{"title":"Skinny (lower) legs run fast marathons.","authors":"Alexander C Berry, L Bruce Gladden","doi":"10.1113/EP093503","DOIUrl":"https://doi.org/10.1113/EP093503","url":null,"abstract":"","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145707836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Physiology of lived experience: Cruising among the Swiss peaks.","authors":"Grégoire P Millet","doi":"10.1113/EP093451","DOIUrl":"https://doi.org/10.1113/EP093451","url":null,"abstract":"","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145707850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Physiology of Lived Experience: And then there was one - the story of a radical nephrectomy.","authors":"Michael J Shattock","doi":"10.1113/EP093520","DOIUrl":"https://doi.org/10.1113/EP093520","url":null,"abstract":"","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145699993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Oliver Hayman, Rosiered Brownson-Smith, Elliott I Atkinson, Padraig Spillane, Stuart Baker, Stuart Goodall, Glyn Howatson, Kevin Thomas, Paul Ansdell
Synaptic input to the motoneuron pool is altered during fatiguing muscle contractions. In humans, the corticospinal tract is often studied, with equivocal findings regarding its role in the reduction of force. To date, the involvement of the reticulospinal tract during states of fatigue has not been explored. Fourteen participants (28 ± 6 years, nine males) visited the laboratory twice, first for a familiarisation, then for an experimental trial. Participants completed a 5-min sustained elbow flexor contraction at an intensity eliciting 40% of the EMG recorded during a maximal isometric voluntary contraction (MVC). Before, during and after the contraction, transcranial magnetic stimulation and electrical cervicomedullary stimulation were used to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials during the silent period (SP-CMEPs), respectively, with CMEPs also being evoked in combination with a startling acoustic sound (CMEPcon). Electrical stimulation of the brachial plexus was used to evoke maximal compound action potentials of the elbow flexors (Mmax). The 5-min contraction induced a 53% loss of force (P < 0.001), with no change in background EMG (∼4% Mmax, P = 0.293). Neither MEP amplitude (P = 0.246) nor CMEPcon ratio (P = 0.489) was altered during the contraction, whereas CMEP and SP-CMEP amplitudes were reduced by ∼20% and 50%, respectively (P < 0.001) and remained depressed post-task. The results suggest that neither corticospinal nor reticulospinal tract excitability was altered during a 5-min constant-EMG task at 40% maximal EMG. Instead, the aetiology of the neural contribution to fatigability appeared to be primarily related to the loss of motoneuron excitability.
{"title":"Corticospinal, reticulospinal and motoneuronal contributions to fatigability during a sustained contraction of the elbow flexors.","authors":"Oliver Hayman, Rosiered Brownson-Smith, Elliott I Atkinson, Padraig Spillane, Stuart Baker, Stuart Goodall, Glyn Howatson, Kevin Thomas, Paul Ansdell","doi":"10.1113/EP093193","DOIUrl":"https://doi.org/10.1113/EP093193","url":null,"abstract":"<p><p>Synaptic input to the motoneuron pool is altered during fatiguing muscle contractions. In humans, the corticospinal tract is often studied, with equivocal findings regarding its role in the reduction of force. To date, the involvement of the reticulospinal tract during states of fatigue has not been explored. Fourteen participants (28 ± 6 years, nine males) visited the laboratory twice, first for a familiarisation, then for an experimental trial. Participants completed a 5-min sustained elbow flexor contraction at an intensity eliciting 40% of the EMG recorded during a maximal isometric voluntary contraction (MVC). Before, during and after the contraction, transcranial magnetic stimulation and electrical cervicomedullary