Large somal size is associated with the expression of galanin but not with neuronal birthdate in the sexually dimorphic male nucleus of ferret's preoptic area/anterior hypothalamus.
Using Nissl and Golgi stains, a sexually dimorphic male nucleus (MN) comprised of a cluster of large cells with large dendritic arbors has been identified in the dorsal preoptic area/anterior hypothalamus (POA/AH) of male ferrets. The MN-POA/AH is formed only in males by the action of estradiol derived from the neural aromatization of testosterone during the last quarter of a 41-day gestation. The ferret's dorsal POA/AH is also characterized by a sex difference in the expression of the neuropeptide galanin which first arises in males around embryonic day (e) 34. We asked whether the male-typical phenotype of large somal size is related to birthdate and/or the capacity of dorsal POA/AH neurons to express galanin. In experiment 1 we labeled cohorts of cells born on E20, E24, or E28 by injecting the amniotic sacs of individual fetuses with the thymidine analogue bromodeoxyuridine (BrdU). On postnatal day 20, BrdU-immunoreactive cells were visualized immunohistochemically, counterstained with cresyl violet, and their somal sizes were measured. BrdU-immunoreactive cells were significantly larger in the males' MN-POA/AH than in a comparable region of females, regardless of when they were born between E20 and E28. In experiment 2 galanin-immunoreactive cells in the dorsal POA/AH of adult ferrets were visualized immunohistochemically, and their somal sizes were measured. Somal areas of galanin-immunoreactive cells were significantly larger in the MN-POA/AH of intact, breeding, or castrated and testosterone-treated males than in the corresponding area of females. Our results suggest that cells in the males' MN-POA/AH are more likely to be larger than cells in females' corresponding region, regardless of birthdate. Finally, in adulthood the male-typical phenotype of large Nissl-stained somal areas of MN-POA/AH cells may, in part, reflect their increased galanin expression.
Park
J J
JJ
Department of Biology, Boston University, Boston, MA 02215, USA.
Patel
J H
JH
Dad
L K
LK
Tobet
S A
SA
Baum
M J
MJ
D000650:Amnion; D000818:Animals; D001973:Bromodeoxyuridine / Q000008:administration & dosage / Q000494:pharmacology; D002452:Cell Count / Q000187:drug effects; D048429:Cell Size; D004333:Drug Administration Routes; D004334:Drug Administration Schedule; D005260:Female; D005289:Ferrets; D019004:Galanin / Q000032:analysis*; D007032:Hypothalamus, Anterior / Q000737:chemistry / Q000166:cytology* / Q000254:growth & development*; D007150:Immunohistochemistry; D007267:Injections; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D010641:Phenotype; D011301:Preoptic Area / Q000737:chemistry / Q000166:cytology* / Q000254:growth & development*; D012727:Sex Characteristics; D012737:Sex Factors
D019004:Galanin; D001973:Bromodeoxyuridine