An upper limit to the number of sodium channels in nerve membrane?

Moore, John W.; Narahashi, Toshio; Shaw, T. I.

doi:10.1113/jphysiol.1967.sp008126

Cited by 165 publications

(70 citation statements)

References 8 publications

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“…A comparison of the values obtained with labelled toxin with corresponding values based on the uptake of unlabelled toxin for rabbit nerve (Keynes et at. 1971) and lobster nerve (Moore et al 1967) yielded satisfactory agreement, which was felt to be adequate validation of the labelled TTX and STX experiments.…”

Section: J M Ritchie R B Rogart and G R Strichartzmentioning

confidence: 99%

“…Following early determinations of the amount of unlabeled toxin taken up by various tissues from single concentrations of toxin (Moore, Narahashi & Shaw, 1967;Keynes, Ritchie & Rojas, 1971), complete binding curves describing the uptake of toxin over a large range of toxin concentrations became possible, with the use of radioactively labelled TTX and STX (Hafemann, 1972;Colquhoun, Henderson & Ritchie, 1972;Henderson, Ritchie & Strichartz, 1973; Aliers, . Using toxin labelled by a modified Wilzbach method, Colquhoun et al (1972) and Henderson et al (1973) showed that there was a saturable component of binding of each toxin to nerve membranes whose equilibrium dissociation constant was consistent with that determined in electrophysiological experiments for the interaction between the toxin and the sodium channel.…”

Section: J M Ritchie R B Rogart and G R Strichartzmentioning

confidence: 99%

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A new method for labelling saxitoxin and its binding to non-myelinated fibres of the rabbit vagus, lobster walking leg, and garfish olfactory nerves.

Ritchie¹,

Rogart²,

Strichartz³

1976

The Journal of Physiology

195

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SUMMARY 1.A new method of labelling saxitoxin (STX) is described, based on transfer of tritium from tritiated water to the toxin.2. The radiochemical purity of the labelled toxin has been directly determined, rather than being based on indirect biochemical means, as in previous experiments with Wilzbach-labelled STX and TTX.3. The specific activity of the labelled toxin, 66 d.p.m.f-mole-1, corresponds with one tritium atom per molecule STX, an improvement of about 300-fold over other means of labelling TTX and STX.4. The binding of this toxin to rabbit, lobster and garfish olfactory nerve fibres has been re-examined. 5. The density of sodium channels calculated on the basis of the binding of the toxin is about four to six-times the values previously reported.

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Section: J M Ritchie R B Rogart and G R Strichartzmentioning

confidence: 99%

Section: J M Ritchie R B Rogart and G R Strichartzmentioning

confidence: 99%

A new method for labelling saxitoxin and its binding to non-myelinated fibres of the rabbit vagus, lobster walking leg, and garfish olfactory nerves.

Ritchie¹,

Rogart²,

Strichartz³

1976

The Journal of Physiology

195

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“…The number of these channels is still uncertain. Using the specific binding capacity of tetrodotoxin (TTX) to Na + channels (19,22), it has been reported that 1 #m ~ of axon surface membrane contains no more than 75 Na + sites in rabbit vagus, 45 in crab nerve, and 36 in lobster nerve (walking leg) (19). Similar values are given for the K + channels (67 K + channels/~m 2 in squid giant axons) (1).…”

Section: Figttre 7 Elongated Protrusion On the Axon Surface Membrane mentioning

confidence: 99%

Excitable Membrane Ultrastructure

Peracchia

1974

The Journal of Cell Biology

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A B S T R A C TCross-sectioned and cross-fractured crayfish axons display regions in which axon and Schwann cell surface membranes are regularly curved and project into the axoplasm. At these regions (projections) the two membranes run precisely parallel, separated by a gap of 130-140 ~.. Longitudinal fractures through the axons expose the inner fractured surface of either the internal (face A) or the external (face B) leaflet of axon and adjacent Schwann cell surface membranes. On both membranes the projections appear as elongated structures oriented with the long axis parallel to the long axis of the nerve fiber. On face A of the axon surface membrane they are seen as elongated indentations 0.5-1.2-~m long, 0.12-0.15-~m wide. The indentations contain parallel chains of globules. The chains repeat every 120-125 ,~ and are oriented obliquely in such a way that if one looks at the axon surface from the extracellular space, the axis of the chains is skewed counterclockwise to the long axis of the indentations by an acute angle (most often 55-60°). The globules repeat along the chain every 80-85 .~. Globules of adjacent chains are in register in such a way that the axis on which globules of neighboring chains are aligned forms an angle of 75-85 ° with the axis of the chains. The complex structure can be defined as a globular array with a rhomboidal unit cell of 80-85 × 120-125 .~. On face B of the axon surface membrane the complementary image of these structures is seen. The projections of the Schwann cell surface membrane also contain groupings of globules; however, these differ from those in the axonal projections in size, pattern of aggregation, and fracture properties. Several possible interpretations of the meaning of these membrane specializations could be proposed. They could be: (a) structures involved in the mechanism of excitation, (b) regions of presumed metabolic couplings, and (c) areas of cell-to-cell adhesion. I N T R O D U C T I O NThe surface membranes of most nerve and muscle cells are called excitable membranes, because of their ability to initiate and conduct electrical impulses. This property (excitability) is the consequence of vohage-dependent changes in sodium and potassium conductances across the membrane (16). The most widely accepted hypothesis attributes the conductance changes to the sudden opening of hydrophilic channels existing in the membrane, to provide selective ionic pathways between the cytoplasmic and the extracellular environment (18, as review).

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“…Measurement of the binding by nerve of tetrodotoxin (TTX), which specifically blocks sodium channels, is an obvious first step; and recently attempts have been made to provide in this way an upper D. COLQUHOUN AND J. M. RITCHIE limit for the number of sodium channels in lobster (Moore, Narahashi & Shaw, 1967; Keynes, Ritchie & IRojas, 1971), crab (Keynes et al 1971), and rabbit (Keynes et al 1971) nerves. The problem with these, as with all binding studies, is to decide how much of the observed binding is to the specific receptors mediating the physiological effect.…”

Section: Introductionmentioning

confidence: 99%

The interaction at equilibrium between tetrodotoxin and mammalian non‐myelinated nerve fibres

Colquhoun¹,

Ritchie²

1972

The Journal of Physiology

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4. An alternative method of computing K that makes rather different assumptions gives a similar low value.5. Despite the low value for K, a TTX concentration of at least 100 nM is needed to block conduction completely and this seems to be related to the fact that conduction is not completely blocked until the external sodium concentration falls below 7 % of its value in normal Locke.6. The minimum sodium concentration needed to support conduction increased with temperature.

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An upper limit to the number of sodium channels in nerve membrane?

Cited by 165 publications

References 8 publications

A new method for labelling saxitoxin and its binding to non-myelinated fibres of the rabbit vagus, lobster walking leg, and garfish olfactory nerves.

A new method for labelling saxitoxin and its binding to non-myelinated fibres of the rabbit vagus, lobster walking leg, and garfish olfactory nerves.

Excitable Membrane Ultrastructure

The interaction at equilibrium between tetrodotoxin and mammalian non‐myelinated nerve fibres

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