Gonadal steroid-dependent neuronal circuitries in avian limbic and preoptic regions

In the avian limbic and preoptic region, the sexually dimorphic medial preo ptic nucleus and nucleus of the stria terminalis are characterized by the p resence of a testosterone-dependent aromatase-immunoreactive neuronal popul ation. In situ hybridization studies confirmed that testosterone is modulat ing the expression of: aromatase gene. Both nuclei are also characterized b y a sexually dimorphic, testosterone-dependent vasotocin system. Immunocyto chemical and in situ hybridization data, demonstrated that dimorphism and t estosterone-sensitivity of this system are both dependent by an embryonic o rganizational effect of the estradiol. Intracerebroventricularly injected v asotocin, has a profound inhibitory effect on the male sexual behaviour, an d immunocytochemical investigations revealed close associations among vasot ocin fibres and aromatase cell bodies. These data suggest that this neurope ptidergic system could have a key role in the circuitries controlling diffe rent aspects of male reproductive behaviour in the Japanese quail.