title: The role of Na+ channels in twitch generation during exposure of the frog rectus abdominis to Ca-free Ringer solution with Na2EDTA.
abstract: The aim of the study was to investigate whether Na+ channels play a role in the twitch component of the response of the isolated frog rectus abdominis to Ca(2+)-free Ringer solution with 0.2 mM Na2EDTA by using tetrodotoxin and some other well known drugs that exhibit a blocking action on Na+ channels. In the presence of 5 x 10(-7) M tetrodotoxin, the twitch component, measured isotonically, disappeared. Although 10(-7) M d-tubocurarine was found to be ineffective, a complete blockage of twitch amplitude was observed at 5 x 10(-6) M concentration of the drug. The inhibitory action of d-tubocurarine on twitch response was not antagonized by 10(-6) and 10(-5) M carbachol. Propranolol (10(-6) - 10(-5) M), lidocaine (2 x 10(-6) - 10(-5) M), quinine (10(-6) - 2 x 10(-5) M) and quinidine (10(-6) - 2 x 10(-5) M) inhibited maximal twitch amplitude in a concentration dependent manner. These findings strongly suggest that activation of tetrodotoxin sensitive Na+ channel may play a primary role at twitch generation during exposure of the frog rectus abdominis to Ca(2+)-free Ringer solution with Na2 EDTA.
authors.affiliation: Department of Pharmacology, Medical Faculty, Cukurova University, Adana, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Seçilmiş
authors.forename: S
authors.initials: S
authors.lastname: Atçi
authors.forename: N
authors.initials: N
authors.lastname: Yaktubay
authors.forename: Y
authors.initials: Y
authors.lastname: Karataş
authors.forename: C
authors.initials: C
authors.lastname: Göçmen
authors.forename: E
authors.initials: E
authors.lastname: Singirik
authors.forename: A
authors.initials: A
authors.lastname: Dikmen
authors.forename: F
authors.initials: F
authors.lastname: Baysal
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology*; D005260:Female; D007552:Isotonic Solutions / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D011894:Rana pipiens; D017568:Rectus Abdominis / Q000502:physiology*; D000077331:Ringer's Solution; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D007552:Isotonic Solutions; D015222:Sodium Channels; D013779:Tetrodotoxin; D000077331:Ringer's Solution; D004492:Edetic Acid; D002118:Calcium