Effects of microgravity elicited by parabolic flight on abdominal aortic pressure and heart rate in rats.

Abdominal aortic pressure (AAP), heart rate (HR), and aortic nerve activity (ANA) during parabolic flight were measured by using a telemetry system to clarify the acute effect of microgravity (microG) on hemodynamics in rats. While the animals were conscious, AAP increased up to 119 +/- 3 mmHg on exposure to microG compared with the value at 1 G (95 +/- 3 mmHg; P < 0.001), whereas AAP decreased immediately on exposure to microG under urethane anesthesia (microG: 72 +/- 9 mmHg vs. 1 G: 78 +/- 8 mmHg; P < 0.05). HR also increased during microG in conscious animals (microG: 349 +/- 12 beats/min vs. 1 G: 324+9 beats/min; P < 0.01), although no change was observed under anesthesia. ANA, which was measured under anesthesia, decreased in response to acute microG exposure (microG: 33 +/- 7 counts/s vs. 1 G: 49 +/- 5 counts/s; P < 0.01). These results suggest that microG essentially induces a decrease of arterial pressure; however, emotional stress and body movements affect the responses of arterial pressure and HR during exposure to acute microG.     

Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat

The rostral ventrolateral medulla contains presympathetic neurons that project monosynaptically to sympathetic preganglionic neurons (SPN) in the spinal cord and are essential for the tonic and reflex control of the cardiovascular system. SPN directly innervate the adrenal medulla and, via postganglionic axons, affect the heart, kidneys, and blood vessels to alter sympathetic outflow and hence blood pressure. Over 80% of bulbospinal, catecholaminergic (C1) neurons contain pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA. Activation of PACAP receptors with intrathecal infusion of PACAP-38 causes a robust, prolonged elevation in sympathetic tone. Given that a common feature of most forms of hypertension is elevated sympathetic tone, this study aimed to determine in the spontaneously hypertensive rat (SHR) and the Wistar Kyoto rat (normotensive control) 1) the proportion of C1 neurons containing PACAP mRNA and 2) responsiveness to intrathecal PACAP-38. We further investigated whether intrathecal infusion of the PACAP antagonist, PACAP(6-38), reduces the hypertension in the SHR. The principal findings are that 1) the proportion of PACAP mRNA-containing C1 neurons is not different between normotensive and hypertensive rats, 2) intrathecal PACAP-38 causes a strain-dependent, sustained sympathoexcitation and tachycardia with variable effects on mean arterial pressure in normotensive and hypertensive rats, and 3) PACAP(6-38) effectively attenuated the effects of intrathecal PACAP-38, but had no effect alone, on any baseline variables. This finding indicates that PACAP-38 is not tonically released in the spinal cord of rats. A role for PACAP in hypertension in conscious rats remains to be determined.     

Changes in blood pressure, heart rate and blood constituents during heat exposure in men with elevated blood pressure

Although the vascular volume response of hypertensive men during exercise has been rather well characterized, the effect of resting heat exposure in this patient population has not been examined. This was done in the present report in seven men with high blood pressure (BP) (i.e., diastolic pressure greater than 12 kPa (90 mmHg) upon initial interview) and 5 normotensive control subjects. 50 min after each subject had consumed an amount of water equal to 1% of his body weight, he reclined on a cot. 10 min later the subject was carried into an environmental chamber equilibrated at Tdb = 45 degrees C, Twb = 28 degrees C. Free-flowing venous blood samples were obtained from a cubital vein, and BP and heart rate were measured, before the heat exposure and at 15 min intervals during the experiment. Within 30 min systolic, diastolic and mean BP of the high BP subjects had decreased to normal levels; no BP changes were detected in normotensive subjects. Accompanying this depressor response was an exaggerated elevation in plasma glucose concentration. No alterations were found with haematocrit, plasma osmolality or electrolytes, or total protein and albumin. The data suggest that heat exposure may have been more stressful for the subjects with high BP than for their controls. This finding implies that phasic depressor responses may be as important as phasic pressor episodes in the aetiology of established essential hypertension.     

