摘要:

SUMMARY1. Non‐invasive continuous finger blood pressure (BP) measurement and a spectral technique based on the Fourier transform (FT) were recently combined to quantify short‐term fluctuations in haemodynamic variables.2. Systolic BP (SBP) recording combined low frequency (LF, Mayer waves) plus high frequency (HF, respiratory) oscillations. The presence of HF oscillations of SBP probably reflects fluctuations in cardiac output. Heart rate (HR) also exhibited a combination of low and HF (respiratory) oscillations. The vagus nerve mediates the efferent control of the respiratory sinus arrhythmia (RSA).3. During controlled breathing in a supine position, a change in SBP is associated with an opposite consequent change in HR. Respiratory sinus arrhythmia could therefore depend on the baroreceptor‐HR response to underlying SBP oscillations.4. The fast regulation of R‐R interval by SBP through the baroreceptor‐HR reflex may explain why the respiratory variations in the diastolic BP

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01391.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. The inhibitory effects produced by activation of the medial region of caudal medulla on activities of the left and right cardiac sympathetic, vagus and greater splanchnic nerves were studied in chloralose‐urethane anaesthetized cats.2. Electrical stimulation of the medial region produced an 80–92% inhibition of the sympathetic nerve activities, and a 45% and 58% inhibition of the left and right cardiac vagal nerve activities, respectively. There were no significant differences between effects elicited in the left and right autonomic nerves. Similar but smaller inhibitory effects were produced by micro‐injection of sodium glutamate (0.5 mol/L) or DL‐homocysteic acid (50 mmol/L) to the same medullary sites.3. These data suggest that neurons residing in the medial medullary region exert strong inhibitory effects on autonomic nerve activities. Since the vasculature is principally innervated by sympathetic nerves, inhibition of sympathetic nerve activities might be the principal factor responsible for the depressor effects caused by activation of the medial region of caudal medulla. The heart is innervated both by sympathetic and parasympathetic nerves. Thus, their simultaneous inhibition during activation of the medial region elicits only a weak and variable inhibition of th

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01392.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. The positive inotropic and chronotropic responses to adrenoceptor agonists (noradrenaline, phenylephrine), to compounds which increase cAMP by post‐adrenoceptor mechanisms (forskolin, theophylline and dibutyryl cAMP) and to calcium chloride were measured in isolated rat atria and papillary muscles from both ventricles.2. Noradrenaline produced similar maximal inotropic responses to calcium chloride in all tissues. Forskolin gave similar responses to calcium chloride in atrial but not ventricular tissues; the reverse was observed with dibutyryl cAMP. Phenylephrine and theophylline produced significantly smaller inotropic responses than calcium chloride in all tissues, especially in ventricular tissues.3. Maximal chronotropic responses to noradrenaline, theophylline and dibutyryl cAMP were similar. Forskolin produced significantly greater responses while calcium chloride and phenylephrine produced significantly smaller responses than noradrenaline.4. These results show that the maximal positive inotropic response of some agonists is markedly dependent on the tissue chosen. Further, chronotropic responses in right atria do not mimic inotropic responses in left atri

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01393.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. A non‐invasive tail cuff method was validated against direct intra‐arterial blood pressure measurements (r2>0.9) and then used to measure the systolic blood pressure (SBP) responses to air‐jet stimulation in mature conscious Sprague‐Dawley (SD) and spontaneously hypertensive rats (SHR). The experiments with the SHR were conducted in parallel with age matched SD rats.2. All rats were trained to remain in perspex holders and when their SBP had stabilized, a jet of air of 10 min duration was directed at the rat's nose via rubber tubing. The blood pressure was measured during the first, fifth and tenth minute.3. The maximum SBP response normally occurred during the first min of air‐jet stimulation and averaged + 30 mmHg in the SHR and +21 mmHg in the SD. Although of higher magnitude in the SHR, when expressed as a percentage of the control SBP, the rise was similar for both strains, 13% and 14%, respectively.4. The pressor response of three SD rats stimulated daily for up to 12 days did not show any evidence of habituation to the stimulus.5. The pressor responses to air‐jet stimulation were abolished in anaesthetized rats, suggesting that they are primarily higher centr

