Static muscular contraction elicits a pressor reflex in the chicken

1997 ◽  
Vol 272 (3) ◽  
pp. R759-R765 ◽  
Author(s):  
I. C. Solomon ◽  
T. P. Adamson
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Sciatic Nerve ◽  
Arterial Pressure ◽  
Gastrocnemius Muscle ◽  
Muscular Contraction ◽  
Arterial Blood ◽  
Static Contraction ◽  
Stimulation Of

Static muscular contraction has been shown to increase arterial blood pressure and heart rate in humans and other mammals. It is not clear, however, whether birds exhibit a similar response to this maneuver. Therefore, we designed these experiments to determine if the chicken exhibits a cardiovascular response to static muscular contraction and if the observed responses are evoked through a reflex involving muscle afferents. Static contraction of the gastrocnemius muscle was evoked by electrically stimulating the sciatic nerve at 1.5-3.0 times motor threshold (30-40 Hz; 0.025 ms) in 13 chloralose-anesthetized cockerels. We measured arterial blood pressure and muscle tension before and during static contraction and calculated mean arterial pressure and heart rate from the arterial pressure trace. We found that static contraction of the gastrocnemius muscle increased mean arterial pressure from 71 +/- 4 to 95 +/- 4 mmHg (P < 0.05) and increased heart rate from 304 +/- 8 to 345 +/- 10 beats/min (P < 0.05). Furthermore, we found that stimulation of the sciatic nerve after paralysis of the birds with vecuronium bromide or stimulation of the cut peripheral end of the sciatic nerve (using the same stimulation parameters described above) evoked no change in mean arterial pressure or heart rate. We conclude that static muscular contraction of the gastrocnemius muscle in the chicken elicits a pressor response and that this response is due to a reflex arising from the contracting muscles.

scholarly journals Acute Cardiovascular Effects of Epidural Spinal Cord Stimulation

2007 ◽  
Vol 5;10 (9;5) ◽  
pp. 677-685
Author(s):  
David M. Schultz
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Spinal Cord Stimulation ◽  
Statistical Significance ◽  
Cold Pressor Test ◽  
Cold Pressor ◽  
Arterial Blood

Background: Several animal studies support the contention that thoracic spinal cord stimulation (SCS) might decrease arterial blood pressure. Objective: To determine if electrical stimulation of the dorsal spinal cord in humans will lower mean arterial pressure (MAP) and heart rate (HR). Design: Case Series Methods: Ten normotensive subjects that were clinically indicated for SCS testing were studied. Two of the 10 patients who underwent testing were excluded from the analysis because they did not respond to the Cold Pressor Test (CPT). Systolic blood pressure, diastolic blood pressure, and heart rate were measured continuously at the wrist (using the Vasotrac device). SCS was administered with quadripolar leads implanted into the epidural space under fluoroscopic guidance. SCS was randomly performed either in the T1-T2 or T5-T6 region of the spinal cord during normal conditions as well as during transient stress induced by CPT. The CPT was conducted by immersing the non-dominant hand in ice-cold water for 2 minutes. Results: There were moderate decreases in MAP and HR during SCS at the T5-T6 region compared to baseline that did not reach statistical significance. However, SCS at the T1-T2 region tended to increase MAP and HR compared to baseline but the change did not reach statistical significance. Arterial blood pressure was transiently elevated by 9.4 ± 3.8 mmHg using CPT during the control period with SCS turned off and also during SCS at either the T1-T2 region or T5-T6 region of the spinal cord (by 9.2 ± 5 mmHg and 10.7 ± 8.4 mmHg, respectively). During SCS at T5-T6, the CPT significantly increased MAP by 5.9±7.1 mmHg compared to control CPT (SCS off). Conclusion: This study demonstrated that SCS at either the T1-T2 or T5-T6 region did not significantly alter MAP or HR compared to baseline (no SCS). However, during transcient stress (elevated sympathetic tone) induced by CPT, there was a significant increase in MAP and moderate decrease in HR during SCS at T5-T6 region, which is not consistent with previous data in the literature. Acute SCS did not result in adverse cardiovascular responses and proved to be safe. Key words: Spinal cord stimulation, mean arterial pressure, heart rate, cold pressor test

scholarly journals Effect of twelve week training program in blood pressure and heart rate at rest in older hypertensive and normotensive women

