SKIN BLOOD-FLOW DISTURBANCES IN THE CONTRALATERAL LIMB IN A PERIPHERAL MONONEUROPATHY IN THE RAT

Electrical excitation of nociceptive afferents in an extremity has bee n demonstrated to increase skin blood flow in the contralateral extrem ity. Hence, one would expect that loose sciatic nerve ligation, which induces an experimental painful peripheral neuropathy, may also provok e a vasodilator response in the contralateral hindpaw. On the non-liga ted side, such a response may involve inhibited skin vasoconstrictor a ctivity as well as neurogenically mediated active vasodilation. We stu died skin blood flow changes in the rat hindpaw consequent to contrala teral loose sciatic nerve ligation. After ligation, we also investigat ed whether blockade of afferent input from the ligated sciatic nerve t o the spinal cord, by means of lidocaine, overrules the vasodilator re sponse in the non-ligated paw. On the non-ligated side, we assessed th e vasoconstrictor response of skin microvessels to cooling of the rat abdomen as a measure of skin vasoconstrictor activity in this paw. In order to investigate the involvement of sensory and/or non-sensory ner ve fibers in the non-ligated sciatic nerve on skin blood flow abnormal ities in the non-ligated paw, we studied the influence of blockade of these fibers through successive capsaicin and lidocaine application. W e show that loose ligation of the sciatic nerve induces a vasodilator response in the contralateral hindpaw, which is completely abolished b y blockade of afferent input From the ligated sciatic nerve. From day 1 after ligation, skin vasoconstrictor activity in the non-ligated paw was reduced, as indicated by an impaired vasoconstrictor response to cooling of the rat abdomen. Besides, blockade of sensory but not of no n-sensory nerve fibers on the non-ligated side attenuated the vasodila tor response in this paw. The data presented here indicate that loose ligation of the rat sciatic nerve induces a vasodilator response in th e contralateral hindpaw. On the non-ligated side, this vasodilator res ponse may involve inhibition of skin vasoconstrictor activity, as well as antidromically acting sensory nerve fibers. Copyright (C) 1996 IBR O.