Diaphragm fatigue induced by inspiratory resistive loading in spontaneously breathing rabbits

Diaphragmatic contractility was assessed in spontaneously breathing ketamine-anesthetized rabbits by measuring the strength of diaphragmatic contraction in response to bilateral supramaximal phrenic nerve stimulation at frequencies between 10 and 100 Hz. During 10-180 min of inspiratory resistive loading, contractility decreased by approximately 40%, and hypoxemia and both respiratory and lactic acidosis developed. After 10 min of recovery, both the response to high-frequency stimulation (100 Hz) and the arterial PO2 and PCO2 returned to base-line levels, whereas metabolic acidosis and reduced response to low-frequency stimulation (10-20 Hz) persisted. Similar levels of hypoxemia and respiratory acidosis in the absence of inspiratory resistive loading did not alter diaphragmatic contractility. We conclude that in anesthetized rabbits excessive inspiratory resistive loading results in partially reversible diaphragm fatigue of the high- and low-frequency types, accompanied by hypoventilation and lactic acidosis.     

Cardiac autonomic control during balloon carotid angioplasty and stenting

Hemodynamic alterations during balloon carotid angioplasty (BCA) and stenting have been ascribed to the consequences of direct carotid baroreceptor stimulation during balloon inflation. BCA with stenting in patients with carotid atheromatous stenoses offers a unique opportunity for elucidating the cardiovascular autonomic response to direct transient intravascular stimulation of the baroreceptors. We analysed the consequences of BCA on the autonomic control of heart rate and on breathing components in nine patients with atheromatous stenoses involving the bifurcation and the internal carotid. A time-frequency domain method, the smoothed pseudo-Wigner-Ville transform (SPWVT), was used to evaluate the spectral parameters (i.e., the instantaneous amplitude and centre frequency (ICF) of the cardiovascular and respiratory oscillations). Those parameters and their dynamics (8 and 24 h later) were evaluated during and after the procedure. BCA stimulates baroreceptors in all patients, which markedly reduces heart rate and blood pressure. Vagal baroreflex activation altered the respiratory sinus arrhythmia in terms of amplitude and frequency (ICF HF RR shifted from 0.27 +/- 0.03 to 0.23 +/- 0.04 Hz pre-BCA vs. BCA, respectively; p < 0.01). Both the high- and low-frequency amplitudes of heart rate oscillations were altered during carotid baroreceptor stimulation, strongly supporting a contribution of the baroreflex to the generation of both oscillations of heart rate. Carotid baroreceptors stimulation increased the inspiratory time (Ti) (1.5 +/- 0.5 to 2.3 +/- 0.6 s pre-BCA vs. BCA, respectively; p < 0.01). In awake patients, BCA with stenting of atheromatous stenosis involving the bifurcation and internal carotid causes marked changes in the cardiac autonomic and respiratory control systems.     

Cardiorespiratory interactions during periodic breathing in awake chronic heart failure patients

We applied spectral techniques to the analysis of cardiorespiratory signals [instantaneous lung volume (ILV), instantaneous tidal volume (ITV), arterial O(2) saturation (Sa(O(2))) at the ear, heart rate (HR), systolic (SAP), and diastolic (DAP) arterial pressure] during nonapneic periodic breathing (PB) in 29 awake chronic heart failure (CHF) patients and estimated the timing relationships between respiratory and slow cardiovascular (<0.04 Hz) oscillations. Our aim was 1) to elucidate major mechanisms involved in cardiorespiratory interactions during PB and 2) to test the hypothesis of a central vasomotor origin of PB. All cardiovascular signals were characterized by a dominant (>/=84% of total power) oscillation at the frequency of PB (mean +/- SE: 0.022 +/- 0.0008 Hz), highly coherent (>/=0.89), and delayed with respect to ITV (ITV-HR, 2.4 +/- 0.72 s; ITV-SAP, 6.7 +/- 0.65 s; ITV-DAP, 3.2 +/- 0.61 s; P < 0.01). Sa(O(2)) was highly coherent with (coherence function = 0.96 +/- 0. 009) and almost opposite in phase to ITV. These findings demonstrate the existence of a generalized cardiorespiratory rhythm led by the ventilatory oscillation and suggest that 1) the cyclic increase in inspiratory drive and cardiopulmonary reflexes and 2) mechanical effects of PB-induced changes in intrathoracic pressure are the more likely sources of the HR and blood pressure oscillations, respectively. The timing relationship between ITV and blood pressure signals excludes the possibility that PB represents the effect of a central vasomotor rhythm.     

