Transverse Electric Impedance of the Squid Giant Axon

Curtis, Howard J.; Cole, Kenneth S.

doi:10.1085/jgp.21.6.757

Cited by 102 publications

(49 citation statements)

References 10 publications

(16 reference statements)

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“…The values obtained (5 ~F/cm 2, Katz, 1948;8 /~F/ cm ~, Fatt and Katz, 1951) are high relative to the values (about I /zF/cm ~) obtained for nerve cells (Curtis and Cole, 1938;Hodgkin and Rushton, 1946;Hodgkin, Huxley, and Katz, 1952). It has been suggested that a major part of this capacitance resides in the tubule membranes and is in parallel with the true surface capacity (Falk and Fatt, 1964), which requires that the membranes be connected in some way.…”

Section: Musclesmentioning

confidence: 75%

The Sarcoplasmic Reticulum and Transverse Tubules of the Frog's Sartorius

Peachey

1965

The Journal of Cell Biology

650

364

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The sarcoplasmic reticulum of the frog's sartorius muscle was examined by electron microscopy following sequential fixation in glutaraldehyde and osmium tetroxide and embedding in Epon. The earlier results of Porter and Palade on Ambystoma muscle were confirmed in the sartorius. In addition, the transverse tubules were observed to be continuous across the width of the fiber, a set of flat intermediate cisternae was seen to connect the terminal cisternae to the longitudinal tubules in the A band, and the continuous reticulum collar at the center of the A band was found to be perforated by circular and elongated pores (the fenestrated collar). The transverse tubules have a volume about 0.3 per cent of the fiber volume, and a surface area about 7 times the outer cylindrical surface area for a fiber 100 µ in diameter. The terminal cisternae, the intermediate cisternae, and the longitudinal tubules together with the fenestrated collar each have a volume of 4 to 5 per cent of the fiber volume and a surface area 40 to 50 times the outer surface area of a fiber 100 µ in diameter. Some evidence for continuity of the transverse tubules with the fiber surface is presented, but this is thought to be not so convincing as evidence presented by others. The results are discussed in terms of a possible mechanism for a role of the transverse tubules and sarcoplasmic reticulum in excitation-contraction coupling, as suggested by their morphology and a variety of physiological studies. In this scheme, the transverse tubules are thought to be electrically coupled to the terminal cisternae, so that depolarization of the fiber surface spreads inward along the transverse tubules and to the terminal cisternae, initiating the release of a contraction-activating substance.

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Section: Musclesmentioning

confidence: 75%

The Sarcoplasmic Reticulum and Transverse Tubules of the Frog's Sartorius

Peachey

1965

The Journal of Cell Biology

650

364

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“…(1) declines smoothly by about 0 6 #F cm-2. This observation is by no means new (Curtis & Cole, 1938;Cole, 1976;Taylor, 1965;Takashima & Schwan, 1974) but its explanation is still unclear. Perfusion of the axon with CsF and sucrose solution does not affect this result (D. A.…”

Section: Discussionmentioning

confidence: 96%

Some effects of aliphatic hydrocarbons on the electrical capacity and ionic currents of the squid giant axon membrane.

Haydon¹,

Requena²,

Urban³

1980

The Journal of Physiology

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SUMMARY1. The electrical properties of squid giant axons were examined by means of admittance bridges at frequencies from 0.5 to 300 kHz. A simple equivalent circuit was used to estimate the membrane capacity.2. The calculated membrane capacities decreased monotonically over the whole frequency range.3. At 100 kHz and higher frequencies the membrane capacity was independent of potential.4. At frequencies greater than 20 kHz, exposure of the axons to saturated or 0-9 saturated solutions of n-pentane (275-306 AM) reduced the capacity per unit area by 0 1-0-15 ,#F cm-2.5. At 1 kHz the effect of the saturated pentane solutions depended on the membrane potential. In axons having potentials between -60 and zero mV the pentane solutions lowered the capacity, whereas for potentials between -160 and -60 mV they produced little or no change.6. Saturated solutions of n-hexane, n-heptane and n-octane exhibited qualitatively similar, but quantitatively smaller influences on the membrane capacity, the changes declining as the chain length increased.7. Under voltage clamp, the peak inward and steady-state outward currents were partially suppressed by the hydrocarbons. Saturated solutions of n-pentane usually reduced the former (reversibly) by 60-80 % and the latter by 20-40 %. Solutions of n-hexane, n-heptane and n-octane appeared to have successively less effect. Except in deteriorating axons, none of the hydrocarbons produced any consistent changes in the passive membrane resistance, the resting potential or in the reversal potential of the transient inward current.8. Both the changes in the clamp currents and in the membrane capacity were largely, though not usually completely, reversible. In the hydrocarbon solutions the axons deteriorated more rapidly than normal.9. The responses of axons of Doryteuthis plei to the hydrocarbons were very similar to those of Loligo forbesi with the exception that for the former all observed changes were some five times faster.

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“…In various studies, the specific membrane capacitance was measured in the range 0.7-1.3·µF·cm -2 (Curtis and Cole, 1938;Gentet et al, 2000). Assuming the specific membrane capacitance of 1·µF·cm -2 (0.01·pF·µm -2 ), the surface capacitance is 122·pF.…”

Section: Solutions and Chemicalsmentioning

confidence: 99%

CCA-1, EGL-19 and EXP-2 currents shape action potentials in theCaenorhabditis eleganspharynx

Shtonda

Avery

2005

Journal of Experimental Biology

135

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SUMMARY The pharynx of Caenorhabditis elegans is a tubular muscle controlled by its own set of neurons. We developed a technique to voltage clamp the pharyngeal muscle and demonstrate by analyzing mutants that the pharyngeal action potential is regulated by three major voltage-gated currents, conducted by a T-type calcium channel CCA-1, an L-type calcium channel EGL-19 and a potassium channel EXP-2. We show that CCA-1 exhibits T-type calcium channel properties: activation at -40 mV and rapid inactivation. Our results suggest that CCA-1's role is to accelerate the action potential upstroke in the pharyngeal muscle in response to excitatory inputs. Similarly to other L-type channels, EGL-19 activates at high voltages and inactivates slowly; thus it may maintain the plateau phase of the action potential. EXP-2 is a potassium channel of the kV family that shows inward rectifier properties when expressed in Xenopus laevisoocytes. We show that endogenous EXP-2 is not a true inward rectifier - it conducts large outward currents at potentials up to +20 mV and is therefore well suited to trigger rapid repolarization at the end of the action potential plateau phase. Our results suggest that EXP-2 is a potassium channel with unusual properties that uses a hyperpolarization threshold to activate a regenerative hyperpolarizing current.

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Transverse Electric Impedance of the Squid Giant Axon

Cited by 102 publications

References 10 publications

The Sarcoplasmic Reticulum and Transverse Tubules of the Frog's Sartorius

The Sarcoplasmic Reticulum and Transverse Tubules of the Frog's Sartorius

Some effects of aliphatic hydrocarbons on the electrical capacity and ionic currents of the squid giant axon membrane.

CCA-1, EGL-19 and EXP-2 currents shape action potentials in theCaenorhabditis eleganspharynx

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