Neuromuscular Transmission in a Sea Anemone

1966 ◽  
Vol 45 (2) ◽  
pp. 305-319
Author(s):  
ROBERT K. JOSEPHSON
Keyword(s):  
Action Potentials ◽  
Repetitive Stimulation ◽  
Muscle Action ◽  
Electrical Potentials ◽  
Effective Pair ◽  
Suction Electrode ◽  
The Individual ◽  
Minimum Interval ◽  
Oral Disk ◽  
Stimulation Of

1. Brief electrical potentials can be recorded from a suction electrode over the marginal sphincter or over a tentacle of the anemone Calliactis polypus following appropriate stimulation of the anemone. These potentials are thought to be muscle action potentials because they precede contraction by about 12 msec. (29-31° C.) and their size is smoothly graded with the size of the contraction. 2. The tentacles and sphincter are activated by a through-conducting system in the oral disk and column. As with other anemones studied, two stimuli are required to evoke sphincter contraction. The maximum interval between an effective pair of stimuli is about 600 msec, and the sphincter potential and contraction increase with decreasing intervals to a minimum interval (as short as 15 msec.) below which there is no response to the second shock. Tentacles behave similarly except that they often produce small potentials and sometimes tiny contractions to single stimuli. 3. During repetitive stimulation the muscle potentials facilitate and the individual contractions both facilitate and sum. The tentacle musculature becomes maximally active earlier in a stimulus burst than does the sphincter.

Multiple conducting systems and the control of behaviour in the brain coral Meandrina meandrites (L.)

1978 ◽  
Vol 200 (1139) ◽  
pp. 193-216 ◽  
Keyword(s):  
Pulse Frequency ◽  
Repetitive Stimulation ◽  
The Other ◽  
Nerve Net ◽  
Level Of Activity ◽  
Suction Electrode ◽  
Intense Light ◽  
The Brain ◽  
Oral Disk ◽  
Stimulation Of

Extracellular suction electrode recordings from tentacles of Meandrina provide evidence for three conducting systems. One system may be the colonial nerve net. It is through-conducting and occasionally gives multiple responses to mechanical and electrical stimulation. The other two systems are also normally through-conducting but they conduct very slowly and are termed slow systems. One slow system (SSo) is in the oral disk and the other (SSc) is in the tissue covering the thecal ridges (coenosarc). SSo pulses travel throughout the interconnected oral disk regions of the colony but also enter the SSc. SSc pulses travel over the entire coenosarc but cannot enter the SSo. Both slow systems are present in the tentacles. Repetitive stimulation of the SSo evokes oral disk expansion and tentacle extension, seemingly identical to the expansion that normally occurs at night when the colony shows tentacular feeding. Repetitive stimulation of the SSc also evokes slight tentacle extension but more noticeably causes the coenosarc to become turgid. Many colonies show coenosarc expansion during the day and this may alter the exposure of symbiotic zooxanthellae to sunlight. The SSo and SSc are spontaneously active and both show a marked increase in pulse frequency when exposed to dissolved food substances. The level of activity in each system may also be modified by changes in light intensity and the SSc and SSo may thus control respectively diurnal and nocturnal expansion of different parts of the colony. The colonial nerve net appears to coordinate fast and slow contractions. Intense light can increase the level of spon­taneous activity in the nerve net.

Repetitive stimulation induced potentiation of excitatory transmission in the rat dorsal horn: an in vitro study

1994 ◽  
Vol 71 (1) ◽  
pp. 216-228 ◽  
Author(s):  
S. Jeftinija ◽  
L. Urban
Keyword(s):  
Peripheral Nerve ◽  
Dorsal Horn ◽  
High Intensity ◽  
Action Potentials ◽  
Dorsal Root ◽  
Low Frequency ◽  
Nerve Trunk ◽  
Primary Afferents ◽  
Repetitive Stimulation ◽  
Stimulation Of

