We describe the discovery of the first selective, potent, and voltage-dependent inhibitor of the late current mediated by the cardiac sodium channel Na V1.5. The compound 3,4-dihydro- N-[(2 S)-3-[(2-methoxyphenyl)thio]-2-methylpropyl]-2 H-(3 R)-1,5-benzoxathiepin-3-amine, 2a (F 15845), was identified from a novel family of 3-amino-1,5-benzoxathiepine derivatives. The late sodium current inhibition and antiischemic effects of 2a were studied in various models in vitro and in vivo. In a rabbit model of ischemia-reperfusion, 2a exhibited more potent antiischemic effects than reference compounds KC 12291, ranolazine, and ivabradine. Thus, after a single administration, 2a almost abolished ST segment elevation in response to a transient coronary occlusion. Further, the antiischemic activity of 2a is maintained over a wide range of doses and is not associated with any hemodynamic changes, contrary to conventional antiischemic agents. The unique pharmacological profile of 2a opens new and promising opportunities for the treatment of ischemic heart diseases.

Background and purpose: Activation of the persistent sodium current in ischaemic myocardium results in calcium overload which is toxic for the cardiomyocyte. Thus, the activity of 3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5 benzoxathiepine bromhydrate (F 15845), a new selective persistent sodium current blocker, in protecting against the effects of cardiac ischaemia was examined, in both in vitro and in vivo models. Experimental approach: Electrophysiological studies using patch-clamp and conventional microlelectrode techniques, isolated perfused hearts and models of angina in anaesthetized animals were used to assess the protection afforded by F 15845 against ischaemia-induced changes. Key results: F 15845 reduced the persistent sodium current activated by veratridine (IC50 1.58 ¥ 10 -6 mol·L -1). F 15845 blocked voltage-gated human cardiac sodium channels in a novel, voltage-dependent manner, selectively affecting steady-state inactivation. F 15845 did not affect action potential shape and basal function of guinea pig isolated perfused hearts but did reduce ischaemia-induced diastolic contracture in this model (IC50 0.64 ¥ 10 -6 mol·L ) in an experimental angina model of demand ischaemia, again without haemodynamic effects, confirming a direct anti-anginal activity. Conclusions and implications: F 15845 is a selective, potent blocker of the persistent sodium current, generated by the human Nav1.5 channel isoforms, and prevents cardiac angina in animal models.

The clinical anti-anginal effectiveness of ranolazine is currently being evaluated. However, the mechanism of its anti-ischaemic action is still unclear. The aim of this work was to establish whether ranolazine exerts functional beta-adrenoceptor antagonist activity in the rat cardiovascular system. Radioligand binding studies were performed in rat hearts and guinea-pig lungs for beta1- and beta2-adrenoceptor affinity, respectively. Ranolazine had micromolar affinity for both beta,- and beta2-adrenoceptors (pKi5.8 and 6.3, respectively). Developed tension was measured in isolated rat left atria (electrically driven at 4 Hz) and cumulative concentration/response curves to (+/-)isoprenaline (0.01-1,000 nM) constructed. Ranolazine (0.32-10 microM) surmountably but weakly antagonised isoprenaline-induced positive inotropic responses, with an apparent pA2 of 5.85 (5.69-6.00) and a slope of -0.74 (-0.70 to -0.77). In bivagotomised, atropinised pithed rats, ranolazine per se evoked marked bradycardia at doses above 10 mg/kg i.v. (maximum variation at 80 mg/kg -125+/-15 bpm, n=6, P<0.001) by a mechanism apparently unrelated to blockade of beta1- or beta2-adrenoceptors. Cumulative incremental doses of (+/-)isoprenaline (0.63 ng/kg to 0.16 mg/kg i.v.) administered to pithed rats induced concomitant depressor and chronotropic responses. Animals received either vehicle (saline 0.9% i.v., n=12), atenolol (0.04-2.5 mg/kg i.v., n=6 per dose), ICI 118551 (0.01-0.63 mg/kg i.v., n=6 or 7 per dose), (+/-)propranolol (0.01-0.63 mg/kg i.v., n=6 per dose) or ranolazine (2.5-80 mg/kg i.v., n=6 or 7 per dose) 10 min prior to isoprenaline. Ranolazine dose-dependently and competitively antagonised isoprenaline-induced decreases in diastolic arterial pressure (DAP, dose ratio 12.2 with 80 mg/kg ranolazine) and increases in heart rate (HR, dose ratio 20.3 with 80 mg/kg ranolazine). Collectively, these results demonstrate that ranolazine behaves as a weak beta1- and beta2-adrenoceptor antagonist in the rat cardiovascular system.

Wound healing after angioplasty or stenting is associated with increased production of thrombin and the activation of protease-activated receptor 1 (PAR1). The aim of the present study was to examine the effects of a new selective PAR1 antagonist, 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)-penta-1,3-dienyl

Similtaneous measurements of arterial pressure and cardiac output (n= 8), mesenteric blood flow (n= 7) or hindquarters (n= 8) blood flow were performed during 1 h periods in conscious rats, before and after acute pharmacological blockade of the autonomic, renin‐angiotensin and vasopressin systems. In the latter condition (areflexic state), arterial pressure was maintained with a continuous infusion of noradrenaline. In the areflexic state, spontaneous fluctuations in arterial pressure were markedly exaggerated, especially depressor episodes. At the onset of these falls in arterial pressure, there was an abrupt and transient decrease in stroke volume and cardiac output. Systemic vasodilatation then developed while cardiac output returned to normal. Regional vasodilatations were also delayed from the onset of the falls in arterial pressure and were usually large enough to maintain blood flow. Both time and frequency domain analyses confirmed that changes in systemic and regional vascular conductances lagged by about 1 s behind arterial pressure changes. These results indicate that, in the absence of neurohumoral influences, autoregulatory‐like mechanisms become dominant in the control of systemic and regional circulations and contribute to exaggeration of the spontaneous short‐term variability of arterial pressure.

