title: A ganglionic stimulant, 1,1-dimethyl-4-phenylpiperazinium, caused both cholinergic and adrenergic responses in the isolated mouse atrium.
abstract: An isolated atrial preparation of the mouse is useful for analyzing the actions of drugs on the myocardium, autonomic neurons and endocardial endothelium. The aim of the present study was to examine the functions of intrinsic neurons of the atrium using a ganglionic stimulant, 1,1-dimethyl-4-phenylpiperazinium (DMPP). DMPP (1-100 μM) caused a negative chronotropic action followed by a positive chronotropic action in spontaneously beating right atria and also caused biphasic inotropic actions consisting of initial inhibition followed by potentiation of electrical field stimulation (EFS)-induced contraction in the left atria. Inotropic actions in the left atria induced by DMPP were characterized using some autonomic drugs and M2 and/or M3 muscarinic receptor knockout (M2R-KO, M3R-KO and M2M3R-KO) mice. Atropine and hexamethonium decreased the initial negative inotropic actions of DMPP. In the atria from pertussis toxin-treated, M2R-KO and M2/M3R-KO mice, the negative inotropic actions were abolished. On the other hand, the following positive inotropic actions were decreased by hexamethonium, atropine and atenolol. In the atria from reserpine-treated mice, positive inotropic actions were also decreased. The positive inotropic action induced by DMPP was almost the same in M2R-KO mice but was reduced in both M3R-KO mice and M2/M3R-KO mice. In conclusion, DMPP caused biphasic inotropic/chronotropic actions in the mouse atrium through activation of intrinsic cholinergic and adrenergic neurons. M2 and M3 muscarinic receptors and β1-adrenoceptor are thought to be involved in these actions.
authors: Department of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
authors: Kenta
authors: K
authors: Ochi
authors: Hiroki
authors: H
authors: Teraoka
authors: Toshihiro
authors: T
authors: Unno
authors: Sei-Ichi
authors: S
authors: Komori
authors: Masahisa
authors: M
authors: Yamada
authors: Takio
authors: T
authors: Kitazawa
mesh_terms: D058671:Adrenergic beta-1 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology*; D004558:Electric Stimulation; D005260:Female; D005731:Ganglionic Stimulants / Q000494:pharmacology*; D006325:Heart Atria / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D010830:Physostigmine / Q000494:pharmacology; D043585:Receptor, Muscarinic M2 / Q000037:antagonists & inhibitors / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000037:antagonists & inhibitors / Q000502:physiology*; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D002800:Cholinesterase Inhibitors; D005731:Ganglionic Stimulants; D018727:Muscarinic Antagonists; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D018342:Receptors, Adrenergic, beta-1; D001262:Atenolol; D004246:Dimethylphenylpiperazinium Iodide; D001285:Atropine; D010830:Physostigmine