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Effects of phase delay shifts (PDS) of light in combination with moderately increased salt intake (SL) (2%) or time restriction of food (FR) during the light-time (passive phase) on heart rate (HR), blood pressure (BP) and locomotor activity (LA) in radiotelemetry-measured rats were evaluated. PDS decreased amplitude and spectral power of circadian...

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... Восстановление АД у крыс Wistar и спонтанно гипертензивных крыс происходит через 2 недели после имплантации устройства [45]. В литературе описаны следующие варианты анестезиологического пособия у крыс: внутримышечное введение кетамина и ксилазина в дозе 100 мг/кг и 10 мг/кг соответственно, цефуроксим 20 мг/кг/день, кетопрофен 5 мг/кг/ день [46]; ингаляционная анестезия изофлюраном с использованием следующих параметров: индукция 4 % изофлюраном в смеси с 100 % кислородом, поддерживающая анестезия -1,5-2,0 % изофлюран в смеси с 100 % кислородом [47]; описано использование 5 % изофлюрана для индукции и 3 % изофлюрана для поддерживающей анестезии (бупренорфин 0,005 мг/кг до 48 часов после операции, триметоприм 30 мг/кг в течение семи дней) [48]; медетомидин + мидазолам + фентанил в количестве 0,15 мг/кг -1 + 2,0 мг/кг -1 + 0,005 мг/кг -1 [49]. Для крупных животных целесообразно использовать комбинированный внутривенный и эндотрахеальный наркоз. ...
Article
We report an analysis of published data concerning the measurement of systemic hemodynamic parameters in experiments on laboratory animals. The article highlights the influence of such issues as housing and husbandry, handling, the frequency of person contact, animal surgical modification and pharmacological support in the perioperative period on blood pressure and heart rate, the most frequently recorded parameters both in experiment and clinic. Published data should be taken into account when planning and preparing an experiment using biomedical animal models, as well as when developing and submitting a protocol to the bioethical commission. Assessment of systemic hemodynamics is an integral part of physiological monitoring in any surgery of animals allowing better standardization of experimental endpoints and timely correction of possible deviations.
... However, ALAN did not alter the absolute systolic BP or HR values during the light phase. A misalignment between the internal biological clock and the environment caused a fall in HR [23,34] and deteriorated heart function, including prolongation of PR and QT intervals, in nighttime animals [4]. Changes in the heart result from the altered activity of the autonomic nervous system and are independent of locomotor activity [4]. ...
Article
Aims: Cardiovascular parameters exhibit significant 24-h variability, which is coordinated by the suprachiasmatic nucleus (SCN), and light/dark cycles control SCN activity. We aimed to study the effects of light at night (ALAN; 1-2 lx) on cardiovascular system control in normotensive rats. Main methods: Heart rate (HR) and blood pressure (BP) were measured by telemetry during five weeks of ALAN exposure. From beat-to-beat telemetry data, we evaluated spontaneous baroreflex sensitivity (sBRS). After 2 (A2) and 5 (A5) weeks of ALAN, plasma melatonin concentrations and the response of BP and HR to norepinephrine administration were measured. The expression of endothelial nitric oxide synthase (eNOS) and endothelin-1 was determined in the aorta. Spontaneous exploratory behaviour was evaluated in an open-field test. Key findings: ALAN significantly suppressed the 24-h variability in the HR, BP, and sBRS after A2, although the parameters were partially restored after A5. The daily variability in the BP response to norepinephrine was reduced after A2 and restored after A5. ALAN increased the BP response to norepinephrine compared to the control after A5. Increased eNOS expression was found in arteries after A2 but not A5. Endothelin-1 expression was not affected by ALAN. Plasma melatonin levels were suppressed after A2 and A5. Spontaneous exploratory behaviour was reduced. Significance: ALAN decreased plasma melatonin and the 24-h variability in the haemodynamic parameters and increased the BP response to norepinephrine. A low intensity ALAN can suppress circadian control of the cardiovascular system with negative consequences on the anticipation of a load.
... Repeated phase-delay shifts in the LD cycle did not induce arrhythmicity, but rather substantially decreased the amplitude and suppressed the circadian power of daily rhythms of BP and HR. The results are in line with our previous studies performed in male rats (Molcan et al., 2014(Molcan et al., , 2015. Similarly, in rats exposed weekly to 6-h phase advances in the LD cycle, the rhythms of activity readjusted to the new phase by the end of each shift, and this resynchronization was accelerated following multiple shifts (Yan, 2011). ...
