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Metabolic syndrome (MetS) is a global health and economic burden. Finding a suitable pharmacological approach for managing this syndrome is crucial. We explored the therapeutic potential of mirabegron (MIR), a βThirty Watanabe heritable hyperlipidemic rabbits (WHHL) were divided into 3 groups: control, high-fructose high-fat diet (HFFD) and HFFD + MIR that received a chow diet, HFFD and HFFD along with MIR treatment, respectively. The protocol lasted for 12 weeks, during which weight and abdominal circumference were monitored; plasma fasting levels of lipids, glucose and insulin were measured and an intravenous glucose tolerance test (IVGTT) was performed. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Cardiac function was assessed using in-vivo and ex-vivo approaches. Vascular reactivity was estimated via isolated carotid arteries method. Aortic atherosclerosis was evaluated using histological and immuno-histochemical techniques.In contrast to the HFFD group, MIR-treated rabbits showed fasting insulin, HOMA-IR and TG levels stabilization and exhibited improved cardiac inotropy and lusitropy, while on the other hand, displayed aggravated atheroma plaque development.Long-term treatment with MIR prevented the increase in TG levels and the establishment of IR and enhanced the cardiac function of a rabbit animal model of MetS with combined dyslipidemia and IR.

Dengue fever is a common arbovirus disease, which has been spread to the entire tropical world. At present, effective drugs for the treatment of dengue fever have not yet appeared, and the dengue vaccines studied in various countries have also experienced severe adverse reactions. Thus it is urgent to find new chemicals against dengue virus. Now we found Sirtuins (SIRTs) were increased during dengue virus infection and tenovin-1, a SIRT1/2 inhibitor, showed an impressive antiviral ability in vitro. In BHK-21 cells, tenovin-1 inhibited the replication of DENV2 with an EC50 at 3.41 ± 1.10 μM, also inhibited other three types of dengue viruses with EC50 at 0.97 ± 1.11 μM, 1.81 ± 1.08 μM, 3.81 ± 1.34 μM respectively. Moreover, the cytopathic effect-induced DENV2 was largely improved by tenovin-1 treatment and the release of progeny viruses was inhibited by tenovin-1 treatment. At the same time, the viral protein level and mRNA level were decreased with tenovin-1 treatment after dengue virus infection. From the drug-addition assay, the tenovin-1 played its antiviral after viral infection, which indicated tenovin-1 was not a microbicide. Apart from its antiviral effect, tenovin-1 inhibited the inflammatory response caused by DENV2, reducing the release of inflammatory factors during viral infection. The antiviral effect of tenovin-1 was abrogated with SIRT agonist or SIRT2 knockdown treatment, which indicated the effect of tenovin-1 was on-target. In conclusion, tenovin-1 was proved to be a promising compound against flavivirus infection through SIRT2, which should be pay more attention for further study.

Transient receptor potential melastatin 8 (TRPM8) channels may contribute to the pathophysiological bladder afferent hyperactivity, thus a TRPM8 antagonist would be a promising therapeutic target for the bladder hypersensitive disorders including urinary urgency in overactive bladder (OAB). We aimed to investigate a pharmacological effect of KPR-5714, a novel selective TRPM8 antagonist, on TRPM8 channels, M

Made available in DSpace on 2019-10-06T15:47:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-05 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Mirabegron is the first β3-adrenoceptor agonist approved on the market and may offer beneficial pharmacological action in patients with overactive bladder and erectile dysfunction. Here, we further investigate the mechanisms by which mirabegron induces rat corpus cavernosum (CC) relaxation. Adult male Wistar rats were used. The CC were isolated for in vitro functional assays and β-adrenoceptors subtypes mRNA expression evaluation. Animals were treated orally with mirabegron (30 mg/kg, 3 h), tadalafil (10 mg/kg, 3 h) or both for intracavernous pressure (ICP). Intracellular levels of cAMP and cGMP were also determined. The β1-, β2- and β3-adrenoceptors subtypes were expressed in rat CC. Mirabegron produced concentration-dependent CC relaxations that were unaffected by the β1-, β2- or β3-adrenoceptor antagonists atenolol (1 μM), ICI-118,551 (1 μM) and L748,337 (10 μM), respectively. Mirabegron-induced relaxations were not affected by the phosphodiesterase type 4 inhibitor, rolipram, or the adenylyl cyclase selective inhibitor, SQ 22,536. Potassium channel- or calcium influx-blockade are not involved in mirabegron-induced relaxations. In contrast, mirabegron produced rightward shifts in the contractile response induced by the α1-adrenoceptor agonist, phenylephrine. Finally, cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly increased in rats treated with mirabegron in a similar degree of tadalafil-treated rat, without promoting a significant cAMP or cGMP accumulation. Together, our results demonstrate that mirabegron induced CC relaxation through α1-adrenoceptor blockade. Care should be taken to translate the effect of mirabegron into the clinic, especially when using rat as an animal model of erectile dysfunction. Department of Pharmacology Faculty of Medical Sciences University of Campinas (UNICAMP) Department of Pharmacology Institute of Biosciences São Paulo State University (UNESP) Department of Pharmacology Institute of Biosciences São Paulo State University (UNESP) FAPESP: 2013/13907–4 FAPESP: 2017/15175–1 FAPESP: 2018/09765–3

