Estrogen (E) regulates a variety of male sociosexual behaviors. We hypothesize that there is a relationship between the distribution of estrogen receptor alpha (ERα) and the degree of male social behavior. To test this hypothesis, ERα immunoreactivity (IR) was compared in prairie voles (Microtus ochrogaster) from Illinois (IL), which are highly social, and Kansas (KN), which are less social. The expression of androgen receptors (AR) in males also was compared between populations. The expression of ERα and AR were compared in brains from KN and IL males and females using immunocytochemistry (ICC). There were significant intrapopulational differences, with males expressing less ERα-IR than females in the medial preoptic area, ventromedial nucleus, ventrolateral portion of the hypothalamus, and bed nucleus of the stria terminalis (BST). IL males also displayed less ERα-IR in the medial amygdala (MeA) than IL females. While IL males expressed significantly less ERα-IR in the BST and MeA than KN males, there was no difference in AR-IR. Differences in the pattern of ERα-IR between KN and IL males were behaviorally relevant, as low levels of testosterone (T) were more effective in restoring sexual activity in castrated KN males than IL males. The lack of difference in AR combined with lower expression of ERα-IR in IL males suggests that behavioral differences in response to T are associated with aromatization of T to E and that reduced sensitivity to E may facilitate prosocial behavior in males.
Bibliographical noteFunding Information:
We wish to thank Dr. C. Sue Carter, Dr. Kristin Kramer and Nancy Cushing for their critical review of this manuscript, and Natalie Synder for her help with the ICC. We thank Dr. Norm Slade and his graduate students for supplying the original wild stock of KN prairie voles. Finally, we thank Narby Thompson and the many students who provided care and support for the animals used in this study. This work was supported by grants from NIH MH 01992 (cosponsored by NIHCD), HD 38490 BSC and NIH ND 11111 GEH, support was also provide by NIH MH 01050.
- Estrogen receptor alpha
- Mating strategy
- Neural basis of behavior
- Prairie vole
- Social behavior