Summary: | Using immunohistochemistry targeting a receptor tyrosine kinase, c-Kit, of the ICC, the ontogeny of these cells in the horse was described. This demonstrated a proximal to distal, as well as a transmural developmental gradient in the large intestine with evidence of ongoing postnatal development. Additionally, the density of ICC in healthy, adult horses was compared to that in horses with obstructive intestinal disease requiring surgical correction. This demonstrated a significant reduction in ICC density in horses with obstructive disorders of the large intestine compared to the control group. In addition, ICC density and distribution was investigated in recovered equine grass sickness horses as well as in normal and diseased donkeys. The c-<i>kit </i>gene, encoding the c-Kit receptor of the ICC, was identified in intestinal tissue samples. The transcription levels of this gene were determined and comparisons made between healthy and diseased horses using quantitative real-time PCR analysis. A parallel immunohistochemical assessment was also performed. These studies demonstrated no significant changes in gene transcription levels, although a reduction in ICC density (using c-Kit immunohistochemistry) in horses with an obstructive disorder of the large colon was evident, suggesting that future investigations of c-<i>kit </i>post-transcriptional control as well as c-Kit protein pathology are warranted. Investigation of the <i>in vitro</i> electrical activity of the equine large colon was carried out using intracellular microelectrode recording techniques in order to characterise slow waves and other electrical activity in this anatomical region from normal horses. It is hoped that this study will help improve our knowledge on the involvement of ICC in equine intestinal motility in health and disease.
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