Eugenodilol: a third-generation beta-adrenoceptor blocker, derived from eugenol, with alpha-adrenoceptor blocking and beta2-adrenoceptor agonist-associated vasorelaxant activities

Ocimum sanctum [Tulsi] as a Potential Immunomodulator for the Treatment of Ischemic Injury in the Brain

Stroke causes brain damage and is one of the main reasons for death. Most survivors of stroke face long-term physical disabilities and cognitive dysfunctions. In addition, they also have persistent emotional and behavioral changes. The two main treatments that are effective are reperfusion with recombinant tissue plasminogen activator and recanalization of penumbra using mechanical thrombectomy. However, these treatments are suitable only for a few patients due to limitations such as susceptibility to hemorrhage and the requirement for administering tissue plasminogen activators within the short therapeutic window during the early hours following a stroke. The paucity of interventions and treatments could be because of the multiple pathological mechanisms induced in the brain by stroke. The ongoing immune response following stroke has been attributed to the worsening brain injury. Hence, novel compounds with immunomodulatory properties that could improve the outcome of stroke patients are required. Natural compounds and medicinal herbs with anti-inflammatory activities and having minimal or no adverse systemic effect could be beneficial in treating stroke. Ocimum sanctum is a medicinal herb that can be considered an effective therapeutic option for ischemic brain injury. Ocimum sanctum, commonly known as holy basil or "Tulsi," is mentioned as the "Elixir of Life" for its healing powers. Since antiquity, Tulsi has been used in the Ayurvedic and Siddha medical systems to treat several diseases. It possesses immuno-modulatory activity, which can alter cellular and humoral immune responses. Tulsi can be considered a potential option as an immuno-modulator for treating various diseases, including brain stroke. In this review, we will focus on the immunomodulatory properties of Tulsi, specifically its effect on both innate and adaptive immunity, as well as its antioxidant and antiinflammatory properties, which could potentially be effective in treating ongoing immune reactions following ischemic brain injury.

Bisoprolol, Known to Be a Selective β₁-Receptor Antagonist, Differentially but Directly Suppresses IK(M) and IK(erg) in Pituitary Cells and Hippocampal Neurons

Bisoprolol (BIS) is a selective antagonist of β₁ adrenergic receptors. We examined the effects of BIS on M-type K⁺ currents (IK(M)) or erg-mediated K⁺ currents (IK(erg)) in pituitary GH3, R1220 cells, and hippocampal mHippoE-14 cells. As GH₃ cells were exposed to BIS, amplitude of IK(M) was suppressed with an IC50 value of 1.21 μM. The BIS-induced suppression of IK(M) amplitude was not affected by addition of isoproterenol or ractopamine, but attenuated by flupirtine or ivabradine. In cell-attached current, BIS decreased the open probability of M-type K⁺ (KM) channels, along with decreased mean opening time of the channel. BIS decreased IK(erg) amplitude with an IC50 value of 6.42 μM. Further addition of PD-118057 attenuated BIS-mediated inhibition of IK(erg). Under current-clamp conditions, BIS depolarization increased the firing of spontaneous action potentials in GH₃ cells; addition of flupirtine, but not ractopamine, reversed BIS-induced firing rate. In R1220 cells, BIS suppressed IK(M); subsequent application of ML-213(Kv7.2 channel activator) reversed BIS-induced suppression of the current. In hippocampal mHippoE-14 neurons, BIS inhibited IK(M) to a greater extent compared to its depressant effect on IK(erg). This demonstrated that in pituitary cells and hippocampal neurons the presence of BIS is capable of directly and differentially suppressing IK(M) and IK(erg), despite its antagonism of β₁-adrenergic receptors.

