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.

DELIUS, W., K.-E. HAGBARTH, A. HONGELL and B. G. WALLIN. Manoeuvres affecting sympathetic outflow in human skin nerves. Acta physiol. scand. 1972. 84. 177-186. W . a L n i m . 0 -E . . M. IIUKI and E. SIMOS, Antagonistic changes of blood flow and sympathetic activity in different vascular beds following central thermal stimulation. 11. Cutaneous and .i.isceral sympathetic activity during spinal heating and cooling in anesthetized rabbits and cats.

nt,ral characteristics of sympathetic actiitity in human skin nerues. Acta physiol. scand. 1972. 8.1.. 164-176. Synchronized bursts of efferent sympathetic impulses, appearing either spontaneously or triggered by various peripheral stimuli, were recorded with niicroelectrodes inserted percutaneously into skin nerve fascicles in alert, adult subjects. The signals were abolished by sympathetic ganglion blocking agents and by Lidocaine nerve blocks proximal to the recording site. Many of the sympathetic discharges were succeeded by skin resistance changes and plethysmographic vasoconstrictor responses within the innervation zone of the fascicle impaled. The sympathetic activity was not pulse synchronous as in muscle nerves and the spontaneous sympathetic volleys occurred largely indepmdently of spontaneous blood pressure variations, indicating a relative lack of baroreflex control of the vasoconstrictor outflow to the skin. A loose coupling was observed, however. between the resting respiratory rhl-thm and the spontaneous sympathetic bursts in the skin nerves.Sympathetic activity in human muscle nerves. appearing as spontaneous bursts of impulses grouped in the pulse rhythm, was first described by Hagbarth and Vallbo (1968). Their findings were recently confirmed by Delius c T t al. (1971 a ) . who noted in addition an inverse relationship between the strmgth of the pulsative sympathetic outflow in the muscle nenes and spontaneous blood pressure fluctuations. According to Hagbarth and \.'allbo a similar type of activity is not to be found in skin nerve fascicles. During an extended search for sympathetic signals in such fascicles, however, u.e now and then observed spontaneously occurring bursts of impulses which appeared in seemingly random fashion without any obvious relation to pulse rhythms or spontaneous blood pressure fluctuations. A systematic study of these neural phenomena in human skin nerve fascicles has now been undertaken. The results to b c a presented lead to the conclusion that the signals derive from groups of postganglionic sympathetic fibres which in awake relaxed subjects exhibit a fluctuating resting discharge of variable strength and which are easily activated by sudden arousal stimuli. A11 of the triggered and many of the spontaneously occurring sympa-I61

DELIUS, W., K.-E. HAGBARTH? -4. HONCELL and B. G. WALLIN. Manoeuvrcs affecting sympathetic oiitflow in human muscle n c r x s . hcta physiol. scand. 1972. 84. 82-94.Multi-unit sympathetic activit). was recorded in hunian muscle nerves, together with measurements of intra-arterial blood pressure and forearm or calf blood flow, during manoeuvres causing circulatory adjustments. Manoeuvres causing an increased vascular resistance in the forearm or calf were regularly associated with an increase in sympathetic outflow, proving that the neural activity was dominated by vasoconstrictor impulses. T h e inverse changes of blood pressure and sympathetic activity observed during Valsalva's manoeuvre and mental stress are explicable in terms of baroreflex control of the neural outflow. However, during muscle work and hyperventilation the relation between blood pressure and sympathetic activity was more complex, indicating that the baroreflex influence was superimposed or modified by other regulatory mechanisms. Some manoeuvres known to affect sympathetic outflow in skin nerves caused no appreciable change in sympathetic muscle nerve activity.

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