Sympathetic fibres maintain some forms of neuropathic pain, but the underlying mechanisms are poorly understood. Therefore, this study investigated the possible involvement of transient receptor potential ankyrin 1 (TRPA1) and the role of the sympathetic nervous system (involved in sympathetically maintained neuropathic pain) in a model of neuropathic pain induced by sciatic nerve chronic constriction injury (CCI) in mice. Systemic injection of the selective TRPA1 antagonist HC-030031 reversed the mechanical and cold allodynia that was induced by sciatic nerve chronic constriction injury (CCI). Nerve injury also sensitised mice to nociception, which was induced by the intraplantar injection of a low dose of the TRPA1 agonist allyl isothiocyanate without changing TRPA1 immunoreactivity in the injected paw. Furthermore, chemical sympathectomy produced by guanethidine largely prevented CCI-induced mechanical and cold allodynia. CCI also induced a norepinephrine-triggered nociception that was inhibited by an α-adrenoceptor antagonist, norepinephrine transporter block and monoamine oxidase inhibition. Finally, the peripheral injection of HC-030031 also largely reduced CCI-induced norepinephrine nociception and mechanical or cold allodynia. Taken together, the present findings reveal a critical role of TRPA1 in mechanical and cold hypersensitivity and norepinephrine hypersensitivity following nerve injury. Finally, our results suggest that TRPA1 antagonism may be useful to treat patients who present sympathetically maintained neuropathic pain.

Mirabegron is a β

β(3)-Adrenoceptors are major players in detrusor relaxation and have been suggested as a new putative target for the treatment of overactive bladder syndrome. We determined the effects of mirabegron (YM178), a novel β(3)-adrenoceptor agonist, on carbachol-induced tone in isolated human detrusor preparations from patients with bladder outflow obstruction (BOO) with and without detrusor overactivity (DO), and from patients with normal bladder function. We compared the effects to those of isoprenaline, a non-selective β-adrenoceptor agonist. Detrusor specimens were obtained from patients with benign prostatic hyperplasia undergoing cystoscopy and from patients undergoing radical prostatectomy/cystectomy (in total 33 donors). Detrusor contractility was evaluated by organ bath studies and strips were incubated with carbachol (1μM) to induce and enhance tension. Both mirabegron and isoprenaline reduced carbachol-induced tone in tissues from all groups. Isoprenaline decreased tension with higher potency than mirabegron in normal, BOO and BOO+DO detrusor strips with pIC(50) values of 7.49 ± 0.16 vs. 6.23 ± 0.26 (P=0.0002), 6.89 ± 0.34 vs. 6.04 ± 0.31 (P=0.01), and 6.57 ± 0.20 vs. 5.41 ± 0.08 (P0.05), respectively. Mirabegron and isoprenaline reduced carbachol-induced tone in both normal bladders and obstructed bladder with and without DO. Isoprenaline had higher potency than mirabegron, but the efficacy of mirabegron effect was the same as that of isoprenaline.

The aim of this study was to investigate the cellular electrophysiological effects of ranolazine on action potential characteristics. The experiments were carried out in dog and human cardiac preparations using the conventional microelectrode technique. In dog Purkinje fibres ranolazine produced a concentration- and frequency-dependent depression of the maximum rate of depolarization (V(max)) while action potential duration (APD) was shortened. In dog and human right ventricular papillary muscle ranolazine exerted no significant effect on APD, while it produced, like mexiletine, use-dependent depression of V(max) with relatively fast onset and offset kinetics. In dog midmyocardial preparations the drug did not exert statistically significant effect on repolarization at 10 μM, although a tendency toward prolongation was observed at 20 μM. A moderate lengthening of APD(90) by ranolazine was noticed in canine atrial preparations obtained from dogs in sinus rhythm and in tachypacing induced remodelled preparations. Use-dependent depression of V(max) was more pronounced in atria from dogs in sinus rhythm than those in remodelled atria or in the ventricle. These findings indicate that ranolazine, in addition to its known late sodium current blocking effect, also depresses peak I(Na) with class I/B antiarrhythmic characteristics. Although peak I(Na) inhibition by ranolazine is stronger in the atria, it is also substantial (at fast stimulation frequencies) in ventricular preparations. Ranolazine also decreased the dispersion of ventricular repolarization (the difference in APD(90) values between Purkinje fibres and papillary muscles), which can contribute to the antiarrhythmic property of the drug.

