Figure 14.

(A–C). Diagram of the interaction between NECs and mast cells and the innervation of the NECs in the gill filament. (A). 1, External environment; 2, afferent synapses and the 5HT neurons (N) connect to central nervous system through the filament nerve (FN); 3, afferent synapses on sympathetic and cranial (parasympathetic) nerves, efFA, efferent filament artery, CVS, central venous sinus. Figure adapted from Bailly (2009). (B). Scheme of the interactions among the NECs, mast cells and nerves from a gill section of the catfish H. fossilis immunolabeled with antibodies to Pis 1. NECs (blue arrows) are innervated by afferent vagal nerve endings (asterisks) and are in close contact with mast cells (black arrows, Pis 1: red fluorescence). These cells’ release, in addition to Pis 1, 5HT, neuropeptides, GABA and its receptor GABA B R1, also contains acetylcholine and its muscarinic and nicotinic receptors, and regulate both innate and adaptative mucosal immunity. (C). Section of the H.fossilis gills immunostained with antibodies against Met-enk (green) and Pis 1 (red), showing the presence of Pis-positive NECs (arrows) and NECs immunostained by both the two antibodies (arrowheads). Scale bar = 20 µm.