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PubMed1997

Comparison of current waveforms for the electrical stimulation of residual low frequency hearing.

Many cochlear prostheses employ charge-balanced biphasic current pulses. These pulses have little energy at low frequencies resulting in limited stimulation of low frequency hearing by mechanical responses to the electrical stimulus. However, if electro-mechanical transduction within the cochlea is nonlinear, electrical stimulation with asymmetric, charge-balanced current pulses may result in a mechanical response with significantly more low frequency energy. We estimated the mechanical response at low frequencies to pulsatile electrical stimulation of the cochlea. The auditory nerve compound action potential evoked by low frequency tones was forward-masked by a train of symmetric or asymmetric current pulses. Masking by asymmetric current pulses was not significantly different from masking by symmetric pulses matched for pulse duration and charge. In conclusion, there appears to be no advantage to using asymmetric current pulses for the mechanical stimulation of residual low frequency hearing by electrical stimulation of the cochlea.

Animals↗

PubMed1992

Chronic intracochlear electrical stimulation in neonatally deafened cats: effects of intensity and stimulating electrode location.

An earlier study conducted in this laboratory suggested that chronic intracochelear electrical stimulation at moderate current levels can at least partially delay or prevent the retrograde degeneration of primary auditory (spiral ganglion) neurons that otherwise is progressive after neonatal deafness induced by ototoxic drug administration. Increased survival of spiral ganglion neurons was observed within the basal cochlear region near the stimulating biopolar electrode pairs, while in more apical regions there was no significant difference between the stimulated and control cochleas. The mechanisms underlying this maintenance of spiral ganglion neurons induced by chronic electrical stimulation are uncertain, especially since increased neuronal survival was observed over broader sectors of the ganglion than would be expected to be directly activated by the bipolar electrodes and moderate stimulation intensity (6 dB above electrically evoked auditory brainstem response threshold) used. In this report, data are presented from a second series of neonatally deafened and chronically stimulated cats. The parameters for chronic electrical stimulation were manipulated in two simple ways. First, the intensity of the electrical stimulus was reduced from the earlier study, while the duration of chronic stimualtion periods was increased; and secondly, two different intracochlear positions of stimulating electrodes were employed in different experimental groups. Results indicate that elecrical stimulation of the cochlea at an extremely low intensity (2 dB above electrically evoked auditory brainstem response threshold) is sufficient to at least partially prevent or delay ganglion cell degeneration in the deafened cochlea. In addition, data suggest a differential distribution of the maintained or conserved ganglion cells, such that when the stimulating electrode pair was positioned near the base of the cochlea increased ganglion survival in a more basal cochlear sector, while stimulation at a more apical site resulted in increased neuronal survival extending to more apical regions.

Animals↗

PubMed1990

Responses of blood vessels in the rabbit knee to electrical stimulation of the joint capsule.

1. An in vitro preparation of the rabbit knee joint, perfused with oxygenated Locke's solution, was used to study the response of articular blood vessels to electrical stimulation of the joint capsule. 2. Using trains of stimulus pulses of different durations, frequency-response curves were obtained. Electrical stimulation always produced vasoconstriction of joint blood vessels, which increased as a function of both frequency and pulse width. 3. This vasoconstrictor response was neurally mediated as it was markedly inhibited after addition to both bath and perfusate of tetrodotoxin. In addition, the response to field stimulation of the capsule was virtually abolished in animals pretreated with reserpine which depletes sympathetic nerve endings of noradrenaline. 4. The response to electrical stimulation was substantially reduced by the alpha-adrenergic antagonist phenoxybenzamine (10(-5) M), the alpha 1-blocker prazosin (10(-6) M), and by guanethidine (10(-5) M) which inhibits the release of noradrenaline, ATP and neuropeptide Y from sympathetic nerve endings. 5. The attenuation of the vasoconstrictor response to field stimulation by prazosin (10(-6) M) was little altered by addition of the alpha 2-adrenoceptor blocker rauwolscine (10(-6) M) to the perfusate. 6. alpha, beta-Methylene ATP (10(-6) M), a P2-purinoceptor desensitizer, had no effect on the vasoconstrictor response to electrical stimulation. 7. These results indicate that the vasoconstrictor response to electrical stimulation of the rabbit knee joint capsule is mediated via noradrenaline acting upon alpha 1-adrenoceptors.

