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

Abstract

A compartmental model of motoneurons of Onuf 's nucleus, the external urethral 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 were used to perform network simulations. The cells in the network were mutually connected by dendrodendritic gap junctions, which were modeled as ohmic resistances between two neuronal compartments. Circularly propagating waves and extinction of meeting waves are to be expected. Increasing random input injection will cause fastening of the network activation, which could be 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 massive activation of the network, resulting in fast contraction of the sphincter.