Protection by imidazol(ine) drugs and agmatine of glutamate-induced neurotoxicity in cultured cerebellar granule cells through blockade of NMDA receptor. (1/11)

This study was designed to assess the potential neuroprotective effect of several imidazol(ine) drugs and agmatine on glutamate-induced necrosis and on apoptosis induced by low extracellular K+ in cultured cerebellar granule cells. Exposure (30 min) of energy deprived cells to L-glutamate (1-100 microM) caused a concentration-dependent neurotoxicity, as determined 24 h later by a decrease in the ability of the cells to metabolize 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) into a reduced formazan product. L-glutamate-induced neurotoxicity (EC50=5 microM) was blocked by the specific NMDA receptor antagonist MK-801 (dizocilpine). Imidazol(ine) drugs and agmatine fully prevented neurotoxicity induced by 20 microM (EC100) L-glutamate with the rank order (EC50 in microM): antazoline (13)>cirazoline (44)>LSL 61122 [2-styryl-2-imidazoline] (54)>LSL 60101 [2-(2-benzofuranyl) imidazole] (75)>idazoxan (90)>LSL 60129 [2-(1,4-benzodioxan-6-yl)-4,5-dihydroimidazole](101)>RX82 1002 (2-methoxy idazoxan) (106)>agmatine (196). No neuroprotective effect of these drugs was observed in a model of apoptotic neuronal cell death (reduction of extracellular K+) which does not involve stimulation of NMDA receptors. Imidazol(ine) drugs and agmatine fully inhibited [3H]-(+)-MK-801 binding to the phencyclidine site of NMDA receptors in rat brain. The profile of drug potency protecting against L-glutamate neurotoxicity correlated well (r=0.90) with the potency of the same compounds competing against [3H]-(+)-MK-801 binding. In HEK-293 cells transfected to express the NR1-1a and NR2C subunits of the NMDA receptor, antazoline and agmatine produced a voltage- and concentration-dependent block of glutamate-induced currents. Analysis of the voltage dependence of the block was consistent with the presence of a binding site for antazoline located within the NMDA channel pore with an IC50 of 10-12 microM at 0 mV. It is concluded that imidazol(ine) drugs and agmatine are neuroprotective against glutamate-induced necrotic neuronal cell death in vitro and that this effect is mediated through NMDA receptor blockade by interacting with a site located within the NMDA channel pore.  (+info)

Antazoline therapy of recurrent refractory supraventricular arrhythmias--a preliminary report. (2/11)

Seven patients with chronic or recurrent supraventricular tachyarrhythmias were selected for a trial of antazoline therapy because sinus rhythm or a controlled ventricular response could not be achieved with quinidine, procainamide, digitalis or propranolol. Sinus rhythm was established by either intravenous administration of antazoline or direct-current countershock, and has been maintained in all for 4 to 16 months by oral administration of antazoline. Side effects were minor. Antazoline is a sufficiently promising antiarrhythmic agent to warrant large-scale controlled studies.  (+info)

Imidazoline antagonists of alpha 2-adrenoceptors increase insulin release in vitro by inhibiting ATP-sensitive K+ channels in pancreatic beta-cells. (3/11)

1. Islets from normal mice were used to study the mechanisms by which imidazoline antagonists of alpha 2-adrenoceptors increase insulin release in vitro. 2. Alinidine, antazoline, phentolamine and tolazoline inhibited 86Rb efflux from islets perifused with a medium containing 3 mM glucose, i.e. under conditions where many adenosine 5'-triphosphate (ATP)-sensitive K+ channels are open in the beta-cell membrane. They also reduced the acceleration of 86Rb efflux caused by diazoxide, an opener of ATP-sensitive K+ channels. 3. ATP-sensitive and voltage-sensitive K+ currents were measured in single beta-cells by the whole-cell mode of the patch-clamp technique. Antazoline more markedly inhibited the ATP-sensitive than the voltage-sensitive current, an effect previously observed with phentolamine. Alinidine and tolazoline partially decreased the ATP-sensitive K+ current. 4. The four imidazolines reversed the inhibition of insulin release caused by diazoxide (through opening of ATP-sensitive K+ channels) or by clonidine (through activation of alpha 2-adrenoceptors) in a concentration-dependent manner. Only the former effect correlated with the ability of each drug to increase control insulin release stimulated by 15 mM glucose alone. 5. It is concluded that the ability of imidazoline antagonists of alpha 2-adrenoceptors to increase insulin release in vitro can be ascribed to their blockade of ATP-sensitive K+ channels in beta-cells rather than to their interaction with the adrenoceptor.  (+info)

