scholarly journals Effects of auricular electrical stimulation on vagal activity in healthy men: evidence from a three-armed randomized trial

2010 ◽  
Vol 118 (8) ◽  
pp. 537-546 ◽  
Author(s):  
Roberto La Marca ◽  
Marko Nedeljkovic ◽  
Lizhuang Yuan ◽  
Andreas Maercker ◽  
Ulrike Ehlert
Keyword(s):  
Electrical Stimulation ◽  
Randomized Trial ◽  
Therapeutic Intervention ◽  
Random Order ◽  
Vagal Afferents ◽  
Vagal Activity ◽  
Manual Acupuncture ◽  
Sinus Arrhythmia ◽  
Healthy Men ◽  
Auricular Electrical Stimulation

The activity of the VN (vagus nerve) is negatively associated with risk factors such as stress and smoking, morbidity and mortality. In contrast, it is also a target of therapeutic intervention. VN stimulation is used in depression and epilepsy. Because of its high invasivity and exclusive application to therapy-resistant patients, there is interest in less invasive methods affecting the VN. Several studies examining acupuncture report beneficial effects on vagal activity. However, findings are inconsistent, and applied methods are heterogeneous resulting in difficulties in interpretation. The purpose of the present study was evaluation of the effects of acupuncture on vagal activity in a three-armed randomized trial while controlling several disturbing factors. Fourteen healthy men participated in random order in four examinations: a control condition without intervention, a condition with placebo, manual acupuncture and electroacupuncture. Acupuncture was conducted on the concha of the ear, as there is neuroanatomical evidence for vagal afferents. Each examination took place once, with a week's time between examinations. RSATR (respiratory sinus arrhythmia adjusted for tidal volume) indicating vagal activity was measured continuously. The study was conducted partially blind in accordance with recommendations. After controlling for respiration, condition-specific pain sensation, individual differences in belief of acupuncture effectiveness and time effects not attributable to the interventions, electroacupuncture but not manual acupuncture was found to have a positive effect on RSATR. The results underline the potential role of auricular electrical stimulation to induce an increase in vagal activity, and it therefore might be used as preventive or adjuvant therapeutic intervention promoting health.

Direct effect of PaCO2 on respiratory sinus arrhythmia in conscious humans

2002 ◽  
Vol 282 (3) ◽  
pp. H973-H976 ◽  
Author(s):  
Nobuko Sasano ◽  
Alex E. Vesely ◽  
Junichiro Hayano ◽  
Hiroshi Sasano ◽  
Ron Somogyi ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Direct Effect ◽  
Respiratory Sinus Arrhythmia ◽  
Random Order ◽  
Mean Amplitude ◽  
Frequency Component ◽  
Pulmonary Gas Exchange ◽  
High Frequency Component ◽  
Sinus Arrhythmia ◽  
End Tidal

Respiratory sinus arrhythmia (RSA) may improve the efficiency of pulmonary gas exchange by matching the pulmonary blood flow to lung volume during each respiratory cycle. If so, an increased demand for pulmonary gas exchange may enhance RSA magnitude. We therefore tested the hypothesis that CO2directly affects RSA in conscious humans even when changes in tidal volume (VT) and breathing frequency ( F B), which indirectly affect RSA, are prevented. In seven healthy subjects, we adjusted end-tidal Pco 2 (Pet CO2 ) to 30, 40, or 50 mmHg in random order at constant VT and F B. The mean amplitude of the high-frequency component of R-R interval variation was used as a quantitative assessment of RSA magnitude. RSA magnitude increased progressively with Pet CO2 ( P < 0.001). Mean R-R interval did not differ at Pet CO2 of 40 and 50 mmHg but was less at 30 mmHg ( P < 0.05). Because VT and F B were constant, these results support our hypothesis that increased CO2directly increases RSA magnitude, probably via a direct effect on medullary mechanisms generating RSA.

scholarly journals Metabolic, Cardiac, and Hemorheological Responses to Submaximal Exercise under Light and Moderate Hypobaric Hypoxia in Healthy Men

Biology ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 144
Author(s):  
Hun-Young Park ◽  
Jeong-Weon Kim ◽  
Sang-Seok Nam
Keyword(s):  
Oxygen Uptake ◽  
Blood Lactate ◽  
Minute Ventilation ◽  
Random Order ◽  
Cycle Ergometer ◽  
Submaximal Exercise ◽  
Erythrocyte Deformability ◽  
Moderate Hypoxia ◽  
Healthy Men ◽  
Significant Difference

