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71.
A search for vasomotor depressor sites in the lateral medullary brainstem of anesthetized cat using microinjections of AMPA has delineated a longitudinal column of sympathoinhibitory neurons consisting of the rostral depressor area, the caudal ventrolateral medulla, and a new intermediate depressor area. Systematic blockade of these three subregions with bilateral microinjections of kynurenic acid indicates a uniform involvement of the entire column with sympathetic baroreflex, but a slightly greater involvement of the anterior portion, over the posterior, with regulation of cardiovascular tone. 相似文献
72.
Previous experiments have demonstrated that stimulation of muscarinic cholinergi receptors in the nucleus tractus solitarius (NTS) of the rat decreases arterial blood pressure and heart rate. The present studies were designed to examine the role of cholinergic mechanisms in the NTS in the tonic regulation of arterial pressure and the baroreceptor reflex. Atropine injected into the NTS of chloralose-anesthetized rats produced a dose-dependent inhibition of cardiovascular responses elicited by injection of acetylcholine into the same site; 240 pmol atropine eliminated acetylcholine-evoked responses. Atropine also increased arterial blood pressure but only at higher doses. Even larger doses of atropine were required to alter cardiovascular responses elicited by electrical stimulation of the aortic depressor nerve. Methylatropine injected into the NTS also blocked acetylcholine-evoked responses but, in contrast to the actions of atropine, did not increase arterial pressure in the dose range required to block acetylcholine-evoked responses. Furthermore, a dose of methylatropine (1 nmol) capable of blocking acetylcholine-evoked cardiovascular responses did not alter aortic depressor nerve-evoked cardiovascular responses. This lack of an effect of methylatropine on arterial pressure and aortic depressor nerve-evoked responses was not due to limited diffusion of the drug within the NTS since 1 nmol methylatropine completely blocked acetylcholine-evoked responses even when injected 0.5 mm distant from the site of acetylcholine injection. These results suggest that cholinergic mechanisms in the NTS are not involved in the tonic regulation of cardiovascular function or the baroreceptor reflex. Furthermore, these results highlight the importance of characterizing doses of drugs used in microinjection studies. 相似文献
73.
The effects of nicardipine injection on baroreflex control of heart rate were investigated by both pressor and depressor tests in 17 adult patients. Baroreflex sensitivity was attenuated after nicardipine injection by the pressor test using phenylephrine, whereas it was not changed by the depressor test using nitroglycerine. No resetting of the baroreflex occurred after nicardipine injection. By the pressor test, the plasma norepinephrine level was decreased, indicating that parasympathetic activity increased, and by the depressor test, the plasma norepinephrine concentration was increased, indicating that sympathetic activity increased. These results suggest that it is safe to use nicardipine clinically even when reduction in blood pressure for hypovolemia or unclamping the main artery is expected, and it is disadvantageous to administer the drug when an increase in blood pressure due to cross-clamping of the main artery is forecasted.(Wajima Z, Inoue T, Ogawa R: The effects of an intravenous nicardipine injection on baroreflex control of heart rate in man. J Anesth 7: 40–47, 1993) 相似文献
74.
Nicolas Bourdillon Sasan Yazdani Masih Nilchian Alessio Mariano Jean-Marc Vesin Grégoire P. Millet 《Journal of Science and Medicine in Sport》2018,21(9):941-949
Objectives
Heart rate variability (HRV) is commonly used to diagnose overreaching and monitor athletes’ responses to training. Baroreflex sensitivity (BRS) is modified by changes in training load and might be another means to detect overreaching. The goal of this study was to assess BRS and HRV changes in two groups of athletes responding either negatively (FOR) or positively (AF) to similar training overload.Design
Fifteen athletes performed 2-week baseline (BSL) training followed by 3-week overload (+45%; OVL) and 2-week recovery (?20%; RCV).Methods
HRV, training load and subjective fatigue were measured daily via questionnaires. BRS, salivary cortisol and testosterone, and submaximal exercise and maximal 3-km run performances were measured at the end of each period.Results
Based on their performance change during OVL, 8 athletes were diagnosed as FOR and 7 as AF. Subjective fatigue was increased in FOR athletes during OVL. BRS increased in AF but not in FOR athletes during RCV. At the end of RCV, cortisol and testosterone were higher than BSL in both groups.Conclusions
Three weeks of similar training overload can induce either performance enhancement or overreaching. The changes in submaximal exercise and maximal performances and in subjective fatigue were the fastest-responding parameters that distinguished the two groups of athletes during OVL. Training overload blunted the increase in BRS in FOR only. Most of the differences in BRS were observed during the recovery period. BRS appears to be a more sensitive parameter than HRV for early monitoring of responses to training. 相似文献75.
