Power spectral analysis of heart rate variability for assessment of diurnal variation of autonomic nervous activity in miniature swine.

BACKGROUND AND PURPOSES: The purpose of the study was to document diurnal variation of autonomic nervous functions by use of power spectral analysis of heart rate (HR) variability. METHODS: To clarify characteristics of power spectral analysis of HR variability, electrocardiogram (ECG), blood pressure (BP), and respiratory (Resp) waveform simultaneously were recorded. RESULTS: Two major spectral components were examined at low (LF)- and high (HF)-frequency bands for HR variability. Coherence between HR and Resp variabilities and HR and BP variabilities was maximal at approximately 0.14 and 0.03 Hz, respectively. On the basis of these data, two frequency bands of interest--LF (0.01 to 0.07 Hz) and HF (0.07 to 1.0 Hz)--were defined. Autonomic blockade studies indicated that the parasympathetic system mediated the HF and LF components, whereas the sympathetic system mediated only the LF component; HR had a diurnal pattern. The LF and HF bands in the dark phase tended to be higher than those in the light phase. The LF-to-HF ratio had a diurnal pattern similar to that of the HR. CONCLUSION: Parasympathetic nervous activity in miniature swine may be predominant in the dark phase. The characteristics of power spectra and diurnal variations of autonomic nervous functions are almost the same as those of humans. Therefore, miniature swine may be a useful animal model for future biobehavioral and pharmacotoxicologic studies.     

Power spectral analysis of heart rate variability for assessment of diurnal variation of autonomic nervous activity in guinea pigs.

We established characteristics of power spectral analysis of heart rate variability, and assessed the diurnal variations of autonomic nervous function in guinea pigs. For this purpose, an electrocardiogram (ECG) was recorded for 24 hr from conscious and unrestrained guinea pigs using a telemetry system. There were two major spectral components, at low frequency (LF) and high frequency (HF) bands, in the power spectrum of HR variability. On the basis of these data, we defined two frequency bands of interest: LF (0.07-0.7 Hz) and HF (0.7-3.0 Hz). The power of LF was higher than that of HF in the normal guinea pigs. Atropine significantly reduced power at HF. Propranolol also significantly reduced power at LF. Furthermore, the decrease in the parasympathetic mechanism produced by atropine was reflected in a slight increase in the LF/HF ratio. The LF/HF ratio appeared to follow the reductions of sympathetic activity produced by propranolol. Autonomic blockade studies indicated that the HF component reflected parasympathetic activity and the LF/HF ratio seemed to be a convenient index of autonomic balance. Nocturnal patterns, in which the values of heart rate in the dark phase (20:00-06:00) were higher than those in the light phase (06:00-20:00), were observed. However, the HF, LF and the LF/HF ratio showed no daily pattern. These results suggest that the autonomic nervous function in guinea pigs has no clear circadian rhythmicity. Therefore, this information may be useful for future studies concerning the autonomic nervous function in this species.     

低、高频电针诱导原癌基因c－fos／c－jun和阿片肽基因表达及其关系的比较研究

本工作对低频（２Ｈｚ）和高频（１００Ｈｚ）电针引起大鼠中枢Ｆｏｓ／Ｊｕｎ表达和三类阿片肽基因表达进行了详细的比较研究,并用针对ｃ－ｆｏｓ／ｃ－ｊｕｎ的反义寡核苷酸（ＯＤＮｓ）对电针引起的Ｆｏｓ／Ｊｕｎ表达进行选择性阻断,然后观察阿片肽基因表达是否受到影响,以确定Ｆｏｓ／Ｊｕｎ复合物在电针引起阿片肽基因表达中的作用。主要结果如下：（１）２Ｈｚ和１００Ｈｚ电针引起脑内不同部位的Ｆｏｓ／Ｊｕｎ表达;（２）２Ｈｚ电针使前脑啡肽原（ＰＰＥ）ｍＲＮＡ表达大幅度增高,１００Ｈｚ电针也能增加ＰＰＥｍＲＮＡ的转录,但不如２Ｈｚ电针的作用显著;但１００Ｈｚ电针能使某些脑区的前强啡肽原（ＰＰＤ）基因转录加速,而２Ｈｚ电针没有这一作用;（３）用ｃ－ｆｏｓ／ｃ－ｊｕｎ反义ＯＤＮｓ特异地阻断Ｆｏｓ／Ｊｕｎ表达后,电针引起的ＰＰＤ转录加速被明显阻断,而ＰＰＥ表达不受影响。提示Ｆｏｓ／Ｊｕｎ是电针引起ＰＰＤ（而非ＰＰＥ）基因表达的转录因子。     