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.

1. Little is known about spontaneous slow rhythms in regional circulations. The present study was aimed at characterizing low-frequency (LF; 78-269 mHz) oscillations in the mesenteric and hindquarter circulations of conscious rats. 2. Mean arterial pressure (MAP) and indices (pulsed Doppler technique) of mesenteric (n = 25) and hindquarter (n = 23) blood flows were recorded in conscious, freely moving rats during 1 h periods. Fast Fourier transform analysis was applied to beat-to-beat data after resampling at 10 Hz of consecutive 205 s time series. 3. A major oscillation centred at 164 +/- 4 mHz was present in the mesenteric, but not in hindquarter, circulation. Consequently, LF power accounted for approximately 43% of the overall variability of mesenteric blood flow. Cross-spectral analysis performed between MAP and mesenteric blood flow indicated that fractional changes in flow were approximately two-fold of those in MAP, in pressure, at the peak frequency. 4. Acute blockade of the autonomic, renin-angiotensin and vasopressin systems combined with noradrenaline infusion (n = 7) reduced the frequency of the mesenteric blood flow oscillation (115 +/- 6 mHz) but did not change its contribution to overall flow variability (approximately 48%). A clear oscillation was still present after acute inhibition of nitric oxide (NO) synthesis with NG-nitro-L-arginine methyl ester (n = 8), but was virtually absent in chronically guanethidine-sympathectomized rats (n = 12). 5. In conclusion, the mesenteric blood flow of conscious rats exhibits a major slow oscillation that originates in the mesenteric vasculature and is not secondary to the activity of the major pressor systems or to the cyclic release of NO. Because of the strong attenuation of the oscillation in sympathectomized rats, we suggest that adrenergic vasoconstrictor tone plays a permissive role in its genesis.

The effects of donitriptan on systemic arterial-jugular venous oxygen saturation difference were evaluated in pentobarbitoneanesthetized pigs. Oxygen and carbon dioxide partial pressures in systemic arterial and jugular venous blood as well as hemoglobin oxygen saturation were determined by conventional blood gas analysis. Vehicle (40% polyethyleneglycol in saline, n ϭ 9) or donitriptan (0.01, 0.04, 0.16, 0.63, 2.5, 10, and 40 g/kg, n ϭ 7) were cumulatively infused over 15 min/dose. The involvement of 5-hydroxytryptamine 1B (5-HT 1B ) receptors was assessed in the presence of the 5-HT 1B/1D receptor antagonist, GR 127935. Donitriptan decreased markedly and dose dependently jugular venous oxygen saturation [ED 50 0.5 (0.3-1.1) g/kg], in parallel with increases in carotid vascular resistance [ED 50 0.9 (0.7-1.1) g/kg]. Since arterial oxygen saturation and partial pressure remained unchanged, donitriptan significantly increased arteriovenous oxygen saturation difference from 0.63 g/kg (maximal variation: 57 Ϯ 18%, P Ͻ 0.05 compared with vehicle). Unexpectedly, donitriptan from 2.5 g/kg induced marked and significant increases in carbon dioxide partial pressure (pVCO 2 ) in venous blood (maximal increase 18.8 Ϯ 5.7%; P Ͻ 0.05 compared with vehicle). Pretreatment with GR 127935 (0.63 mg/kg, n ϭ 5) abolished the fall in venous oxygen saturation and the increase in carotid vascular resistance and reduced the increases in pVCO 2 induced by donitriptan. The results demonstrate that donitriptan, via 5-HT 1B receptor activation, decreases the oxygen saturation of venous blood draining the head, concomitantly with cranial vasoconstriction. Since donitriptan also increased pVCO 2 , an effect upon cerebral oxygen consumption and metabolism is suggested in addition to cranial vasoconstriction, which may be relevant to its headache-relieving effects.Donitriptan is a unique high-efficacy agonist at 5-HT 1B/1D receptors; it is currently being evaluated for efficacy in the acute relief of migraine headache in phase II clinical trials (Dukat, 2001;John et al., 1999John et al., , 2000. One of the key pharmacological actions of donitriptan is 5-HT 1B receptor-medi- Tom et al., 2002). Before the advent of the triptans, the nonselective 5-HT 1B receptor agonist ergotamine (Villalón et al., 1999) was also shown to elicit selective carotid vasoconstriction confined to cephalic AVAs (Johnston and Saxena, 1978). Moreover, increases in AVOSD due to decreases in jugular venous oxygen saturation and oxygen partial pressure (pO 2 ) without affecting systemic arterial oxygen saturation or pO 2 were also observed in this study (Johnston and Saxena, 1978). However, it is presently unknown whether the recently described triptan 5-HT 1B/1D receptor agonistinduced increases in AVOSD are due to changes in systemic arterial or jugular venous oxygen saturation, or both.The aim of the present investigation was therefore to eluArticle, publication date, and citation information can be found at http://jpet.aspetjournals.org. DOI: 10.1124/jpet.102...