Neurones activated from nociceptors in the spinal cord of the frog.

Neurones in the dorsal horns of the frog spinal cord were activated by innocuous (touch) and nociceptive stimuli (heat, pressure, pinch). Forty neurones which were found at depths between 300-700 microns reacted differentially, but not selectively, to various kinds of natural stimuli. The number and frequency of spikes induced by nociceptive stimuli exceeded that produced by innocuous stimuli from twice to many times. Some of the neurones were more sensitive to mechanical stimuli and others to heat. All the neurones tested could thus be classified as polymodal neurones.