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PubMed1995

Incorporation of amino acids into the axoplasm is enhanced by electrical stimulation of the fiber.

The effect of sustained electrical stimulation upon the incorporation of amino acids into the axoplasm was studied in the goldfish Mauthner (M) axon with light autoradiography. An extracellular pulse of tracers applied between M-axons in the medulla resulted in a local and substantial labeling of the M-axoplasm and a faint labeling of the M-perikaryon 4-5 mm away from the site of injection. After 18 h of direct electrical stimulation of the M-axon at 0.3-0.8 Hz, the local incorporation of amino acids into the M-axoplasm doubled. This enhancement declined to reach the baseline within 24 h. A 4 h electrical stimulation did not enhance the incorporation. Transynaptic activation of the M-neuron through the auditory input at 0.1-0.2 Hz for 18 h did not raise the amino acid incorporation in the M-axoplasm. We conclude that electrical discharge of the axon modulates the local incorporation of amino acids into the axoplasm.

Amino Acids↗
PubMed1994

Distribution of c-fos expressing dorsal horn neurons after electrical stimulation of low threshold sensory fibers in the chronically injured sciatic nerve.

The distribution of proto-oncogene c-Fos protein-immunoreactive cells in the spinal cord dorsal horn was studied after electrical stimulation at A alpha/A beta-fiber intensity of normal and previously injured sciatic nerves in urethane anesthetized rats. No or only occasional Fos protein-like immunoreactive cells were seen after stimulation of the normal uninjured nerve or after nerve transection without stimulation. Electrical nerve stimulation at 3, 12, and 21 days after sciatic nerve transection resulted in substantial increases in the numbers of Fos protein-like immunoreactive cell nuclei in each of Rexed's laminae I-V. Combined demonstration of Fos protein-like immunoreactivity and of glial fibrillary acidic protein-like immunoreactivity (astroglia) or OX-42 immunoreactivity (microglia), indicated that the observed Fos protein-like response was confined to neurons and not to astroglia or microglia. Combined demonstration in the spinal cord of Fos protein-like immunoreactive neurons and neurons labeled retrogradely with Fluoro-Gold from the gracile nucleus showed that some of the Fos protein-like immunoreactive neurons in Rexed's laminae III and IV contributed to the postsynaptic dorsal column pathway. The results indicate that stimulation at A alpha/A beta-fiber intensity of a previously injured nerve gives rise to an abnormally increased activation pattern of postsynaptic neurons in the dorsal horn, some of which contribute to the postsynaptic dorsal column pathway.

Action Potentials↗
PubMed2006

Dopamine efflux in the rat striatum evoked by electrical stimulation of the subthalamic nucleus: potential mechanism of action in Parkinson's disease.

The precise mechanism whereby continuous high-frequency electrical stimulation of the subthalamic nucleus ameliorates motor symptoms of Parkinson's disease is unknown. We examined the effects of high-frequency stimulation of regions dorsal to and within the subthalamic nucleus on dopamine efflux in the striatum of urethane-anaesthetized rats using constant potential amperometry. Complementary extracellular electrophysiological studies determined the activity of subthalamic nucleus neurons in response to similar electrical stimulation of the subthalamic nucleus. High-frequency stimulation of the subthalamic nucleus increased action potential firing in the subthalamic nucleus only during the initial stimulation period and was followed by a cessation of firing over the remainder of stimulation. Electrical stimulation of the subthalamic nucleus with 15 pulses elicited stimulus-time-locked increases in striatal dopamine efflux with maximal peak effects occurring at 50 Hz frequency and 300 microA intensity. Extended subthalamic nucleus stimulation (1000 pulses at 50 Hz; 300 microA) elicited a similar peak increase in striatal dopamine efflux that was followed by a relatively lower steady-state elevation in extracellular dopamine over the course of stimulation. In contrast, extended stimulation immediately adjacent and dorsal to the subthalamic nucleus resulted in an 11-fold greater increase in dopamine efflux that remained elevated over the course of the stimulation. Immunohistochemical staining for tyrosine hydroxylase revealed catecholaminergic fibers running immediately dorsal to and through the subthalamic nucleus. Taken together, these results suggest that enhanced dopamine release within the basal ganglia may be an important mechanism whereby high-frequency stimulation of the subthalamic nucleus improves motor symptoms of Parkinson's disease.