Design, synthesis, and in silico studies of novel eugenyloxy propanol azole derivatives having potent antinociceptive activity and evaluation of their β-adrenoceptor blocking property

The design, synthesis, antinociceptive and β-adrenoceptor blocking activities of several eugenyloxy propanol azole derivatives have been described. In this synthesis, the reaction of eugenol with epichlorohydrin provided adducts 3 and 4 which were N-alkylated by diverse azoles to obtain the eugenyloxy propanol azole analogues in good yields. Adducts 3 and 4 were also reacted with azide ion to obtain the corresponding azide 6. The 'Click' Huisgen cycloaddition reaction of 6 with diverse alkynes afforded the title compounds in good yields. The synthesized eugenyloxy propanol azole derivatives were in vivo studied for the acute antinociception on male Spargue Dawley rats using tail-flick test. Compounds 5f, 5g, 7b and 11a exhibited potent analgesic properties in comparison with eugenol as a standard drug. In addition, all compounds were ex vivo tested for β-adrenoceptor blocking properties on isolated left atrium of male rats which exhibited partial antagonist or agonist behaviour compared to the standard drugs. The molecular docking study on the binding site of transient receptor potential vanilloid subtype 1 (TRPV1) has indicated that like capsaicin, eugenyloxy propanol azole analogues exhibited the strong affinity to bind at site of TPRV1 in a "tail-up, head-down" conformation and the presence of triazolyl moieties has played undeniable role in durable binding of these ligands to TRPV1. The in silico pharmacokinetic profile, drug likeness and toxicity predictions carried out for all compounds determined that 5g can be considered as potential antinociceptive drug candidate for future research.

Characterizing the effects of Eugenol on neuronal ionic currents and hyperexcitability

RATIONALE

Eugenol (EUG, 4-allyl-2-methoxyphenol), the main component of essential oil extracted from cloves, has various uses in medicine because of its potential to modulate neuronal excitability. However, its effects on the ionic mechanisms remains incompletely understood.

OBJECTIVES

We aimed to investigate EUG's effects on neuronal ionic currents and excitability, especially on voltage-gated ion currents, and to verify the effects on a hyperexcitability-temporal lobe seizure model.

METHODS

With the aid of patch-clamp technology, we first investigated the effects of EUG on ionic currents in NG108-15 neuronal cells differentiated with cyclic AMP. We then used modified Pinsky-Rinzel simulation modeling to evaluate its effects on spontaneous action potentials (APs). Finally, we investigated its effects on pilocarpine-induced seizures in rats.

RESULTS

EUG depressed the transient and late components of I(Na) in the neurons. It not only increased the degree of I(Na) inactivation, but specifically suppressed the non-inactivating I(Na) (I(Na(NI))). Its inhibition of I (Na(NI)) was reversed by tefluthrin. In addition, EUG diminished L-type Ca(2+) current and delayed rectifier K(+) current only at higher concentrations. EUG's effects on APs frequency reduction was verified by the simulation modeling. In pilocarpine-induced seizures, the EUG-treated rats showed no shorter seizure latency but a lower seizure severity and mortality than the control rats. The EUG's effect on seizure severity was occluded by the I(Na(NI)) antagonist riluzole.

CONCLUSION

The synergistic blocking effects of I (Na) and I(Na(NI)) contributes to the main mechanism through which EUG affects the firing of neuronal APs and modulate neuronal hyperexcitability such as pilocarpine-induced temporal lobe seizures.

Prevention of isoproterenol-induced cardiac hypertrophy by eugenol, an antioxidant

Recent reports on the involvement of calcineurin in cardiac hypertrophy and its susceptibility to free radicals, prompted us to examine possible beneficial effects of dietary antioxidants in this regard. In continuation of initialin vitro studies revealing eugenol to be a potent calcineurin inhibitor, we investigated its ability to reverse isoproterenol-induced cardiac hypertrophy in rats. Intraperitoneal administration of isoproterenol (1 mg/kg body wt/day for 10 days) induced cardiac hypertrophy with increased heart weight and enhanced apoptosis of myocytes concomitant with accumulation of reactive oxygen species, decreased glutathione contents, increased activities of calcineurin and protein kinase C in ventricular tissue. Administering eugenol for 3 days (1 mg/kg body wt/twice a day), followed by combined administration of isoproterenol and eugenol resulted in significant reversal of cardiac hypertrophy and restoration of above changes. These results suggest that eugenol, a natural antioxidant of dietary origin, may offer potential benefits in the management of cardiac hypertrophy.