We compared the effects of metabolic, cardiac, and hemorheological responses to submaximal exercise under light hypoxia (LH) and moderate hypoxia (MH) versus normoxia (N). Ten healthy men (aged 21.3 ± 1.0 years) completed 30 min submaximal exercise corresponding to 60% maximal oxygen uptake at normoxia on a cycle ergometer under normoxia (760 mmHg), light hypoxia (596 mmHg, simulated 2000 m altitude), and moderate hypoxia (526 mmHg, simulated 3000 m altitude) after a 30 min exposure in the respective environments on different days, in a random order. Metabolic parameters (oxygen saturation (SPO2), minute ventilation, oxygen uptake, carbon dioxide excretion, respiratory exchange ratio, and blood lactate), cardiac function (heart rate (HR), stroke volume, cardiac output, and ejection fraction), and hemorheological properties (erythrocyte deformability and aggregation) were measured at rest and 5, 10, 15, and 30 min after exercise. SPO2 significantly reduced as hypoxia became more severe (MH > LH > N), and blood lactate was significantly higher in the MH than in the LH and N groups. HR significantly increased in the MH and LH groups compared to the N group. There was no significant difference in hemorheological properties, including erythrocyte deformability and aggregation. Thus, submaximal exercise under light/moderate hypoxia induced greater metabolic and cardiac responses but did not affect hemorheological properties.

Responses of medullary raphespinal neurons to electrical stimulation of thoracic sympathetic afferents, vagal afferents, and to other sensory inputs in cats

1991 ◽  
Vol 66 (6) ◽  
pp. 2084-2094 ◽  
Author(s):  
R. W. Blair ◽  
A. R. Evans
Keyword(s):  
Electrical Stimulation ◽  
Neuronal Activity ◽  
Vagal Stimulation ◽  
Discharge Rate ◽  
Stellate Ganglion ◽  
Cell Activity ◽  
Conditioning Stimulus ◽  
Vagal Afferents ◽  
Early Peak ◽  
Stimulation Of

1. Medullary raphespinal neurons antidromically activated from the T2-T5 segments were tested for responses to electrical stimulation of cervical vagal and thoracic sympathetic afferents (by stimulating the left stellate ganglion), somatic probing, auditory stimuli, and visual stimuli in cats anesthetized with alpha-chloralose. A total of 99 neurons in the raphe nuclei were studied; the locations of 76 cells were histologically confirmed. Neurons were located in raphe magnus (RM, 65%), raphe obscurus (RO, 32%), and raphe pallidus (RPa, 4%). The mean conduction velocity of these neurons was 62 +/- 2.9 (SE) m/s with a range of 1.1-121 m/s. 2. A total of 60/99 tested neurons responded to electrical stimulation of sympathetic afferents. Quantitation of responses was obtained for 55 neurons. With one exception, all responsive neurons were excited and exhibited an early burst of spikes with a mean latency of 16 +/- 1.2 ms. From a spontaneous discharge rate of 5.2 +/- 1.2 spikes/s, neuronal activity increased by 2.9 +/- 0.3 spikes/stimulus. In addition to an early peak, 15 neurons (25%) exhibited a late burst of spikes with a latency of 182 +/- 12.9 ms; neuronal activity increased by 5.0 +/- 1.3 spikes/stimulus. Duration of the late peak (130 +/- 18.5 ms) was longer than for the early peak (18 +/- 0.7 ms), but threshold voltages for eliciting each peak were comparable. Sixteen of 29 spontaneously active neurons exhibited a postexcitatory depression of activity that lasted for 163 +/- 19.1 ms. All but one tested neuron in RO responded to stimulation of sympathetic afferents, but 65% of neurons in RM responded to this stimulus. 3. In response to vagal afferent stimulation, 19% of 57 neurons exhibited inhibition only, 11% were only excited, and 9% were either excited or inhibited, depending on the stimulus paradigm used; the remaining 61% of neurons were unresponsive. From a spontaneous rate of 7.9 +/- 3.8 spikes/s, excited cells increased their discharge rate by 1.6 +/- 0.3 spikes/stimulus. Activity of inhibited cells was reduced from 21.3 +/- 5.8 to 7.8 +/- 3.1 spikes/s. The conditioning-test (CT) technique was used to assess 11 neurons' responses. Stellate ganglion stimulation was the test stimulus, and vagal stimulation the conditioning stimulus. Vagal stimulation reduced the neuronal responses to stellate ganglion stimulation by an average of 50% with a CT interval of 60-100 ms, and cell responses returned to control after 300 ms. With spontaneous cell activity, low frequencies of vagal stimulation were generally excitatory, and high frequencies (10-20 Hz) inhibitory.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiorespiratory transfer during sleep: a study in healthy young men

1995 ◽  
Vol 269 (3) ◽  
pp. H952-H958 ◽  
Author(s):  
P. Van de Borne ◽  
P. Biston ◽  
M. Paiva ◽  
H. Nguyen ◽  
P. Linkowski ◽  
...  
Keyword(s):  
Breathing Pattern ◽  
Sleep Stages ◽  
Vagal Activity ◽  
Deep Sleep ◽  
Rapid Eye Movement Sleep ◽  
Nocturnal Sleep ◽  
Healthy Men ◽  
Consistent Increase ◽  
Respiratory Modulation ◽  
Light Sleep

