scholarly journals REPETITIVE STIMULATION OF A NODE OF RANVIER UNDER ELECTROTONUS

1961 ◽  
Vol 11 (4) ◽  
pp. 419-426 ◽  
Author(s):  
Seikichi KITAMURA
Keyword(s):  
Node Of Ranvier ◽  
Repetitive Stimulation ◽  
Stimulation Of

Intracellular analysis of trigeminal motoneuron rhythmical activity during stimulation of pontomedullary reticular formation in anesthetized guinea pig

1989 ◽  
Vol 62 (6) ◽  
pp. 1225-1236 ◽  
Author(s):  
S. M. Gurahian ◽  
S. H. Chandler ◽  
L. J. Goldberg
Keyword(s):  
Reticular Formation ◽  
Short Duration ◽  
Field Potential ◽  
Membrane Potentials ◽  
Repetitive Stimulation ◽  
Jaw Movements ◽  
Postsynaptic Potentials ◽  
Duration Stimulus ◽  
Long Duration ◽  
Stimulation Of

1. The effects of repetitive stimulation of the nucleus pontis caudalis and nucleus gigantocellularis (PnC-Gi) of the reticular formation on jaw opener and closer motoneurons were examined. The PnC-Gi was stimulated at 75 Hz at current intensities less than 90 microA. 2. Rhythmically occurring, long-duration, depolarizing membrane potentials in jaw opener motoneurons [excitatory masticatory drive potential (E-MDP)] and long-duration hyperpolarizing membrane potentials [inhibitory masticatory drive potentials (I-MDP)] in jaw closer motoneurons were evoked by 40-Hz repetitive masticatory cortex stimulation. These potentials were completely suppressed by PnC-Gi stimulation. PnC-Gi stimulation also suppressed the short-duration, stimulus-locked depolarizations [excitatory postsynaptic potentials (EPSPs)] in jaw opener motoneurons and short-duration, stimulus-locked hyperpolarizations [inhibitory postsynaptic potentials (IPSPs)] in jaw closer motoneurons, evoked by the same repetitive cortical stimulation. 3. Short pulse train (3 pulses; 500 Hz) stimulation of the masticatory area of the cortex in the absence of rhythmical jaw movements activated the short-latency paucisynaptic corticotrigeminal pathways and evoked short-duration EPSPs and IPSPs in jaw opener and closer motoneurons, respectively. The same PnC-Gi stimulation that completely suppressed rhythmical MDPs, and stimulus-locked PSPs evoked by repetitive stimulation to the masticatory area of the cortex, produced an average reduction in PSP amplitude of 22 and 17% in jaw closer and opener motoneurons, respectively. 4. PnC-Gi stimulation produced minimal effects on the amplitude of the antidromic digastric field potential or on the intracellularly recorded antidromic digastric action potential. Moreover, PnC-Gi stimulation had little effect on jaw opener or jaw closer motoneuron membrane resting potentials in the absence of rhythmical jaw movements (RJMs). PnC-Gi stimulation produced variable effects on conductance pulses elicited in jaw opener and closer motoneurons in the absence of RJMs. 5. These results indicate that the powerful suppression of cortically evoked MDPs in opener and closer motoneurons during PnC-Gi stimulation is most likely not a result of postsynaptic inhibition of trigeminal motoneurons. It is proposed that this suppression is a result of suppression of activity in neurons responsible for masticatory rhythm generation.

Repetitive stimulation of optic nerve and lateral geniculate synapses

1959 ◽  
Vol 1 (6) ◽  
pp. 534-555 ◽  
Author(s):  
P.O. Bishop ◽  
W. Burke ◽  
W.R. Hayhow
Keyword(s):  
Optic Nerve ◽  
Repetitive Stimulation ◽  
Lateral Geniculate ◽  
Stimulation Of

Proportion of muscles spindles supplied by skeletofusimotor axons (beta-axons) in peroneus brevis muscle of the cat

1975 ◽  
Vol 38 (6) ◽  
pp. 1390-1394 ◽  
Author(s):  
F. Emonet-Denand ◽  
Y. Laporte
Keyword(s):  
Neuromuscular Junctions ◽  
Muscle Fibers ◽  
Repetitive Stimulation ◽  
Motor Axon ◽  
Dynamic Sensitivity ◽  
Conduction Velocities ◽  
Peroneus Brevis ◽  
Stimulation Of

Of 32 cat peroneus brevis spindles, 23 (72%) were found to be supplied by a least 1 skeletofusimotor or beta-axon. A motor axon was identified as skeletofusimotor when repetitive stimulation of it elicited both the contraction of extrafusal muscle fibers and as acceleration of the discharge of primary ending, which persisted after selective block of the neuromuscular junctions of extrafusal muscle fibers. The block was obtained by stimulating single axons at 400-500/s for a few seconds. Of 135 axons supplying extrafusal muscle fibers, 24 (18%) were shown to be beta-axons; 22 beta-axons had conduction velocities ranging from 45 to 75 m/s. All but three beta-axons increased the dynamic sensitivity of primary endings. Beta-innervated spindles may also be supplied by dynamic gamma-axons.