Study of β-Adrenoreceptor Antagonistic Activity of DPJ 904 in Rats

beta-Adrenoreceptor antagonistic activity of a newly synthesized compound was evaluated in vivo by measuring the mean arterial blood pressure and heart rate of urethane-anesthetized rats treated with isoprenaline. In vitro beta(1)-, beta(2)- and beta(3)-antagonism was studied using isolated rat right atria, isolated rat uterus and isolated rat colon preparations, respectively, in comparison to isoprenaline response. DPJ 904 (1, 3 and 10 mg/kg, i.v.) produced dose-dependent hypotensive and bradycardia response in anesthetized rat. DPJ 904 (1, 3 and 10 mg/kg, i.v.) significantly inhibited both the tachycardial effects and hypotensive response induced by isoprenaline. DPJ 904-antagonized isoprenaline induced positive chronotropic effects of isolated rat right atria and a uterine relaxant effect indicating beta(1)- and beta(2)-blockade. The parallel shift to the right of the concentration-response curve of isoprenaline in the presence of DPJ 904 in KCl (30 mmol/l) induced contraction of the rat colon suggesting that DPJ 904 also possessed beta(3)-adrenoreceptor antagonistic activity. The selectivity to beta(1)-adrenoreceptor was nearly 20.5 times greater than to beta(2)-adrenoreceptor. The present study indicates that DPJ 904 possesses beta-adrenoreceptor antagonistic activity with slightly more affinity to the beta(1)-adrenoreceptor subtype.

Effects of estragole on the compound action potential of the rat sciatic nerve

Estragole, a relatively nontoxic terpenoid ether, is an important constituent of many essential oils with widespread applications in folk medicine and aromatherapy and known to have potent local anesthetic activity. We investigated the effects of estragole on the compound action potential (CAP) of the rat sciatic nerve. The experiments were carried out on sciatic nerves dissected from Wistar rats. Nerves, mounted in a moist chamber, were stimulated at a frequency of 0.2 Hz, with electric pulses of 50-100-micros duration at 10-20 V, and evoked CAP were monitored on an oscilloscope and recorded on a computer. CAP control parameters were: peak-to-peak amplitude (PPA), 9.9 +/- 0.55 mV (N = 15), conduction velocity, 92.2 +/- 4.36 m/s (N = 15), chronaxy, 45.6 +/- 3.74 micros (N = 5), and rheobase, 3.9 +/- 0.78 V (N = 5). Estragole induced a dose-dependent blockade of the CAP. At 0.6 mM, estragole had no demonstrable effect. At 2.0 and 6.0 mM estragole, PPA was significantly reduced at the end of 180-min exposure of the nerve to the drug to 85.6 +/- 3.96 and 13.04 +/- 1.80% of control, respectively. At 4.0 mM, estragole significantly altered PPA, conduction velocity, chronaxy, and rheobase (P < or = 0.05, ANOVA; N = 5) to 49.3 +/- 6.21 and 77.7 +/- 3.84, 125.9 +/- 10.43 and 116.7 +/- 4.59%, of control, respectively. All of these effects developed slowly and were reversible upon a 300-min wash-out. The data show that estragole dose-dependently blocks nerve excitability.

