American journal of physiology. Regulatory, integrative and comparative physiology最新文献

{"title":"DETERMINING AUTONOMIC SYMPATHETIC TONE AND REACTIVITY USING BAEVSKY'S STRESS INDEX.","authors":"Jan D Huizinga, Ji-Hong Chen, Amer Hussain, Difei Zheng, Lijun Liu, Hansel Lui, Maxwell Pan, Xurui Chen, Brienna DiBattista, Marzia Alam, Julia Niro","doi":"10.1152/ajpregu.00243.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00243.2024","url":null,"abstract":"<p><p>The extrinsic autonomic nervous system is critical in controlling most organ functions and is involved in the pathophysiology of many chronic diseases. However, its assessment plays a minor role in the clinical practice of diagnosis and treatment outside cardiology. Since sympathetic dysfunction is related to diseases such as diabetes, chronic stress, and urinary and gastrointestinal motor dysfunction, an autonomic assessment is warranted. Here, we evaluate the Baevsky Stress Index (SI) to assess sympathetic tone and reactivity based on heart rate variability. We start with discussing Baevsky's original stress index. We propose an optimized calculation of SI and assess the SI of 73 self-declared healthy subjects in the age groups 16-35, 35-50, and 50+ at supine baseline and in response to postural change from supine to standing. Normality assessment and kernel density analysis identified two subgroups: one we deemed to have normal autonomic functioning, and an outlier group with significantly higher baseline sympathetic index (SI) and sympathetic reactivity to standing. Using a Gaussian mixture model, we determined normal SI values and values for autonomic stress and autonomic dysfunction. This study provides a needed start to evaluate sympathetic dysfunction using heart rate variability.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143514413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exercise Pressor Reflex Function Is Augmented in Rats with Chronic Kidney Disease.","authors":"Han-Kyul Kim, Juan Estrada, Ayumi Fukazawa, Amane Hori, Gary A Iwamoto, Scott A Smith, Masaki Mizuno, Wanpen Vongpatanasin","doi":"10.1152/ajpregu.00234.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00234.2024","url":null,"abstract":"<p><p>Cardiovascular responses to exercise are exaggerated in chronic kidney disease (CKD) patients. Enhanced sympathetic activation is thought to play a role with the exercise pressor reflex (EPR), a reflex originating in contracting muscle, modulating this response. Previous studies suggest an overactive EPR in CKD patients as indicated by muscle sympathetic overactivation during static handgrip exercise. However, the role of the EPR could not be fully elucidated due to experimental constraints inherent to humans. The purpose of this study was to specifically test EPR function in a CKD animal model. Male Sprague-Dawley rats were assigned to a diet containing 0.25% adenine to induce CKD or a control diet. Mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) responses to activation of the EPR, including its functional components, the mechanoreflex and metaboreflex, were assessed in decerebrate, unanesthetized animals after feeding 10 to 14 weeks. Plasma creatinine was significantly higher in CKD rats compare to controls (1.80±0.78 vs. 0.34±0.02 mg·dl^-1, <i>P</i> = 0.017). MAP and RSNA responses to muscle contraction (i.e., EPR activation) were potentiated in CKD rats compared to controls (Δ=36±19 vs. 17±8 mmHg, <i>P</i> = 0.014 and Δ=159±62 vs. 64±54 %, <i>P</i> = 0.004, respectively). Similarly, the pressor and sympathetic responses to passive muscle stretch (i.e., mechanoreflex stimulation) were significantly higher in CKD than in control animals. Intraarterial capsaicin administration (i.e., metaboreflex activation) induced an augmented pressor response in CKD rats, compared with controls. Our findings suggest that the EPR, stimulated by the mechano- and metaboreflex, is exaggerated in CKD.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143490567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat-producing thermoeffector plasticity in response to prolonged iterative exposure to a high heat-loss environment: No indication of thermoregulatory fatigue.","authors":"Maaike I Moes, Antonis Elia, Ola Eiken, Michail E Keramidas","doi":"10.1152/ajpregu.00310.