电刺激腹中隔区对兔视前区前下丘脑温敏神经元放电的影响

目的和方法:采用玻璃微电极细胞外引导单位神经元放电的方法,观察电刺激兔腹中隔区(VSA)时,视前区-下丘脑前部(POAH)温度敏感神经元放电频率的变化。结果:电刺激腹中隔区可使视前区-下丘脑前部热敏神经元放电频率增加,冷敏神经元放电频率减少。结论:腹中隔区可能通过影响视前区-下丘脑前部温敏神经元放电频率而参与体温调节。     

电刺激POAH对IL-1β作用下兔VSA温敏神经元放电的影响

目的和方法:为了从细胞水平进一步探讨发热时体温正、负调节中枢的调节机制,本实验采用微电极细胞外记录技术,在26只新西兰兔脑腹中隔区(ventralseptalarea,VSA)记录了温敏神经元单位放电,观察电刺激下丘脑视前区(preopticanteriorhypothalamus,POAH)对致热原IL-1_β作用下兔VSA温敏神经元放电的影响。结果:(1)侧脑室注射的白介素-1_β(IL-1_β)能使VSA热敏神经元放电频率增加,冷敏神经元放电减少,而侧脑室注射等量人工脑脊液(ACSF)对热敏神经元和冷敏神经元的放电均无明显影响。(2)电刺激POAH可反转致热原IL-1_β对VSA热敏神经元和冷敏神经元的上述作用。结论:在致热原作用下的体温调节中,正调节中枢POAH和负调节中枢VSA具有密切的相互作用。     

Effects of high-rate electrical stimulation upon firing in modelled and real neurons

Many medical devices use high-rate, low-amplitude currents to affect neural function. This study examined the effect of stimulation rate upon action potential threshold and sustained firing rate for two model neurons, the rabbit myelinated fibre and the unmyelinated leech touch sensory cell. These model neurons were constructed with the NEURON simulator from electrophysiological data. Alternating-phase current pulses (0–1250 Hz), of fixed phase duration (0.2 ms), were used to stimulate the neurons, and propagation success or failure was measured. One effect of the high pulse rates was to cause a net depolarisation, and this was verified by the relief of action potential conduction block by 500 Hz extracellular stimulation in leech neurons. The models also predicted that the neurons would maintain maximum sustained firing at a number of different stimulation rates. For example, at twice threshold, the myelinated model followed the stimulus up to 500 Hz stimulation, half the stimulus rate up to 850 Hz stimulation, and it did not fire at 1250 Hz stimulation. By contrast, the unmyelinated neuron model had a lower maximum firing rate of 190 Hz, and this rate was obtained at a number of stimulation rates, up to 1250 Hz. The myelinated model also predicted sustained firing with 1240 Hz stimulation at threshold corrent, but no firing when the current level was doubled. Most of these effects are explained by the interaction of stimulus pulses with the cell's refractory period.     

Effects of pyrogen on the medullary temperature-responsive neurone of rabbits

Effects of intravenously injected endogenous pyrogen on the unit activity of temperature-responsive neurones (TR neurones) of medulla oblongata were investigated in urethanized rabbits with an intact or lesioned preoptic/anterior hypothalamic area (PO/AH). TR neurones of the medulla responded to pyrogen in the same manner as did those of the PO/AH; the firing rate in the warm-responsive neurones were depressed and the cold-responsive neurones augmented. However, one-fourth of the medullary TR neurones did not respond to pyrogen in the PO/AH intact group (the control group). Following lesion of the PO/AH, the relative frequencies of TR neurones affected by pyrogen decreased as compared with those in control, and such was suggested to be more apparent in TR neurones discharging at rates of 10 imp./sec or more. Effects of the PO/AH-lesion were also seen in that the magnitude of the facilitatory or inhibitory effect of pyrogen was reduced in the PO/AH-lesioned group as compared with the control group. In some TR neurones an antipyretic agent (Sulpyrine, 48--151 mg/kg) was found to abolish responses to pyrogen.     

