Background & aims: Ulcerative colitis is associated with deranged motility, with consequent diarrhoea and alterations of the colonic transit. Modifications of smooth muscle functions and of the structure of intramural plexuses have been proposed to explain some clinical features of symptomatic colitis, but histological and functional changes of the intrinsic nerves have not been fully explored. Therefore, we investigated the neuronal alterations in a model of experimental colitis, focusing our attention on the abnormalities in myenteric plexus structure and function. Methods: Under urethane anaesthesia, rats were given an intrarectal administration of 0.25 ml of trinitrobenzene sulfonic acid (TNBS) (30 mg/rat in 30% ethanol) and sacrificed after a period of 7 or 15 days. Ethanol- or saline-treated rats were used for comparison. Myenteric plexus morphology was studied by immunocytochemical techniques, using specific markers for neurons (PGP 9.5) and synapsis (synaptophysin and SNAP 25). The functional integrity of the cholinergic system was investigated by measuring the 3H-choline uptake in colonic smooth muscle-myenteric plexus (SMMP) preparations and the outflow of tritium in response to electrical field stimulation (EFS, 2 Hz, 1 msec, supramax. amplitude for 3 min). Tritium outflow was used as a marker of the acetylcholine release from cholinergic nerve endings. Results: TNBS produced a macroscopic damage of the colonic wall, consisting in ulcerative lesions of the mucosa and/or the submucosa and hypertropy of the muscular layers. The lesions were more evident on the distal side of the intestine, close to the site of TNBS injection (8 cm from the anus). The specific neuronal marker PGP 9.5 was significantly increased in areas with partially conserved mucosa or with ulcerative lesions limited to the submucosal layer, at both 7 and 15 days after TNBS treatment. Conversely, in necrotic areas, PGP 9.5 expression was drastically reduced at 7 days and no expression of the marker was measured at 15 days. Similarly, the specific synaptic markers, SNAP-25 and synaptophysin, were increased in areas surrounding the ulcerative lesion, suggesting neuronal plasticity in surviving neurons. In colonic SMMP from rats at 7 or 15 days after pre-treatment, a reduced 3H-choline uptake was observed, compared with preparations from ethanol- or saline-treated animals. The effect was more evident in preparations from the distal portion of the colon, but also evident in the proximal region. Moreover, the tritium outflow evoked by EFS was lower at 7 days, compared to control or ethanol-treated animals, and virtually undetectable at 15 days. Conclusions: These data suggest that TNBS-induced colitis in rats is characterised by time-dependent alterations in myenteric plexus structure and by a reduced activity of the cholinergic nerve endings. These alterations could be responsible of the altered motility patterns which frequently occur in ulcerative colitis.

Morphological and functional alterations of the myenteric plexus in rats with TNBS-induced colitis / Poli, Enzo; Lazzaretti, Mirca; Grandi, Daniela; Pozzoli, Cristina; Coruzzi, G.. - (2000). (Intervento presentato al convegno International Symposium on Brain-Gut axis tenutosi a Toulouse (France) nel July 2-5, 2000).

Morphological and functional alterations of the myenteric plexus in rats with TNBS-induced colitis

POLI, Enzo;LAZZARETTI, Mirca;GRANDI, Daniela;POZZOLI, Cristina;
2000-01-01

Abstract

Background & aims: Ulcerative colitis is associated with deranged motility, with consequent diarrhoea and alterations of the colonic transit. Modifications of smooth muscle functions and of the structure of intramural plexuses have been proposed to explain some clinical features of symptomatic colitis, but histological and functional changes of the intrinsic nerves have not been fully explored. Therefore, we investigated the neuronal alterations in a model of experimental colitis, focusing our attention on the abnormalities in myenteric plexus structure and function. Methods: Under urethane anaesthesia, rats were given an intrarectal administration of 0.25 ml of trinitrobenzene sulfonic acid (TNBS) (30 mg/rat in 30% ethanol) and sacrificed after a period of 7 or 15 days. Ethanol- or saline-treated rats were used for comparison. Myenteric plexus morphology was studied by immunocytochemical techniques, using specific markers for neurons (PGP 9.5) and synapsis (synaptophysin and SNAP 25). The functional integrity of the cholinergic system was investigated by measuring the 3H-choline uptake in colonic smooth muscle-myenteric plexus (SMMP) preparations and the outflow of tritium in response to electrical field stimulation (EFS, 2 Hz, 1 msec, supramax. amplitude for 3 min). Tritium outflow was used as a marker of the acetylcholine release from cholinergic nerve endings. Results: TNBS produced a macroscopic damage of the colonic wall, consisting in ulcerative lesions of the mucosa and/or the submucosa and hypertropy of the muscular layers. The lesions were more evident on the distal side of the intestine, close to the site of TNBS injection (8 cm from the anus). The specific neuronal marker PGP 9.5 was significantly increased in areas with partially conserved mucosa or with ulcerative lesions limited to the submucosal layer, at both 7 and 15 days after TNBS treatment. Conversely, in necrotic areas, PGP 9.5 expression was drastically reduced at 7 days and no expression of the marker was measured at 15 days. Similarly, the specific synaptic markers, SNAP-25 and synaptophysin, were increased in areas surrounding the ulcerative lesion, suggesting neuronal plasticity in surviving neurons. In colonic SMMP from rats at 7 or 15 days after pre-treatment, a reduced 3H-choline uptake was observed, compared with preparations from ethanol- or saline-treated animals. The effect was more evident in preparations from the distal portion of the colon, but also evident in the proximal region. Moreover, the tritium outflow evoked by EFS was lower at 7 days, compared to control or ethanol-treated animals, and virtually undetectable at 15 days. Conclusions: These data suggest that TNBS-induced colitis in rats is characterised by time-dependent alterations in myenteric plexus structure and by a reduced activity of the cholinergic nerve endings. These alterations could be responsible of the altered motility patterns which frequently occur in ulcerative colitis.
2000
Morphological and functional alterations of the myenteric plexus in rats with TNBS-induced colitis / Poli, Enzo; Lazzaretti, Mirca; Grandi, Daniela; Pozzoli, Cristina; Coruzzi, G.. - (2000). (Intervento presentato al convegno International Symposium on Brain-Gut axis tenutosi a Toulouse (France) nel July 2-5, 2000).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/1451774
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