Lordosis inhibiting systems in the septum and dorsal raphe nucle-us

外隔（LS）对雌性和雄性大鼠的前倾和引诱行为等雌性特征性性行为的调节均有抑制作用。中隔背核（DRN）的5 -羟色胺能神经元也存在抑制机制。在雄性大鼠中，这种雌性性行为模式非常罕见，即使用大剂量的雌激素治疗也是如此。女性性行为在男性中的低发生率被认为是由于对LS和DRN的强烈抑制影响。本实验通过神经内分泌学方法对这些抑制机制进行分析，得到以下结果：1：由于DRN前部的腹侧切割增强了雄性和雌性大鼠的前凸行为，因此该核的前腹侧投射参与了前凸抑制机制。2：通过横断雄性大鼠内侧前脑束诱导雌性大鼠前凸活动水平。这提示了神经束作为前凸抑制途径的重要性。为了明确雌激素在LS和DRN抑制系统中的作用，我们将雌二醇直接植入这些区域，并在阉割的雌性和雄性大鼠中注射阈下剂量的苯甲酸雌二醇，观察到前倾。结果表明，雌性大鼠腰侧肌植入雌激素，而DRN未植入雌激素，可促进前凸。这表明对前凸的抑制是由雌激素直接释放的，而不是在DRN中释放的。此外，雌性激素植入雄性前凸肌对前凸无影响。由此可见，雄性大鼠雌性性行为发生率低的原因是由于雌性激素不能直接释放的LS产生了较强的抑制作用。

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.