Ginsenoside Rg1 Reduces Cardiotoxicity While Increases Cardiotonic Effect of Aconitine in vitro / 中国结合医学杂志

OBJECTIVE@#To explore the synergic mechanism of ginsenoside Rg1 (Rg1) and aconitine (AC) by acting on normal neonatal rat cardiomyocytes (NRCMs) and pentobarbital sodium (PS)-induced damaged NRCMs.@*METHODS@#The toxic, non-toxic, and effective doses of AC and the most suitable compatibility concentration of Rg1 for both normal and damaged NRCMs exposed for 1 h were filtered out by 3- (4,5)-dimethylthiahiazo (-z-y1)-3,5-diphenytetrazoliumromide, respectively. Then, normal NRCMs or impaired NRCMs were treated with chosen concentrations of AC alone or in combination with Rg1 for 1 h, and the cellular activity, cellular ultrastructure, apoptosis, leakage of acid phosphatase (ACP) and lactate dehydrogenase (LDH), intracellular sodium ions [Na+], potassium ions [K+] and calcium ions [Ca2+] levels, and Nav1.5, Kv4.2, and RyR2 genes expressions in each group were examined.@*RESULTS@#For normal NRCMs, 3000 µ mol/L AC significantly inhibited cell viability (P<0.01), promoted cell apoptosis, and damaged cell structures (P<0.05), while other doses of AC lower than 3000 µ mol/L and the combinations of AC and Rg1 had little toxicity on NRCMs. Compared with AC acting on NRCMs alone, the co-treatment of 3000 and 10 µ mol/L AC with 1 µ mol/L Rg1 significantly decreased the level of intracellular Ca2+ (P<0.01 or P<0.05), and the co-treatment of 3000 µ mol/L AC with 1 µ mol/L Rg1 significantly decreased the level of intracellular Ca2+ via regulating Nav1.5, RyR2 expression (P<0.01). For damaged NRCMs, 1500 µ mol/L AC aggravated cell damage (P<0.01), and 0.1 and 0.001 µ mol/L AC showed moderate protective effect. Compared with AC used alone, the co-treatment of Rg1 with AC reduced the cell damage, 0.1 µ mol/L AC with 1 µ mol/L Rg1 significantly inhibited the level of intracellular Na+ (P<0.05), 1500 µ mol/L AC with 1 µ mol/L Rg1 significantly inhibited the level of intracellular K+ (P<0.01) via regulating Nav1.5, Kv4.2, RyR2 expressions in impaired NRCMs.@*CONCLUSION@#Rg1 inhibited the cardiotoxicity and enhanced the cardiotonic effect of AC via regulating the ion channels pathway of [Na+], [K+], and [Ca2+].

Quantitative Electrophysiological Evaluation of the Analgesic Efficacy of Two Lappaconitine Derivatives: A Window into Antinociceptive Drug Mechanisms / 神经科学通报·英文版

Quantitative evaluation of analgesic efficacy improves understanding of the antinociceptive mechanisms of new analgesics and provides important guidance for their development. Lappaconitine (LA), a potent analgesic drug extracted from the root of natural Aconitum species, has been clinically used for years because of its effective analgesic and non-addictive properties. However, being limited to ethological experiments, previous studies have mainly investigated the analgesic effect of LA at the behavioral level, and the associated antinociceptive mechanisms are still unclear. In this study, electrocorticogram (ECoG) technology was used to investigate the analgesic effects of two homologous derivatives of LA, Lappaconitine hydrobromide (LAH) and Lappaconitine trifluoroacetate (LAF), on Sprague-Dawley rats subjected to nociceptive laser stimuli, and to further explore their antinociceptive mechanisms. We found that both LAH and LAF were effective in reducing pain, as manifested in the remarkable reduction of nocifensive behaviors and laser-evoked potentials (LEPs) amplitudes (N2 and P2 waves, and gamma-band oscillations), and significantly prolonged latencies of the LEP-N2/P2. These changes in LEPs reflect the similar antinociceptive mechanism of LAF and LAH, i.e., inhibition of the fast signaling pathways. In addition, there were no changes in the auditory-evoked potential (AEP-N1 component) before and after LAF or LAH treatment, suggesting that neither drug had a central anesthetic effect. Importantly, compared with LAH, LAF was superior in its effects on the magnitudes of gamma-band oscillations and the resting-state spectra, which may be associated with their differences in the octanol/water partition coefficient, degree of dissociation, toxicity, and glycine receptor regulation. Altogether, jointly applying nociceptive laser stimuli and ECoG recordings in rats, we provide solid neural evidence for the analgesic efficacy and antinociceptive mechanisms of derivatives of LA.