stimulation were used to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials during the silent period (SP-CMEPs), respectively, with CMEPs also being evoked in combination with a startling acoustic sound (CMEPcon). Electrical stimulation of the brachial plexus was used to evoke maximal compound action potentials of the elbow flexors (M<sub>max</sub>). The 5-min contraction induced a 53% loss of force (P < 0.001), with no change in background EMG (∼4% M<sub>max</sub>, P = 0.293). Neither MEP amplitude (P = 0.246) nor CMEPcon ratio (P = 0.489) was altered during the contraction, whereas CMEP and SP-CMEP amplitudes were reduced by ∼20% and 50%, respectively (P < 0.001) and remained depressed post-task. The results suggest that neither corticospinal nor reticulospinal tract excitability was altered during a 5-min constant-EMG task at 40% maximal EMG. Instead, the aetiology of the neural contribution to fatigability appeared to be primarily related to the loss of motoneuron excitability.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145676894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Cooling down for going up: Could selective 'brain chilling' mitigate high-altitude illness?","authors":"Adnan Haq, Damian M Bailey","doi":"10.1113/EP093165","DOIUrl":"https://doi.org/10.1113/EP093165","url":null,"abstract":"","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145676915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Annaëlle Couvert, Mélanie Rance, Eric Doré, Vincent Martin, Duane Beraud, Claire Morel, Bruno Pereira, Antonio Herbert Lancha, Nathalie Boisseau
This study investigated the acute effects of two isoenergetic high-intensity interval exercise (HIIE) sessions, running (HIIE-RUN) and cycling (HIIE-BIKE), on post-exercise oxygen consumption ( ), carbon dioxide production ( ), substrate oxidation and 24-h energy intake (EI) in men with overweight or obesity. Twelve fasted men (44.4 ± 14.5 years; body mass index: 28.3 ± 1.9 kg m-2) completed both HIIE sessions. and were measured before, during and after exercise, while substrate oxidation was calculated before and after exercise. The rate of perceived exertion was recorded during each exercise. Appetite was assessed throughout each session using a visual analogue scale (VAS) and EI was recorded via a 24-h dietary questionnaire. Both exercise modalities resulted in similar energy expenditure (EE), but HIIE-BIKE elicited a significantly higher respiratory exchange ratio (P = 0.002). No significant effect of exercise modality or time × modality interaction was observed for and EE during the post-exercise period. Fat oxidation was significantly increased during recovery compared with the pre-exercise levels (P < 0.001), but did not differ between modalities. Appetite and 24-h EI were unaffected by the exercise modality. In men with overweight or obesity, isoenergetic HIIE-RUN and HIIE-BIKE seem to induce comparable post-exercise , EE and substrate oxidation during the 2-h recovery period. Both modalities similarly promoted fat oxidation without specific dietary compensation observed.
本研究探讨了跑步（HIIE- run）和骑自行车（HIIE- bike）两种等能高强度间歇运动（HIIE）对超重或肥胖男性运动后耗氧量（V / O 2 ${dot V_{{ mathm {O}}_2}}}$）、二氧化碳生成（V / C 2 ${ mathm {O}}_2}} $）、底物氧化和24小时能量摄入（EI）的急性影响。12名禁食的男性（44.4±14.5岁；体重指数：28.3±1.9 kg m-2）完成了两个HIIE疗程。测定运动前、运动中、运动后的v_2 ${dot V_{{mathrm{O}}_2}}}$和v_2 ${dot V_{mathrm{C}}{{mathrm{O}}_2}}}$，同时测定运动前后底物氧化量。在每次运动中记录感知运动的速率。在每个疗程中使用视觉模拟量表（VAS）评估食欲，并通过24小时饮食问卷记录EI。两种运动方式导致相似的能量消耗（EE），但HIIE-BIKE引起显著更高的呼吸交换比（P = 0.002）。运动方式和时间-模态交互作用对运动后脑电强度和脑电强度无显著影响。与运动前水平（P V O 2 ${dot V_{{ mathm {O}}_2}}}$）相比，恢复期间脂肪氧化显著增加，EE和底物氧化在2 h恢复期间显著增加。两种方式同样促进脂肪氧化，没有特定的饮食补偿观察到。
