<Li> the periventricular nucleus (where somatostatin neurons are located) </Li> <Li> the ventromedial hypothalamus (which is important for sexual behavior). </Li> <P> In neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus . For instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life . </P> <Ul> <Li> If a female rat is injected once with testosterone in the first few days of postnatal life (during the "critical period" of sex - steroid influence), the hypothalamus is irreversibly masculinized; the adult rat will be incapable of generating an LH surge in response to estrogen (a characteristic of females), but will be capable of exhibiting male sexual behaviors (mounting a sexually receptive female). </Li> <Li> By contrast, a male rat castrated just after birth will be feminized, and the adult will show female sexual behavior in response to estrogen (sexual receptivity, lordosis behavior). </Li> </Ul>

Where is the hypothalamus located and what is its function