Adrenomedullary ornithine decarboxylase activity: its use in biochemical mapping of the origins of the splanchnic nerve in the rat.

The activity of ornithine decarboxylase in the adrenal medulla of the rat can be induced transsynaptically by the repeated administration of apomorphine. Unilateral section of one to four ventral spinal cord roots from T4 to T12 partially prevents this effects. Interruption of the intercostal nerves (T7--T13), with preservation of the autonomic innervation of the adrenal medulla, does not produce any alteration in the response of the medullary ODC to APO in the operated side as compared to the intact side. Dorsal root section at T7--T10 leads to a small reduction, while section at T2--T4 has no effect at all. Thus, selective surgical interruption of spinal cord roots indicates that the bulk of splanchnic fibers mediating the transsynaptic induction of adrenomedullary ornithine decarboxylase course in the ventral roots between T7 and T10. Dorsal rhizotomy demonstrates a modulatory role in this induction of afferent information to sympathoadrenal preganglionic neurons involved in innervation of the chromaffin cells.