Anti-Hypertension Effect of Vanylidilol: A Phenylaldehyde α/β-Adrenoceptor Blocker with Endothelium-Dependent and K+ Channels Opening-Associated Vasorelaxant Activities

The antihypertensive effect of vanylidilol, a new alpha/beta-adrenoceptor antagonist with endothelium-dependent and K(+)-channel-opening activities, was investigated in normotensive and hypertensive Wistar rats. Vanylidilol competitively antagonized (-)isoproterenol-induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in isolated rat right atria, left atria, and guinea pig tracheal strips in a concentration-dependent manner. Vanylidilol's apparent pA(2) values were 6.36 +/- 0.08 (right atria), 6.41 +/- 0.07 (left atria), and 6.31 +/- 0.06 (trachea). Vanylidilol also produced a competitive antagonism of phenylephrine-induced contraction in the isolated rat aorta with pA(2) values of 6.79 +/- 0.18. In the radioligand binding assay, vanylidilol inhibited [(3)H]CGP-12177 binding to rat ventricle and lung tissues and [(3)H]prazosin binding to brain membranes with Ki values of 535.17, 2,066.69, and 431.11, respectively. In isolated rat thoracic aorta, vanylidilol's vasorelaxant effects on phenylephrine (10 micromol/l)-induced contractions were attenuated by removing endothelium and by the presence of L-N(G)-nitro arginine methyl ester (L-NAME; 100 micromol/l), methylene blue (10 micromol/l), 1H-[1,2,4]oxadiazolol[4,3,-a] quinoxalin-1-one (ODQ; 10 micromol/l), tetraethylammonium (10 mmol/l), glibenclamide (1 micromol/l), apamin (1 micromol/l), and charybdotoxin (0.1 micromol/l). In addition, vanylidilol, in an equally antagonistic activity, inhibited phenylephrine-induced phasic and tonic contractions. Intravenous vanylidilol further reduced mean blood pressure in pentobarbital-anesthetized normotensive Wistar rats in a dose-dependent manner. The oral administration of vanylidilol to conscious spontaneously hypertensive rats had a long-lasting hypotensive effect on the heart rate and decreased it in a dose-dependent manner. Furthermore, vanylidilol's vasodilator effect can be attributed in part to the release of NO or NO-related substance from vascular endothelium, while the endothelium-independent mechanism involved in vanylidilol's relaxation is probably linked to the activation of the K(+) channels and the alpha-adrenoceptor blocking activity in these vessels.

Vasorelaxant effects of eugenol on rat thoracic aorta

Eugenol is a natural pungent substance and the main component of clove oil, with vasorelaxant action. To elucidate some of the possible mechanisms involved in this action isometric tension was measured in aortic rings from male Wistar rats precontracted with phenylephrine (PHE, 10(-7) M) or KCl (75 mM). Responses to increasing concentrations of eugenol (10(-6)-10(-2) M) were obtained in the presence and absence of endothelium. In the presence of eugenol, dose-response curves to PHE (10(-9) to 10(-4) M) and KCl (5-125 mM) were displaced downwards. Concentration-dependent relaxation was observed in rings precontracted with PHE (10(-7) M) and KCl (75 mM). The tension increment produced by increasing external calcium concentration (0.25-3 mM) was also reduced by eugenol (300 microM) treatment. The inhibitory effects of eugenol (300 microM) were compared to those induced by nifedipine (0.01 microM), a selective Ca(2+) channel blocker, producing similar relaxant effects. Two other protocols were performed. After precontraction with PHE (10(-7) M), increasing concentrations of eugenol (10(-6)-10(-2) M) were used before and after N(w)-nitro-L-arginine (L-NAME, 10(-4) M) and methylene blue (10(-5) M) treatment. Eugenol-induced relaxation was reduced by endothelial damage (rubbing), L-NAME and methylene blue treatments. Results suggested that eugenol produces smooth muscle relaxation resulting from the blockade of both voltage-sensitive and receptor-operated channels that are modulated by endothelial-generated nitric oxide.

