ABSTRACT
Title
Immunohistochemical distribution of synaptophysin in the rat gastric fundus and distal colon: influence of Nociceptin/Orphanin FQ and cold-restraint stress
Authors
G. Morini1, D. Grandi1, R. Guerrini2, M. Massi3
1Dept. of Human Anatomy, Pharmacology and Forensic Medicine, University of Parma, Parma, Italy; 2 Dept. of Pharmaceutical Sciences and Biotechnology Center, University of Ferrara, Ferrara, Italy;3 Dept. of Experimental Medicine and Public Health, University of Camerino, Camerino, Italy.
1Dept. of Human Anatomy, Pharmacology and Forensic Medicine, University of Parma, Parma, Italy; 2 Dept. of Pharmaceutical Sciences and Biotechnology Center, University of Ferrara, Ferrara, Italy;3 Dept. of Experimental Medicine and Public Health, University of Camerino, Camerino, Italy.
Abstract
Nociceptin/orphanin FQ (N/OFQ) is a neuropeptide regulating gastrointestinal functions. In the present study, the possible influence of short- and long term-infusion of N/OFQ and of cold-restraint stress on synaptophysin immunoreactivity in nerve fibers innervating the mucosa of gastric fundus and distal colon was assessed. Male Wistar rats were infused with saline or N/OFQ (1 ug/kg/h) via subcutaneously implanted Alzet osmotic minipumps for 4 and 52 hours and 14 days. Stress was induced by restraining the rats into individual wire-mesh restraint cages in a cold room at 3 °C for 3 h.The distribution of synaptophysin in the mucosa of gastric fundus and distal colon was investigated using immunohistochemical methods. Results were expressed as the surface (µm2) occupied by synapthophysin immunoreactivity per mm2 of mucosa. In saline-infused rats, immunoreactivity to synaptophysin was widely distributed throughout the gastric and the colonic wall. The mucosal surface of synaptophysin immunostaining was 322 ± 25 µm2/mm2 in the gastric fundus and 375 ± 46 µm2/mm2 in the distal colon. Continuous subcutaneous administration of N/OFQ exerted opposite effects in the two regions of the gastrointestinal tract. In the gastric fundus, N/OFQ significantly increased immunostained areas by 46% (P<0.01), 103% (P<0.01) and 93% (P<0.01) following 4hour, 52 hour and 14 day administration respectively, compared with saline-treated controls. By contrast, in the distal colon, the density of synaptophysin immunoreactivity was decreased by 20% after 4 hours, compared with saline-treated controls, while, following 52 hours and 14 days of continuous administration, immunostained areas were not significantly different from control values. Exposure to cold-restraint stress induced similar responses as N/OFQ infusion. In fact areas immunopositive for synaptophysin were significantly increased by 89% (P<0.01) in the fundic mucosa and slightly, not significantly, decreased in the colonic mucosa, compared with saline-treated controls.
The present findings provide evidence that N/OFQ modifies the density of synaptophysin immunoreactivity in the fundic and colonic mucosa, paralleling the effect of acute stress. The opposite effects exerted in the two regions both by N/OFQ and by acute stress could be dependent on different regional mechanisms mediating their effects. Changes in the synaptic protein could be interrelated with the regulation by N/OFQ of mucosal mast cell recruitment in the gastrointestinal tract.
The present findings provide evidence that N/OFQ modifies the density of synaptophysin immunoreactivity in the fundic and colonic mucosa, paralleling the effect of acute stress. The opposite effects exerted in the two regions both by N/OFQ and by acute stress could be dependent on different regional mechanisms mediating their effects. Changes in the synaptic protein could be interrelated with the regulation by N/OFQ of mucosal mast cell recruitment in the gastrointestinal tract.