Neuromuscular Transmission in the Longitudinal Layer of Somatic Muscle in the Earthworm

1969 ◽  
Vol 50 (2) ◽  
pp. 417-430
Author(s):  
T. HIDAKA ◽  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Equilibrium Potential ◽  
Muscle Fibres ◽  
Free Solution ◽  
Excitatory Junction Potentials ◽  
Potential Level

1. The properties of the miniature inhibitory junction potentials (M.I.J.P.) and the inhibitory junction potentials (I.J.P.) elicited by nerve stimulation were investigated in longitudinal muscle fibres of the earthworm. 2. Histograms of the amplitudes(mean,0.71mV.) and the intervals (mean, 101 msec.) of the M.I.J.P. showed skew curves. 3. The polarity of the M.I.J.P. was reversed at about -60 mV. When the external chloride was substituted by glutamate the M.I.J.P. disappeared as an external chloride concentration of 15-20 mM, and further reduction reversed their polarity. 4. Picrotoxin blocked generation of the M.I.J.P. and the I.J.P. 5. The cross-over point of the current-voltage relation curves, with and without presence of GABA, occurred at a membrane potential of -54 mV. in potassium-free solution, and at -56 mV. in potassium-excess solution. 6. Iontophoretic application of GABA produced slow hyperpolarization. The equilibrium potential of the GABA-potential was about -60 mV. During the time course of the GABA-potentials an increase in the membrane conductance was observed. 7. Miniature excitatory junction potentials (M.E.J.P.) and excitatory junction potentials (E.J.P.) could be recorded from the longitudinal muscle, but the M.E.J.P. were rare. 8. D-tubocurarine, but not atropine, completely blocked the M.E.J.P. and E.J.P. Prostigmine enhanced their amplitude and duration. 9. The reversal potential level for the E.J.P. was about 0 mV. Sodium-free solution lowered the reversal potential level for the M.E.J.P. to -20 mV.

Relative contributions of passive equilibrium and active transport to the distribution of chloride in mammalian cortical neurons

1988 ◽  
Vol 60 (1) ◽  
pp. 105-124 ◽  
Author(s):  
S. M. Thompson ◽  
R. A. Deisz ◽  
D. A. Prince
Keyword(s):  
Time Constant ◽  
Cortical Neurons ◽  
Time Course ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Gamma Aminobutyric Acid ◽  
The Mean ◽  
Mean Time

1. Active and passive factors affecting the chloride gradient of cortical neurons were assessed using intracellular recordings from neurons in slices of cingulate cortex maintained in vitro. The chloride equilibrium potential (ECl-) was estimated indirectly from the reversal potentials of responses to perisomatic gamma-aminobutyric acid (GABA) application and the Cl(-)-dependent inhibitory postsynaptic potential (IPSP). Under control conditions the mean resting potential (Vm; -69.7 mV) was not significantly different than the mean IPSP reversal potential (EIPSP; -70.1 mV). 2. Increasing the external potassium concentration ([K+]o) from 1 to 10 mM shifted the mean EIPSP from -80.4 to -61.8 mV. The mean EIPSP was approximately equal to the mean Vm at all [K+]oS. The conditions of Donnan equilibrium are not met in [K+]o less than 10 mM. 3. Polarization of Vm up to 20 mV away from EIPSP for 4 min with maintained current injection had no significant effect on EIPSP. 4. The GABA reversal potential was maintained 37-52 mV less negative than Vm after equilibration in saline in which the external chloride concentration had been reduced from 133 to 5 mM by substitution with isethionate. Vm and input resistance were not significantly different from control values in cells recorded under these conditions. 5. We conclude that Cl- is not passively distributed in cortical neurons, perhaps due to a low resting Cl- permeability. 6. Impalement with electrodes containing 2 M KCl resulted in a rapid 10 mV depolarizing shift in EIPSP that then remained relatively constant. Intracellular iontophoresis of Cl- resulted in a further depolarizing shift of EIPSP of 5-10 mV that returned to control in less than 1 min. The time course of recovery of IPSP amplitude could be fit with a single exponential having a mean time constant of 6.9 +/- 1.5 s and was independent of the amount of Cl- injected or stimulation frequency. 7. Reductions in temperature from 37 to 32 degrees C significantly increased the mean time constant of IPSP recovery from Cl- injection to 11.1 +/- 3.3 s, corresponding to Q10 = 2.6.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris

