Thermoregulatory and rhythm‐generating mechanisms governing the sudomotor and vasoconstrictor outflow in human cutaneous nerves.

Abstract

SUMMARY1. Recordings of multiunit sympathetic activity were made from human nerve fascicles supplying hairy and glabrous skin of the extremities in healthy subjects exposed to different ambient temperatures. Sudomotor and vasomotor events accompanying the neural activity were monitored by simultaneous recordings of electrodermal and pulse plethysmographic events (Pleth) in the neural innervation zones.2. By exposing the subject to warm (43 00) or cold (15 00) environments, it was possible to obtain a selective activation of either the sudomotor or the vasoconstrictor neural system, respectively, with suppression of spontaneous activity in the other system.3. Bursts of both vasoconstrictor and sudomotor nerve activity were found to occur at certain preferred intervals which were integer multiples of a period of about 0-6 sec (100 cycles/min). With high sudomotor or vasoconstrictor tone the 100 cycles/ min rhythm was prominent but with decreasing tone slower subharmonic rhythms prevailed. Respiratory rhythms were also discerned as well as slower rhythms attributable to oscillatory tendencies in thermoregulatory servos.4. Vasoconstrictor bursts had longer mean duration than sudomotor bursts, a finding attributed to a slower conduction velocity of vasoconstrictor as compared to sudomotor impulses.

Regional similarities and differences in thermoregulatory vaso‐ and sudomotor tone.

“…Care was taken to ascertain that neither in the input stages nor in the tape recorder there was any significant 'cross-talk' between the two micro-electrode recording channels. Since a previous study dealt with the correlation between the neural sympathetic activity and the accompanying electrodermal and plethysmographic events (Bini et al 1980) only the mean voltage ('integrated') neurograms are shown in the present paper (with omission of electrodermal and plethysmographic recordings). The double nerve recording sites could often be maintained for several hours.…”

“…The double nerve recording sites could often be maintained for several hours. Unless otherwise stated the subject was resting in a comfortable position while the environmental temperature was changed in the ways previously described (Bini et al 1980). When the subject was lying inside the hypothermia box the arm on which the recordings were made passed through an opening in the box and was (from the axillary region) exposed to a constant room temperature of 22-24 0C.…”

Microneurographic findings in diabetic polyneuropathy with special reference to sympathetic nerve activity

“…In addition, inspiratory and arousal stimuli are usually followed by a strong burst of skin nerve sympathetic activity. Emotional stress may evoke repeated bursts [1,8,17]. The evidence for the sympathetic nature of these activities has been summarized by Vallbo et al [33].…”

Sympathetic nerve activity in the skin in relation to vibration-induced white finger.

“…The two types of fibers are intermingled, and it is difficult to record pure vasoconstrictor impulses isolated from sudom otor impulses. Changing the environmental temperature makes it possible to obtain a selective activa- tion of vasoconstrictor impulses only (9). In oth er words, with a lower ambient temperature, the vasoconstrictor impulses become more dom inan t becau se the sudomotor impulses are suppressed.…”