Coexistence of the stigmoid body and estrogen receptor in some neuronal groups involved in rat reproductive functions.

Abstract

Recent immunohistochemical studies have suggested that the forebrain distribution of stigmoid bodies, marked by an antibody against placental aromatase-associated antigen X-P2 (PAX), overlaps with that of the common binding sites of androgen and estrogen. In the present light- and electron-microscopy study the coexistence of stigmoid bodies and estrogen receptors (EsR) is immunohistochemically examined and quantitatively analyzed in the medial preoptic region, part of the bed nucleus of the stria terminalis and part of the medial amygdaloid nucleus of young female rats. Light microscopy with double immunostaining for PAX and EsR in all three regions indicates that 75-84% of the total of PAX-immunoreactive stigmoid structures are present in neurons which also contain EsR-immunoreactive nuclei, and that 75-78% of EsR-immunoreactive neurons contain PAX-immunoreactive inclusions. Electron microscopic analysis confirms that 70-80% of stigmoid body-containing neurons have EsR-immunoreactive nuclei. These results indicate that the majority of the stigmoid bodies and EsRs intimately coexist, strongly suggesting a functional interrelationship in brain regions which are involved in rat reproductive functions. Stigmoid bodies may play a role in subneuronal EsR mechanisms associated with aromatization in these sex steroid targets in rat brain.