Coherence of medullary unit activity and sympathetic nerve discharge

1990 ◽  
Vol 259 (3) ◽  
pp. R561-R571 ◽  
Author(s):  
G. L. Gebber ◽  
S. M. Barman ◽  
B. Kocsis
Keyword(s):  
Brain Stem ◽  
Unit Activity ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Frequency Domain Analysis ◽  
Ventrolateral Medulla ◽  
Spike Triggered Averaging ◽  
Time Domains ◽  
The Relationship ◽  
Nerve Discharge

Analyses in the frequency and time domains were used to study the relationships between the discharges of single brain stem neurons and postganglionic sympathetic nerves in baroreceptor-innervated and -denervated cats anesthetized with 5,5-diallylbarbiturate-urethan. Spike-triggered averaging was used initially to identify single neurons with sympathetic nerve-related activity in the medullary lateral tegmental field, rostral ventrolateral medulla, and medullary raphe. The discharges of such neurons were correlated to the 2- to 6-Hz rhythm in sympathetic nerve discharge (SND). Frequency-domain analysis revealed that the relationship between medullary unit activity and the sympathetic nerve rhythm was not fixed from cycle to cycle. First, the coherence values relating the activity of these neurons to SND were closer to zero than to unity in most cases. Second, whereas most of the power in the autospectra of SND was contained between 2 and 6 Hz, that in the autospectra of medullary unit activity was more evenly distributed over a much wider frequency band. These and other observations indicate that the 2- to 6-Hz rhythm is an emergent property of a network of brain stem neurons whose discharges are probabilistically rather than strictly related to the phases of the population rhythm.

Brain stem neuronal types with activity patterns related to sympathetic nerve discharge

1981 ◽  
Vol 240 (5) ◽  
pp. R335-R347 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Brain Stem ◽  
Sympathetic Nerve ◽  
Activity Patterns ◽  
Sympathetic Nerves ◽  
Eeg Activity ◽  
Spike Triggered Averaging ◽  
Neuronal Types ◽  
Discharge Patterns ◽  
Electroencephalogram Eeg ◽  
Nerve Discharge

The relationships among the spontaneous activity of single neurons in the cat medulla and inferior cardiac sympathetic nerve discharge (SND), electroencephalogram (EEG) activity, phrenic nerve activity, and the R wave of the electrocardiogram were studied with the methods of spike-triggered averaging and postevent interval analysis. Three categories of neurons (SR, SE, and S) with activity patterns related to SND wee identified. The activity of SR units was related in time to SND and the R wave but not to EEG activity. SE unit discharges were related to SND and EEG activity but not to the R wave. S unit activity was related only to SND. Each of the three categories of neurons could be subdivided into two groups depending on whether their discharges were followed by an increase or a decrease in SND. All unit types exhibited respiratory-related discharge patterns. These data are discussed with regard to the problems associated with the identification of neurons in brain stem networks that govern the discharges of sympathetic nerves.

Effects of brain stem lesions on 10-Hz and 2- to 6-Hz rhythms in sympathetic nerve discharge

1992 ◽  
Vol 262 (6) ◽  
pp. R1015-R1024 ◽  
Author(s):  
S. Zhong ◽  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Brain Stem ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Ventrolateral Medulla ◽  
Total Power ◽  
Field Potentials ◽  
Brain Stem Lesions ◽  
Stem Lesions ◽  
Nerve Discharge

We studied the effects of brain stem lesions or transection on the 10-Hz and 2- to 6-Hz rhythms in sympathetic nerve discharge (SND) in baroreceptor-denervated unanesthetized decerebrate cats. The results indicate that these two rhythms depend in part on different brain stem regions. The 10-Hz rhythm was eliminated by ablation of the rostral ventrolateral medulla (RVLM), medullary raphe complex, or pontine parabrachial and Kolliker-Fuse complex (PB/KF) or by pontomedullary border transection. Except for RVLM lesions, these procedures did not disrupt the 2- to 6-Hz rhythm in SND. In fact the power in SND at frequencies less than 6 Hz was increased by raphe or PB/KF lesions. Total power in SND was not significantly affected by raphe or PB/KF lesions, but mean arterial pressure was significantly reduced. Field potentials recorded from the RVLM (11 of 26 sites) and raphe (10 of 20 sites) were correlated to the 10-Hz rhythm in SND, further supporting a role of these areas in either generating or relaying this rhythm to sympathetic nerves. In contrast, field potentials recorded from the PB/KF were not correlated to the 10-Hz rhythm in SND. Thus this region may provide a tonic drive to the 10-Hz generator located elsewhere in the brain stem.