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00310.2024","url":null,"abstract":"<p><p>Previous studies have suggested that, during prolonged cold exposure, shivering thermogenesis may gradually be attenuated, supposedly reflecting a state of central fatigue (aka \"thermoregulatory fatigue\") provoked by extended shivering activity, that precipitates hypothermia. The purpose of this study was to revisit the validity of this notion. Twelve noncold-acclimatized men participated in three ∼10-h sessions, during which they performed repeatedly three 120-min cold-water immersions. To induce discrete amounts of heat-producing thermoeffector output, presumptively leading to distinct levels of fatigue during each session, subjects were submersed, within each session, in either severely (15°C), moderately (20°C), or slightly (28°C) cold water. The cold-induced elevation in thermogenic rate was similar across the three repeated immersions performed within the 15°C (˜130 W･m2) and 20°C (˜100 W･m2) sessions (P ≥ 0.43). In the 28°C-session, the metabolic heat production was augmented by ˜7% in the second and third immersions compared to in the first immersion (P=0.01). No intrasession differences were noted with regards to the body-core cooling rate, the cold-induced drop in skin temperature and forearm cutaneous vascular conductance, or the stress-hormone (salivary α- amylase and cortisol concentrations) and thermoperceptual responses (P>0.05). The present findings, therefore, demonstrate that the ability to generate heat remains intact during prolonged iterative exposure to a high-heat loss environment in a single day, regardless of the severity of cold stressor. The intermittent application of slight cold stress (i.e., 28°C water) appears to mediate metabolic sensitization, reflecting either the circadian rhythmicity of heat-producing thermoeffector activity, or perhaps the rapid induction of metabolic adaptation.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143466665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Knockdown of the type 1 cannabinoid receptor in the central amygdala increases both spontaneous and water deprivation-induced sodium intake in rats.","authors":"S G Ruginsk, M P Greenwood, M Greenwood, L L K Elias, D Murphy, J Antunes-Rodrigues","doi":"10.1152/ajpregu.00241.2024","DOIUrl":"https://doi.org/10.1152/ajpregu.00241.2024","url":null,"abstract":"<p><p>Important inputs originating in the forebrain circumventricular organs and also in the central amygdala (CeA) trigger essential water deprivation (WD)-induced behaviors, such as thirst and sodium appetite. Together with the secretion of the neurohypophysial peptides vasopressin (AVP) and oxytocin (OT), these behavioral responses seek to maintain the normalcy of ECF osmolality and volume. Within this context, the main hypothesis tested by the present study was that CeA type 1 cannabinoid receptors (CB1Rs) were essential for the maintenance of body fluid homeostasis, particularly in response to WD challenge. We found that CeA CB1R knockdown increased spontaneous and WD-induced hypertonic saline intake, without significantly impacting water ingestion. In euhydrated rats, despite unaltered urinary volume, CB1R knockdown reduced urinary osmolality, as well diminished urinary nitrate concentrations, suggesting reduced renal sodium excretion. No relevant changes were induced by CeA CB1R knockdown on urinary parameters following WD-induced rehydration, which is consistent with unaltered AVP and OT mRNA transcription and hormone release under the same experimental conditions. Taken together, the present data support the notion that CeA CB1Rs participate in both spontaneous and WD-induced NaCl intake, without significantly affecting neuroendocrine output. Given the well described facilitatory CeA role on natriorexigenic responses, and the reported interplay between CB1Rs and gamma aminobutyric acid (GABA) within the CeA, the present findings suggest that CB1Rs may indirectly regulate sodium appetite through effects on CeA GABAergic neurotransmission.