Cocaine alters heart rate dynamics in conscious ferrets.

This study was designed to test the hypothesis that cocaine intoxication induces distinctive alterations in sinus rhythm heart rate dynamics. Time-series and spectral analysis techniques were used to examine the effects of lethal doses of cocaine on heart rate variability in conscious, restrained ferrets. In all animals (n = 5), cocaine administration resulted in a marked decrease in sinus rhythm heart rate variability prior to sudden death. Heart rate variability (coefficient of variation of heart rate) just prior to death (0.018 +/- 0.005) was significantly (p less than 0.02) decreased compared to that at baseline prior to cocaine administration (0.061 +/- 0.022). There was also a significant (p less than 0.02) decrease in total spectral power prior to death compared to baseline. Transient low-frequency (0.04-0.10 Hz) oscillations in heart rate were also noted in three of the five animals following cocaine administration. There were, however, no significant changes in mean heart rate in response to cocaine. Alterations in heart rate dynamics were not seen in three saline-treated controls. Lethal effects of cocaine included ventricular arrhythmias (n = 2) and seizures (n = 3). One animal developed transient ST segment elevations that were consistent with coronary vasospasm. In conclusion, lethal doses of cocaine in the conscious ferret induce characteristic alterations in heart rate dynamics. These abnormalities (loss of heart rate variability and the appearance of low-frequency heart rate oscillations) are similar to those reported previously in certain patients at high risk of sudden cardiac death due to organic heart disease.     

High-frequency oscillations within early and late phases of the phrenic neurogram

Spectral analyses were performed on phrenic neurogram recordings from 18 cats to identify high-frequency oscillations (HFOs) inherent in the signals at different phases of inspiratory activity. Gating the analysis for the entire inspiratory phase resulted in dual spectral HFOs (27 and 83 Hz), both of which persisted when the analysis was repeated on the later phase of phrenic inspiratory activity alone (29 and 82 Hz). A third pass at the same data, gating for just the early phase of phrenic discharge, however, resulted in single spectral HFOs at the higher frequency only (86 Hz). Because both early and late recruited phrenic motoneurons carry both higher and lower spectral frequencies, these results demonstrate that the lower frequency HFO is distinctly delayed in onset compared with the higher frequency HFO, the latter of which is believed to have a brain stem origin. This delayed onset may be important in identifying the source of the lower frequency HFO, which appears to be specific to various respiratory efferent systems.     

The variability of respiratory pattern and gas exchange

It is known, that spectral analysis of heart rate and respiratory variability allows to find out the very low frequency (VLF) rhythm. However it is not known, it is necessary to carry this rhythm to what type of wave processes. The purpose of the present researches was to study the respiratory variability and the variability of gas exchange parameters. 10 healthy subjects have been surveyed. The pneumogramms within 30 minutes spent record, and then a method "breath-by-breath" within 30 minutes registered gas exchange parameters (Ve--lung ventilation, V(O2) -O2 consumption and other parameters). Fast Fourier transform method has found out two groups of the basic peaks. The first--in a range 0.2-0.3 Hz (a time cycle--3-5 s), that corresponds respiratory frequency which size at subjects varied from 12 to 20 per minute. The second--in a range 0.002-0.0075 Hz, that corresponds VLF diapason (a time cycle--1-3.5 minutes). At the analysis pneumogramms rhythms in the same ranges have been established. The carried out researches allow to draw a conclusion on steady character of wave process in a VLF-range. It can be carried to quasi-periodic oscillations type. First oscillator or respiratory frequency it is formed by means of mechanisms of chemoreception. Considering, that V(O2) and V(CO2) are function energy exchange, it is possible to believe, what exactly energy demand define the second oscillator.     

