电刺激兔脑干中缝背核引起呼吸易化效应的观察

本文在30只全麻、制动、断双侧迷走神经的家兔上,记录一侧膈神经放电,观察了电刺激脑干中缝背核(Nucleus Raphe Dorsalis,NRD)所诱发出的呼吸效应。1.施以6—10s 长串电脉冲刺激(波宽0.3ms,频率100Hz,波幅4—6V),诱发出了强的呼吸易化效应,使呼吸加深加快。2.吸气相给予0.4s 短串电脉冲刺激可以明显的延长吸气相,用0.15mA 强度刺激,落位在吸气相的2/3时效应最明显。3.呼气相短串电脉串刺激可规律地使呼气时程缩短,促进呼气向吸气的位相转换,诱发此效应出现的强度阈值在呼气相中逐渐降低。     

Electrical stimulation of the preoptic area in Eigenmannia: evoked interruptions in the electric organ discharge

The functional role of the basal forebrain and preoptic regions in modulating the normally regular electric organ discharge was determined by focal brain stimulation in the weakly electric fish, Eigenmannia. The rostral preoptic area, which is connected with the diencephalic prepacemaker nucleus, was examined physiologically by electrical stimulation in a curarized fish. Electrical stimulation of the most rostral region of the preoptic area with trains of relatively low intensity current elicits discrete bursts of electric organ discharge interruptions in contrast to other forebrain loci. These responses were observed primarily as after-responses following the termination of the stimulus train and were relatively immune to variations in the stimulus parameters. As the duration and rate of these preoptic-evoked bursts of electric organ discharge interruptions (approximately 100 ms at 2 per s) are similar to duration and rate of natural interruptions, it is proposed that these bursts might be precursors to natural interruptions. These data suggest that the preoptic area, consistent with its role in controlling reproductive behaviors in vertebrates, may be influencing the occurrence of electric organ discharge courtship signals by either direct actions on the prepacemaker nucleus or through other regions that are connected with the diencephalic prepacemaker nucleus. Accepted: 16 October 1999     

Effect of motor stimulation and stretching on afferent activity of the neuromuscular spindle isolated from the frog]

The arrangement of muscle spindles in m. ext. long. dig. IV has been examined by microdissection. It is confirmed that spindle systems generally appear to consist of individual receptors. Stimulation effects of fast motor fibres (conduction velocities greater than 12 m/sec) on the spindles of the same muscle were studied. Receptors were isolated with their nerves and the appropriate spinal roots, the latter ones were used for stimulating efferent fibres and recording sensory discharges. Single shocks to the ventral root filaments caused afferent responses ranging from a single action potential to a train of impulses. During repetitive stimulation (train of stimuli at frequency of 10 to 150/sec) a marked increase in afferent activity was found. Afferent activity could be driven by the frequency of stimuli ("driving") and the stimulus/action potentials ratio varied from 1:1 to 1:3 or more. The rate of sensory discharge depended on the frequency of stimuli: the maximum effect, was attained at 30 to 50 stimuli/sec and, in the most responsive receptors, up to 80 stimuli/sec. Slight increases of the initial lengths of the receptors caused facilitation of sensory responses to motor stimulation. Moreover, impairing effects, which appear during sustained or high-frequency stimulation, possibly related to fatigue in intrafusal neuromuscular transmission, could be relieved by increasing the initial length. The repetitive stimulation of fast fusimotor fibres increased both dynamic and static responses and also raised the afferent activity after a period of stretching, when usually a depression occurs; these effects varied according to the preparation, its initial tension and the frequency of stimulation. The main feature of the examined motor fibres, when stimulated, is the constant excitatory action on muscle spindle static response. Results are discussed. It is suggested that the different characteristics of intrafusal muscle fibres, the receptor initial tension and the frequency of motor units discharges, may together affect muscle spindles static or dynamic performance.     

