Changes in Pituitary Adenylate Cyclase-Activating Peptide 27-Like Immunoreactive Nervous Structures in the Porcine Descending Colon During Selected Pathological Processes

Abstract

This study reports on changes in the pituitary adenylate cyclase-activating peptide 27-like immunoreactive (PACAP-27-LI) nerve structures of the enteric nervous system (ENS) in the porcine descending colon, caused by chemically induced inflammation, nerve injury, and proliferative enteropathy (PE), which is a "natural" inflammation of the porcine digestive tract. The distribution pattern of PACAP-27-LI structures was studied using the immunofluorescence technique in the circular muscle layer, enteric plexuses (i.e., myenteric plexus (MP), outer submucous plexus (OSP), and inner submucous plexus (ISP)), and in the mucosal layer. Under physiological conditions, PACAP-27-LI perikarya have been shown to constitute 4.04 ± 0.66, 6.66 ± 0.77, and 11.19 ± 0.74% in the MP, OSP, and ISP, respectively. Changes in PACAP-27 immunoreactivity depended on the pathological factor studied. The numbers of the PACAP-27-LI perikarya amounted to 12.26 ± 1.43, 12.28 ± 0.79, and 21.13 ± 1.19% in chemically induced colitis, 17.83 ± 0.88, 9.03 ± 1.05, and 20.72 ± 1.35% during PE and 10.65 ± 0.82, 6.88 ± 1.04, and 14.04 ± 1.09% after axotomy in MP, OSP, and ISP, respectively. All of the studied processes generally resulted in an increase in the number of PACAP-27-LI nerve fibers in the circular muscle and mucosal layers. The obtained results suggest that PACAP-27-LI nerve structures of ENS may participate in various pathological states within the porcine descending colon, and their functions probably depend on the type of pathological factor.