title: Species difference in the contribution of T-type calcium current to cardiac pacemaking as revealed by r(-)-efonidipine.
abstract: The contribution of the T-type Ca2+ current to cardiac pacemaking was examined in isolated right atrial tissue from the mouse, guinea pig, and rabbit using a specific blocker, R(-)-efonidipine. At 10(-6) M, R(-)-efonidipine produced negative chronotropy, which was prominent in the mouse and small but significant in the guinea pig. No effect was observed in the rabbit. Microelectrode recordings revealed that R(-)-efonidipine significantly prolongs the pacemaker (phase 4) depolarization of the sinoatrial-node action potential in the mouse and guinea pig. These results provide the first pharmacological evidence that the contribution of T-type Ca2+ current to cardiac pacemaking differs among experimental animal species.
authors.affiliation: Department of Pharmacology, Toho University Faculty of Pharmaceutical Sciences, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Tanaka
authors.forename: Chisa
authors.initials: C
authors.lastname: Komikado
authors.forename: Iyuki
authors.initials: I
authors.lastname: Namekata
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Mariko
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Tsuneoka
authors.forename: Koki
authors.initials: K
authors.lastname: Shigenobu
authors.forename: Akira
authors.initials: A
authors.lastname: Takahara
mesh_terms: D000200:Action Potentials; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020747:Calcium Channels, T-Type / Q000187:drug effects* / Q000378:metabolism; D004095:Dihydropyridines / Q000494:pharmacology*; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D051379:Mice; D008839:Microelectrodes; D009596:Nitrophenols / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D011817:Rabbits; D012849:Sinoatrial Node / Q000187:drug effects* / Q000378:metabolism; D013045:Species Specificity; D013997:Time Factors
chemical_list: D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D004095:Dihydropyridines; D009596:Nitrophenols; D009943:Organophosphorus Compounds; C066425:efonidipine