[Abstract Title]. - Society for Neuroscience

Poster
278. Sex Differences I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 278.3/LL24
Topic: E.01.e. Sexual differences
Support: Italian Ministry of Research Grant 2006072719_004
Title: Aromatase distribution during sheep brain development and evaluation on the sexually
dimorphic nucleus
Authors: S. GADAU, A. MURA, G. LEPORE, M. ZEDDA, B. ARRU, *V. FARINA;
Univ. Sassari, Sassari, Italy
Abstract: During foetal development, a series of crucial events may induce stable modifications
in cell number and morphology of selected brain nuclei generating specific neuronal networks.
An important step in the main process of foetal brain sexual differentiation is the aromatization
of testosterone to estradiol by P450 aromatase, being its onset and time length depending on the
length of gestation. In the foetal brain of sheep, a long-gestation species, P450 aromatase activity
starts from embryonic day E30 to E100. From this time onward, aromatase activity is evident in
a cell group of the caudal preoptic area corresponding to the sexually dimorphic nucleus (SDN)
of adults in a lot of species. As to the sheep, its presence is still controversial.
In this study, the possible distribution of P450 aromatase was assessed in the hypothalamic
preoptic area of foetal sheep brain at different stages of development (E30 to E115). In addition,
the existence of SDN has been investigated in adult sheep. Coronal sections of foetal
hypothalami were processed by immunoperoxidase technique (ABC method) employing the
following polyclonal antibodies: anti-P450 aromatase, anti-estrogen receptor (ERβ) and antiandrogen
receptor (AR). In addition, coronal sections of hypothalami from adult sheep of both
sexes were processed with the monoclonal antibody anti-calbindin, a widely considered marker
of SDN.
A high immunoreactivity was found for aromatase, ERβ and AR throughout the foetal period
under examination in different brain regions being mainly distributed in the periventricular area
where the bulk of cells were stained. Moreover, no calbindin-immunoreactive cells were seen in
hypothalamic coronal sections of adult sheep of both sexes. SDN cannot be identified in adult
sheep, neither on the basis of morphological observations, nor of calbindin immunoreactivity.
However, that species is well-characterized by the wide extension of aromatase-immunopositive
brain regions, even in comparison with species taxonomically close, such as the cow. In situ
hybridation studies are being carried out at our labs in order to confirm aromatase
immunoreactivity results.