Studies on the modulation of the basal and evoked release of substance P in the dorsal horn of the rat

he present study investigated whether there is a preferential release of Substance P-like immunoreactive material (SPLI) during selective activation of the A;Activation of the A;The effects of exogenously applied dynorphin (1-8) or met-enk on the basal release of SPLI as well as, the release of SPLI evoked by the application of a peripheral noxious thermal or mechanical stimulus, were also investigated in this study. The noxious cutaneous thermal or mechanical stimuli were applied to different areas of the ipsilateral hind paw and lower limb, and the collected perfusate was assayed for SPLI by RIA, as previously described. Both dynorphin (1-8) and met-enk reduced the basal release of SPLI and prevented the increase in the release of SPLI evoked by a noxious thermal or mechanical stimulus. The effect of dynorphin (1-8) was blocked by the selective...