AROMATASE-IMMUNOREACTIVE NEURONS IN THE ADULT FEMALE CHICKEN BRAIN DETECTED USING A SPECIFIC ANTIBODY

Estrogen formation in the brain catalysed by the cytochrome P450(arom) is required for the control of estrogen-dependent neural mechanisms r egulating reproductive behaviour. A polyclonal antibody was raised aga inst a 15-amino acid fragment of the chicken ovarian P450(arom) protei n, to localise aromatase-immunoreactive (AR-IR) cells in the adult fem ale chicken brain. Specificity of antibody reaction was established by Western blot and by inhibition of aromatase activity in homogenates o f chicken ovarian follicles determined by a radiometric assay. The AR- IR material in the brain was localised in the perikarya and some of th eir adjacent cytoplasmatic processes. Intense immunoreactivity was obs erved in the preoptic region as well as in other hypothalamic nuclei. AR-IR cells were also found in extrahypothalamic areas; in particular, in the area entorhinalis and hippocampus. These results confirm histo logically that aromatization of testosterone in the adult female chick en brain occurs in preoptic nuclei closely associated with the regulat ion of reproductive behaviour. The mapping of AR-IR cells in the femal e chicken brain now allows study of its regulation under different phy siological and environmental conditions, and its relation to classic t arget areas expressing estrogen receptors.