General Characteristics of Sympathetic Activity in Human Muscle Nerves

Abstract

DELIUS, W., K.-E. HAGBARTH, A. HONGELL and B. G. WALLIN. General characteristics of sympathetic activity in h u m a n muscle nerves. Acta physiol. scand. 1972. 84. 65-81.Multiunit sympathetic activity was recorded from muscle nerve fascicles in the median or peroneal nerve of resting, relaxed human subjects. The impulses, which were reversibly abolished by a sympathetic ganglion blocking agent, were grouped in the pulse rhythm, and series of such pulse rhythmic bursts of impulses regularly appeared during spontaneously occurring blood pressure reductions, whereas temporary blood pressure elevations were associated with neural silence. The findings agree with the notion that the sympathetic muscle nerve activity recorded consists of vasoconstrictor impulses, the outflow of which is modulated by a strong phasic and tonic inhibitory baroreflex influence. The reflex delay from an arterial pulse wave to the corresponding inhibition of efferent sympathetic activity was 0.9-1.4 seconds, depending on the recording site. Several stimuli, such as sudden chest compression, a rapid deep breath or an electrical shock against the skin, caused a transient inhibition of the sympathetic discharges lasting a few seconds.

Carotid Baroreceptor Stimulation, Sympathetic Activity, Baroreflex Function, and Blood Pressure in Hypertensive Patients

“…The method determines sympathetic vasomotor tone in human subjects. 20,21 Electric baroreflex stimulation rapidly decreased MSNA and blood pressure. A similar response was observed previously in 4 patients in whom baroreflex afferent nerves were directly stimulated.…”

Effect of facial cooling and cold air inhalation on sympathetic nerve activity in men

“…When a muscle nerve fascicle had been identified by electrical stimulation through the microelectrodes, small adjustments of the intraneural electrode were made until MSNA was encountered. The criteria for an adequate recording of MSNA were the following: (1) electrical stimulation through the intraneural electrode elicited involuntary muscle contractions but not cutaneous paresthesia, (2) stretching the muscle innervated by the impaled fascicle elicited afferent mechanoreceptor discharges, but slight tactile stimuli within the distribution area did not evoke afferent impulses, (3) Valsalva manoeuvre but not arousal stimuli increased burst frequency and (4) the spontaneous activity occurred in intermittent and pulse synchronous bursts (Delius et al, 1972;Vallbo et al, 1979). The nerve signals underwent amplification (50 000 times), bandpass filtering (band width of 700-2000 Hz), and passed through a resistance-capacitance integrating network with a time constant of 0.1 s, providing a mean voltage display of sympathetic nerve activity.…”

Spontanous periodic breathing is associated with sympathetic hyperreactivity and baroreceptor dysfunction in hypertension

“…In brief, electrical activity of muscle vasoconstrictor fibers was measured in the peroneal nerve, posterior to the fibular head by use of tungsten microelectrodes (shaft diameter 200 µm, tapering to an uninsulated tip of 1-5 µm). [24,25] A subcutaneous reference electrode was inserted 1 to 2 cm away from the recording electrode. The neural signal was amplified, filtered, rectified and integrated to obtain a mean voltage neurogram of sympathetic activity.…”