共查询到20条相似文献,搜索用时 15 毫秒
1.
Pulmonary hemodynamics and net transcapillary fluid flux (NTFF) were measured in conscious toads before and following bilateral denervation of the recurrent laryngeal nerves (rLN), which contain afferents from baroreceptors located in the pulmocutaneous arteries. Denervation caused an acute doubling of the arterial-venous pressure gradient across the lung and a threefold increase in pulmonary blood flow. Calculated pulmonary vascular resistance fell and remained below control values through the period of experimentation. NTFF increased by an order of magnitude (0.74-7.77 ml X kg-1 X min-1), as filtration increased in response to the hemodynamic changes caused by rLN denervation. There was a better correlation between NTFF and pulmonary blood flow than between NTFF and pulmonary driving pressure. Our results support the view that tonic neural input from pulmocutaneous baroreceptors protects the anuran lung from edema by restraining pulmonary driving pressure and blood flow and perhaps by reflexly maintaining vascular tone in the extrinsic pulmonary artery, therefore tending to increase the pre-to-postpulmonary capillary resistance ratio and biasing the Starling relationship in the pulmonary capillaries against filtration. 相似文献
2.
Julia T. Apter 《Bulletin of mathematical biology》1963,25(3):325-339
Aortic diastolic pressure curves calculated on the basis of a constant peripheral resistance do not predict humps like those
found in actual clinical records. The present study considers the form of the aortic pressure curve to be expected during
diastole if blood flowed out of the aorta against a peripheral resistance (R) that changed in response to baroreceptor stimulation. Assumptions are (1) baroreceptor stimulation is provided by arterial
pressures above a threshold pressureP
*; (2) pressures aboveP
* occur during late systole and early diastole; (3) peripheral resistance starts to respond a given time interval Δ afterP reachesP
* in systole; (4) Δ is less than the duration of time betweenP
* occurring during early diastole and the end of the cardiac cycle. The present analysis predicts humps in the diastolic pressure
curve, the humps occurring at times when the peripheral resistance time course alters. Initially,R is considered constant at its maximal valueR
0, then it changes in response to pressures during systole (assumed to have a parabolic time course), then changes in response
to pressures during early diastole (assumed to have an exponential time course), and then changes in response to pressures
later in diastole. The humps so predicted occur at times consistent with the location of humps in clinical records. What is
more, this analysis predicts no humps in association with an unresponsive peripheral resistance as in essential hypertension,
in agreement with clinical findings. 相似文献
3.
S. Thomas R. Fritsche S. F. Perry 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):451-458
Simultaneous venous (pre-branchial) and arterial (post-branchial) extracorporeal blood circulations were utilized to monitor continuously the rapid and progressive effects of acute environmental hypercapnia (water partial pressure of CO2 4.8±0.2 torr) or hypoxia (water partial pressure of O2 25±2 torr) on oxygen and carbon dioxide tensions and pH in the blood of rainbow trout (Oncorhynchus mykiss). During hypercapnia, the CO2 tension in the arterial blood increased from 1.7±0.1 to 6.2±0.2 torr within 20 min and this was associated with a decrease of arterial extracellular pH from 7.95±0.03 to 7.38±0.03; the acid-base status of the mixed venous blood changed in a similar fashion. The decrease in blood pH in vivo was greater than in blood equilibrated in vitro with a similar CO2 tension indicating a significant metabolic component to the acidosis in vivo. Under normocapnic conditions, venous blood CO2 tension was slightly higher than arterial blood CO2 tension difference was abolished or reversed during the initial 25 min of hypercapnia indicating that CO2 was absorbed from the water during this period. Arterial O2 tension remained constant during hypercapnia; however, venous blood O2 tension decreased significantly (from 22.0±2.6 to 9.0±1.0 torr) during the initial 10 min. Hypercapnia elicited the release of catecholamines (adrenaline and noradrenaline) into the blood. The adrenaline concentration increased from 6±3 to 418±141 nmol · l-1 within 25 min; noradrenaline concentration increased from 3±0.5 to 50±21 nmol · l-1 within 15 min. During hypoxia arterial blood O2 tension declined progressively from 108.4±9.9 to 12.8±1.7 torr within 30 min. Venous blood O2 tension initially was stable but then decreased abruptly as catecholamines were released into the circulation. The release of catecholamines occurred concomitantly with a sudden metabolic acidosis in both blood compartments and a rise in CO2 tension in the mixed venous blood only.Abbreviations
CCO2
plasmatotal carbondioxide
-
CtO2
blood oxygen content
-
PO2
partial pressure of oxygen
-
PCO2
partial pressure of carbon dioxide
-
PaO2
arterial bloodPO2
-
PaCO2
arterial bloodPCO2
-
PvCO2
venous bloodPCO2
-
PwO2
waterPO2
-
PwCO2
waterPCO2
- Hb
haemoglobin
-
SHbO2
haemoglobin oxygen saturation
- HPLC
high-performance liquid chromatography
- rbc
red blood cell(s)
- Hct
haematocrit 相似文献
4.
