aconitine and Bradycardia

Nicotine improves endotoxic manifestations of hypotension and cardiac autonomic dysfunction in rats. Here, we test the hypothesis that brainstem antiinflammatory pathways of α7/α4β2 nicotinic acetylcholine receptors (nAChRs) modulate endotoxic cardiovascular derangements. Pharmacologic and molecular studies were performed to determine the influence of nicotine or selective α7/α4β2-nAChR ligands on cardiovascular derangements and brainstem neuroinflammation caused by endotoxemia in conscious rats. The i.v. administration of nicotine (50 μg/kg) abolished the lipopolysaccharide (LPS, 10 mg/kg i.v.)-evoked: (i) falls in blood pressure and spectral measure of cardiac sympathovagal balance (ratio of the low-frequency to high-frequency power, LF/HF), (ii) elevations in immunohistochemical protein expressions of NFκB and α4β2-nAChR in medullary neurons of the nucleus tractus solitarius (NTS) and rostral ventrolateral medulla (RVLM), and (iii) decreases in medullary α7-nAChR protein expression. These favorable nicotine influences were replicated in rats treated intracisternally (i.c.) with PHA-543613 (selective α7-nAChR agonist) or 5-iodo-A-85380 (5IA, selective α4β2-nAChRs agonist). Measurement of arterial baroreflex activity by the vasoactive method revealed that nicotine, PHA, or 5IA reversed the LPS depression of reflex bradycardic, but not tachycardic, activity. Moreover, the counteraction by nicotine of LPS hypotension was mostly inhibited after treatment with i.c. methyllycaconitine (MLA, α7-nAChR antagonist) in contrast to a smaller effect for dihydro-β-erythroidine (DHβE, α4β2-nAChR antagonist), whereas the associated increases in LF/HF ratio remained unaltered. The data signifies the importance of brainstem α7, and to a lesser extent α4β2, receptors in the nicotine counteraction of detrimental cardiovascular and neuroinflammatory consequences of endotoxemia.

Topics: Aconitine; alpha7 Nicotinic Acetylcholine Receptor; Animals; Azetidines; Bradycardia; Bridged Bicyclo Compounds, Heterocyclic; Cholinergic Fibers; Dihydro-beta-Erythroidine; Endotoxemia; Hypotension; Infusions, Intraventricular; Lipopolysaccharides; Male; Medulla Oblongata; Neural Pathways; Neurogenic Inflammation; NF-kappa B; Nicotine; Pyridines; Quinuclidines; Rats; Receptors, Nicotinic; Signal Transduction; Solitary Nucleus; Tachycardia

Antiarrhythmic therapy of patients with disturbed automatism of the sinus node and impaired atrioventricular conductance may be complicated by hemodynamically significant bradycardias and contraindications for implantation of a cardiac electrical stimulator This study aimed at estimating effect of antiarrhythmic therapy with allapinin on the function of sinus and atrioventricular nodes. It included 20 patients (mean age 37.5+-2.3 years) with disturbed cardiac rhythm and sinus node dysfunction treated with allapinin (37.5 - 50 mg/d per os). This therapy had well apparent antiarrhythmic effect manifest as improvement of supraventricular and ventricular ectopic activities in the absence of negative influence on the function of sinus and atrioventricular nodes.

Topics: Aconitine; Adult; Anti-Arrhythmia Agents; Bradycardia; Depression, Chemical; Dose-Response Relationship, Drug; Drug Monitoring; Electrocardiography, Ambulatory; Electrophysiologic Techniques, Cardiac; Female; Heart Conduction System; Heart Rate; Humans; Male; Sick Sinus Syndrome; Tachycardia, Paroxysmal; Treatment Outcome; Ventricular Premature Complexes

Nicotinic cholinergic receptors mediate autonomic transmission at ganglia. However, whether different subtypes of nicotinic cholinergic receptors expressed in autonomic ganglia elicit distinct roles in mediating sympathetic and parasympathetic regulations remain to be defined. In this study, we observed that different subtypes of nicotinic receptors were responsible for the sympathetic and parasympathetic cardiovascular responses. In urethane anesthetized mice, intravenous injection with cytisine, a non-selective nicotinic agonist, induced a brief but pronounced decrease in heart rate, followed by increases in heart rate and arterial blood pressure. The bradycardic response was blocked by atropine, and the pressor response was blocked by prazosin, confirming that these responses were parasympathetic and sympathetic activities, respectively. Hexamethonium, a ganglionic blocker, blocked both sympathetic and parasympathetic responses. Pretreatment with methyllycaconitine citrate, a selective alpha7 nicotinic receptor antagonist, significantly attenuated cytisine-induced sympathetic response with little effect on the parasympathetic response. In contrast, pretreatment with dihydro-beta-erythroidine hydrobromide, a selective alpha4beta2 nicotinic receptor antagonist, blocked cytisine-induced parasympathetic response but not the sympathetic response. Pretreatment with dihydro-beta-erythroidine hydrobromide also blocked baroreflex associated parasympathetic bradycardic response. Moreover, treatment with nicotine induced a bradycardic response without a significant pressor response, which was also attenuated by dihydro-beta-erythroidine hydrobromide. Collectively, these data suggest that different nicotinic receptors play distinct roles in sympathetic and parasympathetic ganglia. Specifically, activations of alpha7 and alpha4beta2 nicotinic receptors are involved in cytisine-induced cardiovascular sympathetic and parasympathetic responses, respectively.

