Inhibition of rat hippocampal excitability by the Aconitum alkaloid, 1-benzoylnapelline, but not by napelline.

The effects of the two structurally related Aconitum alkaloids, 1-benzoylnapelline and napelline, were investigated by extracellular recording of the stimulus-evoked population spike in the CA1 region of rat hippocampal slices in vitro. 1-Benzoylnapelline (1-100 microM) exerted a depressant action on the orthodromic as well as on the antidromic population spike. Napelline failed to evoke a significant effect at concentrations up to 100 microM. The inhibitory action induced by 1-benzoylnapelline was enhanced when the frequency of electrical stimulation was increased. In contrast, reversal of the inhibitory effect was accelerated when stimulation frequency was decreased. The activity-dependent mode of action of 1-benzoylnapelline raised the question of whether the drug is effective to suppress epileptiform activity. The results obtained from experiments on epileptiform hippocampal slices revealed a reduction of the burst duration and of the number of spikes in the burst as well as attenuation of the amplitude of the population spikes. These data support the conclusion that 1-benzoylnapelline, in contrast to the structurally related compound, napelline, has an activity-dependent inhibitory action on central neurons.

Blocking effects of hypaconitine and aconitine on nerve action potentials in phrenic nerve-diaphragm muscles of mice.

The mechanisms of neuromuscular blockade by hypaconitine and aconitine were investigated electrophysiologically in isolated phrenic nerve-diaphragm muscles of mice. Hypaconitine (0.08-2 microM) and aconitine (0.3-2 microM) depressed the nerve-evoked twitch tension, without affecting the contraction evoked by stimulation of the muscle. At the concentrations of hypaconitine (up to 5 microM) and aconitine (up to 2 microM) that depressed the nerve-evoked twitch tension, the resting membrane potential of the muscle cells was unchanged. Hypaconitine (0.1-2 microM) and aconitine (2 microM) blocked the end-plate potential (epp), without affecting the amplitude of the miniature epp (mepp). The quantal content of end-plate potentials was decreased by these agents in parallel with the decrement in amplitude. The nerve compound action potential was inhibited by hypaconitine (5 microM) and aconitine (2-10 microM), as well as by 1 microM tetrodotoxin (TTX). When the nerve compound action potential was completely blocked by 2 microM aconitine, the muscle action potential was unaffected, although 1 microM TTX suppressed both potentials to the same degree. These results indicate the neuromuscular blockade produced by hypaconitine and aconitine were caused by reducing the evoked quantal release. The mechanism of this effect was attributed mainly to blocking of the nerve compound action potential.

[Effect of a new anti-arrhythmia drug allapinin on hemodynamics in patients with a persistent form of atrial fibrillation before and after restoration of sinus rhythm]. / Vliianie novogo antiaritmicheskogo preparata allapinina na gemodinamiku u bol'nykh s postoianno'i formoi mertsatel'noi aritmii do i posle vosstanovleniia sinusovogo ritma.

Echocardiographic study was performed in 24 patients with persistent atrial fibrillation (PAF) without clinical signs of circulatory failure. When treated with allapinin , all the patients with PAF showed a significant increase in heart rate (HR) and cardiac output (CO) and a decrease in total peripheral vascular resistance (TPVR). No substantial changes in the major hemodynamic parameters were found in patients with higher left ventricular dimensions; however, a significant rise in end systolic volume (ESV) was noted. There was significantly lower HR, diminished ESV, higher stroke volume and increased CO, elevated ejection fraction and TPVR with sinus rhythm. In PAF patients without apparent signs of circulatory failure, hemodynamic effects of allapinin may be accounted for by its direct vasodilatory action on the arterial bed and by its ability to affect cardiac autonomic innervation. A moderate cardiodepressive effect of the agent may be reflected by deteriorated latent signs of myocardial incompetence which are levelled off following sinus rhythm recovery.

Aconitine-induced modification of single sodium channels in neuroblastoma cell membrane.