Aicher SA 《Cellular and molecular neurobiology》2003,23(4-5):479-490
1. In studies conducted with Dr Donald Reis we described a functionally distinct region of the rat medullary reticular formation that we called the Gigantocellular Depressor Area (GiDA). The GiDA was defined as a region from which vasodepressor and sympathoinhibitory responses were evoked by nanoinjections of glutamate. We later showed that cells in the GiDA project to autonomic nuclei in the medulla, brainstem, and spinal cord, including the intermediolateral cell column. We also showed that kainic acid lesions of the GiDA induce hypertension and block the baroreceptor reflex evoked by electrical stimulation of the aortic depressor nerve. The present studies describe the effects of muscimol nanoinjections into the GiDA.2. Nanoinjections of muscimol were made in the GiDA of anesthetized rats and changes in arterial pressure, heart rate, and responses to aortic depressor nerve stimulation were measured.3. Bilateral nanoinjections of muscimol into the GiDA evoke an increase in arterial pressure and lead to fulminating hypertension. Unilateral injections of muscimol into the GiDA block the baroreflex response evoked by electrical stimulation of the ipsilateral aortic depressor nerve. However, these unilateral injections of muscimol into the GiDA evoked profound falls in arterial pressure to nearly spinal levels. In spite of this fall in blood pressure, heart rate also decreased significantly and there was not a compensatory tachycardia. Both the arterial pressure and baroreceptor responses required several hours to recover following the muscimol injections.4. Although these data are consistent with the proposal that the GiDA is critical for the baroreflex, the opposing effects on blood pressure of unilateral and bilateral injections of muscimol are difficult to reconcile with our current models of central sympathetic regulation. 相似文献
5.
A Niechaj G Wójcik K Lupa 《Archives internationales de physiologie et de biochimie》1978,86(2):385-391
Correlations between the resting blood pressure and magnitude of depressor responses evoked by graded stimulation of the aortic nerve, were studied in rabbits anaesthetized with urethane. The strength of stimulation ranged from 1 to 10 times the threshold, and activated the myelinated afferents. The frequency of stimulation was 5 and 50 cycles/sec. At lower frequency of stimulation the correlations become significant when the intensity of stimulation is 3 times the threshold and they increase at the highest strengths of stimulation. Correlation coefficients calculated for responses obtained at the frequency of 50 cycles/sec are significant in 8 out of 9 intensities of stimulation. With increase in the strength of stimulation they increase, attain their maximum at twice the threshold and decrease at the largest used stimulus strengths. The changes in the values of the correlation coefficients are not paralleled by alterations in the mean size of depressor responses. Since all correlation coefficients are positive, it is inferred that the depressor responses produced by stimulation of the aortic nerve follow WILDER's "law of initial value". The conformity with this rule is the better the higher the values of the correlation coefficients. The strength of relationship between the resting blood pressure and the size of depressor responses is considered to reflect the efficiency of the homeostatic circulatory mechanism. 相似文献
6.
