Somatosensory cortex stimulation-evoked analgesia in rats: potentiation by NO synthase inhibition

Clinical and immunohistochemical evidence suggests the possible significance of electrical stimulation of the secondary somatosensory cortex (S-II) as an analgesic therapy. The aim of the present study was to gain behavioral evidence for S-II stimulation-induced antinociception in conscious rats and to evaluate if the evoked antinociception can be potentiated by the neuronal NO synthase inhibitor 7-nitro-indazole. S-II stimulation produced a weak antinociception in the formalin-induced nociception test, but not in the thermal or mechanical nociception tests. This effect was remarkably potentiated by systemic administration of 7-nitro-indazole at a small dose that had no effect by itself. Thus, our data provide behavioral evidence for S-II stimulation-induced analgesia and may also predict a novel therapeutic strategy in combination with NO synthase inhibitors.