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143447613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Skeletal muscle inosine monophosphate formation preserves ΔG_ATP during incremental step contractions in vivo.","authors":"Zoe H Smith, Christopher M T Hayden, Kate L Hayes, Jane A Kent","doi":"10.1152/ajpregu.00192.2024","DOIUrl":"10.1152/ajpregu.00192.2024","url":null,"abstract":"<p><p>The cause and consequences of inosine monophosphate (IMP) formation when adenosine triphosphate (ATP) declines during muscular contractions in vivo are not fully understood. The purpose of this study was to examine the role of IMP formation in the maintenance of the Gibbs free energy for ATP hydrolysis (ΔG_ATP) during dynamic contractions of increasing workload and the implications of ATP loss in vivo. Eight males (median 27.5, 25-35 yr range) completed an 8-min incremental protocol [2-min stages of isotonic knee extensions (0.5 Hz)] in a 3-T magnetic resonance (MR) system. Phosphorus MR spectra were obtained from the knee extensor muscles at rest and during contractions and recovery. Although the ATP demand during contractions was met primarily by oxidative phosphorylation, [ATP] decreased from 8.2 mM to 7.5 (range 6.4-8.0) mM and [IMP] increased from 0 mM to 0.6 (0.1-1.7) mM. Modeling showed that, in the absence of IMP formation, excess adenosine diphosphate (ADP) would result in a less favorable ΔG_ATP (<i>P</i> < 0.001). Neither [ATP] nor [IMP] had returned to baseline following 10 min of recovery (<i>P</i> < 0.001). Notably, Δ[ATP] was linearly related to the post-contraction reduction in muscle oxidative capacity (<i>r</i> = 0.74, <i>P</i> = 0.037). Our results highlight the importance of IMP formation in preserving cellular energy status by avoiding increases in ADP above that necessary to stimulate energy production pathways. However, the consequence of IMP formation was an incomplete recovery of [ATP], which in turn was related to decreased muscle oxidative capacity following contractions. These results likely have implications for the capacity to generate adequate energy during repeated bouts of muscular work.<b>NEW & NOTEWORTHY</b> An ∼9% decline in [ATP] led to the formation of inosine monophosphate (IMP) during submaximal muscular contractions. Modeling revealed IMP formed to preserve a favorable energy state (ΔG_ATP) by minimizing large increases in [ADP], whereas the loss of [ATP] did not alter ΔG_ATP. [ATP] did not recover by 10 min, and the loss of [ATP] was associated with a reduced oxidative capacity, providing a new link between [ATP] loss and an impaired energetic capacity in vivo.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R195-R205"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142869284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Separate and combined blockades of α- and β-adrenergic receptors in forearm sweating induced by adrenergic agents and exercise in the heat in young adults.","authors":"Tatsuro Amano, Naoto Fujii, Glen P Kenny, Toby Mündel, Yoshimitsu Inoue, Shotaro Yokoyama, Narihiko Kondo","doi":"10.1152/ajpregu.00120.2024","DOIUrl":"10.1152/ajpregu.00120.2024","url":null,"abstract":"<p><p>The assessment of adrenergic modulation of sweating as assessed via pharmacologic administration of α- and β-adrenergic receptor blockers during exercise has yielded mixed findings. However, the underlying mechanisms for this disparity remain unresolved. We investigated the effects of separate and combined blockade of α- and β-adrenergic receptors on forearm sweating induced by a 30-min moderate-intensity exercise bout (<i>n</i> = 17, <i>protocol 1</i>) and the administration of adrenergic agonists epinephrine and norepinephrine (<i>n</i> = 16, <i>protocol 2</i>) in the heat. Adrenergic receptor blockade was induced via the separate and combined iontophoretic administration of terazosin (α-adrenergic receptor antagonist) and propranolol (β-adrenergic receptor antagonist) on forearm skin. Bretylium, a noradrenergic sympathetic nerve inhibitor, was also administered separately in <i>protocol 1</i>. In <i>protocol 1</i>, relative to the separate administration of propranolol, terazosin alone or in combination with propranolol attenuated exercise sweating to a similar extent (both <i>P</i> ≤ 0.037), although the effect was reduced relative to that observed with bretylium treatment (<i>P</i> < 