A reduction in interstitial cells of Cajal in horses with equine dysautonomia (grass sickness)

Equine dysautonomia (grass sickness) is a common, frequently fatal disease of horses characterised by dysfunction of the gastrointestinal tract. Inter stitial cells of Cajal are the c-Kit-immunoreactive cells responsible for t he generation of pacemaker activity in gastrointestinal smooth muscle. Impa irment of this pacemaker action has been implicated in several motility dis orders in humans and laboratory mammals. The aim of this study was to test the hypothesis that changes in interstitial cells of Cajal may be involved in the pathophysiology of the intestinal dysfunction observed in equine gra ss sickness. Interstitial cells of Cajal were identified using immunohistoc hemical labelling with an anti-c-Kit antibody and their density was assesse d using a semi-quantitative grading system. Segments of ileum were examined from 24 horses free from gastrointestinal disease and compared to tissues from 28 horses with grass sickness. Segments of the pelvic flexure region o f the large colon were examined from 13 horses free from gastrointestinal d isease and compared to tissues from 10 horses with grass sickness. In horse s with grass sickness, interstitial cells of Cajal were significantly decre ased in both the myenteric plexus and circular muscle regions of both ileum and pelvic flexure compared to normal animals. Therefore, it is possible t hat the decline in interstitial cells of Cajal may be an important factor i n the development of intestinal dysmotility observed in grass sickness. (C) 2001 Elsevier Science B.V. All rights reserved.