Estrogen receptor α and vasopressin in the paraventricular nucleus of the hypothalamus in Peromyscus

The purpose of this study was to determine the presence of estrogen receptor alpha (ERα) and the relationship between neurons that express ERα and produce vasopressin (AVP) in the paraventricular nucleus of the hypothalamus (PVN) in new world mice of the genus Peromyscus. Brains were collected from male and female Peromyscus californicus, Peromyscus leucopus, Peromyscus maniculatus, and Peromyscus polionotus, and double labeled for the expression of ERα and AVP immunoreactivity (IR). The number of cells expressing ERα-IR and AVP-IR was determined in the medial and posterior region of the PVN. The results indicate that Peromyscus is the first taxonomic group reported to have ERα widely distributed in the PVN, occurring in both medial and posterior regions of the PVN. While estrogen can regulate the production of AVP, AVP and ERα were rarely colocalized. There was, however, a significant inverse relationship between the number of cells that expressed ERα-IR and the number expressing AVP-IR. There were no sex differences in the expression of ERα-IR or AVP-IR.