The preoptic area anterior hypothalamus of different strains of mice: sex differences and development

While sex differences in neural morphology in the preoptic area/anterior hy pothalamus (POA/AH) have been demonstrated in many species, their existence in mice have been controversial. Given the increased use of transgenic and gene-disrupted mice, we characterized sex differences using Nissl stains, and the immunocytochemical location of estrogen receptor-alpha (ER-alpha) a nd galanin in the POA/AH of two widely used strains, C57BL/6 and 129SvEv, a nd a mixed strain (C57BL/6 x 129Sv); the wild-type littermates of steroidog enic factor-1 (SF-1) gene-disrupted mice. Cell grouping was not a reliable marker of sex, in adults, cells located beneath the anterior commissure (AC ) were reliably larger in females than males in 129SvEv, but not in the oth er strains. Caudally, cells in a group medial to the medial extension of th e bed nucleus of the stria terminalis (BST) were significantly larger in ma les than females in C57BL/6J and SF-1 gene-disrupted wild-types. Cell group s discernible by embryonic day (E) 18 were not sexually dimorphic for cell size in C57BL/6J mice at E18 or postnatal day (P) 4. The pattern of distrib ution of cells containing ER-alpha was similar among the strains, reduced i n the group medial to the BST; a pattern established by P0. Galanin-contain ing cells and fibers were seen from E15 to adulthood ventral to the AC. Cau dally, a smaller group ventromedial to the BST was found only in 129SvEv ad ults. Sex differences in neural morphology which develop within the POA/AH depend upon multiple factors, particularly including genetic background. (C ) 1999 Elsevier Science B.V. All rights reserved.