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PubMed1984

Vascular effects of free radicals generated by electrical stimulation.

Electrical field stimulation (9 V, 1.0 ms, 4 Hz) of isolated segments of rat tail arteries and dog coronary arteries inhibits contractile responses to exogenous norepinephrine and elevated potassium concentration. This inhibitory effect of electrical stimulation is blocked by various agents that alter oxygen metabolism: superoxide dismutase, catalase, glutathione, ascorbate, and dimethyl sulfoxide. The observations suggest that the inhibitory effect is due to an action of oxygen free radical metabolites that are generated by the electrical stimulation of the oxygen-rich buffer. These free radical metabolites have two actions: 1) they oxidize drugs in the experimental system, and 2) they exert a direct inhibitory action on vascular smooth muscle.

Animals↗
PubMed2000

Integrin-dependent human macrophage migration induced by oscillatory electrical stimulation.

Electrical stimulation has been used to promote wound healing. The mechanisms by which such stimulation could interact with biological systems to accelerate healing have not been elucidated. One potential mechanism could involve stimulation of macrophage migration to the site of a wound. Here we report that oscillatory electric fields induce human macrophage migration. Macrophages exposed to a 1 Hz, 2 V/cm field show an induced migration velocity of 5.2+/-0.4 x 10(-2) microm/min and a random motility coefficient of 4.8+/-1.4 x 10(-2) microm2/min on a glass substrate. Electric field exposure induces reorganization of microfilaments from ring-like structures at the cell periphery to podosomes that are confined to the contact sites between cell and substrate, suggesting that the cells are crawling on glass. Treatment of cells with monoclonal antibodies directed against beta2-integrins prior to field exposure prevents cell migration, indicating that integrin-dependent signaling pathways are involved. Electric fields cause macrophage migration on laminin or fibronectin coated substrates without inducing podosome formation or changes in cellular morphology. The migration velocity is not significantly altered but the random movement is suppressed, suggesting that cell movements on a laminin- or fibronectin-coated surface are not mediated by cell crawling. It is suggested that electric field-induced macrophage migration utilizes several modes of cell movement, including cell crawling and possibly cell rolling.

Cell Movement↗
PubMed1986

Electrical responses of the smooth muscle of the guinea-pig cerebral artery to brief electrical stimulation.

Electrical responses to brief electrical stimulation were investigated in the cerebral artery of a guinea-pig using a microelectrode. A single brief stimulus (0.05 ms) induced a spike potential followed by a depolarizing slow-potential, and these events were associated with muscle contraction. An outward current injected into the smooth muscle cell induced spike potential but failed to induce depolarizing slow-potential. These activities persisted in the presence of TTX (10(-6) M), guanethidine (5 X 10(-6) M), or atropin (10(-5) M). TEA (5 mM) enhanced the amplitude of the spike potential, but not that of the depolarizing slow-potential. When the external Na was reduced, the membrane transiently hyperpolarized. During this period, the depolarizing slow-potential could be evoked. In a Cl-deficient solution, the membrane depolarized and the amplitude of the depolarizing slow-potential decreased. From these observations it is believed that the contribution of K, Na, or Cl is minor. In a 20 mM-Ca solution, a brief stimulation induced neither spike potential nor depolarizing slow-potential, but did induce a hyperpolarizing slow-potential. The hyperpolarizing slow-potential was also induced in a Na-deficient solution, but only after completion of Na re-distribution across the membrane. These observations suggest that a substance released by brief stimulation produces a prolonged change in ionic conductances of the smooth muscle membrane, allowing the muscle to contract for a certain period.

Animals↗
PubMed1990

Two theories of muscle strength augmentation using percutaneous electrical stimulation.

Electrical stimulation of muscle is a commonly used, well-substantiated strategy that physical therapists use to augment strength in patients with muscle weakness. Two distinctly different theories of strength augmentation using percutaneous muscle stimulation are presented. The first theory proposes that augmentation of muscle strength with electrically elicited muscle contractions occurs in a similar manner to augmentation of muscle strength with voluntary exercise. Electrically elicited muscle contractions of relatively high intensity with low numbers of repetitions strengthen muscle proportionally to the external load on the muscle in a manner that is equivalent to voluntary contraction. The second theory proposes that augmentation of muscle strength using percutaneous stimulation is fundamentally different from augmentation of strength with voluntary exercise. This theory uses the physiological differences between electrically elicited and voluntary contractions, such as the reversal of motor unit recruitment order, as a basis for argument. Both theories are partially substantiated using published literature. Strategies for testing both theories are also presented.

Electric Stimulation Therapy↗
PubMed1999

Functional magnetic resonance imaging of the human motor cortex before and after whole-hand afferent electrical stimulation.

