[The influence of anticipation of pain on heart and respiratory rates and on the pain reflex in man].

A study was undertaken in man to determine the effects of anticipation of pain on the heart rate, respiratory rhythm and nociceptive component of the flexor reflex. Two groups of subjects were used: a group of trained subjects and a group of naive ones. A warning, given 10 min before the delivery of the painful stimulation, made the naive subjects anxious while the trained ones remained relaxed. The latter subjects showed a steady heart rate and respiratory frequency as well as a steady level in the nociceptive reflex threshold for the duration of the experiment. Two kinds of responses were exhibited by the naive subjects: one group showed increased heart rate and respiratory frequency as well as an initial increase in the reflex threshold; the other group showed decreased heart rate, increased respiratory frequency and an initial decrease in the reflex threshold. In each sub-group of the naive subjects, the time course of the reflex threshold showed a progressive evolution towards the threshold level of the trained subjects with a time course of 30--40 min.