Topics: Aconitine; Adrenergic alpha-Antagonists; Alkaloids; Analysis of Variance; Animals; Atropine; Azocines; Blood Pressure; Bradycardia; Cardiovascular Physiological Phenomena; Dihydro-beta-Erythroidine; Heart Rate; Hexamethonium; Male; Mice; Muscarinic Antagonists; Nicotinic Agonists; Nicotinic Antagonists; Prazosin; Quinolizines; Receptors, Nicotinic

Recently we demonstrated that centrally administrated melittin, a phospholipase A(2) (PLA(2)) activator, caused pressor and bradycardic effect in the normotensive conscious rats. In the current study we aimed to determine the mediation of central cholinergic system in the pressor and bradycardic effect of centrally administrated melittin. Studies were performed in normotensive male Sprague-Dawley rats. 1.5, 3.0 or 6.0microg/5.0microl doses of melittin were injected intracerebroventricularly (i.c.v.). Melittin caused dose- and time-dependent increases in mean arterial pressure (MAP) and decrease in heart rate (HR). In order to test the mediation of central cholinergic system on the pressor and bradycardic effect of melittin, the rats were pretreated with mecamylamine (50microg; i.c.v.), cholinergic nonselective nicotinic receptor antagonist, atropine sulfate (10microg; i.c.v.), a cholinergic nonselective muscarinic receptor antagonist, hemicholinium-3 (20microg; i.c.v.), a high affinity neuronal choline uptake inhibitor, methyllycaconitine (10 and 25microg; i.c.v.) or alpha-bungarotoxin (10 and 25microg; i.c.v.), selective antagonists of alpha-7 subtype nicotinic acetylcholine receptors (alpha7nAChRs), 15min prior to melittin (3.0microg) injection. Pretreatment with mecamylamine, hemicholinium-3, methyllycaconitine or alpha-bungarotoxin partially attenuated the pressor and bradicardia effect of elicited by melittin in the normotensive conscious rats whereas pretreatment with atropine had no effect. In conclusion, i.c.v. administration of melittin increases MAP and decreases HR in conscious rats. The activation of central nicotinic cholinergic receptors, predominantly alpha7nAChRs, partially acts as a mediator in the pressor responses to i.c.v. injection of melittin in the normotensive conscious rats. Moreover, decreased uptake of choline to the cholinergic terminals may consider that melittin activates central choline and acetylcholine release, as well.

Topics: Aconitine; Animals; Atropine; Blood Pressure; Bradycardia; Brain; Bungarotoxins; Cholinergic Agents; Cholinergic Fibers; Consciousness; Drug Interactions; Heart Rate; Hemicholinium 3; Injections, Intraventricular; Male; Mecamylamine; Melitten; Nicotinic Antagonists; Parasympatholytics; Phospholipases A; Rats; Rats, Sprague-Dawley

We define the potential sources, clinical manifestations, and treatment of aconitine poisoning.. The database of the National Poison Center in Taiwan was retrospectively searched for the diagnosis of aconitine poisoning for 1990 to 1999. The reasons for taking the aconite roots, the clinical features, management, and possible predisposing factors were noted.. A total of 17 cases occurred and consisted of 9 men and 8 women aged 30 to 70 years. Thirteen patients ingested aconite roots as treatment for rheumatism and wounds. Two patients volunteered to test the effects of aconite roots in a drug study. Two patients accidentally ingested the aconite roots. After a latent period of 10 to 90 minutes, patients developed a combination of neurologic (n=17), cardiovascular (n=14), gastrointestinal (n=9), and other (n=5) features typical of aconitine poisoning. Four patients developed ventricular tachycardia. All patients received supportive treatment. Patients with ventricular tachycardia were also treated with charcoal hemoperfusion. All patients made a complete recovery.. Life-threatening ventricular tachycardia can occur after the consumption of aconite roots. The risk is higher with inadequately processed aconite roots, large doses, or tincture preparations. With increasing popularity of herbal medicines, herb-induced aconitine poisoning may also be seen in Western countries.

Topics: Aconitine; Aconitum; Adult; Aged; Bradycardia; Electrocardiography; Female; Humans; Male; Middle Aged; Phytotherapy; Retrospective Studies; Rheumatic Diseases; Tachycardia, Ventricular; Ventricular Premature Complexes; Wounds and Injuries

Aconitine administered intraperitoneally (i.p.) produces bradycardia mainly by a central muscarinic action. The involvement of hypothalamic regions in the occurrence of aconitine-induced bradycardia was investigated in hypothalamus-lesioned mice. The lesions were made by passing a direct current (1.5 mA, 13 s) through a monopolar electrode. The aconitine (30 micrograms/kg, i.p.)-induced bradycardia was prevented by bilateral lesions of either the whole hypothalamus, except for the lateral hypothalamus area, or the anterior hypothalamus (AH). The bradycardia was not prevented by bilateral lesions of the ventromedial, the paraventricular, the posterior or the lateral hypothalamus regions. Bupivacaine, but not atropine (1 microgram, administered into the intact AH) prevented aconitine-induced bradycardia in mice with a contralaterally lesioned AH. Aconitine (0.8 microgram) directly administered into the unilateral AH in intact mice caused a late phase and lesser extent of bradycardia. These results suggest that a transmission pathway including the AH contributes to the aconitine-induced bradycardia but does not involve the activation of muscarinic receptors in the AH.

Topics: Aconitine; Anesthetics, Local; Animals; Atropine; Blood Pressure; Bradycardia; Bupivacaine; Cerebral Cortex; Hypothalamus, Anterior; In Vitro Techniques; Male; Mice; Mice, Inbred Strains; Muscarinic Antagonists; Neural Pathways; Pulse; Synaptic Transmission

Topics: Aconitine; Animals; Anti-Arrhythmia Agents; Atropine; Bradycardia; Cats; Dose-Response Relationship, Drug; Heart Rate; Perfusion; Tachycardia; Time Factors; Tropanes