摘要:

Cardiac and vascular function is mainly under autonomic nervous control within seconds to minutes, although the control is not mature at birth. We studied sympatho‐vagal control of heart rate and blood pressure in chronically catheterized foetal lambs in the last trimester of gestation. Power spectral analysis was used to quantitate the frequency‐specific heart rate variability (HRV) and blood pressure variability. We performed 15 experiments in seven foetal lambs. These preliminary studies showed that parasympathetic blockade by atropine (eight experiments) had no significant effect on the distribution of HRV to different frequencies. Beta‐sympathetic blockade by propranolol (seven experiments) decreased the ratio of low and mid to high frequency (0.025‐0.13 to 0.13‐1.00 Hz) HRV (P= 0.02). The increased high frequency HRV in the absence of a similar increase in blood pressure variability and tracheal pressure variability suggests enhanced baroreflex responsiveness after propranolol administration. The frequency‐specific sympathetic control of HRV in foetal lambs, the change in ratio of low and mid to high frequency HRV, might have clinical implications in estimating the level of foetal sympathetic activation in the follow‐up of high‐r

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09890.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Nitric oxide (NO) is known to regulate basal coronary blood flow (CBF). The objective of the present study was to examine the importance of NO in CBF regulation at various coronary arterial pressures (CAPs)in vivo.Experiments were performed in 11 open‐chest pentobarbitone sodium anaesthetized pigs. CAP was reduced in steps by a hydraulic occluder on the mid left anterior descending coronary artery (LAD) before and after a 5‐min intracoronary infusion of the inhibitor of NO synthesis, A‐nitro‐L‐arginine (NOARG, 30/imo\min“1). CAP was recorded and NOARG infused through a catheter inserted into the LAD just distal to the occluder. CBF was measured by Doppler flowmetry on the LAD.NOARG significantly reduced CBF by 11±4, 20 ± 5, 10 ± 3, 15 ± 4, 19 ± 2, 25 ± 4 and 25 ± 5 mL min‐1100 g‐1(mean ± SE) at CAPs of 30 (n = 6), 40 (n = 9), 50 (n= 9), 60 (n = 9), 70 (n = 9), 80 (n =8) and 90 (n = 6) mmHg, respectively. These decrements were not statistically different, but the percentage reductions in CBF after infusion of NOARG were significantly greatest at the lowest CAPs. The slight haemodynamic alterations induced by NOARG could not explain the reductions in CBF. Thus, the reductions in CBF after infusion of NOARG were caused by inhibition of a continuous NO release from the coronary endothelium.Coronary NO contributes significantly to CBF at all CAPs between 30 and 90 mmHg. The pronounced reduction in CBF during NO inhibition at the lower CAPs indicates an important vasodilating role of intact endothelium in a region supplied by a s

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09891.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Different conclusions have been reached with regard to the effect of endothelin (ET‐1) on cardiac contractility. We examined systolic and diastolic function in response to constant known concentrations of ET‐1 with or without ET‐1 induced reductions in coronary flow (CF). Rat hearts (n= 21) were buffer‐perfused using constant coronary flow (cCF) or constant perfusion pressure (cPP). Left ventricular function was assessed isovolumically. Addition of ET‐1 (10‐9M) in the cCF group caused a gradual increase in PP from 61 ± 2 to 165±6mmHg (mean±SE) (P<0.01). Within 10 min left ventricular systolic pressure (LVSP) increased from 111 ± 2 to a maximum of 134±4mmHg (P<0.01) and[L\dP/dt]increased from 1640 ± 81 to a maximum of 2020 ± 92 mmHg s“1(P<0.01). After 15 min left ventricular end diastolic pressure (LVEDP), a measure of diastolic stiffness (DS), also increased. With ET‐1 (108M), similar haemodynamic alterations appeared more rapidly. In the cPP group, ET‐1 (10”9M) caused a sharp decrease in CF and LVSP fell from 115 ± 8 to 62±12 mmHg at 10 min (P<0.001). Systolic function remained stable at a reduced level for 1 h. DS did not change. Thus, ET‐1 possesses positive inotropic effects and increases diastolic stiffness. Both effects may be masked by vaso

