Age Impacts Perineuronal Net Density in the Somatosensory Genital Cortex Independently of Gonadal Steroid Hormones

A hallmark of pubertal development is the rise in gonadal hormone secretions and the subsequent onset of sexual behavior. The size of the somatosensory genital cortex increases in response to both this rise in gonadal steroid hormones and sexual experience. However, whether specific markers of brain plasticity are similarly impacted by gonadal hormones during puberty is not known. Perineuronal nets (PNNs) are specialized extracellular matrix structures that unsheathe neurons as they mature, and their maturation coincides with the closure of sensitive periods across several sensory systems. PNNs in somatosensory cortex, as an example, respond to experience-dependent plasticity. Although experience-depended changes occur in the somatosensory cortex, whether gonadal steroid hormones influence PNN development in the somatosensory cortex during puberty is not known. The current study tests the hypothesis that adolescence is a sensitive period for the effects of gonadal steroid hormones on PNN development in the somatosensory genital cortex. This hypothesis predicts that steroid hormone during adolescence, but not before or after, will significantly increase PNNs. To test this hypothesis, male and female mice were gonadectomized before puberty at 22 days of age, and systematically administering blank or steroid hormone-filled capsules before, during, and after the normal time of puberty. Specifically, males were administered 1-wk of testosterone, and females were administered 1-wk of estradiol prior to transcardial perfusion and brain removal, sectioning at 40 microns, and immunofluorescence labeling of Wisteria floribunda (WFA) to visualize PNNs. Results show that hormones and hormone timing have no effect of PNN development in the genital cortex as hormones increased equally across age for all treatment groups. This shows that despite gonadal steroid hormone release happening at the same time PNN maturation occurs, it is a different process that increases PNN density.