Ontogeny of respiratory control and pulmonary mechanics in newborn rabbits

Maturation of the respiratory pattern and the active and passive mechanical properties of the respiratory system were assessed in 19 tracheotomized rabbits (postnatal age range: 1-26 days) placed in a body plethysmograph. With maturation both minute ventilation and tidal volume significantly increased, whereas respiratory frequency decreased. When normalized for body weight (kg) both the passive (Rrs X kg) and active (R'rs X kg) resistances of the respiratory system significantly increased with age, whereas the corresponding passive (Crs X kg-1) and active (C'rs X kg-1) compliances significantly decreased. At any given age R'rs X kg only slightly exceeded Rrs X kg, whereas C'rs X kg-1 was significantly lower than Crs X kg-1. Moreover, the maturational increases in Rrs X kg and R'rs X kg exceeded the corresponding decreases in Crs X kg-1 and C'rs X kg-1, resulting in significant age-related increases in both the passive (tau rs) and active (tau'rs) time constants of the respiratory system. Due to the age-related increases in tau'rs, producing a delayed volume response to any given inspiratory driving pressure, the relative volume loss obtained at any time during inspiration was greater in the maturing rabbit. On the other hand, because of concomitant compensatory changes in respiratory pattern, evidenced by increases in inspiratory duration with age, the end-inspiratory tidal volume loss in the maturing animal was maintained generally less than 10% at all postnatal ages. Thus maturational changes in respiratory pattern appear coupled to changes in the active mechanical properties of the respiratory system. The latter coupling serves to optimize the transduction of inspiratory pressure into volume change in a manner consistent with establishing the minimum inspiratory work of breathing during postnatal development.     

Secondary Rhythms of Cardiac Activity in Rat Ontogeny

Endogenous periodic oscillations of the heart beat rate are described in rat pups aged 3–4, 7–8, 10–11, 13–14, 21–22 days and 1.5 month after birth. These oscillations have all characteristic features established earlier for the secondary rhythms of endogenous contractile activity in the wall of various regions of the gastrointestinal tract and for bursts of spontaneous somatomotor excitation in the early postnatal ontogeny of rats: a multi-stage organization, inconstancy, irregularity of components. In frequency spectra of secondary oscillations of the heart rate obtained by means of fast Fourier transform of R–R intervals of the periodogram, age-related changes of the spectral frequency power are demonstrated in 4 ranges, 0.01–0.03, 0.03–0.1, 0.1–1.0, and 1.0–2.5 Hz, which correspond to the about-one-minute, decasecond, and about-one-second waves of the heart rhythm oscillations and to sinus arrhythmia. It is shown that the dominating frequencies of the secondary rhythms in each range do not have regular age-related changes, which is characteristic of all endogenous secondary rhythms.     