Effect of histamine receptor antagonists on aminophylline-induced seizures and lethality in mice. (4/11)

The aim of this study was to evaluate the effects of H(1) (antazoline and astemizole) or H(2) (cimetidine and famotidine) histamine receptor antagonists on the clonic phase, tonic seizures and morality of mice challenged with aminophylline to induce convulsions in mice. Moreover, the total plasma and brain concentrations of theophylline were evaluated. Astemizole (1 mg/kg) did not affect the threshold for aminophylline-induced seizures, but when administered at a dose of 2 mg/kg, it significantly reduced the CD(50) value of aminophylline from 249 mg/kg to 211 mg/kg (p < 0.01). The remaining histamine receptor antagonists studied i.e., antazoline (up to 1 mg/kg), cimetidine (up to 40 mg/kg) and famotidine (up to 10 mg/kg) had no impact on seizure susceptibility in aminophylline-induced convulsions. Furthermore, astemizole (2 mg/kg) decreased latency to the clonic phase of aminophylline-induced convulsions from 51.1 +/- 4.5 to 32.1 +/- 4.3 min (p < 0.01). It is noteworthy that astemizole, a novel H(1) receptor antagonist, did not alter the brain and plasma levels of theophylline, so the existence of pharmacokinetic interactions was excluded. Our results indicate that some interactions between methylxanthines and histamine receptor antagonists may be clinically important since these drugs are usually combined during the treatment of status asthmaticus.  (+info)

A rapid derivative spectrophotometric method for simultaneous determination of naphazoline and antazoline in eye drops. (5/11)

A zero-crossing first-derivative spectrophotometric method is applied for the simultaneous determination of naphazoline hydrochloride and antazoline phosphate in eye drops. The measurements were carried out at wavelengths of 225 and 252 nm for naphazoline hydrochloride and antazoline phosphate, respectively. The method was found to be linear (r2>0.999) in the range of 0.2-1 microg/ml for naphazoline hydrochloride in the presence of 5 microg/ml antazoline phosphate at 225 nm. The same linear correlation (r2>0.999) was obtained in the range of 1-10 microg/ml of antazoline phosphate in the presence of 0.5 microg/ml of naphazoline hydrochloride at 252 nm. The limit of determination was 0.2 microg/ml and 1 microg/ml for naphazoline hydrochloride and antazoline phosphate, respectively. The method was successfully used for simultaneous analysis of naphazoline hydrochloride and antazoline phosphate in eye drops without any interference from excipients and prior separation before analysis.  (+info)

Antazoline in the treatment of cardiac arrhythmias. (6/11)

Antazoline was administered in sixty-five episodes of various types of cardiac arrhythmia. A complete suppression of the ectopic beats was achieved in five out of six episodes of premature atrial systoles and in twenty-one of the twenty-four episodes of ventricular premature systoles. Conversion to sinus rhythm was observed in seven out of ten and four out of five episodes of paroxysmal atrial and nodal tachycardia respectively. Six out of ten episodes of ventricular tachycardia were controlled by intravenous therapy. However, the drug proved to be ineffective in cases of atrial fibrillation. The side-effects were few and transitory, consisting of nausea, vomiting and drowsiness.  (+info)

Clinical efficacy of antazoline in rapid cardioversion of paroxysmal atrial fibrillation--a protocol of a single center, randomized, double-blind, placebo-controlled study (the AnPAF Study). (7/11)

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An analysis of the purinergic component of active muscle vasodilatation obtained by electrical stimulation of the hypothalamus in rabbits. (8/11)

In anaesthetized rabbits, electrical stimulation of the hypothalamus in areas analogous to the defence area in cats produces the 'defence reaction.' This response includes signs of arousal and a large increase in blood flow to skeletal muscle in the hind limb caused by a vasodilatation in the skeletal muscle vasculature. The vasodilatation is a sympathetic response, and it is not dependent upon muscle activity in the hind limb. The muscle vasodilatation is insensitive to alpha-adrenoceptor, beta-adrenoceptor, cholinoceptor and histamine receptor antagonists. Intra-arterial injections of the purinoceptor agonists, adenosine triphosphate (ATP) and adenosine, mimic the vasodilatation produced by electrical stimulation. The P1-purinoceptor blocker, aminophylline, attenuates adenosine-induced vasodilatation, but it does not affect the vasodilatation produced by ATP or hypothalamic stimulation. The P2-purinoceptor blocker, antazoline, attenuates the vasodilatation produced by both ATP and hypothalamic stimulation. Our results suggest that the muscle vasodilatation produced by hypothalamic stimulation is mediated by purinergic nerves which release ATP and act on P2-purinoceptors.  (+info)

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