延髓腹外侧头端区注射肾上腺髓质素对大鼠血压、心率和肾交感神经活动的影响

本研究在 3 4只麻醉Sprague Dawley大鼠观察了延髓腹外侧头端区内微量注射肾上腺髓质素 ( 10μmol/L ,2 0 0nl)对平均动脉压 (MAP)、心率 (HR)和肾交感神经放电 (RSNA)的影响。实验结果如下 :( 1)延髓腹外侧头端区内微量注射肾上腺髓质素可引起MAP、HR、和RSNA明显增加 ,分别由 99 0 9± 3 3 2mmHg ,3 70 78± 7 84bpm和 10 0± 0 %增至 113 5 7± 3 64mmHg (P <0 0 0 1) ,3 83 2 8± 7 3 8bpm (P <0 0 0 1)和 12 3 72±2 74% (P <0 0 0 1) ;( 2 )降钙素基因相关肽受体阻断剂CGRP8 3 7( 10 0 μmol/L ,2 0 0nl)不能阻断肾上腺髓质素的上述效应 ;( 3 )静脉注射NO前体L 精氨酸 ( 10 0mg/kg ,0 2ml)可消除肾上腺髓质素的上述效应。以上结果提示 ,肾上腺髓质素作用于延髓腹外侧头端区可产生显著的心血管作用 ,此作用不是由降钙素基因相关肽受体介导 ,但可被NO所阻断     

Autonomic nervous control of blood pressure and heart rate during hypoxia in the cod,Gadus morhua

Summary The autonomic nervous and possible adrenergic humoral control of blood pressure and heart rate during hypoxia was investigated in Atlantic cod. The oxygen tension in the water was reduced to 4.0–5.3 kPa (i.e.. P_wO₂=30–40 mmHg), and the fish responded with an immediate increase in ventral and dorsal aortic blood pressure (P _va P _da), as well as a slowly developing bradycardia. The plasma concentrations of circulating catecholamines increased during hypoxia with a peak in the plasma level of noradrenaline occurring before the peak for adrenaline. Bretylium was used as a chemical tool to differentiate between neuronal and humoral adrenergic control of blood pressure and heart rate (f _H) during hypoxia. The increase in P _va and P _da in response to hypoxia was strongly reduced in bretylium-treated cod, which suggests that adrenergic nerves are responsible for hypoxic hypertension. In addition, a small contribution by circulating catecholamines to the adrenergic tonus affecting P _va during hypoxia was suggested by the decrease in P _va induced by injection of the -adrenoceptor antagonist phentolamine. The cholinergic and the adrenergic tonus affecting heart rate were estimated by injections of atropine and the -adrenoceptor antagonist sotalol. The experiments demonstrate an increased cholicholinergic as well as adrenergic tonus on the heart during hypoxia.     

Dynamics of blood pressure, pulse wave transit time and systolic timei intervals during acute gravity changes induced by parabolic flight

To investigate cardiovascular adaptation to transient microgravity (Microgravity), we measured RR intervals (RRI), arterial blood pressure (BP), pulse wave transit time (PTT) and systolic time intervals (STI) during parabolic flight. Our results demonstrate that during microgram RRI, BP and PTT are subject to a rapid adaptation likely mediated by the baroreflex whereas STI changes with microgravity but does not present further adaptation.     

Gradual adjustment of circaseptan-circadian blood pressure and heart rate rhythms after a trans-9-meridian flight.

Circadian and circaseptan adjustment of blood pressure and heart rate after a transmeridian flight by a family of four was relatively fast, but it was not abrupt; it was not completed during the first week in the new setting. Gradual changes continued for the ensuing three weeks. The circadian and circaseptan rhythm characteristics and their adjustment in particular differed among variables in the husband: the circadian component of heart rate adjusted more rapidly than that of blood pressure. The adjustment also differed among two members of the family. A new phenomenon, namely a difference in circadian rhythm adjustment between husband and wife, is also described herein: the wife's circadian rhythm in blood pressure advanced by 9 hours within the 4-week span of recording following a 9-hour advance in living routine (after a 9-zone transmeridian flight); since both schedule and rhythm moved in the same direction (albeit not at the same rate), the behavior may be dubbed concursive. By contrast, the husband delayed to achieve the same adjustment: his behavior was anticursive. The phenomenon of a difference in direction of adjustment for different variables in the same subject has been described earlier as polarity, now qualified as intra-individual polarity, to separate it from the precedent of an intrafamilial or more broadly inter-individual polarity or partitioning, reported apparently for the first time and dubbed 'cursion'.     

