Bartzen-Sprauer J, Klosen P, Ciofi P, Mikkelsen J D, Simonneaux V
Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS 3212, Université de Strasbourg, Strasbourg, France.
J Neuroendocrinol. 2014 Aug;26(8):510-20. doi: 10.1111/jne.12171.
In many species, sexual activity varies on a seasonal basis. Kisspeptin (Kp), a hypothalamic neuropeptide acting as a strong activator of gonadotrophin-releasing hormone neurones, plays a critical role in this adaptive process. Recent studies report that two other neuropeptides, namely neurokinin B (NKB) and dynorphin (DYN), are co-expressed with Kp (and therefore termed KNDy neurones) in the arcuate nucleus and that these peptides are also considered to influence GnRH secretion. The present study aimed to establish whether hypothalamic NKB and DYN expression is photoperiod-dependent in a seasonal rodent, the Syrian hamster, which exhibits robust seasonal rhythms in reproductive activity. The majority of Kp neurones in the arcuate nucleus co-express NKB and DYN and the expression of all three peptides is decreased under a short (compared to long) photoperiod, leading to a 60% decrease in the number of KNDy neurones under photo-inhibitory conditions. In seasonal rodents, RFamide-related peptide (RFRP) neurones of the dorsomedial hypothalamus are also critical for seasonal reproduction. Interestingly, NKB and DYN are also expressed in the dorsomedial hypothalamus but do not co-localise with RFRP-immunoreactive neurones, and the expression of both NKB and DYN is higher under a short photoperiod, which is opposite to the short-day inhibition of RFRP expression. In conclusion, the present study shows that NKB and DYN display different photoperiodic variations in the Syrian hamster hypothalamus. In the arcuate nucleus, NKB and DYN, together with Kp, are down-regulated under a short photoperiod, whereas, in the dorsomedial hypothalamus, NKB and DYN are up-regulated under a short photoperiod.
在许多物种中，性活动随季节变化。 kisspeptin（Kp）是一种下丘脑神经肽，作为促性腺激素释放激素神经元的强激活剂，在这一适应性过程中起关键作用。最近的研究报告称，另外两种神经肽，即神经激肽B（NKB）和强啡肽（DYN），在弓状核中与Kp共表达（因此称为KNDy神经元），并且这些肽也被认为会影响GnRH分泌。本研究旨在确定在季节性繁殖活动中表现出强烈季节性节律的叙利亚仓鼠这一季节性啮齿动物中，下丘脑NKB和DYN的表达是否依赖于光周期。弓状核中的大多数Kp神经元共表达NKB和DYN，并且在短（与长相比）光周期下，所有三种肽的表达均降低，导致在光抑制条件下KNDy神经元数量减少60%。在季节性啮齿动物中，下丘脑背内侧的RFamide相关肽（RFRP）神经元对季节性繁殖也至关重要。有趣的是，NKB和DYN也在下丘脑背内侧表达，但不与RFRP免疫反应性神经元共定位，并且NKB和DYN在短光周期下的表达均较高，这与RFRP表达的短日照抑制相反。总之，本研究表明，在叙利亚仓鼠下丘脑中，NKB和DYN表现出不同的光周期变化。在弓状核中，NKB和DYN与Kp一起在短光周期下被下调，而在下丘脑背内侧，NKB和DYN在短光周期下被上调。