2017 ◽  
Vol 1 (1) ◽  
pp. 51
Author(s):  
Teuta Osmani Vllasolli
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Training Program ◽  
Older Women ◽  
Experimental Period ◽  
Dynamic Resistance ◽  
Arterial Blood ◽  
Resistance Exercises

Introduction: Epidemiological studies suggest that non-pharmacological       interventions such as exercise may be beneficial for treatment of hypertension.  However the potential benefits of exercises especially resistance training on arterial blood pressure and resting heart rate in older adults without hypertension remain controversial. Objective: To analyze the effect of twelve weeks of training program on systolic blood pressure (SBP) diastolic blood pressure (DBP) mean arterial    pressure (MAP) and heart rate (HR) in older women with and without hypertension. Methods: Seventeen hypertensive women (HW) and 10 normotensive women (NW) were included in training program selected by pre-exercise evaluation of the     cardiovascular status and other risks factors (smoking dislipidemia and diabetes). Training program three times per week was consisted from10 minutes of stretching exercises; 45 minutes of aerobic endurance (gait) and 10 min with five minutes of   relaxation while two times per week were included dynamic resistance exercises  (involving the major muscle groups) The training sessions of resistance exercises were performed in three sets of 8 to 10 repetition of maximum (RM) with rest    interval between sets and exercises of 90 seconds. These days aerobic exercises last only 30minutes.Hemodynamic parameters at rest were evaluated by auscultatory method (mercury sphygmomanometer) and HR by Pulsioxymeter monitor (Polar) before and after twelve weeks of experimental period. Results: The HW group (age 66.8 آ± 5.4 years) and the NW (65.2 آ± 4.8years). In HW was found a reduction of SBP (-10.6mmHgp <0.01) and DBP (-1.94 p=0.043). Although significant reduction were observed in SBP (- 6.7mmHg p<0.05) of NW group there were no significant reduce in DBP after exercises (p=0.0 32). Mean arterial pressure (MAP) and resting HR also didn’t show important changes. Conclusion: Twelve weeks training program consisted of aerobic exercises and dynamic resistance exercises is shown to be an   effective training in reduction of resting SBP in older women with hypertension and also to promote adaptations in the cardiovascular system of normotensive older women without. Keywords: older women blood pressure hypertension normotension heart rate exercise.

Interaction of vasopressin and opioids during rapid hemorrhage in conscious rabbits

1991 ◽  
Vol 260 (2) ◽  
pp. R373-R381 ◽  
Author(s):  
J. C. Schadt ◽  
E. M. Hasser
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Pressor Response ◽  
Endogenous Opioids ◽  
Adrenergic Blockade ◽  
Arterial Blood ◽  
Conscious Rabbits

We investigated possible interactions between arginine vasopressin (AVP) and endogenous opioid peptides during rapid hypotensive hemorrhage and subsequent opioid receptor blockade in conscious rabbits. Plasma AVP concentration did not change after normotensive hemorrhage but increased after hypotensive hemorrhage. Blockade of V1-AVP receptors (AVPX) did not affect prehemorrhage arterial pressure, heart rate, or hindquarter blood flow and vascular resistance. AVPX did not alter the hemodynamic response to hemorrhage or the blood loss required to reduce mean arterial pressure to less than 40 mmHg. However, hindquarter blood flow was higher and mean arterial pressure and hindquarter resistance lower after hypotensive hemorrhage in AVPX-treated animals. These differences were maintained after naloxone or saline injection. Naloxone increased mean arterial pressure and hindquarter resistance and decreased heart rate with or without AVPX. At 2 min postinjection, plasma AVP values were greater after saline than after naloxone. When naloxone's pressor response was reduced by alpha-adrenergic blockade, plasma AVP values were higher after naloxone than after saline. Thus AVP was not vital to maintenance of blood pressure during rapid normotensive hemorrhage or to the abrupt decrease in arterial blood pressure and resistance after rapid hypotensive hemorrhage. AVP release was important to spontaneous recovery from acute hypotensive hemorrhage but only of minor importance to naloxone's pressor response. Finally, AVP release appeared to be inhibited by endogenous opioids during acute hemorrhagic hypotension.

Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats

1983 ◽  
Vol 55 (1) ◽  
pp. 105-112 ◽  
Author(s):  
M. P. Kaufman ◽  
J. C. Longhurst ◽  
K. J. Rybicki ◽  
J. H. Wallach ◽  
J. H. Mitchell
Keyword(s):  
Gastrocnemius Muscle ◽  
Pressor Response ◽  
Muscular Contraction ◽  
Muscle Afferents ◽  
Exercise Group ◽  
Group Iv ◽  
Group Iii ◽  
Arterial Blood ◽  
Static Contraction ◽  
Stimulation Of

Static contraction of the hindlimb muscles, induced by electrical stimulation of the ventral roots, reflexly increases arterial blood pressure and heart rate. Although stimulation of groups III and IV muscle afferents is believed to cause these reflex increases, the responses of these afferents to a level of static contraction that increases arterial pressure have not yet been determined. Therefore, in barbiturate-anesthetized cats, afferent impulses arising from endings in the gastrocnemius muscle were recorded from the L7 or S1 dorsal roots, while the cut peripheral end of the L7 ventral root was stimulated. In addition, the effects of capsaicin (100-200 micrograms) and bradykinin (25 micrograms) on the activity of the groups III and IV afferents stimulated by contraction were examined. Contraction of the gastrocnemius muscle to a level equal to or greater than that needed to cause a pressor response stimulated 12 of 19 (63%) group III afferents and 13 of 19 (68%) group IV afferents. However, the discharge patterns of the group III afferents stimulated by contraction were very different from those of the group IV fibers. No relationship was found between those fibers stimulated by contraction and those stimulated by chemicals. Our results suggest that although both groups III and IV muscle afferents contribute to the reflex cardiovascular increases evoked by static exercise, group III fibers were likely to be stimulated by the mechanical effects of muscular contraction, whereas at least some group IV fibers were likely to be stimulated by the metabolic products of muscular contraction.

Blood Pressure Variability in Man: Its Relation to High Blood Pressure, Age and Baroreflex Sensitivity

1980 ◽  
Vol 59 (s6) ◽  
pp. 401s-404s ◽  
Author(s):  
G. Mancia ◽  
A. Ferrari ◽  
L. Gregorini ◽  
G. Parati ◽  
G. Pomidossi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Standard Deviation ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Blood Pressure Variability ◽  
Baroreflex Sensitivity ◽  
Variation Coefficient ◽  
Arterial Blood ◽  
Normotensive Subjects

1. Intra-arterial blood pressure and heart rate were recorded for 24 h in ambulant hospitalized patients of variable age who had normal blood pressure or essential hypertension. Mean 24 h values, standard deviations and variation coefficient were obtained as the averages of values separately analysed for 48 consecutive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for heart rate were smaller. 3. In hypertensive subjects standard deviation for mean arterial pressure was greater than in normotensive subjects of similar ages, but this was not the case for variation coefficient, which was slightly smaller in the former than in the latter group. Normotensive and hypertensive subjects showed no difference in standard deviation and variation coefficient for heart rate. 4. In both normotensive and hypertensive subjects standard deviation and even more so variation coefficient were slightly or not related to arterial baroreflex sensitivity as measured by various methods (phenylephrine, neck suction etc.). 5. It is concluded that blood pressure variability increases and heart rate variability decreases with age, but that changes in variability are not so obvious in hypertension. Also, differences in variability among subjects are only marginally explained by differences in baroreflex function.

scholarly journals Plasticity in breathing and arterial blood pressure following acute intermittent hypercapnic hypoxia in infant rat pups with a partial loss of 5-HT neurons

2015 ◽  
Vol 309 (10) ◽  
pp. R1273-R1284 ◽  
Author(s):  
Jennifer Magnusson ◽  
Kevin J. Cummings
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Cardiovascular Responses ◽  
Partial Loss ◽  
Rat Pups ◽  
Arterial Blood ◽  
Hypercapnic Hypoxia ◽  
Long Term Facilitation