1974 ◽  
Vol 60 (2) ◽  
pp. 453-467
Author(s):  
C. D. DREWES ◽  
R. A. PAX
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Lumbricus Terrestris ◽  
Single Pulse ◽  
Repetitive Stimulation ◽  
Muscle Fibres ◽  
Mechanical Responses ◽  
Segmental Nerve ◽  
Earthworm Lumbricus ◽  
Stimulation Of

1. Patterns of innervation of the longitudinal muscle of the earthworm, Lumbricus terrestris, were examined electrophysiologically. 2. The longitudinal musculature of a segment is innervated by relatively few axons, a fast and slow axon being present in segmental nerve I and in the double nerve, segmental nerve II-III. 3. Single-pulse stimulation of the fast axon produces large external muscle potentials and small twitch-like contractions, which with repetitive stimulation are antifacilitating. 4. Repetitive stimulation of the slow axon produces large, slowly developing and sustained mechanical responses, with electrical and mechanical responses showing summation and facilitation. 5. The amplitude and time course of slow mechanical responses are related to the frequency of stimulation. 6. Individual longitudinal muscle fibres are innervated by either the fast or slow axon in a segmental nerve, or by both fast and slow axons. 7. No evidence was found for peripheral inhibitory innervation of the longitudinal muscle.

Miniature Excitatory Junction Potentials in the Somatic Muscle of the Earthworm, Pheretima Communissima, in Sodium Free Solution

1969 ◽  
Vol 51 (1) ◽  
pp. 107-118
Author(s):  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Reversal Potential ◽  
Muscle Layer ◽  
Physiological Solution ◽  
Free Solution ◽  
Somatic Muscle ◽  
Longitudinal Muscle Layer ◽  
High Calcium ◽  
Excitatory Junction Potentials ◽  
External Potassium ◽  
External Calcium

1. Miniature excitatory junction potentials (m.e.j.p.s) could be recorded from the longitudinal muscle layer of earthworm in sodium-free solution. 2. The amplitude and frequency of the m.e.j.p.s indicated the diffuse innervation and random release of the chemical transmitter from the nerve terminals. 3. Generation of the m.e.j.p.s was prevented by treatment with D-tubocurarine, but not by atropine and picrotoxin. 4. Hyperpolarizations of the membrane by applications of inward current increased the frequency and amplitude of the m.e.j.p.s in sodium-free solution. 5. The reversal potential level for the m.e.j.p.s in sodium-free solution was -;20 mV., and this value was 20 mV. negative to that measured in physiological solution. Low-potassium solution shifted the reversal potential levels in a more negative and high-calcium in a less negative direction. 6. The change of the reversal potential produced by a tenfold change of the external potassium concentration was 24.5 mV., and that by change of the external calcium concentration was 17 mV.

Ionic conductances of monkey solitary cone inner segments

1994 ◽  
Vol 71 (2) ◽  
pp. 656-665 ◽  
Author(s):  
T. Yagi ◽  
P. R. Macleish
Keyword(s):  
Membrane Potential ◽  
Potassium Current ◽  
Time Course ◽  
Reversal Potential ◽  
Light Response ◽  
Membrane Properties ◽  
Equilibrium Potential ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Tetraethylammonium Ions

1. The membrane properties of cone inner segments dissociated enzymatically from monkey retina were studied under voltage-clamp conditions using patch pipettes in the whole-cell clamp configuration. 2. A noninactivating, voltage-gated calcium current was evoked at potentials positive to -60 mV and peaked between -30 and -20 mV when barium was substituted for calcium. Cadmium (50 microM) but not nickel (50 microM) blocked the current. 3. A large calcium-activated anion current (IAn) was observed when the membrane potential was set to a level between -60 and 30 mV. The reversal potential of IAn was 0 mV with chloride as the sole anion and about -30 and -40 mV when methanesulfonate and D-aspartate, respectively, replaced intracellular chloride to set the equilibrium potential for chloride at -50 mV. IAn inactivated and oscillated when the membrane potential was maintained at depolarized levels, contrary to calcium-activated anionic currents seen in photoreceptors of other species. 4. A sustained-type potassium current was activated by depolarizations positive to -50 mV. The time course of activation and deactivation were voltage dependent. This potassium current was partially blocked by 20 mM tetraethylammonium ions. 5. A transient potassium current was activated by depolarizations positive to -20 mV. This current was blocked by 4-aminopyridine (2 mM) and inactivated with a time constant of approximately 500 ms. The amplitude in response to voltage steps to 45 mV was decreased by prepulses to voltages more positive than -30 mV. 6. Hyperpolarization negative to -65 mV activated an inward current that was completely blocked by external cesium (10 mM). The reversal potential suggested a conductance mechanism permeable to both sodium and potassium ions. 7. A calcium-activated potassium current, which was found in salamander photoreceptors, was not detected. 8. The presence of these conductances is expected to influence the membrane potential and the time course of the light response in monkey cones.

