Co-localization of aromatase enzyme and estrogen receptor immunoreactivity in the preoptic area during reproductive aging

Immunoreactive aromatase enzyme (AROM-IR) was studied in the preoptic and septal areas of the male Japanese quail brain relative to the age-related decline in endocrine and behavioral components of reproduction. Additional analyses were conducted to determine if the co-localization of AROM-IR and estrogen receptor immunoreactivity (ER-IR) in the medial preoptic area change during aging. Young, sexually active, male quail (6 months of age) were compared to aged sexually active or inactive, male quail (36 months of age). Testis size decreased in old, sexually inactive males, similar to our previous observations. The numbers of AROM-IR neurons in the medial preoptic area (POM) and the lateral septum (LS) decreased significantly with aging and sexual activity. The number of cells that co-localized both AROM-IR and ER-IR did not differ with age. As a consequence of the age-related change in AROM-IR cells, the relative percentage of dual labelled (AROM-IR and ER-IR) and single labelled cells (AROM-IR) increased in aged males. These data provide histochemical evidence that alterations in the aromatase enzyme system in the medial preoptic area may underlie behavioral and endocrine events associated with reproductive aging.