|Budget Amount *help
¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
The lateral septum (LS) exerts an inhibitory influence in regulation of female characteristic sexual behavior, such as lordosis and soliciting behavior in both female and male rats. The inhibitory mechanism also exist in the serotonergic neurons in the dorsal raphe nucleus (DRN). In male rats, these female sexual behavioral patterns are very rare, even when treated with large doses of estrogen. The low incidence of female sexual behavior in males is thought to be cased by strong inhibitory influences in the LS and DRN.In this experiment, these inhibitory mechanisms have been analyzed by neuroendocrinological methods and following results were obtained. 1 : Since the ventral cut of the anterior part of the DRN enhanced lordotic behavior in both male and female rats, anteroventral projections of this nucleus are involved in lordosis inhibitory mechanisms. 2 : Female levels of lordotic activity was induced by transection of the medial forebrain bundle in male rats. This suggests an importance of the bundle as a pathway for lordosis inhibiting influence. 3 : To clarify the role of estrogen in the inhibitory systems of the LS and DRN, estradiol was implanted directly in these areas and lordosis was observed in subthreshold doses of estradiol benzoate-injected castrated female and male rats. As a result, estrogen implanted in the LS butnot in the DRN facilitated lordosis in female rats. This result indicates that the inhibition for lordosis in the LS is released directly by estrogen but not in the DRN.Furthermore, implantation of estrogen into the LS in males had no effect on lordosis. Thus, the reason of low incidence of female sexual behavior in male rats is the development of strong inhibition in the LS which can not be released directly by estrogen.