[Changes in the skin receptor responses to their repeated heat stimulation]

It is known that cooling of skin induces contraction of collagen fibres, which leads to deformation and excitation of mechanoreceptors. The action of moderate heat on the skin depresses or terminates its tonic activity. The collagen fibres in this case stretch out and the skin tension slackens. Yet, intense thermal stimulation up to 48 degrees C results in a greater afferent activity. This effect is associated with the so-called thermoreceptors. It is shown earlier that repeated stimulation by intense heat increases skin sensitivity to this stimulus. The paper reports the results of recording the time in which afferent activity increased under repeated stimulation of the skin at temperatures up to 48 degrees C and, simultaneously, of the skin tension variations. For each heating instance the skin stretched and contracted when its temperature approached the normal temperature, i. e. 30 degrees C. However, by the next heating (there was a 3--min. pause between them) the skin tension failed to restore completely. Multiple heating tests have shown a loss of the skin sensitivity, and the time in which increased afferent activity manifested itself has shortened. These two processes are simultaneous, which permits concluding that they are related.