Recovery of cutaneous vasomotor activity in the spinal dog

Vasomotor responses of the glabrous skin of the fore and hind feet of six adult female dogs subjected to thermal stress, by cooling or warming the periphery or the spinal cord, were compared in the intact and thoracic spinal animal. In the intact dog the temperature of the forefeet at a neutral ambient temperature (22°C) was higher than the hind feet. After spinal transection the hind feet were warmer than the forefeet for several days, recovering their preoperative temperature by 6.0 ± 0.89 days. The vasomotor response to cooling (13°C) and warming (45°C) one hind limb in the intact animal induced a drop or elevation respectively in the temperature of the contralateral hind foot. This reflex response to peripheral cooling was abolished for several weeks after transection but had recovered by the 29.3 ± 2.94 day. Cooling and warming of the spinal cord below the level of transection by extradurally implanted thermodes failed to induce vasomotor responses in the hind foot pads for several weeks, recovering by the 27.1 ± 3.48 day. It is concluded that whereas thermal regulation by appropriate vasomotor response to peripheral cooling and warming is influenced by supraspinal systems, the vasomotor response recovers and functions appropriately after spinal shock has subsided. This finding contrasts with the failure of spinal animals to regulate body temperature by shivering after peripheral cooling and suggests that vasomotor regulation of body temperature is a primitive thermoregulatory response.