Neonatal heart rate variability and its relation to respiration

The heart rate and respiration signals from nine healthy full term neonates were studied using autoregressive spectral analysis and cross-correlation techniques. The heart rate spectra could be divided into three regions of activity: a very low frequency (VLF) region from 0-0.04 Hz; a low frequency (LF) band from 0.04-0.20 Hz; and a high frequency (HF) region above 0.20 Hz. The newborns exhibited very little respiratory sinus arrhythmia in their heart rate variability in contrast to the situation for adults and older infants. However, variations in heart rate correlated strongly with changes in the breath amplitude, leading to what may be termed a breath amplitude sinus arrhythmia. The neonatal heart rate behaviour under stable conditions of oscillation could be simulated with a nonlinear control model provided the delay time in the baroreceptor loop of the model was taken to be approximately 2 seconds longer than in adults. This is consistent with the immature neurological status of neonates.     

Engagement of inducible nitric oxide synthase at the rostral ventrolateral medulla during mevinphos intoxication in the rat

We evaluated the relationship between the toxicity induced by the organophosphate mevinphos (Mev) and inducible nitric oxide synthase (iNOS) in the rostral ventrolateral medulla (RVLM), the medullary origin of sympathetic neurogenic vasomotor tone. Adult Sprague-Dawley rats that were anesthetized and maintained with propofol were used. Laser scanning confocal microscopic analysis revealed colocalization of the M2 subtype of muscarinic receptors (M(2)R) and iNOS immunoreactivity in RVLM neurons. Comicroinjection bilaterally of Mev (10 nmol) and artificial cerebrospinal fluid (aCSF) into the RVLM elicited a progressive decline in systemic arterial pressure (SAP) and heart rate. This was accompanied during phase 1 Mev intoxication by an increase in the power density of the very high-frequency (VHF; 5-9 Hz), high-frequency (HF; 0.8-2.4 Hz), low-frequency (LF; 0.25- 0.8 Hz) and very low-frequency (VLF; 0-0.25 Hz) components of SAP signals. Phase 2 exhibited a reversal of the VHF and VLF power to control levels and a further reduction in the power density of both HF and LF components to below baseline. Hypotension and bradycardia promoted by Mev were significantly blunted on coadministration into the RVLM of the selective iNOS inhibitors S-methylisothiourea (250 pmol) or aminoguanidine (250 pmol). Not only was the augmented power density of HF and LF components during phase 1 Mev intoxication further enhanced, the reduced power of these two spectral components during phase 2 was appreciably antagonized. On the other hand, the temporal changes in VHF and VLF power were essentially the same as with coadministration of Mev and aCSF. We conclude that, as a cholinesterase inhibitor, Mev may induce toxicity via nitric oxide produced by iNOS on activation of the M(2)R by the accumulated acetylcholine in the RVLM.     