Effect of low extracellular calcium and ryanodine on muscle contraction of the mouse during postnatal development

1991 ◽  
Vol 69 (9) ◽  
pp. 1294-1300 ◽  
Author(s):  
Josette Dangain ◽  
Ian R. Neering
Keyword(s):  
Time Course ◽  
Age Groups ◽  
Isometric Tension ◽  
Muscle Fibres ◽  
Gradual Change ◽  
Free Solution ◽  
Cobalt Ions ◽  
Contraction Speed ◽  
Single Twitch ◽  
Isometric Twitch

We have examined the effects of low Ca2+ solutions, Co2+, and ryanodine on the isometric tension and contraction speed of isolated, developing mouse EDL muscles. Twitch responses of young muscles (7–14 days postnatal) were more sensitive to lowered [Ca2+]0 than those of more fully developed muscles (22–35 days postnatal). Responses of EDL muscles from a middle-aged group (15–21 days postnatal) were intermediate between the two other groups. Overall, the time course of contraction in a single twitch was accelerated by low [Ca2+]o. Ca2+-free solution induced a 7.95 and 9.25 mV depolarization in young and "old" muscle fibres, respectively. The presence of cobalt ions (5 mM) in the Krebs solution had a similar effect as Ca2+-free Krebs in terms of reduction of the isometric twitch and tetanic tensions of EDL muscles from the various age groups. In contrast, the shortening of the contraction time seen with Ca2+-free solution did not take place following exposure to Co2+-containing solutions. Finally, young (7–14 days postnatal) muscles were less sensitive to the inhibitory action of ryanodine on the twitch compared with more fully developed muscles (22–35 days postnatal). Taken together, our results indicate that from birth to maturity, there is a gradual change in the spectrum of calcium utilization for the contractile process.Key words: mammalian muscle, calcium, development, ryanodine, contraction, sarcoplasmic reticulum.

scholarly journals Shift of Intracellular Chloride Concentration in Ganglion and Amacrine Cells of Developing Mouse Retina

2006 ◽  
Vol 95 (4) ◽  
pp. 2404-2416 ◽  
Author(s):  
Ling-Li Zhang ◽  
Hemal R. Pathak ◽  
Douglas A. Coulter ◽  
Michael A. Freed ◽  
Noga Vardi
Keyword(s):  
Gaba Receptors ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Amacrine Cells ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Mouse Retina ◽  
Intracellular Chloride ◽  
Excitatory Action ◽  
Intracellular Chloride Concentration

GABA and glycine provide excitatory action during early development: they depolarize neurons and increase intracellular calcium concentration. As neurons mature, GABA and glycine become inhibitory. This switch from excitation to inhibition is thought to result from a shift of intracellular chloride concentration ([Cl−]i) from high to low, but in retina, measurements of [Cl−]i or chloride equilibrium potential ( ECl) during development have not been made. Using the developing mouse retina, we systematically measured [Cl−]i in parallel with GABA's actions on calcium and chloride. In ganglion and amacrine cells, fura-2 imaging showed that before postnatal day (P) 6, exogenous GABA, acting via ionotropic GABA receptors, evoked calcium rise, which persisted in HCO3−- free buffer but was blocked with 0 extracellular calcium. After P6, GABA switched to inhibiting spontaneous calcium transients. Concomitant with this switch we observed the following: 6-methoxy- N-ethylquinolinium iodide (MEQ) chloride imaging showed that GABA caused an efflux of chloride before P6 and an influx afterward; gramicidin-perforated-patch recordings showed that the reversal potential for GABA decreased from −45 mV, near threshold for voltage-activated calcium channel, to −60 mV, near resting potential; MEQ imaging showed that [Cl−]i shifted steeply around P6 from 29 to 14 mM, corresponding to a decline of ECl from −39 to −58 mV. We also show that GABAergic amacrine cells became stratified by P4, potentially allowing GABA's excitatory action to shape circuit connectivity. Our results support the hypothesis that a shift from high [Cl−]i to low causes GABA to switch from excitatory to inhibitory.

