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Decreased Uptake and Release of D‐Aspartate in the Guinea Pig Spinal Cord After Dorsal Root Section
Author(s) -
Potashner S. J.,
Tran P. L.
Publication year - 1984
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1984.tb12722.x
Subject(s) - spinal cord , anatomy , fasciculus , lesion , gabaergic , dorsum , chemistry , stimulation , biology , inhibitory postsynaptic potential , endocrinology , white matter , neuroscience , pathology , medicine , fractional anisotropy , radiology , magnetic resonance imaging
This study attempts to determine if L‐gluta‐mate and/or L‐aspartate may be transmitters of dorsal sensory neurons. The uptake and the electrically evoked release of D‐[ 3 H]aspartate, a putative marker for L‐glu‐tamate and L‐aspartate, were measured in the cervical enlargement (segments C4‐T1) of the guinea pig spinal cord before and after cutting dorsal roots C5‐T1 on the right side. The uptake and the release of γ‐aminobutyric acid (GABA) also were measured as indices of the integrity of GABAergic neurons in the spinal cord. The cervical enlargement was excised and divided into left and right halves, then into dorsal and ventral quadrants. Quadrants from unlesioned animals took up D‐aspartate and GABA, achieving concentrations in the tissues which were 14‐25 times that in the medium. Subsequently, electrical stimulation evoked a Ca 2+ ‐dependent release of D‐aspartate and of GABA. The uptake and release of D‐aspartate and GABA were similar in tissues taken from intact and sham‐operated animals. However, dorsal rhi‐zotomy, without damage to dorsal radicular or spinal blood vessels, depressed the uptake (by 22‐29%) and the release (by 50%) of D‐aspartate only in quadrants ipsilat‐eral to the lesion. The uptake and the release of GABA were unchanged. In transverse sections of the cervical enlargement, stained to reveal degenerating fibers, by far the heaviest loss of axons occurred in the cuneate fasciculus and in the gray matter ipsilateral to the cut dorsal roots. These findings suggest that the synaptic endings of dorsal sensory neurons probably mediate the uptake and the release of D‐aspartate and, therefore, may use L‐glu‐tamate or L‐aspartate as a transmitter. When spinal blood vessels were damaged during dorsal rhizotomy, the deficits in D‐aspartate uptake and release were larger than those in the absence of vascular damage and were accompanied by deficits in GABA uptake and release. These findings imply that vascular damage results in the loss of intraspinal neurons, some of which probably mediate the uptake and release of D‐aspartate and, therefore, may use L‐glutamate and/or L‐aspartate as a transmitter.