Inhibitory actions of eugenol on rat isolated ileum

The effects of eugenol (1-2000 microM) on rat isolated ileum were studied. Eugenol relaxed the basal tonus (IC50 83 microM) and the ileum precontracted with 60 mM KCl (IC50 162 microM), an action unaltered by 0.5 microM tetrodotoxin, 0.2 mM N(G)-nitro-L-arginine methyl ester, 0.5 mM hexamethonium, and 1 microM indomethacin. Eugenol did not alter the resting transmembrane potential (Em) of the longitudinal muscle layer under normal conditions (5.0 mM K+) or in depolarised tissues. Eugenol reversibly inhibited contractions induced by submaximal concentrations of acetylcholine (ACh) and K+ (40 mM) with IC50 values of approximately 228 and 237 microM, respectively. Eugenol blocked the component of ACh-induced contraction obtained in Ca(2+)-free solution (0.2 mM EGTA) or in the presence of nifedipine (1 microM). Our results suggest that eugenol induces relaxation of rat ileum by a direct action on smooth muscle via a mechanism largely independent of alterations of Em and extracellular Ca2+ influx.

Vanillylamide-based propanolamine derivative displays alpha/beta-adrenoceptor blocking and vasodilating properties

A propanolamine derivative with vanillylamide base, KMUP 880602, was first investigated under in vivo and in vitro conditions. IV KMUP 880602 (0.1, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardia responses in pentobarbital-anesthetized Wistar rats. KMUP 880602 also markedly inhibited both the tachycardia effects induced by (-)isoproterenol and arterial pressor responses induced by phenylephrine. In isolated guinea pig tissues, KMUP 880602 competitively antagonized (-)isoproterenol-induced positive inotropic and chronotropic effects of the atria and tracheal relaxation responses. The apparent pA2 values KMUP 880602 were 7.24 +/- 0.08 (right atria), 7.42 +/- 0.07 (left atria), and 6.24 +/- 0.06 (trachea). KMUP 880602 also produced a competitive antagonism of norepinephrine-induced contraction in the isolated rat aorta with pA2 values of 7.64 +/- 0.18. In the radioligand-binding assay, [3H]CGP-12177 binding to rat ventricle and lung tissues and [3H]prazosin binding to brain membranes were inhibited by KMUP 880602 with pKi values of 7.27, 6.08, and 8.25, respectively. In isolated rat thoracic aorta, the vasorelaxant effects of KMUP 880602 on phenylephrine-induced contractions were attenuated by pretreatment with tetraethylammonium (10-3 M) and charybdotoxin (10-7 M) but not by glibenclamide, 4-aminopyridine, and apamin. In conclusion, KMUP 880602 is an alpha/beta-adrenoceptor blocker, with selective beta1-adrenoceptor blocking and vascular smooth muscle relaxation activities. Particularly, the vasorelaxant effect of KMUP 880602 is partially mediated by the opening of charybdotoxin-sensitive K+ channel.

The new generation dihydropyridine type calcium blockers, bearing 4-phenyl oxypropanolamine, display alpha-/beta-adrenoceptor antagonist and long-acting antihypertensive activities

A new series of dihydropyridine derivatives, bearing oxypropanolamine moiety on phenyl ring at the 4-position of the dihydropyridine base, were prepared. Oxypropanolamine was synthesized by replacing the phenolic OH of vanillin or other compounds, having a phenyl aldehyde group, with epichlorohydrin, followed by cleavaging the obtained epoxide compounds with tert-butylamine, n-butylamine or 2-methoxy-1-oxyethylamino benzene (guaiacoxyethylamine), respectively. Obtained various oxypropanolamine compounds, still remaining a phenyl aldehyde moiety, were then performed by Hantzsch condensation reaction with methylacetoacetate or ethylacetoacetate, respectively, to give our new series of dihydropyridine linked with the 4-phenyl ring. These compounds were evaluated for inotropic, chronotropic, and aorta contractility that associated with calcium channel and adrenoceptor antagonist activities. Dihydropyridine derivatives that with oxypropanolamine side chain on their 4-phenyl ring associated alpha-/beta-adrenoceptor blocking activities created a new family of calcium entry and the third generation beta-adrenoceptor blockers. Optimizing this research to obtain more potent alpha-/beta-adrenoceptor blocking and long-acting antihypertensive oxypropanolamine on the 4-phenyl ring of dihydropyridine series compounds was thus accomplished and classified as third generation dihydropyridine type calcium channel blockers, in comparison with previous short-acting type nifedipine and long-acting type amlodipine. We concluded that compounds 1a, 1b and 1g showed not only markedly high calcium-antagonistic activity but also the highest antihypertensive effect; compounds 1b, 1c, 1f, 1g, 1i and 1j induced sustained antihypertensive effects are major and attributed to their calcium entry and alpha-adrenoceptor blocking activities in the blood vessel due to their introduction of 2-methoxy, 1-oxyethylamino benzene moiety in the side chain on the 4-phenyl ring of dihydropyridine. Bradycardiac effects of all the compounds 1a-1j resulted from calcium entry and beta-adrenoceptor blocking, which attenuate the sympathetic activation-associated reflex tachycardia in the heart. We selected compound 1b as candidate compound for further pharmacological and pre-clinical evaluation studies.

