Figure 8. Simultaneous recording of a C2 and a CMH nociceptor.

A, two fibres with CV of 1.5 m s⁻¹ and 1.3 m s⁻¹ (units C1b in Table 1 and unit C1a in Table 2). According to slowing profile during the changes to baseline stimulation frequency (0.25 Hz), the fast fibre corresponds to a type 2 (Serra et al. 1999) and the slow fibre to a mechano-heat sensitive (CMH) nociceptor. B, these two fibres responded differently to cold and heat ramps: whereas the type 2 responded readily to non-noxious cold and heat, the nociceptor responded only to noxious heat (46°C). C, when menthol was applied there was an immediate and transient response of the C2 caused by the low temperature of menthol. The nociceptor displayed only a smooth change in latency due to a general cooling effect. After 13 min of 40% menthol application, the C2 fibre started firing, while the nociceptor remained with a stable latency.