Blockade by 2,2',2''-tripyridine of the nicotinic acetylcholine receptor channels in embryonic Xenopus muscle cells.
1. The effects of 2,2',2''-tripyridine on the nicotinic acetylcholine (ACh) receptor channels were studied in the cultured myocytes of 1-day-old Xenopus embryos. 2. 2,2',2''-Tripyridine depressed the amplitude of iontophoretic ACh-induced current at a low frequency of 0.7 Hz stimulation and it not only decreased the initial responses but also enhanced the run-down of ACh-induced current at higher frequency stimulation of 7 Hz and 30 Hz. 3. Single ACh channel recordings showed that 2,2',2''-tripyridine decreased the channel conductance, the opening frequency and mean open time of both types of low- and high-conductance channels. 4. These results suggest that the blocking actions of 2,2',2''-tripyridine on ACh receptor channels in the skeletal muscle may contribute to the depression of the nerve-evoked contraction of the mouse diaphragm as reported previously.
Hsu
K S
KS
Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei.
Fu
W M
WM
Lin-Shiau
S Y
SY
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects; D007478:Iontophoresis; D008564:Membrane Potentials / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D018733:Nicotinic Antagonists; D011725:Pyridines / Q000494:pharmacology*; D014981:Xenopus
D007473:Ion Channels; D009466:Neuromuscular Blocking Agents; D018733:Nicotinic Antagonists; D011725:Pyridines; C013278:2,2',2''-terpyridine; D000109:Acetylcholine