Rodrigo O. Marañón Claudio M. Joo Turoni Alfredo Coviello María Peral de Bruno 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(4):403-409
Little is known about the vascular actions of angiotensin II (Ang II) and nitric oxide (NO) in Amphibia. This study investigated
(1) Ang II contractility, (2) NO concentrations, and (3) correlations between Ang II contractility, NO concentration and mean
arterial pressure (MAP) in isolated Bufo arenarum toad aortic rings. Contractility was measured in isometric conditions, NO concentrations were determined by the Griess reaction,
and MAP was determined by a direct method. In isolated toad aortic rings, Ang II produced a contractile response (292.7 ± 89.2 mg;
n = 20). Furthermore, a contractile response to norepinephrine (NE) was also obtained. A significant correlation between both
the Ang II and NE contractile responses was found (r = 0.89; n = 11; P < 0.01). Administration of Ang II increased MAP values (Basal 16.8 ± 1.7; n = 19 vs. Ang II 28.4 ± 1.8 mmHg; n = 19; P < 0.001), and the increase of MAP by Ang II was positively correlated with the Ang II contractile response (P < 0.01). Administration of L-NAME also increased MAP values, and this effect was higher in those toads that presented a lower
pressure response to Ang II (Pearson r = −0.68; P < 0.05). NO was present in all aortic rings, and its concentrations were negatively related to the Ang II contractile response
(P < 0.036) and pressure response (Pearson r = −7.08; P < 0.001). These findings suggest that, in the B. arenarum toad, the NO system contra-regulates both the contractile and pressure Ang II responses, although its action could be different
in each specimen. 相似文献
7.
M. Nagai M. Iriki 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(5):611-616
Summary Selective thermal stimulation of the spinal cord caused changes in ventricular pressure (VP) and blood flow of the pulmocutaneous artery (PCBF) in the bullfrog,Rana catesbeiana, anaesthetized with urethane. Warming the spinal cord significantly increased VP from 28.4±2.5 to 37.2±3.5 mmHg (n=8) and PCBF from 24.5±1.4 to 29.5±2.0 ml/min (n=5). Spinal cord cooling significantly decreased VP from 29.3±2.5 to 24.0±1.9 mmHg (n=6) and PCBF from 22.4±1.4 to 18.5±1.7 ml/min (n=5). Although heart rate did not exhibit significant changes during thermal stimulation, changes in cardiac output were achieved by changes in VP, i.e. changes in stroke volume. Changes in VP were antagonized with propranolol, but not influenced by lower sympathectomy which eliminates the catecholamine release for the chromaffin tissue. Atropine significantly increased creased resting PCBF but failed to antagonize changes in PCBF. This shows that changes in PCBF during spinal cord thermal stimulation are not mediated by an active vasomotor mechanism, but result from changes in cardiac output. The present results show that changes in spinal cord temperature induce inotropic effects on the bullfrog heart through a -adrenergic mechanism of sympathetic nervous origin. 相似文献
8.
C A Courneya N Wilson J R Ledsome 《Canadian journal of physiology and pharmacology》1989,67(4):344-352
The influence of aortic baroreceptors and vagal afferent nerves on the release of immunoreactive vasopressin (iVP) and immunoreactive atrial natriuretic factor (iANF) was examined in anaesthetized rabbits. Changes in plasma concentrations of iVP and iANF, heart rate, mean arterial pressure, and right atrial pressure were measured in response to blood volume changes (+20, +10, -10, -20%). Carotid sinus pressure was maintained at 100 mmHg (1 mmHg = 133.3 Pa), and blood volume changes were performed before and after bilateral vagotomy (VNX) in all experiments. Two experimental groups were studied: rabbits with aortic depressor nerves intact (ADNI) and those with aortic depressor nerves sectioned (ADNX). Mean arterial and right atrial pressures decreased during haemorrhage and increased in response to volume expansion. Plasma iVP concentrations increased with haemorrhage and decreased with volume expansion in the ADNI group. Plasma iANF, however, decreased with haemorrhage and increased during volume expansion in both ADNI and ADNX groups. Vagotomy caused an increase in baseline plasma iANF in the ADNX group. The responses of iANF to blood volume changes were augmented after VNX and ADNX. The results show that neither the aortic baroreceptor nor the vagal afferent input are needed for the iANF response to changes in blood volume, over the range of +/- 20%. In contrast, intact aortic baroreceptors are essential for changes in circulating iVP in this preparation. 相似文献
9.
