Voltage controlled contractions and current voltage relations of crayfish muscle fibers in chloride-free solutions

1969 ◽  
Vol 308 (4) ◽  
pp. 291-314 ◽  
Author(s):  
J. Dudel ◽  
R. R�del
Keyword(s):  
Muscle Fibers ◽  
Crayfish Muscle ◽  
Current Voltage

Fast BK-Type Channel Mediates the Ca2+-Activated K+ Current in Crayfish Muscle

1999 ◽  
Vol 82 (4) ◽  
pp. 1655-1661 ◽  
Author(s):  
Alfonso Araque ◽  
Washington Buño
Keyword(s):  
Electrical Activity ◽  
Single Channel ◽  
Muscle Fibers ◽  
Ionic Channels ◽  
Bk Channels ◽  
Intrinsic Properties ◽  
Open Probability ◽  
Crayfish Muscle ◽  
Fast Activation ◽  
Inside Out

The role of the Ca2+-activated K+ current ( I K(Ca)) in crayfish opener muscle fibers is functionally important because it regulates the graded electrical activity that is characteristic of these fibers. Using the cell-attached and inside-out configurations of the patch-clamp technique, we found three different classes of channels with properties that matched those expected of the three different ionic channels mediating the depolarization-activated macroscopic currents previously described (Ca2+, K+, and Ca2+-dependent K+ currents). We investigated the properties of the ionic channels mediating the extremely fast activating and persistent I K(Ca). These voltage- and Ca2+-activated channels had a mean single-channel conductance of ∼ 70 pS and showed a very fast activation. Both the single-channel open probability and the speed of activation increased with depolarization. Both parameters also increased in inside-out patches, i.e., in high Ca2+concentration. Intracellular loading with the Ca2+ chelator bis(2-aminophenoxy) ethane- N, N,N′,N′-tetraacetic acid gradually reduced and eventually prevented channel openings. The channels opened at very brief delays after the pulse depolarization onset (<5 ms), and the time-dependent open probability was constant during sustained depolarization (≤560 ms), matching both the extremely fast activation kinetics and the persistent nature of the macroscopic I K(Ca). However, the intrinsic properties of these single channels do not account for the partial apparent inactivation of the macroscopic I K(Ca), which probably reflects temporal Ca2+ variations in the whole muscle fiber. We conclude that the channels mediating I K(Ca) in crayfish muscle are voltage- and Ca2+-gated BK channels with relatively small conductance. The intrinsic properties of these channels allow them to act as precise Ca2+ sensors that supply the exact feedback current needed to control the graded electrical activity and therefore the contraction of opener muscle fibers.

scholarly journals Effects of Caffeine on Crayfish Muscle Fibers

1970 ◽  
Vol 55 (5) ◽  
pp. 665-687 ◽  
Author(s):  
Dante J. Chiarandini ◽  
John P. Reuben ◽  
Lucien Girardier ◽  
George M. Katz ◽  
Harry Grundfest
Keyword(s):  
Muscle Fibers ◽  
Bathing Medium ◽  
Contractile Responses ◽  
Crayfish Muscle ◽  
Contractile System ◽  
Mn Recovery

When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM Ko). However, the fibers still respond with contraction to an increase in Ko, though with diminished tension. Addition of Mn slows recovery, but the latter is greatly accelerated during exposure of the fiber to high Ko, or after a brief challenge with high Ko. Neither the depolarization induced by the K, nor the repolarization after its removal accounts for the acceleration, which occurs only if the challenge with K had itself activated the contractile system; acceleration is blocked when contractile responses to K are blocked by reducing the Ca in the bath or by adding Mn. Recovery is accelerated by redistribution of intracellular Cl and by trains of intracellularly applied depolarizing pulses, but not by hyperpolarization. The findings indicate that two sources of Ca can be mobilized to activate the contractile system. Caffeine mobilizes principally the Ca store of the SR. Depolarizations that are induced by high Ko, by transient efflux of Cl, or by intracellularly applied currents mobilize another source of Ca which is strongly dependent upon the entry of Ca from the bathing medium. The sequestering mechanism of the SR apparently can utilize this second source of Ca to replenish its own store so as to accelerate recovery of responsiveness to a new challenge with caffeine.

scholarly journals Dual effect of L-glutamate on excitatory postjunctional membranes of crayfish muscle.

