12. More pulses – lower thresholds? The efficacy of the number of pulses within a stimulus train to elicit MEPs

2014 ◽  
Vol 125 (5) ◽  
pp. e17
Author(s):  
Dimitrios Kefalas ◽  
Andrea Szelényi
Keyword(s):  
Stimulus Train

Properties of synaptic inputs from myenteric neurons innervating submucosal S neurons in guinea pig ileum

2000 ◽  
Vol 278 (2) ◽  
pp. G273-G280 ◽  
Author(s):  
B. A. Moore ◽  
S. Vanner
Keyword(s):  
Guinea Pig ◽  
Myenteric Plexus ◽  
Intracellular Recordings ◽  
Guinea Pig Ileum ◽  
Myenteric Neurons ◽  
Synaptic Inputs ◽  
Stimulus Train ◽  
Stimulation Of ◽  
Double Chamber

This study examined synaptic inputs from myenteric neurons innervating submucosal neurons. Intracellular recordings were obtained from submucosal S neurons in guinea pig ileal preparations in vitro, and synaptic inputs were recorded in response to electrical stimulation of exposed myenteric plexus. Most S neurons received synaptic inputs [>80% fast (f) excitatory postsynaptic potentials (EPSP), >30% slow (s) EPSPs] from the myenteric plexus. Synaptic potentials were recorded significant distances aboral (fEPSPs, 25 mm; sEPSPs, 10 mm) but not oral to the stimulating site. When preparations were studied in a double-chamber bath that chemically isolated the stimulating “myenteric chamber” from the recording side “submucosal chamber,” all fEPSPs were blocked by hexamethonium in the submucosal chamber, but not by a combination of nicotinic, purinergic, and 5-hydroxytryptamine-3 receptor antagonists in the myenteric chamber. In 15% of cells, a stimulus train elicited prolonged bursts of fEPSPs (>30 s duration) that were blocked by hexamethonium. These findings suggest that most submucosal S neurons receive synaptic inputs from predominantly anally projecting myenteric neurons. These inputs are poised to coordinate intestinal motility and secretion.

Characterization of responses of neonatal sinus and AV nodes to critically timed, brief vagal stimuli

1991 ◽  
Vol 260 (2) ◽  
pp. H459-H464 ◽  
Author(s):  
S. Yamasaki ◽  
A. Stolfi ◽  
A. S. Pickoff
Keyword(s):  
Cycle Length ◽  
Cardiac Cycle ◽  
Gradual Increase ◽  
Latency Period ◽  
Atrial Pacing ◽  
Response Curves ◽  
Stimulus Train ◽  
Sinus Cycle Length ◽  
The Right

We studied the responses of sinus cycle length and atrioventricular (AV) nodal conduction to brief, critically timed vagal stimuli in 25 neonatal (9.6 +/- 3.1 days) canines. Vagal stimuli were delivered to the right or left decentralized cervical vagosympathetic trunk as either a single, brief stimulus train or a repetitive, phase-coupled train with both stimulation paradigms programmed to scan the entire cardiac cycle. The effects of brief vagal stimuli on cardiac cycle length were measured while the heart was beating spontaneously, and the vagal effects on AV nodal conduction were measured while the cycle length was held constant by atrial pacing at 300 ms. Neither changes in sinus cycle length nor AV nodal conduction demonstrated classical phase dependency, i.e., a gradual increase in the magnitude of the vagal response as stimuli are delivered progressively later in the cardiac cycle until the latency period (that point in the cardiac cycle at which vagal stimulation no longer affects the next cardiac cycle) is reached. Phase-response curves (PRCs) to single and repetitive stimuli typically exhibited either a flat response or a small decrease in magnitude as the latency period of the PRC was approached. Thus the neonatal sinus and AV node PRCs exhibit a different configuration than that reported in the adult.

