Neurotrophins in the Brain of Teleost Fish: The State of the Art

Neurotrophins are evolutionary well-conserved molecules, and fish constitute valuable vertebrate models to explore their pleiotropic role in the brain. In addition to an introduction on the evolutionary importance of using fish in biomedicine and their neuroanatomy in comparison with mammals, here we review the available literature on the molecular evolution of neurotrophins and their receptors in teleost fish as well as their role in the fish brain, from the early stages of development until adulthood and aging. Among neurotrophins, BDNF is the most well studied in the brain of teleost fish, and we report data on the functional involvement of the BDNF/TrkB system in the development of the visual system and in the mechanisms of adult brain regeneration. With the exception of neuroanatomical expression, much less is known about the role of the other members of neurotrophin family in fish brain. We hope that this chapter opens new avenues leading to a better understanding of the complex and multifaceted roles of neurotrophins in the brain of fish and other vertebrates.