The role of serotonin (5-HT) neurons in cardiovascular responses to acute intermittent hypoxia (AIH) has not been studied in the neonatal period. We hypothesized that a partial loss of 5-HT neurons would reduce arterial blood pressure (BP) at rest, increase the fall in BP during hypoxia, and reduce the long-term facilitation of breathing (vLTF) and BP following AIH. We exposed 2-wk-old, 5,7-dihydroxytryptamine-treated and controls to AIH (10% O2; n = 13 control, 14 treated), acute intermittent hypercapnia (5% CO2; n = 12 and 11), or acute intermittent hypercapnic hypoxia (AIHH; 10% O2, 5% CO2; n = 15 and 17). We gave five 5-min challenges of AIH and acute intermittent hypercapnia, and twenty ∼20-s challenges of AIHH to mimic sleep apnea. Systolic BP (sBP), diastolic BP, mean arterial pressure, heart rate (HR), ventilation (V̇e), and metabolic rate (V̇o2) were continuously monitored. 5,7-Dihydroxytryptamine induced an ∼35% loss of 5-HT neurons from the medullary raphe. Compared with controls, pups deficient in 5-HT neurons had reduced resting sBP (∼6 mmHg), mean arterial pressure (∼5 mmHg), and HR (56 beats/min), and experienced a reduced drop in BP during hypoxia. AIHH induced vLTF in both groups, reflected in increased V̇e and V̇e/V̇o2, and decreased arterial Pco2. The sBP of pups deficient in 5-HT neurons, but not controls, was increased 1 h following AIHH. Our data suggest that a relatively small loss of 5-HT neurons compromises resting BP and HR, but has no influence on ventilatory plasticity induced by AIHH. AIHH may be useful for reversing cardiorespiratory defects related to partial 5-HT system dysfunction.

Hypotensive and Regional Haemodynamic Effects of Exercise, Fasted and after Food, in Human Sympathetic Denervation

1998 ◽  
Vol 94 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Sharmini Puvi-Rajasingham ◽  
Gareth D. P. Smith ◽  
Adeola Akinola ◽  
Christopher J. Mathias
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Superior Mesenteric Artery ◽  
Vascular Resistance ◽  
Mesenteric Artery ◽  
Autonomic Failure ◽  
Sympathetic Denervation ◽  
Stroke Distance

1. In human sympathetic denervation due to primary autonomic failure, food and exercise in combination may produce a cumulative blood pressure lowering effect due to simultaneous splanchnic and skeletal muscle dilatation unopposed by corrective cardiovascular reflexes. We studied 12 patients with autonomic failure during and after 9 min of supine exercise, when fasted and after a liquid meal. Standing blood pressure was also measured before and after exercise. 2. When fasted, blood pressure fell during exercise from 162 ± 7/92 ± 4 to 129 ± 9/70 ± 5 mmHg (mean arterial pressure by 22 ± 5%), P < 0.0005. After the meal, blood pressure fell from 159 ± 8/88 ± 6 to 129 ± 6/70 ± 4 mmHg (mean arterial pressure by 22 ± 3%), P < 0.0001, and further during exercise to 123 ± 6/61 ± 3 mmHg (mean arterial pressure by 9 ± 3%), P < 0.01. The stroke distance—heart rate product, an index of cardiac output, did not change after the meal. During exercise, changes in the stroke distance—heart rate product were greater when fasted. 3. Resting forearm and calf vascular resistance were higher when fasted. Calf vascular resistance fell further after exercise when fasted. Resting superior mesenteric artery vascular resistance was lower when fed; 0.19 ± 0.02 compared with 032 ± 0.06, P < 0.05. After exercise, superior mesenteric artery vascular resistance had risen by 82%, to 0.53 ± 0.12, P < 0.05 (fasted) and by 47%, to 0.29 ± 0.05, P < 0.05 (fed). 4. On standing, absolute levels of blood pressure were higher when fasted [83 ± 7/52 ± 7 compared with 71 ± 2/41 ± 3 (fed), each P < 0.05]. Subjects were more symptomatic on standing post-exercise when fed. 5. In human sympathetic denervation, exercise in the fed state lowered blood pressure further than when fasted and worsened symptoms of postural hypotension.