The ionic mechanism of the slow outward current in Aplysia neurons

1985 ◽  
Vol 54 (2) ◽  
pp. 449-461 ◽  
Author(s):  
J. R. Huguenard ◽  
K. L. Zbicz ◽  
D. V. Lewis ◽  
G. J. Evans ◽  
W. A. Wilson
Keyword(s):  
Reversal Potential ◽  
Outward Current ◽  
Membrane Conductance ◽  
Ion Concentration ◽  
Equilibrium Potential ◽  
Potassium Efflux ◽  
Aplysia Neurons ◽  
K Current ◽  
K Concentration ◽  
K Currents

A slow outward current associated with spike frequency adaptation has been studied in the giant Aplysia neurons R2 and LP1. The current was observed during 60-s voltage clamp commands to potentials just below spike threshold. The slow outward current shows a marked voltage dependence at membrane potential less negative than -40 mV. The slow outward current is associated with increased membrane conductance. The K+ sensitivity of the slow outward current was studied by varying the extracellular K+ concentration and also by measuring potassium efflux with a K+-sensitive electrode. Both procedures indicated that the slow outward current was K+ dependent. Tail currents following the activation of the slow outward current were examined. They were shown to have a similar potassium sensitivity as the slow outward current and had a reversal potential near the potassium equilibrium potential for these cells. The sensitivity of the slow outward current to known blockers of K+ currents, tetraethylammonium and 4-aminopyridine, was tested. The sensitivity was much less than that reported for other K+ currents. The sensitivity of the slow outward current to changes of the extracellular concentrations of Na+ and Cl- ions, as well as electrogenic pump inhibitors, was tested. The results indicate that the slow outward current is much less sensitive to these changes than to the manipulations of the extracellular K+ ion concentration. We tested the sensitivity of this current to manipulations of intracellular and extracellular Ca2+ ion concentrations. We found that the current persisted at a slightly reduced level in the absence of extracellular calcium or in the presence of calcium blocking agents, cobalt and lanthanum. Intracellular injection of the calcium chelator EGTA at a concentration sufficient to block the Ca2+-dependent K+ current, seen after a brief (1.4-s) burst of action potentials, had minimal effects on the slow outward current. Procedures thought to increase intracellular Ca2+ were tested. We found that exposure of the cell to solutions containing elevated Ca2+ concentrations for prolonged periods increased the slow outward current. Also, treatment with drugs thought to elevate intracellular Ca2+ increased the slow outward current. In conclusion, the slow outward current results from an increased K+ conductance.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanical Properties of the Longitudinal and Circular Muscle in the Earthworm

1971 ◽  
Vol 55 (1) ◽  
pp. 101-110
Author(s):  
N. TASHIRO
Keyword(s):  
Mechanical Properties ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Tonic Contraction ◽  
Muscle Fibres ◽  
Field Stimulation ◽  
Free Solution ◽  
Tension Development ◽  
Phasic Contraction

1. The mechanical properties of the longitudinal and circular muscles of the earthworm, Pheretima communissima, were studied in various solutions. 2. In the longitudinal muscle, field stimulation elicited two distinct waves of tension development, i.e. phasic and tonic contractions. But in the circular muscle, these components were not distinguishable. 3. The phasic contraction in the longitudinal muscle increased in sodium-free (tris) solution while the tonic contraction was abolished. Neither the phasic nor the tonic contraction, however, was influenced by tetrodotoxin (3 x 10-6 M), d-tubocurarine (1.4 x 10-5M), or atropine (3.5 x 10-5 M). 4. The contraction in the circular muscle was suppressed in sodium-free solution and also by tetrodotoxin (3 x 10-6 M), but was not affected by d-tubocurarine (1.4 x 10-5 M) or by atropine (3.5 x 10-5M). 5. It is speculated that the phasic contraction of the longitudinal muscle is triggered by a calcium spike, and the contraction in the circular muscle is preceded by a sodium spike in muscle fibres.