Recent evidence suggests that the forkhead transcription factor Foxo1 plays an important role in the regulation of glucose and triglyceride metabolism at the gene transcription level for glucose-6 phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), and apolipoprotein C-III (apoC-III). Here, we report on the pharmacological effects of the novel Foxo1 inhibitor AS1708727, which we identified by compound screening. Chronic treatment of diabetic db/db mice with AS1708727 for four days significantly reduced blood glucose and triglyceride levels with decrease of gene expression levels of hepatic G6Pase, PEPCK, and apoC-III. No reports have yet examined the influence of Foxo1 inhibitors on these pharmacological effects. In this study, we newly identified a Foxo1 inhibitor compound capable of exerting both an anti-hypertriglyceridemic and anti-hyperglycemic effect. These effects were dependent on maintaining a stable blood concentration of AS1708727 and achieving a high rate of compound transition to the liver. We also investigated the action mechanism of AS1708727 on gluconeogenesis in vitro and in vivo. The compound inhibited gene expression of key gluconeogenic molecules and suppressed gluconeogenesis in Fao hepatocyte cells in vitro. Further, in the pyruvate challenge study using db/db mice in vivo, AS1708727 suppressed increases in blood glucose level by inhibiting gluconeogenic gene expression. These results indicate that the novel Foxo1 inhibitor AS1708727 may exert anti-diabetic and anti-hypertriglyceridemic effects by improving blood glucose and triglyceride metabolism at the gene expression level, and may represent a new class of drugs useful for treating type 2 diabetes mellitus and hypertriglyceridemaia.

We have previously demonstrated that menthol reduces murine gastric tone in part through a neural mechanism, involving adrenergic pathways and reduction of ongoing release of acetylcholine from enteric nerves. In the present study we aimed to verify whether the gastric relaxation to menthol may be triggered by interaction with neural receptors or ionic channels proteins, such as transient receptor potential (TRP)-melastatin8 (TRPM8), TRP-ankyrin 1 (TRPA1), 5-hydroxytriptamine 3 (5-HT3) receptor or cholinergic nicotinic receptors. Spontaneous mechanical activity was detected in vitro as changes in intraluminal pressure from isolated mouse stomach. Menthol (0.3-30 mM) induced gastric relaxation which was not affected by 5-benzyloxytryptamine, a TRPM8 receptor antagonist, HC030031, a TRPA1 channel blocker. In addition, allylisothiocyanate, a TRPA1 agonist, but not (2S,5R)-2-Isopropyl-N-(4-methoxyphenyl)-5-methylcyclohexanecarboximide, a selective TRPM8 agonist, induced gastric relaxation. Genic expression of TRPA1, but not of TRPM8, was revealed in mouse stomach. Indeed, menthol-induced gastric relaxation was significantly reduced by hexamethonium, cholinergic nicotinic receptor antagonist. Menthol, at concentrations that failed to affect gastric tone, reduced the contraction induced by dimethylphenylpiperazinium, nicotinic receptor agonist. The joint application of hexamethonium and atropine, muscarinc receptor antagonist, or hexamethonium and phentholamine, α-adrenergic receptor antagonist, did not produce any additive reduction of the relaxant response to menthol. Lastly, ondansetron, a 5-HT3 receptor antagonist, was ineffective. In conclusion, our study suggests that nicotinic receptors, but not TRP and 5-HT3 receptors, are molecular targets for menthol inducing murine gastric relaxation, ultimately due to the reduction of acetylcholine release from enteric nerves.

Bladder overactivity (OAB) is a multifactorial bladder disorder that requires therapeutics superior to the current pharmacological treatment with muscarinic antagonists. β3-adrenoceptor (β3-ADR) agonists represent a novel promising approach that differently addresses the parasympathetic pathway, but the clinical efficacy of these drugs has not been fully elucidated to date. Therefore, we aimed to study the pharmacological mechanisms activated by β3-ADR agonists at muscular and neural sites in the isolated human bladder. Detrusor smooth muscle strips obtained from male patients undergoing total cystectomy were labelled with tritiated choline and stimulated with electrical field stimulation (EFS). EFS produced smooth muscle contraction and simultaneous acetylcholine ([(3)H]-ACh) release, which mostly reflects the neural origin of acetylcholine. Isoprenaline (INA), BRL37344 and mirabegron inhibited the EFS-evoked contraction and [(3)H]-ACh release in a concentration-dependent manner, yielding concentration-response curves (CRCs) that were shifted to the right by the selective β3-ADR antagonists L-748,337 and SR59230A. Based on the agonist potency estimates (pEC50) and apparent affinities (pKb) of antagonists evaluated from the CRCs of agonists, our data confirm the occurrence of β3-ADRs at muscle sites. Moreover, our data are consistent with the presence of inhibitory β3-ADRs that are functionally expressed at the neural site. Taken together, these findings elucidate the mechanisms activated by β3-ADR agonists because neural β3-ADRs participate in the inhibition of detrusor motor drive by reducing the amount of acetylcholine involved in the cholinergic pathway.

