Skip to main content
. 2019 Oct;11:125–146. doi: 10.1016/j.cophys.2019.10.005

Figure 2.

Figure 2

(a) Percentages of nociceptors with superficial RFs that are PMNs. This is high (79%) for C-nociceptors, decreasing through Aδ (average ∼14%) to almost none (∼3%) of Aαβ-nociceptors.

(b) Percentage contribution of PMNs to all neurons. The vast majority of PMNs were C-nociceptors with superficial RFs. None with deep RFs and no A-nociceptors with dermal RFs showed responses to noxious heat.

(c) IB4 relative immuno-intensities relative to C-nociceptor subtypes. This includes only units in this Bristol data set. It is a different plot of data most of which were previously published [26]. Here, the limits are defined more precisely, in that deep HTMRs and unresponsive units are included only if comprehensively tested with all types of noxious mechanical and noxious thermal stimuli, except for open symbols in CM deep that were not heat tested.

The grey bands of 0–20% indicate negativity for IB4, 20–40% indicates weak staining, and 60–100% indicates strong staining. Note the gap in the CUnr (C-unresponsive) units between 40–70% suggesting two possible groups, strongly IB4+ and negative or weakly IB4+. Also note the IB4+ CMH and IB4− CMC units. Dermal and deep HTMRs were mostly negative to medium but not very strong IB4-immunointensities.

(d) trkA versus IB4-immunointensities in C-Unresponsive neurons: All these neurons are from this Bristol database, and each had immunocytochemistry for trkA and IB4 carried out on different sections of the same neuron.

(e–g) A-fiber HTMRs and MPRs.

(e) Incidence of A-fiber HTMRs and MPRs with superficial RFs. For definitions see Sections: A-fiber PMNs and Moderate pressure receptors. MPRs are nociceptors that fire in response to moderate, non-noxious, pressure, but fire faster to higher intensity mechanical stimuli, encoding intensity through the noxious range [12••]. High threshold mechanoreceptors (HTMRs) are nociceptors with higher mechanical thresholds than MPRs that do not respond, or respond poorly, to moderate pressure.

(f) MPRs as a percentage of A-nociceptors with superficial RFs. This increases with CV, being low (15%) in the Aδ-range, and rising to 49% in the Aαβ-range especially above 16 m/s (log 1.2) when the incidence is declining. NB All MPRs had superficial RFs.

(g) Aβ-MPRs and HTMRs: trkA versus CV and RF depth. Redrawn from Fang et al. [9]. In Aαβ-nociceptors: MPRs have the fastest CVs and lowest trkA-expression. trkA-expression was highest in nociceptors with dermal or deep RFs, was next highest in nociceptors with superficial RFs and lowest in MPRs.