Effects of percutaneous stimulation on motor unit firing behavior in man

Summary Motor unit firing behavior in human first dorsal interosseous (FDI) muscle was studied during controlled constant force isometric contractions. The threshold at which motor units were recruited and the mean firing rate at 50% of maximal voluntary contraction (MVC) were evaluated following stimulation of the skin area over the second digit. Stimulation of cutaneous receptors tended to increase the recruitment threshold of most of the motor units recruited under 20% MVC, while high-threshold motor units (those recruited over 30% MVC) generally exhibited a decrease in recruitment threshold. Less dramatic changes in motor unit firing rates were observed, but those motor units recruited over 30% MVC exhibited some increase in firing rate. The relationship between the change in recruitment threshold and change in motor unit firing rate is not rigid and seems to be susceptible to considerable synaptic noise.     

Effects of sympathetic stimulation on the rhythmical jaw movements produced by electrical stimulation of the cortical masticatory areas of rabbits

The somatomotor and sympathetic nervous systems are intimately linked. One example is the influence of peripheral sympathetic fibers on the discharge characteristics of muscle spindles. Since muscle spindles play important roles in various motor behaviors, including rhythmic movements, the working hypothesis of this research was that changes in sympathetic outflow to muscle spindles can change rhythmic movement patterns. We tested this hypothesis in the masticatory system of rabbits. Rhythmic jaw movements and EMG activity induced by long-lasting electrical cortical stimulation were powerfully modulated by electrical stimulation of the peripheral stump of the cervical sympathetic nerve (CSN). This modulation manifested itself as a consistent and marked reduction in the excursion of the mandibular movements (often preceded by a transient modest enhancement), which could be attributed mainly to corresponding changes in masseter muscle activity. These changes outlasted the duration of CSN stimulation. In some of the cortically evoked rhythmic jaw movements (CRJMs) changes in masticatory frequency were also observed. When the jaw-closing muscles were subjected to repetitive ramp-and-hold force pulses, the CRMJs changed characteristics. Masseter EMG activity was strongly enhanced and digastric EMG slightly decreased. This change was considerably depressed during CSN stimulation. These effects of CSN stimulation are similar in sign and time course to the depression exerted by sympathetic activity on the jaw-closing muscle spindle discharge. It is suggested that the change in proprioceptive information induced by an increase in sympathetic outflow (a) has important implications even under normal conditions for the control of motor function in states of high sympathetic activity, and (b) is one of the mechanisms responsible for motor impairment under certain pathological conditions such as chronic musculoskeletal head-neck disorders, associated with stress conditions.     

Effect of auricular electrical stimulation and naloxone on nociceptive sensitivity in rabbits

P. K. Anokhin Research Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR K. V. Sudakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 110, No. 10, pp. 339–341, October, 1990.     

Eye field in the cerebellar flocculus of pigmented rabbits determined with local electrical stimulation

The cerebellar flocculus was mapped with local stimulation techniques in alert pigmented rabbits. Triple-barrelled microelectrodes filled with solutions each containing one of three different dyes (Fast Green FCF, Pontamine Sky Blue and Nigrosine) were used for recording and stimulation. The H-zone from which local stimulation through the microelectrode induced abduction in the ipsilateral eye was visualized on the reconstructed model of the flocculus to span across major folia of the flocculus, forming a narrow strip 0.5-1.0 mm wide. The H-zone was flanked with two V-zones, rostral and caudal, from which downward eye movements were induced in the ipsilateral eye. The R-zone, from which clockwise rotation was induced in the contralateral eye, was extended rostrocaudally across the H- and V-zones. In addition to these eye movement-related zones, a restricted area specifically related to eye blinking was found in the rostroventral area of the flocculus.     

