Norepinephrine levels in traumatized spinal cord of catecholamine-depleted cats

This study was designed to elucidate the origin of norepinephrine (NE) measured in spinal cord following trauma. In normal cats the NE concentration at the lesion site increased 63% over control 1 h following experimentally produced blunt trauma (400 g-cm). Spinal cords of adrenalectomized cats were also traumatized, but there was no increase in NE levels 1 h post-trauma. Spinal cord NE levels in these animals were not significantly different from normal or adrenalectomized non-injured controls. In the absence of one of the major peripheral sources of catecholamine, the adrenal medulla, our decreased NE levels prompt us to disagree with the hypothesis that NE measured in injured spinal cord is liberated from intrinsic neuronal systems. It is likely that the mechanism of NE accumulation is directly related to increased circulating levels of NE. The authors speculate on a possible reason for the conflicting results obtained by different laboratories in this area of research.