Increased vascular resistance in paralyzed legs after spinal cord injury is reversible by training

2002 ◽  
Vol 93 (6) ◽  
pp. 1966-1972 ◽  
Author(s):  
Maria T. E. Hopman ◽  
Jan T. Groothuis ◽  
Marcel Flendrie ◽  
Karin H. L. Gerrits ◽  
Sibrand Houtman
Keyword(s):  
Blood Pressure ◽  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Arterial Blood Flow ◽  
Arterial Blood ◽  
Cord Injury

The purpose of the present study was to determine the effect of a spinal cord injury (SCI) on resting vascular resistance in paralyzed legs in humans. To accomplish this goal, we measured blood pressure and resting flow above and below the lesion (by using venous occlusion plethysmography) in 11 patients with SCI and in 10 healthy controls (C). Relative vascular resistance was calculated as mean arterial pressure in millimeters of mercury divided by the arterial blood flow in milliliters per minute per 100 milliliters of tissue. Arterial blood flow in the sympathetically deprived and paralyzed legs of SCI was significantly lower than leg blood flow in C. Because mean arterial pressure showed no differences between both groups, leg vascular resistance in SCI was significantly higher than in C. Within the SCI group, arterial blood flow was significantly higher and vascular resistance significantly lower in the arms than in the legs. To distinguish between the effect of loss of central neural control vs. deconditioning, a group of nine SCI patients was trained for 6 wk and showed a 30% increase in leg blood flow with unchanged blood pressure levels, indicating a marked reduction in vascular resistance. In conclusion, vascular resistance is increased in the paralyzed legs of individuals with SCI and is reversible by training.

scholarly journals EFFECT OF ORAL MOXONIDINE IN THE ATTENUATION OF THE HAEMODYNAMIC RESPONSES SEEN DURING LAPAROSCOPIC SURGERIES

2017 ◽  
Vol 10 (3) ◽  
pp. 409
Author(s):  
Sidharth Sraban Routray ◽  
Ramakanta Mohanty
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Placebo Group ◽  
Stress Response ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Significant Rise ◽  
Hemodynamic Stability ◽  
Blinded Study ◽  
Double Blinded

ABSTRACTObjective: During laparoscopic surgeries, pneumoperitoneum can lead to various pathophysiologic changes in the cardiovascular system resulting inhypertension and tachycardia. Search for ideal drug to prevent this hemodynamic response goes on. The aim of our study was to evaluate the effect oforally administered moxonidine in attenuating the hemodynamic responses that occur during the laparoscopic surgeries.Methods: A total of 50 adult acetylsalicylic acid I and II patients scheduled for elective laparoscopic surgeries were selected for this prospectiverandomized double-blinded study. They were randomly allocated into two groups: moxonidine group (M) and placebo group (P). M group receivedoral moxonidine 0.3 mg at 8 pm on the day before surgery and at 8 am on the day of surgery. P group received a placebo at the same timing as that ofthe M group.Results: Following pneumoperitoneum rise in systolic blood pressure (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and heart rate (HR)was higher in P group in comparison to M group which was statistically significant.Conclusion: Significant rise in HR, SBP, DBP, and mean BP was noted in the P group in comparison to moxonidine group. Moxonidine provided betterperioperative hemodynamic stability in patients undergoing laparoscopic surgeries.Keywords: Moxonidine, Stress response, Laparoscopic.

Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise

2001 ◽  
Vol 91 (5) ◽  
pp. 2351-2358 ◽  
Author(s):  
K. M. Gallagher ◽  
P. J. Fadel ◽  
S. A. Smith ◽  
K. H. Norton ◽  
R. G. Querry ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Dynamic Exercise ◽  
Positive Pressure ◽  
Intramuscular Pressure ◽  
Arterial Blood ◽  
Exercise In Humans ◽  
Cuff Occlusion

This investigation was designed to determine the role of intramuscular pressure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixteen subjects performed incremental (20 W/min) cycle exercise to fatigue under four conditions: control, exercise with thigh cuff occlusion of 90 Torr (Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 Torr, and a combination of thigh cuff occlusion and LBPP (combination). Indexes of central command (heart rate, oxygen uptake, ratings of perceived exertion, and electromyographic activity), cardiac output, stroke volume, and total peripheral resistance were not significantly different between the four conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arterial pressure from control at rest and throughout the incremental exercise protocol ( P < 0.05). Conversely, there existed no significant changes in mean arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is tonically active and is the primary mediator of exercise pressor reflex-induced alterations in arterial blood pressure during submaximal dynamic exercise in humans.

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