Norepinephrine levels in experimental spinal cord trauma. Part 2: Histopathological study of hemorrhagic necrosis.

Alpha methyl tyrosine (AMT) or reserpine administered intravenously 24 hours before sacrificed 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 hours before sacrifice did not alter NE levels at T-5. Histological sections of spinal cord examined 1 hour after a 500-gm-cm trauma at the T-5 level in cats, pretreated 24 hours before trauma by a single dose of AMT or reserpine demonstrated no reduction of gray or white matter hemorrhages when compared tocontrols. In cats pretreated with phenoxybenzamine 2 hours before trauma there was a marked reduction of hemorrhages at 1 hour 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. It is concluded that posttraumatic blood pressure has greater etiological significance in the pathogenesis of experimental spinal cord hemorrhages than tissue levels of NE.