Influence of the patch pipette glass on single acetylcholine channels recorded from Xenopus myocytes.

The type of glass used to fabricate patch pipettes influences the kinetic properties of single-channel currents activated by acetylcholine in Xenopus myocytes. In patches formed with hard glass pipettes, the opening rate decreased in a time-dependent manner. Such decrease was most pronounced for the low-conductance channel. In addition, longer-duration events of this form of channel dropped out faster than shorter-duration events and, as a consequence, the apparent channel open time became shorter during the recording period. These effects were not observed in patches formed with soft glass pipettes.