Adenosine Triphosphate↗

PubMed2006

Nonpharmacological treatment of lower urinary tract dysfunction using biofeedback and transcutaneous electrical stimulation: a pilot study.

OBJECTIVE: To report a series of children with lower urinary tract dysfunction (LUTD) whose urge syndrome was treated by electrical stimulation, and their voiding dysfunction by biofeedback; none of the children were using anticholinergic drugs during treatment. PATIENTS AND METHODS: In all, 36 children who presented with symptoms of urinary urgency and/or daily incontinence completed the treatment and were prospectively evaluated. The mean (range) follow-up was 13.8 (4-24) months, and their mean age 7 (3-14) years, 17 children were aged <5 years. The children were divided into two groups: group 1, with urge syndrome treated with superficial parasacral electrical stimulation, and group 2, with voiding dysfunction, treated with biofeedback. RESULTS: In group 1, the mean (range) number of electrical stimulation sessions was 13.1 (4-20). Of the 19 children treated, 12 had a complete clinical improvement, six a significant improvement, and one a mild improvement. In group 2, the mean (range) number of biofeedback sessions was 6 (4-14). Of the 17 children treated, there was complete improvement of symptoms in 10, significant improvement in two and mild improvement in five. Six children who had no resolution of symptoms after biofeedback had salvage therapy with electrical stimulation, after which four had complete improvement of symptoms, and two a 90% and 40% improvement, respectively. Taking the two groups together, after treatment, four children developed isolated episodes of urinary tract infection. Of 21 children with nocturnal enuresis, bed-wetting continued in 13 (62%) after treatment. CONCLUSION: In this short-term follow-up, the nonpharmacological treatment of voiding dysfunction using biofeedback, and of urge syndrome by electrical stimulation, was effective for treating LUTD in children.

Adolescent↗

PubMed1997

Electrical stimulation of acupuncture points enhances gastric myoelectrical activity in humans.

OBJECTIVE: Acupuncture is known to enhance gastric motility. Electrical acustimulation has been shown to reduce gastric tachyarrhymia in vection-induced motion sickness. The aim of this study was to investigate the effect of electrical stimulation of acupuncture points on gastric myoelectrical activity in healthy humans. METHODS: Nine healthy native Chinese were studied. Gastric myoelectrical activity was recorded using surface electrogastrography (EGG). The EGG recording was made in the fasting state, in a study period during which acupuncture points were electrically stimulated continuously, and in a recovery period after stimulation. The percentage of regular slow waves was assessed by computing the percentage of 2 to 4 cycles per minute slow waves in the EGG. RESULTS: Electrical stimulation significantly increased the percentage of regular slow waves, which was sustained in the recovery period. The increase of the regular slow wave activity resulted from the normalization of arrhythmia. CONCLUSION: Electrical stimulation of acupuncture points may enhance the regularity of gastric myoelectrical activity and may be an option for treatment of gastric dysrhythmia.