0.001). In <i>protocol 2</i>, administration of propranolol increased norepinephrine- (<i>P</i> = 0.029) but not epinephrine-induced sweat rate. The combined administration of terazosin reversed this response, attenuating sweating (<i>P</i> < 0.001) to a greater extent than terazosin treatment alone (<i>P</i> = 0.030). Altogether, we showed that although β-adrenergic receptors may interact with α-adrenergic receptors pharmacologically, it does not appear to modulate exercise-induced sweating on the forearm. Furthermore, α- but not β-adrenergic receptors independently modulate the regulation of forearm sweating during exercise in the heat. Finally, the bretylium-induced reduction in forearm sweat rate during exercise likely occurs independently of α- and β-adrenergic receptors.<b>NEW & NOTEWORTHY</b> Pharmacological stimulation of α- and β-adrenergic receptors produces sweating in vivo. Still, the separate and interactive roles of these adrenergic receptors during exercise and pharmacological adrenergic stimulation in the heat remain unknown. We showed that β-adrenergic receptors may interact with α-adrenergic receptors pharmacologically, but it does not modulate exercise-induced sweating. The α-adrenergic receptors independently modulate sweating during exercise in the heat. We provide important new insights into our understanding of the mechanisms regulating human sweating.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R181-R194"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142869283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swimming induces physiological cardioprotection associated with pro-growth versus anti-inflammatory influences in extracardiac organs.","authors":"Boris P Budiono, Jelena Vider, Ali Zaid, Jason N Peart, Eugene F Du Toit, John P Headrick, Luke J Haseler","doi":"10.1152/ajpregu.00139.2024","DOIUrl":"10.1152/ajpregu.00139.2024","url":null,"abstract":"<p><p>Physical activity improves myocardial structure, function, and resilience via complex, incompletely defined mechanisms. We explored the effects of 1- to 2-wk swim training on cardiac and systemic phenotype in young male C57Bl/6 mice. Two-week forced swimming (90 min twice daily) resulted in cardiac hypertrophy (22% increase in heart:body weight, <i>P</i> < 0.01), with improved inotropy (22% higher left ventricular +dP/d<i>t</i>, <i>P</i> < 0.01) and functional tolerance to ischemia-reperfusion (I-R) (40%-50% reductions in stunning and diastolic dysfunction, <i>P</i> < 0.01; without changes in cell death assessed from enzyme loss) in Langendorff perfused hearts. Initial Western immunoblot analysis indicated no shifts in cardiac expression of determinants of autophagy (LC3A/B), mitochondrial biogenesis/dynamics (PGC-1α, MFN-1, and OPA-1), or stress signaling (caveolin-3 and GSK-3β). Furthermore, no changes in cardiac cytokines (IL-1b, IL-6, IL-10, IL-12, GM-CSF, TNF-α, and IFN-γ) were detected in multiplex immunoassays. Exploratory profiling of RTK phosphorylation provided evidence for moderately increased activity of receptors involved in cardiac/coronary growth and protection (insulin, IGF-1, FGF R2, Tie-2, PDGFβ, and EphB4), together with a fall in M-CSF R and ephrin sub-type receptor phosphorylation. Swimming increased growth factor while reducing inflammatory mediators across extracardiac tissues [brain, pancreas, thymus, lymph nodes, and white adipose tissue (WAT)]. This included a pattern of increased LIF, VEGF, and pentraxin-2 versus reduced CXCL2/MIP-2a, chitinase 3-like 1, CCL6, MMP9, CD40/TNFRSF5, and IGFBP6 in multiple tissues, and a shift to a pro-browning profile in WAT. In summary, swimming produces integrated systemic benefits, improving cardiac growth, inotropy, and resilience in association with increased growth factor and reduced inflammatory and lipogenic mediators in multiple tissues.<b>NEW & NOTEWORTHY</b> Swimming may induce cardiac and systemic benefits distinct from other modes of physical activity. We show that 2-wk forced swim training increases cardiac growth, contractility, and functional resilience to ischemia in hearts of male mice. This is associated with increased growth factor levels and reduced inflammatory and lipogenic protein profiles in peripheral tissues.