Pharmacological assessment of the contribution of the arterial baroreflex to sympathetic discharge patterns in healthy humans

Jacqueline K. Limberg, Elizabeth P. Ott, Walter W. Holbein, Sarah E. Baker, Timothy B Curry, Wayne T. Nicholson, Michael Joseph Joyner, J. Kevin Shoemaker

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure with intravenous nitroprusside (NTP) and phenylephrine (PE) and measured action potential (AP) patterns with wavelet-based methodology. We hypothesized that 1) baroreflex unloading (NTP) would increase firing of low-threshold axons and recruitment of latent axons and 2) baroreflex loading (PE) would decrease firing of low-threshold axons. Heart rate (HR, ECG), arterial blood pressure (BP, brachial catheter), and muscle sympathetic nerve activity (MSNA, microneurography of peroneal nerve) were measured at baseline and during steady-state systemic, intravenous NTP (0.5-1.2 µg·kg-1·min-1, n = 13) or PE (0.2-1.0 µg·kg-1·min-1, n = 9) infusion. BP decreased and HR and integrated MSNA increased with NTP (P < 0.01). AP incidence (326 ± 66 to 579 ± 129 APs/100 heartbeats) and AP content per integrated burst (8 ± 1 to 11 ± 2 APs/burst) increased with NTP (P < 0.05). The firing probability of low-threshold axons increased with NTP, and recruitment of high-threshold axons was observed (22 ± 3 to 24 ± 3 max cluster number, 9 ± 1 to 11 ± 1 clusters/burst; P < 0.05). BP increased and HR and integrated MSNA decreased with PE (P < 0.05). PE decreased AP incidence (406 ± 128 to 166 ± 42 APs/100 heartbeats) and resulted in fewer unique clusters (15 ± 2 to 9 ± 1 max cluster number, P < 0.05); components of an integrated burst (APs or clusters per burst) were not altered (P > 0.05). These data support a hierarchical pattern of sympathetic neural activation during manipulation of baroreceptor afferent activity, with rate coding of active neurons playing the predominant role and recruitment/derecruitment of higher-threshold units occurring with steady-state hypotensive stress. NEW & NOTEWORTHY To study how changes in baroreceptor afferent activity affect patterns of sympathetic neural activation, we manipulated arterial blood pressure with intravenous nitroprusside and phenylephrine and measured sympathetic outflow with wavelet-based methodology. Baroreflex unloading increased sympathetic activity by increasing firing probability of low-threshold axons (rate coding) and recruiting new populations of high-threshold axons. Baroreflex loading decreased sympathetic activity by decreasing the firing probability of larger axons (derecruitment); however, the components of an integrated burst were unaffected.

Original languageEnglish (US)
Pages (from-to)2166-2175
Number of pages10
JournalJournal of Neurophysiology
Volume119
Issue number6
DOIs
StatePublished - Jun 1 2018

Fingerprint

Baroreflex
Nitroprusside
Axons
Phenylephrine
Pharmacology
Pressoreceptors
Arterial Pressure
Peroneal Nerve
Action Potentials
Electrocardiography
Arm
Catheters
Heart Rate
Neurons
Muscles
Population

Keywords

  • Baroreflex
  • Microneurography
  • Modified Oxford technique
  • Sympathetic outflow

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

Pharmacological assessment of the contribution of the arterial baroreflex to sympathetic discharge patterns in healthy humans. / Limberg, Jacqueline K.; Ott, Elizabeth P.; Holbein, Walter W.; Baker, Sarah E.; Curry, Timothy B; Nicholson, Wayne T.; Joyner, Michael Joseph; Kevin Shoemaker, J.

In: Journal of Neurophysiology, Vol. 119, No. 6, 01.06.2018, p. 2166-2175.

Research output: Contribution to journalArticle

Limberg, Jacqueline K. ; Ott, Elizabeth P. ; Holbein, Walter W. ; Baker, Sarah E. ; Curry, Timothy B ; Nicholson, Wayne T. ; Joyner, Michael Joseph ; Kevin Shoemaker, J. / Pharmacological assessment of the contribution of the arterial baroreflex to sympathetic discharge patterns in healthy humans. In: Journal of Neurophysiology. 2018 ; Vol. 119, No. 6. pp. 2166-2175.
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