Bakker J, Kelliher K R, Baum M J
Department of Biology, Boston University, Massachusetts 02215, USA.
Biol Reprod. 2001 Apr;64(4):1100-5. doi: 10.1095/biolreprod64.4.1100.
In females of both spontaneously and induced ovulating species, pheromones from male conspecifics can directly stimulate GnRH neuronal activity, thereby inducing pituitary LH secretion and stimulating the onset of estrus. However, whether pheromones contribute to the steroid- or mating-induced preovulatory activation of GnRH neurons is less clear. Previous studies in the ferret, an induced ovulator, raised the possibility that olfactory cues contribute to the ability of genital-somatosensory stimulation to activate GnRH neurons in the mediobasal hypothalamus (MBH). In the present study the percentage of GnRH neurons colabeled with Fos-immunoreactivity (IR), used as a marker for neuronal activation, was investigated in the MBH of mated gonadectomized, estradiol-treated female ferrets in which both nares were occluded. In addition, the percentage of GnRH neurons colabeled with Fos-IR was examined in the MBH of gonadectomized, estradiol-treated female ferrets exposed to male bedding. Bilateral nares occlusion successfully blocked mating or odor-induced increments in Fos-IR in central olfactory regions, including the cortical and medial amygdala. By contrast, the percentage of GnRH neurons expressing Fos-IR did not differ between mated nares- and sham-occluded females. Exposure to male bedding alone failed to induce Fos-IR in MBH GnRH neurons. Thus, the mating-induced preovulatory activation of GnRH neurons in the female ferret's MBH appears to rely solely on genital-somatosensory as opposed to olfactory inputs.
在自发排卵和诱导排卵物种的雌性动物中，来自同种雄性的信息素可直接刺激促性腺激素释放激素（GnRH）神经元的活动，从而诱导垂体促黄体生成素（LH）的分泌并刺激发情期的开始。然而，信息素是否有助于类固醇或交配诱导的GnRH神经元排卵前激活尚不清楚。先前对诱导排卵动物雪貂的研究提出，嗅觉线索可能有助于生殖器体感刺激激活中基底下丘脑（MBH）中GnRH神经元的能力。在本研究中，在双侧鼻孔闭塞的交配去性腺、经雌二醇处理的雌性雪貂的MBH中，研究了用Fos免疫反应性（IR）共标记的GnRH神经元的百分比，Fos-IR用作神经元激活的标志物。此外，在暴露于雄性垫料的去性腺、经雌二醇处理的雌性雪貂的MBH中，检查了用Fos-IR共标记的GnRH神经元的百分比。双侧鼻孔闭塞成功阻断了包括皮质和内侧杏仁核在内的中央嗅觉区域中交配或气味诱导的Fos-IR增加。相比之下，在交配的鼻孔闭塞和假闭塞雌性之间，表达Fos-IR的GnRH神经元的百分比没有差异。单独暴露于雄性垫料未能在MBH的GnRH神经元中诱导Fos-IR。因此，雌性雪貂MBH中交配诱导的GnRH神经元排卵前激活似乎仅依赖于生殖器体感输入而非嗅觉输入。
