Acetylcholine-activated Cl- channel in the Chara tonoplast.
Acetylcholine has long been suggested to play a role in controlling physiological processes in plants, but no mechanism has been shown for its action. We show here that a chloride channel in the tonoplast (vacuolar membrane) of Chara corallina responds to acetylcholine. The channel has a conductance of 45 pS. The effect of acetylcholine is enhanced by nicotine, with the open probability increasing from 0.05 in the presence of 4 mM acetylcholine to 0.3 in the presence of 4 mM acetylcholine + 6 mM nicotine. Some effects of acetylcholine were seen at concentrations as low as 20 microM, with a maximum effect between 1 and 10 mM. In the intact cell, acetylcholine prolongs the depolarized phase of the action potential. We propose that this acetylcholine-gated channel has evolved separately from the mammalian acetylcholine-gated channel, and suggest that this represents a third form of acetylcholine signal transduction, after the nicotinic and muscarinic pathways in animal systems.
Gong
X-Q
XQ
Department of Biological Sciences, University at Buffalo, Suny, Buffalo NY 14260, USA.
Bisson
M A
MA
D000109:Acetylcholine / Q000819:agonists / Q000502:physiology*; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D056890:Eukaryota / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015398:Signal Transduction; D014617:Vacuoles / Q000187:drug effects / Q000502:physiology*
D018118:Chloride Channels; D009538:Nicotine; D000109:Acetylcholine; D011188:Potassium