Fade of cardiac responses during tonic vagal stimulation

1982 ◽  
Vol 243 (2) ◽  
pp. H219-H225 ◽  
Author(s):  
P. Martin ◽  
M. N. Levy ◽  
Y. Matsuda
Keyword(s):  
Test Stimulus ◽  
Vagal Stimulation ◽  
Conditioning Stimulus ◽  
Rest Period ◽  
Test Stimulation ◽  
Cardiac Responses ◽  
Conditioning Period ◽  
Stimulus Train ◽  
Time Courses ◽  
Inotropic Responses

We applied trains of stimuli to the vagosympathetic trunks of anesthetized dogs and studied the time courses of the resultant chronotropic and inotropic responses. These responses were maximum soon after the onset of the test stimulus train but then declined over the next 1-5 min despite continued stimulation. The fade ratio was defined as the magnitude of this decline divided by the magnitude of the maximum response. For both inotropic and chronotropic responses, maximum increased with stimulation frequency, but the fade ratio did not change. In some experiments, conditioning stimulus trains of variable duration were applied before a standard rest period, after which the test stimulus train was applied. The longer the conditioning period, the lower was the subsequent fade ratio of the inotropic responses to the test stimulation train. In other experiments, a conditioning train of 2 min was applied, and then variable rest periods were interposed before the test train was applied. The longer the rest period, the greater were the subsequent maximum and fade ratios of the inotropic responses to the test stimulus train. These results indicate that some factor persists well after the cardiac responses to a given stimulus, and this factor affects the next response to an identical vagal stimulation. The chronotropic responses faded about three times faster than the inotropic responses. Thus different mechanisms may account for the fade of the inotropic and chronotropic responses.

scholarly journals Power fatigue of the rat diaphragm muscle

2000 ◽  
Vol 89 (6) ◽  
pp. 2215-2219 ◽  
Author(s):  
Bill T. Ameredes ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
Rene Vandenboom ◽  
Gary C. Sieck
Keyword(s):  
Diaphragm Muscle ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Reduction In Force ◽  
Novel Technique ◽  
Velocity Relationship ◽  
Stimulus Train ◽  
Force Velocity

We hypothesized that decrements in maximum power output (W˙max) of the rat diaphragm (Dia) muscle with repetitive activation are due to a disproportionate reduction in force (force fatigue) compared with a slowing of shortening velocity (velocity fatigue). Segments of midcostal Dia muscle were mounted in vitro (26°C) and stimulated directly at 75 Hz in 400-ms-duration trains repeated each second (duty cycle = 0.4) for 120 s. A novel technique was used to monitor instantaneous reductions in maximum specific force (Po) andW˙max during fatigue. During each stimulus train, activation was isometric for the initial 360 ms during which Po was measured; the muscle was then allowed to shorten at a constant velocity (30% V max) for the final 40 ms, and W˙max was determined. Compared with initial values, after 120 s of repetitive activation, Po andW˙max decreased by 75 and 73%, respectively. Maximum shortening velocity was measured in two ways: by extrapolation of the force-velocity relationship ( V max) and using the slack test [maximum unloaded shortening velocity ( V o)]. After 120 s of repetitive activation, V max slowed by 44%, whereas V o slowed by 22%. Thus the decrease inW˙max with repetitive activation was dominated by force fatigue, with velocity fatigue playing a secondary role. On the basis of a greater slowing of V max vs. V o, we also conclude that force and power fatigue cannot be attributed simply to the total inactivation of the most fatigable fiber types.

The Relationship between CA2/3 and CA1 Subfields in the Stimulus Train-Induced Bursting of Hippocampal Slices

1987 ◽  
Vol 41 (3) ◽  
pp. 496-497
Author(s):  
Hisashi Kojima ◽  
Yohichi Katsuta ◽  
Satoshi Fujii ◽  
Masayoshi Kowada
Keyword(s):  
Hippocampal Slices ◽  
Stimulus Train ◽  
The Relationship