Ranolazine reduces cellular acetyl-CoA content via inhibition of fatty acid beta-oxidation and activates pyruvate dehydrogenase. This metabolic switch increases ATP production per mole of oxygen consumed, reduces the rise in lactic acid and acidosis, and maintains myocardial function under conditions of reduced myocardial oxygen delivery. It is still unclear whether ranolazine causes a reduction of (i) infarct size and (ii) cardiac troponin T release, in a male Wistar rat model of left anterior descending coronary artery occlusion (25 min) and reperfusion (2 h). Rats were subjected to saline infusion (n=12) or ranolazine (bolus injection: 10 mg/kg plus infusion: 9.6 mg/kg/h, n=12), 30 min prior to left anterior descending coronary artery occlusion-reperfusion, respectively. Ranolazine caused a significant reduction in myocardial infarct size of approximately 33% compared to saline control (P

The aim of the present study is to investigate the effects of TRPV1 and TRPA1 receptor antagonists and their synergism on the visceromotor responses during experimental colitis in rats. Colitis was induced in rats by a TNBS/ethanol enema at day 0 and was assessed at day 3 using endoscopy, histology and a myeloperoxidase assay. The visceromotor response to colorectal distension (1080 mmHg) was evaluated in conscious rats before (control condition) and 3 days after 2,4,6-trinitrobenzene sulfonic acid (TNBS) administration (colitis condition). At day 3, visceromotor responses were assessed before and after treatment with a TRPV1 (BCTC) or TRPA1 (TCS-5861528) receptor antagonist either alone or in combination and either after intraperitoneal or intrathecal administration. Endoscopy, microscopy and myeloperoxidase activity indicated severe colonic tissue damage 3 days after TNBS administration. Colorectal distension-evoked visceromotor responses demonstrated a 2.9-fold increase during acute colitis (day 3) compared to control conditions. Intraperitoneal and intrathecal administration of BCTC or TCS-5861528 partially reversed the colitis-induced increase in visceromotor responses compared to control conditions (P

Ranolazine is mainly used to treat patients with chronic stable angina in clinical practice. However, ranolazine does not lower significantly systemic blood pressure. The direct effect of ranolazine on vascular tone remains unknown. In the present study, we investigated the vascular effects and mechanisms of action of ranolazine in isolated rat intrarenal arteries. Rings of intrarenal arteries were mounted in a small vessel myography using two stainless steel wires for the measurement of isometric tension. L-type Ca²⁺ currents were recorded in isolated single renal arterial smooth muscle cells using patch clamp techniques in whole-cell mode. Ranolazine induced concentration-dependent relaxations in rings contracted with phenylephrine, but ranolazine failed to cause any relaxation in rings pre-contracted by U46619, 5-HT or endothelin-1. Ranolazine also induced relaxations in norepinephrine pre-contracted rings. Yohimbine failed to induce relaxation in rings pre-contracted by norepinephrine. Propranolol did not affect ranolazine-induced relaxation but the relaxant effect of ranolazine was much less than that of prazosin. Ranolazine-induced relaxations were slight but significantly attenuated by endothelial denudation. Partial inhibition was observed in endothelium-intact arteries exposed to a combination of iberiotoxin and apamin. Ranolazine at higher concentration (>30 μM) inhibited Ca²⁺-induced contraction in a noncompetitive manner. Ranolazine reduced L-type Ca²⁺ currents at potentials between -30 and 50 mV in isolated renal artery myocytes. Therefore it can be said that ranolazine has significant α₁-adrenergic receptor and weak calcium channel antagonistic effects in rat intrarenal arteries.

The anticonvulsive properties of a new compound: F1933 (Dulozafone) were investigated in the amygdala kindling model and compared with those of diazepam. Both of drugs protected fully kindled rats against generalized siezures but failed to suppress partial ictal events (amygdala afterdischarges and limbic seizures). The anticonvulsive action of F1933, administered at the ED 100 , was nearly reversed by the specific antagonist of benzodiazepines receptors: R015-1788 (Flumazenil), suggesting that the effect of F1933 is mediated by this receptor. These results also emphasize the usefulness of kindling to test antiepileptic drugs and to confirm their supposed profile of action.