Action Potentials↗
PubMed2006

Nociceptive threshold and analgesic response to morphine in aged and young adult rats as determined by thermal radiation and intracerebral electrical stimulation.

The present experiment compared the nociceptive threshold and analgesic response to morphine in young (4-5 months) and aged (24 months) rats using peripheral thermal stimulation and intracerebral electrical stimulation. Responses to thermal stimuli were assessed using both the classical tail-flick procedure in which latency of response is the dependent variable and a new method in which threshold in calories of heat is the dependent variable. In the intracerebral nociceptive threshold procedure, electrical stimuli were delivered via an electrode implanted in the mesencephalic reticular formation (MRF), a pain pathway, and the animals were trained to terminate the stimulation by turning a cylindrical manipulandum embedded in one wall of the experimental chamber. For the classical tail-flick method, the aged rats required a greater intensity of stimulation to produce a basal response latency that was between 2.5 and 3.5 s. Using the new psychophysical method for determining the tail-flick threshold, the aged rats' basal thresholds were significantly higher than that of the young rats. However, the basal thresholds obtained by direct stimulation of the MRF failed to show a significant age effect, suggesting that the registration of pain is not different between young and aged rats. These age-related differences in baseline tail-flick response may be due to changes in the spinal reflex associated with aging. Although, there was no difference in the analgesic effects of morphine between young and aged rats using the latency of the tail-flick response, evidence for decreased analgesic response was seen using the tail-flick threshold measure and the intracerebral stimulation threshold method.

Analgesics, Opioid↗
PubMed2002

Increase in tibialis anterior motor cortex excitability following repetitive electrical stimulation of the common peroneal nerve.

The purpose of this study was to investigate whether repetitive electrical stimulation of the common peroneal nerve (CPN) is associated with changes in the motor response of the tibialis anterior (TA) muscle elicited by focal magnetic stimulation of the motor cortex. Motor evoked potentials (MEP) with a stimulation intensity of 125% of the threshold of the relaxed right TA were obtained before, during, and after repetitive electrical stimulation of the CPN (trains of five pulses of 1 ms, at a frequency of 200 Hz, repeated every second with a 30-min duration). The MEP of the TA muscle elicited after repetitive electrical stimulation were increased by 104% (range: 18-263%), and the increase was maintained for up to 110 min (range: 15-110 min) after the end of nerve stimulation. This increase in the MEP of the TA muscle was associated with a decrease in the threshold from the stimulation-response curve. Furthermore, during that period the early component of the TA stretch reflex as well as the latency of the MEP did not significantly change. To further test the origin of the increased MEP, complementary experiments showed that MEP elicited by transcranial electrical stimulation (TES) were also increased, but to a lesser degree (approximately 50%) than MEP elicited by TMS. It can be concluded that short-term nerve repetitive electrical stimulation of the lower extremities in healthy human participants can lead to a long-term increase in the contralateral MEP. As TES is believed to mainly activate the axon and not the soma of the cortical cells, the increased MEP cannot be explained exclusively by changes in the motor cortex cell excitability, but also by changes in subcortical neural structures involved in the excitation of spinal motoneurons. The results of this study allow the speculation that it would be possible to use repetitive electrical stimulation in the rehabilitation of patients with lower limb muscle weakness and spasticity.

Adult↗
PubMed2006

Postfatigue potentiation of the paralyzed soleus muscle: evidence for adaptation with long-term electrical stimulation training.

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI.

Adaptation, Physiological↗
PubMed2003

Electrical stimulation induced cervical medial branch referral patterns.

