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Abstract
The organization of neuronal cell bodies in the caudal preoptic area (POA) and rostral
anterior hypothalamic area (AH) was studied in Nissl-stained brain sections from adult
male and female ferrets. Computer-assisted image-analysis procedures were developed
to help estimate the areas of cellular density and the sizes of individual perikarya.
At the junction of the POA and AH, a bilateral dorsal-medial group of neurons was
apparent only in male ferrets (dorsal nucleus). At the same coronal level, a ventral-medial
group of neurons was apparent bilaterally in both males and females (ventral nucleus).
The mean somal area of cells in the dorsal nucleus of males was significantly greater
than the mean somal area of cells in the corresponding dorsal region of females or
in the ventral nucleus of both sexes. The dorsal nucleus was clearly discernible in
adult males regardless of their hormonal status, although cells in the dorsal nucleus
were larger in intact breeding males or gonadectomized males given testosterone, estradiol
or dihydrotestosterone than in gonadectomized males given no gonadal hormones or given
progesterone. Neither the grouping of large cells nor the steroid-induced increase
in cell size, characteristic of the male dorsal nucleus, was seen in the comparable
dorsal region of females. The sex difference in cellular organization observed in
the ferret at the junction of the POA and AH is the first difference of this type
to be seen in the POA/AH of a non-rodent mammalian species. Its identification will,
hopefully, aid in the analysis of the neural mechanisms that control various sex-specific
behaviors in this species.