CHANGES IN EXCITABILITY OF HUMAN CUTANEOUS AFFERENTS FOLLOWING PROLONGED HIGH-FREQUENCY STIMULATION

摘要: Prolonged high-frequency stimulation of cutaneous nerves can result in paraesthesiate that begin 20 to 30 s after the end train and last for 5 10 min In present experiments effects such on excitability human afferents their refractory supernormal periods were measured determine whether these changes could explain postactivation paraesthesiae. Attention was focused axons lowest threshold (1.0–1.5 T) compound sensory action potential evoked by stimulating digital index or middle fingers. Repetitive activation produced two opposing low-threshold afferents. Following stimulus trains short duration (1–5 min) dominant effect a long-lasting decrease excitability, amplitude test afferent volley always less than before With trains, no subject experienced paraesthesiate. For lasting longer 7 12 an increase greater stimulation. Within this interval, following subjects The extent supernormality induced supramaximal conditioning greatly increased 1 min. min, degree enhanced much same as stimulation, but inappropriately high size volley. sum total change resulted larger lasted It is concluded axonal predispose most excitable generate ectopic impulses and, thereby, produce