Studies of Origins of Neurons in Medulla that Project to the Lumbosacral Spinal Cord of the Cat

요천수에 투사하는 연수 신경세포들의 분포

Spinal parasympathetic outflows originate in the sacral parasympathetic nuclei. The sacral parasympathetic nuclei receive inputs from the brainstem. Many areas in the medulla appear to influence sympathetic outflow of the spinal cord. Whether neurons in these areas of the medulla may project to the lumbosacral cord to affect the parasympathetic outflow has not been studied clearly. Thus, this study was intended to investigate origins of cells projecting from the medulla to the sacral parasympathetic nuclei of the spinal cord. In 3 cats, horseradish peroxidase (HRP) was injected into the lower lumbar spinal cord. HRP labeled neurons were found mainly in the following areas: nucleus retroambiguus, nucleus tractus solitarius, raphe complex and ventrolateral area of the rostral medulla. Most of these areas are known to be involved in regulation of sympathetic activity, and, thus, these results indicate that these areas are likely to affect the sacral parasympathetic outflow as they do for the sympathetic nerves.