Quantifying sympathetic nerve activity: problems, pitfalls and the need for standardization

Abstract

Since the first recording of sympathetic nerve activity (SNA) early last century, numerous methods for presentation of the resulting data have developed. In this paper, we discuss the common ways of describing SNA and their application to chronic recordings. Suggestions on assessing the quality of SNA are made, including the use of arterial pressure wave-triggered averages and nasopharyngeal stimuli. Calculation of the zero level of the SNA signal from recordings during ganglionic blockade, the average level between bursts and the minimum of arterial pressure wave-triggered averages are compared and shown to be equivalent. The use of normalization between zero and maximal SNA levels to allow comparison between groups is discussed. We recommend that measured microvolt levels of integrated SNA be presented (with the zero/noise level subtracted), along with burst amplitude and frequency information whenever possible. We propose that standardization of the quantifying/reporting of SNA will allow better comparison between disease models and between research groups and ultimately allow data to be more reflective of the human situation.

Recording sympathetic nerve activity chronically in rats: surgery techniques, assessment of nerve activity, and quantification

“…A characteristic of renal, splanchnic, and lumbar SNA is the presence of pulse-synchronous or cardiac cycle-related nerve bursts (10,22). Figure 2 illustrates a chronic telemetry-based recording of renal SNA from a rat using Data Sciences International F50-W-F2 and PA-C40 transmitters (see online supplement for corresponding audio clip).…”

“…Within this report, we provide examples of lumbar, renal, and splanchnic SNA recordings. A second proof-of-concept method to confirm the presence of sympathetic bursts is to determine whether the activity is cardiac cycle related (10,22). This analysis can be performed two ways: 1) subjectively by visual inspection of the location of the sympathetic burst relative to the cardiac cycle or pulsatile blood pressure or 2) spike-triggered averaging of the rectified nerve signal from the start of each cardiac cycle (Fig.…”

“…A common experimental manipulation to test the presence of sympathetic bursts is ganglionic blockade or baroreflex loading (7,10,22). For example, IV administration of ganglionic blockers (i.e., chlorisondamine or hexamethonium) will block neurotransmission between pre-and postganglionic neurons and result in an abrupt cessation of the sympathetic burst activity, pulse-synchronous activity, and cardiac cycle-related activity (Fig.…”

“…For dissection of the nerve, there are several techniques that can improve long-term viability: 1) ensure a constant bathing of the dissection site in warmed, sterile saline (37.5°C); 2) choose a 2-to 3-mm section of nerve that is free of incoming blood supply; 3) avoid damage to nearby lymph vessels or blood vessels that will produce leakage of fluid into the area; 4) gently isolate the selected nerve section from the surrounding tissue using fine, straight forceps (No. 5 micro-dissecting tweezers, Roboz Surgical Instrument, Rockville, MA) or fine, round-ended, straight glass probes (made by pulling 100-l glass pipets over a flame and melting the broken ends into a rounded shape); and 5) take great care not to stretch, pick up, pull, or touch the nerve section during the dissection (10,13,22,25).…”

Possibilities of Pharmacological Correction of Structural and Functional Alterations of Microcirculation in Terms of Endothelial Dysfunction in Comorbid Patients Suffered Stroke Event

“…О р и г и н а л ь н ы е и с с л е д о в а н и я Амплитуда симпатической активности отражает число задействованных нервных волокон, а ее частота -ак-тивность центральной генерации и / или входов от ре-цепторов [4]. В ряде фундаментальных работ, посвя-щенных вопросам регуляции сосудистого тонуса, показано, что этот механизм является базовым в под-держании гомеостаза на уровне МЦ и обеспечивает взаимосвязь между функциональной активностью микрососудов и уровнем гемоперфузии органа и / или ткани в определенную единицу времени [5][6][7][8].…”