Acupuncture Points↗

PubMed1998

Botulinum toxin type A and short-term electrical stimulation in the treatment of upper limb flexor spasticity after stroke: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To investigate whether the combined approach of botulinum toxin type A (BtxA) and electrical stimulation was more effective than the toxin alone in the treatment of chronic upper limb spasticity after stroke. DESIGN: Randomized, placebo-controlled study with four treatment groups: 1000 units BtxA (Dysport) + electrical stimulation (A), 1000 units BtxA (B), placebo + electrical stimulation (C) and placebo (D). SETTING: A neurological rehabilitation clinic. SUBJECTS: Twenty-four stroke patients with chronic upper limb spasticity after stroke, six patients in each treatment group. INTERVENTIONS: Intramuscular injection of either toxin or placebo into six upper imb flexor muscles. In group A and C additional electrical stimulation of the injected muscles with surface electrodes, three times half an hour each day for three days. MAIN OUTCOME MEASURES: Muscle tone rated with the modified Ashworth score, limb position at rest and difficulties encountered during three upper limb motor tasks assessed before and 2, 6 and 12 weeks after injection. RESULTS: Most improvements were observed in patients of group A. Cleaning the palm (p = 0.004) differed across groups. Pairwise comparison for this target variable showed that group A differed from group B and D (p <0.01), but not from C. Indicative across-group differences were obtained for elbow spasticity reduction (p = 0.011), and improvement of putting the arm through a sleeve (p = 0.020). CONCLUSIONS: The placebo-controlled trial favours the concept that electrical stimulation enhances the effectiveness of BtxA in the treatment of chronic upper limb flexor spasticity after stroke.

Activities of Daily Living↗

PubMed1994

Electrical stimulation of cardiac tissue: a bidomain model with active membrane properties.

Numerical calculations simulated the response of cardiac muscle to stimulation by electrical current. The bidomain model with unequal anisotropy ratios represented the tissue, and parallel leak and active sodium channels represented the membrane conductance. The speed of the wavefront was faster in the direction parallel to the myocardial fibers than in the direction perpendicular to them. However, for cathodal stimulation well above threshold, the wavefront originated farther from the cathode in the direction perpendicular to the myocardial fibers than in the direction parallel to them, consistent with observations of a dog-bone-shaped virtual cathode made by Wikswo et al., Circ. Res. 68:513-530, 1991. The model showed that the virtual cathode size and shape were dependent upon both membrane and tissue conductivities. Increasing the peak sodium conductance or reducing the transverse intracellular conductivity accentuated the dog-bone shape, while the opposite change caused the virtual cathode to become more elliptical, with the major axis of the ellipse transverse to the fiber direction. A cathodal stimulus created regions of hyperpolarization that slowed conduction of the wavefront propagating parallel to the fibers. An anodal stimulus evoked a wavefront with a complex shape; activation originated from two depolarized regions 1 to 2 mm from the stimulus site along the fiber direction. The threshold current strength (0.5 ms duration pulse) for a cathodal stimulus was 0.048 mA, and for an anodal stimulus was 0.67 mA. When the model was modified to simulate the effect of electropermeabilization, which may be present when the transmembrane potential reaches very large values near the stimulating electrode, our qualitative conclusions remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1977

Measurements of contraction latencies to mechanical and electrical stimulation of the protozoan, Spirostomum ambiguum.

Measurements made on contraction latencies in Spirostomun suggest that mechanical stimulation causes contractions to be initiated by the release of small amounts of calcium from a store tightly coupled to the contractile apparatus. Contraction to electrical stimulation appears to result from the gross electrophoretic mobilization of large amounts of calcium from a loosely coupled store. Contraction latencies to mechanical stimulation were three milliseconds and were independent of stimulus strength, previous stimulation, and contraction probability. For 0.5-millisecond biphasic electrical stimulation the contraction latencies varied widely. Latencies to initial contractions were dependent on stimulus strength: from 1.0 milliseconds for a stimulus that caused a 100% probability of contraction to 2.0 milliseconds for a stimulus that caused a 10% probability of contraction. Latencies of contraction to electrical stimulation were also dependent upon previous stimulation, lengthening to over 300 milliseconds after ten minutes of stimulation. Initial contraction latencies were not affected by previous stimulation to the other (electrical or mechanical) stimulus modality. Repeated electrical stimulation also reduced the animal's resting length and slowed the rate of post contraction re-extension, whereas mechanical stimulation did not have these effects.

Animals↗

PubMed2005

Low amplitude, high frequency strains imposed by electrically stimulated skeletal muscle retards the development of osteopenia in the tibiae of hindlimb suspended rats.