{"title":"Acute metabolic responses to high-intensity interval training in men with overweight or obesity: Does the exercise modality matter?","authors":"Annaëlle Couvert, Mélanie Rance, Eric Doré, Vincent Martin, Duane Beraud, Claire Morel, Bruno Pereira, Antonio Herbert Lancha, Nathalie Boisseau","doi":"10.1113/EP093045","DOIUrl":"10.1113/EP093045","url":null,"abstract":"<p><p>This study investigated the acute effects of two isoenergetic high-intensity interval exercise (HIIE) sessions, running (HIIE-RUN) and cycling (HIIE-BIKE), on post-exercise oxygen consumption ( <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <msub><mi>O</mi> <mn>2</mn></msub> </msub> <annotation>${dot V_{{{mathrm{O}}_2}}}$</annotation></semantics> </math> ), carbon dioxide production ( <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><mi>C</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${dot V_{{mathrm{C}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> ), substrate oxidation and 24-h energy intake (EI) in men with overweight or obesity. Twelve fasted men (44.4 ± 14.5 years; body mass index: 28.3 ± 1.9 kg m<sup>-2</sup>) completed both HIIE sessions. <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <msub><mi>O</mi> <mn>2</mn></msub> </msub> <annotation>${dot V_{{{mathrm{O}}_2}}}$</annotation></semantics> </math> and <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <mrow><mi>C</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${dot V_{{mathrm{C}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> were measured before, during and after exercise, while substrate oxidation was calculated before and after exercise. The rate of perceived exertion was recorded during each exercise. Appetite was assessed throughout each session using a visual analogue scale (VAS) and EI was recorded via a 24-h dietary questionnaire. Both exercise modalities resulted in similar energy expenditure (EE), but HIIE-BIKE elicited a significantly higher respiratory exchange ratio (P = 0.002). No significant effect of exercise modality or time × modality interaction was observed for <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <msub><mi>O</mi> <mn>2</mn></msub> </msub> <annotation>${dot V_{{{mathrm{O}}_2}}}$</annotation></semantics> </math> and EE during the post-exercise period. Fat oxidation was significantly increased during recovery compared with the pre-exercise levels (P < 0.001), but did not differ between modalities. Appetite and 24-h EI were unaffected by the exercise modality. In men with overweight or obesity, isoenergetic HIIE-RUN and HIIE-BIKE seem to induce comparable post-exercise <math> <semantics> <msub><mover><mi>V</mi> <mo>̇</mo></mover> <msub><mi>O</mi> <mn>2</mn></msub> </msub> <annotation>${dot V_{{{mathrm{O}}_2}}}$</annotation></semantics> </math> , EE and substrate oxidation during the 2-h recovery period. Both modalities similarly promoted fat oxidation without specific dietary compensation observed.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145653999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L Madden Brewster, Travis Dylan Gibbons, Hannah Grace Caldwell, Connor A Howe, Jennifer S Duffy, Andrew R Steele, Justin A Monteleone, Jay M J R Carr, Jodie Lauren Koep, Tenasia D R Monaghan, David B MacLeod, Philip N Ainslie
<p><p>Stability in cerebral oxygen extraction fraction (OEF) is typically determined by alterations in cerebral blood flow (CBF). At rest, arterial partial pressure of carbon dioxide ( <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> ) and OEF exhibit a strong inverse relationship owing to the powerful influence of <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> on cerebral resistance, CBF and therefore oxygen delivery; however, it is unclear whether this relationship also exists during exercise, especially when supramaximal, during which marked hyperventilation-induced reductions in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> induce cerebrovascular vasoconstriction and lower CBF. We determined whether: (1) supramaximal exercise yields the largest change in OEF versus lower intensities, correlated with reductions in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> ; and (2) declines in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> (independent of exercise) determine changes in OEF. Blood was sampled from the brachial/radial artery and internal jugular vein during: (1) 60 min, 34% maximal O<sub>2</sub> uptake (SUB; n = six males, six females); (2) 4 min, 90% maximal O<sub>2</sub> uptake (MAX; n = six males, six females); (3) 1-2 min of high-intensity sprinting, ∼110% maximal O<sub>2</sub> uptake (HIS; n = six males, five females); and (4) resting hyperventilation-induced hypocapnia (HYPO; n = six males, five females). OEF was calculated as: [ <math> <semantics> <mrow><mrow><mo>(</mo> <mrow><mrow><mi>arterial</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mspace></mspace> <mi>content</mi></mrow> <mo>-</mo> <mrow><mi>jugular</mi> <mspace></mspace> <mi>venous</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mspace></mspace> <mi>content</mi></mrow> </mrow> <mo>)</mo></mrow> <mo>/</mo> <mrow><mi>arterial</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mrow><mspace></mspace> <mi>content</mi></mrow> <mo>]</mo> <mspace></mspace> <mo>×</mo> <mspace></mspace> <mn>100</mn> <mo>.</mo></mrow> </mrow> <annotation>$( {{mathrm{arterial;}}{{mathrm{O}}_2}{mathrm{;content}} - {mathrm{jugular;venous;}}{{mathrm{O}}_2}{mathrm{;content}}} )/{mathrm{arterial;}}{{mathrm{O}}_2}{mathrm{;content}}]; times ;100.$</annotation></se
脑氧萃取分数（OEF）的稳定性通常由脑血流量（CBF）的变化决定。休息时，动脉血分压（paco2 ${P_{ mathm {aC}}{{ mathm {O}}_2}}}$）与OEF呈强烈的反比关系，这是由于paco2 ${P_{ mathm {aC}}{{ mathm {O}}_2}}}$对脑阻力、CBF和供氧量的强大影响；然而，尚不清楚这种关系是否也存在于运动中，特别是在超极限运动中，在超极限运动中，过度通气导致的paco2 ${P_{mathrm{aC}}{{mathrm{O}}_2}}}$明显减少导致脑血管收缩和CBF降低。我们确定：(1)与低强度运动相比，最高强度运动是否产生最大的OEF变化，与P aC o2 ${P_{ mathm {aC}}{{ mathm {O}}_2}}}$的减少相关；(2) P aC o2 ${P_{mathrm{aC}}{{mathrm{O}}_2}}}$的下降（与运动无关）决定了OEF的变化。取肱动脉/桡动脉和颈内静脉血样：(1)60 min，最大摄氧量34% （n = 6男，6女）；(2) 4 min， 90%最大摄氧量（MAX; n = 6男，6女）；(3) 1-2分钟的高强度冲刺，约110%的最大氧摄取（HIS; n = 6男，5女）；静息过度通气诱导的低碳酸血症（HYPO; n = 6男，5女）。OEF计算为：[（动脉o2含量-颈静脉o2含量）/动脉o2含量]× 100。$ ({{ mathrm{动脉。}}{{ mathrm {O}} _2} { mathrm{;内容}}- { mathrm{颈;静脉}}{{ mathrm {O}} _2} { mathrm{;内容}}})/ { mathrm{动脉。}}{{ mathrm {O}} _2} { mathrm{;内容}}]; ; 100年。$ ΔOEF在HIS[估计边际平均值：15.6%(95%置信区间：12.4,18.8)]和HYPO[17.7%(14.5, 20.9)]期间最大，而SUB [-0.9% (-4.0, 2.1)]；p < 0.0001 （vs. HIS和vs. HYPO）和MAX [2.5% (-0.5, 5.6)；p < 0.0001, vs. HIS和vs. HYPO]。与MAX [-6.2 mmHg(-7.8, -4.6)]和SUB [1.4 mmHg(-0.2, 2.9)]相比，Δ P aC o2 $Delta {P_{{mathrm{aC}}{{mathrm{O}}}}$在HIS [-12.9 mmHg(-14.6, -11.2)]和HYPO [-9.2 mmHg(-10.9, -7.6)]中减少最多；所有比较p < 0.0001]。在混合分析中，ΔOEF与Δ P aC O 2 $Delta {P_{mathrm{aC}}{{mathrm{O}}_2}} $呈负相关[β = -1.65 (-2.23, -1.07)；P < 0.0001]，并在每个条件内。总之，可能是由于CBF的减少，低碳酸血症本身以类似于超极限冲刺的方式增加了OEF，表明运动在这个过程中不是强制性的。
{"title":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\">Cerebral oxygen extraction across different exercise intensities: Role of arterial <ns0:math> <ns0:semantics><ns0:msub><ns0:mi>P</ns0:mi> <ns0:mrow><ns0:mi>C</ns0:mi> <ns0:msub><ns0:mi>O</ns0:mi> <ns0:mn>2</ns0:mn></ns0:msub> </ns0:mrow> </ns0:msub> <ns0:annotation>${P_{{mathrm{C}}{{mathrm{O}}_2}}}$</ns0:annotation></ns0:semantics></ns0:math>.","authors":"L Madden Brewster, Travis Dylan Gibbons, Hannah Grace Caldwell, Connor A Howe, Jennifer S Duffy, Andrew R Steele, Justin A Monteleone, Jay M J R Carr, Jodie Lauren Koep, Tenasia D R Monaghan, David B MacLeod, Philip N Ainslie","doi":"10.1113/EP092724","DOIUrl":"https://doi.org/10.1113/EP092724","url":null,"abstract":"<p><p>Stability in cerebral oxygen extraction fraction (OEF) is typically determined by alterations in cerebral blood flow (CBF). At rest, arterial partial pressure of carbon dioxide ( <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> ) and OEF exhibit a strong inverse relationship owing to the powerful influence of <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> on cerebral resistance, CBF and therefore oxygen delivery; however, it is unclear whether this relationship also exists