Effect of paced breathing on ventilatory and cardiovascular variability parameters during short-term investigations of autonomic function

Paced breathing (PB) around 0.25 Hz has been advocated as a means to avoid confounding and to standardize measurements in short-term investigations of autonomic cardiovascular regulation. Controversy remains, however, as to whether it causes any alteration in autonomic control. We addressed this issue in 40 supine, middle-aged, healthy volunteers by assessing the changes induced by PB (0.25 Hz for 8 min) on 1) ventilatory parameters, 2) the indexes of autonomic control of cardiovascular function, and 3) the spectral indexes of cardiovascular variability. Subjects were grouped into group 1 (n = 31), if spontaneous breathing was regular and within the high-frequency (HF) band (0.15-0.45 Hz), or group 2 (n = 9), if it was irregular or slow (< 0.15 Hz). In both groups, PB was accompanied by an increase in minute ventilation (both groups, P < 0.01), whereas tidal volume increased only in group 1 (P = 0.0003). End-tidal CO2 decreased by [median (lower quartile, upper quartile)] -0.2 (-0.5, -0.1)% (group 1, P < 0.0001) and -0.6 (-0.8, -0.5)% (group 2, P = 0.008). Mean R-R interval and systolic and diastolic pressure remained remarkably stable (all P > or = 0.13, both groups). No significant changes were observed in spectral indexes of R-R and pressure variability (all P > or = 0.12, measured only in group 1 to avoid confounding), except in the HF power of pressure signals, which significantly increased (all P < 0.05) in association with increased tidal volume. In conclusion, PB at 0.25 Hz causes a slight hyperventilation and does not affect traditional indexes of autonomic control or, in subjects with spontaneous breathing in the HF band, most relevant spectral indexes of cardiovascular variability. These findings support the notion that PB does not alter cardiovascular autonomic regulation compared with spontaneous breathing.     

Changes in autonomic control of heart associated with classical appetitive conditioning in rats.

The aim of this study was to examine the changes in autonomic control of the heart associated with classical appetitive conditioning in rats. We trained rats to learn that a movement into a test chamber was followed by delivery of reward (contextual conditioning) and performed power spectral analysis of heart rate variability from electrocardiograms recorded using the telemetry system. We investigated the sympathovagal balance of autonomic regulation of the heart in response to not only the conditioned stimulus (the movement into the test chamber), but also the unconditioned stimulus (reward), and compared the results of these two kinds of emotional states; it might be considered that "the reward-expecting state" is evoked by the conditioned stimulus and "the reward-receiving state" is evoked by the unconditioned stimulus in rats. The reward-expecting state resulted in a significant increase in both low frequency (LF) power and high frequency (HF) power with no change in heart rate (HR) and LF/HF ratio, indicating that both sympathetic and parasympathetic activity increased with no change in sympathovagal balance. The reward-receiving state resulted in a significant increase in HR and a significant decrease in LF power, HF power, and LF/HF ratio, indicating that both sympathetic and parasympathetic activity decreased with predominance in the parasympathetic activity. These results suggest that the method performed in our present study might be useful for distinguishing between two different emotional states evoked by classical appetitive conditioning in rats.     

Capsaicin increases modulation of sympathetic nerve activity in rats: measurement using power spectral analysis of heart rate fluctuations

We assessed the sympatho-vagal activities of the heart after administration of capsaicin by measuring the power spectral analysis in rats. There were major two frequency components of heart rate variability, which we defined as high (1.0 Hz <, HF) and low (LF, < 1.0 Hz) frequency components. Vagal blockade by atropine abolished the high frequency component, and lowered the amplitude of the low frequency component. On the other hand, under conditions of sympathetic blockade by propranolol, the low frequency component was reduced. Combined vagal and sympathetic blockade abolished all heart rate fluctuations. We analyzed the low and high frequency components by integrating the spectrum for the respective band width. The rats administered capsaicin had a higher heart rate and sympathetic nervous system index (LF/HF) than the control group of rats. These results suggest that power spectral analysis is an effective and noninvasive method for detecting subtle changes in autonomic activity in response to the intake of foods or drugs.     

