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The daily (A), (B), (C) and weekly (D), (E), (F) pattern of HR (A), (D), mean arterial BP (B), (E) and locomotor activity (C), (F) in rats (n = 6) exposed for 1 week to control 12L:12D conditions and for 12 weeks (S01, S05, S10, S11) to PAS three times per week. The dark solid lines (A), (B), (C) and dark bars (D), (E), (F) represent the dark phase mean values and the dotted lines (A), (B), (C) and gray bars (D), (E), (F) represent the light phase mean values. Columns with superscripts are statistically different. Error bars indicate s.e.m.
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Cardiovascular parameters, such as blood pressure and heart rate, exhibit both circadian and ultradian rhythms which are important for the adequate functioning of the system. For a better understanding of possible negative effects of chronodisruption on the cardiovascular system we studied circadian and ultradian rhythms of blood pressure and heart...
Citations
... In contrast with a decrease in 24-h variability, we observed an increase in ultradian oscillations after ALAN exposure. Elevated power of ultradian oscillations of several physiological parameters, such as systolic blood pressure, heart rate and sleep characteristics, was recorded in different models of circadian disruption, such as shift work, constant light and jet lag [31][32][33]. Ultradian oscillations in the energy metabolisms became more pronounced after SCN lesions and the deletion of clock genes [34][35][36][37]. ...
Artificial light at night (ALAN) disrupts 24-h variability of blood pressure, but the molecular mechanisms underlying these effects are unknown. Therefore, we analysed the daily variability of pulse pressure, the maximum value of acceleration rate of aortic pressure (dP/dt(max)) measured by telemetry and protein expression in the thoracic aorta of normotensive male rats exposed to ALAN (1-2 lx) for 3 weeks. Daily, 24-h variability of pulse pressure and dP/dt(max) was observed during a regular light/dark regimen with higher values during the dark compared to the light phase of the day. ALAN suppressed 24-h variability and enhanced ultradian (<12-h) periods of pulse pressure and dP/dt(max) in duration-dependent manners. From beat-to-beat blood pressure variability, ALAN decreased low-frequency bands (a sympathetic marker) and had minimal effects on high-frequency bands. At the molecular level, ALAN decreased angiotensin II receptor type 1 expression and reduced 24-h variability. ALAN caused the appearance of 12-h oscillations in transforming growth factor β1 and fibulin 4. Expression of sarco/endoplasmic reticulum Ca2+-ATPase type 2 was increased in the middle of the light and dark phase of the day, and ALAN did not affect its daily and 12-h variability. In conclusion, ALAN suppressed 24-h variability of pulse pressure and dP/dt(max), decreased the power of low-frequency bands and differentially affected the expression of specific proteins in the rat thoracic aorta. Suppressed 24-h oscillations by ALAN underline the pulsatility of individual endocrine axes with different periods, disrupting the cardiovascular control of central blood pressure.
... However, HR exhibits circadian fluctuations, and values measured at specific times of the day should reasonably be accepted. The reason for such an approach is the fact that telemetry studies in awake rats indicate the existence of a circadian rhythm in HR, not only in males (Hashimoto et al., 1999(Hashimoto et al., , 2001Koresh et al., 2016;Molcan et al., 2013Molcan et al., , 2014Wessel et al., 2007) but also in females (Koresh et al., 2016;Schlatter & Zbinden, 1982). Therefore, in this regard, the use of the HRV method can be an effective and non-invasive tool for the assessment of autonomic control of the heart, as well as autonomic modulation of HR (Akselrod, 1988;Lunqvist, 1990;Malik & Camm, 1993;Mansier et al., 1996), for which changes are a useful indicator of tendencies F I G U R E 1 Graphical representation of sex differences in individual heart rate variability (HRV) parameters depending on the light-dark (LD) cycle in rats under zoletil anaesthesia. ...