Implantable device for long-term electrical stimulation of denervated muscles in rabbits

Although denervating injuries produce severe atrophic changes in mammalian skeletal muscle, a degree of functional restoration can be achieved through an intensive regime of electrical stimulation. An implantable stimulator was developed so that the long-term effects of different stimulation protocols could be compared in rabbits. The device, which is powered by two lithium thionyl chloride batteries, is small enough to be implanted in the peritoneal cavity. All stimulation parameters can be specified over a wide range, with a high degree of resolution; in addition, up to 16 periods of training (10–180 min) and rest (1–42 h) can be set in advance. The microcontroller-based device is programmed through a bidirectional radiofrequency link. Settings are entered via a user-friendly computer interface and annotated to create an individual study protocol for each animal. The stimulator has been reliable and stable in use. Proven technology and rigorous quality control has enabled 55 units to be implanted to date, for periods of up to 36 weeks, with only two device failures (at 15 and 29 weeks). Changes in the excitability of denervated skeletal muscles could be followed within individual animals. Chronaxie increased from 3.24±0.54 ms to 15.57±0.85 ms (n=55, p<0.0001) per phase in the 2 weeks following denervation.     

Atherosclerosis induced in rabbits by prolonged electrical stimulation of the hypothalamus

The effect of prolonged electrical stimulation of emotiogenic zones of the hypothalamus in rabbits on their blood lipid level and the development of atherosclerosis was studied with the aid of a specially designed autonomous system. A negative emotional state observed during stimulation was accompanied by hyperlipemia and by the development of atherosclerosis in one third of uncastrated and two thirds of castrated animals.Department of Pathological Physiology and Central Scientific-Research Laboratory, Leningrad Sanitary Hygiene Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR P. N. Beselkin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1294–1296, November, 1976.     

Effects of long-term electrical stimulation on some contractile and metabolic characteristics of fast rabbit muscles

Summary Intermittant long-term stimulation of fast rabbit muscles up to 28 days with a frequency pattern resembling that of a slow muscle (10 Imp/sec) led to a slowing of the time course of contraction already during the first week. There was an increase of tetanic tension as well. The observed rearrangement of activities of key enzymes of energy supplying metabolism was found to occur sequentially. Decreases of extramitochondrial enzymes of glycogenolysis (phosphorylase), glycolysis (triosephosphate dehydrogenase, lactate dehydrogenase) and energy rich phosphate transfer were found initially together with a decrease of mitochondrial glycerolphosphate dehydrogenase. The isozyme pattern of lactate dehydrogenase was changed. Large initial increases were found in enzymes involved in glucose phosphorylation (hexokinase) and fatty acid activation (palmitoyl-CoA synthetase). Later an increase of key enzymes of the citric acid cycle (citrate synthase) and fatty acid oxidation (3-hydroxyacyl-CoA dehydrogenase) as well as ketone body utilization (3-ketoacid-CoA transferase) could be shown.Histochemical staining and comparative activity determination of succinate dehydrogenase in single fibres revealed that the mosaic like fibre composition of the fast muscle was transformed into a more uniform population resembling that of a predominantly slow muscle.This study was supported by grants from Medical Research Council, Deutsche Forschungsgemeinschaft and Deutscher Sportbund.     

Effects of transcutaneous short-term electrical stimulation on M. vastus lateralis characteristics of healthy young men

Fifteen healthy, untrained male subjects (mean age +/- SD, 22 +/- 5 years) were used to examine the plasticity of myosin heavy chain phenotype, size, oxidative capacity and capillarization of skeletal muscle fibre types with short-term electrical stimulation (ES). Ten subjects were electro-stimulated on both quadriceps muscles with a frequency of 45-60 Hz, with 12 s of stimulation followed by 8 s of recovery for a total of 30 min per day, 3 days per week for 6 weeks. The remaining five subjects served as controls. Two vastus lateralis muscle biopsy samples were removed from each subject before (week 0) and after (week 6) ES training. A standardized exercise test on a cycle ergometer was performed by each subject before and after the experimental period and several indicators of whole-body aerobic capacity were estimated. The so-called electromyographic threshold was also determined during the tests. Muscle biopsy samples were analysed by electrophoresis, immunohistochemistry and quantitative histochemistry. Myosin heavy chain (MHC) composition, muscle fibre type distribution, fibre areas, oxidative capacity and capillaries of each fibre type were estimated. Muscular changes with ES revealed an increase of fibres expressing MHC-IIA, and a decrease of fibres expressing MHC-IIX and MHC-I, as well as an increase of the oxidative capacity and mean number of capillaries of fast-twitch (type II) fibres with minimal muscle fibre hypertrophy. These adaptations seem related to a bi-directional transformation from both MHC isoforms I and IIX towards the MHC-IIA isoform. The aerobic performance and electromyographic variables at the whole-body level were not altered by ES. These results indicate that the particular short-term ES training protocol tested in the present study induces significant adaptations in histochemical and metabolic machineries of human skeletal muscle. The results also offer new perspectives for realistic applications of ES in various clinical situations and sport training.     