Role of the brain stem in generating the 2- to 6-Hz oscillation in sympathetic nerve discharge

1993 ◽  
Vol 265 (5) ◽  
pp. R1026-R1035 ◽  
Author(s):  
S. Zhong ◽  
Z. S. Huang ◽  
G. L. Gebber ◽  
S. M. Barman
Keyword(s):  
Brain Stem ◽  
Sympathetic Nerve ◽  
Cervical Spinal Cord ◽  
Ventrolateral Medulla ◽  
Population Activity ◽  
A Value ◽  
Decerebrate Cats ◽  
The Brain ◽  
Nerve Discharge

We tested the hypothesis that brain stem circuits normally generate a 2- to 6-Hz oscillation in sympathetic nerve discharge (SND). Experiments were performed on baroreceptor-denervated decerebrate cats and urethan-anesthetized rats in which renal or splanchnic SND was recorded along with field potentials (population activity) from sites in the rostral ventrolateral medulla, medullary raphe, or medullary lateral tegmental field. Our major findings were as follows. 1) Population activity recorded from the three medullary regions contained a 2- to 6-Hz oscillation. 2) The 2- to 6-Hz oscillation in population activity recorded from some medullary sites was correlated to that in SND. Peak coherence in the 2- to 6-Hz band approached a value of 1 in some cases. 3) Whereas cervical spinal cord transection abolished or markedly reduced SND, the 2- to 6-Hz oscillation in medullary activity was essentially unchanged. These results support the view that the 2- to 6-Hz oscillation in SND can be generated in the brain stem of cats and rats.

Caudal ventrolateral medullary neurons are elements of the network responsible for the 10-Hz rhythm in sympathetic nerve discharge

1994 ◽  
Vol 72 (1) ◽  
pp. 106-120 ◽  
Author(s):  
S. M. Barman ◽  
H. S. Orer ◽  
G. L. Gebber
Keyword(s):  
Firing Rate ◽  
Sympathetic Nerve ◽  
Pressor Response ◽  
Ventral Surface ◽  
Frequency Domain Analysis ◽  
Nerve Activity ◽  
Cardiac Nerve ◽  
Spike Triggered Averaging ◽  
Inferior Cardiac Nerve ◽  
Nerve Discharge

1. This is the first study to show that caudal ventrolateral medullary (CVLM) neurons play an important role in governing the 10-Hz rhythm in sympathetic nerve discharge (SND). Spike-triggered averaging showed that the naturally occurring discharges of 66 of 246 CVLM neurons located 0–2.5 mm rostral to the obex, 4–4.25 mm lateral to the midline, and within 2 mm of the ventral surface were correlated to the 10-Hz rhythm in inferior cardiac SND of 17 urethan-anesthetized cats. 2. Frequency domain analysis was used to characterize further the relationships between SND and the discharges of 45 CVLM neurons with activity correlated to the 10-Hz rhythm in inferior cardiac nerve activity. The autospectra of the discharges of 22 of these neurons contained a sharp peak near 10 Hz (corresponding to the peak in the autospectra of SND), although the mean firing rate of these neurons was only 5.9 +/- 0.5 (SE) spikes/s. The peak coherence value relating the 10-Hz discharges of these CVLM neurons and the inferior cardiac nerve was 0.42 +/- 0.03. The autospectra for the other 23 CVLM neurons did not contain a peak near 10 Hz. Their mean firing rate was 2.3 +/- 0.5 spikes/s, and the peak coherence value relating their discharges to the 10-Hz rhythm in SND was 0.08 +/- 0.01. The coherence value was significantly different than zero in all but three cases. 3. Importantly, spike-triggered averaging and coherence analysis demonstrated that CVLM neurons with activity correlated to the 10-Hz rhythm did not have activity correlated 1:1 to the cardiac-related rhythm in SND of baroreceptor-innervated cats. Also, their discharges were not correlated to the irregular 2- to 6-Hz oscillations in SND of baroreceptor-denervated cats. These data support the hypothesis that different pools of brain stem neurons generate the 10-Hz rhythm and the 2- to 6-Hz oscillations (or cardiac-related rhythm) in SND. 4. Despite the fact that CVLM neurons with activity correlated to the 10-Hz rhythm did not have activity correlated 1:1 to the cardiac-related rhythm in SND, these neurons were influenced by baroreceptor afferent nerve activity. First, their firing rates could be decreased (n = 12) or increased (n = 2) during the pressor response induced by inflating a balloon in the aorta (aortic obstruction). Second, on occasion, the discharges of CVLM neurons and the 10-Hz rhythm in SND were entrained to a harmonic of the heart rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Rostral ventrolateral medullary and caudal medullary raphe neurons with activity correlated to the 10-Hz rhythm in sympathetic nerve discharge