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R206-R219"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142942643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of different intensity aerobic exercise on remodeling immune microenvironment of adipose tissue in obesity mouse.","authors":"Zhimin Lu, Chang Meng, JinRu Yang, Xuecong Wang, Xueying Li, Jie Zhang, Xuewen Tian, Qinglu Wang","doi":"10.1152/ajpregu.00227.2024","DOIUrl":"10.1152/ajpregu.00227.2024","url":null,"abstract":"<p><p>Obesity can change the immune microenvironment of adipose tissue and induce inflammation. This study is dedicated to exploring the internal mechanism by which different intensities of exercise reprogram the immune microenvironment of epididymal adipose tissue in nutritionally obese mice. C57BL/6J male obese mouse models were constructed by high-fat diet, which were respectively obese control group (OC), moderate-intensity continuous exercise group (HF-M), high-intensity continuous exercise group (HF-H), and high-intensity intermittent exercise group (HF-T). The exercise group was subjected to aerobic exercise intervention for 8 wk, and samples of mice were collected at the fourth and eighth week, respectively. Mice blood, liver, and adipose tissue of the epididymis were collected for index detection and adipose tissue ordinary transcriptome sequencing. After exercise intervention, when compared with the OC group, the morphology and blood indexes of the exercise groups were significantly improved. The liver lipid content was decreased, adipose tissue inflammation was reduced, and the mRNA and protein expression levels of <i>IL-1β</i>, <i>F4/80</i>, and <i>CD64</i> in adipose tissue were significantly decreased (<i>P</i> < 0.01). Among the three exercise groups, the effect of the HF-T group was more significant. When compared with the OC group, fibroblast-specific marker genes, neutrophil marker genes, macrophage marker genes, and immune-related signaling pathways were significantly downregulated in the HF-T group. Exercise can reshape the immune microenvironment of adipose tissue, and high-intensity intermittent aerobic exercise is the most effective.<b>NEW & NOTEWORTHY</b> The present study has revealed that obesity is capable of altering the immune microenvironment within adipose tissue, thereby giving rise to inflammation. It has been demonstrated that exercise holds the potential to reverse the onset of inflammatory responses, with high-intensity intermittent aerobic exercise emerging as the most efficacious approach.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R220-R234"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142913652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of nocturnal oxygen enrichment on high-altitude acclimatization.","authors":"Alejandro M Rosales, Walter S Hailes, Christopher W Collins, Mark L McGlynn, Brent C Ruby, Dustin R Slivka","doi":"10.1152/ajpregu.00251.2024","DOIUrl":"10.1152/ajpregu.00251.2024","url":null,"abstract":"<p><p>Nocturnal oxygen enrichment improves sleep at high altitudes but may impair acclimatization. Our purpose was to determine if nocturnal oxygen enrichment impacts acclimatization. A 7-day acclimatization protocol occurred at a field-based research site between 0 and 4,200 m. Participants were housed at 2,800 m and slept with ([Formula: see text], 32.3 ± 2.5% O₂) or without ([Formula: see text], 20.8 ± 0.1% O₂) nocturnal oxygen enrichment. Resting and steady-state cycling (5-min, 1.75 W·kg^-1) tests occurred on <i>Day 0</i> (0 m) and <i>Days 1</i>, <i>4</i>, and <i>7</i> (2,800 m). Sleep, <i>vastus lateralis</i> muscle oxygenation [oxygenated hemoglobin (O₂Hb), deoxygenated hemoglobin (HHb)], arterial blood oxygen saturation ([Formula: see text]), heart rate (HR), and expired gases were measured. Five daily hikes from 2,800 to 4,200 m were also completed. Sleep was longer (<i>P</i> = 0.028) and overnight [Formula: see text] higher (<i>P</i> < 0.001) in the [Formula: see text] (452 ± 63 min, 96 ± 1%) than the [Formula: see text] group (427 ± 63 min, 91 ± 2%). The [Formula: see text] and [Formula: see text] groups did not differ at rest in ΔO₂Hb (-1.47 ± 0.99, -1.46 ± 1.30 A.U., <i>P</i> = 0.901), ΔHHb (0.78 ± 0.84, 0.51 ± 0.96 A.U., <i>P</i> = 