Aconitine-modified sodium channels in the neuroblastoma cell membrane were investigated with patch-clamp technique in outside-out configuration. When aconitine (0.1 mmol/l) was present in the pipette solution two types of modified single sodium channels were observed. The first type showed openings with normal amplitude (slope conductance 15.5 pS) and bursting behaviour. The second type of modified channel openings was characterized with low amplitude (slope conductance 2.8 pS) and longer open time as comparing to unmodified channels. The low-amplitude channels were shown to have altered ion selectivity: they were permeable to NH4+. Both populations of aconitine-modified channels could be blocked by tetrodotoxin. In contrast to macroscopic current experiments (Mozhayeva et al. 1977) the development of aconitine modification was not affected by repetitive stimulation and external application of the agent had no effect on single sodium channels in outside-out membrane patch.

Separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography.

The separation and characterization of the metabolic products of lappaconitine in rat urine by high-performance liquid chromatography with electrochemical and ultraviolet detection are described. Urine samples from rats intravenously administered lappaconitine hydrobromide were extracted with chloroform and then purified on a Sep-Pak C18 cartridge. The subsequent resolution into individual compounds was achieved by high-performance liquid chromatography. Identification of these compounds was based on comparisons of the chromatographic behaviour and the detector response with those of authentic samples. Changes in the ratio of lappaconitine to its metabolites in rat urine with time after dosing led to a proposal for one of the probable metabolic pathways of lappaconitine in the rat.

[Determination of alkaloids in Aconite roots by HPLC].

Three alkaloids contained in Aconite roots, aconitine, mesaconitine and hypaconitine, were determined by HPLC. 15 samples (8 species) of Aconite roots were analysed. The results reveal that most of them contain the three alkaloids in different contents, and some of them contain one or two alkaloids.

[The effect of allapinine on the sodium currents of isolated trigeminal ganglion neurons and cardiomyocytes of rats]. / Vliianie allapinina na natrievye toki izolirovannykh neironov trigeminal'nogo gangliia i kardiomiotsitov krys.

Block of sodium currents by allapinine (diterpene alkaloid with strong antiarrhythmic properties) was investigated in isolated, voltage-clamped trigeminal neurons of a rat and single ventricular myocytes of a neonatal rat. Allapinine (in micromolar concentrations) produced a 70-90% decrease of the sodium current amplitude without any changes in voltage-dependent properties of INa in both neurons and cardiomyocytes. Allapinine also blocked the aconitine-modified sodium current. An increase of depolarization frequencies (0.5 to 5.0 Hz) produced no additional block of sodium currents in allapinine-bathed neurons and ventricular myocytes.

Studies on the metabolism of lappaconitine in humans. Identification of the metabolites of lappaconitine in human urine by high performance liquid chromatography.

The metabolites of lappaconitine in the urine of humans having been previously administered intramuscularly with lappaconitine hydrobromide were studied using high performance liquid chromatography with electrochemical and ultraviolet detection. The urine was extracted by means of liquid- and solid-phase extractions. Each of the metabolites of lappaconitine was purified by high performance liquid chromatography on a reversed phase column and identified on the basis of the chromatographic behaviour and the detector response. It was proved that lappaconitine, N-deacetyl-16-O-demethyllappaconitine and N-deacetyllappaconitine were excreted in urine from humans receiving lappaconitine.

[Effects of reserpine and 5-HT on analgesia induced by lappaconitine and N-deacetyllappaconitine].

In the rat tail-flick test it was shown that ip lappaconitine (LA) 1-6 mg/kg, N-deacetyllappaconitine (DLA) 4-10 mg/kg or icv DLA 20-60 micrograms/rat exhibited a dose-dependent analgesic activity, but icv LA 20-40 micrograms/rat was inactive. The analgesic potency of ip LA was a little more potent than that of DLA and slightly weaker than that of morphine (P less than 0.05). Combined ip of subanalgesic doses of morphine and LA or DLA produced significant analgesic action. Analgesia mediated by LA was not antagonized by naloxone. The analgesic effect induced by LA or DLA was abolished and restored 3 and 120 h, respectively, after ip reserpine 3 mg/kg. Concomitant administration of 1-tryptophan or 5-HT as well as premedication of alpha-methyldopa prevented reserpine-induced decrease on LA or DLA analgesia. The elevation of brain 5-HT level by icv 5-HT significantly enhanced the analgesia of LA and DLA. LA- or DLA-induced analgesia was attenuated by pretreatment of p-chlorophenylalanine but this attenuation was reversed by icv 5-HT. p-Chloroamphetamine also markedly reduced LA- or DLA-induced analgesia. It is concluded that the central serotoninergic system is involved in the modulation of LA- or DLA-induced analgesia.