Heart rate variability (HRV) is commonly used in experimental studies to assess sympathetic and parasympathetic activities. The belief that HRV in rodents reflects similar cardiovascular regulations in humans is supported by evidence, and HRV in rats appears to be at least analogous to that in humans, although the degree of influence of the parasympathetic division of the autonomic nervous system (ANS) may be greater in rats than in humans. Experimental studies are based on control or baseline values, on the basis of which the change in ANS activity after a given experimental intervention is assessed, but it is known that the ANS in rats is very sensitive to various stress interventions, such as the manipulation itself, and ANS activity can also differ depending on sex, the time of measurement, and whether the animals are under general anaesthesia. Thus, for correct assessment, changes in ANS activity and their relationship to the observed parameter should be based on whether ANS activity does or does not change but also to what extent the activity is already changed at the start of the experiment. Since rats are considered to be the most suitable model animal for basic cardiovascular research, in this review we point out existing differences in individual HRV frequency parameters at the start of experiments (control, baseline values), taking into account sex in relation to time of measurement and anaesthesia.
... Our results, therefore, indicate that in zoletil-anesthetized rats, LD differences were maintained only in males but not in females. Considering the results of telemetry studies by Molcan et al. [50,51], heart rate exhibits a significant circadian rhythm in non-anesthetized rats, in which the heart rate in the dark period fluctuated from 347 beats/min to 363 beats/min, and from 309 beats/min to 321 beats/min in the light period. Thus, it appears that although zoletil exerts a tachycardic effect, [7,30,31]; pent -Pentobarbital (161.1(156.1-165.7), ...
The aim was to evaluate the current state of the autonomic nervous system (ANS) activity under general anesthesia using heart rate variability (HRV) in dependence on the light-dark (LD) cycle in healthy, sexually mature, spontaneously breathing, zoletil-anesthetized (30 mg/kg) Wistar rats of both sexes after a 4-week adaptation to an LD cycle (12 h:12 h). The animals were divided into four experimental groups according to sex and light period (n = 20 each). RR interval duration, spectral power at very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF), total spectral power of HRV, and the LF/HF ratio were analyzed. Sympathetic and baroreceptor activity was decreased, and parasympathetic activity was increased in both sexes and in both light periods. Regarding sex differences, HRV was significantly lower in females versus males in the light period. In the dark period, females exhibited higher HRV than males. Regarding LD differences, in females, HRV was lower in the light versus the dark period, unlike males, in which HRV was higher in the dark versus the light period of the rat regimen day. Sex differences in the activity of the ANS were apparent in rats, persisted under general anesthesia, and were dependent on the LD cycle.
... Baseline HR analysis from telemetry studies involving non-anesthetized rats, in which a chronobiological approach was applied, indicates that there is a circadian rhythm in HR in rats, with a higher HR during the active (i.e., dark) period of the regimen day, not only in males [10][11][12][13][14] but also in females [12,15]. If HR exhibits circadian fluctuations, then when exactly HR is evaluated can be problematic. ...
In in vivo cardiovascular or toxicological studies involving rat models, changes in selected electrocardiographic (ECG) parameters are monitored after various interventions to assess the origin and development of heart rhythm disorders. Each ECG parameter has diagnostic significance; as such, commonly evaluated ECG parameters, including heart rate, PR interval, P wave duration, P wave amplitude, QRS complex, QT and QTc interval duration, R wave and T wave amplitude, of rats under various types of general anesthesia were the focus of this study. Studies that performed in vivo cardiovascular or toxicological experiments in rats were retrieved from a search of the Web of Science database for articles published mainly between 2000 and 2021. In total, the search retrieved 123 articles. ECG parameters that were reported as baseline or control values were summarized and averages with ranges were calculated. It is important to be cautious when interpreting results and, in discussions addressing the mechanisms underlying a given type of arrhythmia, acknowledge that initial ECG parameters may already be affected to some extent by the general anesthesia as well as by sex and the time of day the experiments were performed.
... Because HR in non-anesthetized rats exhibits circadian variation; in the dark period, it varies from 347 to 363 beats/min and, in the light period from 309 to 321 beats/min. Molcan et al. [5] reported that recorded HR was increased in both sexes and in both light periods. In females, LD differences were eliminated (possibly modified) and, in males, LD differences were preserved. ...
Introduction: The primary objective of this study was to determine the impact of spectral powers of heart rate variability (HRV) on changes in heart rate (HR),
total spectral power of HRV, and low-frequency (LF)/high-frequncy (HF) ratio in healthy, sexually mature rats of both sexes spontaneously breathing under zoletil
anesthesia in the light (inactive) and the dark (active) period of their regimen day.