Lipid solubility of vasodilatory vanilloid-type beta-blockers on the functional and binding activities of beta-adrenoceptor subtypes

Various vanilloid-type beta-adrenoceptor blockers were studied on guinea pig right atrium and trachea and rat colon. In addition, we also investigated their beta(1)-, beta(2)-, and beta(3)-adrenoceptor binding affinities. All these beta-adrenergic antagonists inhibited (-)isoproterenol-induced positive chronotropic effects of the right atrium and tracheal relaxation responses in a concentration-dependent manner. Some of these agents prevented the inhibition of rat colon spontaneous motility by (-)isoproterenol. Of the agents tested, we found that ferulidilol, eugenodilol, eugenolol, isoeugenolol, and ferulinolol, as well as propranolol and metoprolol, possessed beta(3)-adrenoceptor blocking activities, others were nearly without effectiveness. Furthermore, the binding characteristics of vanilloid-type beta-adrenergic antagonists were evaluated in [3H]CGP-12177, a beta(1)/beta(2)-adrenoceptor blocker and a beta(3)-adrenoceptor agonist, binding to beta(1)-, beta(2)-, and beta(3)-adrenoceptor sites in rat ventricle, lung, and interscapular brown adipose tissue (IBAT) membranes, respectively. Eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol were less potent than both propranolol and ferulidilol in competing for the beta(3)-adrenoceptor binding sites. From the results of in vitro functional and binding studies, we suggested that propranolol, ferulidilol, eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol all possessed beta(3)-adrenoceptor blocking activities. On the other hand, we also found that eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol had a low lipid solubility in comparison with propranolol and ferulidilol. In conclusion, we proposed that beta(3)-adrenoceptor antagonistic actions of these vanilloid-type beta-blockers were positively correlated with their lipid solubility.

Pharmacological effects of an aldehyde type alpha/beta-adrenoceptor blocking agent with vasodilating properties

KMUP 880723 (0.5, 1.0, and 3.0 mg/kg, iv) produced dose-dependent hypotensive and bradycardia responses in pentobarbital-anesthetized Wistar rats. KMUP 880723 (1.0 mg/kg, iv) also markedly inhibited both the tachycardia effects induced by (-)isoproterenol and arterial pressor responses induced by phenylephrine. In the isolated Wistar rat right atria, left atria, and guinea pig tracheal strips, KMUP 880723 competitively antagonized the (-)isoproterenol-induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol suggested that KMUP 880723 was a beta(1)/beta(2)-adrenoceptor competitive antagonist. The apparent pA(2) values were 6.89+/-0.10 in the right atria, 7.02+/-0.09 in the left atria, and 6.59+/-0.11 in the trachea, indicating that KMUP 880723 was a nonselective beta-adrenoceptor blocker. In thoracic aorta experiments, KMUP 880723 also produced a competitive antagonism of norepinephrine-induced contraction with a pA(2) value of 7.14+/-0.06. In isolated rat thoracic aorta, KMUP 880723 more potently relaxed the contractions induced by norepinephrine (3 x 10(-6) M) than those by high K(+) (75 mM). In the radioligand-binding assay, the pK(i) values of [3H]CGP-12177 binding to rat ventricle and lung membranes were 6.56 and 6.40, respectively, and the value of [3H]prazosin binding to rat brain membranes was 6.66. These results further confirmed the alpha/beta-adrenoceptor blocking activities of KMUP 880723 reported in the functional studies. We conclude that KMUP 880723 is a nonselective beta-adrenoceptor antagonist with alpha-adrenoceptor blocking-associated vasorelaxant activity.