Role of the Alternans of Action Potential Duration and Aconitine-Induced Arrhythmias in Isolated Rabbit Hearts

Under conditions of Na+ channel hyperactivation with aconitine, the changes in action potential duration (APD) and the restitution characteristics have not been well defined in the context of aconitine-induced arrhythmogenesis. Optical mapping of voltage using RH237 was performed with eight extracted rabbit hearts that were perfused using the Langendorff system. The characteristics of APD restitution were assessed using the steady-state pacing protocol at baseline and 0.1 microM aconitine concentration. In addition, pseudo-ECG was analyzed at baseline, and with 0.1 and 1.0 microM of aconitine infusion respectively. Triggered activity was not shown in dose of 0.1 microM aconitine but overtly presented in 1.0 microM of aconitine. The slopes of the dynamic APD restitution curves were significantly steeper with 0.1 microM of aconitine than at baseline. With aconitine administration, the cycle length of initiation of APD alternans was significantly longer than at baseline (287.5 +/- 9.6 vs 247.5 +/- 15.0 msec, P = 0.016). The functional reentry following regional conduction block appears with the progression of APD alternans. Ventricular fibrillation is induced reproducibly at pacing cycle length showing a 2:1 conduction block. Low-dose aconitine produces arrhythmogenesis at an increasing restitution slope with APD alternans as well as regional conduction block that proceeds to functional reentry.

Effects of aconitine on Ca2+ oscillation in cultured myocytes of neonatal rats / 华中科技大学学报（医学）（英德文版）

In order to investigate the effects of aconitine on [Ca2+] oscillation patterns in cultured myocytes of neonatal rats, fluorescent Ca2+ indicator Fluo-4 NW and laser scanning confocal microscope (LSCM) were used to detect the real-time changes of [Ca2+] oscillation patterns in the cultured myocytes before and after aconitine (1.0 micromol/L) incubation or antiarrhythmic peptide (AAP) and aconitine co-incubation. The results showed under control conditions, [Ca2+] oscillations were irregular but relatively stable, occasionally accompanied by small calcium sparks. After incubation of the cultures with aconitine, high frequency [Ca2+] oscillations emerged in both nuclear and cytoplasmic regions, whereas typical calcium sparks disappeared and the average [Ca2+] in the cytoplasm of the cardiomyocyte did not change significantly. In AAP-treated cultures, intracellular [Ca2+] oscillation also changed, with periodic frequency, increased amplitudes and prolonged duration of calcium sparks. These patterns were not altered significantly by subsequent aconitine incubation. The basal value of [Ca2+] in nuclear region was higher than that in the cytoplasmic region. In the presence or absence of drugs, the [Ca2+] oscillated synchronously in both the nuclear and cytoplasmic regions of the same cardiomyocyte. It was concluded that although oscillating strenuously at high frequency, the average [Ca2+] in the cytoplasm of cardiomyocyte did not change significantly after aconitine incubation, compared to the controls. The observations indicate that aconitine induces the changes in [Ca2+] oscillation frequency other than the Ca2+ overload.

