Estrous cycle differences in cocaine-induced stereotypic and locomotor behaviors in Fischer rats.

This study was conducted to characterize female behavioral response to acute 'binge' pattern cocaine administration (15 mg kg(-1) i.p., three times a day, at 1 h intervals) during the different stages of the estrous cycle in Fischer rats. Cocaine administration significantly increased stereotypic behavior and locomotion in females. Animals in estrus showed significantly higher cocaine-induced stereotypic and locomotive behavioral responses than those in other stages of the cycle. Plasma levels of the cocaine metabolite benzoylecgonine during metestrus diestrus were significantly higher than during estrus and proestrus probably reflecting more rapid biotransformation of cocaine. Therefore, it is likely that the hormonal fluctuations associated with the estrous cycle modulate both cocaine metabolism and the behavioral responses to cocaine in female rats. This in turn may have important implications in gender differences in behavioral responses to cocaine.