Pubertal hormones mediate sex differences in levels of myelin basic protein in the orbitofrontal cortex of adult rats.

Previous work from our lab revealed that adult female rats have increased levels of myelin basic protein (MBP), a marker for myelination, in the orbitofrontal cortex (OFC) as compared to adult males. The goal of the present study was to determine the role of gonadal hormones, acting either in adulthood or at puberty, in the development of an adult sex difference in OFC levels of MBP. In an initial experiment, we replicated our previous results demonstrating that gonadally intact female rats have increased levels of MBP in the OFC as compared to males. In a second experiment, gonadectomy in adulthood did not alter MBP levels in rats of either sex. In a third experiment, gonadectomy immediately prior to pubertal onset resulted in significant reduction of levels of MBP in adult females but not males. This reduction eliminated the sex difference in adult MBP levels in the OFC. These results reveal puberty to be an organizational time point for a sex difference in the OFC of adult rats in levels of a marker of myelination. This neuroanatomical difference may contribute to observed sex differences in OFC-associated behaviors including in inhibitory control.