Maria Bernardete Cordeiro de Sousa Anette Hoffmann 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(3):381-386
Summary Electrical stimulation of the central nervous system of conscious toads with permanently implanted electrodes in regions related to orienting and avoidance responses induces cardiovascular (hypertension and tachycardia) and respiratory (increased intrapulmonary pressure) changes together with the somato-motor effects typical of these responses. Sympathetic activation occurs and the main peripheral mediator involved may be adrenergic, since the cardiovascular effects are almost completely blocket by systemic pretreatment with phentolamine and DCI.The cardiovascular changes obtained by central stimulation are qualitatively similar to those recorded for toads whose orienting and avoidance behaviors are obtained by the presentation of visual stimuli (presentation of a prey and of a black card moved over the experimental box). Variations in heart rhythm may occur in both cases in the absence of visible somatic manifestations or of other neurovegetative changes, thus showing the importance of this parameter as an index of sensory reception of biologically significant stimuli.The results are compared to those obtained under similar conditions in other non-mammalian vertebrates.Abbreviations
BP
blood pressure
-
EMG
electromyogram
-
ES
electrical stimulation
-
IPP
intrapulmonary pressure 相似文献
10.
S. Aota D. J. Randall 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):138-146
Ventilation frequency, opercular pressure amplitude, heart rate, dorsal aortic pressure, arterial pH, arterial O2 tension, and plasma catecholamine levels were recorded in rainbow trout, Oncorhynchus mykiss, during normoxia (19.7 kPa, 148 mmHg) or hyperoxia (51.2 kPa, 384 mmHg) after injection of various concentrations of catecholamines. In normoxic fish, adrenaline injection resulted in a depression of arterial O2 tension, hypoventilation due to a drop in ventilation frequency, and a drop in heart rate, while dorsal aortic pressure increased. Noradrenaline depressed ventilation frequency, but opercular pressure amplitude increased to a far greater extent, and dorsal aortic pressure increased. During hyperoxia, adrenaline injection lowered ventilation frequency, opercular amplitude and heart rate, but dorsal aortic pressure increased. The stimulatory effects of noradrenaline on ventilation were abolished during hyperoxia, but the cardiac responses were similar to those seen during normoxia. These results indicate that catecholamines can modify the ventilatory output from the respiratory centre, and modification of ventilation frequency can occur independently of opercular pressure amplitude.Abbreviations
f
g
ventilation frequency
- HPLC
high performance liquid chromatography
-
P
op
opercular pressure amplitude
-
f
h
heart rate
-
P
DA
dorsal aortic pressure
- pHa
arterial pH
-
P
aO2
arterial oxygen tension
-
PO2
oxygen tension 相似文献
11.
R. M. Bevan P. J. Butler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(5):349-354
Arterial blood pressure was monitored in voluntarily diving tufted ducks. Mean arterial blood pressure while diving increased during the pre-dive tachycardia, fell to resting levels on submersion, then gradually increased before peaking on surfacing. Estimated total peripheral resistance fell during the pre-dive and post-dive tachycardia, presumably to allow the oxygen stores to be loaded and replenished respectively and/or for carbon dioxide levels to be reduced. Changes in mean arterial blood pressure and total peripheral resistance suggest that peripheral vasoconstriction occurs in some vascular beds during a dive. An increase in arterial blood pressure (and therefore perfusion pressure) may be employed to increase blood flow and oxygen delivery to the active leg muscles.Abbreviations ecg
Electrocardiogram, f
H, heart rate
- MABP
mean arterial blood pressure
-
P
b
blood pressure(s)
- TPR
total peripheral resistance
-
V
b
cardiac output 相似文献
12.
