Parallels between properties of high-threshold mechanoreceptors of the goat oral mucosa and human pain report.

In the following experiments, we examined parallels between properties of A-delta high-threshold mechanoreceptors (HTMs; mechanonociceptors, MN, and intense pressure receptors, IPR) innervating the goat mucosa and human mucosal pain report. As suggested in previous studies, activation thresholds of afferents which are generally considered to be mechanical nociceptors are far below mechanical pain thresholds. It was determined that classification of nociceptors by frequency thresholds, i.e., the pressure at which HTMs maintained a minimum frequency (97 g/mm2 and 117 g/mm2 for IPRs and MNs respectively) brings afferent reactivity into alignment with perceptual events. The range of reactivity of the nociceptor pool paralleled pain report from "faint-weak" (142 g/mm2) to "strong-intense" (277 g/mm2). It is suggested that coding of intense mechanical pain from compressive forces is likely to arise from both individual afferents, whose reactivity spanned the range, and from recruitment of afferent populations with progressively higher thresholds.