The functional anatomy of the receptive fields of rabbit C polymodal nociceptors

Abstract

1. The rabbit saphenous nerve was split into small strands to enable recording from single polymodal nociceptive C receptors. 2. The cutaneous receptive field was explored with textile fiber sized probes of diameter 20-50 microns, with buckling loads from 75 to 150 mgf. It was found that the classical 'hot spot', as defined by nylon monofilament von Frey hairs, is composed of a large number of active areas if a smaller stimulating probe is used. 3. Studies of spatial and temporal interaction established that C polymodal nociceptors respond best to slow movements and that each area of the receptive field acts independently of surrounding areas. 4. Moisture on the skin was shown to increase the discharge to a standard stimulus, probably by its softening effect on the stratum corneum. Glueing the probe to the skin showed that compressive force is not the major stimulus. 5. These results support the contention that fabric-evoked prickle is the result of individual stiff fabric hairs exceeding nociceptor threshold at their point of contact with the skin rather than some complex interaction of fabric properties.