Sex difference and steroidal stimulation of galanin immunoreactivity in the ferret's dorsal preoptic area/anterior hypothalamus

Abstract

A sexually dimorphic male nucleus (MN) is seen in Nissl-stained sections from the dorsal preoptic area/anterior hypothalamus (dPOA/AH) of male, but not female, ferrets. We used immunohistochemical methods to determine whether particular neuropeptides are found in cells of the MN. A sexually dimorphic cluster of galanin-immunoreactive (IR) cells was found in the dPOA/AH of ferrets killed either on embryonic day (E) 38 or in adulthood. Significantly more galanin-IR cells were distributed in the MN and in other subregions of the dPOA/AH of intact breeding males than estrous females. The density of galanin-IR cells in the dPOA/AH was significantly reduced in adult males by castration and restored to the level of intact breeding males by daily injections of testosterone propionate (TP) for 5 weeks. The same TP treatment failed to augment the density of galanin-IR cells in the dPOA/AH of adult, ovariectomized females. Computer-assisted image analysis and grid-crossing analysis showed that the area and the number of galanin-IR fibers in the dPOA/AH were significantly greater in adult females than in males, regardless of subjects' concurrent steroidal condition. A cluster of galanin-IR cells was present in the dPOA/AH of males, but not females, killed on either E34 or E38. Administration of TP between E28 and E37 significantly increased the density of galanin-IR cells in the dPOA/AH of females killed on E38, up to the level seen in control males. The results suggest that the capacity of cells located in the dPOA/AH to express galanin after adult steroid exposure is sexually differentiated by the fetal action of testosterone, or its metabolite, estradiol, in males.

Galanin neurons in the intermediate nucleus (InM) of the human hypothalamus in relation to sex, age, and gender identity

“…The function of galanin neurons in the human InM is not known, but animal experiments suggest that this area and its galanin neurons in particular may be involved in sexual and reproductive behavior (Swaab, 2003, 2004a). In the ferret the medial preoptic galanin neurons are activated during mating (Bakker et al, 2002), and the galanin production of the InM neurons of the ferret is activated by testosterone (Park et al, 1997). The SDN‐POA size in rats is positively correlated with the frequency of masculine sexual behavior, as well as with male preference for a female over a male (Houtsmuller et al, 1994).…”

“…In the preoptic area of the ferret, a sexually dimorphic cell group was found that contained more galanin neurons in males than in females. The density of galanin neurons was reduced by castration and restored by testosterone treatment (Park et al, 1997). In the rat, large numbers of galanin neurons were found in the medial preoptic area, which decreased following gonadectomy in males and increased again after administration of either testosterone or estrogens in both sexes (Bloch et al, 1993, 1998).…”

Sleep and Human Aging

“…Testosterone has been proposed to underlie the sex differences in atrophy associated with galanin-expressing neurons within the preoptic hypothalamic area (Garcia-Falgueras et al, 2011). In rodent studies, galanin neuronal density is reduced by castration and restored with testosterone treatment (Park et al, 1997). In human studies, both castrated men and male to female transsexual individuals have galanin-expressing neurons within the preoptic area of the hypothalamus reduced to a number similar to that observed in women (Garcia-Falgueras et al, 2011).…”

Sexually Dimorphic Activation of Galanin Neurones in the Ferret's Dorsomedial Preoptic Area/Anterior Hypothalamus after Mating

“…Using immunocytochemical methods, the neurochemical phenotype of neurones in the ferret's sexually dimorphic dmPOA/AH was determined (6). A striking sex difference was found in the distribution of galanin‐immunoreactive (IR) neurones: gonadally intact males in breeding condition had many more galanin‐IR neurones in the dmPOA/AH than gonadally intact, oestrous females.…”

“…The sex difference in galanin‐IR in the dmPOA/AH did not result from sex differences in circulating testosterone levels; treatment with high doses of testosterone propionate (5 mg/kg) failed to augment the number of galanin‐IR neurones in adult, ovo‐hysterectomized females. However, prenatal treatment with testosterone propionate significantly increased numbers of galanin‐IR neurones in the dmPOA/AH of females up to the level seen in males, implying that the capacity of these dmPOA/AH cells to express galanin is sexually differentiated prenatally by testosterone and/or its oestrogenic metabolite in male ferrets (6). Sex differences in the distribution of galanin neurones in the POA/AH have also been described for several other species, including the teleost fish sailfin molly (7), the goldfish (8), the mouse (9), the rat (10) and the gerbil (11).…”