4-aminopyridine and l-cis-diltiazem block the cGMP-activated K+ channels closed by light in the molluscan extra-ocular photoreceptors.
The cGMP-activated K+ channels closed by light lead to the depolarizing photocurrent of photoreceptors in the Onchidium ganglion. Whole-cell current records showed that external application of 100-200 microM 4-aminopyridine or 200-400 microM l-cis-diltiazem completely blocked the macroscopic photocurrent at any depolarizing and hyperpolarizing potentials. Single-channel current recordings suggested that both 4-aminopyridine and l-cis-diltiazem act to block the cGMP-activated K+ channels in their open state from inside the cell.
Gotow
T
T
Department of Physiology, Faculty of Medicine, Kagoshima University, Japan.
Nishi
T
T
Murakami
M
M
D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D006152:Cyclic GMP / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D008974:Mollusca / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017956:Photoreceptor Cells, Invertebrate / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
D002121:Calcium Channel Blockers; D015221:Potassium Channels; D015761:4-Aminopyridine; D004110:Diltiazem; D006152:Cyclic GMP