Anadón Ramón, Rodríguez-Moldes Isabel, Adrio Fátima
Área de Bioloxía Celular, Departamento de Bioloxía Funcional, CIBUS, Facultade de Bioloxía, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
J Comp Neurol. 2024 Feb;532(2):e25590. doi: 10.1002/cne.25590.
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the central nervous system (CNS) of vertebrates. Immunohistochemical techniques with specific antibodies against GABA or against its synthesizing enzyme, glutamic acid decarboxylase (GAD) allowed characterizing GABAergic neurons and fibers in the CNS. However, studies on the CNS distribution of GABAergic neurons and fibers of bony fishes are scant and were done in teleost species. With the aim of understanding the early evolution of this system in bony vertebrates, we analyzed the distribution of GABA-immunoreactive (-ir) and GAD-ir neurons and fibers in the CNS of a basal ray-finned fish, the Siberian sturgeon (Chondrostei, Acipenseriformes), using immunohistochemical techniques. Our results revealed the presence and distribution of GABA/GAD-ir cells in different regions of the CNS such as olfactory bulbs, pallium and subpallium, hypothalamus, thalamus, pretectum, optic tectum, tegmentum, cerebellum, central grey, octavolateralis area, vagal lobe, rhombencephalic reticular areas, and the spinal cord. Abundant GABAergic innervation was observed in most brain regions, and GABAergic fibers were very abundant in the hypothalamic floor along the hypothalamo-hypophyseal tract and neurohypophysis. In addition, GABA-ir cerebrospinal fluid-contacting cells were observed in the alar and basal hypothalamus, saccus vasculosus, and spinal cord central canal. The distribution of GABAergic systems in the sturgeon brain shows numerous similarities to that observed in lampreys, but also to those of teleosts and tetrapods.
γ-氨基丁酸（GABA）是脊椎动物中枢神经系统（CNS）中的主要抑制性神经递质。使用针对GABA或其合成酶谷氨酸脱羧酶（GAD）的特异性抗体的免疫组织化学技术，能够对中枢神经系统中的GABA能神经元和纤维进行特征描述。然而，关于硬骨鱼类GABA能神经元和纤维在中枢神经系统分布的研究较少，且这些研究是在硬骨鱼纲物种中进行的。为了了解该系统在硬骨脊椎动物中的早期进化，我们使用免疫组织化学技术分析了一种基干辐鳍鱼——西伯利亚鲟（软骨硬鳞类，鲟形目）中枢神经系统中GABA免疫反应性（-ir）和GAD-ir神经元及纤维的分布。我们的结果揭示了GABA/GAD-ir细胞在中枢神经系统不同区域的存在和分布，这些区域包括嗅球、大脑皮质和大脑皮质下区域、下丘脑、丘脑、顶盖前区、视顶盖、被盖、小脑、中央灰质、八侧线区、迷走叶、后脑网状区域以及脊髓。在大多数脑区观察到丰富的GABA能神经支配，并且沿着下丘脑-垂体束和神经垂体，下丘脑底部的GABA能纤维非常丰富。此外，在翼侧和基底下丘脑、血管囊以及脊髓中央管中观察到了GABA-ir脑脊液接触细胞。鲟鱼脑中GABA能系统的分布与在七鳃鳗中观察到的情况有许多相似之处，但也与硬骨鱼纲和四足动物的情况相似。