Changes in the probability of firing of motor units following electrical stimulation in human limb muscles

Changes in the probability of motor unit firing was studied in ten different muscles (six muscles in the upper extremity and four muscles in the lower extremity) of eleven healthy human subjects. The responses were elicited by the electrical stimulation of cutaneous or mixed nerves during weak voluntary contraction of the muscle studied, and were recorded by averaging the rectified surface electromyogram. In eight of the ten muscles, well-detectable, short and long latency excitatory phases were observed. The most constant and well-identified excitatory responses were observed in the first interosseus dorsalis muscle in the hand, and in the extensor digitorum brevis muscle in the foot. These two distal muscles seem to be the most useful muscles for routine determination of the short and long latency responses to cutaneous stimulation.     

Stability of firing patterns of hypothalamic neurons subjected to direct electrical or chemical stimulation

Summary The relationship between mean firing rate and activity pattern was studied in 177 neurons in the ventromedial hypothalamus of rats immobilized by Remyolan. Stationary epochs of spontaneous or stimulated activity containing at least 512 interspike intervals were analyzed with the LINC computer. The most frequently encountered interval histograms (IHs) were of the exponential (35%) or gamma 2 (25%) type. The IH shape remained unchanged even if the average firing rate was varied over a wide range (from 20/sec to 2/sec) by polarization through the recording microelectrode (2–5 nA, 1–10 min) or by intracarotid injection of glucose (0.1 ml, 10–25%). The coefficient of variation (CV = SD/ mean interval) was 1.03 for the spontaneous and 0.90 or 0.95 for the activity influenced by polarization or glucose, respectively. Since according to other studies sensory stimulation decreases CV by reorganization of the synaptic input, it is suggested that polarization and glucose affect predominantly the postsynaptic elements without significantly changing the presynaptic activity pattern.Visiting scientist from the Institute of Experimental Medicine, Academy of Medical Sciences, Leningrad, U.S.S.R.     

电刺激VSA对IL-1_β作用下兔POAH温敏神经元放电的影响

目的和方法：本实验采用微电极细胞外记录,在３２只新西兰兔下丘脑视前区（ＰＯＡＨ）记录温敏神经元单位放电,观察电刺激腹中膈区（ＶＳＡ）对致热原ＩＬ－１β作用下兔ＰＯＡＨ温敏神经元放电的影响。结果：（ｌ）侧脑室注射白介素－１β（ＩＬ－１β）能使ＰＯＡＨ热敏神经元放电减少,冷敏神经元放电增加;而侧脑室注射人工脑脊液（ＡＣＳＦ）对热敏神经元和冷敏神经元的放电均无明显影响。（２）电刺激ＶＳＡ可反转ＩＬ－１β对ＰＯＡＨ热敏神经元和冷敏神经元的上述作用。结论：ＶＳＡ可能作为负调节中枢参与致热原作用下的体温调节。     

电刺激VSA对IL-1β作用下兔POAH温敏神经元放电的影响关

目的和方法:本实验采用微电极细胞外记录,在32只新西兰兔下丘脑视前区(POAH)记录温敏神经元单位放电,观察电刺激腹中膈区(VSA)对致热原IL-1_β作用下兔POAH温敏神经元放电的影响。结果:(1)侧脑室注射白介素-1_β(IL-1_β)能使POAH热敏神经元放电减少,冷敏神经元放电增加;而侧脑室注射人工脑脊液(ACSF)对热敏神经元和冷敏神经元的放电均无明显影响。(2)电刺激VSA可反转IL-1_β对POAH热敏神经元和冷敏神经元的上述作用。结论:VSA可能作为负调节中枢参与致热原作用下的体温调节。     