The purpose of this study was to determine the extent to which high frequency, low amplitude skeletal muscle contractions, induced using electrical stimulation, could prevent or retard disuse osteopenia. Ten minutes of 30 Hz electrical stimulation was delivered, 5 days a week, during a 4 week rat-hindlimb suspension protocol. Each pulse generated a peak compressive dynamic strain on the tibia of approximately 200 microepsilon. We hypothesized that the electrical stimulation protocol would significantly reduce the loss of tibial bone mineral density compared to the contralateral control tibia that did not receive electrical stimulation. Compared to the contralateral control limb, the tibia of the stimulated limb had significantly higher bone mineral density and enhanced newly formed bone in the tibial diaphysis. The diaphysis, specifically the posterior bone cortex, of the tibia of the limb receiving the stimulation also demonstrated substantially larger mineral-binding fluorochrome biomarker within the osteocyte lacunae and canalicular volumes. Although the protocol did not prevent disuse osteopenia the evidence suggests that it was effective at reducing the extent of the osteopenia. One possibility for this outcome may be the insensitivity of bone to static, compared to dynamic compressive loads. In the present study there was a considerable static component to the compressive loads that accounted for a large component of the peak load generated by the stimulated skeletal muscle. Nevertheless, the results provide impetus for further development of the methods by which muscle contraction-induced loading of bone can be clinically exploited.

Animals↗

PubMed1997

Investigation of quadriceps femoris function through electrical stimulation.

OBJECTIVE: Patellofemoral dysfunctions are associated with problems in the knee extensor mechanism, including specific atrophy of the distal fibers of the vastus medialis, also known as the vastus medialis oblique. Rehabilitation of the vastus medialis in patellofemoral dysfunctions has been shown to be ineffective. This limitation had stemmed from the lack of understanding of the vastus medialis' specific functions. The purpose of this project was to investigate the role of four portions of the quadriceps femoris using surface electrical stimulation. DESIGN AND SETTING: Single-group and single-test (repeated measures on muscle portions) design. All tests were performed in a university laboratory. SUBJECTS: Eight healthy university students received electrical stimulation. MEASUREMENTS: Subjects were seated with the knee at 90 degrees of flexion and the leg pushing against a strain gauge that measured the force exerted. Electrical stimulation was administered on the vastus lateralis, rectus femoris, and proximal and distal fibers of the vastus medialis to quantify the torque produced by the knee extensors. The electrical stimulation maximum intensity was adjusted to achieve specific fiber recruitment and the highest isolated contraction. Force was measured with a strain gauge placed on the anterior aspect of the distal end of the tibia. Force was recorded in two levels: force applied before the onset of electrical stimulation and force produced by the stimulation. Subjects also performed two maximum isometric knee extensions before and after electrical stimulation for normalization. RESULTS: Electrical stimulation elicited mean torques of 6.31 per thousand, 14.0 per thousand, 20.2 per thousand, and 28.0 per thousand of maximum isometric voluntary contractions of the distal and proximal fibers of the vastus medialis, the vastus lateralis, and rectus femoris, respectively. CONCLUSIONS: The distal fibers of the vastus medialis do not contribute significantly to knee extension.

Journal Article↗

PubMed1986

Bladder inhibition by electrical stimulation of the perianal skin.

Transcutaneous electrical stimulation was applied to the perianal skin of 25 patients with frequency, urgency or incontinence. Repeated cystometrogram during this stimulation disclosed suppression of detrusor activity, inhibition of detrusor instability in 4 of 8 patients and increase of maximum cystometric capacity in 5 of 25 patients. Electromyographic activity of the anal sphincter muscle increased in all the 25 patients. Poststimulation improvement was observed clinically in 9 of 12 patients.

Anal Canal↗

PubMed1990

Electrical stimulation alters fatty acid metabolism in isolated skeletal muscle.