Power spectra of inspiratory nerve activity with lung inflations in cats

To investigate the effect of lung inflations on the high-frequency synchrony (70-122 Hz) observed in the inspiratory activity of respiratory motor nerves of decerebrate cats, I applied a step increase in lung inflation pressure at fixed delays into the inspiratory phase and computed power spectra of phrenic neurograms before and during inflation. In 25 decerebrate paralyzed cats the frequency of the high spectral peak was 92.3 +/- 11.1 Hz before and 105.3 +/- 12.1 Hz during the step in inflation pressure, shifting upward by 13.0 +/- 6.0 Hz. For 8 of the 25 cats, the recurrent laryngeal and phrenic neurograms were recorded simultaneously. The high spectral peak was present during inspiration in the recurrent laryngeal power spectra and coherent with the high peak in the phrenic power spectra. In response to lung inflation, the high peak disappeared from the power spectra of the recurrent laryngeal nerve as the inspiratory activity was inhibited; a shift upward in frequency was not detectable. Comparing inspiratory times (TI, based on the phrenic neurograms) for breaths with no lung inflations to those for breaths with lung inflations, I found that lung inflations early in inspiration caused a decrease in TI, lung inflations at intermediates times had no effect on TI, and lung inflations late in inspiration caused an increase in TI. Despite lung inflation decreasing, not affecting, or increasing inspiratory duration and amplitude of the phrenic neurogram, lung inflation always caused a shift upward in the high-frequency peak of the phrenic power density. The fact that lung inflation, a powerful respiratory stimulus, affected the frequency of the high peak in a consistent manner suggests that the high-frequency synchrony is an important and robust feature of the central respiratory pattern generator.     

Spontaneous fluctuations in cerebral blood flow: insights from extended-duration recordings in humans

To determine the dependence of cerebral blood flow (CBF) on arterial pressure over prolonged time periods, we measured beat-to-beat changes in mean CBF velocity in the middle cerebral artery (transcranial Doppler) and mean arterial pressure (Finapres) continuously for 2 h in six healthy subjects (5 men and 1 woman, 18-40 yr old) during supine rest. Fluctuations in velocity and pressure were quantified by the range [(peak - trough)/mean] and coefficients of variation (SD/mean) in the time domain and by spectral analysis in the frequency domain. Mean velocity and pressure over the 2-h recordings were 60 +/- 7 cm/s and 83 +/- 8 mmHg, associated with ranges of 77 +/- 8 and 89 +/- 10% and coefficients of variation of 9.3 +/- 2.2 and 7.9 +/- 2.3%, respectively. Spectral power of the velocity and pressure was predominantly distributed in the frequency range of 0.00014-0.1 Hz and increased inversely with frequency, indicating characteristics of an inverse power law (1/f(alpha)). However, linear regression on a log-log scale revealed that the slope of spectral power of pressure and velocity was steeper in the high-frequency (0.02-0.5 Hz) than in the low-frequency range (0.002-0.02 Hz), suggesting different regulatory mechanisms in these two frequency ranges. Furthermore, the spectral slope of pressure was significantly steeper than that of velocity in the low-frequency range, consistent with the low transfer function gain and low coherence estimated at these frequencies. We conclude that 1) long-term fluctuations in CBF velocity are prominent and similar to those observed in arterial pressure, 2) spectral power of CBF velocity reveals characteristics of 1/f(alpha), and 3) cerebral attenuation of oscillations in CBF velocity in response to changes in pressure may be more effective at low than that at high frequencies, emphasizing the frequency dependence of cerebral autoregulation.     

Quantitative estimation of connection of the heart rate rhythm with motor activity in rat fetuses

In rat fetuses over E17-20 with preserved placental circulation with use of mathematical analysis there were revealed value and character of connections of slow wave oscillations of the heart rhythm with motor activity for 30 min of observation. In the software PowerGraph 3.3.8, normalization and filtration of the studied signals were performed in three frequency diapasons: D1-0.02–0.2 Hz (5–50 s), D2-0.0083-0.02 Hz (50 s-2 min), and D3-0.0017–0.0083 Hz (2–10 min). The EMG curves filtrated by diapasons or piezograms were compared with periodograms in the corresponding diapasons of the heart rhythm variations. In the software “Origin 8.0”, quantitative estimation of the degree of intersystemic interrelations for each frequency diapason was performed by Pearson correlation of coefficient, by the correlation connection value, and by the time shift of maximum of cross-correlation function. It has been established that in the frequency D1, regardless of age, the connection of heart rhythm oscillations with motor activity is expressed weakly. In the frequency diapason D2, the connection in most cases is located in the zone of weak and moderate correlations. In the multiminute diapason (D3), the connection is more pronounced. The number of animals that have a significant value of the correlation connection rises. The fetal motor activity fires in the decasecond diapason in all age groups are accompanied by short-time decelerations of the heart rhythms. In the minute diapason, there is observed a transition from positive connections in E17 and E18 to the negative ones in E19-20. Results of the study are considered in association with age-related changes of ratios of positive and negative oscillations of the heart rhythm change depending on the character of motor activity.     

