Key result
Topical application of capsaicin-based analgesic balm significantly attenuated blood pressure and muscle sympathetic nerve activity increases during postexercise ischemia in healthy men (P<0.05).
Why the study?
Does topical capsaicin attenuate blood pressure and muscle sympathetic nerve activity responses to isolated muscle metaboreflex activation in healthy men?
Does topical capsaicin attenuate blood pressure and muscle sympathetic nerve activity responses to isolated muscle metaboreflex activation in healthy men?
p-value: p=< 0.05
Topical capsaicin attenuates blood pressure and sympathetic responses during isolated muscle metaboreflex activation, suggesting TRPv1 receptors contribute to the exercise pressor reflex in humans.
May blunt metaboreflex pressor responses in healthy adults; leaves open therapeutic relevance in hypertension or HF.
The exercise pressor reflex (EPR) is comprised of group III and IV skeletal muscle afferents and is one of the principal mediators of the cardiovascular response to exercise. In animals, capsaicin-based analgesic balm (CAP) attenuates the pressor response to muscle contraction, indicating the transient receptor potential vanilloid 1 (TRPv1) receptor (localized on the group IV afferent neuron) as an important mediator of the EPR. However, whether these findings can be extrapolated to humans remains unknown. Here, we tested the hypothesis that CAP would attenuate blood pressure (BP) and muscle sympathetic nerve activity (MSNA) responses to isolated muscle metaboreflex activation in healthy men. MSNA (microneurography) and beat-to-beat heart hate (HR, by electrocardiography), and BP (finger photoplethysmography) were continuously measured in eight healthy males (23 ± 5 yr) at rest, during isometric handgrip exercise, and during postexercise ischemia (PEI). Trials were performed before and 30 and 60 min after the topical application of CAP (0.1%, CAPZASIN-HP) over the volar forearm of the subject's exercising arm. Isometric exercise evoked increases in mean BP (∆32 ± 4 mmHg) and MSNA (∆26 ± 5 bursts/min; ∆19 ± 5 bursts/100 heart beats). The increases in BP during handgrip were not affected by CAP, but the increase in MSNA was lower after 60 min of CAP application. During PEI, the increases in BP and MSNA were all significantly less than those before CAP (all P < 0.05). In conclusion, CAP attenuated BP and sympathetic responses evoked by PEI in humans. These data provide evidence that transient receptor potential vanilloid 1 receptors potentially contribute to the EPR in humans, via its metabolic component. NEW & NOTEWORTHY We found that topical application of capsaicin-based analgesic balm attenuates arterial blood pressure and muscle sympathetic nerve activity during isolated muscle metaboreflex activation following isometric handgrip exercise in healthy humans. These findings suggest that the transient receptor potential vanilloid 1 may contribute to the exercise pressor reflex in humans via its metabolic component.
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Vianna et al. (2018) studied Healthy (n=8). Capsaicin-based analgesic balm vs. Before application (baseline) was evaluated on Blood pressure and muscle sympathetic nerve activity increases during postexercise ischemia (p=< 0.05). Topical application of capsaicin-based analgesic balm significantly attenuated blood pressure and muscle sympathetic nerve activity increases during postexercise ischemia in healthy men (P<0.05).
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