Sex difference in the distribution and size of glomeruli in the ferret's main olfactory bulb.

When exposed to male anal scent gland odorants in a previous study from our laboratory, the distribution of activated glomeruli in the ventral-caudal portion of the main olfactory bulb (MOB) was greater in female than in male ferrets. We asked whether this functional dimorphism corresponds to a morphological sex difference in the distribution, number, or size of glomeruli in the MOB of adult ferrets. Coronal serial sections through the rostro-caudal extent of the MOB from groups of breeding male and female ferrets were collected, and the glomeruli were visualized after staining of juxtaglomerular cells with an antiserum raised against neuronal nuclear protein. In both sexes the greatest density of glomeruli was seen in the ventral MOB; however, this dense cluster of glomeruli extended more caudally in males than in females. Also, the number of glomeruli per section across the caudal extent of the MOB and glomerular areas measured at three sites in the MOB were significantly greater in males than in females. We previously observed greater odor-induced glomerular activation in the ventral-caudal MOB of female than male ferrets. This functional sex difference was inversely correlated with the present observation that glomerular density, number and area were greater in the caudal MOB of male than female ferrets.