Phoenixin (PNX) is a newly described peptide found in both neural and non-neural tissues. Until now, no attempts have been made to investigate the expression of PNX in the nervous system of animals other than laboratory rodents, in which an enzyme immunoassay revealed the highest quantity of the substance in the spinal cord. Since the domestic pig, due to its anatomical and histological resemblance to humans, is often used as an animal model in biomedical investigations, the present study was designed to examine PNX-immunoreactivity in the spinal cords of female pigs (n = 5). The spinal cords were dissected and divided into the cervical, thoracic, lumbar, sacral and coccygeal segments, which were sectioned transversally into 10-μm-thick serial sections. The sections from each spinal cord segment were processed for double-labelling immunohistochemistry using antibodies against PNX in a mixture with those against calcitonin gene-related peptide (CGRP), substance P (SP) or choline acetyltransferase (CHAT). The PNX-immunoreactivity had a similar distribution in the grey matter of all the spinal cord sections examined and was mainly observed in varicose nerve fibres (NF) that formed a dense plexus in laminae I and II of the dorsal horn. Nearly all of the PNX-immunoreactive NF stained also for CGRP or SP and, interestingly, many of them were CHAT-positive. The present study has provided for the first time the detailed information on the arrangement and chemical features of nerve structures expressing PNX-immunoreactivity in the spinal cord of a large mammal. The exact function of PNX in the spinal cord is not known yet. However, the distribution pattern and immunohistochemical characteristics of PNX-IR NF clearly suggest that this peptite most likely plays a role in spinal noxious signalling.

凤凰蛋白（PNX）是在神经和非神经组织中都发现的一种新描述的肽。迄今为止，除实验室啮齿类动物外，还没有尝试研究PNX在动物神经系统中的表达，在这种动物中，酶免疫法检测出脊髓中该物质的含量最高。由于家猪由于其在解剖学和组织学上与人相似，因此经常在生物医学研究中用作动物模型，因此本研究旨在检查雌性猪脊髓中的PNX免疫反应性（n = 5）。解剖脊髓，并分为颈段，胸段，腰段，骨段和尾骨段，将其横向切成10μm厚的连续切片。使用针对PNX的抗体与针对降钙素基因相关肽（CGRP），P物质（SP）或胆碱乙酰基转移酶（CHAT）的混合物，对来自每个脊髓节段的切片进行双标记免疫组化处理。PNX免疫反应性在所有检查的脊髓节的灰质中都有相似的分布，并且主要观察到在背角I和II层形成密集神经丛的曲张神经纤维（NF）中。几乎所有的PNX免疫反应性NF也都被CGRP或SP染色，有趣的是，其中许多是CHAT阳性的。本研究首次提供了有关在大型哺乳动物的脊髓中表达PNX免疫反应性的神经结构的排列和化学特征的详细信息。尚不清楚PNX在脊髓中的确切功能。然而，PNX-IR NF的分布模式和免疫组化特征清楚地表明，这种肽可能最可能在脊髓有害信号传导中起作用。