Journal of Neuroscience, Vol 4, 2533-2542, Copyright © 1984 by Society for Neuroscience
Receptor autoradiography in thoracic spinal cord: correlation of neurotransmitter binding sites with sympathoadrenal neurons
VS Seybold and RP Elde
Receptor autoradiography was combined with the retrograde labeling of
sympathoadrenal neurons by fast blue to determine whether opiate,
serotonin, catecholamine, or cholinergic binding sites could be spatially
correlated with preganglionic neurons in the rat intermediolateral cell
column (IML) that project to the adrenal gland. [3H]Dihydromorphine (DHM)
was used for the visualization of mu opiate receptors, [3H]lysergic acid
diethylamide (LSD) for serotonin receptors, [3H]para-aminoclonidine (pAC)
for alpha 2-adrenergic receptors, and [3H]quinuclidinyl benzilate (QNB) for
muscarinic cholinergic receptors. While qualitative assessment of
autoradiograms indicated that alpha 2-adrenergic and muscarinic receptors
were concentrated in the intermediate zone of the spinal cord, quantitation
of grains in specific regions of the intermediate gray revealed that alpha
2-adrenergic and serotonergic receptors were more highly concentrated over
sympathoadrenal preganglionic neurons than over other regions in IML or the
adjacent intermediate gray matter. Information concerning the distribution
of neurotransmitter-binding sites in other regions of thoracic spinal cord
was also obtained. All ligands showed relatively dense binding sites in the
superficial laminae of the dorsal horn, and all but [3H]DHM revealed
similar densities of binding sites in the region adjacent to the central
canal. Only [3H]QNB revealed a high density of binding sites in the ventral
horn of the spinal cord.
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