Research reportIndividual variation in the propensity to attribute incentive salience to a food cue: Influence of sex

- Two different outbred strains: Sprague-Dawley and Heterogeneous Stock.
- Motivational value of the cue was assessed by two measures.
- Female SD rats acquired PCA behavior slightly faster than males, but not in HS rats.
- No sex difference or any impact of estrous cycle in asymptotic PCA behavior.
- Females had more active/inactive responses in the conditioned reinforcement test.

There is considerable individual variation in the propensity of animals to attribute incentive salience to discrete reward cues, but to date most of this research has been conducted in male rats. The purpose of this study was to determine whether sex influences the propensity to attribute incentive salience to a food cue, using rats from two different outbred strains (Sprague-Dawley [SD] and Heterogeneous Stock [HS]). The motivational value of a food cue was assessed in two ways: (i) by the ability of the cue to elicit approach toward it and (ii) by its ability to act as a conditioned reinforcer. We found that female SD rats acquired Pavlovian conditioned approach behavior slightly faster than males, but no sex difference was detected in HS rats, and neither strain showed a sex difference in asymptotic performance of approach behavior. Moreover, female approach behavior did not differ across estrous cycle. Compared to males, females made more active responses during the test for conditioned reinforcement, although they made more inactive responses as well. We conclude that although there are small sex differences in performance on these tasks, these are probably not due to a notable sex difference in the propensity to attribute incentive salience to a food cue.