LOCALISATION OF THE INTERSTITIAL CELLS OF CAJAL IN RAINBOW TROUT

Abstract: The interstitial cells of Cajal (ICC) are primarily placed in the gastrointestinal tract, where they play a crucial role in the initiation and control of motility by operating as pacemaker cells. They also have a role in neurotransmission. ICC’s functions have been investigated, especially in mammals, but less is known about the cells in fish. This study explored the presence and distribution of ICC in rainbow trout (Oncorhynchus mykiss) using immunohistochemistry on tissue preparation from six different regions of the gastrointestinal tract. This was done to investigate the difference in the distribution of ICC between the regions. The primary antibodies were directed against anoctamin 1 (Ano-1), targeting the ICC, and the neuronal marker acetylated tubulin (AcT), some preparations were simultaneously incubated with Ano-1 and AcT. Ano-1 immunoreactive structures were found in the proximal-, mid-, and distal intestine, but no Ano-1 immunoreactive cells were found in the cardiac stomach, pyloric stomach, or rectum. Wholemount preparations of the myenteric plexus, situated between the two muscle layers, showed singular fibres with branched extensions. These cells were located above AcT immunoreactive nerve fibres closer to the circular muscle layer. Nerves and potential ICC could be distinguished situated in the same area, but there was no overlap between them. The immunohistochemistry performed on the paraffin sectioned preparations resulted in Ano-1 immunoreactivities found in the myenteric plexus and the circular muscle layer. Occasional cells were located deeper into the circular muscle layer. The distribution and location of the Ano-1 immunoreactive structures suggest that they are ICC. The result also shows that even though most of the ICC are located adjacent to the myenteric plexus, some cells are also found in the circular muscle layer. Further studies are required to examine if there are anatomically and functionally differences between the cells.