Stumbling Corrective Reaction During Fictive Locomotion in the Cat

2005 ◽  
Vol 94 (3) ◽  
pp. 2045-2052 ◽  
Author(s):  
Jorge Quevedo ◽  
Katinka Stecina ◽  
Simon Gosgnach ◽  
David A. McCrea
Keyword(s):  
Dorsal Surface ◽  
Fictive Locomotion ◽  
Step Cycle ◽  
Stimulus Train ◽  
Subsequent Step ◽  
Extensor Motoneuron ◽  
Motoneuron Activity ◽  
Hind Foot ◽  
Hip Flexor ◽  
Decerebrate Cats

An obstacle contacting the dorsal surface of a cat’s hind foot during the swing phase of locomotion evokes a reflex (the stumbling corrective reaction) that lifts the foot and extends the ankle to avoid falling. We show that the same sequence of ipsilateral hindlimb motoneuron activity can be evoked in decerebrate cats during fictive locomotion. As recorded in the peripheral nerves, twice threshold intensity stimulation of the cutaneous superficial peroneal (SP) nerve during the flexion phase produced a very brief excitation of ankle flexors (e.g., tibialis anterior and peroneus longus) that was followed by an inhibition for the duration of the stimulus train (10–25 shocks, 200 Hz). Extensor digitorum longus was always, and hip flexor (sartorius) activity was sometimes, inhibited during SP stimulation. At the same time, knee flexor and the normally quiescent ankle extensor motoneurons were recruited (mean latencies 4 and 16 ms) with SP stimulation during fictive stumbling correction. After the stimulus train, ankle extensor activity fell silent, and there was an excitation of hip, knee, and ankle flexors. The ongoing flexion phase was often prolonged. Hip extensors were also recruited in some fictive stumbling trials. Only the SP nerve was effective in evoking stumbling correction. Delivered during extension, SP stimulus trains increased ongoing extensor motoneuron activity as well as increasing ipsilateral hip, knee, and ankle hindlimb flexor activity in the subsequent step cycle. The fictive stumbling corrective reflex seems functionally similar to that evoked in intact, awake animals and involves a fixed pattern of short-latency reflexes as well as actions evoked through the lumbar circuitry responsible for the generation of rhythmic alternating locomotion.

Autonomic response to chronic electrode stimulation of cerebellum

1961 ◽  
Vol 201 (4) ◽  
pp. 697-699 ◽  
Author(s):  
J. D. Emerson ◽  
John M. Bruhn ◽  
Geraldine M. Emerson ◽  
J. O. Foley
Keyword(s):  
Autonomic Response ◽  
Bladder Pressure ◽  
P Values ◽  
Pupillary Dilatation ◽  
Pupillary Constriction ◽  
Train Duration ◽  
Stimulus Train ◽  
Steel Electrodes ◽  
Ansiform Lobule ◽  
Stimulation Of

The cerebellum was stimulated with implanted chronic concentric stainless steel electrodes in ten cats, with isolation of current to the cortex immediately beneath the electrodes. Stimulus parameters were: current density 0.5–2.55 ma/mm2, pulse duration 1–2 msec., frequency 100 cycle/sec, stimulus train duration 10–15 sec. Elevation of bladder pressure, pupillary dilatation, and pupillary constriction were obtained at P values of 10–7–10–10; depression of bladder pressure at P < 10–5. Responsive areas included ansiform lobule and vermis.

A functional analysis of dopaminergic innervation of the neurohypophysis

1981 ◽  
Vol 241 (3) ◽  
pp. E186-E190
Author(s):  
S. S. Passo ◽  
J. R. Thornborough ◽  
C. F. Ferris
Keyword(s):  
Functional Analysis ◽  
Electrical Activity ◽  
Dopaminergic Neurons ◽  
Arcuate Nucleus ◽  
Inhibitory Effect ◽  
Inhibitory Influence ◽  
Dopamine Receptor Antagonist ◽  
Neurohypophyseal Hormones ◽  
Stimulus Train ◽  
Stimulation Of

