Sympathetic nerve discharge in chronic spinal cat

1982 ◽  
Vol 243 (3) ◽  
pp. H463-H470 ◽  
Author(s):  
J. L. Ardell ◽  
S. M. Barman ◽  
G. L. Gebber
Keyword(s):  
Blood Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Slow Waves ◽  
External Carotid ◽  
Spinal Transection ◽  
Reflex Mechanism ◽  
Ganglionic Blockade ◽  
Spinal Segments ◽  
Nerve Discharge

A study was made of external carotid, renal, and splanchnic sympathetic nerve discharge (SND) in chloralose-anesthetized cats subjected to transection of the sixth cervical spinal segment 2-37 days earlier. Minimal activity was observed under normocapnic conditions 2 days after spinal transection, and ganglionic blockade failed to lower blood pressure. Moderate hypercapnia increased SND and led to synchronization of activity into 1-6 cycle/s slow waves. Such slow-wave activity was present under normocapnic conditions in cats 9-37 days after spinal transection. Ganglionic blockade significantly reduced blood pressure in these preparations. The interval between successive 1-6 cycle/s slow waves was variable. Thus, unlike the case in baroreceptor-denervated cats with an intact neuraxis [Barman and Gebber, Am. J. Physiol. 239 (Regulatory Integrative Comp. Physiol. 8): R42-R47, 1980], chronic spinal cats are incapable of rhythm generation in the 1-6 cycle/s frequency range. Crosscorrelation analysis revealed that the discharges of pairs of segmental (but not intersegmental) sympathetic nerves were related in the chronic spinal cat. This situation differs from that in the baroreceptor-denervated cat in which the discharges of pairs of intersegmental as well as segmental sympathetic nerves are related. Thus coordination of activity in sympathetic nerves that arise from different spinal segments requires the integrity of bulbospinal connections. Finally, no evidence was obtained for the existence of a baroreceptor-like reflex mechanism acting to control SND in the chronic spinal cat.

Differential control of sympathetic nerve discharge by the brain stem

1984 ◽  
Vol 247 (3) ◽  
pp. R513-R519 ◽  
Author(s):  
S. M. Barman ◽  
G. L. Gebber ◽  
F. R. Calaresu
Keyword(s):  
Brain Stem ◽  
Sympathetic Nerve ◽  
Sympathetic Nerves ◽  
Frequency Component ◽  
External Carotid ◽  
Medullary Raphe ◽  
Reticular Neurons ◽  
Differential Control ◽  
The Brain ◽  
Raphe Neurons

This investigation was designed to test the hypothesis that the brain stem differentially controls the basal discharges of postganglionic sympathetic nerves distributed to different organs. Previous studies have shown that the 2- to 6-Hz activity pattern in sympathetic nerves of the baroreceptor-denervated cat originates in the brain stem. In the current study, autocorrelation and power spectral analyses were used to compare the 2- to 6-Hz frequency components of the simultaneously recorded discharges of postganglionic sympathetic nerve pairs (inferior cardiac and renal; external carotid and renal) in baroreceptor-denervated cats anesthetized with sodium diallylbarbiturate and urethan (Dialurethane). In addition, spike-triggered averaging was used to compare the relative strengths of coupling of the basal discharges of single ventrolateral medullary reticular or medullary raphe neurons to activity in postganglionic sympathetic nerve pairs. The major findings of the study are as follows: 1) the predominant 2- to 6-Hz frequency component in the basal discharges of one sympathetic nerve often was different from that in the discharges of a second nerve, and 2) the activity of approximately one-third of ventrolateral medullary reticular neurons and one-half of medullary raphe neurons (with sympathetic-related activity) was differentially related to the discharges of postganglionic nerve pairs. These results support the view that the brain stem reticular formation and raphe complex exert their influences on different sympathetic nerves in a nonuniform fashion.

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.

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.

A comparative study of the acute effects of cetamolol (AI-27,303), atenolol, propranolol, and dexpropranolol on blood pressure, sympathetic nerve and ganglion activity of cats

1983 ◽  
Vol 61 (7) ◽  
pp. 693-698 ◽  
Author(s):  
J. Jaramillo
Keyword(s):  
Blood Pressure ◽  
Comparative Study ◽  
Intravenous Administration ◽  
Superior Cervical Ganglion ◽  
Sympathetic Nerve ◽  
Sympathetic Ganglia ◽  
Acute Effects ◽  
Cervical Ganglion ◽  
Sympathetic Discharge ◽  
Nerve Discharge

The effects of cetamolol (AI-27,303, Betacor®), atenolol, propranolol, and dexpropranolol were evaluated in 36 chloralose–urethane anesthetized cats. Blood pressure, sympathetic nerve discharge, and ganglionic activity (from the superior cervical ganglion) were recorded after the intravenous administration of 2.5, 5.0, and 10 mg/kg doses of the compounds. The results indicate that cetamolol and atenolol decreased blood pressure and discharge in the postganglionic sympathetic nerve and impaired transmission at the level of sympathetic ganglia. Propranolol and dexpropranolol given at the same doses produced a larger decrease in blood pressure, but increased the sympathetic discharge and had no effect on ganglionic spike amplitude.

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.

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