Kashiwayanagi Makoto
Pheromones, which provide specific information concerning the identity, gender, and endocrine status in a variety of mammals have been found in saliva, skin gland secretions, and urine (Halpern and Martinez-Marcos 2003; Powers and Winans 1975; Wysocki and Meredith 1987). The modulation of gonadal function by the smell of urine has been well established in rodent VNOs (Halpern and Martinez-Marcos 2003; Keverne et al. 1986; Wysocki and Meredith 1987). In rats, pheromones in urine excreted from males and females induce various changes in gonadal functions such as reflex ovulation in the absence of coitus and mounting (Johns et al. 1978), a reduction in the estrous cycle of females from 5 to 4 days (Chateau et al. 1976), and estrous synchrony among females living together (McClintock 1978). In addition, exposure to male pheromones elicits the release of luteinizing hormone (Rajendren et al. 1990) and estrous synchrony among females that are living together (McClintock 1978). The vomeronasal system is a second olfactory system organized in parallel with the main olfactory system. The VNO, which is the peripheral chemoreceptor organ of the vomeronasal system, forms a bilateral tubular structure in the ventral part of the nasal cavity of rats. The interaction of a pheromone with receptors of VNSs initiates a sequential molecular event leading to action potential initiation. In the present chapter, we first addressed the mechanism of pheromone reception by the VNO in rats. Chemical signals excreted from animals affect the sexual behavior of conspecific male and female animals. Information regarding the females’ endocrine state is transmitted to males by means of urinary pheromones. Sexually experienced male rats prefer estrous to diestrous urine odor (Lydell and Doty 1972; Pfaff and Pfaffmann 1969). The VSNs project information to the mitral cells (MTCs) in the AOB located on the dorsocaudal surface of the main olfactory bulb (MOB) (Rajendren et al. 1990). Pheromonal information transmitted via the MTC is modified by GABA-immunoreactive interneurons at the periglomerular cell (PGC) layer and by granule cells (GCs) (Keverne et al. 1986; Halpern and Martinez-Marcos 2003; Wysocki and Meredith 1987). Comparison of c-Fos expression, which is correlated with the neural activity of sexually experienced and inexperienced males after exposure to estrous or diestrous urine shows changes in cellular responses to urinary pheromones as related to sexual experience (Honda et al. 2008). In the lateral and rostral sectors of the PGC, many more Fos-immunoreactive (Fos-ir) cells were observed in the sexually experienced rats than in the inexperienced rats. In the latter part of this chapter, I will describe possible mechanisms concerning changes in neural function with sexual experiences and aging.
信息素存在于唾液、皮肤腺体分泌物及尿液中，它能提供有关各种哺乳动物的身份、性别及内分泌状态的特定信息（哈尔彭和马丁内斯 - 马科斯，2003年；鲍尔斯和维南斯，1975年；怀索基和梅雷迪思，1987年）。尿液气味对性腺功能的调节在啮齿动物的犁鼻器中已得到充分证实（哈尔彭和马丁内斯 - 马科斯，2003年；凯弗内等人，1986年；怀索基和梅雷迪思，1987年）。在大鼠中，雄性和雌性排出尿液中的信息素会引起性腺功能的各种变化，如在无交配和爬跨情况下的反射性排卵（约翰斯等人，1978年）、雌性发情周期从5天缩短至4天（沙托等人，1976年）以及共同生活的雌性之间的发情同步（麦克林托克，1978年）。此外，暴露于雄性信息素会引发促黄体生成素的释放（拉金德伦等人，1990年）以及共同生活的雌性之间的发情同步（麦克林托克，1978年）。犁鼻系统是与主嗅觉系统并行组织的第二嗅觉系统。犁鼻器是犁鼻系统的外周化学感受器器官，在大鼠鼻腔腹侧形成双侧管状结构。信息素与犁鼻系统受体的相互作用引发一系列分子事件，导致动作电位的产生。在本章中，我们首先探讨了大鼠犁鼻器接收信息素的机制。动物排出的化学信号会影响同种雄性和雌性动物的性行为。关于雌性内分泌状态的信息通过尿液信息素传递给雄性。有性经验的雄性大鼠更喜欢发情期尿液的气味而非动情间期尿液的气味（利德尔和多蒂，1972年；普法夫和普法夫曼，1969年）。犁鼻感觉神经元将信息投射到位于主嗅球背尾表面的副嗅球中的二尖瓣细胞（MTCs）（拉金德伦等人，1990年）。通过MTC传递的信息素信息在球周细胞（PGC）层被γ - 氨基丁酸免疫反应性中间神经元以及颗粒细胞（GCs）修饰（凯弗内等人，1986年；哈尔彭和马丁内斯 - 马科斯，2003年；怀索基和梅雷迪思，1987年）。比较暴露于发情期或动情间期尿液后有性经验和无性经验雄性的c - Fos表达（其与神经活动相关），结果显示与性经验相关的对尿液信息素的细胞反应存在变化（本田等人，2008年）。在PGC的外侧和吻侧区域，有性经验的大鼠中观察到的Fos免疫反应性（Fos - ir）细胞比无性经验的大鼠更多。在本章的后半部分，我将描述与性经验和衰老相关的神经功能变化的可能机制。