Salgado HC Barale AR Castania JA Machado BH Chapleau MW Fazan R 《American journal of physiology. Heart and circulatory physiology》2007,292(1):H593-H600
Baroreflex responses to changes in arterial pressure are impaired in spontaneously hypertensive rats (SHR). Mean arterial pressure (MAP), heart rate (HR), and regional vascular resistances were measured before and during electrical stimulation (5-90 Hz) of the left aortic depressor nerve (ADN) in conscious SHR and normotensive control rats (NCR). The protocol was repeated after beta-adrenergic-receptor blockade with atenolol. SHR exhibited higher basal MAP (150 +/- 5 vs. 103 +/- 2 mmHg) and HR (393 +/- 9 vs. 360 +/- 5 beats/min). The frequency-dependent hypotensive response to ADN stimulation was preserved or enhanced in SHR. The greater absolute fall in MAP at higher frequencies (-68 +/- 5 vs. -38 +/- 3 mmHg at 90-Hz stimulation) in SHR was associated with a preferential decrease in hindquarter (-43 +/- 5%) vs. mesenteric (-27 +/- 3%) resistance. In contrast, ADN stimulation decreased hindquarter and mesenteric resistances equivalently in NCR (-33 +/- 7% and -30 +/- 7%). Reflex bradycardia was also preserved in SHR, although its mechanism differed. Atenolol attenuated the bradycardia in SHR (-88 +/- 14 vs. -129 +/- 18 beats/min at 90-Hz stimulation) but did not alter the bradycardia in NCR (-116 +/- 16 vs. -133 +/- 13 beats/min). The residual bradycardia under atenolol (parasympathetic component) was reduced in SHR. MAP and HR responses to ADN stimulation were also preserved or enhanced in SHR vs. NCR after deafferentation of carotid sinuses and contralateral right ADN. The results demonstrate distinct differences in central baroreflex control in conscious SHR vs. NCR. Inhibition of cardiac sympathetic tone maintains reflex bradycardia during ADN stimulation in SHR despite impaired parasympathetic activation, and depressor responses to ADN stimulation are equivalent or even greater in SHR due to augmented hindquarter vasodilation. 相似文献
13.
Electrical stimulation on the hypothalamus in alert cats increases the blood pressure and inhibits the baroceptor reflexes. In animals with extirpated sinocarotid and aortic nerves the pressor reactions are perversed to depressor ones at threshold stimulation of the hypothalamus. Meanwhile suprathreshold stimulation of this organ leads to emergence of depressor-pressor responses. It is suggested that inhibition of the baroceptor reflexes is one of the mechanisms of the hypertensive reaction emergence at stimulation of the hypothalamus. 相似文献
14.
H. Y. Xu K. R. Olson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(6):470-476
The importance of neuronal and lumenal vascular adrenoceptors in the regulation of vascular reactivity was examined in rainbow trout (Oncorhynchus mykiss), in vivo and in vitro. In vivo, ganglionic blockade with hexamethonium or -adrenoceptor blockade, with either phentolamine or prazosin, produced similar (7 mmHg) decreases in dorsal aortic blood pressure. The drop in dorsal aortic pressure produced by phentolamine or prazosin was due to reduced systemic vascular resistance. Neither the -adrenoceptor antagonist, phenoxybenzamine nor chemical sympathectomy with 6-hydroxy-dopamine affected dorsal aortic pressure. However, after chemical sympathectomy, phenoxybenzamine lowered dorsal aortic pressure to levels similar to that produced by either phentolamine or prazosin. Plasma epinephrine and norepinephrine concentrations increased four- and twofold, respectively, in sympathectomized fish. Sympathectomy also produced a leftward shift in the epinephrine dose/response curve of the in vitro perfused splanchnic vasculature, placing the effective catecholamine concentration well within the in vivo plasma levels. These results indicate that following chemical sympathectomy arterial blood pressure is stabilized by circulating catecholamines through the combined effect of increased plasma catecholamine concentrations and increased sensitivity of vascular adrenoceptors. Phenoxybenzamine is incapable of blocking neuronal vascular adrenoceptors but is a potent antagonist of the up-regulated adrenoceptors, suggesting that the latter are localized on the lumenal side of the vessel.Abbreviations 6OH-DA
6-hydroxy dopamine
-
EC
50
half-maximal response
- EDTA
ethylenediaminetetra-acetate
- PE
polyethylene
- PBS
phosphate-buffered saline
-
P
da
dorsal aortic pressure
- USP
United States Pharmacopeia 相似文献
15.
