Effects of low ethanol doses on heart rhythm in rabbits

Effects of low ethanol doses on the vagosympathetic mechanisms of heart rhythm regulation were studied in rabbits. Analysis of heart rhythm variability showed that single intragastric administration of 0.5 mg/kg ethanol caused tachycardia in animals with initial predominance of vagal activity and bradycardia in animals with predominating sympathetic mechanisms. This was associated with general activation of all regulatory effects on the heart rhythm and a drastic increase in power spectrum for all frequency ranges, though with a certain deficiency of vagal effects. However, after 24 h the vagal component of the spectrum drastically increased in animals of both groups, while other parameters did not differ from the control. Presumably, this rebound can be used as a physiological marker, ethanol tolerance measure, formation of the abstinence syndrome and liability to alcoholism. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 9, pp. 306–310, September, 2004     

Parasympathetic cardiac effects in sympathectomized rats

In adult sympathectomized rats the right and left vagus nerves exhibited asymmetric effects on heart rate and strength of cardiac contractions. After vagotomy, the heart rate and stroke volume remained high in sympathectomized rats, but returned to normal in intact animals. The sympathetic nervous system plays a role in postvagotomic tachycardia. Sympathectomized rats were characterized by higher reactivity of cardiac β-adrenoceptors to propranolol compared to intact animals. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 8, pp. 131–134, August, 2007     

Heart Rate Variability in Outbred White Rats upon Periodical α-Tocopherol Administration

Effect of α-tocopherol (vitamin E) periodical administration on heart rhythm regulation was investigated in outbred white rats. α-Tocopherol administration to males was followed by reduction of sympathetic neural influence on heart rhythm and also by the increase of the number of individuals with high activity of autonomic regulation loop. In female rats α-tocopherol administration modulates the activity of humoral control circuit and promotes heart rate reduction, however upon that the percent of females with high centralization of heart rate regulation was increased. Translated from Byulleten’ Experimental’noi Biologii i Meditsiny, Vol. 147, No 2, pp. 130–133, February, 2009     

Effect of β-adrenoceptor blockers on growth of neurites in spinal ganglia in organotypic tissue culture

We studied the effects of norepinephrine and β₁-adrenoblockers atenolol and metoprolol on the growth of neuritis in organotypic tissue culture of spinal ganglia from 10–12-day chicken embryos. Atenolol (10⁻⁴ M) accelerated the growth of neurites in spinal ganglia by 45%, while metoprolol inhibited the growth of the explants almost in all examined concentrations (10⁻¹⁰–10⁻⁴ M). Thus, β₁-adrenoblockers can produce opposite effects on neurite growth. Both atenolol and metoprolol abolished the neurite-stimulating effect of norepinephrine, probably, because this effect is mediated via β₁-adrenoreceptors of spinal ganglia. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 5, pp. 487–489, May, 2007.     

Heart Rate Variability in Rats with Experimental Chronic Heart Failure and Long-Term Exposure to β-Adrenoblockers

Simulation of chronic heart failure in rats led to an increase in heart rate variability and decrease in heart rate. All β-blockers also promoted the heart rate variability augmentation in ill animals. The most potent effects on heart rate variability were produced by pindolol, atenolol, and propranolol. Bisoprolol and metoprolol affected heart rate and heart rate variability in less extent, and nebivolol normalized a part of heart rate variability parameters. Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 147, No. 2, pp. 139–143, February, 2009     

Role of Sympathetic and Parasympathetic Nervous Systems in Heart Rate Regulation in Cats

The effects of atropine and β-adrenoceptor blockers on mean HR, wave structure of the cardiac rhythm, and chronotropic reaction to noise stress were examined in cats. Atropine (0.5 mg/kg) increased the mean HR and significantly decreased the spectrum power of HF, LF, and VLF oscillations. The decrease in HF power was most pronounced, which enhanced LF/HF ratio. Propranolol (0.5 mg/kg) decreased the mean HR and slightly increased the power of HF, LF, and VLF oscillations. Atenolol (2 mg/kg) exerted similar but more pronounced effects. β-Adrenoceptor blockers increased HF power to a greater extent than LF and VLF power, which led to a decrease in LF/HF ratio. Atropine markedly decreased the chronotropic reaction to stress. β-Adrenoceptor blockers produced no effect on the amplitude of this reaction, but accelerated restoration of initial HR. It is established that the changes in power spectrum of HR and the phase reflex reactions in cats are mediated by parasympathetic influences; the sympathetic system is involved only in the control of mean HR, probably in response to the level of animal activity. The changes in LF/HF ratio during blockade of sympathetic and parasympathetic systems are caused by opposite influences of these systems on HF oscillations, but not by hypothetic “sympathetic” and “parasympathetic” nature of LF and HF oscillations of the heart rhythm. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 11, pp. 484–489, November, 2005     

