Role of endogenous norepinephrine in microcirculation after experimental acute spinal cord injury

The effects of endogenous norepinephrine on changes in spinal microcirculation after acute injury of the spinal cord were examined in rabbits. 6-hydroxydopamine (6-OHDA), which selectively destroys catecholamine neurons, was injected into the subarachnoid cavity of the rabbit spinal cord. Measurement of the intraspinal monoamine level revealed a decrease in the intraspinal norepinephrine level in the treated animals. Recovery from motor paralysis after compression at T-8 occurred more rapidly in the treated than in untreated animals. The animals were observed with respect to 1) blood flow in the spinal cord, 2) intraspinal vascular permeability, and 3) edema of the spinal cord. In the untreated animals, vascular permeability increased and edema developed immediately after the injury. In the treated animals, however, both the increase in vascular permeability and the extent of edema were smaller. Our findings indicate that intraspinal norepinephrine plays an important role in the change of microcirculation after acute spinal cord injury.