Effects of ranolazine on isosorbide dinitrate- and on sildenafil-induced changes in mean arterial pressure and heart rate were assessed in conscious dogs. Dogs (n = 7) were chronically instrumented for measurements of mean arterial pressure and heart rate. Bolus intravenous injections of either isosorbide dinitrate (0.2 mg/kg) or sildenafil (0.5 mg/kg) caused biphasic changes in mean arterial pressure and heart rate: a transient (approximately 20 s) decrease in mean arterial pressure and an increase in heart rate, followed by prolonged (10-15 min) decreases in mean arterial pressure by 11 +/- 1.6 and 11 +/- 2.2 mm Hg, respectively. Infusion of ranolazine alone (plasma concentrations = 4 or 8 microM) for 10 min did not significantly affect mean arterial pressure and heart rate. The transient hypotension and tachycardia caused by isosorbide dinitrate were not altered by ranolazine. The sildenafil-induced transient tachycardia (Delta change: 114 +/- 10 beats/min) was significantly (P < 0.05) blunted by either 4 (Delta change: 71 +/- 8 beats/min) or 8 (Delta change: 66 +/- 9 beats/min) microM ranolazine. However, the sildenafil-induced transient decrease in mean arterial pressure was not altered by ranolazine. During ranolazine infusion (4-5 or 8-10 microM), isosorbide dinitrate and sildenafil caused prolonged decreases in mean arterial pressure. These results indicate that except for a blunting of the transient tachycardia caused by sildenafil, ranolazine at concentrations up to 10 microM does not alter changes in mean arterial pressure and heart rate induced by either isosorbide dinitrate or sildenafil in conscious dogs.

Increased polyol pathway flux has been linked to nerve complications in diabetic rats, which are attenuated by aldose reductase inhibitors, defective nitric oxide-mediated vasodilation being a particular target. Diabetes also elevates the endothelial angiotensin system, increasing vasa nervorum vasoconstriction. The aim was to assess whether promotion of vasodilation by treatment with the aldose reductase inhibitor, ZD5522 (3',5'-dimethyl-4'-nitromethylsulphonyl-2-(2-tolyl)acetanilide), coupled with reduced vasoconstriction using the angiotensin-converting enzyme inhibitor, lisinopril, interacted positively to improve neurovascular function. After 8 weeks of streptozotocin-induced diabetes, sciatic nerve blood flow and motor conduction velocity were 51% and 21% reduced, respectively. Two weeks of lisinopril treatment dose-dependently corrected the conduction deficit (ED(50) approximately 0.9 mg kg(-1)). Low-dose lisinopril (0.3 mg kg(-1)) or ZD5522 (0.25 mg kg(-1)) had modest corrective (10-20%) effects on nerve conduction and perfusion. However, when combined, blood flow and conduction velocity reached the nondiabetic range. The ZD5522 dose used gave a approximately 45% nerve sorbitol reduction but had no significant effect on fructose content; lisinopril co-treatment did not alter ZD5522 action on polyols. Thus, there was a marked neurovascular synergistic interaction between angiotensin-converting enzyme and aldose reductase inhibition in diabetic rats. This points to a potential therapeutic benefit, which requires evaluation in clinical trials.

The effect of cyclosporin A was investigated on Torpedo synaptosomes. Cyclosporin A inhibits KCl-evoked acetylcholine release (up to 50% at 1 mu M) and was inactive on acetylcholine release induced by a Ca2+ ionophore, A23187. Interestingly, when the synaptosomes were pretreated with cyclosporin A, this immunosuppressor did abolish the modulation of A23187-induced acetylcholine release produced by two other drugs, cetiedil (alpha-cyclohexyl-3-thienyl acetic acid 2-(hexahydro-1H-azepin-1-yl) ethyl ester, citrate salt) and MR16728 (N-(N'-hexamethylene imino)-propyl-phenyl-cyclohexyl-methyl acetamide, chlorhydrate), which were previously shown to be inhibitory and stimulatory, respectively. Moreover, cyclosporin A and MR16728 are competitive inhibitors of [3H]cetiedil binding to purified synaptosomal presynaptic membranes (dissociation constant of 181.9 nM). These results suggest that presynaptic proteins involved in acetylcholine release (directly or indirectly through cyclophilin) are potential targets of cyclosporin A in Torpedo synaptosomes.

