title: Effects of potassium channel blockers on the acetylcholine-induced currents in dissociated outer hair cells of guinea pig cochlea.
abstract: Much physiological evidence is available to show that acetylcholine (ACh) hyperpolarizes the outer hair cells (OHCs) of guinea pig cochlea and induces Ca2+-activated K+ currents. In this study, using the nystatin perforated patch-clamp technique, we investigated the effects of various K+ channel blockers on the ACh-induced currents (I[ACh]) in dissociated OHCs of guinea pig cochlea. The I(ACh) were inhibited by apamin in a concentration-dependent manner. The half-maximal inhibitory concentration for apamin on the ACh-induced response was 1.59 x 10(-9) M. Charybdotoxin and iberiotoxin had no inhibitory effect on the I(ACh) The inhibitory potency of the various K+ channel blockers on the I(ACh) was as follows: apamin >> quinine approximately quinidine approximately d-tubocurarine > tetraethylammonium chloride > 4-aminopyridine approximately Ba2+ > Cs2+. It is proposed that the Ca2+-activated K+ channels of mammalian cochlear OHCs should be classified as small conductance Ca2+-activated K+ (SK) channels according to their pharmacological properties.
authors.affiliation: Department of Otolaryngology, Fukui Medical University School of Medicine, Japan. takehito@sabae.hosp.go.jp
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Kakehata
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: H
authors.initials: H
authors.lastname: Saito
authors.forename: N
authors.initials: N
authors.lastname: Akaike
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000109:Acetylcholine / Q000502:physiology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D018999:Charybdotoxin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D012604:Scorpion Venoms / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D018712:Analgesics, Non-Narcotic; D018733:Nicotinic Antagonists; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D001030:Apamin; D019789:Tetraethylammonium; C064719:iberiotoxin; D011803:Quinine; D015761:4-Aminopyridine; D011802:Quinidine; D000109:Acetylcholine; D014403:Tubocurarine