Immunocytochemical Identification and Localization of Diffuse Neuroendocrine System (DNES) Cells in Gastrointestinal Tract of Channel Catfish (Ictalurus punctatus)

To detect distribution and relative frequency of diffuse neuroendocrine system (DNES) cells in the gastrointestinal tract of channel catfish (Ictalurus punctatus), the intestinal tract of channel catfish was divided into seven portions from proximal to distal: the enlarged area after oesophagus, cardia, fundus, pylorus, and anterior, middle, and posterior intestine. Immunohistochemical method using the strept avidin-biotin-complex (SABC) was employed. All antisera between seven portions of the channel catfish were compared statistically using statistical package for the social science (SPSS). Five types of DNES cells were determined: neuropeptide Y-immunoreactive (NPY-IR) cells were demonstrated in both anterior and middle intestine; serotonin (5-HT) immunoreactive cells were detected throughout the whole gastrointestinal tract; vasoactive intestinal peptide (VIP) positive cells were at the highest frequency in pylorus; glucagon-immunoreactive (GLU-IR) cells were moderate in number in the fundus and anterior, middle intestine, and no immunoreactivity was determined in the other portions; somatostatin (SOM) positive cells were more abundant in the anterior and middle intestine. The regional distribution and relative frequency of immunoreactive cells in the channel catfish, Ictalurus punctatus, are essentially similar to those of other fish. However, some characteristics are observed in this species, which further proved that the diversity of the physiological function of DNES cells was based on their morphology.