Interactions of a new beta-blocker, celiprolol, with the calcium antagonists, diltiazem and nifedipine, on atrioventricular conduction

Modulation of beta-adrenergic receptor subtype activities in perioperative medicine: mechanisms and sites of action

This review focuses on the mechanisms and sites of action underlying beta-adrenergic antagonism in perioperative medicine. A large body of knowledge has recently emerged from basic and clinical research concerning the mechanisms of the life-saving effects of beta-adrenergic antagonists (beta-AAs) in high-risk cardiac patients. This article re-emphasizes the mechanisms underlying beta-adrenergic antagonism and also illuminates novel rationales behind the use of perioperative beta-AAs from a biological point of view. Particularly, it delineates new concepts of beta-adrenergic signal transduction emerging from transgenic animal models. The role of the different characteristics of various beta-AAs is discussed, and evidence will be presented for the selection of one specific agent over another on the basis of individual drug profiles in defined clinical situations. The salutary effects of beta-AAs on the cardiovascular system will be described at the cellular and molecular levels. Beta-AAs exhibit many effects beyond a reduction in heart rate, which are less known by perioperative physicians but equally desirable in the perioperative care of high-risk cardiac patients. These include effects on core components of an anaesthetic regimen, such as analgesia, hypnosis, and memory function. Despite overwhelming evidence of benefit, beta-AAs are currently under-utilized in the perioperative period because of concerns of potential adverse effects and toxicity. The effects of acute administration of beta-AAs on cardiac function in the compromised patient and strategies to counteract potential adverse effects will be discussed in detail. This may help to overcome barriers to the initiation of perioperative treatment with beta-AAs in a larger number of high-risk cardiac patients undergoing surgery.

Comparison of anti-M2-muscarinic effect of AF-DX 116 on atrioventricular nodal conduction with those of pirenzepine and atropine as antibradyarrhythmic drugs

Selectivity of antimuscarinic actions of AF-DX 116 (AF-DX) on the atrioventricular (AV) nodal conduction was compared with those of pirenzepine and atropine by using the canine isolated, blood-perfused AV node preparation and the open-chest in situ dog heart. In the isolated AV node preparation, dose-response curves for negative dromotropic effects (prolongation of Atrio-His interval) of carbachol (CCh) injected into the posterior septal artery were shifted to the right in parallel by AF-DX, pirenzepine, and atropine with apparent pA2-values of 13, 27.5, and 0.45 microg, respectively, and slopes of the modified Schild plot of nearly unity. Meanwhile, dose-response curves for coronary vasodilator effects of CCh were shifted to the right by AF-DX, pirenzepine, and atropine with the apparent pA2 values of 68, 12.5, and 0.55 microg, respectively, but the slopes were far from unity. In the in situ open-chest heart, dose-response curves for negative dromotropic effects (prolongation of AV conduction time) of CCh given intravenously were shifted to the right in parallel by AF-DX, pirenzepine, and atropine with apparent pA2 values of 36, 32, and 1.25 microg/kg, respectively, and the slope of nearly unity, whereas dose-response curves for hypotensive effects of CCh were shifted to the right by AF-DX, pirenzepine, and atropine with apparent pA2 values of 105, 15, and 0.65 microg/kg, respectively, but the slopes of AF-DX and pirenzepine were far from unity. In addition, prolongations of AV conduction time by electrical stimulation of the left vagus nerve in the in situ heart were suppressed by AF-DX, pirenzepine, and atropine with the ID50, dose for 50% suppression, of 40, 35, and 1.9 microg/kg, respectively. These results suggest that (a) the potency of antimuscarinic actions of AF-DX on the CCh-induced negative dromotropic effects was almost equal to that of pirenzepine, and approximately 30 times less potent than atropine; (b) the M2-subtype selectivity of AF-DX was considerably higher in comparison with pirenzepine and atropine; and (c) the muscarinic receptor subtype on the canine AV node is entirely of the M2-type, but only sparsely developed in the coronary vascular beds.

Time course of a new ultrashort-acting beta-adrenoceptor-blocking drug, ONO-1101: comparison with those of esmolol and propranolol by using the canine isolated, blood-perfused heart preparations

Time courses of beta-adrenoceptor-blocking actions of ONO-1101, a new cardioselective beta-blocker, were compared with those of esmolol and propranolol by using the isolated, blood-perfused sinoatrial node (SAN) and papillary muscle (PM) preparations of dogs. ONO-1101 per se given intraarterially (i.a.) in each nutrient artery did not affect basal sinoatrial rates (SARs; 99 +/- 2 beats/min, n = 7) in the SAN and developed tension (DT; 3.2 +/- 0.7 g, n = 7) of the PM preparations. Norepinephrine (NE) injected i.a. into the each artery induced increases in SAR (42 +/- 6 beats/min at 0.051 +/- 0.014 microg) and PMDT (2.9 +/- 0.4 g at 0.048 +/- 0.011 microg). The i.a. injections of NE were repeated every 3 min after i.v. bolus injections of ONO- 1101 into the support dog. NE-induced increases in SAR and PMDT were maximally inhibited 3 to 6 min after the i.v. injections of ONO-1101. Maximal percentage inhibitions by ONO-1101 of NE-induced increases in SAR were 54 +/- 6, 78 +/- 3, and 96 +/- 2% at 0.01, 0.1, and 1 mg/kg of the drug, respectively. Similarly, maximal percentage inhibitions by ONO-1101 of NE-induced increases in PMDT were 50 +/- 12, 93 +/- 2, and 100% +/- 0, respectively. The inhibition was quickly recovered; times required for 50% recovery (RT1/2) were 12 +/- 3. 17 +/- 3, and 32 +/- 10 min in the SAN preparation, and 13 +/- 3, 16 +/- 2, and 39 +/- 11 min in the PM preparations, after i.v. injections of 0.01, 0.1, and 1 mg/kg of ONO-1101, respectively. In comparison, maximal percentage inhibitions by esmolol of NE-induced increases in SAR were 45 +/- 5, 79 +/- 6, and 96 +/- 2%, and those in PMDT were 34 +/- 4, 75 +/- 5, and 97 +/- 1%, whereas the RT1/2 values were 11 +/- 2, 15 +/- 4, and 40 +/- 12 min in the SAN preparation, and 10 +/- 2, 16 +/- 7, and 27 +/- 6 min in the PM preparations, after i.v. injections of 0.01, 0.1, and 1 mg/kg of esmolol, respectively. In contrast, the maximal percentage inhibitions by an i.v. bolus injection of 0.1 mg/kg of propranolol of NE-induced increases in SAR and PMDT were 77 +/- 18% and 87 +/- 13% (n = 4). respectively. The maximal inhibitions were obtained 6-15 min after injections of propranolol and then slowly recovered only by 21% in the SAN and 8% in the PM preparations, even after 60 min. These results clearly demonstrate that ONO-1101 is an ultrashort-acting beta-blocker, but the recovery time is dose dependent, and that the beta-blocking action of ONO-1101 is almost similar to or slightly more potent (or both) than esmolol.