Time-variant spectral analysis of heart rate variability during parabolic flight with and without LBNP

Modifications of autonomic activity during parabolic flight were studied by a time-variant model able to estimate low (LF, 0.04-0.14 Hz) and high (HF, 0.14-0.35 Hz) frequency spectral components on a beat-to-beat basis. Ten subjects were studied with and without lower body negative pressure (LBNP). ECG and Gz load were digitized (500 Hz) and RR interval variability series extracted. Beat-to-beat mean RR, variance, LF and HF power were obtained. One-way ANOVA (p<0.01) was used to compare values obtained during starting 1Gz (I), first 1.8Gz (II), 0Gz (III), second 1.8Gz (IV), ending 1Gz (V). Without LBNP, total and LF power increased during 0Gz to 1.69 +/- 1.41 and 2.87 +/- 4.66 respectively (mean +/- SD, normalized by phase I value). With LBNP, their change during 0Gz (1.38 +/- 1.37 and 1.54 +/- l.04 respectively) reached significance only with phase II and phase V. Phase I HF power was higher than in the other phases, both without and with LBNP.     

High and low frequency electroacupuncture analgesia are mediated by different types of opioid receptors at spinal level: a cross tolerance study

Previous studies have shown that rats subjected to low or high frequency electroacupuncture (EA) stimulation release enkephalins or dynorphins respectively to produce analgesia. This conclusion was tested in the present study by using cross tolerance technique for further analysing their receptor mechanisms. The main results were as follows: (1) In rats subjected to 2 Hz EA for 6 h, there was a gradual decrease in the analgesic effect, leading to a state of tolerance to 2 Hz EA analgesia. These rats, however, still responded to 100 Hz EA. Likewise, rats made tolerant to 100 Hz EA were still effective to 2 Hz EA stimulation, showing not significant cross tolerance between 2 Hz and 100 Hz EA analgesia. (2) Rats made-tolerant to 100 Hz EA analgesia showed a diminished response to intrathecal dynorphin A (1-13), a kappa agonist, whereas the analgesic effect of the delta agonist [D-Pen2, D-pen5] enkephalin (DPDPE) remained intact. (3) Rats made tolerant to 2 Hz EA analgesia showed a cross tolerance to DPDPE, but not to dynorphin A (1-13). Results obtained from aforementioned cross tolerance studies suggest that 2 Hz and 100 Hz EA analgesia are mediated by delta and kappa opioid receptors, respectively, at the spinal cord of the rat.     

Differential responses of frequency components of renal sympathetic nerve activity to arterial pressure changes in conscious rats

The present study examined the effects of baroreceptor loading and unloading on the various rhythms present in the renal sympathetic nerve activity (RSNA) of 10 conscious rats. Short-lasting (4-5 min), steady-state decreases (from -10 to -40 mmHg) and increases (from 5 to 30 mmHg) in arterial pressure (AP) were induced by the intravenous infusion of sodium nitroprusside and phenylephrine, respectively. The relationship between changes in AP level and RSNA total power (fast Fourier transform analysis; 0-25 Hz) was characterized by an inverse sigmoid function. Basal AP was located 6.3 mmHg above AP at the midrange of the curve, that is, near the lower plateau. Sigmoid relationships were also observed for spectral powers in the low (LF, 0.030-0.244 Hz), respiratory (0.79-2.5 Hz) and high-frequency (HF, 2.5-25 Hz) bands. In contrast, in the MF band (0.27-0.76 Hz) containing oscillations associated with Mayer waves, the AP-RSNA power relationship showed a bell curve shape with a maximum at 21 mmHg below basal AP. Similarly, changes in RSNA power at the frequency of the heart beat were well characterized by a bell curve reaching a maximum at 22 mmHg below basal AP. Under baseline conditions, LF, MF, respiratory and HF powers contributed approximately 3, 10, 18, and 69% of the total RSNA power, respectively. The pulse-synchronous oscillation of RSNA accounted for only 11 +/- 1% of HF power. The contribution of HF power to total power did not change consistently with AP changes. Therefore, most of the baroreflex-induced changes in RSNA are mediated by changes in the amplitude of fast, irregular fluctuations.     