Effects of γ-Aminobutyric Acid and Picrotoxin on the Permeability of the Longitudinal Muscle of the Earthworm to Various Anions

1969 ◽  
Vol 51 (2) ◽  
pp. 363-375
Author(s):  
Y. ITO ◽  
H. KURIYAMA ◽  
N. TASHIRO
Keyword(s):  
Membrane Potential ◽  
Response Curve ◽  
Longitudinal Muscle ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Input Resistance ◽  
Ringer Solution ◽  
Aminobutyric Acid ◽  
Inhibitory Junction Potential ◽  
Junction Potential

The effects of GABA and picrotoxin on the input resistance of the muscle of the earthworm, Pheretima communissima in Ringer solution and in solutions containing various foreign anions were observed. 1. Substitution of Cl- by I- and Br- reduced the input resistance and hyperpolarized the membrane. Although anions larger than chloride in hydrated size increased the input resistance, no change of the membrane potential was observed. 2. GABA reduced the input resistance of the membrane and picrotoxin increased it in Ringer solution. The dose-response curve for the changes of the input resistance under various concentrations of GABA shifted parallel-wise under treatment with picrotoxin. 3. In the presence of foreign anions which had larger hydration size than Br-, GABA reduced the input resistance. Picrotoxin did not, however, increase the input resistance when the solutions contained anions of smaller hydration size than ClO4-. 4. Reversal potential levels for the miniature inhibitory junction potential in various concentrations of chloride were measured. The change of the reversal potential levels produced by a tenfold change of chloride concentration was 25 mV.

A Critical Study of the Evidence for Peripheral Inhibitory Axons in Insects

1968 ◽  
Vol 49 (1) ◽  
pp. 201-222
Author(s):  
P. N. R. USHERWOOD
Keyword(s):  
Potassium Concentration ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Critical Study ◽  
Muscle Fibres ◽  
High Concentration ◽  
Bathing Medium

1. The metathoracic anterior coxal adductor (a.c.a.) muscle of the locust and the grasshopper is innervated by a peripheral inhibitory axon similar to the inhibitory axon which innervates the metathoracic extensor tibiae muscles of these insects. No evidence was found to justify calling this axon an inhibitory-conditioning axon. 2. Hyperpolarizing inhibitory postsynaptic potentials (IPSPs) are normally recorded from a.c.a. muscle fibres during stimulation of this axon, and if the bathing medium contains a high concentration of potassium ions the tonic fibres of the a.c.a. muscle relax slightly during inhibitory stimulation. 3. The IPSPs are chloride potentials and can be converted to depolarizing responses by changing either the external or internal chloride concentration of the a.c.a. muscle fibres. Depolarizing IPSPs are frequently accompanied by small contractions of a.c.a. muscle fibres innervated by the inhibitory axon. 4. The a.c.a. muscle fibres are permeable to potassium and chloride ions but influx of potassium chloride is much faster than efflux. Therefore when a.c.a. muscle fibres are loaded with chloride by exposing them to high-K saline (20-100 m-equiv. potassium/l.) and are then returned to normal (10 m-equiv. potassium/l.) saline the internal chloride concentration remains elevated for some time and during this period the equilibrium potential for the inhibitory response is less negative than the resting potential and the IPSPs are depolarizing. 5. Depolarizing IPSPs are usually recorded from a.c.a. muscle fibres of locusts and grasshoppers when these fibres are transferred from their normal bathing medium, haemolymph, to 10 K saline. Probably the main reason for this reversal of the IPSPs is the entry of KCl into the muscle fibres during dissection of the nerve-muscle preparations. Large quantities of KCl would be released into the environment surrounding these preparations from muscle fibres cut and removed during dissection. 6.Depolarizing IPSPs were more frequently recorded from muscle fibres of grassfed locusts than from fibres of starved locusts. The potassium concentration of haemolymph of grass fed locusts is higher than that of locust saline (10 m-equiv./l.). 7. The potassium concentration of locust haemolymph presumably fluctuates in vivo but these fluctuations are too slow to affect the sign of the IPSP. The IPSPs are therefore always hyperpolarizing in vivo. 8. The effect of changes in the potassium concentration of the bathing medium on the magnitude and polarity of the IPSP could account for the diverse responses recorded previously from a.c.a. muscle fibres of locusts and grasshoppers.

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