MR16728, a cetiedil analogue, enhanced acetylcholine (ACh) release (up to 145% of control) from Torpedo synaptosomes when the release was triggered by a Ca2+ ionophore, A23187 or ionomycin, in the presence of 4 mM Ca2+ in the release medium, but inhibited ACh release induced by KCl depolarization of the presynaptic membrane. MR16728 also inhibited Ca2+-ATPase activity measured in purified synaptosomal presynaptic membranes. We studied the stimulation by MR16728 as a function of its concentration; the half-maximal effect was reached at the concentration of 13.5 μM. Moreover the stimulation was more pronounced (up to 300%) when a low concentration of Ca2+ (in the 10-micromolar range) was added to the medium. The enhancement of ACh release was also observed in proteoliposomes having incorporated mediatophore, a presynaptic membrane protein, able to release ACh in a Ca2+-dependent manner. Thus, mediatophore is a potential presynaptic target for MR16728.

The potency of several compounds in inhibiting the autmatically induced by epinephrine in the rat ventricular strip has been evaluated. A correlation with high statistical significancee has been found between pharmacological activity and molecular volume (Mullins' hypothesis) or solubility (Ferguson's rule). These observations have been taken as evidence that the physical properties of the compounds studied are important in determining their potency as inhibitors of ventricular automaticity. Acetylcholine showed high specificity in inhibiting the epinephrine-induced authorhythmicity. It is concluded that this cardiac action of epinephrine may be inhibited not only by antagonists of beta-receptors, but also by a specific action of acetylcholine and by the nonspecific action of various compounds, for which the physical properties of the molecules assume a prominent importance.

The effects of propranolol, AY 21,011 and quinterenol on the responses of spontaneously beating right atrium and electrically driven left atrium to isoproterenol have been determined. The dissociation constants ( K B values) of these antagonists were the same for antagonizing the inotropic and chronotropic effects of isoproterenol. These results give further support to the hypothesis that the inotropic and chronotropic responses to isoproterenol are mediated via the same receptors.

The nature of brochial beta-receptors has been investigated in anaesthetized dogs by means of a comparative study of practolol- and propranolol-isoprenaline antagonisms on airway resistance, heart rate and diastolic blood pressure. While propranolol antagonized competitively isoprenaline effects on the three parameters, practolol was a competitive antagonist of isoprenaline only on heart rate and airway resistance. However, propranolol-practolol activity ratio values were very different for these two parameters. Thus it appears that bronchial beta-receptors are neither of the s1 nor of the s2 type, as defined by Lands et al. (1967). Comparative studies carried out on atropinized and non-antropinized animals suggest that a reflex cholinergic bronchoconstriction and a direct vasodilatation of the bronchial mucosa may interfere with the bronchodilator effects of isoprenaline.

The effects of cumulative i.v. doses of the β-blocking drrugs practonol, oxprenolol, sotalol, (±)-propanolol and dexpropranolol upon d P d t , left ventricular strain gauge measurements and atrioventricular conduction times have been determined at fixed rates in open-chested vagotomized normal and catecholamine-depleted dogs. Practolol, oxprenolol, sotalol and (±)-propranolol, in doses between 0.1 and 2.56 mg/kg, caused dose-dependent reductions in d P d t and strain gauge measurements and an increase in conduction time. When these drugs were administered in the same dose range to catecholamine-depleted dogs, (±)-propranolol and sotalol did not alter these parameters from control values, whilst oxprenolol and practolol decreased conduction time and increased d P d t and strain gauge measurements. Dexpropranolol, 0.01–2.56 mg/kg, had no effect on d P d t , strain gauge measurements or conduction time in normal or catecholamine-depleted dogs. In doses greater than 2.56 mg/kg, oxprenolol, sotalol and (±)-propranolol caused further increases in conduction time and decrease in d P d t and strain gauge measurements in both normal and catecholamine-depleted dogs. Dexpropanolol in doses greater than 2.56 mg/kg also caused similar changes. In contrast, practolol, in doses up to 82 mg/kg, caused no changes in these parameters additional to those observed at lower doses in either normal or catecholamine-depleted dogs. It is concluded that the initial decreases in d P d t and strain gauge measurements and increase in conduction time caused by low doses of practolol, oxprenolol, sotalol and (±)-propranolol aree due to adrenergic β-receptor blockade. The increase in d P d t , strain gauge measurements and decrease in conduction time in catecholamine-depleted dogs caused by practolol and oxprenolol are due to the intrinsic sympathomimetic activity of these drugs. Further decreases in d P d t and strain gauge measurements, and increase in conduction time after high doses of oxprenolol, sotalol (±)-propranolol and dexopropranolol in both normal catecholamine-depleted dogs indicate that these drugs also have membrane-stabilizing properties. Practolol was shown not to have membrane-stabilizing properties in doses up to 82 mg/kg. The technique described may be useful in relating the additional properties of β-blocking agents to their adrenoceptive blocking actions.