Cardiac Autonomic Modulation Is Determined by Gender and Is Independent of Aerobic Physical Capacity in Healthy Subjects

Background

Aerobic physical capacity plays an important role in reducing morbidity and mortality rates in subjects with cardiovascular diseases. This action is often related to an improvement in the autonomic modulation of heart rate variability (HRV). However, controversies remain regarding the effects of physical training on cardiac autonomic control in healthy subjects. Therefore, our objective was to investigate whether aerobic capacity interferes with the autonomic modulation of HRV and whether gender differences exist.

Methods

Healthy men and women (N=96) were divided into groups according to aerobic capacity: low (VO₂: 22-38 ml/kg^-1 min^-1), moderate (VO₂: 38-48 ml/kg^-1 min^-1) and high (VO₂ >48 ml/kg^-1 min^-1.) We evaluated the hemodynamic parameters and body composition. The autonomic modulation of HRV was investigated using spectral analysis. This procedure decomposes the heart rate oscillatory signal into frequency bands: low frequency (LF=0.04-0.15Hz) is mainly related to sympathetic modulation, and high frequency (HF=0.15-0.5Hz) corresponds to vagal modulation.

Results

Aerobic capacity, regardless of gender, determined lower values of body fat percentage, blood pressure and heart rate. In turn, the spectral analysis of HRV showed that this parameter did not differ when aerobic capacity was considered. However, when the genders were compared, women had lower LF values and higher HF values than the respective groups of men.

Conclusion

The results suggest that aerobic physical capacity does not interfere with HRV modulation; however, the cardiac modulatory balance differs between genders and is characterized by a greater influence of the autonomic vagal component in women and by the sympathetic component in men.     

Comparative analysis of EEG spatial organization in the rats with different level of genetically determinated anxiety under ethanol

The pecularities of EEG changes in the rats with geneticaly different level of anxiety was studed after ethanol injection. The biopotentials spatial synchronization and entropy in the "high anxious" rats (strain MR) did not increase under low dose; on the contrary the above changes were characteristic for the rats without anxiety signs (strain MNRA). After injection of middle and high ethanol doses the "high anxious" rats as compared with "low anxious" ones had the "simplification" of reaction type--the increase of narrow frequency coherence (i.e. linear biopotentials relationship) and spectral power of theta-activity (5.75-7.25 Hz), which was combined with the decrease of nonlinear biopotential characteristics. This fact is interpreted as the predominance of subcortical mechanisms of the brain functional state regulation over cortical ones. The significant decrease of high frequency EEG components in "high anxious" rats takes place under more high ethanol doses, presumably reflecting the increase of the anxiolytic level of ethanol effect.     

Relationship between cortical electrical and cardiac autonomic activities in the awake lizard, Gallotia galloti

ECG and EEG signals were simultaneously recorded in lizards, Gallotia galloti, both in control conditions and under autonomic nervous system (ANS) blockade, in order to evaluate possible relationships between the ANS control of heart rate and the integrated central nervous system activity in reptiles. The ANS blockers used were prazosin, propranolol, and atropine. Time-domain summary statistics were derived from the series of consecutive R-R intervals (RRI) of the ECG to measure beat-to-beat heart rate variability (HRV), and spectral analysis techniques were applied to the EEG activity to assess its frequency content. Both prazosin and atropine did not alter the power spectral density (PSD) of the EEG low frequency (LF: 0.5-7.5 Hz) and high frequency (HF: 7.6-30 Hz) bands, whereas propranolol decreased the PSD in these bands. These findings suggest that central beta-adrenergic receptor mechanisms could mediate the reptilian waking EEG activity without taking part any alpha(1)-adrenergic and/or cholinergic receptor systems. In 55% of the lizards in control conditions, and in approximately 43% of the lizards under prazosin and atropine, a negative correlation between the coefficient of variation of the series of RRI value (CV(RRI)) and the mean power frequency (MPF) of the EEG spectra was found, but not under propranolol. Consequently, the lizards' HRV-EEG-activity relationship appears to be independent of alpha(1)-adrenergic and cholinergic receptor systems and mediated by beta-adrenergic receptor mechanisms.     

