Norepinephrine levels in experimental spinal cord trauma

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Abstract
.alpha.-Methyl tyrosine (AMT) or reserpine administered i.v. 24 h before sacrifice in the nontraumatized cat resulted in significant reduction in tissue levels of norepinephrine (NE) tested at the T-5 spinal cord level. Phenoxybenzamine given 2 h before sacrifice did not alter NE levels at T-5. Histological sections of spinal cord examined 1 h after a 500 gm-cm trauma at the T-5 level in cats, pretreated 24 h before trauma by a single dose of AMT or reserpine, demonstrated no reduction of gray or white matter hemorrhages when compared to controls. In cats pretreated with phenoxybenzamine 2 h before trauma there was a marked reduction of hemorrhages at 1 h posttrauma when compared to controls. The animals treated with phenoxybenzamine had a 32% reduction of systemic blood pressure before trauma, demonstrated no pressor response to spinal cord trauma and were severely hypotensive posttrauma. Posttraumatic blood pressure apparently has greater etiological significance in the pathogenesis of experimental spinal cord hemorrhages than tissue levels of NE.
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