Article
Disturbances in regular circadian oscillations can have negative effects on cardiovascular function, but epidemiological data are inconclusive and new data from animal experiments elucidating critical biological mechanisms are needed. To evaluate the consequences of chronic phase shifts of the light/dark (LD) cycle on hormonal and cardiovascular rhythms, two experiments were performed. In Experiment 1, male rats were exposed to either a regular 12:12 LD cycle (CONT) or rotating 8-h phase-delay shifts of LD every second day (SHIFT) for 10 weeks. During this period, blood pressure (BP) was monitored weekly, and daily rhythms of melatonin, corticosterone, leptin and testosterone were evaluated at the end of the experiment. In Experiment 2, female rats were exposed to the identical shifted LD schedule for 12 weeks, and daily rhythms of BP, heart rate (HR) and locomotor activity were recorded using telemetry. Preserved melatonin rhythms were found in the pineal gland, plasma, heart and kidney of SHIFT rats with damped amplitude in the plasma and heart, suggesting that the central oscillator can adapt to chronic phase-delay shifts. In contrast, daily rhythms of corticosterone, testosterone and leptin were eliminated in SHIFT rats. Exposure to phase shifts did not lead to increased body weight and elevated BP. However, a shifted LD schedule substantially decreased the amplitude and suppressed the circadian power of the daily rhythms of BP and HR, implying weakened circadian control of physiological and behavioural processes. The results demonstrate that endocrine and cardiovascular rhythms can differentially adapt to chronic phase-delay shifts, promoting internal desynchronization between central and peripheral oscillators, which in combination with other negative environmental stimuli may result in negative health effects.
... Recent studies have shown that rapid shifts of LD cycle may prevent entrainment to such light schedules and induce a free-running like pattern of activity rhythm in animals [18] suggesting that SHIFT rats could be tested in different circadian times. However, in our previous study we demonstrated that rats exposed to 8-h phase delay shifts every second day substantially lengthened their period of activity rhythm by about 4 h [25,35], which is out of the range of free-running periods in rats [36] Moreover, clock gene expression in peripheral organs exhibited robust rhythmicity [25,37] indicating that rats were synchronised among each other. Since all behavioural tests were performed during the second half of the light phase on the second day after prolonged dark phase, it is likely that both SHIFT and CTRL rats were tested during their subjective passive phase (Fig. 1, 2). ...
... 25 Spontaneous baroreflex sensitivity (sBRS) was computed as α-index within the LF range ((LF HRV /LF BPV ) 0.5 ). 26 Circadian amplitude (the difference between the peak and the mean value of a wave), acrophase (the time at which the peak of a rhythm occurs) and percentage of rhythmicity (the coefficient of determination; represents the percentage of variation in the data that is explained by the fitted model) of cardiovascular parameters 27,28 were calculated from the original data using Chronos-Fit software. 29 ...
Article
Decreased oxygenation during pregnancy and early periods of ontogeny can affect normal body development and result in diseases in adulthood. The aim of this study was to use the model of prenatal intermittent hypoxia (PIH) and evaluate the effects of short-term hypoxia at the end of gestation on blood pressure (BP) control in adulthood. Wistar rats were exposed daily to PIH for 4 h during gestational day 19 and 20. In adult male rats, heart rate (HR), systolic BP and pulse pressure (PP) were acquired by radiotelemetry during 1 week. On the basis of HR variability and BP variability, sympathovagal balance (LF/HF) and spontaneous baroreflex sensitivity (sBRS) were evaluated. Systolic BP and PP were significantly elevated in PIH rats in comparison with control rats during the light and dark phase of the day, while LF/HF increased only during the light phase of the day. In contrast, sBRS tended to decrease only during the dark phase in PIH rats. In all measured and calculated parameters, significant circadian rhythms were present and were not affected by PIH. In conclusion, our data suggest that short intermittent hypoxia at the end of gestation can increase BP and PP via significant changes in LF/HF, which occur especially during the passive phase of the day. Results suggest that minor changes in the autonomous nervous system activity induced by environmental conditions during the perinatal period may contribute to development of hypertension in adulthood.Hypertension Research advance online publication, 25 February 2016; doi:10.1038/hr.2016.21.
Article
Cardiovascular (CV) health is often expressed by changes in heart rate and blood pressure, the physiological record of which may be affected by moving, anaesthesia, handling, time of day and many other factors in rodents. Telemetry measurement minimises these modulations and enables more accurate physiological recording of heart rate and blood pressure than non-invasive methods. Measurement of arterial blood pressure by telemetry requires implanting a catheter tip into the artery. Telemetry enables us to sample physiological parameters with a high frequency continuously for several months. By measuring the pressure in the artery using telemetry, we can visualize pressure changes over a heart cycle as the pressure wave. From the pressure wave, we can subtract systolic, diastolic, mean and pulse pressure. From the beat-to-beat interval (pressure wave) and the RR' interval (electrocardiogram), we can derive the heart rate. From beat-to-beat variability, we can evaluate the autonomic nervous system's activity and spontaneous baroreflex sensitivity and their impact on CV activity. On a long-term scale, circadian variability of CV parameters is evident. Circadian variability is the result of the circadian system's activity, which synchronises and organises many activities in the body, such as autonomic and reflex modulation of the CV system and its response to load over the day. In the presented review, we aimed to discuss telemetry devices, their types, implantation, set-up, limitations, short-term and long-term variability of heart rate and blood pressure in CV research. Data collection by telemetry should be, despite some limitations, standard in modern experimental CV research.