Electrical stimulation of the whole hand using a mesh-glove has been shown to improve volitional movement of the hand and arm, and decrease muscle hypertonia after hemispherical stroke in patients who have reached a recovery plateau. The goal of this study was to investigate the effect of stimulation of the nerve afferents of the hand on brain cortical activity elicited by whole-hand subthreshold stimulation for sensation in humans with intact nervous systems. Brain cortical activity in 6 healthy subjects (30-45 years) was studied using blood oxygenation level-dependent functional Magnetic Resonance Imaging during a test motor task, finger-to-thumb tapping and after 20 minutes of mesh-glove stimulation of the resting hand prior to performance of an identical motor task, to test the changes in the conditioned motor task established after 20 minutes of mesh-glove stimulation. Fifteen contiguous echo-planar sequences parallel to the bicommissural plane were acquired for functional magnetic resonance. Post-processing of image data included correction of motion artefacts and calculation of correlation coefficients between the signal intensity of pixels during rest and finger tapping and a rectangular reference wave function. The functional Magnetic Resonance Imaging examinations revealed a signal increase in the primary and secondary motor and somatosensory areas when comparing the number of activated pixels during test and conditioned motor tasks. Our preliminary study indicated that change occurred in a definite pattern in the region of the regional cerebral blood flow of the brain cortex after mesh-glove whole-hand stimulation at the subthreshold level for sensation. We assumed that this increase in regional cerebral blood flow also reflected augmented neuronal activity.

Adult↗
PubMedDate not supplied

Skeletal muscle carbohydrate metabolism during short-term and prolonged in vivo electrical stimulations.

Electrical stimulations were applied to the gastrocnemius muscle of intact frog. Rana hexadactyla (Lesson) for short-term (SMS) and prolonged (PMS) periods. Short-term muscular stimulations resulted in decreased glycogenolysis and glycolysis with depleted glycogen and lactic acid contents in the muscles and increased lactic acid content in the blood. The activity levels of SDH and MDH were decreased in SMS muscles. Prolonged muscular stimulations, on the other hand, increased glycogenolysis and glycogenolysis was suggested to be due to stepped-up glycogenesis. Tissue oxidative metabolism was also correlated with regulation of activities of enzymes concerned with anaerobic pathways.

Animals↗
PubMed1967

Lateral hypothalamus: hoarding behavior elicited by electrical stimulation.

Electrical stimulation of those points in the lateral hypothalamic area of the brain that promote feeding, but not of other points, elicited intense hoarding activity in satiated rats, similar to that produced by long-term food deprivation. This result suggests that hoarding of food is organized by a hypothalamic drive mechanism sensitive to the efflects of long-term nutritional depletion.

Animals↗
PubMed1982

Striatal 3-methoxytyramine as an index of dopamine release effects of electrical stimulation.

Electrical stimulation of the substantia nigra elicited frequency-dependent increases in striatal 3-methoxytyramine (3-MT). Subsequently, successive increases in dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured. Inhibition of nigrostriatal cell firing with HA-966 resulted in decreased striatal 3-MT, but in this case elevated DOPAC and HVA were also observed. These data indicate that 3-MT is a reliable index of dopamine (DA) release but that concurrent measurements of DOPAC, HVA and DA provide the most reliable interpretation of drug effects on dopaminergic function.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Theoretical determination of the current density distributions in human vertebral bodies during electrical stimulation.

Electrical stimulation with a 60 kHz sinewave input signal, supplied via external plate electrodes on the skin surface, is presently being studied as a treatment for human systemic osteoporosis. In this paper, Maxwell's equations were solved for voltage and current density values at nodal points in a three-dimensional, anatomically-based, finite element grid model of the human trunk constructed from T5 to L5. Based on the dose response results from Luessenhop's castrated Sprague Dawley breeder rat experiment and our theoretical determination, the magnitude of the input current to the electrodes necessary to induce a response in the human vertebral body was determined. Four different electrode systems in current clinical use were evaluated, and the optimal input current determined. In addition, the effect of subcutaneous fat was studied.

Adipose Tissue↗
PubMed1997

Conversion of beating mode in Chlamydomonas flagella induced by electric stimulation.

