosterone-treated group maintained the aversion for the longest period of time, followed by dihydrotestosterone-treated, sham, castrated and estradiol-treated groups. It appears that estradiol augments the castration effect whereas dihydrotestosterone attenuates the effect. Estradiol was administered alone or in combination with 2 different doses of dihydrotestosterone, and a day 1 preexposure condition was used. The outcome of behavior is apparently dependent on the ratio of estradiol to dihydrotestosterone, with variations in this ratio resulting in fast (estrogen effect) to slow (androgen effect) rates of extinction.