Acute intermittent hypoxia significantly increased multiunit muscle sympathetic nerve activity burst incidence from 33 to 43 bursts per 100 heartbeats and increased action potential discharge rates compared to baseline normoxia.
Does acute intermittent hypoxia increase muscle sympathetic nerve activity and action potential discharge rates in healthy adults?
Acute intermittent hypoxia increases muscle sympathetic nerve activity by increasing action potential discharge rates and within-burst firing, partially mediated by carotid chemoreceptors.
Absolute Event Rate: 43% vs 33%
p-value: p=<0.01
We examined the effect of acute intermittent hypoxia (IH) on sympathetic neural firing patterns and the role of the carotid chemoreceptors. We hypothesized exposure to acute IH would increase muscle sympathetic nerve activity (MSNA) via an increase in action potential (AP) discharge rates and within-burst firing. We further hypothesized any change in discharge patterns would be attenuated during acute chemoreceptor deactivation (hyperoxia). MSNA (microneurography) was assessed in 17 healthy adults (11 male/6 female; 31 ± 1 yr) during normoxic rest before and after 30 min of experimental IH. Prior to and following IH, participants were exposed to 2 min of 100% oxygen (hyperoxia). AP patterns were studied from the filtered raw MSNA signal using wavelet-based methodology. Compared with baseline, multiunit MSNA burst incidence ( P 0.05); however, hyperoxia following IH attenuated the probability of particular AP clusters firing more than once per burst ( P < 0.01). Acute IH increases MSNA by increasing AP discharge rates and within-burst firing. A portion of the increase in within-burst firing following IH can be attributed to the carotid chemoreceptors. These data advance the mechanistic understanding of sympathetic activation following acute IH in humans.
Ott et al. (Wed,) conducted a other in Healthy adults (n=17). Acute intermittent hypoxia vs. Baseline normoxia was evaluated on Multiunit MSNA burst incidence (bursts/100 heartbeats) (p=<0.01). Acute intermittent hypoxia significantly increased multiunit muscle sympathetic nerve activity burst incidence from 33 to 43 bursts per 100 heartbeats and increased action potential discharge rates compared to baseline normoxia.