Free plasma catecholamines in spinal cord injured persons with different injury levels at rest and during exercise

Spinal cord lesion leads to an interruption of pathways from brain to the peripheral sympathetic nervous system, which results in pathological changes in sympathetic innervation. Free epinephrine (E), norepinephrine (NE) and dopamine (DA) were measured in 30 tetraplegics (TETRA), 15 high-lesion paraplegics (T1 and T4, HPARA), 15 paraplegics with injuries between T5 and T10 (MPARA), 15 low-lesion paraplegics (below T10, LPARA) and 16 non-handicapped control persons (C) at rest, at 60 and 100% of maximal oxygen consumption during graded wheelchair ergometry (WCE). The TETRA showed significant lower E and NE levels at rest and only slight increases during physical exercise. The E and NE concentrations of the paraplegics with a lesion below T5 were significantly higher than those of the high-lesion paraplegics, as well as those of the control persons at every point in the study. All paraplegics and the control persons showed, at submaximal and maximal exercise, a significant increase in NE. Only a slight increase in E in HAPRA was shown. No differences were found at rest and during exercise in E and NE levels in the MPARA and LPARA. No significant differences were found in the dopamine concentration at rest or during exercise for any of the groups. In summary, different levels of lesion and the resulting interruption to sympathetic pathways in the spinal cord are decisive factors in the degree of impairment of sympathetic innervation in SCI persons. Tetraplegics show less preganglionic resting activity because of interruption of impulses from central centers and no considerable stimulation of the sympathetic nervous system during maximal exercise. Individuals with high paraplegia have a partial impairment of catecholamine release, especially of epinephrine, at rest and during exercise. Paraplegics with a lesion level below T5 showed an augmented basal and exercise-induced upper spinal thoracic sympathetic activity in comparison to control persons.