STUDY DESIGN: Electrical stimulation of the right cervical medial branches with or without the third occipital nerves was performed in nine subjects for a total of forty-eight medial branches and eight third occipital nerves. The referral patterns of each nerve or nerve branch was mapped on a human line diagram. These diagrams were compared to facet joint (zygapophyseal joint, facet joint), myofascial, and discogenic referral patterns already published by various authors. OBJECTIVE: [corrected] To determine the referral patterns of the cervical medial branches and the third occipital nerve. HYPOTHESIS: The cervical medial branch referral patterns created by electrical stimulation may differ from those reported from other etiologies and may prove to be useful when considering various cervical pain syndromes. METHODS: The third occipital nerve and third through eighth medial branches of the cervical posterior rami of nine subjects with and without a history of neck pain were electrically stimulated under fluoroscopic imaging. All subjects were blinded to the level of stimulation, and the referral patterns of each individual were mapped out on a human line drawing by the primary author of this study. These referral patterns were compared to referral patterns reported from other etiologies by various authors. CONCLUSIONS: Electrical stimulation of the third occipital nerve as well as the medial branch of the right C3-C8 posterior primary rami create discrete, reproducible referral patterns which differ from those reported from other etiologies by various authors.

Journal Article↗
PubMed1986

The effect of electrical stimulation on reinnervation of rat muscle: contractile properties and endplate morphometry.

Denervated extensor digitorum longus muscles of Wistar rats were electrically stimulated in vivo for 4 days (2h per day) after peroneal nerve crush 1 cm from the muscle. Isometric contractile properties and endplate ultrastructure were measured on days 11 and 18. On day 11, the time to peak (116% of control) and 1/2-relaxation time (136% of control) for the twitch tensions of stimulated muscles measured in vivo were significantly less than those (127% and 157% of controls, respectively) of non-stimulated muscles. Peak twitch and tetanic tensions were not significantly different. The postsynaptic area of endplates for stimulated muscles were closer in size to controls than those for the non-stimulated ones. On day 18, no difference was found in the contractile responses between stimulated and non-stimulated groups. Similarly, the postsynaptic areas were the same for both groups. These results demonstrate that denervated muscle stimulated electrically for 4 days prior to reinnervation can preserve the structure of the endplate as well as accelerate recovery of normal function in reinnervated muscle fibers after 11 days of denervation.

Animals↗
PubMed1976

Adjustable nonimplantable electrical stimulators for correction of urinary incontinence.

Investigations of functional electrical stimulation (FES) of the closing muscles in the lower urinary tract using nonimplantable electrical stimulators have reached the final stage. The optimal stimuli parameters were chosen on the basis of neurophysiological studies of the urinary tract and urodynamic measurements of mechanical response to electrical stimulation. According to these findings, two electronic systems for FES have been developed. An adjustable system for stimulation of the urethral closing mechanism using vaginal or anal plugs. The external unit of the stimulator contains a generator producing square-wave pulses. The vaginal and anal plugs are from Vitalograph Ltd, and Cardiac Recorders Ltd., commercial tipes redesigned to suit our needs. Frequency and duration of the pulses can be individually adjusted for each patient. An automatic integrated adjustable system for stimulation of the urethral closing mechanism built into a vaginal plug. This stimulator is based on completely new design principles. It has the form of a cylinder with hemispherical ends. Both the electronic unit and battery supply are located within. The system is completely automatic and is started by placing the stimulator in the vagina. Both systems mentioned were constructed for curing stress incontinence, post-operative incontinence, enuresis and in some cases for use in incontinent paraplegics. Clinical evaluation has given satisfactory results for both types of stimulators in the above-mentioned patients. They are simple to use and instructions can be given in an urologist's prescription. Permanent or intermittent application is possible.

Anal Canal↗
PubMed1975

Eye and head movements evoked by electrical stimulation of monkey superior colliculus.

In unrestrained animals of many species, electrical stimulation at sites in the superior colliculus evokes motions of the head and eyes. Collicular stimulation in monkeys whose heads are rigidly fixed is known to elicit a saccade whose characteristics depend on the site stimulated and are largely independent of electrical stimulation parameters and initial eye position. This study examined what role the colliculus plays in the coding of head movements. A secondary aim was to demonstrate the effects of such electrical stimulation parameters as pulse frequency and intensity. Rhesus monkeys were free to move their heads in the horizontal plane; head and eye movements were monitored. As in previous studies, eye movements evoked by collicular stimulation were of short latency, repeatable, had a definite electrical threshold, and did not depend on the initial position of the eye in the orbit. By contrast, evoked head movements were extremely variable in size and latency, had no definite electrical threshold, and did depend on initial eye position. Thus when the eyes approached positions of extreme deviation, a head movement in the same direction became more likely. These results suggest that the superior colliculus does not directly code head movements in the monkey.