Differential pattern of spinal sympathetic outflow in response to stimulation of the caudal medullary raphe

In urethan-anesthetized cats, frequency domain analysis was used to explore the mechanisms of differential responses of inferior cardiac (CN), vertebral (VN), and renal (RN) sympathetic nerves to electrical stimulation of a discrete region of the medullary raphe (0-2 mm caudal to the obex). Raphe stimulation in baroreceptor-denervated cats at frequencies (7-12 Hz) that entrained the 10-Hz rhythm in nerve activity decreased CN and RN activities but increased VN activity. The reductions in CN and RN discharges were associated with decreased low-frequency (相似文献   

Respiratory cycle timing and fast inspiratory discharge rhythms in the adult decerebrate rat

In supracollicular decerebrate paralyzed adult rats, neural respiration was monitored by bilateral phrenic recordings. In the study of respiratory cycle timing, the effects of vagal afferent input (lung inflation) on respiratory phase durations resembled those seen in decerebrate cats. 1) Withholding lung inflation during neural inspiration (I) produced lengthening of I phase duration by 46% (mean, n = 11). 2) Maintaining lung inflation during neural expiration (E) produced lengthening of E phase duration by 112% (mean, n = 4). In the study of fast rhythms in inspiratory discharges, phrenic nerve autospectra and bilateral (left-right) phrenic coherences in 16 rats revealed two types of fast rhythm: 1) high-frequency oscillation (HFO), which had significant coherence peaks (n = 9, range 106-160 Hz, mean 132 Hz); and 2) medium-frequency oscillation (MFO), which had autospectral peaks but no distinct coherence peaks (n = 11, range 46-96 Hz, mean 66 Hz). These rhythms resembled MFOs and HFOs in the decerebrate cat, but the modal frequency range was about twice as large. In addition, these frequency values differed markedly from the 20-40 Hz of the rhythms found in earlier studies in neonatal in vitro preparations; the difference may be due to developmental immaturity.     

Frequency characteristics of long-term heart rate variability during constant-routine protocol

The effects of such behavioral factors as physical activity, food intake, and circadian rhythm on long-term heart rate variability (HRV) in humans remain poorly understood. We therefore studied their effects on HRV using a constant-routine protocol that included simultaneous core body temperature (CBT) correction. Seven healthy subjects completed the constant-routine and daily-routine protocols, during which HRV and CBT were continuously monitored. During the constant routine, subjects were kept awake for 27 h in a semirecumbent posture with minimal physical activity; small isocaloric meals were provided every 2 h. During the daily routine, subjects carried on their lives normally. Data were analyzed using generic spectral analysis based on a fast Fourier transform; coarse-graining spectral analysis was also used to eliminate periodicity due to the regular meals for raw HRV and for the CBT-corrected HRV without circadian and/or low-frequency ultradian components. The results showed that 1) the power spectra of HRV in the constant routine and daily routine had similar power-law scalings at frequencies above approximately 10(-3.5) Hz, while 2) below that crossover frequency, HRV was smaller in the constant routine than in the daily routine, with the difference becoming significant (P < 0.05) at <10(-4) Hz, 3) coarse-graining spectral analysis eliminated diet-induced peaks in generic spectral analysis-based HRV spectra during the constant routine and emphasized the crossover at approximately 10(-3.5) Hz, and 4) CBT correction did not alter the results. Below a frequency of approximately 10(-3.5) Hz (a period >1 h), HRV is strongly influenced by behavioral factors; above that crossover frequency, HRV is behavior independent, possibly reflecting an intrinsic regulatory system.     