The contractile amplitude and simultaneously recorded maximal rate of rise of depolarization (MRD) of the intracellular action potential were compared in electrically-driven rabbit and guinea-pig atria. β-receptor blocking agents (propranolol, practolol and oxprenolol), carbamyl choline and sodium pentobarbital were pefused through the tissue bath to determine which parameter was a more sensitive criterion of the direct effects of these agents on heart. Propranolol (10−6 M) decreased the contractile amplitude, but had no effect or caused a small increase in MRD in rabbit atria. A higher concentration depressed both MRD and contractile amplitudes. In guinea-pig atria oxprenolol (10−6 M) elicited similar results, practolol (10−5 M) depressed the MRD but not the contractile amplitude and propranolol (10−5 M) had no significant effect on either contraction or MRD. Carbamyl choline and sodium pentobarbital both decreased contractile amplitudes while not affecting the MRD. We conclude that the most sensitive criterion of the direct effects of these drugs on heart depends upon the agent studied and upon experimental conditions.

The local anesthetic properties of propanolol, pronethalol, practolol and procaine were studied in the lobster giant axon. The following observations were made: (1) in the lobster axon propanolol was found to be 12-times and pronethalol 8-times more effective than procaine as local anesthetics: (2) practolol was nearly devoid of local anesthetic activity; (3) propranolol and pronethalol were readily antagonized by high [Ca2+]o; however, procaine was much less susceptible to high [Ca2+]o and required 5-times normal [Ca2+]o to partially antagonize its action; (4) low [Ca2+]o potentiated the local anesthetic effects of propranolol and pronethalol and to a lesser extent those of procaine; (5) a possible site of action of these local anesthetics is discussed.

ICI-50172 was used to evaluate the role of β-receptors in the re-uptake of noradrenaline in sympathetic transmission, since most previous studies on the role of receptors in this process have been based on the effects of α-receptor antagonists. 3 H- dl -noradrenaline was infused intravenously into pithed rats, and 1 hr later the heart was homogenized and the catecholamines were extracted by ion exchange chromatography. Endogenous noradrenaline was estimated fluorimetrically, and radioactivity was measured by scintillation counting. ICI-50172 (10 mg/kg), given intravenously 30 min before the 3 H-noradrenaline infusion caused an insignificant reduction of 7% in the uptake of 3 H-noradrenaline compared with the significant reduction of 57% produced by an equivalent dose of cocaine. Preganglionic stimulation of cardiac sympathetic nerves significantly depleted radioactive noradrenaline stores by 31%, but ICI-50172 did not increase this loss of radioactivity. On the other hand, endogenous noradrenaline stores were not reduced either by stimulation alone, ICI-50172 alone, or stimulation in the presence of the drug. Since ICI-50172 in a dose sufficient for β-blockade neither reduced the uptake of infused noradrenaline, nor facilitated the depletion of noradrenaline stores by nerve stimulation, it appears that β-receptors do not play a major part in the conservation of liberated transmitter.

The effects of promazine and thioridazine on electrically stimulated left rat atria were studied in the presence of varying concentrations of calcium and at different frequencies and strengths of stimulation. An increase of the calcium concentration, [Ca2+]O, in the Ringer solution increased the force of contraction of the preparations. A slight decrease in excitability was found at [Ca2+]O above 4.0 meq/1. Suprathreshold stimulation (50 mA) produced a considerable increase in contractile force when [Ca2+]O was 2.0 meq/1, but on increasing the calcium concentration, this augmentation declined rapidly. On the basis of experiments with an adrenergic β-blocker, practolol, and atropine sulphate, it is concluded that suprathreshold stimulation releases noradrenaline as well as acetylcholine. The decrease in contractile force caused by promazine, 2.5 × 10−5 M, and thioridazine, 2.5 × 10−5 M, was, to a certain extent, antagonized by increasing the concentration of Ca2+. In atria stimulated at suprathreshold values, the results indicate that some sort of competition between Ca2+ and the phenothiazine derivatives may exist, and it is assumed that the drugs interfere with the exchangeability of calcium available for contraction. The decrease in excitability caused by promazine, 2.5 × 10−5 M, seemed to be independent of varying [Ca2+O. An increase in the frequency of contractions increased the threshold for electrical stimulation and reduced the contractile force (‘negative staircase’). Promazine, 2.5 × 10−5 M, enhanced these effects. It is concluded that the degree of the phenothiazine-induced reduction in contractile force of isolated rat atria depends upon the calcium concentration of the Ringer solution and also on the frequency and strength of stimulation.