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09892.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The vascular responses to cyclopiazonic acid (CPA), an inhibitor of the Ca2+‐ATPase in the sarcoplasmic reticulum, were investigated in the rabbit femoral artery, suspended in an organ chamber for isometric tension recordings. CPA produced rhythmic contractions in the femoral artery which had been contracted with phenylephrine. CPA, however, did not induce the rhythmic responses in endothelium‐denuded arteries.NG‐nitro‐L‐arginine methyl ester and methylene blue, inhibitors of the formation and the action of nitric oxide, respectively, failed to antagonize the CPA‐induced rhythmic contractions in the phenylephrine‐contracted artery. In contrast, the CPA‐induced rhythmic contractions were abolished by charybdotoxin, a Ca2+‐activated K+channel antagonist, but not by glibenclamide, a blocker of the ATP‐sensitive K+channel. Nifedipine also inhibited the CPA‐induced rhythmic contractions in the endothelium‐intact artery and relaxed the endothelium‐denuded artery treated with CPA. These results indicate that the CPA‐induced rhythmic contractions in the phenylephrine‐contracted rabbit femoral artery may be attributed to the periodic inactivation of the voltage‐dependent Ca2+channel, presumably regulated by the Ca2+‐activated K+channel. The activation of the K+channel by CPA might occur onl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09893.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effect of removal of cerebrovascular sympathetic, parasympathetic or sensory nerve on brain cortical blood flow and spontaneous vasomotion during changes in systemic blood pressure was studied by laser‐Doppler flowmetry in anaesthetized rats. Selective section of sympathetic fibres along the internal carotid artery markedly affected the ability to autoregulate, as measured in microvessels of the middle cerebral arterial territory. Removal of the parasympathetic nerves tended to reduce the ability to autoregulate, whereas no significant influence was found after sensory denervation. Following the denervations, spontaneous vasomotion was not significantly affected in frequency or amplitud

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09894.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Plasma volume (PV) changes to 15 min quiet standing were analysed (Hb/Hct‐alterations) in two studies (nine and 11 healthy males). Data confirmed and extended our findings that blood, arterial or venous, sampled on standing fails to reveal the induced overall haemoconcentration (PV loss). First, standing led to markedly incomplete mixing of blood between circulatory compartments. Secondly, with sampling of antecubital venous blood, haemoconcentration was strongly affected by regional plasma loss and, apparently equally important, by regional blood flow. These difficulties were circumvented, however, by the finding that the PV restitution (haemoconcentration) in the recumbent subject after standing fitted invariably a monoexponential function with striking precision. It allowed, by extrapolation, a seemingly superior definition of the PV reduction at the very end of standing as supported by the fact that PV changes from Hb/Hct and from IgM protein concentration changes were similar, refuting that Fcell‐changes contributed to the pronounced Hb/Hct changes. The described novel approach revealed a nicely reproducible PV loss of no less than 692 ± 46 mL (18.1 ±0.6%, Study I; 18.4 ± 0.5%, Study II), or ± 11% reduction of blood volume, showing that quiet standing leads to a much more rapid and haemodynamically important decrease in PV than reported previously. Yet, PV was virtually restored within 20 min of recumbency after standing, with 50% recovery within 6 min and regain of as much as 70 mL in the very first min. The latter data indicate that the body possesses a surprising capacity for rapid fluid transfer from the extra‐ to the intravascu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09895.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In ordertofind an explanationforthe discrepancy between previous reports on the consistency of the blink reflex response with stimulation of the mental nerve, the habituation of the blink reflex was studied with stimulation of the supraorbital and mental nerves in 14 healthy adults. A series of eight electrical stimuli was delivered to the distributions of the nerves on each side at frequency rates of 1.0, 0.5, 0.2 and 0.1 Hz. The latencies and peak‐to‐peak amplitudes of the ipsilateral late blink reflex components (R2i) were measured. The habituation phenomenon was analysed by means of multivariate analysis of the amplitudes, the nerve and frequency effects were determined by means of a repeated measures analysis of variance model. The blink reflex showed more pronounced amplitude attenuation of the consecutive responses with stimulation of the mental than the supraorbital nerve at rates of 0.5 and 0.2 Hz, and marginally so also at 0.1 Hz. For the supraorbital nerve, habituation could be demonstrated with stimulation frequencies of 1.0 and 0.5 Hz, while for the mental nerve a statistically significant habituation phenomenon was found even with the lowest repetition rate of 0.1 Hz. The greater tendency of the mental nerve blink reflex to habituate is obviously one reason why it has previously sometimes been considered too inconsistent to be useful in clinical practice. For the recording of the supraorbital nerve blink reflex, a 10 s interval between stimuli is adequate, whereas longer interstimulus intervals may have to be adopted to obtain consistent blink reflex responses with stimulation of the mental ne

