Abstract
Immature male rats (26-29 days and 34-36 days of age) and mature male rats (150-210 days of age) were electrically stimulated through chronically implanted electordes, and serum and pituitary concentrations of LH, FSH and prolactin were measured by radioimmunoassay. In mature male rats, stimulation of the medial basal prechiasmatic area (PVA), which showed a significant facilitatory effect on LH and prolactin release in the female, also induced an increase of serum LH and a relatively increased concentration of prolactin in serum. Stimulation of the medial preoptic area (MPO), medial and lateral parts of the amygdala (AMYG) induced a slight increase in serum concentration of LH. These results indicate that there is no sexual difference in the ability to induce LH release in the PVA and MPO. But the effect of AMYG stimulation is quite difficult to be explained, because it was observed in the present experiment that the stimulation in acute preparation had no effect on LH release. Dorsal hippocampus exerted an inhibitory effect on FSH secretion in immature rats. Immature male AMYG stimulation decreased pituitary concentrations of LH and FSH, in contrast to the immature female, which was indicative of the existence of sexual difference in the same area. All the brain areas examined except the PVA decreased serum concentration of prolactin following the stimulation in mature rats, but in immature rats all the areas examined showed no effect and rather facilitated it.
