Differentiation of sympathetic activity at the spinal level in Response to central cold stimulation

Summary Thermally induced adjustments of skin blood flow in chronically spinalized dogs may occur without alterations of arterial pressure and heart rate. In lightly anesthetized rabbits with chronic spinal transection at the level of C₆/C₇, the question was investigated, whether the isolated spinal cord can produce differentiated changes of regional sympathetic activity as a response to central cold stimulation.Selective cooling of the thoraco-lumbar spinal cord in chronically spinalized rabbits induced an increase in vasoconstrictor tone of the ear skin vessels as indicated by a drop of ear skin temperature at constant core and ambient air temperatures. Simultaneously, a decrease of activity in a splanchnic nerve branch was observed. Arterial pressure and heart rate remained unaffected on the average. 24 h after spinal transection, this response seemed to be less pronounced than 3 or more days after the operation. The presented results show that the pattern of regional vasomotor responses induced by central cold stimulation is, on principle, identical in intact and chronically spinalized rabbits. Therefore, the vasomotor pattern described in spinalized animals seems to represent a thermoregulatory response mediated by a vicarious spinal control system.