Whisnant C S, Goodman R L
Department of Physiology, West Virginia University Health Sciences Center, Morgantown 26506.
Biol Reprod. 1990 Apr;42(4):656-61. doi: 10.1095/biolreprod42.4.656.
Two photoperiod-controlled neuroendocrine systems appear to suppress secretion of tonic luteinizing hormone (LH) in anestrous ewes: a steroid-independent system that decreases LH pulse frequency in ovariectomized ewes and a steroid-dependent system whereby estradiol gains the capacity to suppress LH pulse frequency in anestrus. This study was designed to test the hypothesis that serotonergic neurons inhibit LH pulse frequency in ovariectomized ewes and to examine the possible interaction of this system with the steroid-dependent inhibition of LH pulse frequency in the anestrous season. In Experiment 1, i.v. injection of serotonin receptor antagonist, methysergide, significantly increased LH pulse frequency in ovariectomized ewes during the anestrous season. In Experiment 2, we examined the effects of oral administration of parachlorophenylalanine for 5 days on the synthesis of serotonin. This treatment significantly increased LH pulse frequency in ovariectomized ewes, but had no effect on the negative feedback action of estradiol. These data support the hypothesis that a serotonergic neural system mediates the steroid-independent inhibition of LH pulse frequency in anestrous ewes and suggest that this system is not absolutely essential for the functioning of the steroid-dependent system responsible for the negative feedback action during the anestrous season.
两种受光周期控制的神经内分泌系统似乎会抑制处于乏情期母羊的促黄体生成素（LH）的分泌：一种是不依赖类固醇的系统，它会降低去卵巢母羊的LH脉冲频率；另一种是依赖类固醇的系统，在乏情期，雌二醇获得抑制LH脉冲频率的能力。本研究旨在验证5-羟色胺能神经元抑制去卵巢母羊LH脉冲频率这一假设，并研究该系统与乏情季节中依赖类固醇对LH脉冲频率的抑制作用之间可能存在的相互作用。在实验1中，静脉注射5-羟色胺受体拮抗剂麦角新碱，在乏情季节显著增加了去卵巢母羊的LH脉冲频率。在实验2中，我们研究了连续5天口服对氯苯丙氨酸对5-羟色胺合成的影响。这种处理显著增加了去卵巢母羊的LH脉冲频率，但对雌二醇的负反馈作用没有影响。这些数据支持了5-羟色胺能神经系统介导乏情期母羊中不依赖类固醇对LH脉冲频率抑制作用的假设，并表明该系统对于乏情季节中负责负反馈作用的依赖类固醇系统的功能并非绝对必要。
