THE 3-DIMENSIONAL STRUCTURE OF MYENTERIC NEURONS IN THE GUINEA-PIG ILEUM

Myenteric neurons of the guinea-pig ileum were intracellularly filled with the fluorescent dye Lucifer Yellow, optically sectioned with a co nfocal microscope and volume reconstructed to recreate 3-D images of t he cells. The resulting images provide information not evident from re gular microscopy. The somata varied in cross-section from flat-oval to nearly circular, and their surface membranes were marked by invaginat ions and protrusions significantly increasing the surface area of the somatic membrane. The neurons could be divided into four morphological classes: Dogiel type I, Dogiel type II, filamentous, and intermediate . There was no clear correlation between cell class and the shape of t he soma in cross-section. The dendritic processes of all the neurons s tudied extended in an orad-caudad or circumferential direction of the bowel wall. When the filled neurons were viewed edge-on, the spatial a rrangement of the processes was confined to a plane that had a thickne ss less than the thickness of the parent soma. The broad, short dendri tes of Dogiel type I neurons were oval or nearly circular in cross-sec tion. Directly measured quantitative data were obtained for the volume and surface area of the somata and visible processes. The structural details reported herein are likely to have important implications rega rding the functional properties of individual enteric ganglion neurons and circuits of enteric ganglion neurons. (C) 1998 Elsevier Science B .V. All rights reserved.