γ节律振荡机制在视觉研究中的新进展

γ节律振荡是大脑皮质中常见的,频率在30～80 Hz之间的神经振荡模式,在初级视觉通道中能观察到多种起源的γ节律振荡.在小鼠、猫与猴V1的视觉诱发的γ节律振荡主要起源于L2/3和L4B,并对刺激参数敏感.猫与小鼠初级视觉通道(视网膜、LGN与V1)中观察到起源于视网膜由亮度诱发的高频γ节律振荡;在猴LGN却没有观察到γ节律振荡,而在V1上记录到亮度诱发的γ活动.γ节律振荡的产生与抑制性中间神经元网络有重要的关系,其中抑制性中间神经元中PV细胞被认为与自发γ节律振荡的产生相关. SOM细胞的参与对低频γ节律振荡(20～40 Hz)的产生起到关键作用;而光栅诱发的高频γ节律振荡(65～80 Hz)主要与PV细胞有关.动物在不同生理状态、发育阶段与脑疾病状态下光栅诱发的γ节律振荡存在较大差异,反映大脑对视觉信息加工的变化.     

Role of sympathetic and parasympathetic mechanisms in formation of secondary cardiac rhythms in rats ontogenesis

In progeny of Wistar rats aged from birth to 3 week, there was studied participation of sympathetic and parasympathetic mechanisms in regulation of cardiac rhythm and its rhythmic oscillations (secondary cardiac rhythms), whose spectral composition was analyzed using rapid Fourier transformation. Consequences, which changed in the process of development, of blockade of -adrenoreceptors by propranolol, of -adrenoreceptors by phentolamine, and of muscarinic cholinoreceptors by atropine as well as of chronic desympathization by guanethidine (isobarine). It was found that due to heterochronia in establishment of functions of sympathetic and parasympathetic nervous systems, reactions to blockade of adreno- and cholinoreceptors for the first 3 weeks of postnatal ontogenesis changed not only quantitatively, but also qualitatively. Blockade of adrenoreceptors in newborn animals leads to an increase of power of the rhythm oscillations in all low-frequency diapasons. The baroreflex function of parasympathetic innervation is well expressed as early as in newborns. Tonic function with respect to frequency of heart rate and power of oscillations in the high-frequency diapason becomes evident only by the 3-week age.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 69–75.Original Russian Text Copyright © 2005 by Bursian, Sizonov, Semenova, Kulaev, Timofeeva, Polyakova, Dmitrieva.     

Mechanical modulation of atrial flutter cycle length

Although atrial flutter (AFL) is considered a highly regular rhythm, small fluctuations in cycle length have been described. The mechanisms responsible for these interval oscillations have been investigated by recent studies in humans which have shown that cyclic variations in atrial volume and pressure following ventricular contraction may account for the spontaneous variability of AFL. Other studies have shown that variations in the dimensions of the atria, caused by hemodynamical alterations due to imposed manoeuvres, directly modify the rate of AFL. All this evidence has led to the development of the mechano-electrical feedback (MEF) hypothesis, which assumes that changes in atrial volume directly affect AFL cycle length variability by modifying the conduction properties of the circulating impulse in the atrium.In the present study, we re-examined the variability pattern of typical AFL by spectral analysis aiming to support the MEF hypothesis for AFL cycle length variability. In a study population of 30 patients with typical AFL, we observed that AFL cycle length presented a spontaneous beat-to-beat variability, composed of two oscillations: a main oscillation at the frequency of ventricular contraction (1.70±0.48 Hz, spectral power: 15.4±17.6 ms²) and a second oscillation at the frequency of respiration (0.32±0.07 Hz, spectral power: 2.9±2.6 ms²). Both ventricular and respiratory oscillations persisted after pharmacologic autonomic blockade (ventricular spectral power: 17.7±14.7 ms² (before block) vs 20.2±18.3 ms² (after block), p=NS; respiratory spectral power: 6.0±3.8 ms² (before block) vs 5.0±3.4 ms² (after block), p=NS), suggesting a non-neurally mediated underlying mechanism. Contrary to respiratory modulation of heart rate during sinus rhythm, respiratory AFL cycle length oscillations displayed a reverse pattern, with longer cycle lengths during inspiration and shorter during expiration (AA_insp=223.2±28.6 ms vs AA_exp=221.1±28.2 ms, p<0.0005), which was consistent with a mechanical modulation of AFL reentry.The use of spectral analysis techniques applied to ventricular interval series and combined with computer simulations of atrioventricular conduction showed that the respiratory oscillation of atrial cycle length determined an oscillation in ventricular intervals with longer intervals during inspiration and shorter during expiration (VV_insp=639.9±186.0 ms vs VV_exp=634.8±182.9 ms, p<0.05). Ventricular interval oscillations resulted amplified by a factor 1.8 with respect to corresponding atrial cycle length oscillations. Thus, the mechanical fluctuations in AFL cycle length, although of small amplitude, might become clinically relevant through a magnified effect on ventricular variability.     

