Sympathoadrenal preganglionic neurons: their distribution and relationship to chemically-coded fibers in the kitten...

The location of those sympathetic preganglionic neurons in the spinal cord that project to the adrenal medulla--the sympathoadrenal preganglionic (SAP) neurons--was studied by the method of retrograde axonal transport of the fluorescent dye Fast Blue. The distribution of chemically-coded fibers and their relationship to the SAP neurons was also investigated using the indirect immunofluorescence technique. In kittens, 5 microliters of a 1% solution of Fast Blue was injected into the medulla of the left adrenal gland. After a survival period of 5 days, the spinal cords from C8 to L5 were sectioned and processed for the localization of enkephalin-, neurophysin-, oxytocin-, serotonin-, substance P- and somatostatin-like immunoreactivity. Retrogradely labeled neurons were found in the ipsilateral intermediolateral cell column (IML) (89.8% of all retrogradely labeled neurons) from T1 to L4, and in the contralateral IML (10.2%) from T1 to L4. The enkephalin, serotonin and substance P immunoreactive fibers appeared to surround both the retrogradely labeled and unlabeled IML neurons. The somatostatin immunoreactive fibers were observed only in proximity to the retrogradely labeled neurons. Only a sparse population of neurophysin and oxytocin immunoreactive fibers were observed in IML, and were not seen to be in apposition to the retrogradely labeled neurons.