延髓腹外侧Boetzinger复合体呼吸时相转换效应的研究

The effects of electrical stimulation of B?tzinger complex (Bot.C) on respiratory rhythm were investigated in 40 urethane anesthetized adult rabbits. The results were as follows. (1) A short train stimulation delivered in the early inspiratory phase produced a transient inhibition of phrenic discharge. The stimulus, when delivered in the mid or late inspiratory phase, could cause a premature termination of the inspiratory phase ("inspiratory off-switch") and a switching to the expiratory phase, which was accompanied with the reduced duration of the consecutive expiratory phase. There was a negative linear correlation between the threshold intensity of inspiratory off-switching and delivery time of stimulation. (2) A short train stimulation delivery in the expiratory phase elicited a transient phrenic discharge. The discharge in the late expiratory phase was followed by a premature onset inspiration. This effect was also dependent on the strength and delivery time of the stimulus. The results suggest that the Bot.C is involved in the central control of respiratory phase-switching.     

Effects of stimulus parameters on cardiovascular responses to medullary stimulation in the cat

The results of this study indicated that when stimulus intensity, pulse frequency and train duration were varied the basic topography of the cardiovascular responses to medullary stimulation did not change, but was merely increased or diminished in magnitude. Pressor responses were usually obtained in conscious cats, and also narcosis produced reversal effect on rare occasions. It is suggested that the reversal in cardiovascular responses is probably locus specific, and the medullary loci yielding reversal effect are more limited than those eliciting consequently pressor responses.     

电和L—谷氨酸钠刺激兔中缝隐核对膈神经放电的影响

实验在45只麻醉、自主呼吸、断双侧颈迷走神经的家兔上进行。电刺激或微量注射L-谷氨酸钠于中缝隐核(Nucleus raphe obscurus,NRO),观察到:(1)长串电脉冲刺激NRO(50—200μA,波宽0.3ms,100Hz,4—6s),出现膈神经放电被抑制的反应,被抑制的程度与刺激强度、刺激频率间存在相关性。(2)吸气期用短串电脉冲(100—200μA,波宽0.3ms,50—100Hz,5—20个脉冲)刺激NRO,可提前终止膈神经放电,产生吸气切断效应。吸气切断时间具有刺激落位和刺激强度依赖性。(3)NRO内微量注射细胞体兴奋剂谷氨酸钠(1mol/L,1μl),注药期间出现膈神经放电抑制,注药后为吸气时程(Ti)缩短和呼气时程(Te)延长。     

Effect of transcutaneous transcerebral electrostimulation as electroanesthesia on the beta-endorphin content of the cerebrospinal fluid and blood plasma

The beta-endorphin content was measured in the cerebrospinal fluid (CSF) and blood plasma of patients before and after 30 minutes of transcutaneous transcerebral electric stimulation in the electric anesthesia mode. The output current was biphasic and rectangular. It was composed of high-frequency pulse trains (peak-to-peak intensity 250-300 mA, frequency 167 kHz) modulated by low frequency (77 Hz). Electrical stimulation resulted in an appreciable increase in the beta-endorphin content in the CSF and blood plasma of patients. The data obtained attest to the intensification of the neuromodulator release to the CSF and blood plasma and to the involvement of the endorphinergic brain systems in the realization of the analgetic effect of transcutaneous transcerebral electric stimulation.     

‘Communication’ in weakly electric fish, Gnathonemus niger (Mormyridae) I. Variation of electric organ discharge (EOD) frequency elicited by controlled electric stimuli

The weakly electric fish, Gathonemus niger, discharged with a frequency of 4 to 8 Hz during the day and 10 to 16 Hz during the night. The frequency of superimposed burst discharges (32 to 56 Hz) was independent of diurnal factors. The variation of the electric organ discharge frequency during the day was investigated in response to controlled electric stimulus patterns: (a) A free running stimulus frequency of 4 Hz, simulating the resting frequency of another fish, and different stimulus intensities, simulating different distances between two fish. (b) Free running frequencies of 4, 8, 16, …, 128 Hz and two particular stimulus intensities. (c) Discharge coupled stimuli (each discharge triggered an electric stimulus with a fixed delay) and different stimulus intensities.All three kinds of stimuli elicited defined and predictable response discharge patterns supporting the assumption that an electric fish would respond to a particular discharge pattern of another fish also in a similar and predictable manner. Low stimulus intensities (0·04 to 0·2 mV per cm) caused cessation of the discharge activity, a ‘hiding’ or ‘listening’ response. The discharge rate increased linearly with the logarithm of the stimulus intensity. The fish was particularly sensitive to stimulus frequencies which simulated its burst activity (32 to 56 Hz). Discharge coupled stimuli showed that the fish responded to about eight times lower stimulus intensities if the stimulus occurred between two discharges (15 to 30 m-s after the fish's discharge) than if the stimulus occurred within or immediately after the discharge. All suprathreshold stimuli elicited a typical discharge pattern: The irregular resting discharge activity became significantly regular. The degree of regularity was even improved during maintained stimulation. The regularisation of the discharge activity is thought to be involved in the fish's electrolocating system whereas frequency variations are considered as being involved in both the locating system and as communication signals among weakly electric fish.     