Elevated C-Reactive Protein Levels and Enhanced High Frequency Vasomotion in Patients with Ischemic Heart Disease during Brachial Flow-Mediated Dilation

Purpose

The physiological role of vasomotion, rhythmic oscillations in vascular tone or diameter, and its underlying mechanisms are unknown. We investigated the characteristics of brachial artery vasomotion in patients with ischemic heart disease (IHD).

Methods

We performed a retrospective study of 37 patients with IHD. Endothelial function was assessed using flow-mediated dilation (FMD), and power spectral analysis of brachial artery diameter oscillations during FMD was performed. Frequency-domain components were calculated by integrating the power spectrums in three frequency bands (in ms²) using the MemCalc (GMS, Tokyo, Japan): very-low frequency (VLF), 0.003–0.04 Hz; low frequency (LF), 0.04–0.15 Hz; and high frequency (HF), 0.15–0.4 Hz. Total spectral power (TP) was calculated as the sum of all frequency bands, and each spectral component was normalized against TP.

Results

Data revealed that HF/TP closely correlated with FMD (r = −0.33, p = 0.04), whereas VLF/TP and LF/TP did not. We also explored the relationship between elevated C-reactive protein (CRP) levels and vasomotion. HF/TP was significantly increased in subjects with high CRP levels (CRP;>0.08 mg/dL) compared with subjects with low CRP levels (0.052±0.026 versus 0.035±0.022, p<0.05). The HF/TP value closely correlated with CRP (r = 0.24, p = 0.04), whereas the value of FMD did not (r = 0.023, p = 0.84). In addition, elevated CRP levels significantly increased the value of HF/TP after adjustment for FMD and blood pressure (β = 0.33, p<0.05).

Conclusion

The HF component of brachial artery diameter oscillation during FMD measurement correlated well with FMD and increased in the presence of elevated CRP levels in subjects with IHD.     

The effect of sinus node depression on heart rate variability in humans using zatebradine, a selective bradycardic agent

Zatebradine is a bradycardic agent with a selective effect on the pacemaker current in the sinus node. The effect of such drugs on heart rate variability is not known. Thirty-six patients without structural heart disease were randomly assigned to receive 10 mg of zatebradine i.v. (n = 24) or isotonic saline (n = 12). Heart rate variability (HRV) was recorded as power in the very low frequency (VLF, 0.003-0.040 Hz), low frequency (LF, 0.040-0.150 Hz), and high frequency (HF, 0.150-0.400 Hz) spectral bands as well as total power (TP, 0.003-0.400 Hz) during 5-min ECG acquisitions at baseline, 30, and 60 min following the start of the infusion. No change in heart rate variability was detected in the control group. Zatebradine significantly reduced heart rate variability at 60 min in all frequency bands: VLF (-12+/-4%, p<0.001), LF (-19+/-4%, p<0.001), and HF (-26+/-5%, p<0.001). The reduction in HRV following zatebradine is due to depression of sinus node response to all external stimuli and underscores the need for documentation of normal sinus node function in HRV research.     

Narrow-band changes in the spectral composition of the EEG under the influence of an agonist and antagonist of the cholinergic neuromediator system]

The EEG effects of intake of the mean therapeutic single dose of cholinomimetic amiridin (20 mg) or cholinolytic amizyl (2 mg) were studied in 7 healthy subjects. After the intake of the drugs with agonistic and antagonistic action, significant opposite changes in the EEG spectral density were observed in the frequency ranges of 0.6-6.7, 7.7-11.4, and 24.8-29.7 Hz. Amizyl produced an enhancement of the spectral density of the delta-, theta- and beta 2 activity and reduction of the alpha-rhythm power, while under the action of amiridin the spectral density of these rhythms changed in opposite directions. The oppositely directed changes in the alpha range were most pronounced. The peak frequency of amiridin-induced shift was equal to 9.8-10 Hz, and the same value of the spectral change induced by amizyl was 10.8-11.4 Hz. It is suggested that the spectral power density of the alpha-rhythm is an EEG index of the level of cholinergic activation.     