[Effects of central Ca2+ on analgesic action of lappaconitine].

Lappaconitine (LA), isolated from Aconitum sinomontanum Nakai, was characterized as analgesic principle by our laboratory. The analgesic effect of ip LA 6 mg/kg as measured in the rat tail-flick test was reduced by icv CaCl2 or MgCl2 0.1 or 1 mumol/rat. BaCl2 was inactive. The analgesic action induced by LA was potentiated by ethylene glycol tetraacetic acid (EGTA, 0.2 mumol/rat icv) but not by ethylenediamine tetraacetic acid (EDTA, 0.2 or 0.4 mumol/rat icv). The calcium antagonists nifedipine (5 mg/kg ip) and verapamil (1 mumol/rat icv) partially reversed the Ca2+ antagonistic effect on LA analgesia, although nifedipine did not enhance LA analgesic action and only at 15 min after medication did verapamil exhibit enhancement of LA analgesia. The analgesic activity of LA was reduced and augmented by microinjection of CaCl2 0.5 mumol and EGTA 50 nmol to periaqueductal gray (PAG) area, respectively. These results suggest that LA can produce analgesia, possibly through a decrease in cellular calcium availability and PAG may be involved in the Ca2+ antagonistic effect on LA analgesia.

Putrescine reverses aconitine-induced arrhythmia in rats.

Putrescine, (150-300 mg kg-1 i.v.) injected into anaesthetized rats reversed aconitine-induced arrhythmia and restored sinus rhythm. In the same experimental model, quinidine and lignocaine had a transient therapeutic effect, procainamide was practically ineffective and verapamil worsened the aconitine arrhythmia, causing the death of all treated animals. These data demonstrate that putrescine has an antiarrhythmic effect in an experimental model particularly resistant to usual antiarrhythmic treatments.

[Effect of anti-arrhythmia drugs on the beta2 receptor-dependent adenyl cyclase system of lymphocytes in patients with cardiac rhythm disorders]. / Vliianie antiaritmicheskikh preparatov na beta2-retseptorzavisi- muiu adeniultsiklaznuiu sistemu limfotsitov bo'lnykh s narushe- niiami ritma serdtsa.

The authors analyzed the density of beta 2-adrenoreceptors, their affinity for catecholamines and activity of peripheral lymphocyte adenylate cyclase in healthy donors and patients with frequent ventricular premature contraction (VPC) in their pretreatment state and during short-term ethmosine or allapinine therapy. The density of beta 2-adrenoreceptors was increased by 43%, whereas guanylimidodiphosphate- or forskolin-induced stimulation of adenylate cyclase was decreased in the lymphocytes of VPC patients as compared to those of healthy donors. Ethmosine therapy failed to produce any changes in the density and affinity of the receptors for catecholamines. Allapinine caused a 47% reduction in beta 2-adrenoreceptor density and a 10(2)-10(3)-fold decrease in receptor affinity for 1-isoproterenol. After discontinuation of allapinine, the changes in beta 2-adrenoreceptor density and affinity for catecholamines remained on days 3 and 7, respectively. The clinical effect of both ethmosine and allapinine was accompanied by an increase in lymphocyte adenylate cyclase activity.

[Pharmacodynamics of allapinin and its possible adverse effects]. / Farmakodinamika allapinina i ego vozmozhnye pobochnye éffekty.

Allapinine (Class IC), a new antiarrhythmic agent, was studied in 76 patients with premature contraction. Allapinine was found to be beneficial both in ventricular and supraventricular premature beats. Oral allapinine usually showed its effect 40-60 minutes following its administration, its maximum action being 4-5 hours later, its duration was some 8 hours. The optimal dose of the drug amounted to 75 mg/day. Larger-dose allapinine produced adverse effects, its lower dosage had no antiarrhythmic effect. The drug failed to affect blood pressure, heart rate, QT interval length. The PQ interval and QRS complex were increased. The side effects were dose-dependent. There was a risk of the drug's arrhythmogenic effect.

[Pharmacokinetics and pharmacodynamics of the new Russian anti-arrhythmia drug allapinin]. / Farmakokinetika i farmakodinamika novogo otechestvennogo antiaritmicheskogo preparata allapinina.