Effect of β-adrenoblockers on heart rate variability in awake and narcotized rats

In narcotized rats, β-adrenoceptor blockers changed all parameters of heart rate variability indicating up-regulation of parasympathetic activity and down-regulation of the sympathetic one. In immobilized awake rats, the temporal and geometrical parameters varied similarly, while spectral analysis indicated possible activation of other neurohumoral mechanisms against the background of β-blocker treatment. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 10, pp. 372–264, October, 2007     

Treatment of acute coronary syndromes in patients with type 2 diabetes mellitus with β-adrenoblockers and angiotensin-converting enzyme inhibitors: Cardiohemodynamic effects and impact for prognosis

Long-term oral treatment of patients with acute coronary syndromes and type 2 diabetes mellitus with β-adrenoblockers and angiotensin-converting enzyme inhibitors is associated with positive, though ambiguous changes in the left-ventricular structure and function. These changes should be the reason for choosing optimal therapy ensuring better prognosis in this patient population. Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 138, No. 9, pp. 341–344, September, 2004     

Role of Purinoceptors in Cardiac Function in Rats during Ontogeny

Intravenous injection of exogenous ATP (10⁻⁴ M) to rats aging 21, 56, and 100 days increased the heart rate by the 15th sec postinjection. Stable ATP analogue α,β-methylene-ATP in an equimolar concentration increased the heart rate in rats aging 56 and 100 days (by the 15th second after treatment), but had no effect on 21-day-old animals. α,β-Methylene-ATP in a concentration of 10⁻⁷ M increased the heart rate in 21-day-old rat pups, which attests to high sensitivity of P2 purinoceptors. Administration of ATP and α,β-methylene-ATP after treatment with nonselective purinoceptor antagonist suramin did not increase the heart rate in rats of different age groups. Infusion of ATP and its stable analogue after administration of selective P2Y receptor antagonist reactive blue 2 increased the heart rate in rats of different age groups. These changes reflect activation of P2X receptors in the heart. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 11, pp. 490–492, November, 2005     

Circadian rhythm changes in heart rate variability during chronic sound stress

To study the circadian rhythm changes of the heart rate variability (HRV) during chronic sound stress, Wistar rats were implanted with telemetry transmitters and exposed to chronic ultrasound stress for 14 days. The heart rate, mean R-R intervals (mean R-R) and body temperature were monitored hourly. The spectra of five-minute heart rate variability were plotted on a log-log scale of frequency versus power spectral density, and the spectral exponent β of the regression line of this plot was calculated. The exponent β, heart rate (HR) and body temperature recorded hourly were plotted and fitted to sine curves to observe the circadian rhythm of these parameters. The correlation coefficient of the fitted sine curves in β decreased from 0.644 in the control period to 0.105 in the stress period, indicating that the rhythm of β deceased during stress. This did not occur in the other two parameters, demonstrating that the HRV exponent can assess chronic stress.     

Survival of rats with experimental chronic heart failure depending on pharmacodynamic and pharmacokinetic parameters of angiotensin-converting enzyme inhibitors and β-adrenoceptor blockers

Lipophilic inhibitors of angiotensin-converting enzyme increased 6-month survival and/or lifetime of rats with experimental chronic heart failure. These drugs had no effect on the mortality rate of animals with acute decompensation of the disease. β-Adrenoceptor blockers without intrinsic sympathomimetic activity not only prolonged 6-month survival and lifetime, but also decreased the mortality rate of rats with decompensation of chronic heart failure. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 1, pp. 45–48, January, 2006     

Theta driving both inhibits and potentiates the effects of nicotine on dentate gyrus responses

The medial septal area of conscious rats was stimulated through previously implanted electrodes at a frequency of 7.7 Hz for 20 min each day for 7 days to evoke rhythmic slow activity in CA1 at a similar frequency to spontaneous theta. Two weeks later in the anaesthetized rats the effects of a single subcutaneous injection of nicotine (0.4 mg/kg) on fEPSPs, evoked in the dentate gyrus by separate stimulation of the MPP and LPP, were studied and compared with those obtained in controls. Nicotine increased the firing of locus coeruleus neurons and the slope of the fEPSPs evoked by LPP stimulation, but not by MPP stimulation. Prior theta driving considerably increased the effect of nicotine on the responses evoked by stimulation of the MPP and abolished the nicotine-induced potentiation of the responses evoked by stimulation of the LPP. The results are attributed to theta driving increasing the amount of noradrenaline released by nicotine and to noradrenaline producing a β-adrenoceptor long-lasting potentiation at the medial perforant path synapse and a long-lasting depression at the lateral perforant path synapse. Published in Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 56, No. 2, pp. 257–263, March–April, 2006.     

