Relationships between activity of sympathetic nerve pairs: phase and coherence

1990 ◽  
Vol 259 (3) ◽  
pp. R549-R560 ◽  
Author(s):  
B. Kocsis ◽  
G. L. Gebber ◽  
S. M. Barman ◽  
M. J. Kenney
Keyword(s):  
Frequency Band ◽  
Sympathetic Nerve ◽  
Coherence Function ◽  
Sympathetic Nerves ◽  
Phase Spectrum ◽  
Central System ◽  
Functional States ◽  
Alpha Chloralose ◽  
Constant Interval ◽  
Nerve Discharge

The coherence function and phase spectrum were used to study the relationships between the discharges of sets of two postganglionic or preganglionic sympathetic nerves in baroreceptor-denervated cats anesthetized with either 5,5-diallylbarbiturate-urethan or alpha-chloralose. Most of the power in sympathetic nerve discharge was contained between 2 and 6 Hz. The coherence values relating the activity of two nerves were significantly different from zero within this frequency band. The phase spectrum was either linear or complex (i.e., showed changes in slope) within the coherent frequency band. We observed three patterns of relationship. The first pattern was characterized by a constant interval between activity in different sympathetic nerves within the coherent frequency band. The second pattern was characterized by a frequency-dependent interval. The third pattern was characterized by uncoupling of the 2- to 6-Hz rhythms in the discharges of different nerves. Switching between these patterns was observed. We suggest that the three patterns reflect different functional states of the central system responsible for the 2- to 6-Hz rhythm. Two models of this system are entertained. The first model is one of a system of coupled oscillators while filtering circuits that receive common inputs are the elements of the second model.

Frequency characteristics of sympathetic nerve discharge in anesthetized rats

1994 ◽  
Vol 267 (3) ◽  
pp. R830-R840 ◽  
Author(s):  
M. J. Kenney
Keyword(s):  
Frequency Domain ◽  
Frequency Band ◽  
Sympathetic Nerve ◽  
Acute Stress ◽  
Sympathetic Nerves ◽  
Frequency Characteristics ◽  
Total Power ◽  
Dynamic Nature ◽  
Frequency Components ◽  
Nerve Discharge

Frequency-domain analyses were used to characterize basal sympathetic nerve discharge (SND) and to determine the relationships between the activity recorded simultaneously from sympathetic nerves in chloralose-anesthetized, baroreceptor-innervated rats. Discharges were recorded from the splanchnic, renal, and lumbar nerves. The following observations were made. 1) Approximately 65-75% of total power in SND was contained below 9 Hz in either baroreceptor-innervated rats or baroreceptor-denervated rats. 2) Coherence values relating the activity of two nerves were significantly different from zero within this frequency band. 3) The interval between the discharges of two sympathetic nerves was either frequency dependent or constant within the coherent frequency band. 4) The frequency components of SND and the relationships between the activity in two sympathetic nerves could be altered during periods of acute stress. These results suggest that the system responsible for basal SND in rats is composed of either multiple sympathetic generators or multiple filters arranged in parallel, which are capable of producing different outputs. The dynamic nature of these circuits was revealed by the changes that occurred during periods of acute stress.

Differential relationships among discharges of postganglionic sympathetic nerves

1991 ◽  
Vol 260 (6) ◽  
pp. R1159-R1167 ◽  
Author(s):  
M. J. Kenney ◽  
S. M. Barman ◽  
G. L. Gebber ◽  
S. Zhong
Keyword(s):  
Frequency Band ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
The Body ◽  
Spectral Analyses ◽  
Decerebrate Cats ◽  
Nerve Discharge

The relationships among the simultaneously recorded discharges of as many as four postganglionic sympathetic nerves were studied with coherence and phase spectral analyses in baroreceptor-denervated cats. Discharges were recorded from the inferior cardiac (CN), vertebral (VN), and renal (RN) nerves. Most of the power in sympathetic nerve discharge was less than 6 Hz, and the discharges of any two nerves coherred over a frequency band generally between 0 and 15 Hz. Peak coherence occurred between 2 and 6 Hz in most cases. Our most important observations are as follows. 1) Coherence values were significantly higher in chloralose-anesthetized than in unanesthetized decerebrate cats. 2) Coherence values were higher for near ipsilateral nerves (e.g., CN and VN) than for widely separated ipsilateral nerves (e.g., CN and RN). 3) Coherence values for most pairs were higher when the nerves were located on the same side (ipsilateral nerves) rather than on opposite sides (contralateral nerves) of the body. 4) Coherence values were higher for some functionally complementary nerves (e.g., CN and RN) than for noncomplementary nerves (e.g., VN and RN). These results support the hypothesis that the central circuits responsible for the basal discharges of different postganglionic sympathetic nerves are selectively coupled.