0.202), [Formula: see text] (93 ± 3, 93 ± 3%, <i>P</i> = 1.000), HR (59 ± 6, 64 ± 13 beats·min^-1, <i>P</i> = 0.229), respiratory exchange ratio (RER, 0.81 ± 0.07, 0.79 ± 0.06, <i>P</i> = 0.274), and ventilation body temperature pressure saturated (BTPS) (10.56 ± 2.12, 10.80 ± 1.96 L·min^-1, <i>P</i> = 0.717). The [Formula: see text] and [Formula: see text] groups also did not differ while cycling in ΔO₂Hb (-2.96 ± 3.03, -1.70 ± 3.46 A.U., <i>P</i> = 0.278), ΔHHb (7.59 ± 4.65, 6.34 ± 3.21 A.U., <i>P</i> = 0.451), [Formula: see text] (90 ± 6, 89 ± 6%, <i>P</i> = 0.875), HR (113 ± 10, 118 ± 16 beats·min^-1, <i>P</i> = 0.408), RER (0.89 ± 0.06, 0.89 ± 0.07, <i>P</i> = 0.756), and ventilation BTPS (54.00 ± 15.42, 60.18 ± 18.42 L·min^-1, <i>P</i> = 0.371). [Formula: see text] while cycling returned toward <i>Day 0</i> (0 m) values by <i>Day 7</i> (2,800 m) in both groups (<i>P</i> < 0.001) indicating short-term acclimatization. Nocturnal oxygen enrichment improves sleep but does not impair short-term acclimatization when completing daily prolonged exercise.<b>NEW & NOTEWORTHY</b> This work examined the impact of nocturnal oxygen enrichment on short-term high-altitude acclimatization to 2,800 m while completing daily hikes to 4,200 m. Recurrently dampening the required hypoxic stimulus for acclimatization via nocturnal oxygen enrichment improved sleep but did not impair short-term high-altitude acclimatization. This was evinced through ventilatory and cardiovascular adjustments that improved arterial blood oxygen saturation after 7 days.</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R172-R180"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142852101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intradermal electrical stimulation of sudomotor nerves and local sweat rate.","authors":"Gary W Mack, Kaylee M Bahr, Christian J McEwan, Carson J Price, Ashton J Renfro","doi":"10.1152/ajpregu.00229.2024","DOIUrl":"10.1152/ajpregu.00229.2024","url":null,"abstract":"<p><p>The local sweat rate (LSR) response to intradermal electrical stimulation generates a sigmodal stimulus-response curve with a peak sweat rate generated during a 30-s period of continuous stimuli at a frequency of 16-32 Hz. However, the in vivo firing pattern of the sudomotor nerve resembles more of a bursting pattern. We tested the hypothesis that a bursting pattern during intradermal electrical stimulation would result in a greater sweating response than the regular continuous stimulus pattern. Fifteen subjects were studied in a temperature-controlled room at 27.6 ± 0.2°C. The LSR was measured with a miniature sweat capsule with guide sleeves for holding the intradermal stimulating electrodes. The nine continuous stimulus frequencies (0.2, 1, 2, 4, 8, 12, 16, 32, and 64 Hz) were compared to a bursting pattern with a similar total number of stimuli. The sweating response was determined as the area under the ∆LSR-time curve. Peak ∆LSR was slightly higher for the continuous stimuli (0.396 ± 0.242 mg·min^-1·cm^-2, <i>P</i> = 0.023) than for the bursting stimuli (0.356 ± 0.244 mg·min^-1·cm^-2). The sigmoidal-shaped stimulus-response curves, however, were significantly different (<i>P</i> = 0.0007). The stimulus frequency producing 50% of peak LSR (EC₅₀, <i>P</i> = 0.0029) was higher during continuous stimulation and the Hill slope was lower (<i>P</i> < 0.0001) during bursting stimuli. These data do not support the concept that a bursting stimulus pattern during intradermal electrical stimulation evokes a greater ∆LSR.<b>NEW & NOTEWORTHY</b> Neuron discharge variability can offer some advantages to a downstream physiological response. We examined this possibility with respect to sudomotor nerve activity and local sweat rate. Variable neuron discharge activity, induced by intradermal electrical stimulation, did not have an impact on the peak local sweat rate but did reduce the time to sweating onset and the stimulus intensity required to reach 50% of peak sweating (EC₅₀).</p>","PeriodicalId":7630,"journal":{"name":"American journal of physiology. Regulatory, integrative and comparative physiology","volume":" ","pages":"R154-R160"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142869282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}