Baroreflex resetting of human sympathetic action potential subpopulations during exercise

This study tested the hypothesis that during fatiguing volitional exercise in humans, descending cortical signals and ascending skeletal muscle metaboreflex signals exert divergent control over baroreflex resetting of sympathetic action potential (AP) discharge. We quantified the baroreflex gain for sympathetic AP clusters within the muscle sympathetic nerve activity neurogram (peroneal microneurography and continuous wavelet transform) during baseline (BSL), the first 2-min of a 5-min isometric handgrip (20% of maximal effort; IHG1), the last 2-min of IHG (IHG2), and during postexercise circulatory occlusion (PECO) in seven healthy participants. AP baroreflex threshold gain was measured as the slope of the linear relationship between AP probability (%) versus diastolic blood pressure (DBP; mmHg) for 10 normalized AP clusters. Compared with BSL, during IHG1, AP baroreflex threshold functions were only reset to greater DBP and baroreflex gain was unaffected. Compared with BSL, during IHG2 and PECO, baroreflex functions were reset to greater DBP and to greater AP firing probabilities, with medium-sized APs demonstrating the largest upward resetting (e.g., cluster 3 BSL: 26 ± 7%, cluster 3 IHG2: 78 ± 22%, cluster 3 PECO: 88 ± 46%). Compared with BSL, AP baroreflex threshold gain was not different during IHG2 but was increased during PECO, with medium-sized APs demonstrating the largest increase in baroreflex gain (e.g., cluster 3 BSL: -6.31 ± 3.1%/mmHg, cluster 3 IHG2: -6.18 ± 5.4%/mmHg, cluster 3 PECO: -12.13 ± 6.5%/mmHg). These findings indicate that during IHG exercise, descending cortical signaling and ascending skeletal muscle metaboreceptor signals differentially affect baroreflex resetting of subpopulations of human muscle sympathetic postganglionic neurons.NEW & NOTEWORTHY This study provides new insight to baroreflex resetting of MSNA during exercise in humans. Both fatiguing IHG and PECO reset baroreflex control of sympathetic APs to higher blood pressures and greater MSNA. However, only PECO increased baroreflex threshold gain of medium-sized sympathetic APs, an effect that was concealed when focusing on the integrated MSNA neurogram to quantify baroreflex gain. These data suggest that descending central versus ascending muscle metaboreflex mechanisms differentially affect baroreflex resetting of sympathetic APs.

Medienart:	E-Artikel

Erscheinungsjahr:	2023
Erschienen:	2023

Enthalten in:	Zur Gesamtaufnahme - volume:129
Enthalten in:	Journal of neurophysiology - 129(2023), 4 vom: 01. Apr., Seite 927-936

Sprache:	Englisch

Beteiligte Personen:	Klassen, Stephen A [VerfasserIn] Badrov, Mark B [VerfasserIn] Moir, M Erin [VerfasserIn] Shoemaker, J Kevin [VerfasserIn]

Links:	Volltext

Themen:	Baroreflex resetting Central command Isometric handgrip exercise Journal Article Muscle metaboreflex Muscle sympathetic nerve activity Research Support, Non-U.S. Gov't

Anmerkungen:	Date Completed 17.04.2023 Date Revised 14.06.2023 published: Print-Electronic figshare: 10.6084/m9.figshare.22117871 Citation Status MEDLINE

doi:	10.1152/jn.00347.2022

funding:
Förderinstitution / Projekttitel:

PPN (Katalog-ID):	NLM35453095X