1992 ◽  
Vol 68 (5) ◽  
pp. 1535-1547 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Slow Wave ◽  
Sympathetic Nerve ◽  
Frequency Domain Analysis ◽  
Firing Rates ◽  
Medullary Raphe ◽  
The Mean ◽  
The Relationship ◽  
Medullary Neurons ◽  
Raphe Neurons ◽  
Nerve Discharge

1. The current study is the first to identify medullary neurons whose naturally occurring discharges were correlated to the 10-Hz rhythm in sympathetic nerve discharge (SND). Spike-triggered averaging showed that 44 of 164 rostral ventrolateral medullary (RVLM) and 44 of 174 caudal medullary raphe neurons had activity correlated to the 10-Hz rhythm in inferior cardiac postganglionic SND of 23 baroreceptor-denervated, decerebrate cats. 2. When the frequency of the rhythm in SND was decreased by lowering body temperature, the discharges of the 10 neurons tested (6 RVLM and 4 raphe) remained locked to the peak of the next 10-Hz sympathetic nerve slow wave rather than to the peak of the preceding slow wave. This observation supports the contention that the 10-Hz rhythm in basal SND was generated in the brain stem rather than in the spinal cord. 3. Frequency-domain analysis was used to characterize further the relationship between the 10-Hz rhythm in SND and the discharges of 30 RVLM and 24 raphe neurons. The autospectra of the discharges of eight RVLM and four raphe neurons contained a sharp peak near 10 Hz, although the mean firing rates of these neurons were lower than the frequency of the rhythm in SND. Coherence values as high as 0.76 characterized the relationship between the discharges of these "rhythmically firing neurons" and the 10-Hz rhythm in SND. A coherence value of 1.0 indicates a perfect correlation. The autospectra of the discharges of the 22 RVLM and 20 raphe neurons did not contain a peak near 10 Hz. The mean firing rates and coherence values relating the discharges of these "nonrhythmically firing neurons" and the 10-Hz rhythm in SND were significantly lower than those for the rhythmically firing neurons. Because the frequency of the population rhythm recorded from the inferior cardiac nerve was higher than the firing rates of individual medullary neurons, the 10-Hz rhythm in SND appears to be an emergent property of a network of neurons whose discharges are probabilistically related to the population rhythm. 4. In addition to the peak near 10-Hz, the autospectrum of SND often contained considerable power at frequencies < 6 Hz. This component of SND is called the 2- to 6-Hz rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Partial Spectral Analysis of Cardiac-Related Sympathetic Nerve Discharge

2000 ◽  
Vol 84 (3) ◽  
pp. 1168-1179 ◽  
Author(s):  
Peter D. Larsen ◽  
Craig D. Lewis ◽  
Gerard L. Gebber ◽  
Sheng Zhong
Keyword(s):  
Sympathetic Nerve ◽  
Phase Locking ◽  
Sympathetic Nerves ◽  
Heart Beat ◽  
Partial Coherence ◽  
Coherence Analysis ◽  
Clear Peak ◽  
The Relationship ◽  
Mode Of Coordination ◽  
Nerve Discharge