Electric stimulation of a single Chlamydomonas cell by means of a suction electrode induced a temporary conversion of flagellar waveform from an asymmetric forward mode to a symmetric reverse mode. The reverse mode continued for about 0.5 seconds, after which the forward mode was resumed. Anodic stimulation (current passing outward through the membrane outside the suction pipette) was more effective in inducing the flagellar response than cathodic stimulation. No flagellar response was induced in the absence of free Ca2+ or in the presence of calcium channel inhibitors, pimozide (5 microM) and diltyazem (0.3 mM). These findings indicate that the flagellar response by membrane depolarization followed by a Ca2+ influx through voltage-dependent calcium channels. This experimental system allowed us to quantitatively analyze the behavior of flagella during the waveform conversion. The flagellar bending pattern quickly changed from the forward mode to the reverse mode and, thereafter, gradually resumed the forward mode through two discrete phases: changes during reverse mode beating (phase I) and a distinct transitional phase (phase II). Recovery in curvature and sliding velocity of principal bends occurred mostly in phase I. Almost all of the recovery of reverse bends, returning the curvature to the low values characteristic of asymmetric forward mode beating, occurred in phase II. Beat frequency recovered through both phases. Phase II was often interrupted by a temporary stoppage of beating. These findings indicate that the bending pattern is converted through multiple steps that are controlled by Ca2+.

Animals↗
PubMed1995

Which structures are sensitive to painful transcranial electric stimulation?

Electric transcranial stimulation (TCS) is useful for clinical studies. It is, however, painful and not generally used for awake subjects. By means of topical anaesthesia and nerve blockades we wanted to find out which structures of the scalp and cranium are sensitive to electric TCS. Altogether 21 subjects participated in the present study. Our data show that pain experienced by the subjects during electric TCS is brought about by activation of the pain receptors in the scalp under the stimulating electrodes. Topical anaesthetic cream is incapable of attenuating this pain. The periosteum does not seem to be much more sensitive electric stimulation than rest of the scalp. Furthermore, contractions of facial and neck muscles do not seem to have a significant role in pain generation in electric TCS. Pain can be prevented if sufficiently large areas of the scalp are properly anaesthetized before stimulation by e.g. blockade of the major nerves responsible for the sensation of the stimulus area.

Adult↗
PubMed1998

Peculiarity of soleus motor potentials evoked by transcranial magnetic stimulation and electrical stimulation of tibial nerve.

OBJECTIVE: To reveal and discuss the peculiarities of soleus muscle in comparison with electrophysiological features of other leg muscles. METHODS: Vastus lateralis (L3), tibialis anterior (L4), extensor digitorum brevis (L5) and soleus (S1) muscles were tested at rest. Transcranial magnetic stimulation (TMS) combined which electrical stimulation of relevant peripheral nerves were applied. Cortically evoked motor potentials (C-MEP), peripheral compound muscle action potential (CMAP) and F-wave were recorded. Estimating F-wave conduction time allowed to calculated the central conduction time (CCT-F) within the cortex-spinal motoneurones segment for each muscle. RESULTS: One could expect that the lower spinal metameric representation of the muscle the longer a corresponding CCT-F. However, a study of 30 healthy subject (60 right and left muscles) reveals a relatively short CCT-F for the soleus muscle. Moreover, the mean amplitude of soleus C-MEP is the lowest, CMAP and F-wave amplitude are the highest and standardised distal motor latency is the longest compared to the analogous parameters for the other muscles. CONCLUSIONS: The reason for these special features can be attributed probably to a different structure and innervation of the soleus (mainly red, slow, tonic muscle) in contrast to the tibialis anterior and extensor digitorum brevis (mainly white, fast, phasic muscle).

Adolescent↗
PubMed1997

Urinary bladder control by electrical stimulation: review of electrical stimulation techniques in spinal cord injury.

Evacuation of urine in paraplegics without the need for catheters would be possible when voiding could be induced by eliciting a bladder contraction. A challenging option to obtain detrusor contraction is electrical stimulation of the detrusor muscle or its motor nerves. This article reviews the 4 possible stimulation sites where stimulation would result in a detrusor contraction: the bladder wall, the pelvic nerves, the sacral roots, and the spinal cord. With respect to electrode application, sacral root stimulation is most attractive. However, in general, sacral root stimulation results in simultaneous activation of both the detrusor muscle and the urethral sphincter, leading to little or no voiding. Several methods are available to overcome the stimulation-induced detrusor-sphincter dyssynergia and allow urine evacuation. These methods, including poststimulus voiding, fatiguing of the sphincter, blocking pudendal nerve transmission, and selective stimulation techniques that allow selective detrusor activation by sacral root stimulation, are reviewed in this paper.

Electric Stimulation↗
PubMed1982

Modulation of spasticity: prolonged suppression of a spinal reflex by electrical stimulation.

