The interstitial nuclei of the human anterior hypothalamus: an investigation of sexual variation in volume and cell size, number and density

The four interstitial nuclei of the anterior hypothalamus (INAH) have been considered as candidate human nuclei for homology with the much studied sex ually dimorphic nucleus of the preoptic area of the rat. Assessment of the INAH for sexual dimorphism has produced discrepant results. This study repo rts the first systematic examination of all four INAH in the human for sexu al variation in volume, neuronal number and neuronal size. Serial Nissl-sta ined coronal sections through the medial preoptic area and anterior hypotha lamus were examined from 18 males and 20 females who died between the ages of 17 and 65 without evidence of hypothalamic pathology or infection with t he human immunodeficiency virus. A computer-assisted image-analysis system and commercial stereology software package were employed to assess total vo lume, neuronal number and mean neuronal size for each INAH. INAH3 occupied a significantly greater volume and contained significantly more neurons in males than in females. No sex differences in volume were detected for any o f the other INAH. No sexual variation in neuronal size or packing density w as observed in any nucleus. The present data corroborate two previous repor ts of sexual dimorphism of INAH3 but provide no support for previous report s of sexual variation in other INAH. (C) 2000 Elsevier Science B.V. All rig hts reserved.