Little is known about the contribution of plasma free fatty acid (FFA) and intramuscular triacylglycerol (TG) as substrates for energy production during prolonged electrical stimulation of skeletal muscle. The purpose of this study was to investigate the effects of continuous and intermittent electrical stimulation protocols of different intensities on exogenous FFA oxidation, exogenous FFA incorporation into intracellular TG, and intracellular TG content in the isolated in vitro rat flexor digitorum brevis muscle preparation. Muscles were electrically stimulated for 0.5 h continuously at 0.2 Hz or intermittently (30 s on, 60 s off) at 0.2, 0.4, 0.8, and 5.0 Hz while incubated at 37 degrees C in 0.5 mM palmitate-3% bovine serum albumin medium (pH 7.4) in the presence of insulin (100 microU/ml) and glucose (11 mM). Control muscles were frozen immediately after excision or incubated for 0.5 h. At similar frequencies, less exogenous FFA esterification and more exogenous FFA oxidation occurred during continuous than during intermittent stimulation. As the frequency of intermittent stimulation increased, the amount of exogenous FFA esterified decreased and the amount of exogenous FFA oxidized increased. The data also indicate that at least a portion of TG was constantly being hydrolyzed during electrical stimulation. Under stimulation conditions in which exogenous FFA esterification was below the control (resting muscle) level, intramuscular TG content was significantly decreased compared with control TG content values. Thus both plasma FFA and intramuscular TG are substrates for energy production during electrical stimulation. However, the stimulation parameters employed affect the quantities utilized.

Animals↗

PubMed1983

Effects of naloxone and neonatal treatment with monosodium-L-glutamate on growth hormone and prolactin release induced by electrical stimulation of the medial-basal hypothalamus in rats.

The role of nerve cells of the arcuate nucleus and endogenous opioid peptides in the regulation of GH and prolactin secretion has been investigated. Electrical stimulation of the medial-basal hypothalamus (MBH) for 10 min raised plasma levels of both hormones in male rats anaesthetized with pentobarbitone sodium. Plasma hormone levels increased within 5 min after the termination of the stimulus, while no marked changes were found during stimulation. The GH response to the electrical stimulus was substantially reduced in rats with arcuate lesions induced by neonatal treatment with monosodium-L-glutamate (MSG). By contrast, the size of the prolactin response was not altered by MSG treatment. The opiate receptor antagonist naloxone (10 mg/kg, i.v.) failed to influence GH secretion induced by electrical stimulation in either control or MSG-treated animals. The post-stimulus rise of plasma prolactin levels was attenuated by naloxone in control rats, while the same dose of the drug was ineffective in rats which had been exposed to MSG. We conclude that endogenous opioids participate in the increase of prolactin release upon electrical stimulation of the MBH but are not involved in the GH secretory response. Arcuate neurones are important in the maintenance of the GH response to electrical stimulation. By contrast, lesioning of the arcuate nucleus failed to affect the prolactin secretory response elicited by MBH stimulation. However, prolactin release in MSG-treated rats appeared less susceptible to the inhibitory action of naloxone, suggesting a possible supersensitivity towards endogenous opioids.

Animals↗

PubMed2000

Prior electrical stimulation of the inferior colliculus sensitizes rats to the stress of the elevated plus-maze test.

Besides its primary function in the transmission of acoustic signals, the inferior colliculus (IC) is involved in conveying auditory information of aversive nature to higher cortical structures. In the field of anxiety research, one widely used animal model is the electrical stimulation of a given structure supposed to be involved in the neural circuitry underlying emotional behavior. Indeed, electrical stimulation of the inferior colliculus produces fear-like responses. Moreover, prior exposure to stressful events sensitizes rodents' responsivity to fearful stimuli when they are subsequently tested in the elevated plus-maze. Based on these evidence it seems to be important to know whether animals stimulated in the inferior colliculus would show a heightened behavioral responsivity to subsequent stressful events. To this end, we examined the temporal course of the effects of the electrical stimulation of this midbrain region (5, 10 and 15 min afterward) on the conventional and ethological measures of the behavior of rats exposed to the elevated plus-maze test. Prior electrical stimulation of the inferior colliculus produced an 'anxiogenic' profile in the elevated plus-maze, i.e. a significant reduction in the number of entries and time spent into the open arms. Still, previous electrical stimulation of the inferior colliculus caused a significant decrease in rearing, scanning, peeping out, head dipping and end-arm activity while increased immobility. All these changes occurred after 5 min of inferior colliculus electrical stimulation. Therefore, stimulation of the inferior colliculus causes a heightened responsivity to anxiogenic stimuli inherent to the elevated plus-maze test. These findings bring additional support to the proposed role of this midbrain structure in the elaboration of adaptive responses to stressful situations.