We have studied the relationship between pulse synchronous baroreceptor input (represented by the arterial pulse, AP) and the cardiac-related rhythm in sympathetic nerve discharge (SND) of urethan-anesthetized cats by using partial autospectral and partial coherence analysis. Partial autospectral analysis was used to mathematically remove the portion of SND that can be directly attributed to the AP, while partial coherence analysis was used to removed the portion of the relationship between the discharges of sympathetic nerve pairs that can be attributed to linear AP-SND relationships that are common to the nerves. The ordinary autospectrum of SND (ASSND) and coherence functions relating the discharges of nerve pairs (CohSND-SND) contained a peak at the frequency of the heart beat. When the predominant mode of coordination between AP and SND was a phase walk, partialization of the autospectra of SND with AP (ASSND/AP) left considerable power in the cardiac-related band. In contrast, when the predominant mode of coordination between AP and SND was phase-locking, there was virtually no cardiac-related activity remaining in ASSND/AP. Partialization of CohSND-SND with AP reduced the peak coherence within the cardiac-related band in both modes of coordination but to a much greater extent during phase-locking. After baroreceptor denervation, CohSND-SND at the cardiac frequency remained significant, although a clear peak above background coherence was no longer apparent. These results are consistent with a model in which the central circuits controlling different sympathetic nerves share baroreceptor inputs and in addition are physically interconnected. The baroreceptor-sympathetic relationship contains both linear and nonlinear components, the former reflected by phase-locking and the latter by phase walk. The residual power in ASSND/AP during phase walk can be attributed to the nonlinear relationship, and the residual peak in partialized nerve-to-nerve coherence (CohSND-SND/AP) arises largely from nonlinearities that are common to the two nerves. During both phase walk and phase-locking, in addition to common nonlinear AP-SND relationships, coupling of the central circuits generating the nerve activities may contribute to CohSND-SND/APbecause significant CohSND-SND was still observed following baroreceptor denervation.

scholarly journals 2019 Ludwig Lecture: Rhythms in sympathetic nerve activity are a key to understanding neural control of the cardiovascular system

2020 ◽  
Vol 318 (2) ◽  
pp. R191-R205 ◽  
Author(s):  
Susan M. Barman
Keyword(s):  
Brain Stem ◽  
Cardiovascular System ◽  
Sympathetic Nerve ◽  
Neural Control ◽  
Sympathetic Nerve Activity ◽  
Cardiovascular Responses ◽  
Sympathetic Nerves ◽  
Ventrolateral Medulla ◽  
Nerve Activity

This review is based on the Carl Ludwig Distinguished Lecture, presented at the 2019 Experimental Biology Meeting in Orlando, FL, and provides a snapshot of >40 years of work done in collaboration with the late Gerard L. Gebber and colleagues to highlight the importance of considering the rhythmic properties of sympathetic nerve activity (SNA) and brain stem neurons when studying the neural control of autonomic regulation. After first providing some basic information about rhythms, I describe the patterns and potential functions of rhythmic activity recorded from sympathetic nerves under various physiological conditions. I review the evidence that these rhythms reflect the properties of central sympathetic neural networks that include neurons in the caudal medullary raphe, caudal ventrolateral medulla, caudal ventrolateral pons, medullary lateral tegmental field, rostral dorsolateral pons, and rostral ventrolateral medulla. The role of these brain stem areas in mediating steady-state and reflex-induced changes in SNA and blood pressure is discussed. Despite the common appearance of rhythms in SNA, these oscillatory characteristics are often ignored; instead, it is common to simply quantify changes in the amount of SNA to make conclusions about the function of the sympathetic nervous system in mediating responses to a variety of stimuli. This review summarizes work that highlights the need to include an assessment of the changes in the frequency components of SNA in evaluating the cardiovascular responses to various manipulations as well as in determining the role of different brain regions in the neural control of the cardiovascular system.

Lateral tegmental field neurons play a permissive role in governing the 10-Hz rhythm in sympathetic nerve discharge

1993 ◽  
Vol 265 (5) ◽  
pp. R1006-R1013 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Peak Frequency ◽  
Chemical Inactivation ◽  
Rhythm Generator ◽  
Spike Triggered Averaging ◽  
Series Of Experiments ◽  
Decerebrate Cats ◽  
Permissive Role ◽  
Nerve Discharge