Stabilometry and definition of the threshold of galvanic vestibular stimulation in normal subjects: an experimental study

The effect of the galvanic stimulation on the vestibular apparatus has been evaluated by registration on the postural deviations, using a stabilometry platform. We have studied the galvanic body-sway responses in a group of normal subjects, using a binauricolar bipolar stimulation, with the electrodes attached by means of surgical tape to the mastoid area. The records of body-sway responses have demonstrated in 80% of the considered cases a significant variation of all positional parameters after a current intensity of 2 mA, according the body sways toward the positive stimulus. At the same current intensity only five of the studied subjects have shown multidirectional swinging, in three cases joined with a subjective slight sway toward the ear stimulated with positive polarity. Therefore the galvanic test, joined with the posturography, proves to be a useful auxiliary method in vestibular investigation, allowing us to lower the threshold of galvanic stimulation and to make the electric stimulus better supported for the patient.     

Frequency-dependent response of SI RA-class neurons to vibrotactile stimulation of the receptive field

Three types of experiment were carried out on anesthetized monkeys and cats. In the first, spike discharge activity of rapidly adapting (RA) SI neurons was recorded extracellularly during the application of different frequencies of vibrotactile stimulation to the receptive field (RF). The second used the same stimulus conditions to study the response of RA-I (RA) cutaneous mechanoreceptive afferents. The third used optical intrinsic signal (OIS) imaging and extracellular neurophysiological recording methods together, in the same sessions, to evaluate the relationship between the SI optical and RA neuron spike train responses to low- vs high-frequency stimulation of the same skin site. RA afferent entrainment was high at all frequencies of stimulation. In contrast, SI RA neuron entrainment was much lower on average, and was strongly frequency-dependent, declining in near-linear fashion from 6 to 200 Hz. Even at 200 Hz, however, unambiguous frequencyfollowing responses were present in the spike train activity of some SI RA neurons. These entrainment results support the "periodicity hypothesis" of Mountcastle et al. ( J Neurophysiol 32: 452-484, 1969) that the capacity to discriminate stimulus frequency over the range 5-50 Hz is attributable to the ability of SI RA pyramidal neurons to discharge action potentials in consistent temporal relationship to stimulus motion, and raise the possibility that perceptual frequency discriminative capacity at frequencies between 50 and 200 Hz might be accounted for in the same way. An increase in vibrotactile stimulus frequency within the range 6-200 Hz consistently resulted in an increase in RA afferent mean spike firing rate (M FR). SI RA neuron M FR also increased as frequency increased between 6 and 50 Hz, but declined as stimulus frequency was increased over the range 50-200 Hz. At stimulus frequencies > 100 Hz, and at positions in the RF other than the receptive field center (RF center ), SI RA neuron MFR declined sharply within 0.5-2s of stimulus onset and rebounded transiently upon stimulus termination. In contrast, when the stimulus was applied to the RF center, MFR increased with increasing frequency and tended to remain well maintained throughout the period of high-frequency stimulation. The evidence obtained in "combined" OIS imaging and extracellular microelectrode recording experiments suggests that SI RA neurons with an RF center that corresponds to the stimulated skin site occupy small foci within the much larger SI region activated by same-site cutaneous flutter stimulation, while for the RA neurons located elsewhere in the large SI region activated by a flutter stimulus, the stimulus site and RF center are different.     

