Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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The influence of stimulus temperature rise rate (2.5 degrees C/s, 5.0 degrees C/s, and 10.0 degrees C/s), adapting (baseline) temperature (25 degrees C, 30 degrees C, and 35 degrees C), and duration of peak stimulus temperature (1.0 s, 2.5 s, 5.0 s, and 10.0 s) on responses evoked by noxious heat stimuli of suprathreshold intensity was studied in wide dynamic range (WDR) neurons of the rat spinal dorsal horn. The spinal neuronal responses were compared with human psychophysical data obtained using the same stimuli. Noxious heat stimuli with a peak temperature of 54 degrees C were applied with a contact thermostimulator to the glabrous skin of the hindfoot in rats or to the palmar skin in humans. ⋯ The changes in the total impulse counts evoked by varying supraliminal heat stimuli in spinal dorsal horn WDR neurons corresponded well with the changes in pain magnitude estimates in humans. Also, the changes in spinal neuronal response onset latencies were accompanied by corresponding changes in onset latencies of human pain reactions but not with pain magnitude estimates. The effect of spinalization indicated that descending pathways control not only the response magnitude in the spinal dorsal horn WDR neurons but also the temporal characteristics of the spinal neuronal response.