REGIONAL SPECIFICITIES IN THE DISTRIBUTION, CHEMICAL PHENOTYPES, AND COEXISTENCE PATTERNS OF NEUROPEPTIDE CONTAINING NERVE-FIBERS IN THE HUMAN ANAL-CANAL

Despite the pivotal clinical significance of the human anal canal, lit tle is known about its total and specific innervation. This study asse ssed the comparative distribution and histotopology of nerve fibres im munoreactive for neural markers and a variety of regulatory active neu ropeptides in the human anal canal by light microscopic immunohistoche mistry. Depending on the epithelial zone and region of the anal canal, the neural elements were differentially immunoreactive for the pan-ne ural marker protein gene product 9.5, the catecholamine marker tyrosin e hydroxylase, the neuroendocrine marker chromogranin A, and various n europeptides. Protein gene product 9.5-immunoreactive nerve fibres wer e ubiquitously abundant in the anal canal. In the anal transitional zo ne, ectopic epithelial types were supplied by the same pattern of pept idergic nerves as the respective type of epithelium in normotopic loca tion. In the dermis of the squamous zone and in the perianal epidermis , unusual distribution patterns of nerve fibres, referred to as areas of high nerve fibre density, were encountered. Double immunohistochemi stry revealed region-specific coexistence patterns of neuropeptidergic nerve fibres, and novel peptide coexistence patterns were detected in anal nerve fibres. Subsets of nerve fibres formed close spatial relat ionships with chromogranin A-positive neuroendocrine cells, most frequ ently in the anal transitional zone. Chromogranin-A positive cells wer e shown to be present in the epithelium of perianal eccrine sweat glan ds. The differential distribution, peptide phenpotypes and coexistence patterns of different nerve fibre populations in the human anal canal may reflect topospecific regulatory functions of neurally released ne uropeptides in health and disease. (C) 1993 Wiley-Liss, Inc.