Material and methods: Experiments were performed using male and female zoletil-anesthetized (30 mg/kg [intraperitoneal]) Wistar rats after a four-week adaptation
to a light-dark (LD) cycle (12h:12h). The animals were divided into four experimental groups (n=20 each) according to sex and light period. HR, spectral powers of
HRV (very low frequency, LF, and HF), as well as LF/HF ratio were evaluated 20 min after administration of anesthesia.
Results and conclusions: Zoletil exerted a tachycardic effect in both sexes and in both light periods of the regimen day. In females, the autonomic nervous system
was involved in HR changes in both light periods, while in males, HR exhibited no dependence on autonomic nervous system activity; as such, the authors speculate
that it was predominantly determined by other factors. In females, HRV was determined by sympathetic and baroreflex activity in both light periods, while in males,
HRV was determined by parasympathetic activity. LF significantly influenced LF/HF ratio in females, but not in males, while the effect of HF on the LF/HF ratio
was negligible in both sexes and in both light periods.
... Our results, therefore, indicate that in zoletil-anesthetized rats, LD differences were maintained only in males but not in females. Considering the results of telemetric studies by Molcan et al. [19,20], heart rate exhibits a significant circadian rhythm in non-anesthetized rats, in which the heart rate in the dark period fluctuates from 347 beats/min to 363 beats/min, and from 309 beats/min to 321 beats/min in the light period. Thus, it appears that although zoletil exerts a tachycardic effect, it can eliminate-or, at least modify-circadian rhythm of heart rate, but only in females. ...
Background: It is known that general anesthesia weakens autonomic function and baroreflex control. Intravenous anesthetics may have different qualitative and quantitative effects on the peripheral autonomic nervous system (ANS) and, can thus, alter the activity of sympathetic or parasympathetic divisions of the ANS. Presently, there are relatively little data regarding sex differences in ANS activity or sex differences in ANS activities during anesthesia. The primary goal of the present study was to assess sex differences in ANS activity in dependence on the light-dark (LD) cycle in healthy, sexually mature, spontaneously breathing zoletil-anesthetized rats.
... Our results, therefore, indicate that in zoletil-anesthetized rats, LD differences were maintained only in males but not in females. Considering the results of telemetric studies by Molcan et al. [19,20], heart rate exhibits a significant circadian rhythm in non-anesthetized rats, in which the heart rate in the dark period fluctuates from 347 beats/min to 363 beats/min, and from 309 beats/min to 321 beats/min in the light period. Thus, it appears that although zoletil exerts a tachycardic effect, it can eliminate-or, at least modify-circadian rhythm of heart rate, but only in females. ...
Background: It is known that general anesthesia weakens autonomic function and baroreflex control. Intravenous anesthetics may have different qualitative and quantitative effects on the peripheral autonomic nervous system (ANS) and, can thus, alter the activity of sympathetic or parasympathetic divisions of the ANS. Presently, there are relatively little data regarding sex differences in ANS activity or sex differences in ANS activities during anesthesia. The primary goal of the present study was to assess sex differences in ANS activity in dependence on the light-dark (LD) cycle in healthy, sexually mature, spontaneously breathing zoletil-anesthetized rats.
... Because HR in non-anesthetized rats exhibits circadian variation; in the dark period, it varies from 347 to 363 beats/min and, in the light period from 309 to 321 beats/min. Molcan et al. [9] reported that recorded HR was increased in both sexes and in both light periods. In females, LD differences were eliminated (possibly modified) and, in males, LD differences were preserved. ...
Objectives: It is known that general anesthesia weakens autonomic function and baroreflex control. Intravenous anesthetics may have different qualitative and quantitative effects on the peripheral autonomic nervous system (ANS) and, can thus, alter the activity of sympathetic or parasympathetic divisions of the ANS. Presently, there are relatively little data regarding sex differences in ANS activity or sex differences in ANS activities during anesthesia. Aims: The primary objective of this study was to determine the impact of spectral powers of heart rate variability (HRV) on changes in heart rate (HR), total spectral power of HRV, and low-frequency (LF)/high-frequncy (HF) ratio in healthy, sexually mature rats of both sexes spontaneously breathing under zoletil anesthesia in the light (inactive) and the dark (active) period of their regimen day. Materials and Methods: Experiments were performed using male and female zoletil-anesthetized (30 mg/kg [intraperitoneal]) Wistar rats after a four-week adaptation to a light-dark (LD) cycle (12h:12h). The animals were divided into four experimental groups (n=20 each) according to sex and light period. HR, spectral powers of HRV (very low frequency, LF, and HF), as well as LF/HF ratio were evaluated 20 min after administration of anesthesia. Results and Conclusions: Zoletil exerted a tachycardic effect in both sexes and in both light periods of the regimen day. In females, the autonomic nervous system was involved in HR changes in both light periods, while in males, HR exhibited no dependence on autonomic nervous system activity; as such, the authors speculate that it was predominantly determined by other factors. In females, HRV was determined by sympathetic and baroreflex activity in both light periods, while in males, HRV was determined by parasympathetic activity. LF significantly influenced LF/HF ratio in females, but not in males, while the effect of HF on the LF/HF ratio was negligible in both sexes and in both light periods.
