Sex differences in cocaine-stimulated motor behavior: Disparate effects ofgonadectomy

Sex differences in biological substrates of drug use and addiction are poor ly understood. The present study investigated sexual dimorphisms in motor b ehavior following acute cocaine administration (10, 20, or 40 mg/kg, i.p.). Cocaine increased stereotypy rating, horizontal and vertical activity in b oth sexes, and effects were always greater in females than males. A populat ion analysis using data from multiple experiments indicated that horizontal activity scores were normally distributed in males but not in females. Gon adectomy induced disparate effects on cocaine-stimulated motor behavior. Po pulation analysis indicated that castrated males exhibited more horizontal activity and stereotypy than shams. Ovariectomy did not affect cocaine-stim ulated stereotypy brit did attenuate horizontal activity in a subset of rat s that had not been vaginally lavaged. In summary, gonadectomy effects were sex and behavioral topography specific and indicate that activational effe cts of gonadal hormones partially mediate the robust sex differences in coc aine-stimulated open-field behavior. [Neuropsychopharmacology 25:118-130, 2 001] (C) 2001 American College of Neuropsychopharmacology. Published by Els evier Science Inc.