Recordings from sympathetic nerves in decerebrate cats show a variable mixture of 10-Hz and 2- to 6-Hz discharges. Although medullary lateral tegmental field (LTF) neurons are considered to be a source of the 2- to 6-Hz oscillation in sympathetic nerve discharge (SND), their role in the control of the 10-Hz rhythm has not been critically evaluated. This issue served as the focus of the current study. In the first series of experiments, spike-triggered averaging of inferior cardiac SND was used in an attempt to identify LTF neurons with activity correlated to the 10-Hz rhythm in SND. The discharges of only one of the 120 LTF neurons studied were correlated to this component of SND. In contrast, 17 of 79 neurons had activity correlated to the 2- to 6-Hz oscillation in experiments in which this component of SND was prominent. These data indicate that LTF neurons neither receive input from nor are components of the 10-Hz rhythm generator. In a second series of experiments, muscimol was microinjected into the LTF bilaterally. Chemical inactivation of the LTF either eliminated the 10-Hz rhythm or reduced the power and peak frequency in this band of SND. These data support the view that LTF neurons have a permissive role in governing the 10-Hz rhythm in SND, probably by acting on elements of the rhythm generator located elsewhere. As expected, muscimol microinjections reduced the power in the 2- to 6-Hz band in SND in some experiments.

The 10-Hz rhythm in sympathetic nerve discharge

1992 ◽  
Vol 262 (6) ◽  
pp. R1006-R1014 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber ◽  
S. Zhong
Keyword(s):  
Frequency Domain ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Frequency Dependent ◽  
New Findings ◽  
Decerebrate Cats ◽  
Nerve Discharge

Frequency-domain analysis was used to characterize the relationships among the rhythmic discharges recorded simultaneously from two to four sympathetic nerves in unanesthetized decerebrate cats. The major new findings were as follows. 1) The 10-Hz rhythmic discharges of different nerves cohered strongly in baroreceptor-innervated and -denervated cats. 2) The interval between the discharges of two nerves was frequency dependent in the 10-Hz band in some cats, supporting the view that the 10-Hz rhythm is generated by multiple central circuits that are coupled. 3) In some cases the central circuits responsible for the 10-Hz rhythms nonuniformly affected different nerves. 4) In baroreceptor-innervated cats the coherence values for the cardiac-related discharges of any two nerves were significantly higher than those for the 10-Hz rhythms. 5) In baroreceptor-denervated cats the 10-Hz rhythmic discharges of different nerves cohered more strongly than the 2- to 6-Hz rhythms. 6) The 10-Hz rhythm usually was not a harmonic of the 2- to 6-Hz or cardiac-related rhythm. Thus these rhythms are generated independently.

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

2005 ◽  
Vol 288 (5) ◽  
pp. R1396-R1410 ◽  
Author(s):  
Shaun W. Phillips ◽  
Gerard L. Gebber ◽  
Susan M. Barman
Keyword(s):  
Respiratory Rate ◽  
Sympathetic Nerve ◽  
Artificial Ventilation ◽  
Critical Role ◽  
Lung Inflation ◽  
Chemical Inactivation ◽  
A Value ◽  
Relationship Of ◽  
The Relationship ◽  
Nerve Discharge

We used spectral analysis and event-triggered averaging to determine the effects of chemical inactivation of the medullary lateral tegmental field (LTF) on 1) the relationship of intratracheal pressure (ITP, an index of vagal lung inflation afferent activity) to sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) and 2) central respiratory rate in paralyzed, artificially ventilated dial-urethane-anesthetized cats. ITP-SND coherence value at the frequency of artificial ventilation was significantly ( P < 0.05; n = 18) reduced from 0.73 ± 0.04 (mean ± SE) to 0.24 ± 0.04 after bilateral microinjection of muscimol into the LTF. Central respiratory rate was unexpectedly increased in 12 of these experiments (0.28 ± 0.03 vs. 0.95 ± 0.25 Hz). The ITP-PNA coherence value was variably affected by chemical inactivation of the LTF. It was unchanged when central respiratory rate was also not altered, decreased when respiratory rate was increased above the rate of artificial ventilation, and increased when respiratory rate was raised from a value below the rate of artificial ventilation to the same frequency as the ventilator. Chemical inactivation of the LTF increased central respiratory rate in four of six vagotomized cats but did not significantly affect the PNA-SND coherence value. These data demonstrate that the LTF 1) plays a critical role in mediating the effects of vagal lung inflation afferents on SND but not PNA, 2) helps maintain central respiratory rate in the physiological range, but 3) is not involved in the coupling of central respiratory and sympathetic circuits.

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