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Biophysical Journal Sep 1972A mathematical model that describes the relationship between sinus pressure and nerve discharge frequency of the carotid sinus baroreceptor is presented. It is partly...
A mathematical model that describes the relationship between sinus pressure and nerve discharge frequency of the carotid sinus baroreceptor is presented. It is partly based upon the single-fiber data obtained by Clarke from the sinus nerve of a dog. The model takes into account what is currently known about the physiology of the baroreceptor. It consists of two nonlinear ordinary differential equations and eight free parameters. With one set of values for these eight parameters, the model reproduces well the experimental results reported by Clarke for positive ramp pressure inputs. Only three parameters needed to be adjusted in order to fit the dynamic data. The remaining five were obtained from static and steady-state data.
Topics: Carotid Sinus; Kinetics; Mathematics; Models, Neurological; Nerve Endings; Neurons; Pressoreceptors
PubMed: 5056961
DOI: 10.1016/S0006-3495(72)86153-8 -
British Journal of Anaesthesia May 1995
Topics: Heart; Heart Rate; Humans; Posture; Pressoreceptors; Vagus Nerve
PubMed: 7772448
DOI: 10.1093/bja/74.5.628-d -
Clinical and Experimental Pharmacology... Mar 20101. Baroreceptors regulate moment-to-moment blood pressure (BP) variations, but their long-term effect on the cardiovascular system remains unclear. Baroreceptor deficit... (Comparative Study)
Comparative Study
1. Baroreceptors regulate moment-to-moment blood pressure (BP) variations, but their long-term effect on the cardiovascular system remains unclear. Baroreceptor deficit accompanying hypertension contributes to increased BP variability (BPV) and sympathetic activity, whereas exercise training has been associated with an improvement in these baroreflex-mediated changes. The aim of the present study was to evaluate the autonomic, haemodynamic and cardiac morphofunctional effects of long-term sinoaortic baroreceptor denervation (SAD) in trained and sedentary spontaneously hypertensive rats (SHR). 2. Rats were subjected to SAD or sham surgery and were then further divided into sedentary and trained groups. Exercise training was performed on a treadmill (five times per week, 50-70% maximal running speed). All groups were studied after 10 weeks. 3. Sinoaortic baroreceptor denervation in SHR had no effect on basal heart rate (HR) or BP, but did augment BPV, impairing the cardiac function associated with increased cardiac hypertrophy and collagen deposition. Exercise training reduced BP and HR, re-established baroreflex sensitivity and improved both HR variability and BPV. However, SAD in trained SHR blunted all these improvements. Moreover, the systolic and diastolic hypertensive dysfunction, reduced left ventricular chamber diameter and increased cardiac collagen deposition seen in SHR were improved after the training protocol. These benefits were attenuated in trained SAD SHR. 4. In conclusion, the present study has demonstrated that the arterial baroreflex mediates cardiac disturbances associated with hypertension and is crucial for the beneficial cardiovascular morphofunctional and autonomic adaptations induced by chronic exercise in hypertension.
Topics: Adaptation, Physiological; Animals; Autonomic Denervation; Baroreflex; Heart Rate; Hypertension; Male; Myocardial Contraction; Physical Conditioning, Animal; Pressoreceptors; Rats; Rats, Inbred SHR
PubMed: 19930428
DOI: 10.1111/j.1440-1681.2009.05333.x -
Pharmacological Research Jul 2000The baroreflex-induced changes in heart rate in chloralose anaesthetized and artificially ventilated cats (2.5-4.0 kg) before and after pretreatment with calcium channel...
The baroreflex-induced changes in heart rate in chloralose anaesthetized and artificially ventilated cats (2.5-4.0 kg) before and after pretreatment with calcium channel blockers (CCBs) were compared. Baroreflex mediated changes in heart rate (HR) were elicited by raising and lowering the systemic blood pressure with intravenous injections of phenylephrine and sodium nitroprusside, respectively. The effects of three CCBs, verapamil, diltiazem and nifedipine administered either intravenously (i.v.) or intracisternally (i.c.) were studied. Verapamil administration markedly inhibited the reflex bradycardia as well as the tachycardia following either i.v. or i.c. administration. Intracisternally, a relatively smaller dose of verapamil produced an effect comparable in magnitude and duration, to a higher i.v. dose. The reflex bradycardia was inhibited following i.v., but not i.c. administration of nifedipine while the reflex tachycardia was not affected significantly by either i.v. or i.c. nifedipine. Intravenous diltiazem did not appear to affect the reflex bradycardia or tachycardia significantly. It is suggested that verapamil administration interacts with central cardiovascular integrating mechanisms to reduce the gain of the baroreflex function. Nifedipine and diltiazem are relatively free from this effect.
