Dorsal Roots of Spinal Nerves and Regulation of Skin Temperature. ∗

Abstract

Stricker 1 first showed that stimulation of the dorsal roots of spinal nerves produced a vasodilatation in peripheral blood vessels. This observation has been confirmed by Bayliss, 2 Ranson and Wightman 3 and others. Hinsey and Gasser 4 showed that the fibers mediating vasodilatation on stimulation of the dorsal roots were ones whose potentials were found in the C-spike of the action potential. Vasodilator reflexes over the dorsal roots were demonstrated in positive experiments by Bayliss 5 and Fofanov and Tschalussow. 6 Recently Bishop, Heinbecker and O'Leary 7 and Zuckerman and Ruch 8 have again obtained positive results which tend to show that the vasodilator fibers in the dorsal roots are accessible to reflex stimulation.

The observations of Hinsey and Cutting, 9 Hinsey, 10 and of Zuckerman and Ruch 8 showed that the skin temperatures in deafferented hind limbs were lower than in the opposite normally innervated limbs. These observations could either be attributed to an overaction of the vasoconstrictor pathways or to an absence of a dorsal root vasodilator mechanism in the colder limb. Zuckerman and Ruch state that when a limb is connected only with the spinal dorsal roots, it shows a different behavior than the opposite completely denervated limb (method of denervation is not stated; unless a bilateral abdominal sympathectomy was performed in addition to cutting the lumbosacral spinal roots, the denervation would not have been complete). The former fell in temperature much less than the denervated limb and usually less than the normally innervated skin. Hinsey observed that when a deafferented limb was sympathectomized, it became warmer than the opposite normally innervated limb.