Summary
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1.
Kinetics of activation and desensitization phases of the acetylcholine (ACh)-induced chloride current (I Cl) were studied using isolated single neurons of Japanese land snail and the “concentration clamp” technique.
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2.
The dose-response curve for the peakI Cl gave a dissociation constant of 7.1 × 10−6 M and a Hill coefficient of 1.8.
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3.
The current-voltage relationship was linear in the voltage range examined (−60 to +10 mV) and the reversal potential (E ACh) was −7.2 ± 1.5 mV (N = 10). The value was close to the calculated equilibrium potential for chloride ions (E Cl).
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4.
Both activation and desensitization phases of the ACh-inducedI Cl consisted of a single exponential at concentrations less than 3 × 10−6 M and a double exponential at higher concentrations. The time constants of both phases decreased with increasing ACh concentrations but showed no potential dependency.
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5.
The recovery from desensitization of theI Cl induced by 5 × 10−6 M ACh proceeded double exponentially, with time constants of 11 and 114 sec at a holding potential of −30 mV.
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6.
Noise analysis was performed on a steady-state current induced by 3 × 10−7 to 2 × 10−6 M ACh. The mean open time was about 60 msec at 10−6 M ACh and the single-channel conductance was 14 PS.
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7.
These results suggest that the ACh receptor-Cl channel complex in snail neurons has two binding sites with the dissociation constant of 7.1 × 10−6 M and is rapidly activated and desensitized to a steady level in the presence of the agonist.
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Ikemoto, Y., Ishizuka, S., Ono, K. et al. Kinetic analysis of acetylcholine-induced chloride current in isolated snail neurons. Cell Mol Neurobiol 8, 293–305 (1988). https://doi.org/10.1007/BF00711171
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DOI: https://doi.org/10.1007/BF00711171