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

在雌性和雄性大鼠中，外侧隔(LS)对雌性特征性行为的调节都有抑制作用，如前凸和招揽行为。这种抑制机制也存在于中缝背核(DRN)的5-羟色胺能神经元。在雄性大鼠中，这种雌性性行为模式非常罕见，即使在大剂量雌激素治疗的情况下也是如此。男性女性性行为的低发生率被认为是由于LS和DRN中强烈的抑制作用所致。在本实验中，用神经内分泌学方法分析了这些抑制机制，并获得了以下结果。1.由于切断背根神经节前部腹侧可增强雄性和雌性大鼠的前凸行为，因此该核团的前腹投射参与了抑制前凸的机制。2：切断雄性大鼠内侧前脑束，诱导雌性大鼠前凸活动水平。这表明该束作为抑制前凸影响的途径具有重要意义。3.为阐明雌激素在LS和DRN抑制系统中的作用，将雌激素直接注入这两个区域，并在阈值以下剂量注射苯甲酸雌二醇的去势雌性和雄性大鼠观察到前凸。结果是，在LS而不是DRN植入雌激素促进了雌性大鼠的前凸。这一结果表明，雌激素对腰椎前凸的抑制作用是由雌激素直接释放的，而不是在背角。此外，在男性腰椎中植入雌激素对前凸没有影响。因此，雌性大鼠性行为发生率低的原因是在LS中形成了不能被雌激素直接释放的强烈抑制。

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.