Diencephalic regions contributing to sympathetic nerve discharge in anesthetized cats

1988 ◽  
Vol 254 (2) ◽  
pp. R249-R256 ◽  
Author(s):  
Z. S. Huang ◽  
K. J. Varner ◽  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Blood Pressure ◽  
Sympathetic Nerve ◽  
Medial Forebrain Bundle ◽  
Significant Component ◽  
Medial Thalamus ◽  
Dependent Component ◽  
Medial Hypothalamus ◽  
Alpha Chloralose ◽  
Frequency Current ◽  
Nerve Discharge

We reported that the forebrain is responsible for a significant component (38%) of inferior cardiac postganglionic sympathetic nerve discharge (SND) in baroreceptor-denervated cats anesthetized with alpha-chloralose [Huang et al., Am. J. Physiol. 252 (Regulatory Integrative Comp. Physiol. 21): R645-R652, 1987]. The current study was initiated to assess the contribution of various diencephalic regions to the forebrain-dependent component of SND in this preparation. For this purpose, the reductions in inferior cardiac SND and blood pressure produced acutely by midbrain transection at stereotaxic plane A3 in nonlesioned control cats were compared with those in cats in which diencephalic lesions were made with radio-frequency current. Lesions of the anterior medial hypothalamus including the paraventricular nucleus failed to attenuate the decreases in SND and blood pressure produced by midbrain transection. In contrast, the effects of midbrain transection were significantly attenuated by lesions of the lateral hypothalamus (including medial forebrain bundle), posterior medial hypothalamus, or the medial thalamus. We conclude that both the hypothalamus and medial thalamus contribute to SND in anesthetized cats.

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.

scholarly journals Aging alters regulation of visceral sympathetic nerve responses to acute hypothermia

2006 ◽  
Vol 291 (3) ◽  
pp. R573-R579 ◽  
Author(s):  
Bryan G. Helwig ◽  
Sujatha Parimi ◽  
Chanran K. Ganta ◽  
Richard Cober ◽  
Richard J. Fels ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Middle Aged ◽  
Fischer 344 ◽  
Skin Cooling ◽  
Young Subjects ◽  
Colonic Temperature ◽  
Induced Changes ◽  
F344 Rats ◽  
Nerve Discharge

Hypothermia produced by acute cooling prominently alters sympathetic nerve outflow. Skin sympathoexcitatory responses to skin cooling are attenuated in aged compared with young subjects, suggesting that advancing age influences sympathetic nerve responsiveness to hypothermia. However, regulation of skin sympathetic nerve discharge (SND) is only one component of the complex sympathetic nerve response profile to hypothermia. Whether aging alters the responsiveness of sympathetic nerves innervating other targets during acute cooling is not known. In the present study, using multifiber recordings of splenic, renal, and adrenal sympathetic nerve activity, we tested the hypothesis that hypothermia-induced changes in visceral SND would be attenuated in middle-aged and aged compared with young Fischer 344 (F344) rats. Colonic temperature (Tc) was progressively reduced from 38°C to 31°C in young (3 to 6 mo), middle-aged (12 mo), and aged (24 mo) baroreceptor-innervated and sinoaortic-denervated (SAD), urethane-chloralose anesthetized, F344 rats. The following observations were made. 1) Progressive hypothermia significantly ( P < 0.05) reduced splenic, renal, and adrenal SND in young baroreceptor-innervated F344 rats. 2) Reductions in splenic, renal, and adrenal SND to progressive hypothermia were less consistently observed and, when observed, were generally attenuated in baroreceptor-innervated middle-aged and aged compared with young F344 rats. 3) Differences in splenic, renal, and adrenal SND responses to reduced Tc were observed in SAD young, middle-aged, and aged F344 rats, suggesting that age-associated attenuations in SND responses to acute cooling are not the result of age-dependent modifications in arterial baroreflex regulation of SND. These findings demonstrate that advancing chronological age alters the regulation of visceral SND responses to progressive hypothermia, modifications that may contribute to the inability of aged individuals to adequately respond to acute bouts of hypothermia.

