Jennings Kimberly J, Chasles Manon, Cho Hweyryoung, Mikkelsen Jens, Bentley George, Keller Matthieu, Kriegsfeld Lance J
Department of Psychology, University of California, Berkeley, CA 94720, USA.
Department of Neurology and Neurobiology Research Unit, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
Integr Comp Biol. 2017 Nov 1;57(5):1055-1065. doi: 10.1093/icb/icx099.
Males of many species rely on chemosensory information for social communication. In male Syrian hamsters (Mesocricetus auratus), as in many species, female chemosignals potently stimulate sexual behavior and a concurrent, rapid increase in circulating luteinizing hormone (LH) and testosterone (T). However, under winter-like, short-day (SD) photoperiods, when Syrian hamsters are reproductively quiescent, these same female chemosignals fail to elicit behavioral or hormonal responses, even after T replacement. It is currently unknown where in the brain chemosensory processing is gated in a seasonally dependent manner such that reproductive responses are only displayed during the appropriate breeding season. The goal of the present study was to determine where this gating occurred by identifying neural loci that respond differentially to female chemosignals across photoperiods, independent of circulating T concentrations. Adult male Syrian hamsters were housed under either long-day (LD) (reproductively active) or SD (reproductively inactive) photoperiods with half of the SD animals receiving T replacement. Animals were exposed to either female hamster vaginal secretions (FHVSs) diluted in mineral oil or to vehicle, and the activational state of chemosensory processing centers and elements of the neuroendocrine reproductive axis were examined. Components of the chemosensory pathway upstream of hypothalamic centers increased expression of FOS, an indirect marker of neuronal activation, similarly across photoperiods. In contrast, the preoptic area (POA) of the hypothalamus responded to FHVS only in LD animals, consistent with its role in promoting expression of male sexual behavior. Within the neuroendocrine axis, the RF-amide related peptide (RFRP), but not the kisspeptin neuronal system responded to FHVS only in LD animals. Neither response within the POA or the RFRP neuronal system was rescued by T replacement in SD animals, mirroring photoperiodic regulation of reproductive responses. Considering the POA and the RFRP neuronal system promote reproductive behavior and function in male Syrian hamsters, differential activation of these systems represents a potential means by which photoperiod limits expression of reproduction to the appropriate environmental context.
许多物种的雄性依靠化学感应信息进行社交交流。与许多物种一样，在雄性叙利亚仓鼠（金仓鼠）中，雌性化学信号会强烈刺激性行为，并使循环中的促黄体生成素（LH）和睾酮（T）同时迅速增加。然而，在类似冬季的短日照（SD）光周期下，当叙利亚仓鼠处于生殖静止状态时，即使在补充睾酮后，这些相同的雌性化学信号也无法引发行为或激素反应。目前尚不清楚大脑中化学感应处理在何处以季节性依赖的方式受到调控，从而使得生殖反应仅在适当的繁殖季节表现出来。本研究的目的是通过识别在不同光周期下对雌性化学信号有不同反应的神经位点来确定这种调控发生的位置，而不受循环中睾酮浓度的影响。成年雄性叙利亚仓鼠被饲养在长日照（LD）（生殖活跃）或短日照（SD）（生殖不活跃）光周期下，其中一半的SD动物接受睾酮替代。动物被暴露于稀释在矿物油中的雌性仓鼠阴道分泌物（FHVSs）或溶剂中，并检查化学感应处理中心和神经内分泌生殖轴各部分的激活状态。下丘脑中心上游的化学感应通路各组成部分，作为神经元激活的间接标志物，FOS的表达在不同光周期下相似地增加。相比之下，下丘脑的视前区（POA）仅在LD动物中对FHVS有反应，这与其在促进雄性性行为表达中的作用一致。在神经内分泌轴内，仅在LD动物中，RF酰胺相关肽（RFRP）而非 kisspeptin 神经元系统对FHVS有反应。SD动物中通过睾酮替代并不能挽救POA或RFRP神经元系统内的任何一种反应，这反映了生殖反应的光周期调节。考虑到POA和RFRP神经元系统促进雄性叙利亚仓鼠的生殖行为和功能，这些系统的差异激活代表了一种潜在方式，通过这种方式光周期将繁殖表达限制在适当的环境背景下。
