DIRECT PROJECTIONS FROM PONTINE DORSOLATERAL TEGMENTUM TO THE SACRAL SPINAL CORD IN THE RABBIT

To obtain morphological data concerning pontine micturition reflex in the rabbit, the fiber connection between the pontine dorsolateral tegmentum and sacral spinal cord were examined by using retrograde and anterograde tract tracing techniques combined with immunohistochemistry.After injection of a wheat germ agglutinin horseradish peroxidase(WGA HRP) or a fluorescence tracer, tetra methylrhodamine dextran amine(TMR),into the sacral spinal cord segments,a cluster of neurons labeled with WGA HRP or TMR were seen in the pontine dorsolateral tegmentum.To identify whether the retrogradely labeled neurons belong to the locus coeruleus,the sections containing many TMR labeled neurons through the pons were incubated with anti tyrosine hydroxylase (TH) antibody and observed under epifluorescence microscope. It was shown that a cluster of TMR labeled neurons in the dorsolateral tegmentum were surrounded by TH positive neurons,but no one showed TH like immunoreactivity.In anterograde experiment,injection of WGA HRP into the dorsolateral tegmentum resulted in many anterogradely labeled nerve fibers and terminals in the sacral spinal cord,including the sacral parasympathetic nucleus,intermediate gray and dorsal commissural nucleus.Together with the findings obtained in the other species,it may be concluded that the cluster of neurons in the dorsolateral tegmentum of the rabbit corresponds to Barrington nucleus revealed in the rat and cat,and thus may be involved in micturition activity.