This study tested the concept that changes in breathing parameters account for modifications in respiratory-related blood pressure (BP) and R-R interval (RRI) variability during nocturnal sleep. BP (Finapres), electrocardiogram, respiration (Respitrace), and polygraphic sleep recordings were recorded continuously in 13 healthy men aged 18-37 yr. The transfer characteristics identified by coherence and gain measures between the calibrated thoraco-abdominal motion and the respiratory-related BP and RRI variability evidenced a consistent increase during transitions from wake to light sleep and from light to deep sleep but returned to waking levels during rapid-eye-movement sleep (P < 0.0001). These changes were related to the specific modifications occurring in the respiratory rate, tidal volume, and ribcage-to-abdominal motion ratio during the different sleep stages (0.28 < r < 0.39; P < 0.0001). This study demonstrates 1) that modifications in the breathing pattern account for 8-15% of the variance in the cardiorespiratory transfer, and 2) that respiratory modulation of vagal activity is not the main mechanism controlling the magnitude of the respiratory-related BP and RRI variability during sleep.

scholarly journals Vascular and Inflammatory High Fat Meal Responses in Young Healthy Men; A Discriminative Role of IL-8 Observed in a Randomized Trial

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e53474 ◽  
Author(s):  
Diederik Esser ◽  
Els Oosterink ◽  
Jos op 't Roodt ◽  
Ronald M. A. Henry ◽  
Coen D. A. Stehouwer ◽  
...  
Keyword(s):  
Randomized Trial ◽  
High Fat ◽  
Healthy Men ◽  
Fat Meal

Responses of medullary raphe neurons to electrical and chemical activation of vagal afferent nerve fibers

1993 ◽  
Vol 70 (5) ◽  
pp. 1950-1961 ◽  
Author(s):  
A. R. Evans ◽  
R. W. Blair
Keyword(s):  
Electrical Stimulation ◽  
Chemical Activation ◽  
Vagal Afferents ◽  
Frequency Dependent ◽  
Afferent Fibers ◽  
Vagal Afferent ◽  
Mixed Responses ◽  
Excitatory Responses ◽  
Dose Dependent ◽  
Stimulation Of

1. Various intensities, frequencies, and pulse widths of electrical stimulation of vagal afferent fibers were used to assess the responses of 87 medullary raphe neurons to vagal afferent fiber input in pentobarbital sodium-anesthetized, barodenervated paralyzed cats. Thirty-seven neurons were antidromically activated from the T2-T3 segments of the thoracic spinal cord, and 40 neurons could not be antidromically activated. Neurons were located in the nucleus raphe magnus (79%) and the nucleus raphe obscurus (15%). The remaining 6% of the neurons were not found; however, their locations were comparable in depth and position on the midline with other neurons in the same animals whose locations were identified. 2. The responses of 60 neurons to electrical stimulation of vagal afferent fibers were classified as excitatory (38%), inhibitory (24%), or mixed, (7%). The mixed responses were characterized by excitation at one frequency or intensity and inhibition at another frequency or intensity. The remaining 27 neurons did not clearly respond. 3. The excitatory responses to electrical stimulation of the cervical vagus nerve were intensity and frequency dependent. Inhibitory responses were frequency dependent at lower frequencies of stimulation and both frequency and intensity dependent at higher frequencies. The mixed responses were frequency dependent. Overall, longer pulse widths produced significantly greater responses than shorter pulse widths. 4. Thirty-three neurons were tested for responses to chemical stimulation of vagal afferents with intra-atrial injections of three doses of veratridine. Twenty-one percent were excited, 55% were inhibited, and 6% had mixed responses. For the mixed responses, excitation occurred at one dose and inhibition at another. The remaining 18% of the neurons were unresponsive to veratridine. The excitatory responses were dose dependent, but the inhibitory responses were not. Three doses of phenybiguanide (PBG) were also used to chemically activate vagal afferents in 27 neurons. Eleven percent were excited, 44% were inhibited, and 4% had mixed responses. The remaining 41% were unresponsive to PBG. The excitatory and inhibitory responses were dose dependent. 5. When comparing responses in projection and nonprojection neurons, inhibition was seen significantly more often in projection neurons and excitation in nonprojection neurons. Sixty-three percent of the neurons inhibited by electrical stimulation were raphespinal neurons, and 78% of the neurons excited by vagal stimulation were nonprojection neurons. Similar observations were made with the responses to chemical activation of the vagus. 6. Neurons with lower spontaneous discharge rates were more often excited by vagal stimulation and neurons with higher rates were more often inhibited.(ABSTRACT TRUNCATED AT 400 WORDS)

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