The mechanism of β-receptor antagonism by propranolol and practolol was investigated on rabbit isolated atrium preparations. Both drugs produced a parallel shift in the log. dose-response curve of isoprenaline without a decrease in the maximal response, suggesting that the antagonism was competitive. The pA2 values for propranolol and practolol were 8.36±0.07 and 6.58±0.04 respectively. These results are discussed.

Rats were treated for seven days with various doses of propranolol, alprenolol, oxprenolol or practolol. Half of the daily dose was administered subcutaneously every 12th hour. The noradrenaline, adrenaline and dopamine contents of the brain, heart and adrenals were generally not considerably altered by the treatment. The noradrenaline level of the brain slightly increased and the adrenaline content tended to be reduced especially after the larger doses, whereas the dopamine content constantly remained unaffected. In the heart the noradrenaline content was insignificantly increased by alprenolol and propranolol but the other drugs showed no tendency to alter the catecholamine content of this organ. The smaller doses had a tendency to increase the adrenaline content of the adrenal glands, which was inversely correlated to the intrinsic sympathomimetic activity of the drugs. The adrenal glands were enlarged by the larger doses of the drugs.

The beta adrenergic receptor blocking properties of 1-(4′-methyl-phenyl)-2-isopropylamino-propanol HCl (H 35/25), 1-(4′-methylphenyl)-2-isopropylaminoethanol — HCl (H 29/50) and 4-(2-hydroxy-3-isopropylaminopropoxy) acetanilide (ICI 50172) were compared according to their ability to block the positive chronotropic, vasodepressor and intestinal inhibitory responses to three doses of isoproterenol in the anesthetized dog. The results obtained suggest that these three agents differ in the selectivity of their beta receptor blocking actions. H 29/50 blocked all three responses to isoproterenol in the same dose range. H 35/25 blocked the vasodepressor but not the positive chronotropic or intestinal inhibitory responses to isoproterenol. ICI 50172 blocked the positive chronotropic response, the intestinal inhibitory response but not the vasodepressor response to isoproterenol. These data support the conclusion that there are beta receptor blocking agents with varying degrees of selectivity.

Chlorpromazine, diazepam, propranolol and practolol protect human erythrocytes against hypotonic hemolysis in vitro. Half-maximal protection was obtained with 4 × 10−6 moles/1 chlorpromazine, 2 × 10−4 moles/1 propranolol, 2 × 10−4 moles/1 diazepam and 4 × 10−4 moles/1 practolol. The interaction between pairs of these four membrane stabilizing agents wasexamined by obtaining dose-response curves for each of them alone as well as in the presence of a constant concentration of one of the others. The maximal antihemolytic effect was not increased by any of the combinations tested, and the dose-response curves for the combined effect conformed to theoretical curves for the combined effect of two drugs acting by the same mechanism.

The β-receptor blocking actions of ICI 50172 were compared with those of propranolol, pronethalol and MJ 1999. It antagonized the cardiac effects but did not affect the depressor action of isoprenaline in the anaesthetized cat. The dose-effect curve for ICI 50172 was flatter than for the other antagonists. Autonomic reflexes did not account for the difference in curves. ICI 50172 antagonized the actions of isoprenaline on guinea-pig bronchi, rabbit intestine and rat uterus. It had one seventh to one threehundredth the potency of propranolol in these respects. It had anti-arrhythmic activity in cats in which ventricular tachycardia was produced by methylchloroform and adrenaline. ICI 50172 had β-receptor agonistic actions on heart, bronchi, intestine and uterus, particularly in high doses; thus, it differed from the usual pattern for partial agonists. Possible explanations for it

In the isolated rabbit aortic strips the contractile response to noradrenaline was antagonized by 1-(o-allylphenoxy)-3-isopropylamino-2-propanol hydrochloride (H 56/28) and by 1-(o-allyloxyphenoxy)-3-isopropylamino-2-propranol hydrochloride (39,089-Ba) but not by 4-(2-hydroxy-3-isopropylaminopropoxy) acetanilide (AY 21,011). H 56/28 displayed mixed competitive and noncompetitive components in its antagonistic effects while 39,089-Ba did not fulfill requirements for competitive antagonism as indicated by the calculated KB (dissociation constant) values. H 56/28 and 39,089-Ba afforded significant protection against α-adrenergic receptor blockade induced by phenoxybenzamine (10−7 g/ml), but AY 21, 011 displayed only weak protective properties. The observed antagonistic effects of H 56/28 and 39,089-Ba against noradrenaline contractions could be due partly to their affinity for α-adrenergic receptor sites and partly to their nonspecific effects when used in high concentrations. Although the response to angiotensin was often potentiated by β-adrenergic blocking agents, these effects were not dose dependent.