Dual cholinergic and serotonergic excitatory pathways mediate oxygen sensing in the zebrafish gill

The paradigm is the current understanding of oxygen sensing in vertebrates, which involves specialized respiratory chemoreceptors. This paradigm includes the established role of acetylcholine (ACh) in oxygen sensing in the mammalian carotid body and pulmonary neuroepithelial bodies (NEBs), as well as the recognized presence and role of serotonin (5-HT) in oxygen sensing in fish gill neuroepithelial cells (NECs).

This preprint falls under "Normal Science" because it operates within the existing paradigm of oxygen sensing in vertebrates. While it presents novel findings about the specific mechanisms and neurotransmitters involved in zebrafish gill oxygen sensing, it does not challenge the fundamental understanding of oxygen sensing or propose a new paradigm. The research elaborates on the established paradigm by identifying two distinct populations of chemoreceptors in zebrafish gills and their respective roles in mediating hypoxic signaling. This contributes to a deeper understanding of oxygen sensing within the accepted framework, characteristic of normal science. There is a degree of uncertainty in classifying between Normal Science and Model Drift. Because the study identifies novel cell types and pathways, it could be construed as exhibiting slight deviation from existing models of gill oxygen sensing (Model Drift). However, the core finding that ACh and 5HT mediate oxygen sensing in the gills, activating vagal ganglia, still falls firmly within the established understanding of the process, ultimately favouring a classification of Normal Science.