Figure 5: C-MIAs are vigorously activated by histamine and capsaicin.
From: Three functionally distinct classes of C-fibre nociceptors in primates

(a) Intradermal injection of histamine produced a significantly greater net response in C-MIAs than in CMHs (*P<0.05, Mann–Whitney U-test). Dashed line indicates net response of 10 APs in 5 min. (b) In C-MIAs tested with both histamine and capsaicin (filled circles, n=11), capsaicin responses were larger than the responses to histamine. Open circles indicate C-MIAs only tested with one agent. Inset: When only fibres that fulfil the response criteria were included, the average histamine- and capsaicin-evoked response did not differ. (c) Histograms of instantaneous frequencies of histamine responses in CMHs (blue columns) and C-MIAs (grey columns) and capsaicin responses in C-MIAs (red columns). All trials resulting in a response were included in the analysis. Bins are in log increments (factor √2). Error bars indicate s.e.m. Data are from cynomolgus and pigtail monkeys.