1. The effects of repetitive stimulation of primary afferents in lumbar dorsal roots on synaptic transmission in the dorsal horn (DH) were studied in a rat spinal cord slice-dorsal root ganglion (DRG)-peripheral nerve trunk preparation by the use of intracellular recording from neurons (n = 115) of the spinal dorsal horn (depth 147 +/- 139, mean +/- SD). All DH neurons were excited synaptically by electrical stimulation of the dorsal root or the peripheral nerve trunk. The electrical shocks were calibrated to produce activation either of large fibers (10–20 V, 0.02 ms) or the whole fiber population including unmyelinated afferents (supramaximal stimulus: > 35 V, 0.5 ms). Postsynaptic potentials induced by low intensity repetitive stimulation of primary afferents at frequencies below 5 Hz failed to produce a prolonged change in the resting membrane potential. In 97/115 DH neurons, slow excitatory postsynaptic potentials (EPSP)--evoked by high intensity low-frequency repetitive stimulation (0.1–2 Hz) of primary afferents--summated, producing a prolonged cumulative depolarization. In the remaining 18/115 DH neurons, high intensity low-frequency stimulation produced a cumulative hyperpolarizing response. 2. In 22 of 97 neurons that responded to high intensity repetitive stimulation with a cumulative depolarization, wind-up in the firing of action potentials was recorded. In all but two experiments, neurons that responded with wind-up to stimulation of one root responded with wind-up to stimulation of the adjacent dorsal root. In 14/22 wind-up neurons, the synaptic response to high intensity stimulation of primary afferents was composed of a short latency EPSP, followed by an inhibitory postsynaptic potential (IPSP), followed by a slow EPSP. The decrease of the amplitude and duration of the IPSP obtained during train stimulation did not seem to contribute to facilitation of transmission induced by repetitive stimulation. 3. The wind-up in firing of action potentials was followed by a prolonged potentiation of synaptic transmission in tetanized synapses. A test of other, adjacent primary afferents revealed that these synapses in the neurons in the superficial laminae had not undergone potentiation. This “synaptic specificity” of post-wind-up potentiation suggested that the mechanism for the induction of stimulation-dependent changes in the excitability of the DH neuron is presynaptic to the recorded-from neuron. 4. In a concentration of 0.5 microM and higher, tetrodotoxin (TTX) applied to sensory neurons selectively blocked action potentials in large myelinated primary afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Contractions of frog tonus fibers and their modification by length changes

1990 ◽  
Vol 258 (4) ◽  
pp. C618-C621
Author(s):  
E. Bozler
Keyword(s):  
Fast Response ◽  
Nerve Fibers ◽  
Repetitive Stimulation ◽  
Length Changes ◽  
The Individual ◽  
Isotonic Contractions ◽  
Stimulation Of

Isometric and isotonic contractions of the tonus fibers of the frog were recorded using anodal block of the nerve fibers of the twitch fibers. Repetitive stimulation produced a contraction with a very slow rising phase because the individual responses were very weak. The first two or three stimuli usually did not give a visible response at all. However, if the twitch fibers were also stimulated, the responses of the tonus fibers were many times stronger and faster, but only under isotonic conditions. This indicates that the large increase in the responses of the tonus fibers was produced by the passive shortening caused by the contraction of the twitch fibers. A strong and fast response of the tonus fibers was also obtained if during stimulation of the tonus fibers the muscle was made to shorten by diminishing the load. It is suggested that the enormous effect of shortening is due to the regenerating action of shortening previously demonstrated.

Sustained potential shifts and paroxysmal discharges in hippocampal formation

1985 ◽  
Vol 53 (4) ◽  
pp. 1079-1097 ◽  
Author(s):  
G. G. Somjen ◽  
P. G. Aitken ◽  
J. L. Giacchino ◽  
J. O. McNamara
Keyword(s):  
Action Potentials ◽  
Hippocampal Formation ◽  
Repetitive Stimulation ◽  
Tissue Slices ◽  
Fascia Dentata ◽  
Population Spikes ◽  
Anesthetized Rats ◽  
Freely Moving ◽  
Stimulation Of

