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.

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.

scholarly journals Altered frequency responses of sympathetic nerve discharge bursts after IL-1β and mild hypothermia

2002 ◽  
Vol 93 (1) ◽  
pp. 280-288 ◽  
Author(s):  
M. J. Kenney ◽  
F. Blecha ◽  
R. J. Fels ◽  
D. A. Morgan
Keyword(s):  
Sympathetic Nerve ◽  
Neural Circuits ◽  
Mild Hypothermia ◽  
Sympathetic Nerves ◽  
Interscapular Brown Adipose Tissue ◽  
Frequency Responses ◽  
Brown Adipose ◽  
Complex Relationships ◽  
Colonic Temperature ◽  
Nerve Discharge

Although interleukin-1β (IL-1β) administration produces nonuniform changes in the level of sympathetic nerve discharge (SND), the effect of IL-1β on the frequency-domain relationships between discharges in different sympathetic nerves is not known. Autospectral and coherence analyses were used to determine the effect of IL-1β and mild hypothermia (60 min after IL-1β, colonic temperature from 38°C to 36°C) on the relationships between renal-interscapular brown adipose tissue (IBAT) and splenic-lumbar sympathetic nerve discharges in chloralose-anesthetized rats. The following observations were made. 1) IL-1β did not alter renal-IBAT coherence values in the 0- to 2-Hz frequency band or at the cardiac frequency (CF). 2) Peak coherence values relating splenic-lumbar discharges at the CF were significantly increased after IL-1β and during hypothermia. 3) Hypothermia after IL-1β significantly reduced the coupling (0–2 Hz and CF) between renal-IBAT but not splenic-lumbar SND bursts. 4) Combining IL-1β and mild hypothermia had a greater effect on renal-IBAT SND coherence values than did mild hypothermia alone. These data demonstrate functional plasticity in sympathetic neural circuits and suggest complex relationships between immune products and SND regulation.

Sympathetic nerve regulation to heating is altered in senescent rats

2002 ◽  
Vol 283 (2) ◽  
pp. R513-R520 ◽  
Author(s):  
Michael J. Kenney ◽  
Richard J. Fels
Keyword(s):  
Sympathetic Nerve ◽  
Neural Circuits ◽  
Internal Temperature ◽  
Fischer 344 ◽  
Young Rats ◽  
F344 Rats ◽  
Nerve Discharge ◽  
Nerve Regulation

Renal and splanchnic sympathetic nerve discharge (SND) responses to increased (38–41°C) internal temperature were determined in anesthetized young (3–6 mo old), mature (12 mo old), and senescent (24 mo old) Fischer 344 (F344) rats. We hypothesized that SND responses would be altered in senescent and mature rats as demonstrated by attenuated sympathoexcitatory responses to heating and by the absence of hyperthermia-induced SND pattern changes. The following observations were made. 1) Renal and splanchnic SND responses were significantly increased during heating in young and mature but not in senescent rats. 2) At 41°C, renal and splanchnic SND responses were higher in young compared with senescent rats, and renal SND was higher in mature than in senescent rats. 3) Heating changed the SND bursting pattern in young, but not in mature or senescent, rats. 4) SND responses to heating did not differ between baroreceptor-innervated (BRI) and sinoaortic-denervated (SAD) senescent rats but were higher in SAD compared with BRI young rats. These results demonstrate an attenuated responsiveness of sympathetic neural circuits to heating in senescent F344 rats.

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.

scholarly journals Effects of combined aging and heart failure on visceral sympathetic nerve and cardiovascular responses to progressive hyperthermia in F344 rats

2010 ◽  
Vol 299 (6) ◽  
pp. R1555-R1563 ◽  
Author(s):  
M. L. Margiocco ◽  
M. Borgarelli ◽  
T. I. Musch ◽  
D. M. Hirai ◽  
K. S. Hageman ◽  
...  
Keyword(s):  
Heart Failure ◽  
Sympathetic Nerve ◽  
Cardiovascular Responses ◽  
Aged Rats ◽  
Young Rats ◽  
Regulatory Status ◽  
High Prevalence ◽  
Effects Of Aging ◽  
Colonic Temperature ◽  
F344 Rats

Sympathetic nerve discharge (SND) responses to hyperthermia are attenuated in aged rats without heart failure (HF) and in young HF (YHF) rats, demonstrating that individually aging and HF alter SND regulation. However, the combined effects of aging and HF on SND regulation to heat stress are unknown, despite the high prevalence of HF in aged individuals. We hypothesized that SND responses to heating would be additive when aging and HF are combined, demonstrated by marked reductions in SND and mean arterial pressure (MAP) responses to heating in aged HF (AHF) compared with aged sham HF (ASHAM) rats, and in AHF compared with YHF rats. Renal and splenic SND responses to hyperthermia (colonic temperature increased to 41.5°C) were determined in anesthetized YHF, young sham (YSHAM), AHF, and ASHAM Fischer rats. HF was induced by myocardial infarction and documented using echocardiographic, invasive, and postmortem measures. The severity of HF was similar in YHF and AHF rats. SND responses to heating were attenuated in YHF compared with YSHAM rats, demonstrating an effect of HF on SND regulation in young rats. In contrast, AHF and ASHAM rats demonstrated similar SND responses to heating, suggesting a prominent influence of age on SND regulation in AHF rats. Splenic SND and MAP responses to heating were similar in YHF, AHF, and ASHAM rats, indicating that the imposition of HF in young rats changes the regulatory status of these variables to one consistent with aged rats. These data suggest that the effect of HF on SND regulation to hyperthermia is age dependent.

Metabolic responses to tyramine and cold in young male Sprague-Dawley and Fischer 344 rats

1984 ◽  
Vol 246 (2) ◽  
pp. E141-E144 ◽  
Author(s):  
M. Kiang-Ulrich ◽  
S. M. Horvath
Keyword(s):  
Young Male ◽  
Strain Differences ◽  
Metabolic Responses ◽  
Fischer 344 Rats ◽  
Sprague Dawley ◽  
O2 Uptake ◽  
Fischer 344 ◽  
Cold Challenge ◽  
Colonic Temperature ◽  
F344 Rats

Significant differences in responses to intraperitoneally injected tyramine or cold exposure (-10 degrees C) were observed in young (3-4 mo) male Sprague-Dawley (S-D) and Fischer 344 (F344) rats cold-acclimated (CA) or non-cold-acclimated (non-CA). Non-CA S-D and F344 rats respond to tyramine by increased O2 uptake and elevation of colonic temperature, but, as we had reported previously, the optimal doses of tyramine required was significantly different for these two strains, i.e., 2 mg/kg for F344 vs. 20 mg/kg for S-D. The response to tyramine was significantly potentiated by cold acclimation in both strains of rats. Despite the different dosages of tyramine given to the animals, similar increases in O2 uptakes and colonic temperatures were observed. Differences between these two strains were also evident in their responses to a cold challenge (3 h, -10 degrees C). The ranking for cold tolerance (-10 degrees C) was as follows: CA F344 greater than non-CA F344 greater than CA S-D greater than non-CA S-D. These differences between the two strains suggest that interpretations regarding the response of rats to stressful conditions must be made with caution and appreciation of strain differences.

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 Dexmedetomidine and regulation of splenic sympathetic nerve discharge in aged F344 rats

2015 ◽  
Vol 190 ◽  
pp. 53-57 ◽  
Author(s):  
R.M. McMurphy ◽  
R.J. Fels ◽  
M.J. Kenney
Keyword(s):  
Sympathetic Nerve ◽  
F344 Rats ◽  
Nerve Discharge

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.

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