Effects of supine floating on heart rate,blood pressure and cardiac autonomic nervous system activity

It is known that heart rate, oxygen uptake and body temperature during exercise in water are affected by water temperature, buoyancy and so on. Relaxation in water (supine floating) has been performed in hydrotherapy and aqua exercise. But there were few reports about supine floating (Schulz and Kaspar 1994). The purpose of this study was to make clear the effects of supine floating on heart rate, blood pressure and cardiac autonomic nervous system activity in males.     

Changes in arterial blood pressure, heart rate and haematocrit during acute hyperkalaemia in conscious sheep.

The systolic, diastolic and mean arterial blood pressures, heart rate and haematocrit were measured at 15 minute intervals before, during and after 2 hour infusions of 0-4 mol.l-1 NaCl at 2-2 ml min-1 into conscious intact sheep and 0-4 mol. l-1 KCl at 2-2 ml. min-1 into conscious sheep which were either intact or adrenalectomized. The haemotocrit was also measured in splenectomized sheep receiving 0-4 mol. l-1 KCl. The NaCl infusion had no significant effect on blood pressure(BP), heart rate and haematocrit. Both intact and adrenalectomized sheep were able to withstand an increase in plasma potassium concentration in excess of 50% of the preinfusion concentration before any substantial fall in BP occurred. In intact and adrenalectomized sheep, heart rate and haematocrit increased rapidly and progressively throughout the potassium infusions and at maximum plasma potassium concentration the mean increments in these parameters for both groups of sheep were 21-6+/-2-69 beats/min and 7-5+/-0-47% respectively. Heart rate and haematocrit were more closely correlated with the plasma potassium concentration than with any other variable measured in these experiments. Adrenalectomy did not reduce the ability of the sheep to maintain their BP or to increase their heart rate and haematocrit. As the mean increase in haematocrit during potassium infusion into splenectomized sheep was 1-3+/-0-45% most of the increase in haematocrit observed in the potassium-infused intact and adrenalectomized sheep was caused by ejection of red cells from the spleen into the circulation.     

Measurement of the common carotid arterial flow during parabolic flight in the anesthetized rat]

To measure the blood flow of a common carotid artery (CCA) during parabolic flight in the rat, we developed an animal double hold box (ADHB) made of styrene expanded form for the anesthetized rat to keep the animal at a proper posture in an aircaft. Twelve anesthetized rats weighing 291-342 g were surgically operated to mount a ultrasound flowmeter probe (1 mm size,1RS:Transonic Systems Inc.) around the right CCA and to insert a catheter into the right axillar artery for blood pressure measurement. These animals were held comfortably in ADHBs which were placed on the rack installed in the aircraft (MU-300). A total of 27 parabolic flights was performed and the blood flow was measured accurately in 9 rats. This special animal holding facility is useful for various types of animal experiments in an aircraft.     

Nociceptin/orphanin FQ increases blood pressure and heart rate via sympathetic activation in sheep.

This study was undertaken to examine the cardiovascular effects of nociceptin/Orphanin FQ (OFQ). Nociceptin/OFQ (10-300 nmol/kg, IV) stimulates an increase in mean blood pressure (MBP) and heart rate (HR) in chronically catheterized sheep. Pretreatment with phenoxybenzamine (5 mg/kg) attenuated the pressor response, consistent with sympathetically mediated vasoconstriction. Furthermore, the lack of a reflex bradycardia suggests either blunting of the baroreflex by nociceptin/OFQ or direct beta-adrenergic activation. The bradycardic response to norepinephrine (0.6 microg/kg, IV) remained intact after nociceptin/OFQ administration, demonstrating that nociceptin/OFQ does not blunt the baroreflex. Additionally, the increase in HR was completely reversed by pretreatment with propranolol. These data suggest that nociceptin/OFQ plays a role in cardiovascular regulation via sympathetic activation.     