Paroxysmal firing was provoked by electric stimulation of afferent pathways in hippocampal formation of intact, urethan-anesthetized rats, of freely moving unanesthetized rats, and in hippocampal tissue slices in vitro. The electric responses of fascia dentata and CA3 zone of the hippocampus of urethan-anesthetized rats were recorded with extracellular microelectrodes. Paroxysmal discharges were provoked by stimulating the ipsilateral angular bundle. During repetitive stimulation, intercurrent paroxysmal discharges (IPaD) took the form of compound action potentials (population spikes) of large amplitude, provoked by but not locked in time to the stimulus pulses. IPaD was often but not always followed by paroxysmal after-discharge (PaAD), usually consisting of bursts of population spikes, sometimes superimposed on a slow wave. Stimulus pulses that were not strong enough to evoke population spikes when applied singly could provoke the paroxysmal firing of large amplitude spikes when applied repetitively. The liminal frequency to provoke paroxysmal firing, with 10-s train duration and with pulses evoking 60 to 80% of maximal amplitude focal postsynaptic potential (PSP) waves, varied between 6 and 15 Hz in urethan-anesthetized rats. The outbreak of IPaD was always accompanied by a marked sustained potential (SP) shift. The polarity of the paroxysmal SP shift was the opposite of the polarity of the PSP waves. We conclude that the extracellular paroxysmal SP shifts in fascia dentata are probably generated mainly by current flowing from the dendritic trees toward the cell somata of granule cells. The amplitude of the population spikes fired during paroxysmal discharges could reach 30-40 mV, indicating the precise coincidence of the impulses fired by many neurons. These spikes often arose without a detectable preceding synaptic potential. We conclude that the synchronization of the action potentials fired by granule and pyramidal cells during paroxysmal discharge is probably due to electric interaction among the neurons. In unanesthetized freely moving rats IPaD and PaAD consisting of bursts of population spikes were provoked. These were similar to those observed in urethan-anesthetized rats. Motor seizures provoked in kindled rats were associated with intense and prolonged spike bursts followed by spikeless positive waves recorded in the granule cell layer of fascia dentata. In hippocampal tissue slices maintained in vitro, paroxysmal firing could be provoked in CA1 zone by repetitive stimulation of Schaffer collaterals. IPaD and PaAD could be provoked in some slices exposed to normal (3.5 mM) [K+] and in all slices exposed to elevated (5.5 or 7.0 mM) [K+].(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Human neuromuscular junction on micro-structured microfluidic devices implemented with a custom micro electrode array (MEA)

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Pauline Duc ◽  
Michel Vignes ◽  
Gérald Hugon ◽  
Audrey Sebban ◽  
Gilles Carnac ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Action Potentials ◽  
Electrode Array ◽  
Microfluidic Devices ◽  
Muscle Action ◽  
Human Motor ◽  
Micro Electrode Array ◽  
Stimulation Of

Microfluidic devices were coupled with custom MEA and used for co-culture of human motor neurons and muscles. This allowed to assess human NMJ activity by electrical stimulation of axons and recording of subsequent muscle action potentials.

Neuromuscular Properties of Mesenteries from the Sea-Anemone Metridium

1969 ◽  
Vol 50 (1) ◽  
pp. 151-168
Author(s):  
E. A. ROBSON ◽  
R. K. JOSEPHSON
Keyword(s):  
Action Potentials ◽  
Neuromuscular Junctions ◽  
Sea Anemone ◽  
Retractor Muscle ◽  
Muscle Action ◽  
Stimulus Interval ◽  
Nerve Net ◽  
Slow Contraction ◽  
Oral Disk ◽  
Muscle Potential

1. A method is described for a simultaneous electrical and mechanical recording from isolated mesenteries of the sea-anemone Metridium senile (L.). 2. The retractor muscle gives quick and slow contractions. Shock intervals of 0.15-2 sec. produce facilitated twitches on all stimuli after the first, usually followed by a slow contraction. Trains of stimuli at lower frequencies are followed by slow contractions only. Slow contractions may also arise spontaneously. 3. Two types of potential were found using external suction electrodes, provisionally interpreted as nerve-net impulses and muscle action potentials. The first is an all-or-none compound pulse, whose brief components summate (1-3 msec, height up to 0.4 mV.). Conduction speed in an expanded anemone would be 70-120 cm./sec. at 14-16° C., corresponding to that of the through-conduction system. The second always precedes a twitch and is a smooth, graded potential lasting 50-100 msec. Its size, up to 1.2 mV., is inversely related to stimulus interval, but unlike the quick mechanical rseponse it shows but slight initial facilitation. A muscle potential follows a nerve-net impulse and is propagated at the same speed. The refractory period of the nerve-net probably exceeds that of the muscle. Potentials showing similar features have been recorded from the oral disk and tentacles. 4. These results support the suggestion that the sites of facilitation and initiation of contractions are neuromuscular junctions throughout the retractor muscle. Quick contractions are co-ordinated by the nerve-net, whereas it is possible that slow contractions, however initiated, may at least in part be propagated in the muscle itself.

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