during exercise, especially when supramaximal, during which marked hyperventilation-induced reductions in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> induce cerebrovascular vasoconstriction and lower CBF. We determined whether: (1) supramaximal exercise yields the largest change in OEF versus lower intensities, correlated with reductions in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> ; and (2) declines in <math> <semantics><msub><mi>P</mi> <mrow><mi>aC</mi> <msub><mi>O</mi> <mn>2</mn></msub> </mrow> </msub> <annotation>${P_{{mathrm{aC}}{{mathrm{O}}_2}}}$</annotation></semantics> </math> (independent of exercise) determine changes in OEF. Blood was sampled from the brachial/radial artery and internal jugular vein during: (1) 60 min, 34% maximal O<sub>2</sub> uptake (SUB; n = six males, six females); (2) 4 min, 90% maximal O<sub>2</sub> uptake (MAX; n = six males, six females); (3) 1-2 min of high-intensity sprinting, ∼110% maximal O<sub>2</sub> uptake (HIS; n = six males, five females); and (4) resting hyperventilation-induced hypocapnia (HYPO; n = six males, five females). OEF was calculated as: [ <math> <semantics> <mrow><mrow><mo>(</mo> <mrow><mrow><mi>arterial</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mspace></mspace> <mi>content</mi></mrow> <mo>-</mo> <mrow><mi>jugular</mi> <mspace></mspace> <mi>venous</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mspace></mspace> <mi>content</mi></mrow> </mrow> <mo>)</mo></mrow> <mo>/</mo> <mrow><mi>arterial</mi> <mspace></mspace></mrow> <msub><mi>O</mi> <mn>2</mn></msub> <mrow><mrow><mspace></mspace> <mi>content</mi></mrow> <mo>]</mo> <mspace></mspace> <mo>×</mo> <mspace></mspace> <mn>100</mn> <mo>.</mo></mrow> </mrow> <annotation>$( {{mathrm{arterial;}}{{mathrm{O}}_2}{mathrm{;content}} - {mathrm{jugular;venous;}}{{mathrm{O}}_2}{mathrm{;content}}} )/{mathrm{arterial;}}{{mathrm{O}}_2}{mathrm{;content}}]; times ;100.$</annotation></se","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145653903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mariana Brizuela, Anuja R Bony, Sonia Garcia-Caraballo, David J Adams, Stuart M Brierley
Chronic visceral pain is a key symptom of irritable bowel syndrome. Modulation of voltage-gated calcium and potassium channels by G protein-coupled receptors plays a key role in dampening nociceptive transmission. Both baclofen and the analgesic peptide α-conotoxin Vc1.1 activate GABAB receptors (GABABR), resulting in inhibition of CaV2.2 and CaV2.3 calcium channels to reduce colonic nociception. Recent studies have also shown that GABABR activation potentiates G-protein-coupled inwardly rectifying potassium (GIRK)-1/2 channels in mammalian sensory afferent neurons. In this study, we investigated the expression of these ion channel targets in rodent and human dorsal root ganglion (DRG) neurons, including those innervating the colon. We examined how CaV2.2 and GIRK channel antagonists, as well as a GIRK channel activator, influence the passive and active electrical properties of adult mouse DRG neurons. We also assessed the effects of α-conotoxin Vc1.1 on neuronal excitability in the presence of the selective CaV2.2 antagonist ω-conotoxin CVIE and the GIRK channel activator ML297. We further evaluated the impact of the GIRK channel antagonist tertiapin-Q on excitability in mouse colonic DRGs and afferents and explored the role of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Our findings demonstrate that both CaV2.2 inhibition and GIRK channel potentiation reduce excitability in mouse DRGs, likely mediating the antinociceptive effects of Vc1.1 and baclofen observed in vivo. However, GIRK channel potentiation appears to play only a limited role in modulating excitability in colon-innervating DRGs and colonic afferents. These findings suggest that neurons innervating different body regions use distinct mechanisms to regulate excitability and nociceptive signalling.