在麻醉兔,研究了刺激肾神经传入纤维与颈动脉窦压力感受性反射在减压反射中的相互作用。电刺激肾神经传入纤维引起平均动脉压(MAP)下降,下降程度在一定范围有赖于刺激频率。当颈动脉窦被隔离和主动脉神经切断后,随着颈动脉窦内压逐渐升高,刺激肾神经传入纤维引起的减压反应不断减弱。在45至135mmHg 之间的7个颈动脉窦内压(ISP)水平,刺激肾神经传入纤维,并画出刺激前和刺激时的 ISP-MAP 关系曲线。在颈动脉窦内压为75至105mmHg 之间,刺激肾神经传入纤维显著降低 ISP-MAP 关系曲线的斜率和对ISP 的平均动脉压反应范围。这些结果提示:(1)颈动脉窦压力感受器的传入冲动可调制刺激肾神经传入纤维的降压反应,在一定范围内与颈动脉窦内压呈反比;(2)刺激肾神经传入纤维明显减弱颈动脉窦的压力感受性反射。 相似文献
16.
Prostaglandin (PG) D3 has been identified as an inhibitor of human platelet aggregation, but little is known of the hemodynamic activity of this material. In morphine pretreated, chloralose-urethan anesthetized dogs, bolus intravenous injections (1, 3.2 and 10 μg/kg) of PGD3 and also PGD2 were associated with marked, dose-related increases in pulmonary arterial pressure. Cardiac index and rate increased, while peripheral vascular resistance decreased in response to injections of PGD3. A biphasic (depressor followed by a pressor phase) effect on systemic arterial pressure was observed after PGD2, while PGD3 was associated with dose-related depressor responses. Graded intravenous infusions (0.25, 0.50 and 1.0 μg/kg/min) of PGD3 and PGD2 were associated with qualitatively similar cardiovascular responses. Quantitatively, PGD3 infusions were associated with greater decreases in peripheral vascular resistance and greater increases in cardiac output, heart rate, and peak left ventricular dp/dt than were infusions of PGD2. In contrast, PGD3 was less potent than PGD2 as a pulmonary pressor material. Systemic arterial pressure responses to infusions of the prostaglandins were variable. In these experiments, PGD3 and PGD2 were associated with qualitatively similar cardiovascular responses characterized by peripheral vasodilatation. 相似文献
17.
《Peptides》2013
Recent data suggests that neurons expressing the long form of the leptin receptor form at least two distinct groups within the caudal nucleus of the solitary tract (NTS): a group within the lateral NTS (Slt) and one within the medial (Sm) and gelantinosa (Sg) NTS. Discrete injections of leptin into Sm and Sg, a region that receives chemoreceptor input, elicit increases in arterial pressure (AP) and renal sympathetic nerve activity (RSNA). However, the effect of microinjections of leptin into Slt, a region that receives baroreceptor input is unknown. Experiments were done in the urethane-chloralose anesthetized, paralyzed and artificially ventilated Wistar or Zucker obese rat to determine leptin's effect in Slt on heart rate (HR), AP and RSNA during electrical stimulation of the aortic depressor nerve (ADN). Depressor sites within Slt were first identified by the microinjection of l-glutamate (Glu; 0.25 M; 10 nl) followed by leptin microinjections. In the Wistar rat leptin microinjection (50 ng; 20 nl) into depressor sites within the lateral Slt elicited increases in HR and RSNA, but no changes in AP. Additionally, leptin injections into Slt prior to Glu injections at the same site or to stimulation of the ADN were found to attenuate the decreases in HR, AP and RSNA to both the Glu injection and ADN stimulation. In Zucker obese rats, leptin injections into NTS depressor sites did not elicit cardiovascular responses, nor altered the cardiovascular responses elicited by stimulation of ADN. Those data suggest that leptin acts at the level of NTS to alter the activity of neurons that mediate the cardiovascular responses to activation of the aortic baroreceptor reflex. 相似文献
18.
Hines T 《American journal of physiology. Regulatory, integrative and comparative physiology》2000,278(6):R1433-R1440
Pregnancy is associated with blunted reflex responses to cardiac and arterial baroreceptor stimulation. We tested the hypothesis that arterial baroreceptor afferent discharge is attenuated in response to a pressure stimulus in pregnant rats. Multifiber aortic depressor nerve activity (ADNA), mean arterial pressure (MAP), and heart rate were measured in anesthetized (pentobarbital sodium, 35 mg/kg ip) late-pregnant and virgin rats in response to increases ?phenylephrine (PE), 1.5-24 microg. kg(-1). min(-1) and 1-16 microg/kg and decreases ?sodium nitroprusside (SNP), 5-80 microg. kg(-1). min(-1) and 0.05-16 microg/kg in MAP. Resting MAP was lower in pregnant rats, but changes in MAP were similar to those in virgin rats during both PE and SNP administration. ADNA was significantly attenuated in pregnant animals during both PE and SNP infusions (P < 0.05) due to a more rapid adaptation to the pressure stimulus. Bolus drug administration evoked similar changes in MAP and ADNA in both groups; however, the maximum decrease in ADNA was achieved at the lowest dose of SNP in pregnant rats. Thus baroreceptor afferent discharge is attenuated in pregnant rats, and this involves a more rapid adaptation to a pressure stimulus. 相似文献
19.
