Ovarian hormones after postnatal day 20 reduce neuron number in the rat primary visual cortex

Joseph L. Nuñez, Jagdeep Sodhi, Janice M. Juraska

Research output: Contribution to journalArticle

Abstract

Previous work from our lab has documented a sex difference in n1euron number in the binocular region of the adult rat primary visual cortex (Oc1B), with males having 19% more neurons than females. In the present study, the role of developmental steroid hormones in the formation of this difference was explored. Male and female rats underwent neonatal hormone manipulation (female + testosterone or dihydrotestosterone; male + flutamide) followed by gonadectomy on postnatal day 20. Animals that did not undergo hormone manipulation were either gonadectomized or sham operated at day 20. Neuron number was quantified in the monocular (Oc1M) and binocular (Oc1B) subfields of the adult rat primary visual cortex using the optical disector technique. As adults, day 20 gonadectomized females, as well as females + testosterone and females + dihydrotestosterone, had significantly more neurons than intact females. There was no difference in neuron number between postnatal day 20 gonadectomized males, males + flutamide, and intact males. Also, intact males had significantly more neurons than intact females in both in Oc1M and Oc1B. It appears that ovarian steroids after day 20 are the primary cause of the lower number of neurons in the primary visual cortex of the female rat.

Original languageEnglish (US)
Pages (from-to)312-321
Number of pages10
JournalJournal of Neurobiology
Volume52
Issue number4
DOIs
StatePublished - Sep 15 2002

Keywords

  • Cerebral cortex
  • Neuron number
  • Ovarian hormones
  • Rat
  • Sexual differentiation

ASJC Scopus subject areas

  • Neuroscience(all)
  • Cellular and Molecular Neuroscience

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