Lozano Daniel, González Agustín, López Jesús M
Brain Behav Evol. 2018;91(4):228-251. doi: 10.1159/000490172. Epub 2018 Jul 13.
Holosteans form a small group of actinopterygian fishes considered the sister group of teleosts. Despite this proximity to the biggest group of vertebrates, relatively few studies have been conducted to investigate the organization of the central nervous system of this group of fishes. In this study, the neuroanatomical distribution of orexin/hypocretin-like immunoreactive (OX-ir) cell bodies and fibers was analyzed in the brain of 3 representative species of the 2 orders of extant holosteans, the spotted gar Lepisosteus oculatus, the Florida gar Lepisosteus platyrhincus, and the bowfin Amia calva. Antibodies against orexin-A (OXA) and orexin-B (OXB) were used, which labeled the same cells and fibers throughout the brain. In addition, double immunohistofluorescence was performed for the simultaneous detection of OXA and OXB with tyrosine hydroxylase, serotonin, and neuropeptide Y (NPY), in an attempt to localize the orexinergic structures precisely and study the possible interactions between these neuroactive substances. The pattern of distribution of OX-ir cells in the 3 species was largely similar, showing labeled cells in the preoptic area (POA), and the tuberal and retrotuberal hypothalamic regions, with only subtle differences between species in the density of labeled cells. OX-ir fibers were found in all main brain subdivisions of the 3 species, mostly in the ventral subpallial areas, POA, hypothalamus, posterior tubercle, thalamus, and mesencephalic tectum. Different densities of orexinergic fibers were observed in relation to catecholaminergic and serotoninergic cell groups, as well as an absence of colocalization between orexins and NPY in the same hypothalamic neurons. The comparison of these results with those obtained in other vertebrates highlights a constant pattern of distribution of this system of neurotransmission among different groups of actinopterygian fishes, especially in teleosts. Conserved features shared by all vertebrates studied were also observed, such as the presence of OX-ir cells in the basal hypothalamus, reflecting the preserved functions of these neuropeptides over the course of evolution.
全骨鱼类是硬骨鱼纲中一个较小的类群，被认为是真骨鱼类的姐妹群。尽管与最大的脊椎动物类群关系密切，但针对该鱼类群中枢神经系统组织开展的研究相对较少。在本研究中，我们分析了现存全骨鱼类两个目3个代表性物种（眼斑雀鳝Lepisosteus oculatus、佛罗里达雀鳝Lepisosteus platyrhincus和弓鳍鱼Amia calva）大脑中orexin/下丘脑泌素样免疫反应性（OX-ir）细胞体和纤维的神经解剖分布。我们使用了抗orexin-A（OXA）和orexin-B（OXB）的抗体，它们在整个大脑中标记相同的细胞和纤维。此外，我们还进行了双重免疫荧光实验，以同时检测OXA和OXB与酪氨酸羟化酶、5-羟色胺和神经肽Y（NPY），试图精确地定位orexin能结构，并研究这些神经活性物质之间可能的相互作用。3个物种中OX-ir细胞的分布模式大致相似，视前区（POA）、结节部和结节后下丘脑区域均有标记细胞，仅物种间标记细胞密度存在细微差异。在这3个物种的所有主要脑区都发现了OX-ir纤维，主要分布在腹侧皮质下区域、POA、下丘脑、后结节、丘脑和中脑顶盖。观察到orexin能纤维与儿茶酚胺能和5-羟色胺能细胞群的密度不同，并且在同一下丘脑神经元中orexins和NPY不存在共定位。将这些结果与在其他脊椎动物中获得的结果进行比较，突出了该神经传递系统在不同硬骨鱼类群中，尤其是在真骨鱼类中分布的恒定模式。在所有研究的脊椎动物中也观察到了共同的保守特征，如下丘脑基部存在OX-ir细胞，这反映了这些神经肽在进化过程中保留的功能。
