Trk neurotrophin-receptor systems and calcium-binding proteins localization in sensory organs of Nothobranchius guentheri. Morphological and immunohistochemical analysis.

Neurotrophins are growth factors responsible for neuronal development, function, survival, differentiation, and plasticity. They exert their functions by binding to specific receptors (Trks) and the p75 neurotrophin receptor. Neurotrophins act in both central and peripheral nervous systems, including sensory organs, where also calcium-binding proteins (CaBPs) operate. These latter are involved in essential physiological functions related to calcium ions such as nerve impulse transmission, neurogenesis, synaptic plasticity, and transmission and they may also have a protective role within both the central nervous system and peripheral sensory systems. Neurotrophins and CaBPs perform their functions in all vertebrates, including fish. Nonetheless, they have never been localized in N. guentheri sensory organs, according to our knowledge. Thanks to its short lifespan, N. guentheri is an emergent model in aging studies and its value is relevant in the context of translational medicine. Thus, this study aimed at locating neurotrophin-receptor systems and CaBPs in N. guentheri mechanosensory organs and retina. Using immunoperoxidase, single double immunofluorescence methods, the investigation revealed N. guentheri localization of neurotrophins and CaBPs in the inner ear, in the neuromasts of the lateral line system, and retinal cells. This discovery demonstrates that these proteins impact N. guentheri biology, further underlining its suitability as an aging studies model. These findings could impact aging-related neurodegenerative research within the context of translational medicine.