Animals↗
PubMed1981

Effects of ouabain and electrical stimulation on the fine structure of nerve endings in the electric organ of Torpedo marmorata.

The cycle of synaptic vesicles was studied in isolated nerve terminals and in the electric tissue of Torpedo marmorata. The synaptosomes, as used in this investigation, were a pure cholinergic subcellar fraction that captured dextran particles as an extracellular marker. This endocytotic phenomenon was enhanced by potassium depolarization. Field electrical stimulation (1 Hz and 10 Hz) of the electric organ induced the appearance of membrane foldings into presynaptic terminals. Morphometric studies showed that the number of synaptic vesicles did not decline until after at least 30 min. On the other hand, at 10 Hz these changes were accompanied by an increase in length of the membrane of the terminal. At 15 min of recovery after prolonged stimulation, there was a great increase in density of synaptic vesicles with a large number of vesicles of small diameter. This increase was accompanied by a decrease of membrane length, suggesting that reformation of vesicles is related to retrieval of membrane. Pharmacological stimulation with ouabain produced changes similar to those of long-term electrical stimulation. These changes in membrane were accompanied by a decrease of the population of synaptic vesicles and a wide variation in their diameters. It is concluded that structural changes reported here could not be correlated with kinetics of the transmitter release.

Animals↗
PubMed1980

Electrical stimulation providing functional use of paraplegic patient muscles.

The paper presents a short description of the field of electrical stimulation of skeletal muscles and a survey of the recent achievements in the functional electrical stimulation (FES) of paraplegic patients. The major emphasis is placed on the discussion of the basic problems concerning muscle fatigue, muscle retraining and patient selection. Muscle strengthening and exercising procedures using electrical stimulation are described. The obtained properties of retrained muscles with special regard to their fatiguing are clearly documented. The potential possibilities of using FES for performing functional tasks are discussed and the results of preliminary experiments are illustrated. The standing and primitive walking of patient, induced by electrically stimulated paralyzed muscles are presented. Finally, a proposal for an orthotic device using electrical stimulation is described, which enables a paraplegic patient to stand by means of support of his proper bones and muscle forces.

Adult↗
PubMed2004

Effects of electrode-to-fiber distance on temporal neural response with electrical stimulation.

This paper presents an analysis of the effects of the electrode-to-fiber distance on the temporal response properties of an auditory nerve fiber stimulated by electric current pulses. This analysis was based upon results from a computational model of a mammalian auditory nerve fiber axon having 50 nodes of Ranvier, each consisting of 130 stochastic sodium channels and 50 stochastic potassium channels, making it possible to represent the temporal fluctuations of action potential initiation and conduction. A monopolar stimulus electrode was located above a central (26th) node at electrode-to-fiber distances of 1, 4, and 7 mm, while the recording electrode was located at the 36th node. Action potentials (spikes) were generated by the biophysical model using the Crank-Nicholson method to solve a diffusive partial differential equation. By observing the occurrence times of spikes in response to 2000 cathodic monophasic stimulus pulses, temporal jitter (i.e., the standard deviation of spike times) was calculated and the poststimulus time (PST) histogram was generated as well. Furthermore, by computing the PST histogram for each initiation node as functions of space (node number) and time (PST), it was shown that spike initiation was distributed not only spatially but also temporally for stimulus levels producing firing efficiencies (FEs) near 0.5. However, at levels producing FEs near 0.99, while temporal variations approached zero, the spatial distribution of initiating nodes was comparable to that observed for the FE near 0.5. As temporal fluctuations are important for speech coding in cochlear implants, we conclude that spatial characteristics of the electrode-auditory nerve fiber interface may play a significant role in influencing these stochastic temporal processes.

Action Potentials↗
PubMed1960

Feeding behavior and electrical stimulation of the brain of Carassius auratus.

Bipolar electrodes were implanted in large goldfish in olfactory and nonolfactory areas of the central nervous system. Stimulation of olfactory areas elicited stereotyped feeding activity indistinguishable from normally induced behavior. It is suggested that the olfactory rather than the peripheral gustatory system plays the predominant role in the arousal of feeding activity.

Animals↗