Properties of non‐junctional acetylcholine receptor channels on innervated muscle of Xenopus laevis.

Brehm, Paul; Kullberg, R; Moody-Corbett, F

doi:10.1113/jphysiol.1984.sp015222

Cited by 145 publications

(80 citation statements)

References 27 publications

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“…Based on pooled data from single-exponential histograms, the mean open time increased e-fold for every 62.3 & 7.1 mV (n = 7 sites). This voltage dependency of open time is similar to that seen for the 40 pS channels at stages 19-30 in myotomal muscle and also to that of the 60 pS channels appearing later in myotomal muscle (Brehm et al, 1984b;Owens and Kullberg, 1989).…”

Section: Gating Kineticssupporting

confidence: 59%

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Three conductance classes of nicotinic acetylcholine receptors are expressed in developing amphibian skeletal muscle

Owens

Kullberg

1989

J. Neurosci.

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Two previously described classes of nicotinic AChRs in vertebrate skeletal muscle have conductances of 40 and 60 pS. In addition, a third conductance class of AChR channels is present in developing Xenopus muscle. This class appears to represent an independent channel type, rather than a subconductance state of the larger conductance channels. The channel has a slope conductance of 25 pS and a reversal potential of about 0 mV membrane potential. Its kinetic properties resemble those of the 40 pS channels present in early embryonic myotomal muscle. The channel has a mean open time of about 6 msec (at 40 mV applied potential). The open time is dependent on membrane potential and increases e-fold for every 60 mV of hyperpolarization. Consecutive openings were often separated by brief closures of about 0.4 msec in duration. The identity of the channel as a nicotinic AChR was established by blocking the channel openings with alpha-BTX and by demonstrating bursting and desensitization in the presence of high agonist concentrations. In some muscles (e.g., extraocular), this channel may be a predominant form at early developmental stages and could therefore be important to the function of developing synapses in those muscles.

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Section: Gating Kineticssupporting

confidence: 59%

“…We routinely tested patches for the presence of stretch-activated channels (Brehm et al, 1984b) by applying suction to the recording pipette during the recording. To avoid confusing AChRs and stretch-activated channels, records containing channel activity elicited by suction were not analyzed.…”

Section: Methodsmentioning

confidence: 99%

Three conductance classes of nicotinic acetylcholine receptors are expressed in developing amphibian skeletal muscle

Owens

Kullberg

1989

J. Neurosci.

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“…It is worth noting in this respect that applying suction to patches showing spontaneous activity did not increase channel activity further in a graded manner like that shown in Fig. 5 The channels in C2 myoblasts and myotubes are similar to the stretch-activated channels in adult skeletal muscle (Brehm, Kullberg & Moody-Corbett, 1984;Guharay & Sachs, 1984, 1985. They are cation-selective and have a conductance in Na+-containing saline of 30-35 pS.…”

Section: Discussionmentioning

confidence: 64%

Stretch‐sensitive channels in developing muscle cells from a mouse cell line.

Franco

Lansman

1990

The Journal of Physiology

110

121

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4. Channel openings occurred as bursts of brief openings and closings separated by much longer closed periods. Closed-time histograms were best fitted with three exponential components, while histograms of burst duration were best fitted with two exponential components, reflecting the short and long bursts in the single-channel records.5. Applying suction to the patch electrode while recording at steady negative membrane potentials produced channel openings to discrete current levels. Mean channel open probability depended linearly on the square of the applied pressure and was greater at positive membrane potentials. The permeability of the channel to monovalent and divalent cations was indistinguishable from the spontaneous activity recorded at steady negative potentials.6. Channel activity recorded from cell-attached patches in the absence of applied pressure depended on membrane potential increasing -e-fold per 38 mV with depolarization. Analysis of the kinetics of the response to membrane potential * To whom correspondence should be addressed. MS 7995A. FRANCO AND J. B. LANSMAN showed that the depolarization reduced the duration of the slowest component of the closed-time distribution.7. The lanthanide cation gadolinium (Gd) reduced the amplitude of the unitary currents in a concentration-dependent manner. The amplitudes of both inward and outward currents were reduced to the same extent suggesting block is voltageindependent. Gd produced half-maximal inhibition of the unitary current at 6 aM.8. The fraction of recordings from cell-attached patches showing stretch-activated and spontaneous channel activity was determined at morphologically identifiable stages of myogenesis. Stretch-sensitive activity was high in myoblasts plated at low density, but decreased during development. The fraction of patches showing spontaneous activity was low and remained constant during muscle differentiation.9. The results are discussed in terms of the possibility that cation channels in developing muscle cells are gated by changes in membrane tension and voltage. The role of Ca2+-permeable cation channels in providing a pathway for Ca2+ influx during the early stages of myogenesis is considered.

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“…decays were apparently well fitted by single-exponential curves probably reflects our inability to resolve two components by eye when one component largely outweighs the other. In general, the single-exponential decays fell within the limits of the fast and slow channel open times previously described by spectral analysis of ACh noise and by single channel recordings from myotomal muscle (Brehm, Kullberg & Moody-Corbett, 1984;Brehm, Kidokoro & Moody-Corbett, 1984;Kullberg & Kasprzak, 1985).…”

Section: Development Of End-plate Currentsmentioning

confidence: 99%

Comparative development of end‐plate currents in two muscles of Xenopus laevis.

Kullberg¹,

Owens²

1986

The Journal of Physiology

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SUMMARY1. The development of miniature end-plate currents (m.e.p.c.s) was studied in the superior oblique and interhyoideus muscles of Xenopus laevis. An analysis of m.e.p.c. decays shows that each muscle possesses its own characteristic programme ofend-plate current development.2. In the superior oblique, the exponential decay constants of m.e.p.c.s were initially about 3 ms; they declined within half a day to 1 ms and remained at that value for six weeks. They then gradually became longer, reaching a mean value of 1-7 ms at late metamorphosis.3. In the interhyoideus, m.e.p.c. decay constants were initially about 6 ms. They declined in less than one day to a mean value of 2-6 ms and remained there for the following seven weeks. Upon completion of metamorphosis, the decay constants underwent a further decrease to about 1 ms.4. In both muscles, the changes in m.e.p.c. decays were correlated with developmental changes in muscle contraction speeds, as measured by maximum twitch frequencies.5. The above changes inend-plate currents in the superior oblique andinterhyoideus muscles are discussed in terms of the development of acetylcholine receptor channel gating and acetylcholinesterase activity.

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Properties of non‐junctional acetylcholine receptor channels on innervated muscle of Xenopus laevis.

Cited by 145 publications

References 27 publications

Three conductance classes of nicotinic acetylcholine receptors are expressed in developing amphibian skeletal muscle

Three conductance classes of nicotinic acetylcholine receptors are expressed in developing amphibian skeletal muscle

Stretch‐sensitive channels in developing muscle cells from a mouse cell line.

Comparative development of end‐plate currents in two muscles of Xenopus laevis.

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