Defenselike patterns of spinal sympathetic outflow involving the 10-Hz and cardiac-related rhythms

2000 ◽  
Vol 278 (6) ◽  
pp. R1616-R1626 ◽  
Author(s):  
Gerard L. Gebber ◽  
Sheng Zhong ◽  
Craig Lewis ◽  
Susan M. Barman
Keyword(s):  
Blood Pressure ◽  
Time Domain ◽  
Sympathetic Nerve ◽  
High Frequency ◽  
Control Level ◽  
Sympathetic Nerves ◽  
Sympathetic Outflow ◽  
Related Activity ◽  
Free Running ◽  
Stimulation Of

Frequency- and time-domain analyses were used to compare the effects of stimulation of the defense region of the midbrain periaqueductal gray (PAG) on the 10-Hz and cardiac-related discharges of sympathetic nerves with different cardiovascular targets. In baroreceptor-denervated cats anesthetized with urethan, PAG stimulation at frequencies equal to or higher (up to 25 Hz) than that of the free-running 10-Hz rhythm produced an immediate and sustained decrease in vertebral sympathetic nerve (VN) 10-Hz activity but increased the 10-Hz discharges of the inferior cardiac (CN) and renal (RN) nerves. In baroreceptor-innervated cats, VN cardiac-related activity was initially unchanged by high-frequency (25-Hz) PAG stimulation, or it increased along with that in the CN and RN. Later, during high-frequency PAG stimulation, when the rise in blood pressure approached its peak, VN cardiac-related activity usually was reduced below control level. At this time, the increases in CN and RN cardiac-related discharges were largely sustained. The cardiac-related discharges of the three nerves were unaffected by PAG stimulation at frequencies just below or just above that of the heartbeat. We conclude that the defenselike pattern of spinal sympathetic outflow involving the 10-Hz rhythm is different in mechanism and character from that involving the cardiac-related rhythm.

Differential Patterns of Spinal Sympathetic Outflow Involving a 10-Hz Rhythm

1999 ◽  
Vol 82 (2) ◽  
pp. 841-854 ◽  
Author(s):  
Gerard L. Gebber ◽  
Sheng Zhong ◽  
Craig Lewis ◽  
Susan M. Barman
Keyword(s):  
Brain Stem ◽  
Phase Angle ◽  
Sympathetic Nerves ◽  
Phase Relations ◽  
Sympathetic Outflow ◽  
Free Running ◽  
The Difference ◽  
Electrical Stimuli ◽  
The Brain ◽  
Stimulation Of

Time and frequency domain analyses were used to examine the changes in the relationships between the discharges of the inferior cardiac (CN) and vertebral (VN) postganglionic sympathetic nerves produced by electrical activation of the midbrain periaqueductal gray (PAG) in urethan-anesthetized, baroreceptor-denervated cats. CN-VN coherence and phase angle in the 10-Hz band served as measures of the coupling of the central oscillators controlling these nerves. The 10-Hz rhythm in CN and VN discharges was entrained 1:1 to electrical stimuli applied to the PAG at frequencies between 7 and 12 Hz. CN 10-Hz discharges were increased, and VN 10-Hz discharges were decreased when the frequency of PAG stimulation was equal to or above that of the free-running rhythm. In contrast, stimulation of the same PAG sites at lower frequencies increased, albeit disproportionately, the 10-Hz discharges of both nerves. In either case, PAG stimulation significantly increased the phase angle between the two signals (VN 10-Hz activity lagged CN activity); coherence values relating their discharges were little affected. However, the increase in phase angle was significantly more pronounced when the 10-Hz discharges of the two nerves were reciprocally affected. Importantly, partialization of the phase spectrum using the PAG stimuli did not reverse the change in CN-VN phase angle. This observation suggests that the increase in the CN-VN phase angle reflected changes in the phase relations between coupled oscillators in the brain stem rather than the difference in conduction times to the two nerves from the site of PAG stimulation. In contrast to the effects elicited by PAG stimulation, stimulation of the medullary lateral tegmental field induced uniform increases in the 10-Hz discharges of the two nerves and no change in the CN-VN phase angle. Our results demonstrate that changes in the phase relations among coupled brain stem 10-Hz oscillators are accompanied by differential patterns of spinal sympathetic outflow. The reciprocal changes in CN and VN discharges produced by PAG stimulation are consistent with the pattern of spinal sympathetic outflow expected during the defense reaction.

Spectral characteristics of skin sympathetic nerve activity in heat-stressed humans

2006 ◽  
Vol 290 (4) ◽  
pp. H1601-H1609 ◽  
Author(s):  
Jian Cui ◽  
Mithra Sathishkumar ◽  
Thad E. Wilson ◽  
Manabu Shibasaki ◽  
Scott L. Davis ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Sympathetic Nerve ◽  
High Frequency ◽  
Sympathetic Nerve Activity ◽  
Spectral Power ◽  
Spectral Characteristics ◽  
Nerve Activity

Skin sympathetic nerve activity (SSNA) exhibits low- and high-frequency spectral components in normothermic subjects. However, spectral characteristics of SSNA in heat-stressed subjects are unknown. Because the main components of the integrated SSNA during heat stress (sudomotor/vasodilator activities) are different from those during normothermia and cooling (vasoconstrictor activity), we hypothesize that spectral characteristics of SSNA in heat-stressed subjects will be different from those in subjects subjected to normothermia or cooling. In 17 healthy subjects, SSNA, electrocardiogram, arterial blood pressure (via Finapres), respiratory activity, and skin blood flow were recorded during normothermia and heat stress. In 7 of the 17 subjects, these variables were also recorded during cooling. Spectral characteristics of integrated SSNA, R-R interval, beat-by-beat mean blood pressure, skin blood flow variability, and respiratory excursions were assessed. Heat stress and cooling significantly increased total SSNA. SSNA spectral power in the low-frequency (0.03–0.15 Hz), high-frequency (0.15–0.45 Hz), and very-high-frequency (0.45–2.5 Hz) regions was significantly elevated by heat stress and cooling. Interestingly, heat stress caused a greater relative increase of SSNA spectral power within the 0.45- to 2.5-Hz region than in the other spectral ranges; cooling did not show this effect. Differences in the SSNA spectral distribution between normothermia/cooling and heat stress may reflect different characteristics of central modulation of vasoconstrictor and sudomotor/vasodilator activities.

