Morphologic relationship between the pontine micturition center and the sympathetic center in the spinal cord of the rat.

To study whether the sympathetic nerves coordinate with the parasympathetic nerves during micturition in the rat. We used antegrade neural tracing with biotinylated dextran amine (BDA) injected into the pontine micturition center (PMC) to label the terminals in the 1.6-S1 cord. Preganglionic parasympathetic neurons (PPNs) in the L6-S1 segment were labelled by retrograde transport of Fluorogold (FG) from the major pelvic ganglion (MPG). We detected retrograde neurons in L6-S1 using retrograde transport of horseradish peroxidase (HRP) from the intermediolateral cell column (IML) of the 1,1-1,2 segment where sympathetic preganglionic neurons (SPNs) are located. Immunohistochemical methods showed that PPNs were identified to be choline acetyltransferase-immunoreactive (ChAT-IR). HRP-labelled neurons were not ChAT-IR and located dorsal to PPNs. BDA-labelled terminals were located mainly in the bilateral IML of L6-S1, some of which had synaptic contact with the HRP-labelled neurons. In addition, there were some wheat germ agglutinin-horseradish peroxidase (WGA-HRP) labelled terminals in the ipsilateral IML of the L1-L2 segment after WGA-HRP was microinjected into SPN. We conclude that PMC may control the preganglionic neurons of sympathetic nerves through the interneurons located dorsal to PPNs.