NOCICEPTIVE AND REFLEXIVE RESPONSES RECORDED FROM THE HUMAN NASAL-MUCOSA

Slow electrical responses after painful stimulation with carbon dioxid e, which is known to specifically activate nociceptors, were recorded from the nasal respiratory epithelium in human volunteers. The negativ e component of these potentials (negative mucosal potential NMP) has b een hypothesized to be a summated receptor potential. The aim of the p resent study was to characterize the stimulus-response relationship an d to demonstrate that the NMP is restricted to the site of stimulation , i.e., to the area of activated nociceptors. Eight healthy volunteers participated in the experiments. The NMP was recorded from the nasal septum and intensity ratings were obtained for each of the applied sti muli. To control for autonomic reflexes, blood flow changes were addit ionally recorded using a laser Doppler flow meter. Both increasing sti mulus duration and increasing concentration produced a significant inc rease in the subjects' intensity estimates, in the NMP's amplitudes an d areas under the curve, but did net change the local blood flow in a dose-related manner. The odorant hydrogen sulphide, which was used as a non-painful control stimulus, did not elicit mucosal potentials or p roduce blood flow changes. By recording both ipsi- and contralaterally it was also demonstrated that the NMP could only be obtained at the s timulated site, thus supporting the hypothesis that the NMP is a speci fic peripheral nociceptive correlate.