J. Derek Kingsley Lynn B. Panton Victor McMillan Arturo Figueroa 《Archives of physical medicine and rehabilitation》2009,90(9):1628-1634
Kingsley JD, Panton LB, McMillan V, Figueroa A. Cardiovascular autonomic modulation after acute resistance exercise in women with fibromyalgia.
Objective
To test the hypothesis that autonomic modulation after resistance exercise (RE) would be reduced in women with fibromyalgia (FM) compared with controls.Design
Before-after trial.Setting
Testing occurred in a university setting.Participants
Women with FM (n=9) and healthy controls (n=9) underwent testing before (pre) and 20 minutes after (post) RE.Interventions
Not applicable.Main Outcome Measures
Normalized low-frequency (LFnu) and normalized high-frequency (HFnu) oscillations and the LFnu/HFnu ratio were indicative of sympathetic modulation, parasympathetic modulation, and sympathovagal balance, respectively. Baroreceptor reflex sensitivity (BRS) was also measured.Results
Variables were similar in both groups at rest. HFnu decreased in controls (pre, 55.0±4.2%; post, 35.0±4.7%; P<.05) and increased in women with FM (pre, 57.0±5.7%; post, 63.2±4.6%; P<.05). LFnu increased in controls (pre, 43.3±4.4%; post, 63.2±4.8%; P<.05) and decreased in women with FM (pre, 41.8±5.6%; post, 35.6±4.7%; P<.05). The LFnu/HFnu ratio increased in controls (pre, 0.89±0.17; post, 2.43±0.64; P<.05) with no change in women with FM (pre, 0.90±0.22; post, 0.64±0.13; P=.13). BRS decreased in controls (pre, 8.78±1.42ms/mmHg; post, 5.49±0.66ms/mmHg; P<.05), but not in women with FM (pre, 5.91±1.22ms/mmHg; post, 9.23±2.4ms/mmHg; P=.16).Conclusions
After acute RE, women with FM responded differently from controls, demonstrated by lower sympathetic and higher vagal modulation without altering BRS. These postexercise responses may be attributed to the altered autonomic responsiveness to physiologic stress that characterizes FM. 相似文献76.
de Andrade O Amarante MK da Cunha NV de Aguiar Corrêa FM Fontes MA Martins-Pinge MC 《Neuroscience research》2012,72(3):270-274
We evaluated the involvement of paraventricular nucleus (PVN) in the changes in mean arterial pressure (MAP) and heart rate (HR) during an orthostatic challenge (head up tilt, HUT). Adult male Wistar rats, instrumented with guide cannulas to PVN and artery and vein catheters were submitted to MAP and HR recording in conscious state and induction of HUT. The HUT induced an increase in MAP and HR and the pretreatment with prazosin and atenolol blocked these effects. After inhibition of neurotransmission with cobalt chloride (1 mM/100 nl) into the PVN the HR parameters did not change, however we observed a decrease in MAP during HUT. Our data suggest the involvement of PVN in the brain circuitry involved in cardiovascular adjustment during orthostatic challenges. 相似文献
77.
M.T. Durand A.L. Mota A.R. Barale J.A. Castania R. Fazan Jr. H.C. Salgado 《Brazilian journal of medical and biological research》2012,45(5):444-449
The time to reach the maximum response of arterial pressure, heart rate and vascular resistance (hindquarter and mesenteric) was measured in conscious male spontaneously hypertensive (SHR) and normotensive control rats (NCR; Wistar; 18-22 weeks) subjected to electrical stimulation of the aortic depressor nerve (ADN). The parameters of stimulation were 1 mA intensity and 2 ms pulse length applied for 5 s, using frequencies of 10, 30, and 90 Hz. The time to reach the hemodynamic responses at different frequencies of ADN stimulation was similar for SHR (N = 15) and NCR (N = 14); hypotension = NCR (4194 ± 336 to 3695 ± 463 ms) vs SHR (3475 ± 354 to 4494 ± 300 ms); bradycardia = NCR (1618 ± 152 to 1358 ± 185 ms) vs SHR (1911 ± 323 to 1852 ± 431 ms), and the fall in hindquarter vascular resistance = NCR (6054 ± 486 to 6550 ± 847 ms) vs SHR (4849 ± 918 to 4926 ± 646 ms); mesenteric = NCR (5574 ± 790 to 5752 ± 539 ms) vs SHR (5638 ± 648 to 6777 ± 624 ms). In addition, ADN stimulation produced baroreflex responses characterized by a faster cardiac effect followed by a vascular effect, which together contributed to the decrease in arterial pressure. Therefore, the results indicate that there is no alteration in the conduction of the electrical impulse after the site of baroreceptor mechanical transduction in the baroreflex pathway (central and/or efferent) in conscious SHR compared to NCR. 相似文献
78.
