The synthesis and metabolism of catecholamines in the spinal cord of the rat after acute and chronic transections.

The capacity of the spinal cord of the rat to synthesize and metabolize catecholamines from injected L-DOPA, was tested at 10 and 100 days after a middle thoracic transection of the cord. There was no indication of even a minimal recovery of the capacity to synthesize noradrenaline in the caudal region of the transected cord. At 10 days after transection, the lumbar cord could synthesize 50% of the dopamine formed in the intact cord. At 100 days after transection the synthesis of dopamine in the transected cord was equal to that in the intact control animal. At both 10 and 100 days after transection, the dopamine synthesized from L-DOPA was efficiently metabolized to dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). As judged from the levels of gamma-aminobutyric acid (GABA) and glutamic acid (glutamate) present in the transected cord, no major metabolic derangement of the spinal cord tissue seemed to have been present at the times the experiments were done. It is concluded that dopamine can be efficiently synthesized and metabolized from its immediate precursor, L-DOPA, even in the absence of monoaminergic nerves. The results are discussed with reference to two main themes. The first, is the likelihood that in the therapeutic use of L-DOPA in states of chronic dopaminergic nerve degeneration (e.g. Parkinson's disease), the synthesis and metabolism of dopamine probably occurs throughout the entire central nervous system. The second, is the possible usefulness of L-DOPA to test for the relative intactness of spinal reflex circuities in the chronically spinalized animal.