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01394.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. This study investigated the influences of calcium‐channel blocking agents verapamil and diltiazem on platelet responses induced by arginine vasopressin (AVP) and lysine vasopressin (LVP).2. The substances inhibited platelet aggregation induced by both low and high AVP concentrations, LVP and adrenaline plus AVP. IC50 values of each drug are lower than those determined for ADP‐ and collagen‐elicited aggregation. Verapamil and diltiazem also decreased AVP‐induced thromboxane B2synthesis.3. Other series of experiments showed that the addition of ethyleneglycol‐bis‐(β‐amino‐ethyl ether)N, N'‐tetra‐acetic acid to platelet‐rich plasma samples also prevented the platelet response to vasopressin polypeptides.4. Our data provide evidence that the effects of verapamil and diltiazem on vasopressin‐induced platelet responses may be directly related to inhibition of ext

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01395.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. We previously found that adrenaline and noradrenaline exert essentially opposite effects on clearance from plasma of chylomicron‐like emulsions injected intravenously in rats, suggesting mechanisms that may be implicated in the atherogenic effects of chronic stress and hypertension and conversely in the protective effect of regular exercise.2. The mechanisms underlying the effects of adrenaline and noradrenaline have now been investigated. Chronic adrenergic blockade with either the α1‐receptor antagonist doxazosin or the β‐receptor antagonist propranolol slowed the clearance of labelled emulsion lipids from plasma of normal Wistar rats. The results with doxazosin were unexpected in view of its capacity to decrease plasma triglycerides in patients.3. In spontaneously hypertensive rats (SHR) the clearance of triolein (TO) was very slow compared with normal Wistar rats. Emulsion TO clearance provides a measure of lipolysis by lipoprotein lipase, and a defect in clearance indicates either defective enzyme action or poor perfusion of capillary beds rich in enzyme. Defective enzyme activity in SHR was excluded, suggesting redistribution of blood flow away from skeletal muscle and adipose tissue. In SHR the TO clearance from injected chylomicron‐like emulsions was improved by blockade with doxazosin compared with control untreated SHR.4. The β2‐adrenoreceptor agonist Fenoterol was infused intravenously during clearance of an injected lipid emulsion. Clearance of radiolabelled cholesteryl oleate (CO) was clearly slowed while there was a lesser reduction of TO clearance rate. Emulsion CO clearance provides a measure of the uptake of lipoprotein remnants by the liver, and a defect in clearance of CO indicates either defective ligand (apolipoprotein E)‐receptor interaction or decreased perfusion of the splanchnic bed. Isoprenaline, a non‐selective β‐adrenergic agonist, gave similar results. Both compounds reduced mean arterial pressure by about 20–40 mmHg at the doses employed, indicating that the β1(cardiac) effect of the isoprenaline was insufficient to offset its vasodilatatory effect on skeletal muscle arterioles (β2).5. The α‐agonist phenylephrine, at a dose which moderately raised mean arterial pressure, slowed clearance of both TO and CO for the first 12 min after injection of emulsion but at later time points clearances caught up with the controls.6. Administration of a mixture of isoprenaline and phenylephrine produced definite enhancement of both TO clearance and CO clearance. The effect of the mixture was opposite to the effects of ***of either agonist alone, demonstrating clearly that direct effects on lipoprotein lipase activity or receptor mediated processes were not involved.7. Angiotensin II both alone and especially in conjunction with complete autonomic blockade, markedly reduced clearance of emulsion TO and CO.8. The results are consistent with our previous interpretations that regional blood flow regulates the removal from plasma of rapidly cleared chylomicron‐like emulsions more than regulation by enzymes or receptor‐mediated uptake. The results with angiotensin II indicate the importance and lack of specificity of haemodynamic effects on the met

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01396.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARY1. Adrenocorticotrophin (ACTH) administration produces an adrenally dependent rise in blood pressure in rats.2. The haemodynamic and metabolic effects of ACTH were examined in nephrectomized, 5/6 nephrectomized and orchidectomized male Sprague‐Dawley rats and sham operated controls.3. Reduction in renal mass did not increase the blood pressure rise produced by ACTH.4. Gonadectomy did not reduce the blood pressure rise produced by ACTH, which was slightly higher in castrated animal

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1991.tb01397.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY