Relationship between size and latency of action potentials in human muscle sympathetic nerve activity

Salmanpour, Aryan; Brown, Lyndon J.; Steinback, Craig D.; Usselman, Charlotte W.; Goswami, Ruma; Shoemaker, J. Kevin

doi:10.1152/jn.00814.2010

Cited by 55 publications

(105 citation statements)

References 27 publications

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“…Briefly, this technique uses a continuous wavelet transform (CWT) for AP detection. The CWT used a "mother wavelet" that was adapted to an actual average AP waveform constructed from physiological recordings of postganglionic sympathetic APs (i.e., matched mother wavelet had the same morphology as a physiological sympathetic AP; Salmanpour et al 2010). The designing process involves 1) detecting APs from the filtered raw MSNA signal and averaging them to build a mean AP template, and 2) matching the amplitude and the phase of the new mother wavelet to that of the mean AP template in the frequency domain .…”

Section: Methodsmentioning

confidence: 99%

“…Extracted APs were grouped as overlapped (i.e., the summated signal of two co-occurring APs) or single APs based on their morphology (for a complete performance evaluation of our AP detection algorithm on overlapping APs, see Salmanpour et al 2010). Then, nonoverlapped APs were ordered based on peak-to-peak amplitude and histogram analysis was performed to separate APs into amplitudebased clusters based on Scott's rule (Scott 1979).…”

Section: Methodsmentioning

confidence: 99%

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Baroreflex mechanisms regulating the occurrence of neural spikes in human muscle sympathetic nerve activity

Salmanpour

Shoemaker

2012

Journal of Neurophysiology

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Salmanpour A, Shoemaker JK. Baroreflex mechanisms regulating the occurrence of neural spikes in human muscle sympathetic nerve activity. J Neurophysiol 107: 3409 -3416, 2012. First published March 21, 2012 doi:10.1152/jn.00925.2011.-This study tested the hypothesis that the discharge patterns of action potentials (APs) within bursts of postganglionic muscle sympathetic nerve activity (MSNA) are subject to arterial baroreflex control but in a manner that varies inversely with AP size. MSNA data were collected over 5 min of supine rest in 15 young and healthy individuals (8 males; 24 Ϯ 4 yr of age; means Ϯ SD). The baroreflex threshold and sensitivity diagrams were constructed for both the integrated sympathetic bursts and for the AP clusters. For the integrated bursts, a strong linear relationship between burst probability and diastolic blood pressure (DBP) was observed (P Ͻ 0.05). There was little relationship between integrated burst strength (amplitude) and DBP. On average, 12 AP clusters were observed across individuals. Larger APs tended to appear in the larger bursts. Linear regression analysis was used to study the baroreflex threshold (probability of AP cluster occurrence vs. DBP) as well as the baroreflex sensitivity (AP cluster size vs. DBP). A significant reflex threshold relationship was observed in 75-100% of AP clusters across all individuals. In contrast, significant reflex sensitivity relationships were observed in only 9 of 15 individuals and for limited APs. Overall, the slope of the AP baroreflex threshold relationship was greater for the small-medium sized AP clusters than that of the larger APs. Therefore, within each burst, the small-medium sized APs are governed by the baroreflex mechanism. However, the large APs, which tend to appear in the large integrated bursts, are weakly associated with a baroreflex control feature. The variable impact of baroreflex control over AP occurrence provides a plausible explanation for the overall weak baroreflex control over integrated burst strength, a feature that is determined by both the number and size of the AP complement. microneurography; spike detection and classification; firing probability THE RECRUITMENT STRATEGIES used by the central nervous system to coordinate the discharge patterns in postganglionic sympathetic outflow have been a focus of research since the multi unit discharge behavior was first observed in mammals almost a century ago (Adrian et al. 1932). The discharge of sympathetic outflow occurs as volleys of synchronized action potentials (APs). Even under conditions of supine rest, these volleys, or so-called "bursts," vary in discharge rate as well as in size. The variations in burst size are believed to be determined by spontaneous fluctuations in the number of axons being recruited per burst (Ninomya et al. 1993). Sundlof and Wallin (1978) demonstrated that such bursts in the muscle sympathetic nerve activity (MSNA) neurogram are synchronized to the cardiac cycle with an occurrence probability that is inversely related to blood ...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Baroreflex mechanisms regulating the occurrence of neural spikes in human muscle sympathetic nerve activity