Dopaminergic neurons arising from cell bodies in the rostral arcuate nucleus of the hypothalamus have been shown to make axoaxonic contact with neurohypophyseal neurosecretory axons. In this study, electrical stimulation of the rostral arcuate nucleus depresses multiunit electrical activity recorded from neurosecretory axons within the neurohypophysis. After a single 5-s stimulus train, neurohypophyseal electrical activity is reduced to 6% of control. The superfusion of dopamine (5 micrograms/microliters) onto the neurohypophysis also has an inhibitory effect. Superfusion directly onto the neurohypophysis of the dopamine-receptor antagonist, pimozide (1 micrograms/microliters), abolishes the inhibitory effect of arcuate nucleus stimulation. These findings suggest that the dopaminergic innervation of the neurohypophysis may have an inhibitory influence on the release of neurohypophyseal hormones.

"On" and "off" responses of guinea pig ureter

1985 ◽  
Vol 248 (1) ◽  
pp. C165-C169 ◽  
Author(s):  
K. W. Hong ◽  
P. Biancani ◽  
R. M. Weiss
Keyword(s):  
Guinea Pig ◽  
Ethylenediaminetetraacetic Acid ◽  
Free Calcium ◽  
Free Solution ◽  
Stimulus Train ◽  
Electrical Stimuli

The in vitro guinea pig ureter responds to 5-s trains of electrical stimuli with two contractions: the first, an “on” response, occurs within 0.1-0.3 s after the onset of the stimulus train; the second, an “off” response, occurs 0.2-1.0 s after the termination of the stimulus train. Force decreases between the two responses during a time when the stimulus is still being delivered. Longer duration and/or higher frequencies of stimuli within the train are required to elicit the off response than the on response. Neither the on nor the off response appears to be neurally mediated, since both responses are unchanged by tetrodotoxin, phentolamine, atropine, and pyrilamine. Decreasing temperature from 37 to 22 degrees C decreases the amplitude of the on response and increases the amplitude of the off response. Calcium-free solution, 2 mM ethylenediaminetetraacetic acid (EDTA), 1 mM Mn2+, and 1 microM verapamil abolish the on response at a time at which the off response continues to persist. Conversely, 0.5 mM caffeine and 0.1 mM theophylline abolish the off response, whereas they only slightly reduce the on response. These data suggest that the on response depends on extracellular free calcium, whereas the off response is more dependent on bound or stored calcium.

Refractoriness of sural nerve in humans

2008 ◽  
Vol 86 (9) ◽  
pp. 600-605 ◽  
Author(s):  
Paige Stevens ◽  
Parveen Bawa
Keyword(s):  
Action Potential ◽  
Sural Nerve ◽  
Compound Action Potential ◽  
High Frequency Stimulation ◽  
Partial Recovery ◽  
Healthy Human ◽  
Perception Threshold ◽  
Test Response ◽  
Stimulus Train ◽  
Compound Action

High-frequency stimulation of peripheral nerve bundles is frequently used in clinical tests and physiologic experiments to study presynaptic and postsynaptic effects. To understand the postsynaptic effects, it is important to ensure that each pulse in the train is equally effective in stimulating the presynaptic nerve bundle; however, the optimal interpulse interval (IPI) and the stimulus intensity at which each pulse is equally effective in stimulating the same number of axons are not known. The magnitude of the compound action potential produced by each pulse in a train was tested on the sural nerve of 4 healthy human subjects. The stimulus train (2–4 pulses) was applied to the sural nerve at the lateral malleolus, and neural responses were recorded from just below the knee. With 2-pulse trains, families of curves between IPIs (1–6 ms) and normalized amplitudes of the second response were plotted for different stimulus intensities. Visual inspection of the data showed that the curves fell into 2 groups: with stimulus intensities <2.5× perception threshold (Th), the test response appeared partially at longer IPIs, whereas with stimulus intensities ≥3× Th, partial recovery of the test response was earlier. The interval for complete recovery was statistically the same for low- and high-intensity stimulation. With more than 2 pulses in a stimulus train (IPI = 5 ms), the amplitude of the compound action potential (CAP) was not affected significantly. These results are important in understanding both the presynaptic and postsynaptic responses when presynaptic axon bundles are stimulated at high frequencies.

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