Effects of external electrical stimulation on laser-beam-induced experimental thrombosis

External electrical stimulation (EES) has demonstrated venous antithrombotic properties. The aim of this investigation was to study its antithrombotic properties using unfractionated heparin (UFH) as a reference in arterial and venous mesenteric microvessels. For this purpose a rat model of laser-beam-induced thrombosis was used. Four groups of rats were investigated (n = 7): control, UFH (5 mg /kg), UFH (2.5 mg/kg) and electrical stimulation [e-vascular, E = 10, alternate polarity, in two protocols: (i) 30 min before and during thrombosis induction and (ii) only 30 min before thrombosis induction as preventive stimulation]. This effect was tested in arterial and venous microvessels in the four groups using the continuous protocol and only in arterial microvessels using the preventive protocol. Three parameters were studied: the number of laser beams needed to induce platelet thrombus formation, the number of emboli and the duration of embolization. Induced hemorrhagic time (IHT), platelet aggregation induced by ADP and coagulation tests (activated partial thromboplastin time, aPTT, prothrombin time, pTT, and fibrinogen level) were also determined. Continuous electrical stimulation decreased the number of emboli and the duration of embolization both in arterioles and in venules. It also significantly reduced the amplitude and velocity of the ex vivo platelet aggregation induced by ADP. Contrary to UFH, neither aPTT nor pTT were affected in platelet-poor plasma collected after the induction of thrombosis by laser beam, nor did it modify IHT. Preventive electrical stimulation produced similar results with fewer effects on induced venous thrombosis. These data suggest that EES has a potent antithrombotic effect on arterial and venous thrombosis without any hemorrhagic adverse effects, making it a very promising tool in the prevention and treatment of venous and arterial thromboembolic complications.     

Effects of neuromuscular electrical stimulation parameters on specific tension

This study examined the effects of altering surface neuromuscular electrical stimulation (SNMES) parameters on the specific tension of the quadriceps femoris muscle. Seven able-bodied subjects had magnetic resonance images taken of both thighs prior to and immediately after four SNMES protocols to determine the activated muscle cross-sectional area (CSA). The four protocols were: (1) research (RES, 100 Hz, 450 μs, and amplitude set to evoke 75% of maximal voluntary isometric torque, MVIT); (2) pulse duration (PD, 100 Hz, 150 μs, same current as in RES); (3) frequency (FREQ, 25 Hz, 450 μs, and same current as in RES); (4) amplitude (AMP, 100 Hz, 450 μs, and current set to evoke the average of the initial torques of PD and FREQ, 45 ± 9% of MVIT). Reducing the amplitude of the current from 75 to 45% of MVIT did not alter specific tension, 25 ± 8 N/cm², suggesting that the amplitude probably affects torque and the area of activated muscle proportionally. Shortening the pulse duration from 450 to 150 μs caused specific tension to drop from 25 ± 6 to 20 ± 6 N/cm² (P < 0.05), indicating that pulse duration increased torque and the activated CSA disproportionally. Alternatively, reducing the frequency from 100 to 25 Hz decreased specific tension from 25 ± 6 to 17 ± 4 N/cm² (P < 0.05), suggesting that the frequency increased torque without affecting the activated CSA. Clinicians who administer SNMES should be aware of the magnitude of adaptations to a given amplitude, pulse duration, and frequency.     

Formation of an endogenous pyrogen in normal and thyroidectomized rabbits

Summary As demonstrated in experiments on rabbits, a decrease of its pyrexial reaction following intravenous administration of bacterial lipopolysacchride (pyrogenal) was accompanied in thyroidectomized rabbits by reduction of the frequency of detection of endogenous pyrogen in the blood.Following daily administration of pyrogenal (for 7 days) in normal rabbits habituation (not immunological tolerance) to the preparation was revealed; no such state developed in thyroidectomized animals.The reaction to the administration of the same serum, containing endogenous pyrogen, was the same in intact and thyroidectomized animals.(Presented by Active Member AMN SSSR, P. F. Zdrodovskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 57, No. 4, pp. 49–51, April, 1964