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We investigated blocking effects of pirenzepine, AF-DX 116 and atropine on the negative chronotropic and dromotropic responses to stimulation of the intracardiac vagus nerves in the anesthetized, open-chest dogs. Stimulation of the intracardiac vagus nerves to the sinoatrial nodal region (stimulation of the intracardiac parasympathetic nerves to the(More)
1. Vasoconstrictions induced by transmural electrical field stimulation were frequency-dependent from 2 to 32 Hz in the rabbit isolated splenic artery. All contractions were abolished in the presence of tetrodotoxin 1 microM or guanethidine 100 microM. Stimulation at a frequency of more than 32 Hz induced both neurogenic and myogenic responses. 2. Prazosin(More)
1. The effects of omega-conotoxin GVIA (omega-CgTX) and tetrodotoxin (TTX) on vasoconstrictions induced by acetylcholine (ACh) and nicotine were investigated and compared with those induced by periarterial electrical stimulation in the isolated and perfused canine splenic arteries. 2. ACh and nicotine at doses of 0.01 to 1 mumol constricted the splenic(More)
Neuropeptide Y (NPY) inhibits the release of noradrenaline (NA) or acetylcholine (ACh) from nerve terminals in the heart. Thus, we differentiated the blocking effects of NPY on the negative and positive (atrial chronotropic and inotropic) responses to simultaneous stimulation of the intracardiac parasympathetic and sympathetic nerves in isolated,(More)
The blocking effects of glibenclamide on the chronotropic and inotropic responses to K+ channel openers pinacidil (ATP-sensitive) and acetylcholine (ACh) or adenosine (receptor-operated) were investigated in the isolated, blood-perfused canine atrium or ventricle. Glibenclamide (0.1-3 mumol) induced no significant cardiac effects. Cumulative administration(More)
Positive chrono- and inotropic responses to denopamine (TA-064, (-)-(R)-1-(p-hydroxyphenyl)-2-[(3,4-dimethoxyphenethyl)amino]ethanol), a new and orally active cardiotonic agent, were investigated in the canine isolated right atrial or left ventricular preparation which was cross-circulated with blood from another support dog. Denopamine dose-dependently(More)
We investigated the nonuniform effects of autonomic nerve stimulation of the effective refractory period (ERP) of the right atrium in the anesthetized dog. Stimulation of the discrete intracardiac sympathetic nerves to the sinoatrial (SA) nodal region uniformly shortened ERPs at three sites in the right atrium after administration of atropine. Right ansa(More)
We investigated blocking effects of the selective beta 1-adrenoceptor blocker atenolol (0.1-100 micrograms/kg, i.v.), the selective beta 2-adrenoceptor blocker ICI 118,551 (1-1000 micrograms/kg, i.v.) and the combination of the two drugs on positive chronotropic and dromotropic responses to norepinephrine (NE) released by stimulation of the sympathetic(More)
AIM Doxazosin is a racemic mixture of (-)doxazosin and (+)doxazosin that is currently used as an add-on therapy for hypertension. In this study we investigated the contribution of each enantiomer to the hypotensive action of long-term administration of (±)doxazosin in conscious rats. METHODS Blood pressure of conscious SD rats was measured using a volume(More)
AIM To study the effect of blocking adenosine A1 receptors on learning and memory and the relation with cholinergic and aminoacidergic nerve. METHODS Using step through test, spectrophotometry and HPLC method, the effect of selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 0.3, 0.15, 0.075, 0.03, 0.015 microgram, icv)(More)