Excitatory postsynaptic potentials of hippocampal neurons and their extinction during repeated stimulation

A method of detecting "minimal" excitatory postsynaptic potentials (EPSP) in neurons of hippocampal area CA₃ of the unanesthetized rabbit during stimulation of the septo-fimbrial region and the dentate fascia is described. The method consists of presenting a strong (a current of up to 1 mA) conditioning stimulus, inducing a distinct inhibitory postsynaptic potential (IPSP), before a near-threshold (current of 0.03–0.35 mA) testing stimulus. The response to the testing stimulus, develoing after the previous conditioning IPSP, in most cases was purely depolarizing and, judging from the change in the latent period in some cases and the absence of correlation between its amplitude and that of the IPSP, it is a pure EPSP. If the testing stimuli are presented at low enough frequency (intervals of not less than 1 sec) the amplitude of the EPSP evoked by them gradually falls. This decrease exhibits some of the characteristic properties of extinction of behavioral responses (recovery after an interruption, a more rapid decrease during repeated series of stimuli, a slower decrease in amplitude during less frequent stimulation). The amplitude of the IPSP also fell or showed no significant change. The results are evidence in support of the hypothesis that extinction is based on a mechanism of homosynaptic depression.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 3–12, January–February, 1978.     

The behavior of rats with different regimes of cerebral self stimulation]

The behaviour of rats was studied during electrical self-stimulation (SS) of the brain in a chamber with a pedal: with a fixed duration of stimuli trains (fixed SS regime), and in a self-controlled regime, where the duration of trains was set by the rat itself. As the current intensity or the duration of the trains continues to increases, the SS frequency in the fixed regime rises no longer. The duration of pressing becomes shorter than that of the trains, and the number of short pauses drops down to 50% of its total number of pauses, if at the same current intensity the duration of the train is the same or greater than that set by the rats in the self-controlled SS regime. With weak current intensities, the rats could fail to press the pedal if they received 0.1 sec. trains. But at the same current intensities the rats began SS, if they received for pressing the pedal a succession of trains of 0.1 sec. each with intervals of 0.1 divided by 0.2 sec. SS discontinued if the interval in the trains succession increased up to 0.4 sec.     

Cross-correlation analysis of unit activity in spinal locomotor centers

Correlation analysis of unit activity in spinal locomotor centers was carried out in immobilized thalamic cats. Within a short time interval (the time shift of one spike train relative to the other during plotting of the cross-correlation histogram did not exceed 54 msec) correlation between the spike flows of these cells was absent, irrespective of the distance between them, both at rest and during efferent discharge generation. Spike flows of neurons could correlate only in the case of a long time interval (maximal time shift of one spike train relative to the other not less than 4–8 sec during plotting of the cross-correlation histogram). Weak correlation with a long time interval (4–8 sec) was found between changes in the momentary frequency of a neuron and the intensity of the discharge in the motor nerve, but no correlation was found between changes in momentary frequency of the neuron and intensity of discharge. The possible causes of the absence of correlation with a short time interval and its presence with a long time interval are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 3, pp. 283–289, May–June, 1980.     

Dependence of the Magnitude of Postural Reactions in Humans on the Strength of Unilateral Galvanic Anodal and Cathodal Vestibular Stimulations

In 13 healthy volunteers, we recorded stabilographic postural reactions (side inclinations of the body) to unilateral galvanic vestibular stimulation (GVS) by rectangular current pulses (4 sec long, 2, 3, 4, 5, or 6 mA). For the cathodal GVS, the dependence of the magnitude of reaction was linear within this range. The corresponding dependence for the anodal GVS was close to linear at small currents, but the increment of the magnitude became smaller with further increase in the stimulation intensity, and a plateau was formed. A significant divergence between the two curves was observed with stimulation currents 4 mA and higher. This difference can be explained considering modern concepts on the mechanism of GVS-induced effects (an increase or a decrease in the level of tonic impulsation in fibers of the vestibular nerve under the influence of polarization). Anodal GVS continues to suppress tonic activity up to the moment where all GVS-sensitive vestibular afferents stop to generate impulses; a further increase in the intensity of hyperpolarizing current is not accompanied by a decrease in the activity in the vestibular nerve and, consequently, by an increase in the magnitude of postural reactions. The tested approach can be used for qualitative estimation of the vestibular tone in humans. Neirofiziologiya/Neurophysiology, Vol. 37, No. 2, pp. 169–176, March–April, 2005.     