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09896.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The present study was undertaken to investigate the firing patterns, location and projections of vertical eye movement‐related neurones in the Forel's field H (FFH), the interstitial nucleus of Cajal (INC), and reticular formation of the mesodiencephalic junction (MDJ) in chronically prepared alert cats. A total of 456 neurones in the medial MDJ with firing closely related to vertical eye movements was examined using antidromic microstimulation and spike‐triggered averaging technique. On the basis of their firing patterns, these neurones were classified into five groups, i.e. burst neurones (BNs), burst‐tonic neurones (BTNs), tonic neurones (TNs), augmenting neurones (ANs) and pause neurones (PNs). BNs were located mainly in the dorsomedial part of the FFH. Most of TNs were found more caudally than BNs. BTNs and PNs were located further caudally, within the INC and nearby reticular formation. ANs were located mainly in the dorsolateral part of the FFH. Both medium‐lead BNs (MLBNs) and BTNs projected to the inferior rectus (IR) subdivision of the oculomotor nucleus on both sides. MLBNs projected to the trochlear nucleus as well through collateral branches of the axon projecting to the oculomotor nucleus. Downward and upward MLBNs made direct excitatory and inhibitory connections, respectively, with IR motorneurones. These results suggest that many kinds of neurones in the paramedian regions of MDJ play a significant role in the genesis of vertical eye mo

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09897.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The effect of 17β‐oestradiol and 3α‐hydroxy‐5α‐pregnane‐20‐one (allopregnanolone) on the action potentials in the Schaffer collateral pathway was investigated in hippocampus CA1. Slices from male and female guinea‐pigs and female rats were used. In the rat three groups were studied: (a) untreated prepubertal rats at day 25 after partus; (b) rats injected on day 26 with 10 IU of equine serum gonadotropin studied on day 28, when in the pro‐oestrus follicular phase; and (c) on day 32 when in the luteal phase. The allopregnanolone (12.6 μ.M, 0.5 nL) was applied locally in stratum oriens‐pyramidale. The 17β‐oestradiol (0.7 nM) was perfused (4 mL min‐1) or applied locally. The amplitude of the population spike in stratum pyramidale was increased by oestradiol in guinea‐pigs of both sexes and in all the three groups of rats. Allopregnanolone decreased the amplitude of the population spike in the guinea‐pigs and in the luteal phase rats. The effect appeared within seconds after the application of the drugs. The allopregnanolone inhibition of the population spike was increased by perfusion with oestradiol in the guinea‐pigs and in the luteal phase rats. This effect appeared within 7 min, and improved with increasing length of the perfusion (7–71 min). It remained for 55 min after return to perfusion with artificial cerebrospinal fluid. In prepubertal and follicular phase rats the allopregnanolone inhibition was seen only after perfusion with oestradiol for more than 15 min. The results show that 17β‐oestradiol increases the allopregnanolone inhibition and that this inhibition is most efficie

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09898.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Members of the epidermal growth factor (EGF) family have many different effects on ovarian cells including a strong inhibition of estradiol‐17β production. An increased binding of the EGF family to its receptor is seen at the time of ovulation. The aim of the present study was to measure the mRNA levels of the EGF receptor in the preovulatory follicle and to see if the levels are still high after functional luteolysis.The mRNA of the EGF receptor was measured in whole ovaries, follicles and corpora lutea. Pregnant mare serum gonadotrophin (PMSG) stimulated rats were used to get denned follicles. To achieve luteolytic corpora lutea on day 11, the adult female pseudopregnant rat model was used. Determination of the EGF receptor mRNA was performed with solution hybridization analysis, using a 768 bp long probe of the human EGF receptor (2318–3085).A two‐fold increase in the mRNA levels of the EGF receptor was registered between 09.00 and 21.00 h during the proestrus day in the preovulatory follicle. Concurrently, serum estradiol‐17β levels decreased from 420 ± 65 to 79 ± 6 pM. High levels of EGF receptor proteins in the preovulatory follicle were verified by immunohistochemistry. The levels of EGF receptor mRNA was decreasing from 25.4 ± 4.4 fmol mg‐1in the corpus luteum on day 1 to 7.6 ± 9.9 fmol mg‐1on day 11. Thus, the high amounts of EGF receptor in the ovary during the late preovulatory period might be involved in the regulation of ovarian estradi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1995.tb09899.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY