RT Journal Article T1 Distribution of gamma‐aminobutyric acid immunoreactivity in the brain of the Siberian sturgeon (Acipenser baeri): Comparison with other fishes A1 Anadón Álvarez, Ramón A1 Rodríguez-Moldes Rey, María Isabel A1 Adrio Fondevila, Fátima AB 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. PB Wiley SN 0021-9967 YR 2024 FD 2024 LK http://hdl.handle.net/10347/34619 UL http://hdl.handle.net/10347/34619 LA eng NO Anadón, R., Rodríguez-Moldes, I., & Adrio, F. (2024). Distribution of gamma-aminobutyric acid Immunoreactivity in the brain of the Siberian sturgeon (Acipenser baeri): Comparison with other fishes. Journal of Comparative Neurology, 532, e25590. https://doi.org/10.1002/cne.25590 NO This work was supported by The Ministerio de Economía, Industria y Competitividad- Agencia Estatal de Investigación (grant No. BFU2017-89861-P) partially financed by the European Social Fund and by Xunta de Galicia (Grant No. ED431C 2021/18). We also thank Dr. Mercedes Rivas Cascallar for technical assistance with the confocal microscope. DS Minerva RD 24 abr 2026