ISSN:
1432-2013
Keywords:
Receptor
;
Cholinergic
;
Ionic channels
;
Voltage clamp
;
Membrane current
;
Muscles
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The current contributions of individual ionic channels can be measured by electrically isolating a small patch of membrane. To do this, the tip of a small pipette is brought into close contact with an enzymatically cleaned membrane of a hypersensitive amphibian or mammalian muscle fiber. Current flowing through the pipette is measured. If the pipette contains cholinergic agonist at μ-molar concentrations, square pulse current waveforms can be observed which represent the activation of individual acetylcholine-receptor channels. The square pulses have amplitudes of 1 to 3 pA and durations of 10–100 ms. In order to obtain the necessary resolution, a delicate compromise had to be found between different experimental parameters. Pipettes with 1–3 μm internal diameter and a steep final taper had to be used, extensive enzyme treatment was necessary, and conditions had to be found in which channels open at a relatively low frequency.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584247