Electrical subcutaneous nerve stimulation of radial, median, and saphenous nerves has been shown to produce prolonged analgesia. In a double blind study, such stimulation also suppressed clonus for 3 hours after stimulation ceased in subjects with spasticity. Since the effect is contralateral, each subject was his own control. Because stimulation of the nerve in the wrist suppressed ankle clonus, the mechanism mediating the effect must be centrifugal inhibition. These results suggest that subcutaneous nerve stimulation may also be a tool in the management of spasticity.

Electric Stimulation↗
PubMed2001

A comparative study of the effects of magnetic stimulation and electric stimulation on peripheral nerve injury in rat.

The influence of pulsed magnetic stimulation (MS) on the sciatic nerve injury was investigated. Thirty rats were divided into three groups equally: MS group (A), electric stimulation (ES) group (B) and the control group (C). The MS and ES were applied immediately after the first 10 min of the sciatic nerve crush. Sciatic function index (SFI), toe spreading reflex (TSR), muscular weight and volume were measured after the experiment. The TSR of in the groups A and B occurred at 4th day while in the control group it occurs at 10th day. There was statistically significant difference in SFI between groups A and B (P < 0.01). The weight and volume of the gastrocnemius muscle were statistically greater in the groups A and B than in the control group (P < 0.01). The effect of MS was similar to that of ES. It was suggested that the application of MS immediately after the nerve injury might have an important clinical value as it can accelerate functional recovery and prevent or minimize muscle atrophy. The technique is easily to operate, non-invasion, painless and permits tolerance of high intensity output to be used.

Animals↗
PubMed1980

[Cortical influences on hemodynamics during combined nociceptive stimulation and electric stimulation of septal and bulbar brain structures].

Changes of the arterial pressure, blood flow volume rate and peripheral vascular resistance were studied under the nociceptive and electric stimulation of the microcellular reticular nucleus of the medulla oblongata and the lateral septal nucleus in cats. The isolated nociceptive stimulation of the reticular nucleus increased the arterial pressure and the peripheral vascular resistance whereas the stimulation of the septum induced a depressor reaction. The combined stimulation of the bulbar structures increased still more the peripheral vascular resistance. The change in the pressor reaction depended on the character of the previous stimulation. The combined stimulation of the septum completely abolished the pressor nociceptive reaction. The reaction was but decreased under the reverse combination of the electric and nociceptive stimuli. Application of strychnine and potassium chloride on the sensomotor cortical area induced a clear decrease in the pressor reaction only when the reticular nucleus had been stimulated. The peripheral vascular resistance decreased after the application of these agents as well as on the stimulation of the septum.

Animals↗
PubMed2005

Differences in quadriceps femoris muscle torque when using a clinical electrical stimulator versus a portable electrical stimulator.

BACKGROUND AND PURPOSE: There have been conflicting views and evidence reported in the literature concerning differences in muscle torque-generating capacities between clinical ("plug-in") console devices whose power source is provided by an electrical outlet (60 Hz, alternating current-driven) and portable electrical muscle stimulators (smaller, battery-operated stimulators). The purpose of this study was to compare the torque-generating capacity of the quadriceps femoris muscle during neuromuscular electrical stimulation (NMES) between a clinical neuromuscular electrical stimulator (VersaStim 380) and a portable neuromuscular electrical stimulator (Empi 300PV). SUBJECTS: Forty volunteer subjects with no known knee, neurological, or cardiovascular pathology (22 male, 18 female) participated in the study. METHODS: All subjects were tested with the clinical and portable stimulators on 2 separate days. Peak isometric torque of the quadriceps femoris muscle was measured using a Biodex dynamometer. Peak isometric quadriceps femoris muscle torque achieved during NMES and the average quadriceps femoris muscle torque integral produced over 10 NMES contractions were measured for each stimulator. Subjects also rated the amount of pain they experienced during the 10 NMES contractions using a numeric pain scale. Paired t tests were used to compare mean differences in measured variables between stimulator conditions. RESULTS: There were no differences in the peak torque or numeric pain ratings during the electrically stimulated contractions between stimulator conditions. The Empi 300PV produced a greater average torque integral compared with the VersaStim 380 during 10 electrically stimulated contractions (Empi 300PV=988.6-/+330.4 N.m-s, Versastim 380=822.7-/+292.6 N.m-s). DISCUSSION AND CONCLUSION: The portable Empi 300PV stimulator produced comparable levels of average peak torque at comparable levels of discomfort to those produced by the VersaStim 380 clinical stimulator. The Empi 300PV maintained greater amounts of torque production during a 10-contraction training session compared with the VersaStim 380. Based on these data, we believe that the Empi 300PV has the potential to produce adequate levels of torque production for NMES quadriceps femoris muscle performance training. Further study is needed to determine the effectiveness of using the Empi 300PV for quadriceps femoris muscle performance training.

Adult↗