Vanidipinedilol: a vanilloid-based beta-adrenoceptor blocker displaying calcium entry blocking and vasorelaxant activities

Calcium channel and beta-adrenoceptor blockade have proved highly useful in antihypertensive therapy. Studies of the mechanisms of action of vanidipinedilol that combine these effects within a single molecule are described here. Intravenous injection of vanidipinedilol (0.1, 0.25, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardic responses, significantly different from nifedipine-induced (0.5 mg/kg, i.v.) hypotensive and reflex tachycardic effects in pentobarbital-anesthetized Wistar rats. A single oral administration of vanidipinedilol at doses of 10, 25, and 50 mg/kg dose-dependently reduced blood pressure with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat atrium, vanidipinedilol (10(-7), 10(-6), and 10(-5) M) competitively antagonized the (-)isoproterenol-induced positive chronotropic and inotropic effects and inhibited the increase in heart rate induced by Ca2+ (3.0-9.0 mM) in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol and CaCl2 suggested that vanidipinedilol possessed beta-adrenoceptor-blocking and calcium entry-blocking activities. On tracheal strips of reserpinized guinea pig, cumulative doses of vanidipinedilol (10(-10) to 3x10(-6) M) produced dose-dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10(-10), 10(-9), 10(-8) M), a beta2-adrenoceptor antagonist, shifted the vanidipinedilol concentration-relaxation curve significantly to a region of higher concentrations. These results implied that vanidipinedilol had a partial beta2-agonist activity. In the isolated thoracic aorta of rat, vanidipinedilol had a potent effect inhibiting high-K+-induced contractions. KCI-induced intracellular calcium changes of blood vessel smooth muscle cell (A7r5 cell lines) determined by laser cytometry also was decreased after administration of vanidipinedilol (10(-8), 10(-7), 10(-6) M). Furthermore, the binding characteristics of vanidipinedilol and various antagonists were evaluated in [3H]CGP-12177 binding to ventricle and lung and [3H]nitrendipine binding to cerebral cortex membranes in rats. The order of potency of beta1- and beta2-adrenoceptor antagonist activity against [3H]CGP-12177 binding was (-)propranolol (pKi, 8.59 for beta1 and 8.09 for beta2) > vanidipinedilol (pKi, 7.09 for beta1 and 6.64 for beta2) > atenolol (pKi, 6.58 for beta1 and 5.12 for beta2). The order of potency of calcium channel antagonist activity against [3H]nitrendipine binding was nifedipine (pKi, 9.36) > vanidipinedilol (pKi, 8.07). The ratio of beta1-adrenergic-blocking/calcium entry-blocking selectivity is 0.1 and indicated that vanidipinedilol revealed more in calcium entry-blocking than in beta-adrenergic-blocking activities. It has been suggested that vanidipinedilol-induced smooth muscle relaxation may involve decreased entry of Ca2+ and partial beta2-agonist activities. In conclusion, vanidipinedilol is a nonselective beta-adrenoceptor antagonist with calcium channel blocking and partial beta2-agonist associated vasorelaxant and tracheal relaxant activities. Particularly, the vasodilator effects of vanidipinedilol are attributed to a synergism of its calcium entry blocking and partial beta2-agonist activities in the blood vessel. A sustained bradycardic effect results from beta-adrenoceptor blocking and calcium entry blocking, which blunts the sympathetic activation-associated reflex tachycardia in the heart.