ULTRASTRUCTURAL EVIDENCE FOR A DIRECT PATHWAY FROM THE PONTINE MICTURITION CENTER TO THE PARASYMPATHETIC PREGANGLIONIC MOTONEURONS OF THE BLADDER OF THE CAT

Light microscopy tracing studies have provided evidence that the ponti ne micturition center (PMC) projects to the area of the intermediolate ral cell column of the sacral spinal cord. Although this region contai ns parasympathetic preganglionic motoneurons of the bladder and colon, it also contains many local interneurons and neurons projecting to su praspinal levels. The present study demonstrates that neurons in the P MC indeed project to preganglionic bladder motoneurons. Wheat germ agg lutinin horseradish peroxidase was injected in the PMC and cholera tox in B subunit was injected in the bladder wall. Many anterogradely labe led fibers from the PMC were found to terminate on somata and dendrite s of the retrogradely labeled preganglionic bladder motoneurons. The t erminals were filled with many round vesicles and possessed an asymmet ric synaptic cleft, suggesting an excitatory function. (C) 1997 Elsevi er Science Ireland Ltd.