Electric organ discharge frequency modulation evoked by water vibration in Gymnotus carapo

• 1.1. The electric organ discharge (EOD) frequency modulations evoked by brief water vibration were analysed in the pulse-type fish Gymnotus carapo.
• 2.2. The response consisted of a transient increase of the EOD frequency at short latency (30 msec). Response profiles were characteristic of the specimen and relatively independent on stimulus intensity.
• 3.3. Conversely, they were dependent on stimulation sequence, showing a rapid decrement along successive stimuli and high temporal discrimination.
• 4.4. The brief latencies indicate a relatively simple neural circuit.
• 5.5. The response may be an electrolocation enhancement strategy for the detection of moving objects based on “sampling” the periphery at a higher frequency.

     

Adiabatic solution for the Ohmic cable equation. An homogeneous cell, prospects for electronic measurements]

Exact and adiabatic electrotonic solutions [1] were calculated for reconstructed motoneurone and hippocampal interneurone in case of linear and exponential ramp stimulation by the fixed current, potential or homogenous electric field. For the rising exponential ramp the solutions are identical. In case of the decaying exponent the adiabatic solution becomes an asymptote for the exact one if the stimulus decays slower than relaxation of the initial conditions in the cell. If the stimulus decays faster, the asymptote is the current or potential axis, depending on the stimulation mode. For electrotonically short cell, the exact solution approaches the asymptote faster. The solution for the exponentially rising field does not depend on the dendritic tree configuration and depends only on the effective electrotonic length of the neurone. It could be useful to apply ramp stimulation, especially exponential ramp of the electric field, to estimate electrotonic parameters of cells.     

Responses of rabbit visual cortical neurons to intracortical electrical stimulation

Responses of rabbit visual cortical neurons to single and repetitive intracortical electrical stimulation were investigated. The stimulating electrode was located 0.7–1.2 mm away from the recording electrode. Response thresholds to single stimulation were as a rule 150–180 µA, whereas to series of stimuli they were 30–60 µA. The latent period to the first spike averaged 5–15 msec but the probability of the initial discharge was very low, namely 3–6%. With an increase in current intensity the duration of the initial inhibitory pause was increased in half of the neurons responding to it, whereas in the rest it was unchanged. After presentation of series of stimuli spontaneous activity was enhanced for a short time (4–6 sec). In about half of the cells the same kinds of discharge dynamics were observed in response to repetitive stimulation (frequency 0.25 Hz) as in responses to light, but more neurons with sensitization of discharge and fewer "habituating" neurons took part in responses to electrical stimulation. It is postulated that stimulation of a given point of the visual cortex evokes excitation of a local neuron hypercolumn and inhibition of neighboring cell columns.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 412–419, July–August, 1983.     

电刺激家兔迷走神经中枢端诱导的黑-伯反射中的非联合型学习现象

本文旨在研究电刺激家兔迷走神经诱导的黑-伯（Hering-Breuer,HB）反射中的学习和记忆现象。选择性电刺激家兔迷走神经中枢端（频率10～100Hz,强度20～60μA,波宽0．3ms,持续60s）,观察对膈神经放电的影响。以不同频率电刺激家兔迷走神经可模拟HB反射的两种成分,即类似肺容积增大所致抑制吸气的肺扩张反射和类似肺容积缩小所致加强吸气的肺萎陷反射。（1）长时高频（≥40Hz,60s）电刺激迷走神经可模拟呼吸频率减慢,呼气时程延长的肺扩张反射。随着刺激时间的延长,膈神经放电抑制的程度逐渐衰减,表现为呼吸频率的减慢（主要由呼气时程延长所致）在刺激过程中逐渐减弱或消失,显示为适应性或“习惯化”的现象;刺激结束时呼吸运动呈现反跳性增强,表现为一过性的呼气时程缩短,呼吸频率加快,然后才逐渐恢复正常。长时低频（〈40Hz,60s）电刺激迷走神经可模拟呼吸频率加快、呼气时程缩短的肺萎陷反射。随着刺激时间的延长,膈神经放电增强的程度逐渐衰减,同样表现出“习惯化”现象;刺激结束后,膈神经放电不是突然降低,而是继续衰减,表现为呼气时程逐渐延长,呼吸频率逐渐减慢,直至恢复到前对照水平,表现了刺激后的短时增强效应。（2）HB反射的适应性或“习惯化”程度反向依赖于刺激强度和刺激频率,表现为随着刺激强度和频率的增加,膈神经放电越远离正常基线水平,即爿惯化程度减弱。结果表明,家兔HB反射具有“习惯化”这一非联合型学习现象,反映与其有关的呼吸神经元网络具有突触功能的可翅性,呼吸的中枢调控反射具有一定的适应性。     

