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.

中文翻译：

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食人鱼鱼脑中的Orexin / Hypocretin系统的组织：与单胺和神经肽Y可能的关系的评估。

Holosteans是一小群放线翅目鱼类，被认为是硬骨鱼类的姊妹群。尽管靠近最大的脊椎动物群，但进行了相对较少的研究来调查这组鱼类的中枢神经系统的组织。在这项研究中，分析了2种现存全息动物的3种代表性物种（斑点雀Le Lepisosteus oculatus，佛罗里达雀gar Lepisosteus）的大脑中食欲素/促胰泌素样免疫反应（OX-ir）细胞体和纤维的神经解剖分布。 platyrhincus和Bowfin Amia calva。使用了针对orexin-A（OXA）和orexin-B（OXB）的抗体，它们标记了整个大脑中相同的细胞和纤维。此外，进行了双重免疫组化荧光检测，同时检测酪氨酸羟化酶，5-羟色胺和神经肽Y（NPY）的OXA和OXB，以试图精确定位食欲能结构并研究这些神经活性物质之间可能的相互作用。三种物种中OX-ir细胞的分布模式基本相似，显示标记的细胞位于视前区（POA）以及下丘脑和管状的区域，而物种之间的标记细胞密度只有细微的差异。在这3个物种的所有主要脑部中都发现了OX-ir纤维，主要分布在腹膜下区域，POA，下丘脑，后结节，丘脑和中脑顶盖。观察到与儿茶酚胺能和5-羟色胺能细胞群有关的食欲素能纤维的密度不同，并且在相同的下丘脑神经元中食欲素和NPY之间没有共定位。将这些结果与在其他脊椎动物中获得的结果进行比较，突显了这一神经传递系统在放线y类鱼类的不同组之间，尤其是硬骨鱼中的恒定分布模式。还观察到所有研究脊椎动物共有的保守特征，例如下丘脑基底中OX-ir细胞的存在，反映了这些神经肽在进化过程中的保守功能。将这些结果与在其他脊椎动物中获得的结果进行比较，突显了这一神经传递系统在放线y类鱼类的不同组之间，尤其是硬骨鱼中的恒定分布模式。还观察到所有研究脊椎动物共有的保守特征，例如下丘脑基底中OX-ir细胞的存在，反映了这些神经肽在进化过程中的保守功能。将这些结果与在其他脊椎动物中获得的结果进行比较，突显了这一神经传递系统在放线y类鱼类的不同组之间，尤其是硬骨鱼中的恒定分布模式。还观察到所有研究脊椎动物共有的保守特征，例如下丘脑基底中OX-ir细胞的存在，反映了这些神经肽在进化过程中的保守功能。