Animals↗

PubMed1977

Intravaginal electrical stimulation. Clinical experiments of urethral closure.

The effect on the urethra of intravaginal electrical stimulation (IVS) was registered by means of urethral pressure profiles (UPP). With the object of finding the most appropriate electrical parameters and optimal electrode positions within the vagina, 24 patients with stress incontinence, 22 with urgency and 4 continent women were studied. Electrical stimulation was given via an obturator with seven electrodes, which could be connected in different combinations of pairs. In all the women, stimulation with the electrodes in specific positions effected a more marked rise in the UPPs than with the electrodes in other positions. A change in position of more than 5 to 10 mm caused a decrease in the response. It was determined that a frequency of between 20 to 50 Hz with a pulse duration of 1 to 5 ms was most effective for urethral closure.

Adult↗

PubMed1995

Inhibitory influence from the nucleus reticularis pontis oralis on the micturition reflex induced by electrical stimulation of the pontine micturition center in cats.

An inhibitory influence from the nucleus reticularis pontis oralis on the micturition induced by electrical stimulation of the pontine micturition center was investigated in decerebrate cats at the supracollicular level. Monopolar electrical stimulation (30-50 microA, 0.2 ms, 50 Hz, 3 s) of the nucleus locus coeruleus alpha (pontine micturition center) produced micturition similar to that induced by distending the bladder by saline infusion. The intravesical pressure increase and micturition induced by electrical stimulation of the nucleus locus coeruleus alpha were suppressed by electrical stimulation of the nucleus reticularis pontis oralis in the intensity range 20-100 microA in a stimulus-intensity-dependent manner. These findings indicate that the nucleus reticularis pontis oralis has an inhibitory influence on the functions of the micturition center.

Animals↗

PubMed1992

Induction of atrial natriuretic factor and myosin light chain-2 gene expression in cultured ventricular myocytes by electrical stimulation of contraction.

While hormonal stimuli and mechanical stretch can induced cardiac-specific gene expression and in some cases cellular hypertrophy, the relationship between myocyte contraction frequency, gene expression, and myocyte growth has not been well characterized. In this study a new model system was developed in which cultures of neonatal rat ventricular myocytes were subjected to long term pacing of contractions with pulsatile electrical stimulation. Myocytes submitted to electrical stimulation for 3 days displayed dramatic increases in cellular size and myofibrillar organization, and a 5-10-fold increase in the expression of the cardiac genes atrial natriuretic factor and myosin light chain-2. Atrial natriuretic factor expression induced by electrical stimulation of contractions was inhibited by nifedipine or W7, indicating a dependence on calcium influx and calmodulin activity. Phosphoinositide hydrolysis and cAMP formation were not affected by electrical stimulation suggesting that gene induction occurred independently of the activation of protein kinases C or A above basal levels. These findings show that the cellular events associated with contraction, such as changes in cytoplasmic free calcium levels and/or cellular stretch, may serve as important determinants of myocyte growth and cardiac gene expression.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1989

Electrical stimulation of primary afferent A fibres does not reduce substance P release in the dorsal horn of the cat.

Antibody microprobes were used to measure the release of immunoreactive substance P in the dorsal horn of anaesthetised cats during noxious mechanical or thermal stimulation of the hind limb. Concomitant electrical stimulation of the ipsilateral tibial or sural nerve at intensities sufficient to excite only A alpha beta or additionally A delta primary afferent fibres did not reduce the release of substance P evoked by noxious stimuli. The results suggest that segmental inhibition produced in the dorsal horn by electrical stimulation of peripheral nerves is not mediated by presynaptic inhibition of substance P release from nociceptive primary afferent fibres.

Animals↗