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Neurotrophins are a family of growth factor primarily acting in the nervous system, throughout two categories of membrane receptors on the basis of their high (Trk receptors) or low (p75NTR) affinity. Both neurotrophins and Trk receptors are phylogenetically conserved and are expressed not only in the central and peripheral nervous system but also in non-nervous tissues of vertebrates and some invertebrates. The brain-derived neurotrophic factor (BDNF)/TrkB system plays an important role in the development, phenotypic maintenance and plasticity of specific neuronal populations. Considering that this system is poorly characterized in the central nervous system of teleosts, the expression and anatomical distribution of TrkB in the brain of the adult zebrafish using reverse transcriptase-polymerase chain reaction (RT-PCR), Western-blot and immunohistochemistry were analysed. Both the riboprobe and the antibody used were designed to map within the catalytic domain of TrkB. RT-PCR detected specific TrkB mRNA in brain homogenates, while Western-blot identified one unique protein band with an estimated molecular weight of 145kDa, thus corresponding with the TrkB full-length isiform of the receptor. Immunohistochemistry showed specific TrkB immunoreactivity in restricted areas of the encephalon, i.e. the hypothalamus and a specific neuronal subpopulation of the reticular formation. The present results demonstrate, for the first time, that, as in mammals, the encephalon of adult zebrafish expresses TrkB in specific zones related to food intake, behaviour or motor activity., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Sensory cells contain ion channels involved in the organ-specific transduction mechanisms that convert different types of stimuli into electric energy. Here we focus on small-conductance calcium-activated potassium channel 1 (SK1) which plays an important role in all excitable cells acting as feedback regulators in after-hyperpolarization. This study was undertaken to analyze the pattern of expression of SK1 in the zebrafish peripheral nervous system and sensory organs using RT-PRC, Westernblot and immunohistochemistry. Expression of SK1 mRNA was observed at all developmental stages analyzed (from 10 to 100 days post fertilization, dpf), and the antibody used identified a protein with a molecular weight of 70kDa, at 100dpf (regarded to be adult). Cell expressing SK1 in adult animals were neurons of dorsal root and cranial nerve sensory ganglia, sympathetic neurons, sensory cells in neuromasts of the lateral line system and taste buds, crypt olfactory neurons and photoreceptors. Present results report for the first time the expression and the distribution of SK1 in the peripheral nervous system and sensory organs of adult zebrafish, and may contribute to set zebrafish as an interesting experimental model for calcium-activated potassium channels research. Moreover these findings are of potential interest because the potential role of SK as targets for the treatment of neurological diseases and sensory disorders., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Acid-sensing ion channels (ASICs) in mammals monitor acid sensing and mechanoreception. They have a widespread expression in the central and peripheral nervous system, including the gut. The distribution of ASICs in zebrafish is known only in larvae and at the mRNA level. Here we have investigated the expression and cell distribution of ASIC2 in the gut of adult zebrafish using PCR, Western blot and immunohistochemistry. ASIC2 mRNA was detected in the gut, and a protein consistent with predicted ASIC2 (64kDa molecular mass) was detected by Western blot. ASIC2 positivity was found in a subpopulation of myenteric neurons in the enteric nervous system, as well in enteroendocrine epithelial cells. These data demonstrate for the first time the occurrence of ASIC2 in the gut of adult zebrafish where it presumably acts as a chemosensor and a mechanosensor., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

The Sox-2 is a transcription factor involved in adult neurogenesis in different vertebrate species, including fishes. Sox-2 also participates in growth and renewal on sensory cells in neuromasts of the fish lateral line system, and it is essential for development of taste buds in mammals. Using immunohistochemistry and Western blot we have investigated the occurrence and localization of Sox-2 taste buds and neuromast of zebrafish from 10 days post-fertilization to adult stage (1 year). The antibody used identifies two protein bands with estimated molecular weights of 34 and 37kDa which are consistent with those predicted for Sox-2. Sensory cells in taste buds displayed Sox-2 immunoreactivity at all the ages sampled, whereas in the neuromasts Sox-2 expression was restricted to the basal non-sensory cells. Interestingly Sox-2 immunoreactivity was observed in epithelial cells associated with both taste buds and neuromasts. Present results demonstrate that Sox-2 expressed in taste buds and neuromasts of zebrafish during the whole lifespan. Nevertheless, whereas the role of Sox-2 in taste buds of zebrafish remains to be established, the results in neuromast suggest that Sox-2 could participate in cell renewal of the mechanosensory cells.