Association of nicotinic acetylcholine receptors with central respiratory control in isolated brainstem-spinal cord preparation of neonatal rats

Nicotine exposure is a risk factor in several breathing disorders Nicotinic acetylcholine receptors (nAChRs) exist in the ventrolateral medulla, an important site for respiratory control. We examined the effects of nicotinic acetylcholine neurotransmission on central respiratory control by addition of a nAChR agonist or one of various antagonists into superfusion medium in the isolated brainstem-spinal cord from neonatal rats. Ventral C4 neuronal activity was monitored as central respiratory output, and activities of respiratory neurons in the ventrolateral medulla were recorded in whole-cell configuration. RJR-2403 (0.1-10mM), a4b2 nAChR agonist induced dose-dependent increases in respiratory frequency. Non-selective nAChR antagonist mecamylamine (0.1-100mM), a4b2 antagonist dihydro-b-erythroidine (0.1-100mM), a7 antagonist methyllycaconitine (0.1-100mM), and a-bungarotoxin (0.01-10mM) all induced dose-dependent reductions in C4 respiratory rate. We next examined effects of 20mM dihydro-b-erythroidine and 20mM methyllycaconitine on respiratory neurons. Dihydro-b-erythroidine induces hyperpolarization and decreases intraburst firing frequency of inspiratory and preinspiratory neurons. In contrast, methyllycaconitine has no effect on the membrane potential of inspiratory neurons, but does decrease their intraburst firing frequency while inducing hyperpolarization and decreasing intraburst firing frequency in preinspiratory neurons. These findings indicate that a4b2 nAChR is involved in both inspiratory and preinspiratory neurons, whereas a7 nAChR functions only in preinspiratory neurons to modulate C4 respiratory rate.

Antidysrhythmic activity of some nonsteroidal anti inflammatory drugs against barium chloride and aconitine cardiac dysrhythmias in guinea pigs

In our previous work, some nonsteroidal anti-inflammatory drugs demonstrated a remarkable antidysrhythmic activity against ouabain-induced dysrhythmias in urethane-anaesthetized guinea pigs. The present study was undertaken to investigate any possible antidysrhythmic properties of these drugs against other models of experimentally-induced cardiac dysrhythmias achieved by the slow intravenous infusion of barium chloride and aconitine in guina pigs. Two methods have been used for this purpose. In the first method, the drugs were tested for their ability to revert an established barium chloride and aconditine-induced cardiac dysrhythmias. In the second, the tested drugs wee given in advance to visualize if they can protect the animal from the effect of a subsequent dose of the respective dysrhythmogenic agent. Ventricular dysrhythmia induced by barium chloride was reversed by an equivalent dose [20 g/Kg] of Tiaprofenic acid, Pirprofen, Indomethacin and Asprin. On the other hand, the tested drugs, in he same dose level, were unable to revert ventricular dysrhythmias induced by aconitine. Tiaprofenic acid, Indomethacin and Aspirin, in a dose level of 20 mg/Kg, were found to produce a significant protection against dysrhythmias induced by barium chloride and aconitine. Pirprofen, in a dose level of 20 mg/Kg, was unable to protect against bariumn chloride-induced dysrhythmnias whereas, in the same dose lvel, it roduced significant protectioin against ventricular dysrhhythmias induced by aconitine. No correlation was found toexist between the antidysrhythmic effectiveness of these drugs and their effect on the serum and cardiac tissue electrolytes [N2+, K+ and Ca2+]. The relevance of these findings was discussed

Involvement of Central adrenergic mechanisms in the induction of cardiac arrhythmias by aconitine nitrate administered intraventricularly.

Aconitine, 10 mug, administered intraventricularly in cats produced cardiae arrhythmias. Intraventricular administration of phenoxybenzamine, propranolol and practolol abolishes the centrally induced cardiac arrhythmias. Intraventricular reserpinization also abolished these cardiac arrhythmias whereas intraventricular administration of 6-hydroxydopamine and tetrabenazine had no effect. Brain stem noradrenaline probably plays a role in these centrally induced cardiac arrhythmias by aconitine.