Jb. Cabot et al., SPINAL-CORD LAMINA-V AND LAMINA-VII INTERNEURONAL PROJECTIONS TO SYMPATHETIC PREGANGLIONIC NEURONS, Journal of comparative neurology, 347(4), 1994, pp. 515-530
This light and electron microscopic study sought to localize spinal co
rd interneurons that contribute to the normal and abnormal physiologic
al regulation of spinal sympathetic preganglionic function. Sympatheti
c preganglionic neurons in caudal C8 through T4 of rat spinal cord wer
e retrogradely labeled with wheat germ agglutinin (WGA) and/or cholera
beta subunit (CT beta) following injections into the superior cervica
l ganglion (SCG). With two exceptions, the observed locations of retro
gradely WGA- and CT beta-labeled sympathetic preganglionic neurons wer
e as expected from previous studies. The exceptions were restricted po
pulations of cells in caudal C8 and rostral T1 spinal segments. These
neurons were classified as ventrolateral (vlSPN) and ventromedial (vmS
PN) sympathetic preganglionic neurons; their somata and dendrites enci
rcled dorsolateral lamina M motoneurons. Only WGA was transported tran
sneuronally following the retrograde labeling of sympathetic pregangli
onic neurons. Transneuronally WGA-labeled spinal interneurons were loc
ated principally in the reticulated division of lamina V and dorsolate
ral lamina VII. A strict segmental organization was observed. All tran
sneuronally labeled interneurons were ipsilateral to, and coextensive
with, retrogradely WGA-labeled sympathetic preganglionic neurons. Elec
tron 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 immunor
eactive in retrogradely labeled sympathetic preganglionic neurons and
in transneuronally labeled lamina V and lamina VII neurons: 1) cistern
ae and vesicles at the trans face of the Golgi apparatus, 2) large end
osomes/dense bodies, and 3) multivesicular bodies. The data are consis
tent with two hypotheses: 1) Somatic and visceral primary afferent inp
uts 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 pathw
ays access sympathetic preganglionic neurons through symmetrical, segm
ental interneuronal circuitry. (C) 1994 Wiley-Liss, Inc.