Changes in the somatostatin (SOM)-like immunoreactivity within nervous structures of the porcine descending colon under various pathological factors

This study reports on changes in the somatostatin-like immunoreactive (SOM-LI) nerve structures of the enteric nervous system (ENS) in the porcine descending colon, caused by chemically driven inflammation, proliferative enteropathy (PE), which is a “natural” inflammation with proliferative changes and nerve injury (axotomy). The distribution pattern of SOM-LI structures was studied using the immunofluorescence technique in the circular muscle layer, the myenteric (MP), outer submucous (OSP) and inner submucous plexuses (ISP) and also in the mucosal layer. Under physiological conditions SOM-LI perikarya have been shown to constitute 1.97 ± 0.36%, 2.06 ± 0.33% and 4.23 ± 0.40% in the MP, OSP and ISP, respectively. Changes in SOM-immunoreactivity depended on the pathological factor and the part of the ENS studied. Numbers of the SOM-LI perikarya amounted 1.81 ± 0.30, 1.97 ± 0.24 and 11.15 ± 0.95 during chemically induced colitis and 3.21 ± 0.37%, 4.33 ± 0.33% and 4.42 ± 0.32% after axotomy in MP, OSP and ISP, respectively. Moreover during PE SOM-positive cell bodies were not observed at all in MP, whereas within OSP and ISP the number of SOM-LI perikarya amounted to 3.34 ± 0.36 and 10.92 ± 059, respectively. All processes studied resulted in a decrease in the number of SOM-LI nerve fibers in the mucosal layer, whereas within the circular muscle layer chemically induced inflammation and axotomy caused an increase in the number of the SOM-LI nerve fibers contrary to PE, which reduced the number of such fibers. The obtained results suggest that SOM-LI nerve structures of the ENS may participate in various pathological states within the porcine descending colon and their functions probably depend on the type of pathological factor.