Spinal interneurons with sympathetic nerve-related activity

1984 ◽  
Vol 247 (5) ◽  
pp. R761-R767 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Electrical Stimulation ◽  
Sympathetic Nerve ◽  
Sympathetic Neurons ◽  
Related Activity ◽  
Spinal Interneurons ◽  
The Third ◽  
Cardiac Nerve ◽  
Thoracic Spinal ◽  
Inferior Cardiac Nerve ◽  
Stimulation Of

This study tested the hypothesis that at least some brain stem and reflex control of sympathetic outflow is mediated over pathways containing spinal interneurons. The vicinity of the intermediolateral nucleus (IML) of the third thoracic spinal segment was searched for neurons with spontaneous activity correlated to that in the inferior cardiac post-ganglionic sympathetic nerve of 16 baroreceptor-denervated cats anesthetized with Dial-urethane. Section of the carotid sinus, aortic depressor, and vagus nerves prevented the coupling of sympathetic and nonsympathetic networks by pulse synchronous baroreceptor activity. Spike-triggered averaging revealed the existence of two types of spinal neurons with sympathetic nerve-related activity. Preganglionic sympathetic neurons (PSN; n = 33) were antidromically activated by electrical stimulation of their axons in the third thoracic white ramus. Four observations suggest that the second group of neurons with sympathetic nerve-related activity (n = 18) were spinal interneurons (SIN) in pathways that excite PSN. First, these neurons could not be antidromically activated by stimulation of the segmental white ramus. Second, the intervals between spontaneous unit spike occurrence and inferior cardiac nerve activity were similar for SIN and PSN. Third, SIN and PSN were activated with nearly identical onset latencies by electrical stimulation of medullary sympathoexcitatory sites. Fourth, SIN were excited by intensities of cardiac sympathetic afferent stimulation that also activated PSN and the inferior cardiac nerve. SIN and PSN were distinguished on the basis of their spontaneous firing patterns; i.e., interspike intervals of SIN were significantly shorter than those of PSN.(ABSTRACT TRUNCATED AT 250 WORDS)

Spinally mediated inhibition of abdominal and lumbar sympathetic activities

1988 ◽  
Vol 254 (4) ◽  
pp. R655-R658 ◽  
Author(s):  
R. F. Taylor ◽  
L. P. Schramm
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Activity ◽  
Sympathetic Nerve Activity ◽  
Sympathetic Nerves ◽  
Grouped Data ◽  
Response Curves ◽  
Spinal Transection ◽  
Stimulus Response ◽  
Dorsolateral Funiculus ◽  
Stimulation Of

Renal, splenic, and lumbar sympathetic nerve activities were recorded in the paralyzed, anesthetized, artificially ventilated, and spinally transected rat. Electrical stimulation of the dorsolateral funiculus caudal to the spinal transection was used to generate stimulus-response curves for changes in sympathetic activity in each of the three sympathetic nerves using five stimulus frequencies. In all rats, spinal stimulation inhibited sympathetic activity in renal and splenogastric nerves by approximately 50%. In grouped data, threshold frequency for inhibition of renal and splenogastric sympathetic nerve activity was 5 Hz, and inhibitions were maximal (50-60%) at 10 Hz. In contrast, activity in the lumbar sympathetic chain was inhibited in only two of five rats, and grouped data did not exhibit any statistically significant inhibitions. We conclude that lumbar sympathetic activity which remains after spinal transection can be inhibited only marginally by spinal stimulation, which substantially reduces renal and splenogastric sympathetic activity.

Regional and functional differences in the distribution of vestibulosympathetic reflexes

1998 ◽  
Vol 275 (3) ◽  
pp. R824-R835 ◽  
Author(s):  
I. A. Kerman ◽  
B. J. Yates
Keyword(s):  
Blood Pressure ◽  
Vestibular System ◽  
Sympathetic Nerves ◽  
Relative Magnitude ◽  
External Carotid ◽  
Sympathetic Outflow ◽  
Renal Nerve ◽  
Body Regions ◽  
Sympathetic Efferents ◽  
Vestibulosympathetic Reflexes

Although considerable evidence suggests that the vestibular system regulates sympathetic outflow during movement and changes in posture, little is known about relative vestibular influences on activity of different sympathetic nerves and sympathetic efferents with different functions. In the present study, we demonstrated that electrical stimulation of the vestibular nerve in the cat elicited responses in sympathetic nerves innervating the head and abdominal viscera. This observation suggests that activity of sympathetic efferents innervating multiple body regions is affected by vestibular signals. These responses were attenuated by >80% when blood pressure was increased to >160 mmHg. Because raising blood pressure decreases the responsiveness of vasoconstrictor fibers, the simplest explanation for these data is that the vestibular system provides particularly strong inputs to components of the sympathetic nervous system that regulate peripheral vascular resistance. Furthermore, the relative magnitude of vestibulosympathetic reflexes was over four times larger in one sympathetic nerve composed mainly of vasoconstrictor efferents (renal nerve) than another nerve (external carotid nerve) containing similar types of fibers. Collectively, these data indicate that the vestibular system has selective influences on sympathetic outflow to particular tissues and body regions.

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