Effect of hypoxia of increasing severity on the dynamics of cerebral cortex EEGs in rats with different resistance to acute oxygen deficiency

EEGs recorded from the cerebral cortex of rats with high and low resistance to hypoxia during “elevation” in a pressure chamber differ in the dynamics of the EEG power spectra. EEGs of highly resistant rats show phasic changes in biopotentials correlating with the severity of hypoxia: primary increase in the absolute power of all frequency ranges is followed by normalization and a secondary increase with predominance of the slow-wave component, inhibition of the β₂ range and the emergence of interhemispheric differences, and terminal inhibition of the power of all frequency ranges. In rats with low resistance to hypoxia, phases of relative normalization of EEG spectra and their depression during terminal period are not observed, all changes being represented by a continuous increase in the power of the α and δ ranges with progressive inhibition of the β₂ range and then of the β₁ range. Interhemispheric asymmetry is significant throughout the period of power increase. A high amplitude burst activity is recorded in rats of both types starting from an altitude of 8000 or 9000 m. The pattern of EEG changes in rats exposed to hypoxia of growing severity consistently reproduces those observed in patients with ischemic stroke. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 9, pp. 262–267, September, 1996     

Sex-related differences in the variability of vascular blood flow in middle-age individuals

Analysis of spectral parameters of vascular blood flow variability revealed some sex-related peculiarities. The amplitude of aortic pulsation and total variability power of this parameter and its four components (ultralow frequency, very low frequency, low frequency, and high frequency range) were higher in women. The amplitude of microvascular pulsation and total variability power of this parameter and components were higher in men. In male patients, the relative variability power for the amplitude of microvascular pulsation was higher in the high frequency and low frequency ranges, but lower in the very low frequency and ultralow frequency ranges. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 145, No. 4, pp. 399–401, April, 2008     

Frequency-domain analysis of cerebral autoregulation from spontaneous fluctuations in arterial blood pressure

The dynamic relationship between spontaneous fluctuations of arterial blood pressure (ABP) and corresponding changes in crebral blood flow velocity (CBFV) is studied in a population of 83 neonates. Static and dynamic methods are used to identify two subgroups showing either normal (group A, n=23) or impaired (group B, n=21) cerebral autoregulation. An FFT algorithm is used to estimate the coherence and transfer function between CBFV and ABP. The significance of the linear dependence between these two variables in demonstrated by mean values of squared coherence >0.50 for both groups in the frequency range 0.02–0.50 Hz. However, group A has significanlty smaller coherences than group B in the frequency ranges 0.02–0.10 Hz and 0.33–0.49 Hz. The phase response of group A is also significantly more positive than that of group B, with slopes of 9.3±1.05 and 1.80±1.2 rad Hz⁻¹, respectively. The amplitude frequency response is also significantly smaller for group A in relation to group B for the frequency range 0.25–0.43 Hz. These results suggest that transfer function analysis may be able to identify different components of cerebral autoregulation and also provide a deeper understanding of recent findings by other investigators.     

EEG frequency ranges during perception and mental rotation of two-and three-dimensional objects

Spectral EEG powers were compared in 4 frequency ranges (8–13, 15–25, 25–35, and 35–45 Hz) in a group of 20 subjects during the performance of tasks requiring mental rotation of two-and three-dimensional objects. Only those EEG segments corresponding to tasks with identical solution times were analyzed. The spectral powers of oscillations in the alpha range were higher in control conditions than during task performance. Power in the frequency range 15–45 Hz was greater during task performance than in control conditions; this supports the concept that alpha rhythm desynchronization accompanies the synchronization of higher frequency EEG rhythms. Frequency power during task performance with two-dimensional objects was greater than that during tasks with three-dimensional objects. Since the angle of rotation between two-dimensional objects was greater than that between three-dimensional objects, this factor, rather than the depth of the perceived space, increased the level of cortical activation. In all experimental situations, power at frequencies of 15–45 Hz was significantly greater in the occipital regions than any other regions, reflecting the visual modality of the stimulus. Particular changes were noted in the gamma range (35–45 Hz), where power in the first second of task performance was significantly higher than in the second second; this may provide evidence that this range is more closely associated with perception and recognition processes than with mental transformation of the image. Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences. Institute of Humans, Russian Academy of Sciences, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 47, No. 5, pp. 908–917, September–October, 1997.     

