Partial demasculinization of several brain regions in adult male (XY) rats with a dysfunctional androgen receptor gene

John A. Morris, Cynthia L. Jordan, Brittany Dugger, S. Marc Breedlove

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

The adult rat posterodorsal medial amygdala (MePD) is sexually dimorphic in regional volume and neuronal soma size, both of which are larger in males than in females. This sexual dimorphism is entirely dependent on adult circulating levels of testicular androgens, and both androgen and estrogen treatment can masculinize MePD structure. We examined male rats that are rendered androgen-insensitive by the testicular feminization mutation (tfm) of the androgen receptor (AR) gene to determine how a dysfunctional AR affects this and other brain sexual dimorphisms. In adult wild-type rats, the MePD in males had a greater regional volume, rostrocaudal extent, and soma size than in females. In genetic males, defective ARs affected some but not all of these indices: MePD volume and soma size in tfm males were intermediate between those of wild-type males and females, but the rostrocaudal extent of the MePD was unaffected by the mutation, being as great in tfm males as in wild-type males. Regional volume and soma size in the suprachiasmatic nucleus was reduced in tfm males compared with wild-type males, suggesting that AR normally affects this region in male rats. Interestingly, whereas volume of the sexually dimorphic nucleus of the preoptic area was unaffected by the tfm allele, soma size in this region was reduced in tfm males compared with wild-type males. Although estrogen receptor activation has been shown to be vital for masculinization of the rodent brain, our results indicate that ARs also contribute to this process in several brain regions.

Original languageEnglish (US)
Pages (from-to)217-226
Number of pages10
JournalJournal of Comparative Neurology
Volume487
Issue number2
DOIs
StatePublished - Jun 27 2005
Externally publishedYes

Keywords

  • Androgen insensitivity
  • Medial amygdala
  • Sexual differentiation
  • Sexually dimorphic nucleus of the preoptic area
  • Suprachiasmatic nucleus
  • Tfm

ASJC Scopus subject areas

  • Neuroscience(all)

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