How does intermittent painful intraneural microstimulation affect cutaneous thermal emission profiles in normal human volunteers?
Sympathetic vasoconstriction overrides C nociceptor-induced antidromic vasodilatation, highlighting the need to consider the dynamic interplay between sympathetic and somatic systems when interpreting skin temperature deviations.
The interaction between orthodromic sympathetic vasoconstrictor and antidromic vasodilator effects of C-fiber stimulation was studied in normal human volunteers. Excitation of C fibers was achieved through administration of intermittent painful intraneural microstimulation to upper limb nerves, while recording cutaneous thermal emission profiles in the projected fields of cutaneous sensation. During initial stimulation, when both systems are co-activated, skin temperature decreased. Temperature increased after termination of the stimulus. Eventually, temperature decreased again upon renewed stimulation. Thus, sympathetic vasoconstriction was found to override the antidromic vasodilator effect induced by stimulation of C nociceptors. When interpreting abnormal deviations of skin temperature in patients with peripheral nerve disorders, the dynamic interplay between opposing vasomotor effects driven by sympathetic and somatic systems must be taken into consideration.
Ochoa et al. (Sun,) studied this question.