... Our results, therefore, indicate that in zoletil-anesthetized rats, LD differences were maintained only in males but not in females. Considering the results of telemetry studies by Molcan et al. [50,51], heart rate exhibits a significant circadian rhythm in non-anesthetized rats, in which the heart rate in the dark period fluctuated from 347 beats/min to 363 beats/min, and from 309 beats/min to 321 beats/min in the light period. Thus, it appears that although zoletil exerts a tachycardic effect, [7,30,31]; pent -Pentobarbital (161.1(156.1-165.7), ...
The aim was to evaluate the current state of the autonomic nervous system (ANS) activity under general anesthesia using heart rate variability (HRV) in dependence on the light-dark (LD) cycle in healthy, sexually mature, spontaneously breathing, zoletil-anesthetized (30 mg/kg) Wistar rats of both sexes after a 4-week adaptation to an LD cycle (12 h:12 h). The animals were divided into four experimental groups according to sex and light period (n = 20 each). RR interval duration, spectral power at very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF), total spectral power of HRV, and the LF/HF ratio were analyzed. Sympathetic and baroreceptor activity was decreased, and parasympathetic activity was increased in both sexes and in both light periods. Regarding sex differences, HRV was significantly lower in females versus males in the light period. In the dark period, females exhibited higher HRV than males. Regarding LD differences, in females, HRV was lower in the light versus the dark period, unlike males, in which HRV was higher in the dark versus the light period of the rat regimen day. Sex differences in the activity of the ANS were apparent in rats, persisted under general anesthesia, and were dependent on the LD cycle.
... Light pollutions and continuous light associated with melatonin deficiency disturb circadian rhythm [1,2], and constant light hampers pineal gland function and abolishes approximately 90% of nocturnal melatonin production [3]. In addition, circadian disorders are deleterious to the heart and may enhance susceptibility to cardiac arrhythmias [4,5]. ...
... Light pollution associated with circadian rhythm disorders affects cardiac rhythm and can increase susceptibility to arrhythmias [4,5]. Findings herein indicate that both normotensive and hypertensive rats' exposure to continuous light for 6 weeks resulted in significant reduction in electrical threshold to induce VF (Figure 1) compared to standard light conditions. ...
Light pollution disturbs circadian rhythm, and this can also be deleterious to the heart by increased susceptibility to arrhythmias. Herein, we investigated if rats exposed to continuous light had altered myocardial gene transcripts and/or protein expression which affects arrhythmogenesis. We then assessed if Omacor® supplementation benefitted affected rats. Male and female spontaneously hypertensive (SHR) and normotensive Wistar rats (WR) were housed under standard 12 h/12 h light/dark cycles or exposed to 6-weeks continuous 300 lux light for 24 h. Half the rats were then treated with 200 mg/100 g b.w. Omacor®. Continuous light resulted in higher male rat vulnerability to malignant ventricular fibrillation (VF). This was linked with myocardial connexin-43 (Cx43) down-regulation and deteriorated intercellular electrical coupling, due in part to increased pro-inflammatory NF-κB and iNOS transcripts and decreased sarcoplasmic reticulum Ca2+ATPase transcripts. Omacor® treatment increased the electrical threshold to induce the VF linked with amelioration of myocardial Cx43 mRNA and Cx43 protein levels and the suppression of NF-κB and iNOS. This indicates that rat exposure to continuous light results in deleterious cardiac alterations jeopardizing intercellular Cx43 channel-mediated electrical communication, thereby increasing the risk of malignant arrhythmias. The adverse effects were attenuated by treatment with Omacor®, thus supporting its potential benefit and the relevance of monitoring omega-3 index in human populations at risk.
