Segmental regulation pattern of body surface temperature in the rat hindlimb.

Body surface zones or 'thermatomes', whose temperature is regulated by a single spinal segment, were investigated by thermography in the rat hindlimb. First, the spatial relation between the dermatome delineated by dye extravasation and the corresponding thermatome was investigated in rats pretreated with intravenous application of Evans blue. Electrical stimulation of the spinal nerves and sympathetic trunk segments at L3 and L5 induced a distal dominant temperature decrease. In contrast, Evans blue extravasation appeared in the medial (in L3) and lateral (in L5) paw only by electrical stimulation of the spinal nerves. Second, thermatomes L1-L5 were determined in other rats. Electrical stimulation of the sympathetic trunk segments L1-L6 produced a temperature decrease in the abdomen, hindlimb, and tail. However, the hindlimb temperature was regulated mainly by L2-L5 levels, particularly by L4 and L5. The abdomen was regulated uniformly by L1-L6, and the tail by L6. It was demonstrated that thermatomes are manifested differently from the corresponding dermatomes in the rat hindlimb.