Myenteric neurons with different projections have different dendritic tree patterns: a morphometric study in the pig ileum.

Morphometric analysis was performed of two types of myenteric neurons with at first glance, very similar morphology, but different projections in the pig ileum. 50 type IV cells projecting vertically to the outer submucosal plexus, and 50 solitary type V neurons projecting aborally, within the myenteric plexus, were evaluated. Using a computer-aided morphometric device, the following parameters were recorded: somal area, longest somal diameter, number of primary dendrites, dendritic length, number of dendritic branching points and number of terminal segments. In addition to other significant differences, the most prominent discriminating parameter between the two populations of nerve cells estimated in this study was the length of the longest dendrite of each cell type. The longest dendrite of an individual type V neuron is a manifold longer than the corresponding somal diameter, in contrast to type IV neurons where it is at most twice the somal diameter. In addition, all type IV and type V single dendritic lengths were arranged in histogramms, where the type V dendrites showed two frequency peaks. Thus, we assume that solitary type V neurons can develop two populations of dendrites: a short and a long one. These results demonstrate that myenteric neurons with different projections (and hence different functions) display strikingly different dendritic morphology.