{"title":"GABA<sub>B</sub> receptor-mediated modulation of sensory neuron excitability: Roles of Ca<sub>V</sub>2.2, G-protein-coupled inwardly rectifying potassium (GIRK) channels, and hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels in human and mouse nociception.","authors":"Mariana Brizuela, Anuja R Bony, Sonia Garcia-Caraballo, David J Adams, Stuart M Brierley","doi":"10.1113/EP093318","DOIUrl":"https://doi.org/10.1113/EP093318","url":null,"abstract":"<p><p>Chronic visceral pain is a key symptom of irritable bowel syndrome. Modulation of voltage-gated calcium and potassium channels by G protein-coupled receptors plays a key role in dampening nociceptive transmission. Both baclofen and the analgesic peptide α-conotoxin Vc1.1 activate GABA<sub>B</sub> receptors (GABA<sub>B</sub>R), resulting in inhibition of Ca<sub>V</sub>2.2 and Ca<sub>V</sub>2.3 calcium channels to reduce colonic nociception. Recent studies have also shown that GABA<sub>B</sub>R activation potentiates G-protein-coupled inwardly rectifying potassium (GIRK)-1/2 channels in mammalian sensory afferent neurons. In this study, we investigated the expression of these ion channel targets in rodent and human dorsal root ganglion (DRG) neurons, including those innervating the colon. We examined how Ca<sub>V</sub>2.2 and GIRK channel antagonists, as well as a GIRK channel activator, influence the passive and active electrical properties of adult mouse DRG neurons. We also assessed the effects of α-conotoxin Vc1.1 on neuronal excitability in the presence of the selective Ca<sub>V</sub>2.2 antagonist ω-conotoxin CVIE and the GIRK channel activator ML297. We further evaluated the impact of the GIRK channel antagonist tertiapin-Q on excitability in mouse colonic DRGs and afferents and explored the role of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Our findings demonstrate that both Ca<sub>V</sub>2.2 inhibition and GIRK channel potentiation reduce excitability in mouse DRGs, likely mediating the antinociceptive effects of Vc1.1 and baclofen observed in vivo. However, GIRK channel potentiation appears to play only a limited role in modulating excitability in colon-innervating DRGs and colonic afferents. These findings suggest that neurons innervating different body regions use distinct mechanisms to regulate excitability and nociceptive signalling.</p>","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145647842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fergus K O'Connor, Surendran Sabapathy, Aaron J E Bach, Bryce N Balmain, Llion Roberts, Norman R Morris
{"title":"From mechanistic promise to clinical translation: Passive heat therapy as a cardiovascular and functional adjunct in ageing and disease.","authors":"Fergus K O'Connor, Surendran Sabapathy, Aaron J E Bach, Bryce N Balmain, Llion Roberts, Norman R Morris","doi":"10.1113/EP093511","DOIUrl":"https://doi.org/10.1113/EP093511","url":null,"abstract":"","PeriodicalId":12092,"journal":{"name":"Experimental Physiology","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145630455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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