Electrotonic coupling in a network of compartmental external urethral sphincter motoneurons of Onuf's nucleus

A compartmental model of motoneurons of Onuf's nucleus, the external urethr al and anal sphincter motor nucleus, was constructed from morphological and electrophysiological data previously reported in the literature. The model neurons have active somata and initial axon segments. The dendritic trees are represented by one equivalent dendritic cylinder. These model neurons w ere used to perform network simulations. The cells in the network were mutu ally connected by dendrodendritic gap junctions, which were modeled as ohmi c resistances between two neuronal compartments. Circularly propagating wav es and extinction of meeting waves are to be expected. Increasing random in put injection will cause fastening of the network activation, which could b e related to Onuf's function. This could mean that a small continuous input to this nucleus from a higher center is only needed to cause a fast massiv e activation of the network, resulting in fast contraction of the sphincter . (C) 2001 Elsevier Science B.V. All rights reserved.