Gasping Generation in Developing Swiss–Webster Mice In Vitro and In Vivo

During hypoxia the respiratory network produces gasping in vivo and in vitro. To understand the mechanisms involved in such response and to validate in vitro findings, correlative studies are necessary. During perinatal age gasping generation is robust and then declines during postnatal development, possibly due to changes in either the rhythm generator (the pre-Bötzinger complex, PBC) and/or its motor outputs. We tested this hypothesis by recording respiratory response to hypoxia in vivo and in vitro during postnatal development. We found that postnatal age influences: (1) The hypoxia-induced pattern change in the PBC bursts, (2) The coupling between the PBC and the XII nucleus during prolonged hypoxia and (3) The ability of mice to gasp and autoresuscitate from hypoxic conditions. We conclude that the inability of mice to gasp during late postnatal development might be determined by a progressive uncoupling between the respiratory rhythm generator and its motor outputs in hypoxia.     

兔边缘系统背侧海马呼吸相关神经元

本工作对35只家兔在背侧海马区用玻璃微电极记录了103个神经元单位放电,分类如下:56个神经元属非呼吸节律性自发的间歇性放电,可分为两种类型:一为长时振荡型放电;另一为短时振荡型放电。47个神经元出现呼吸节律同步性自发放电,可分为三种类型:吸气型15个单位;呼气型9个单位;跨时相型23个单位。上述结果提示:边缘系统海马的呼吸信息在情绪活动的协调方面可能是一个有趣的问题。     

Contribution of the respiratory rhythm to sinus arrhythmia in normal unanesthetized subjects during positive-pressure mechanical hyperventilation

The precise contribution of the CO2-dependent respiratory rhythm to sinus arrhythmia in eupnea is unclear. The respiratory rhythm and sinus arrhythmia were measured in 12 normal, unanesthetized subjects in normocapnia and hypocapnia during mechanical hyperventilation with positive pressure. In normocapnia (41 +/- 1 mmHg), the respiratory rhythm was always detectable from airway pressure and inspiratory electromyogram activity. The amplitude of sinus arrhythmia (138 +/- 21 ms) during mechanical hyperventilation with positive pressure was not significantly different from that in eupnea. During the same mechanical hyperventilation pattern but in hypocapnia (24 +/- 1 mmHg), the respiratory rhythm was undetectable and the amplitude of sinus arrhythmia was significantly reduced (to 40 +/- 5 ms). These results show a greater contribution to sinus arrhythmia from the respiratory rhythm during hypocapnia caused by mechanical hyperventilation than previously indicated in normal subjects during hypocapnia caused by voluntary hyperventilation. We discuss whether the respiratory rhythm provides the principal contribution to sinus arrhythmia in eupnea.