Direct projection from the lumbosacral spinal cord to spinally- projecting neurons in Barrington's nucleus: an electron microscopic study in the rat

An electron microscopic experiment was performed to examine if spinally projecting neurons in Barrington's nucleus receive direct projection from the lumbosacral spinal cord following injection of biotinylated dextran amine (BDA) into the lumbosacral spinal cord in the rat. Consistent with previous study, at light microscopic level, numerous anterogradely labeled axon terminals and some retrogradely labeled cell bodies were seen in Barrington's nucleus after injection of BDA into the lumbosacral spinal cord. Electron microscopic observations showed that some BDA labeled axon terminals made synaptic contact with dendrites labeled with BDA. The present results indicate that Barrington's nucleus receives direct afferents from the lumbosacral spinal cord, and suggest that there may be a direct ascending pathway from the lumbosacral spinal cord to Barrington's nucleus in the pontine micurition reflex of the rat. \[