Central oscillators responsible for sympathetic nerve discharge

1980 ◽  
Vol 239 (2) ◽  
pp. H143-H155 ◽  
Author(s):  
G. L. Gebber
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sympathetic Nerve ◽  
Sympathetic Neurons ◽  
Sympathetic Nerves ◽  
Oscillatory Activity ◽  
Periodic Input ◽  
Neuronal Types ◽  
The Central Nervous System ◽  
Nerve Discharge

The current state of knowledge concerning central mechanisms responsible for the generation of background discharges in sympathetic nerves is examined. It is apparent from recent investigations that the classic concept of a randomly discharging and diffusely organized central network onto which rhythms (cardiac- and respiratory-related) are imposed by extrinsic inputs has not passed the test of time. Rather, brain stem as well as spinal networks that govern the discharges of sympathetic nerves are inherently capable of rhythm generation. Sympathetic nerve rhythms inherent to the central nervous system imply the existence of neuronal circuits that are capable of oscillatory activity. Central oscillators provide a mechanism for synchronization of the activity of populations of sympathetic neurons in the absence of periodic input from sources extrinsic to the central nervous system. Indeed, the thesis is developed that, rather than creating rhythms in sympathetic nerve discharge, the function of periodic input from extrinsic sources such as the baroreceptors is to entrain rhythms of central origin. Finally, the problems associated with the identification of neuronal types that comprise central oscillators which govern the discharges of sympathetic nerves are discussed.

scholarly journals Cold stress alters characteristics of sympathetic nerve discharge bursts

1999 ◽  
Vol 87 (2) ◽  
pp. 732-742 ◽  
Author(s):  
Michael J. Kenney ◽  
Dale E. Claassen ◽  
Richard J. Fels ◽  
Cristina S. Saindon
Keyword(s):  
Body Temperature ◽  
Cold Stress ◽  
Sympathetic Nerve ◽  
Mild Hypothermia ◽  
Core Body Temperature ◽  
Low Frequency ◽  
Sympathetic Nerves ◽  
Level Of Activity ◽  
Core Body ◽  
Nerve Discharge

Frequency-domain analyses were used to determine the effect of cold stress on the relationships between the discharge bursts of sympathetic nerve pairs, sympathetic and aortic depressor nerve pairs, and sympathetic and phrenic nerve pairs in chloralose-anesthetized, baroreceptor-innervated rats. Sympathetic nerve discharge (SND) was recorded from the renal, lumbar, splanchnic, and adrenal nerves during decreases in core body temperature from 38 to 30°C. The following observations were made. 1) Hypothermia produced nonuniform changes in the level of activity in regionally selective sympathetic nerves. Specifically, cold stress increased lumbar and decreased renal SND but did not significantly change the level of activity in splanchnic and adrenal nerves. 2) The cardiac-related pattern of renal, lumbar, and splanchnic SND bursts was transformed to a low-frequency (0–2 Hz) pattern during cooling, despite the presence of pulse-synchronous activity in arterial baroreceptor afferents. 3) Peak coherence values relating the discharges between sympathetic nerve pairs decreased at the cardiac frequency but were unchanged at low frequencies (0–2 Hz), indicating that the sources of low-frequency SND bursts remain prominently coupled during progressive reductions in core body temperature. 4) Coherence of discharge bursts in phrenic and renal sympathetic nerve pairs in the 0- to 2-Hz frequency band increased during mild hypothermia (36°C) but decreased during deep hypothermia (30°C). We conclude that hypothermia profoundly alters the organization of neural circuits involved in regulation of sympathetic nerve outflow to selected regional circulations.

Paraventricular nucleus bicuculline alters frequency components of sympathetic nerve discharge bursts

2001 ◽  
Vol 281 (3) ◽  
pp. H1233-H1241 ◽  
Author(s):  
Michael J. Kenney ◽  
Mark L. Weiss ◽  
Kaushik P. Patel ◽  
Yan Wang ◽  
Richard J. Fels
Keyword(s):  
Paraventricular Nucleus ◽  
Sympathetic Nerve ◽  
Cardiac Cycle ◽  
Low Frequency ◽  
Sympathetic Nerves ◽  
Receptor Antagonism ◽  
Gaba Agonist ◽  
Frequency Components ◽  
Induced Changes ◽  
Nerve Discharge