Salmanpour

Shoemaker

2012

Journal of Neurophysiology

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“…During programmed stimulation-induced PVCs in healthy humans, significant modifications in neural discharge were presented as an increase in the amplitude and duration of the sympathetic burst immediately after the PVC (post-PVC burst) (9). The size of a postganglionic sympathetic burst reflects the number of active axons firing in that multiunit recording (22,26), as well as the size of the action potentials (APs). Recent work from our laboratories indicates the presence of a latent subpopulation of postganglionic sympathetic axons that generate large APs, are present during larger bursts, reflect faster conduction velocities, and are recruited with higher probability during severe chemoreflex (30) or baroreflex stress (26).…”

mentioning

confidence: 99%

“…The size of a postganglionic sympathetic burst reflects the number of active axons firing in that multiunit recording (22,26), as well as the size of the action potentials (APs). Recent work from our laboratories indicates the presence of a latent subpopulation of postganglionic sympathetic axons that generate large APs, are present during larger bursts, reflect faster conduction velocities, and are recruited with higher probability during severe chemoreflex (30) or baroreflex stress (26). The expression of such a subpopulation of latent, but large, APs during post-PVC sympathetic bursts remains to be established.…”

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confidence: 99%

Recruitment pattern of sympathetic muscle neurons during premature ventricular contractions in heart failure patients and controls

Maslov

Brešković

Brewer

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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Premature ventricular contractions (PVC) elicit larger bursts of multiunit muscle sympathetic nerve activity (MSNA), reflecting the ability to increase postganglionic axonal recruitment. We tested the hypothesis that chronic heart failure (CHF) limits the ability to recruit postganglionic sympathetic neurons as a response to PVC due to the excessive sympathetic activation in these patients. Sympathetic neurograms of sufficient signal-to-noise ratio were obtained from six CHF patients and from six similarly aged control individuals. Action potentials (APs) were extracted from the multiunit sympathetic neurograms during sinus rhythm bursts and during the post-PVC bursts. These APs were classified on the basis of the frequency per second, the content per burst, and the peak-to-peak amplitude, which formed the basis of binning the APs into active clusters. Compared with controls, CHF had higher APs per burst and higher number of active clusters per sinus rhythm burst (P < 0.05). Compared with sinus rhythm bursts, both groups increased AP frequency and the number of active clusters in the post-PVC burst (P < 0.05). However, compared with controls, the increase in burst integral, AP frequency, and APs per burst during the post-PVC burst was less in CHF patients. Nonetheless, the PVC-induced increase in active clusters per burst was similar between the groups. Thus, these CHF patients retained the ability to recruit larger APs but had a diminished ability to increase overall AP content.

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“…For example, in addition to the severe chemoreflex response discussed above, similar patterns have now been observed during -80 mmHg of LBNP (15) but less so during -60 mmHg lower body suction (236). Furthermore, in preliminary studies, Salmanpour et al (237) observed that all action potentials present at baseline exhibited faster conduction velocities during a Valsalva's maneuver, evidence perhaps for the possibility of malleable synaptic delays within the neural pathway.…”

Section: Characteristics Of Postganglionic Sympathetic Dischargementioning

confidence: 70%

Neural Control of Vascular Function in Skeletal Muscle

Shoemaker

Badrov

Al‐Khazraji

et al. 2015

Comprehensive Physiology

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The sympathetic nervous system represents a fundamental homeostatic system that exerts considerable control over blood pressure and the distribution of blood flow. This process has been referred to as neurovascular control. Overall, the concept of neurovascular control includes the following elements: efferent postganglionic sympathetic nerve activity, neurotransmitter release, and the end organ response. Each of these elements reflects multiple levels of control that, in turn, affect complex patterns of change in vascular contractile state. Primarily, this review discusses several of these control layers that combine to produce the integrative physiology of reflex vascular control observed in skeletal muscle. Beginning with three reflexes that provide somewhat dissimilar vascular patterns of response despite similar changes in efferent sympathetic nerve activity, namely, the baroreflex, chemoreflex, and muscle metaboreflex, the article discusses the anatomical and physiological bases of postganglionic sympathetic discharge patterns and recruitment, neurotransmitter release and management, and details of regional variations of receptor density and responses within the microvascular bed. Challenges are addressed regarding the fundamentals of measurement and how conclusions from one response or vascular segment should not be used as an indication of neurovascular control as a generalized physiological dogma. Whereas the bulk of the article focuses on the vasoconstrictor function of sympathetic neurovascular integration, attention is also given to the issues of sympathetic vasodilation as well as the impact of chronic changes in sympathetic activation and innervation on vascular health. © 2016 American Physiological Society.

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Relationship between size and latency of action potentials in human muscle sympathetic nerve activity

Cited by 55 publications

References 27 publications

Baroreflex mechanisms regulating the occurrence of neural spikes in human muscle sympathetic nerve activity

Baroreflex mechanisms regulating the occurrence of neural spikes in human muscle sympathetic nerve activity

Recruitment pattern of sympathetic muscle neurons during premature ventricular contractions in heart failure patients and controls

Neural Control of Vascular Function in Skeletal Muscle

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