Sensitization and habituation of the plantar cushion reflex in cats.

The plantar cushion reflex in cats was examined as a model system in a mammal for the study of the effects of repeated stimulation on neural transmission. Effects of various frequencies and intensities of stimulation were similar to those seen in other reflex systems. For instance, for a fixed number of stimuli, habituation of the plantar cushion reflex was more marked at 10 Hz than at 2.0 Hz, and with 1.0 X threshold stimulation than with 5.0 X threshold stimulation. Sensitization occurred at intermediate intensities and frequencies of stimulation. Dorsal root potentials were studied; changes in dorsal root potentials during iterated stimulation did not correlate with the changes in the plantar cushion reflex. These changes in the plantar cushion reflex were also unrelated to variations in afferent transmission peripheral to the spinal cord. Sensitization and habituation in the plantar cushion reflex occurred during iterated stimulation, were produced centrally, and were unrelated to mechanisms of presynaptic inhibition.