Short-term and long-term blood pressure and heart rate variability in the mouse

Knowledge on murine blood pressure and heart rate control mechanisms is limited. With the use of a tethering system, mean arterial pressure (MAP) and pulse interval (PI) were continuously recorded for periods up to 3 wk in Swiss mice. The day-to-day variation of MAP and PI was stable from 5 days after surgery. Within each mouse (n = 9), MAP and PI varied by 21+/-6 mm Hg and 17+/-4 ms around their respective 24-h averages (97+/-3 mm Hg and 89+/-3 ms). Over 24-h periods, MAP and PI were bimodally distributed and clustered around two preferential states. Short-term variability of MAP and PI was compared between the resting (control) and active states using spectral analysis. In resting conditions, variability of MAP was mainly confined to frequencies <1 Hz, whereas variability of PI was predominantly linked to the respiration cycle (3-6 Hz). In the active state, MAP power increased in the 0.08- to 3-Hz range, whereas PI power fell in the 0.08- to 0.4-Hz range. In both conditions, coherence between MAP and PI was high at 0.4 Hz with MAP leading the PI fluctuations by 0.3-0.4 s, suggesting that reflex coupling between MAP and PI occurred at the same frequency range as in rats. Short-term variability of MAP and PI was studied after intravenous injection of autonomic blockers. Compared with the resting control state, MAP fell and PI increased after ganglionic blockade with hexamethonium. Comparable responses of MAP were obtained with the alpha-blocker prazosin, whereas the beta-blocker metoprolol increased PI similarly. Muscarinic blockade with atropine did not significantly alter steady-state levels of MAP and PI. Both hexamethonium and prazosin decreased MAP variability in the 0.08- to 1-Hz range. In contrast, after hexamethonium and metoprolol, PI variability increased in the 0.4- to 3-Hz range. Atropine had no effect on MAP fluctuations but decreased those of PI in the 0.08- to 1-Hz range. These data indicate that, in mice, blood pressure and its variability are predominantly under sympathetic control, whereas both vagal and sympathetic nerves control PI variability. Blockade of endogenous nitric oxide formation by N(G)-nitro-L-arginine methyl ester increased MAP variability specifically in the 0.08- to 0.4-Hz range, suggesting a role of nitric oxide in buffering blood pressure fluctuations.     

Methylphenidate increases heart rate,blood pressure and plasma epinephrine in normal subjects

Following an intravenous infusion of methylphenidate (0.3mg/kg) there were significant increases in plasma epinephrine, heart rate, systolic and diastolic pressure, but there was no change in plasma norepinephrine. This pattern of response differs from that seen with D-amphetamine or caffeine.     

树鼩血压和心率的无创测定

目的建立健康树鼩的心率、血压正常值参考范围,并探讨不同来源、不同性别、不同年龄树鼩心率、血压的差异。方法随机挑选实验树鼩180只,按来源分为野生成年组、F1代自繁成年组和青幼年组三个组,每组雌雄各半,共60只。采用智能无创血压计（鼠仪）逐只测定HR（心率）、SBP（收缩压）、DBP（舒张压）和MBP（平均动脉压）。结果野生成年树鼩、自繁成年树鼩和青幼年树鼩心率分别为394.33±37.74 BPM、351.61±72.76 BPM和378.19±69.04 BPM,野生和自繁成年树鼩组差异有显著性（P〈0.05）。自繁成年树鼩收缩压、舒张压和平均动脉压均明显低于青幼年树鼩,差异有极显著性（P〈0.01）。野生成年树鼩和自繁成年树鼩相比,收缩压、舒张压和平均动脉压差异均无显著性（P〉0.05）。结论大鼠无创血压计适合于树鼩的血压、心率的测量。通过测定,获得了野生成年树鼩、F1代自繁成年树鼩和青幼年树鼩的心率和血压参考值范围,丰富了树鼩基础生理数据,可为相关研究提供科学参考。