A neurochemical analysis of the interaction of afferent signals at the spinal cord level]

The antinociceptive effect of electrical nerve stimulation with low (2-4 V, 100 Hz, 5 min) and high (45 V, 1 Hz, 1 min) intensity in the unanesthetized rats with the transsected spinal cord was determined by microelectrode recording in the ventrolateral tracts. The action of low intensity stimulation was reduced by yohimbine or during antinociceptive effect of clonidine. It was potentiated by baclofen and physostigmine. Prazosin, bicuculline, methysergid, strychnin, atropine, muscimole, THIP did not influence the effect of low-intensity stimulation. Metysergide partially reduced the effect of high-intensity stimulation. The data suggest that 2-adrenoreceptors are involved in the action of low-intensity stimulation and 5-HT-receptors are involved in the action of high-intensity one. For potentiating the effect of low-intensity stimulation on the segmental level it is possible to use baclofen and physostigmine.