INFLUENCE OF AN EXPERIMENTAL PERIPHERAL MONONEUROPATHY ON THE RESPONSES OF MEDIAL BULBORETICULAR NEURONS TO NOXIOUS SKIN STIMULATION AND THE MODULATION OF THE RESPONSES BY AN ALPHA(2)-ADRENOCEPTOR AGONIST IN THE RAT

A peripheral mononeuropathy was induced in rats by the placement of four loose ligatures around the right sciatic nerve. After the development of mechanical hyperalgesia in the neuropathic limb, the responses of medial bulboreticular neurons to noxious skin stimulation were determined, and the attenuation of the responses was attempted by administering systemically medetomidine, a highly specific α2-adrenoceptor agonist. The neuronal responses to noxious stimulation of the sciatic nerve area or the saphenous nerve area in the hyperalgesic limb were of a magnitude equal to that of the responses from the corresponding areas in the intact limb of neuropathic or control rats. Also the spontaneous activity of bulboreticular neurons in neuropathic rats was of a magnitude equal to that in intact rats. The dose-dependent (50-200 μg/kg) suppression of the evoked responses by medetomidine was equal in intact and neuropathic animals. It is concluded that the medial bulboreticular neurons are not involved in the development of hyperalgesia in rats with an experimental mononeuropathy. © 1993 by Academic Press, Inc.