Andrea Dietrich Harriëtte Riese Arie M. van Roon Albertine J. Oldehinkel Jan Neeleman 《Biological psychology》2009,81(1):67-73
We investigated the temperamental traits high-intensity pleasure (temperamental activation) and shyness (temperamental inhibition) in relation to autonomic function as measured by heart rate (HR), respiratory sinus arrhythmia (RSA), and baroreflex sensitivity (BRS) in 938 10-13-year-old preadolescents from a population cohort. Temperament was evaluated by parent reports on the Revised Early Adolescent Temperament Questionnaire. Autonomic measurements were obtained in supine and standing position. High-intensity pleasure was negatively associated with supine HR and positively with supine RSA and BRS in both genders. Shyness was positively related to supine BRS in girls only. Orthostatic-based autonomic reactivity (difference) scores adjusted for supine values were unrelated to temperamental measures. It appeared that higher scores on temperamental activation and inhibition are associated with higher cardiac vagal activity (RSA) and/or flexible regulation of autonomic balance (BRS), implicating healthy physiological functioning. Moreover, results suggest a physiological basis promoting the tendency towards engagement in high-intensity activities. 相似文献
79.
Stefan Duschek Heike Heiss Boriana Buechner Natalie Werner Rainer Schandry Gustavo A. Reyes del Paso 《The journal of physiological sciences : JPS》2009,59(2):105-112
Chronic low blood pressure is typically accompanied by symptoms such as fatigue, reduced drive, dizziness, headaches and cold
limbs. Reduced cognitive performance, diminished cerebral blood flow and autonomic dysregulation have been furthermore documented
in this condition. The present contribution reports two studies exploring systemic hemodynamics in chronic hypotension and
their modification through vasopressor application. In study I, effects of the alpha-sympathomimetic midodrine were examined
in 54 hypotensive individuals using a placebo-controlled double-blind design. Hemodynamic parameters were assessed at rest
and during mental stress. They were derived from continuous blood pressure recordings using Modelflow analysis. The drug led
to marked increases in blood pressure, total peripheral resistance and stroke volume. However, due to strong heart rate deceleration,
cardiac output remained virtually unchanged. In study II, 40 hypotensive and 40 normotensive control persons were compared
with respect to hemodynamics. While groups did not differ in total peripheral resistance, hypotensives exhibited markedly
diminished stroke volume and heart rate, resulting in a reduction in cardiac output of 25% at rest and of 33% during mental
stress. The data provide relevant knowledge about the hemodynamic mediation of chronic hypotension. In contrast to elevated
blood pressure, which is mainly determined by increased peripheral resistance, reduced cardiac output may be the cardinal
hemodynamic aberration in chronic hypotension. Midodrine proved to be effective in elevating blood pressure. However, given
the cardiac origin of chronic hypotension and the lack of drug effect on cardiac output, alpha-sympathomimetic treatment may
be suboptimal. 相似文献
80.
Gert Pfurtscheller Rupert Ortner Günther Bauernfeind Patricia Linortner Christa Neuper 《Neuroscience letters》2010
Slow oscillations around 0.1 Hz are characteristic features of both the cardiovascular and central nervous systems. Such oscillation have been reported, e.g. in blood pressure, heart rate, EEG and brain oxygenation. Hence, conscious intention of a motor act may occur only as a result of brain activity changes in frontal and related brain areas, or might be entrained by slow oscillations in the blood pressure. Twenty-six subjects were asked to perform voluntary, self-paced (at free will) brisk finger movements. Some subjects performed self-paced movements in relatively periodic intervals of around 10 s at the decreasing slope of the slow 0.1-Hz blood pressure oscillation. Our study reveals the first time that self-paced movements, at least in some subjects, do not stem from “free will” based on brain activity alone, but are influenced by slow blood pressure oscillations. 相似文献