Estrogen/progesterone treatment in adulthood affects the size of several components of the medial preoptic area in the male rat

Abstract

The results of preliminary studies suggested that steroid and/or propylthiouracil (PTU) treatment of adult gonadectomized (Gxd) male rats significantly reduced the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA). Therefore, we designed a study to examine this effect in detail. Groups of adult rats were sham Gxd (intact) or Gxd, then treated with multiple injections of oil (males and females), or estrogen and progesterone (males). Gonadectomized estrogen/progesterone-treated males had a significantly smaller SDN-POA volume, smaller volume of the medial division of the medial preoptic nucleus (MPNm), smaller volume of the anteroventral MPNm (MPNav), and larger volume of the anteroventral periventricular nucleus (AVPv). The volume of the central division of the medial preoptic nucleus (MPNc) or of the suprachiasmatic nucleus was not affected. There were no differences between Gxd estrogen/progesterone-treated males vs the group that received PTU as well, indicating that the PTU treatment was unnecessary. The reduced volume of the SDN-POA was due to a reduced volume of the MPNav and of the portion of the SDN-POA located within the MPNm-exclusive of the MPNav and MPNc. In conclusion, estrogen/progesterone treatment in adulthood caused significant changes in the volume of several medial preoptic structures in two separate groups of Gxd males. Because the steroids produced no significant effects in intact males, testicular hormones appear to "protect" these structures from the effects of the estrogen/progesterone treatment.

Topography in the preoptic region: Differential regulation of appetitive and consummatory male sexual behaviors

“…Theses lateral cells therefore tend to be larger in males than in females [102] since males on average have higher circulating concentrations of testosterone in the blood [18]. The volume of the entire POM and the size of neurons in the lateral part of this nucleus thus provide a clear morphological signature of testosterone action in the brain contrary to what is observed for sexually dimorphic brain areas in the preoptic region in other species such as the SDN-POA of rats [11,73,143] but similar to observations reported concerning the gerbil SDA [52,53,55] or the rat MPN [41,42]. Interestingly, the effects of testosterone on the neuronal size are more pronounced in the lateral part of the POM than in the medial part of the nucleus adjacent to the third ventricle [102].…”

Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure

“…hypothalamus (20) of adult gonadectomized male rats, cross-sex hormone treatment (consisting of combined estrogen/progesterone treatment) resulted in significant volume decreases towards female proportions. In addition, in the adult female canary, testosterone triggered the growth of brain vocal control nuclei towards male proportions (21).…”

Neurobehavioral effects of dietary soy phytoestrogens

“…Increased awareness and understanding of brain plasticity (and behavior) is evolving with the advancements in technology and exchange of scientific information [2,15,18,27,33,40,43,45,47,51,62,71,78,81,96,97,104,112,114,116,123,127]. Since all commercially available rodent diets use soy as the main source of protein in their formulations, it is intriguing to consider the possible impact dietary phytoes- …”