Topics: Animals; Blood Pressure; Calcium Channel Blockers; Cats; Female; Heart Rate; Male; Nitroprusside; Phenylephrine; Pressoreceptors; Reflex
PubMed: 10860642
DOI: 10.1006/phrs.2000.0659 -
Hypertension (Dallas, Tex. : 1979) May 1995Bromocriptine, a dopamine agonist with central nervous system actions, may reduce sympathetic nervous system activity. We tested this hypothesis by measuring arterial... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
Bromocriptine, a dopamine agonist with central nervous system actions, may reduce sympathetic nervous system activity. We tested this hypothesis by measuring arterial blood pressure, central venous pressure, heart rate, muscle sympathetic nerve activity, and forearm blood flow before and after unloading the arterial baroreceptors with sodium nitroprusside (0.5 to 1.5 mcg/kg per minute IV), before and after unloading the cardiopulmonary baroreceptors with incremental lower body negative pressure (0 to -15 mm Hg), and before and after immersion of the hand in ice-cold water for 2 minutes (cold pressor test). After obtaining basal responses to provocative maneuvers, we gave 20 healthy subjects either 5 mg oral bromocriptine (n = 10) or placebo (n = 10) in a randomized, double-blind fashion. Bromocriptine did not affect resting mean arterial pressure, heart rate, or forearm blood flow. Bromocriptine decreased resting central venous pressure by 1.2 mm Hg (P < .05) and tended to increase total integrated muscle sympathetic nerve activity (from 151 +/- 44 to 212 +/- 82 U/min, P = NS). The reflex increases in muscle sympathetic nerve activity to nitroprusside infusion and lower body negative pressure were unchanged by bromocriptine; however, vascular responsiveness to both maneuvers was impaired after bromocriptine administration compared with control. Without bromocriptine, the reflex increase in muscle sympathetic nerve activity after nitroprusside-induced hypotension maintained forearm blood flow at a constant level, whereas with bromocriptine the forearm blood flow increased from 1.9 +/- 0.3 to 2.8 +/- 0.6 mL/min per 100 mL (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Adult; Bromocriptine; Cold Temperature; Double-Blind Method; Hemodynamics; Humans; Lung; Male; Muscles; Pressoreceptors; Sympathetic Nervous System
PubMed: 7737719
DOI: 10.1161/01.hyp.25.5.1075 -
Hypertension (Dallas, Tex. : 1979) May 1995We compared two methods of assessment of baroreflex sensitivity in eight supine healthy volunteers during repeated baseline measurements and various conditions of... (Comparative Study)
Comparative Study
We compared two methods of assessment of baroreflex sensitivity in eight supine healthy volunteers during repeated baseline measurements and various conditions of cardiac autonomic blockade. The spontaneous baroreflex method involved computer scanning of recordings of continuous finger arterial pressure and electrocardiogram to locate sequences of three or more beats in which pressure spontaneously increased or decreased, with parallel changes in pulse intervals. The mean regression slope of all these sequences during each study condition was considered to represent the mean spontaneous baroreflex slope. In the drug-induced method, sigmoidal curves were constructed from data obtained by bolus injections of phenylephrine and nitroprusside; the tangents taken at the resting pressure of each of these curves were compared with the mean spontaneous baroreflex slopes. The two methods yielded slopes that were highly correlated (r = .96, P < .001), with significant but similar intraindividual baseline variability. Atropine virtually eliminated the baroreflex slope; subsequent addition of propranolol did not alter it further. Propranolol or clonidine alone increased average baroreflex slope to the extent that they increased resting pulse interval (r = .69 to .83). The spontaneous baroreflex method provides a reliable, noninvasive assessment of human vagal cardiac baroreflex sensitivity within its physiological operating range.
Topics: Adult; Blood Pressure; Clonidine; Humans; Male; Middle Aged; Phenylephrine; Pressoreceptors; Propranolol; Reflex; Regression Analysis
PubMed: 7737717
DOI: 10.1161/01.hyp.25.5.1058 -
The Journal of Surgical Research Jul 1978
Review
Topics: Angina Pectoris; Carotid Sinus; Electric Stimulation; Electric Stimulation Therapy; Humans; Hypertension; Pressoreceptors
PubMed: 355726
DOI: 10.1016/0022-4804(78)90162-2 -
Annals of the New York Academy of... Apr 1969
Topics: Models, Neurological; Pressoreceptors; Time; Transducers
PubMed: 5258023
DOI: 10.1111/j.1749-6632.1969.tb14021.x -
Nordisk Medicin Jan 1968
Topics: Animals; Blood Pressure; Dogs; Electric Stimulation; Humans; Hypertension; Pressoreceptors
PubMed: 5637267
DOI: No ID Found -
Anaesthesia Jul 1980
Topics: Anesthesia; Carotid Body Tumor; Humans; Pressoreceptors
PubMed: 7435944
DOI: 10.1111/j.1365-2044.1980.tb03893.x