P. Arbeille D. Sigaudo A. Pavy Le Traon S. Herault M. Porcher C. Gharib 《European journal of applied physiology and occupational physiology》1998,78(3):208-218
The first objective of this study was to confirm that 4 days of head-down tilt (HDT) were sufficient to induce orthostatic
intolerance, and to check if 4 days of physical confinement may also induce orthostatic intolerance. Evidence of orthostatic
intolerance during tilt-up tests was obtained from blood pressure and clinical criteria. The second objective was to quantify
the arterial and venous changes associated with orthostatic intolerance and to check whether abnormal responses to the tilt
test and lower body negative pressure (LBNP) may occur in the absence of blood pressure or clinical signs of orthostatic intolerance.
The cerebral and lower limb arterial blood flow and vascular resistance, the flow redistribution between these two areas,
and the femoral vein distension were assessed during tilt-up and LBNP by ultrasound. Eight subjects were given 4 days of HDT
and, 1 month later, 4 days of physical confinement. Tilt and LBNP test were performed pre- and post-HDT and confinement. Orthostatic
intolerance was significantly more frequent after HDT (63%) than after confinement (25%, P<0.001). Cerebral haemodynamic responses to tilt-up and LBNP tests were similar pre- and post-HDT or confinement. Conversely,
during both tilt and LBNP tests the femoral vascular resistances increased less (P<0.002), and the femoral blood flow reduced less (P<0.001) after HDT than before HDT or after confinement. The cerebral to femoral blood flow ratio increased less after HDT
than before (P<0.002) but remained unchanged before and after confinement. This ratio was significantly more disturbed in the subjects who
did not complete the tilt test. The femoral superficial vein was more distended during post-HDT LBNP than pre-HDT or after
confinement (P<0.01). In conclusion, 4 days of HDT were enough to alter the lower limb arterial vasoconstriction and venous distensibility
during tilt-up and LBNP, which reduced the flow redistribution in favour of the brain in all HDT subjects. Confinement did
not alter significantly the haemodynamic responses to orthostatic tests. The cerebral to femoral blood flow ratio measured
during LBNP was the best predictor of orthostatic intolerance.
Accepted: 12 December 1997 相似文献
20.
Dona F. Boggs Geoffrey F. Birchard 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(5):641-648
Summary The burrow-dwelling woodchuck (Marmota monax) (mean body wt.=4.45±1 kg) was compared to a similar-sized (5.87±1.5 kg) but arboreal rodent, the porcupine (Erithrizon dorsatum), in terms of its ventilatory and heart rate responses to hypoxia and hypercapnia, and its blood characteristics.V
T,f,T
I andT
E were measured by whole-body plethysmography in four awake individuals of each species. The woodchuck has a longerT
E/T
TOT (0.76±0.03) than the porcupine (0.61±0.03). The woodchuck had a higher threshold and significantly smaller slope to its CO2 ventilatory response compared to the porcupine, but showed no difference in its hypoxic ventilatory response. The woodchuck P50 of 27.8 was hardly different from the porcupine value of 30.7, but the Bohr factor, –0.72, was greater than the porcupine's, –0.413. The woodchuck breathing air has PaCO2=48 (±2) torr, PaO2=72 (±6), pHa=7.357 (±0.01); the porcupine blood gases are PaCO2=34.6 (±2.8), PaO2=94.9 (±5), pHa=7.419 (±0.03), suggesting a difference in PaCO2/pH set points. The woodchuck exhibited no reduction in heart rate with hypoxia, nor did it have the low normoxic heart rate observed in other burrowing mammals. 相似文献