1975 ◽  
Vol 65 (5) ◽  
pp. 677-691 ◽  
Author(s):  
P S Taraskevich
Keyword(s):  
Muscle Fibers ◽  
Reversal Potential ◽  
Dual Effect ◽  
Sodium Conductance ◽  
Crayfish Muscle ◽  
Permeability Changes ◽  
Extracellular Sodium ◽  
Sodium And Potassium

Iontophoretically applied glutamate produces different excitatory postjunctional permeability changes on separate muscle fibers in a single crayfish muslce. At junctions on some fibers glutamate appears to increase the conductance to both sodium and potassium whereas at others its effect is primarily on the sodium conductance. These results obtained by studying the reversal potential for the extracellularly recorded glutamate potential under conditions of varied extracellular sodium and potassium concentrations.

Ultrastructure of nerve terminals and muscle fibers in denervated crayfish muscle

1973 ◽  
Vol 146 (2) ◽  
pp. 155-165 ◽  
Author(s):  
H. L. Atwood ◽  
C. K. Govind ◽  
G. D. Bittner
Keyword(s):  
Muscle Fibers ◽  
Nerve Terminals ◽  
Crayfish Muscle

scholarly journals Inhibition by hypertonic solutions of Ca-dependent electrogenesis in single crab muscle fibers.

1977 ◽  
Vol 70 (4) ◽  
pp. 491-505 ◽  
Author(s):  
G Suarez-Kurtz ◽  
A L Sorenson
Keyword(s):  
Time Course ◽  
Morphological Changes ◽  
Muscle Fibers ◽  
Surface Charges ◽  
Fiber Volume ◽  
Graded Responses ◽  
Hypertonic Solutions ◽  
Current Voltage ◽  
Negative Surface ◽  
Current Voltage Relationship

This study describes the effect of hypertonic solutions on isolated muscle fibers of Callinectes danae. Solutions of twice normal tonicity (2.0 T) inhibit both the normal graded membrane responses and the spikes induced by procaine, tetraethylammonium, or barium. The inhibition is maintained throughout exposure to hypertonic solutions prepared by addition of impermeant solutes such as NaCl, sucrose, or Tris-propionate, but is reversible on their withdrawal. In the presence of permeant solutes such as glycerol or acetamide, the inhibition is transient. In both cases the onset of inhibition of the depolarizing Ca electrogenesis is correlated with shrinkage of the fiber. In the case of permeant solutes, the time course of recovery of the graded responses or the spikes follows the recovery of the fiber volume. Changes in the passive electrical characteristics of the fibers due to hypertonic solutions were unrelated to the blockade of membrane Ca activation. The current-voltage relationship in hypertonic sollution revealed no increase in depolarizing K activation. Inhibition of the graded membrane responses and spikes appears to be associated with depression of Ca conductance. Hypertonic solutions might affect the activation of Ca conductance through reduction of the electric field generated by fixed negative surface charges and/or morphological changes in the T tubules. Membrane depolarization elicited little or no tension in 2.0 T solutions while caffeine contracture (10 mM) with an ampliture of 76% of the maximal contractile ability could still be elicited. This indicates that direct effects of hypertonic solutions on the contractile apparatus were not responsible for loss of tension. The latter is attributed to the inhibition of the transmembrane Ca currents.

Potassium redistribution and water movement in crayfish muscle fibers

1972 ◽  
Vol 80 (3) ◽  
pp. 267-283 ◽  
Author(s):  
George M. Katz ◽  
John P. Reuben ◽  
MacBerman ◽  
Philip B. Dunham
Keyword(s):  
Water Movement ◽  
Muscle Fibers ◽  
Crayfish Muscle
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