Spinal cord lamina V and lamina VII interneuronal projections to sympathetic preganglionic neurons

Abstract

This light and electron microscopic study sought to localize spinal cord interneurons that contribute to the normal and abnormal physiological regulation of spinal sympathetic preganglionic function. Sympathetic preganglionic neurons in caudal C8 through T4 of rat spinal cord were retrogradely labeled with wheat germ agglutinin (WGA) and/or cholera beta subunit (CT beta) following injections into the superior cervical ganglion (SCG). With two exceptions, the observed locations of retrogradely WGA- and CT beta-labeled sympathetic preganglionic neurons were as expected from previous studies. The exceptions were restricted populations of cells in caudal C8 and rostral T1 spinal segments. These neurons were classified as ventrolateral (vlSPN) and ventromedial (vmSPN) sympathetic preganglionic neurons; their somata and dendrites encircled dorsolateral lamina IX motoneurons. Only WGA was transported transneuronally following the retrograde labeling of sympathetic preganglionic neurons. Transneuronally WGA-labeled spinal interneurons were located principally in the reticulated division of lamina V and dorsolateral lamina VII. A strict segmental organization was observed. All transneuronally labeled interneurons were ipsilateral to, and coextensive with, retrogradely WGA-labeled sympathetic preganglionic neurons. Electron microscopic observations suggested that retrograde transsynaptic passage of WGA occurred within the sympathetic preganglionic neuropil and showed further that similar classes of organelles were WGA immunoreactive in retrogradely labeled sympathetic preganglionic neurons and in transneuronally labeled lamina V and lamina VII neurons: 1) cisternae and vesicles at the trans face of the Golgi apparatus, 2) large endosomes/dense bodies, and 3) multivesicular bodies. The data are consistent with two hypotheses: 1) Somatic and visceral primary afferent inputs to thoracic spinal cord modify segmental sympathetic preganglionic function through activation of a disynaptic pathway involving lamina V and/or lamina VII interneurons, and 2) long-loop propriospinal pathways access sympathetic preganglionic neurons through symmetrical, segmental interneuronal circuitry.

Light and Electron Microscopic Studies of the Distribution of NADPH-Diaphorase in the Rat Upper Thoracic Spinal Cord with Special Reference to the Spinal Autonomic Region.

“…The present results taken together with that of TOGASHI et al (1992) suggest that the fibres may arise from interneurons in lamina V (CABOT et al, 1991(CABOT et al, , 1994 and/or supraspinal regions. In the latter, it is possible that, besides the traditional monoamine-, amino acid-and peptide-containing axon terminals in ILp, there might exist yet other supraspinal projection fibres to the ILp with NO being utilized as a neurotransmitter or neuromodulator.…”

GABAergic Neurons in the Central Region of the Spinal Cord: A Novel Substrate for Sympathetic Inhibition

“…A vast proportion of bulbospinal inputs directly innervate SPNs in the intermediolateral cell column (IML) (Anderson et al, 1989;Zagon and Smith, 1993;Pyner and Coote, 1998). However, viral trans-synaptic labeling studies have revealed many interneurons that are involved in sympathetic control in specific areas of the spinal cord, including the IML and laminas V and VII (Cabot et al, 1994;Joshi et al, 1995), and these are likely candidates for mediating indirect supraspinal control of SPN activity. Recently, putative presympathetic interneurons have also been located in the central autonomic area (CAA), dorsal and lateral to the central canal (Clarke et al, 1998;Tang et al, 2004), a region that receives input from vasomotor regions of the brain (Caverson et al, 1983;Bacon and Smith, 1993;Zagon and Smith, 1993).…”

Tracing functionally identified neurones in a multisynaptic pathway in the hamster and rat using herpes simplex virus expressing green fluorescent protein

“…86.6 organisation. Also a small number only contained HSV-1-GFP, these were not SPNs because they were smaller in size and found in the white matter of the spinal cord in a region suggested to be where interneurones are located, (Cabot et al 1991(Cabot et al , 1994Joshi et al 1995). It is interesting that LaVail et al (1993) have reported that the retrograde tracer FG interferes with the infectivity of herpes simplex virus.…”