Tetanic hyperpolarization of single medullated nerve fibers in sodium and lithium

1976 ◽  
Vol 231 (4) ◽  
pp. 1033-1038 ◽  
Author(s):  
GM Schoepfle
Keyword(s):  
Steady State ◽  
Interspike Interval ◽  
Nerve Fibers ◽  
Repetitive Stimulation ◽  
Time Dependent ◽  
Potassium Ions ◽  
Current Densities ◽  
Medullated Nerve Fiber ◽  
Sodium And Potassium ◽  
Stimulation Of

Repetitive stimulation of a single medullated nerve fiber of Xenopus yields a succession of postspike voltage-time curves which are nearly coincident until attainment of a voltage that corresponds to that of the maximum attained by the normal postspike undershoot. Initially the interspike potential returns toward a resting level after this brief phase of hyperpolarization. However, as tetanization proceeds, a pattern of hyperpolarization develops with the result that, in the tetanic steady state, there exists a progressive hyperpolarization throughout each interspike interval. Extent of postspike hyperpolarization in terms of a deviation deltaVm from the resting level of membrane potential is approximated by the variation deltaVm = delta[MNa + MK]/[GNa + GK] where MNa and MK are current densities associated with active pumping of sodium and potassium ions and GNa and GK are corresponding time-dependent leak conductances. Tetanic hyperpolarization is reversibly abolished by cyanide and by exposure to lithium Ringer. Eventual reappearance of tetanic hyperpolarization in the presence of lithium Ringer suggests lithium pumping.

Effects of prolonged repetitive stimulation of median, ulnar and peroneal nerves

2010 ◽  
Vol 41 (6) ◽  
pp. 785-793 ◽  
Author(s):  
Fusun Baumann ◽  
Robert D. Henderson ◽  
Fred Tremayne ◽  
Nicole Hutchinson ◽  
Pamela A. McCombe
Keyword(s):  
Repetitive Stimulation ◽  
Stimulation Of

Dynamics of Excitatory Transmitter Release: Analysis of Synaptic Responses in CA3 Hippocampal Neurons After Repetitive Stimulation of Afferent Fibers

1998 ◽  
Vol 79 (4) ◽  
pp. 1977-1988 ◽  
Author(s):  
Marco Canepari ◽  
Enrico Cherubini
Keyword(s):  
Transmitter Release ◽  
Hippocampal Neurons ◽  
Repetitive Stimulation ◽  
Patch Clamp Technique ◽  
Afferent Fibers ◽  
Presynaptic Mechanisms ◽  
Release Analysis ◽  
Excitatory Transmitter ◽  
Stimulation Of ◽  
Synaptic Responses

Canepari, Marco and Enrico Cherubini. Dynamics of excitatory transmitter release: analysis of synaptic responses in CA3 hippocampal neurons after repetitive stimulation of afferent fibers. J. Neurophysiol. 79: 1977–1988, 1998. The patch-clamp technique (whole cell configuration) was used to record excitatory postsynaptic currents (EPSCs) evoked by repetitive stimulation (4 pulses at 50-ms intervals) of afferent fibers in the stratum lucidum-radiatum. Different synaptic behaviors (EPSC patterns) were classified in terms of facilitation or depression of the mean amplitude of the second, third, and fourth EPSC with respect to the previous one. A large variety of EPSC patterns was observed by stimulating different afferent fibers. Experiments with the mGluR2/mGluR3 agonist 2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) (1 μM), a compound that reduces release at mossy but not at associative commissural fibers and therefore allows to identify the origin of synaptic responses, showed that particular EPSC patterns could not be associated to the activation of a specific type of synaptic input. To investigate the role of the probability of release in the dynamics of synaptic activity, the extracellular calcium concentration was varied from 0.8 to 4 mM in several experiments. EPSC patterns dominated by depression, characteristics of high release probability conditions, could be observed in the majority of the cases in the presence of higher calcium concentrations. A quantitative model for dynamics of transmitter release has been developed. Experimental results were compared with data computed with the model taking into account the probability of release and the time course of reavailability. This work indicates that short-term changes of presynaptic conditions occurring during a train of action potentials can account for the high variability of EPSC responses. The model that is proposed also suggests a general method of experimental data analysis to investigate the possible presynaptic mechanisms underlying long-lasting changes in synaptic efficacy.

scholarly journals The "late" Ca channel in squid axons.

1981 ◽  
Vol 78 (6) ◽  
pp. 683-700 ◽  
Author(s):  
L J Mullins ◽  
J Requena
Keyword(s):  
Steady State ◽  
Repetitive Stimulation ◽  
Test Solution ◽  
Ca Channel ◽  
Normal Concentration ◽  
Giant Axons ◽  
Light Production ◽  
High K ◽  
K Response ◽  
Stimulation Of

Squid giant axons were injected with aequorin and then treated with seawater containing 50 mM Ca and 100-465 mM K+. Measurements of light production suggested a phasic entry of Ca as well as an enhanced steady-state aequorin glow. After a test K+ depolarization, the aequorin-injected axon was stimulated for 30 min in Li seawater that was Ca-free, a procedure known to reduce [Na]i to about one-half the normal concentration. Reapplication of the elevated K+ test solution now showed that the Ca entry was virtually abolished by this stimulation in Li. A subsequent stimulation of the axon in Na seawater for 30 min resulted in recovery of the response to depolarization by high K+ noted in a normal fresh axon. In axons first tested for a high K+ response and then stimulated in Na seawater for 30 min (where [Na]i increases approximately 30%), there was approximately eight fold enhancement in this response to a test polarization. Axons depolarized with 465 mM K seawater in the absence of external Ca for several minutes were still capable of producing a large phasic entry of Ca when [Ca]0 was made 50 mM, which suggests that it is Ca entry itself rather than membrane depolarization that produced inactivation. Responses to stimulation at 60 pulses/s in Na seawater containing 50 mM Ca are at best only 5% of those measured with high K solutions. The response to repetitive stimulation is not measurable if [Ca]o is made 1 mM, whereas the response to steady depolarization is scarcely affected.

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