Acetylcholine noise in cultured chick myoballs: a voltage clamp analysis.

Abstract

SUMMARY1. Large spherical muscle cells were grown in vitro by allowing dissociated chick myoblasts to fuse in suspension culture.2. Myoball membranes could be adequately voltage clamped even in the face of large inward currents (ca. 100 nA) induced by ACh.3. The single channel conductance, y, estimated from the ratio of the mean to the variance of ACh currents was 25-40 pmho at temperatures between 250 and 37 0C. 4. Spectra of ACh current fluctuations declined with 1/f 2. The mean channel open time (7r) estimated from the half-power frequency was 2 msec at 37 0C and -90 mV holding potential. At lower membrane potentials 7 was decreased and on hyperpolarization r was prolonged.

A transition temperature for acetylcholine channel conductance in chick myoballs.

“…VACh, determined by interpolation, was -5 mV. The same result was obtained in four other cells, and we conclude that VACh is the same at 5 0C as at 37 0C (Fischbach & Lass, 1978). -2~~-0 inFig.…”

Morphology of long‐term denervated rat soleus muscle and the effect of chronic electrical stimulation.

“…An alternative possibility is that those new fibres which established connections with the connective tissue and which were subjected to stretch developed sarcomeres whereas those fibres which were not subjected to stretch failed to form sarcomeres. A similar phenomenon is observed when myotubes in tissue culture are prevented from attaching to the bottom of the culture dish ('myoballs'; Fischbach & Lass, 1978). Activity in the stimulated muscles might act in the same way as stretch and maintain sarcomere structure.…”

The mechanism of steroid anaesthetic (alphaxalone) block of acetylcholine‐induced ionic currents

“…The results of this study show that the steroid anaesthetic alphaxalone blocks the ACh-induced rea I I _ sponse in cultured chick myoballs (Fischbach & Lass, 1978), ED50 = 6.0ptM. At the molecular level, alphaxalone produces an 'all or none' block of the ionic channel and reduces the number of available channels for a given dose of ACh.…”

“…Cell culture and electrophysiological techniques and the analysis of ACh-induced current fluctuations have been described in preceding papers (Fischbach & Lass, 1978). Briefly, spherical multinucleated myoballs were prepared by allowing mononucleated precursor cells to fuse in suspension culture.…”

“…We have described, in this paper, the effects of alphaxalone on the acetylcholine (ACh)-induced response in voltage clamped 'myoballs' (Fischbach & Lass, 1978) in culture. The molecular action of alphaxalone was studied by acetylcholine 'noise' analysis and double pulse conditioning experiments.…”