The relative sensitivity of Renshaw cells to orthodromic group Ia volleys caused by static stretch and vibrations of extensor muscles.

1. Activity of Renshaw cells monosynaptically excited by ventral root stimulation and disynaptically excited by electric stimulation of the group Ia afferents in the gastrocnemius-soleus (GS) nerve, was recorded in precollicular decerebrate cats. The response of these units to prolonged vibration applied longitudinally to the deefferented GS muscle was then compared with that elicited by static stretch of the homonymous muscle, for comparable frequencies of discharge of the group Ia afferents. 2. Small-amplitude vibration of the GS muscle at 200/sec for one second produced a sudden increase in the discharge rate of Renshaw cells, which gradually decreased within the first 100 msec of vibration to reach steady albeit lower level than that obtained during the first part of vibration. The response of the Renshaw cells during the first 100 msec of vibration (phasic response) and that elicited during the last 500 msec of vibration (tonic response) were evaluated for different frequencies of sinusoidal stretch. The mean increase in the firing frequency per imp./sec in the Ia afferents was also calculated using the total one-second period. 3. The response of Renshaw cells to muscle vibration increased with the frequency of vibration and, over the value of 10/sec, appeared to be linearly related to the frequency of the input, at least up to the frequency of 150/sec. Since vibration was of sufficient amplitude to produce driving of all the primary endings of muscle spindles, the responses were expressed as mean increases in the discharge rate of Renshaw cells per average impulse/sec in the Ia afferents. The discharge of the Renshaw cell increased on the average by 2.90 and 1.08 imp./sec per each imp./sec in the Ia afferents during the phasic and the tonic component of the response respectively, while the response calculated during the whole period of vibration corresponded on the average to 1.45 imp./sec per each imp./sec in the Ia afferents. 4. The Renshaw cells tested above responded also with increasing frequencies of discharge to increasing levels of static extension of the GS muscle. In particular the discharge frequency of Renshaw cells was on the average linearly related to muscle extension, at least for values ranging from 0 to 8 mm. The mean increase in discharge rate as a function of the static extension corresponded on the average to 0.89 imp./sec/mm. Since the discharge rate of the primary endings of muscle spindles recorded from the deefferented GS muscle increased by 2.62 imp./sec/mm, it appears that the mean increase in the discharge rate of Renshaw cells as a function of static extension corresponded to 0.34 imp./sec per each imp./sec in the Ia afferents.     

Relationship between the resting blood pressure and depressor responses evoked by stimulation of the aortic nerve.

Correlations between the resting blood pressure and magnitude of depressor responses evoked by graded stimulation of the aortic nerve, were studied in rabbits anaesthetized with urethane. The strength of stimulation ranged from 1 to 10 times the threshold, and activated the myelinated afferents. The frequency of stimulation was 5 and 50 cycles/sec. At lower frequency of stimulation the correlations become significant when the intensity of stimulation is 3 times the threshold and they increase at the highest strengths of stimulation. Correlation coefficients calculated for responses obtained at the frequency of 50 cycles/sec are significant in 8 out of 9 intensities of stimulation. With increase in the strength of stimulation they increase, attain their maximum at twice the threshold and decrease at the largest used stimulus strengths. The changes in the values of the correlation coefficients are not paralleled by alterations in the mean size of depressor responses. Since all correlation coefficients are positive, it is inferred that the depressor responses produced by stimulation of the aortic nerve follow WILDER's "law of initial value". The conformity with this rule is the better the higher the values of the correlation coefficients. The strength of relationship between the resting blood pressure and the size of depressor responses is considered to reflect the efficiency of the homeostatic circulatory mechanism.