Cluster Analysis of Extracardiac Control of the Heart Rate in Random-Bred Albino Rats at Rest

Heart rate variability was examined in random-bred albino rats at rest. The rats were clusterized according to activity of autonomic contour of heart rate control. Combination of factor and cluster analyses enhanced informative value of spectrum parameters of the heart rate variability in nonlinear rats grouped by initial neurovegetative status. The contours of central and autonomic regulation describe the most general features of the control influences that realize modulating influences at the heart level via sympathetic and parasympathetic control pathways. Their activity is comprehensively assessed by the normalized power spectrum of variations in the heart rate. Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 147, No. 1, pp. 16–19, January, 2009     

Heart rate variability as an index of autonomic imbalance in patients with recent myocardial infarction

Autonomic nervous activities are estimated in three groups of patients; Group A consists of patients who had experienced myocardial infarction (MI) within 2–6 weeks before the tests; Group B consists of patients who had MI more than one year previously; Group C consists of matched controls, free of cardiac disease. Autonomic activity is estimated using postural effects on heart rate variability (HRV): a sympathetic activity index is defined as HRV power within a low frequency band (0·04–0·12 Hz) in the tilt position and a parasympathetic activity index is defined as HRV power in a high frequency band (0·18–0·28 Hz) in the supine position. Results show that, relative to controls, Group A patients have reduced parasympathetic activity index (5+3 against 13+8, normalised units; p<0·05) and an increased ratio of sympathetic to parasympathetic activity (17+17 against 4+2; p<0·05). Group B is not significantly different from Group A or C. The period of 2–6 weeks post-MI thus appears to be characterised by depressed parasympathetic nervous activity which can be measured using HRV analysis.     

Effect of new anxiolytic CM-346 on bioelectrical activity of cerebral cortex in MR and MNRA rats

The effect of 2-[2-(morpholin)ethylthio]-5-ethoxybenzimidazole (CM-346) on the EEG of MR and MNRA rats was compared with that of diazepam. Both CM-346 and diazepam reversed stress-induced changes in bioelectrical activity after intraperitoneal injection of 0.9% NaCl. In MR and MNRA rats both drugs decreased the EEG spectral power in the high-frequency θ-band (7.5–8.2 Hz). In MR rats, CM-346 increased the power of the low-frequency θ-rhythm (4.8–5.8 Hz) and the dominant activity peak (6.0–7.2 Hz) and decreased the spectral power in the 19–20 Hz band. The data suggest that CM-346 exerts antistressor and anxiolytic effects in animals with passive reactions to emotional stress. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 128, No. 11, pp. 500–503, November, 1999     

Does Greater Low Frequency EEG Activity in Normal Immaturity and in Children with Epilepsy Arise in the Same Neuronal Network?

Greater low frequency power (<8 Hz) in the electroencephalogram (EEG) at rest is normal in the immature developing brain of children when compared to adults. Children with epilepsy also have greater low frequency interictal resting EEG activity. Whether these power elevations reflect brain immaturity due to a developmental lag or the underlying epileptic pathophysiology is unclear. The present study addresses this question by analyzing spectral EEG topographies and sources for normally developing children and children with epilepsy. We first compared the resting EEG of healthy children to that of healthy adults to isolate effects related to normal brain immaturity. Next, we compared the EEG from 10 children with generalized cryptogenic epilepsy to the EEG of 24 healthy children to isolate effects related to epilepsy. Spectral analysis revealed that global low (delta: 1–3 Hz, theta: 4–7 Hz), medium (alpha: 8–12 Hz) and high (beta: 13–25 Hz) frequency EEG activity was greater in children without epilepsy compared to adults, and even further elevated for children with epilepsy. Topographical and tomographic EEG analyses showed that normal immaturity corresponded to greater delta and theta activity at fronto-central scalp and brain regions, respectively. In contrast, the epilepsy-related activity elevations were predominantly in the alpha band at parieto-occipital electrodes and brain regions, respectively. We conclude that lower frequency activity can be a sign of normal brain immaturity or brain pathology depending on the specific topography and frequency of the oscillating neuronal network.