Androgen receptors are required for full masculinization of the ventromedial hypothalamus (VMH) in rats - PubMed (original) (raw)

Androgen receptors are required for full masculinization of the ventromedial hypothalamus (VMH) in rats

Brittany N Dugger et al. Horm Behav. 2007 Feb.

Abstract

The ventromedial hypothalamus (VMH) is one of several sexually dimorphic nuclei that regulate mating behavior, and is rich in steroid hormone receptors and aromatase activity. We looked at the contribution of the androgen receptor (AR) to the volume of the VMH in rats by measuring each of the four subdivisions of the VMH in 90 day old male, female, and XY male rats carrying a mutant AR allele (tfm), which renders animals largely unresponsive to androgens. Confirming published reports, total VMH volume was greater in wild-type males than in females (P<0.01). The mean total volume of the VMH in TFM males was intermediate, but not significantly different from either females or males (Ps>0.10). The sex difference in VMH volume was primarily accounted for by the ventrolateral subdivision (VMHvl), which in both females and TFM males was significantly smaller than in wild-type males (Ps<0.005). There was no significant sex difference in the volume of the other three subdivisions of the VMH. Neuronal somata were larger in males than females in VMHvl, central VMH (VMHc) and the dorsomedial VMH (VMHdm), with TFM males having feminine neuronal somata in the VMHdm and VMHc. These data suggest that AR plays a role during sexual differentiation of the VMH, imparting its greatest effect in the VMHvl. ARs may regulate aromatase expression or activity to affect estrogen receptor activation, or may act independently of estrogen receptors to influence VMH morphology.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Thionin-stained 40µm coronal section taken at two different rostrocaudal levels of the VMH of an adult WT male. (Top) Rostral most appearance of the anterior portion (A) (Bottom) Further caudally in the same material showing the Dorsomedial, (DM) Central (C), and the Ventrolateral (VL) portions of the VMH appear. The dashed lines separate the divisions. 3V = Third ventricle.

Figure 2

Figure 2

Mean (± SEM) total (bilateral) volume of the VMH in adult TFM male, WT male and female rats. VMH volume is significantly greater in WT males than in females. VMH volume in TFM males is intermediate and not significantly different from WT males or females. * P < 0.02.

Figure 3

Figure 3

Mean (± SEM) bilateral volume of the four subdivisions of the VMH in adult TFM male rats compared with WT male and female littermates. Volume is significantly greater in WT males than in females only in the VMHvl. This subdivision is also larger in WT males than in TFM males. TFM males did not significantly differ from females in any of these measures. * P < 0.01.

Figure 4

Figure 4

Mean (± SEM) cross-sectional area of neuronal somata in the VMHa, VMHvl, VMHc, and the VMHdm in adult TFM male rats and WT male and female littermates. Neuronal somata are larger in males than females in the VMHvl, VMHc and the VMHdm. TFM males have significantly smaller somata than their WT male littermates in the VMHdm, and marginally smaller somata in the VMHvl and VMHc. * P < 0.05.

Similar articles

Cited by

References

    1. Beach FA, Buehler MG. Male rats with inherited insensitivity to androgen show reduced sexual behavior. Endocrinology. 1977;100(1):197–200. - PubMed
    1. Christensen LW, Nance DM, Gorski RA. Effects of hypothalamic and preoptic lesions on reproductive behavior in male rats. Brain Res Bull. 1977;2(2):137–41. - PubMed
    1. Cooke BM, Breedlove SM, Jordan CL. Both estrogen receptors and androgen receptors contribute to testosterone-induced changes in the morphology of the medial amygdala and sexual arousal in male rats. Horm Behav. 2003;43(2):336–46. - PubMed
    1. Devidze N, Mong JA, Jasnow AM, Kow LM, Pfaff DW. Sex and estrogenic effects on coexpression of mRNAs in single ventromedial hypothalamic neurons. Proc Natl Acad Sci U S A. 2005;102(40):14446–51. - PMC - PubMed
    1. Etgen AM, Morales JC. Somatosensory stimuli evoke norepinephrine release in the anterior ventromedial hypothalamus of sexually receptive female rats. J Neuroendocrinol. 2002;14(3):213–8. - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources