POLARIZED INNERVATION PATTERN OF THE MUCOSE OF THE GUINEA-PIG DISTAL COLON

A neuronal retrograde tracing method with the dye Dil in combination w ith the immunohistochemical detection of vasoactive intestinal polypep tide (VIP) and choline acetyltransferase (ChAT) was used to characteri se the mucosal projection of neurones located in the submucosal plexus of the guinea pig distal colon. VIP and ChAT immunoreactivity labelle d separate populations. The mucosa was innervated by descending (59.7 +/- 7.4%), ascending (8.7 +/- 5.0%) and circumferential (31.7 +/- 6.1% ) pathways. Descending neurones had longer projections than ascending ones. Descending Dil-labelled neurones were in their vast majority VIP -positive (88.4 +/- 3.6%) and only 3.5 +/- 4.8% of them were ChAT-posi tive. Conversely, the ascending pathways were predominantly ChAT-posit ive (90.9 +/- 20.3%) and only 7.8 +/- 20.6% of them were VIP-positive. A significantly larger proportion of Dil-neurones with circumferentia l projection were ChAT-than VIP-positive (70.9 +/- 15.6 vs. 27.8 +/- 1 5.7%). The proportion of ascending, descending and circumferential ChA T-positive Dil-neurones was 23:7.70%, respectively, whereas the propor tion for VIP-positive Dil-neurones was 2:84:14%, respectively. The res ults suggest a conservation of the submucosal innervation pattern alon g the guinea pig colonic mucosa but also reveal differences in the muc osal enteric innervation of other regions of the gastrointestinal trac t. (C) 1998 Elsevier Science Ireland Ltd.