Autospectral and coherence analyses were used to determine the effect of paraventricular nucleus (PVN) GABAA receptor antagonism [microinfusion or microinjections of bicuculline methiodide (BMI) 100 pmoles] on sympathetic nerve discharge (SND) frequency components (bursting pattern and relationships between discharges in regionally selective nerves) in α-chloralose-anesthetized rats. SND was recorded from the renal, splenic, and lumbar nerves. The following observations were made. First, PVN BMI microinjections, but not PVN saline or cortical BMI microinjections, transformed the cardiac-related SND bursting pattern in baroreceptor-innervated rats to one characterized by the presence of low-frequency bursts not synchronized to the cardiac cycle or phrenic nerve discharge bursts. Second, SND pattern changes were similar in the renal, splenic, and lumbar nerves, and peak coherence values relating low-frequency bursts in sympathetic nerve pairs (renal-splenic, renal-lumbar, and splenic-lumbar) were significantly increased from preinjection control after PVN BMI microinjection. Third, PVN BMI microinjections significantly increased the coupling between low-frequency SND bursts in baroreceptor-denervated rats. Finally, PVN BMI-induced changes in the SND bursting pattern were not observed after PVN pretreatment with muscimol (GABA agonist, 1 nmole). We conclude that PVN GABAA receptor antagonism profoundly alters the frequency components in sympathetic nerves.

Coupled oscillators account for the slow rhythms in sympathetic nerve discharge and phrenic nerve activity

1997 ◽  
Vol 272 (4) ◽  
pp. R1314-R1324 ◽  
Author(s):  
S. Zhong ◽  
S. Y. Zhou ◽  
G. L. Gebber ◽  
S. M. Barman
Keyword(s):  
Phrenic Nerve ◽  
Sympathetic Nerve ◽  
Coupled Oscillators ◽  
Sympathetic Nerves ◽  
Partial Coherence ◽  
Coherence Analysis ◽  
Nerve Activity ◽  
Phrenic Nerve Activity ◽  
Slow Rhythm ◽  
Nerve Discharge

Phase-locked slow rhythms in sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) are generally thought to arise from a common brain stem "cardiorespiratory" oscillator. The results obtained in vagotomized and baroreceptor-denervated cats anesthetized with pentobarbital sodium do not support this view. First, partial coherence analysis revealed that the discharges of pairs of sympathetic nerves remained correlated at the frequency of the central respiratory cycle after mathematical removal of the portion of these signals common to PNA. The residual coherence suggests that the slow rhythm in SND is dependent on central mechanisms in addition to those responsible for rhythmic PNA. Second, the rhythms in SND and PNA became coupled in a 2:1 relationship during either moderate systemic hypocapnia or hypercapnia. Third, the slow rhythm in SND was maintained when rhythmic PNA was eliminated during extreme hypocapnia. Fourth, during extreme hypercapnia, coherence of the rhythms in SND and PNA was drastically reduced. These results suggest that the slow rhythms in SND and PNA arise from separate oscillators that are normally coupled.

Regulation of the sympathetic nerve discharge bursting pattern during heat stress

1998 ◽  
Vol 275 (6) ◽  
pp. R1992-R2001 ◽  
Author(s):  
Michael J. Kenney ◽  
Dale E. Claassen ◽  
Michelle R. Bishop ◽  
Richard J. Fels
Keyword(s):  
Heat Stress ◽  
Frequency Domain ◽  
Phrenic Nerve ◽  
Sympathetic Nerve ◽  
Core Body Temperature ◽  
Low Frequency ◽  
Sympathetic Nerves ◽  
Frequency Components ◽  
Pattern Transformation ◽  
Nerve Discharge

Frequency-domain analyses were used to determine the effect of heat stress on the relationships between the discharge bursts of sympathetic nerve pairs and sympathetic and phrenic nerve pairs in chloralose-anesthetized rats. Sympathetic nerve discharge (SND) was recorded from the renal, splanchnic, splenic, and lumbar nerves during increases in core body temperature (Tc) from 38 to 41.4 ± 0.3°C. The following observations were made: 1) hyperthermia transformed the cardiac-related bursting pattern of SND to a pattern that contained low-frequency, non-cardiac-related bursts, 2) the pattern transformation was uniform in regionally selective sympathetic nerves, 3) hyperthermia enhanced the frequency-domain coupling between SND and phrenic nerve bursts, and 4) low-frequency SND bursts recorded during hyperthermia contained significantly more activity than cardiac-related bursts. We conclude that acute heat stress profoundly affects the organization of neural circuits responsible for the frequency components in sympathetic nerve activity and that SND pattern transformation provides an important strategy for increasing the level of activity in sympathetic nerves during increased Tc.

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