Article
New findings: What is the central question of this study? Artificial light at night decreases blood pressure and heart rate in rats. Are mentioned changes in heart rate accompanied by changes in protein expression in the heart's left ventricle? What is the main finding and its importance? For the first time, we reported that five weeks of artificial light at night affected protein expression in the heart's left ventricle in normotensive and hypertensive rats. Artificial light at night decreased expression of the sarco/endoplasmic reticulum Ca2+ -ATPase, angiotensin II receptor type 1, and endothelin-1. Abstract: Artificial light at night (ALAN) affects the circadian rhythm of the heart rate in normotensive Wistar (WT) and spontaneously hypertensive rats (SHR) through the autonomic nervous system, which regulates the heart's activity through calcium handling, an important regulator in heart contractility. We analysed the expression of the sarco/endoplasmic reticulum Ca2+ -ATPase (SERCA2) and other selected regulatory proteins involved in the regulation of heart contractility, angiotensin II receptor type 1 (AT1 R), endothelin-1 (ET-1) and tyrosine hydroxylase (TH) in the left ventricle of the heart in WT and SHR after two and five weeks of ALAN with intensity 1-2 lx. Expression of SERCA2 was decreased in WT (control: 0.53 ± 0.07; ALAN: 0.46 ± 0.10) and SHR (control: 0.72 ± 0.18; ALAN: 0.56 ± 0.21) after five weeks of ALAN (p = 0.067). Expression of AT1 R was significantly decreased in WT (control: 0.51 ± 0.27; ALAN: 0.34 ± 0.20) and SHR (control: 0.38 ± 0.07; ALAN: 0.23 ± 0.09) after two weeks of ALAN (p = 0.028) and in SHR after five weeks of ALAN. Expression of ET-1 was decreased in WT (control: 0.51 ± 0.27; ALAN: 0.28 ± 0.12) and SHR (control: 0.54 ± 0.10; ALAN: 0.35 ± 0.23) after five weeks of ALAN (p = 0.015). ALAN did not affect the expression of TH in WT or SHR. In conclusion, ALAN suppressed the expression of SERCA2, AT1 R and ET-1, which are important for the regulation of heart contractility, in a strain-dependent pattern in both WT and SHR. This article is protected by copyright. All rights reserved.
Article
Birds developed endothermy and four-chambered high-performance heart independently from mammals. Though avian embryos are extensively studied and widely used as various models for heart research, little is known about cardiac physiology of adult birds. Meanwhile, cardiac electrophysiology is in search for easily accessible and relevant model objects which resemble human myocardium in the pattern of repolarizing currents (IKr, IKs, IKur and Ito). This study focuses on the configuration of electrical activity and electrophysiological phenotype of working myocardium in adult Japanese quails (Coturnix japonica). The resting membrane potential and action potential (AP) waveform in quail atrial myocardium were similar to that in working myocardium of rodents. Using whole-cell patch clamp and sharp glass microelectrodes, we demonstrated that the repolarization of quail atrial and ventricular myocardium is determined by voltage-dependent potassium currents IKr, IKs and Ito – the later was previously considered as an exclusive evolutionary feature of mammals. The specific blockers of these currents, dofetilide (3 μmol l⁻¹), HMR 1556 (30 μmol l⁻¹) and 4-aminopyridine (3 mmol l⁻¹), prolonged AP in both ventricular and atrial myocardial preparations. The expression of the corresponding channels responsible for these currents, in quail myocardium was investigated with quantitative RT-PCR and western blotting. In conclusion, the described pattern of repolarizing ionic currents and channels in quail myocardium makes this species a novel and suitable experimental model for translational cardiac research and reveals new information related to the evolution of cardiac electrophysiology in vertebrates.
Article
Physiological variables such as heart rate (HR) and blood pressure (BP) exhibit long-term circadian rhythms, which can be disturbed by shift work. On the other hand, short-term oscillations in HR and BP have a high prognostic value. Therefore, we aimed to determine if the short-term variability, complexity and entropy of HR and BP would be affected by a regular light/dark (LD) cycle and phase delay shifts of the LD cycle, leading to chronodisruption. Telemetry-monitored rats were exposed first to the regular LD cycle and then to shifts in LD for 8 weeks. On the basis of long-term HR and BP recording and evaluation, we found circadian rhythms in HR and BP variability, complexity and entropy under regular LD cycles. Short-term exposure to shifts disturbed circadian rhythms of HR and BP variability, complexity and entropy, indicating chronodisruption. The power of circadian rhythms was suppressed after 8 weeks of phase delay shifts. Long-term exposure to shifts increased variability (p = 0.007), complexity (p < 0.001) and dark-time entropy (p = 0.006) of HR but not BP. This is the first study demonstrating long-term recording and estimation of HR and BP variability, complexity and entropy in conscious rats exposed to irregular lighting conditions. After long-term phase delay shifts, short-term variability of HR was less predictable than in controls. This study suggests that changes in short-term HR and BP oscillations induced by long-term shift work can negatively affect cardiovascular health.