Pharmacokinetics of allapinin tablets, used as a single dose, alone or in combination with other antiarrhythmic drugs (cordarone, mexitil, ritmilen) were assessed in 11 patients with frequent extrasystoles. Allapinin pharmacokinetic pattern was basically similar in patients in whom it was very effective and those in whom it had no effect. Combined use of the above-mentioned antiarrhythmic drugs and allapinin did not affect the latter's pharmacokinetic parameters. Allapinin pharmacokinetics can be described using a one-part model.

[Allapinin pharmacokinetics after its single intravenous administration]. / Allapinin. Farmakokinetika pri razovom vnutrivennom vvedenii.

Allapinin after i.v. bolus infusion in a dose of 30 mg is relatively quickly eliminated from blood (in patients without congestive heart failure half-elimination period is 2.4 +/- 0.5 h and clearance is 79.0 +/- 8.9 l/h) which makes a good reason for its intravenous infusion according to the scheme "load dose + drop infusion". Marked heart failure in patients with acute myocardial infarction compared to patients without heart failure results in reduced elimination rate, decreased clearance, significantly increased plasma allapinin concentration which should be taken in account when choosing the regime of drug infusion. The elimination of allapinin is mainly metabolic and not renal (only about 17% of the drug is excreted with urine).

[Effect of a single oral dose of allapinin in patients with chronic ventricular extrasystole]. / Deistvie allapinina pri odnokratnom prieme vnutr' u bol'nykh s khronicheskoi zheludochkovoi ekstrasistoliei.

Effect of a new antiarrhythmic drug allapinin was studied in 21 patients with chronic ventricular extrasystoles by an acute drug test with single oral dose of the drug controlled by 12-hour Holter monitoring. In 9 cases the dose was 50 mg. Maximal total reduction of ventricular ectopic complexes (VEC) per hour was 67 +/- 28% (mean value); in 5 cases (55%) it exceeded 90% of basal level. At peak of action, PQ interval increased by 15%, QRS--by 14%, QT was not significantly changed. In 14 cases the dose was 75 micrograms. Maximal VEC number reduction per hour was on the average 89 +/- 18% and in 12 cases (88%) exceeded 90%. PQ increased by 22%, QRS--by 23% and QT by 9% though JT was not changed (average peak values). It is thus concluded that single oral dose of allapinin has pronounced antiarrhythmic effect in patients with VEC and influences ECG intervals in the way characteristic for class IC antiarrhythmic drugs. The degree of the effect depends on the dose.

[Studies on the chemical constituents of Aconitum szechenyianum Gay].

Five constituents were isolated from Aconitum szechenyianum Gay. The structures of these compounds were identified as beta-sitosterol (I), aconitine (II), 3-acetylaconitine (III), songorine (IV) and a new compound whose structure was elucidated to be szechenyine (V) on the basis of UV, IR, 1HNMR, 13CNMR and Mass spectra.

Pharmacological studies of lappaconitine. Occurrence of analgesic effect without opioid receptor.

The contribution of opioid receptor to lappaconitine (LA) induced analgesia was investigated by in vivo and in vitro methods. The antagonistic effects of naloxone (NLX) on the analgesic actions of LA (s.c.) and morphine (MOR, s.c.) were determined by the tail pressure method, the hot plate method and the acetic acid-induced writhing method in mice. The ED50 values of MOR in the absence of NLX were 3.82, 0.50 and 0.33 mg/kg, respectively, but in the presence of NLX, the analgesic effect of MOR was decreased and the ED50 values were changed to 41.6, 4.40 and 5.97 mg/kg, respectively. However, NLX did not affect the analgesic activity of LA. The ED50 values of LA in the three methods were 9.12, 3.34 and 1.70 mg/kg in the absence of NLX and 12.1, 4.19 and 2.88 mg/kg in the presence of NLX, respectively. The inhibitory effect of the LA on the electrically evoked contractions of isolated guinea-pig ileum was weaker than that of MOR, and differently from MOR, its effect was not antagonized by NLX. Additionally, LA did not abolish the electrically evoked contractions of isolated rabbit and mouse vas deferens. In conclusion, the results suggest that the opioid receptor was not involved in the analgesic activity of LA.