Increase in Parasympathetic Nerve Activity During the Nighttime Following Bright Light Exposure During the Daytime

A spectral analysis of heart rate was carried out on 11 young female adults in order to evaluate the effects of bright light exposure on autonomic nervous activity. Bright light (5,000 lx) was provided by fluorescent lamps during the daytime (07:00-15:00) on day 1. Dim light (200 lx) was given on day 2. High frequency components (HF: 0.15-0.4Hz) were used as a marker of parasympathetic activity and the ratio of low frequency (LF: 0.04-0.15 HZ) to high frequency (LF/HF) as an indicator of sympathetic activity. The average value during the sleep period (23:30-06:30) was compared following diurnal exposure to bright or dim light. HF component was significantly greater from 23:30 to 02:00 after diurnal exposure of bright light, being accompanied by lower heart rate during these periods. There existed negative correlation between heart rate and HF component from 23:30 to 02:00 under diurnal exposure to bright and dim lights. The results indicate that bright light exposure during the daytime (07:00-15:00) could enhance parasympathetic activity around midnight.     

Spectral analysis of muscle sympathetic nerve activity in heat-stressed humans

Whole body heating increases muscle sympathetic nerve activity (MSNA); however, the effect of heat stress on spectral characteristics of MSNA is unknown. Such information may provide insight into mechanisms of heat stress-induced MSNA activation. The purpose of the present study was to test the hypothesis that heat stress-induced changes in systolic blood pressure variability parallel changes in MSNA variability. In 13 healthy subjects, MSNA, electrocardiogram, arterial blood pressure (via Finapres), and respiratory activity were recorded under both normothermic and heat stress conditions. Spectral characteristics of integrated MSNA, R-R interval, systolic blood pressure, and respiratory excursions were assessed in the low (LF; 0.03-0.15 Hz) and high (HF; 0.15-0.45 Hz) frequency components. Whole body heating significantly increased skin and core body temperature, MSNA burst rate, and heart rate, but not mean arterial blood pressure. Systolic blood pressure and R-R interval variability were significantly reduced in both the LF and HF ranges. Compared with normothermic conditions, heat stress significantly increased the HF component of MSNA, while the LF component of MSNA was not altered. Thus the LF-to-HF ratio of MSNA oscillatory components was significantly reduced. These data indicate that the spectral characteristics of MSNA are altered by whole body heating; however, heat stress-induced changes in MSNA do not parallel changes in systolic blood pressure variability. Moreover, the reduction in LF component of systolic blood pressure during heat stress is unlikely related to spectral changes in MSNA.     

Differences in neural-immune gene expression response in rat spinal dorsal horn correlates with variations in electroacupuncture analgesia

Background

Electroacupuncture (EA) has been widely used to alleviate diverse pains. Accumulated clinical experiences and experimental observations indicated that significant differences exist in sensitivity to EA analgesia for individuals of patients and model animals. However, the molecular mechanism accounting for this difference remains obscure.

Methodology/Principal Findings

We classified model male rats into high-responder (HR; TFL changes >150) and non-responder (NR; TFL changes ≤0) groups based on changes of their pain threshold detected by tail-flick latency (TFL) before and after 2 Hz or 100 Hz EA treatment. Gene expression analysis of spinal dorsal horn (DH) revealed divergent expression in HR and NR after 2 Hz/100 Hz EA. The expression of the neurotransmitter system related genes was significantly highly regulated in the HR animals while the proinflammation cytokines related genes were up-regulated more significantly in NR than that in HR after 2 Hz and 100 Hz EA stimulation, especially in the case of 2 Hz stimulation.

Conclusions/Significance

Our results suggested that differential regulation and coordination of neural-immune related genes might play an important role for individual variations in analgesic effects responding to EA in DH. It also provided new candidate genes related to EA responsiveness for future investigation.