Showing papers on "Arecoline published in 2000"

Muscarinic Cholinergic Modulation of Prepulse Inhibition of the Acoustic Startle Reflex

Abstract: The purpose of the present study was to determine the effects of muscarinic cholinergic receptor antagonists and agonists on prepulse inhibition (PPI) of the acoustic startle reflex in rats. The muscarinic receptor antagonist scopolamine (0.03–1.0 mg/kg) produced a significant dose-dependent decrease in PPI without affecting startle amplitude. In contrast, N -methyl scopolamine, the quaternary analog of scopolamine, had no effect on PPI, indicating that scopolamine disrupted PPI through a central cholinergic mechanism. Two other muscarinic receptor antagonists, trihexyphenidyl (0.3–10 mg/kg) and benztropine (0.03–10 mg/kg), produced significant decreases in PPI similar to scopolamine. On the other hand, the muscarinic receptor antagonists dicyclomine (0.03–10 mg/kg) and biperiden (0.03–10 mg/kg) had no effect on PPI but significantly decreased startle amplitude. Mecamylamine (0.1–10 mg/kg), a nicotinic receptor antagonist, also had no effect on PPI. Administered alone, the muscarinic receptor agonists pilocarpine (0.03–10 mg/kg), oxotremorine (0.01–0.3 mg/kg), RS-86 (0.1–3.0 mg/kg), and arecoline (0.3–10 mg/kg), as well as the cholinesterase inhibitors physostigmine (0.01–0.3 mg/kg) and tacrine (0.03–10 mg/kg), had no effect on PPI, but each produced significant decreases in startle amplitude at the highest doses tested. In addition, the disruption of PPI by scopolamine was reversed in a dose-dependent manner by the muscarinic receptor agonist oxotremorine. The present findings demonstrate that the muscarinic cholinergic system plays an important role in the normal mechanisms of PPI.

Behavioral and biochemical studies of dichloromethane fraction from the Areca catechu nut.

Abstract: The dichloromethane fraction from Areca catechu was found to inhibit monoamine oxidase type A isolated from the rat brain with an IC50 of 665 +/- 65.1 microg/ml. Studies with pharmacological models of depression, i.e., forced swim and tail-suspension tests, indicated that it caused significant reduction in the immobility time similar to that of moclobemide (a selective inhibitor of MAO-A) without causing a significant change in motor performance. Alkaloids such as arecaidine, arecoline, and a few other constituents, reported to be present in Areca catechu were also tested, but none of them were found to inhibit MAO. Present study suggests that the dichloromethane fraction from A. catechu possesses antidepressant property via MAO-A inhibition.

Effects of areca nut extracts on the functions of human neutrophils in vitro

Abstract: Aqueous extracts of ripe areca nut without husk (ripe ANE) and fresh and tender areca nut with husk (tender ANE) were examined for their effects on the defensive functions of human neutrophils. Exposure of peripheral blood neutrophils to ripe ANE and tender ANE inhibited their bactericidal activity against oral pathogens, including Actinobacillus actinomycetemcomitans and Streptococcus mutans, in a dose-dependent manner. At the concentrations tested, ripe and tender ANEs did not significantly affect the viability of neutrophils as verified by their ability to exclude trypan blue dye. However, both ANEs inhibited the production of bactericidal superoxide anion by neutrophils as measured by cytochrome c reduction. Moreover, the ripe ANE inhibited neutrophils more effectively than did tender ANE. Arecoline, a major alkaloid of areca nut, only exhibited an inhibitory effect on the functions of neutrophils when high concentrations were used. Therefore, arecoline could not be used to explain the inhibitory effects observed for ANEs. In conclusion, our results demonstrated that ripe and tender ANEs reduced the antibacterial activity and the superoxide anion production of neutrophils. This effect may contribute to a less efficient elimination of bacteria from the periodontal environment. Inhibition of the antimicrobial functions of neutrophils may alter the microbial ecology of the oral cavity, and this may be one possible mechanism by which areca nut compromises the oral health of users of areca nut products.

Arecoline excites rat locus coeruleus neurons by activating the M2-muscarinic receptor.

Abstract: The action of arecoline on rat locus coeruleus neurons was studied by intracellular recording from the in vitro brain slice preparation. Superfusion of arecoline (0.1-100 microM) caused two dose-related effects, an increased firing rate and, in neurons previously hyperpolarized to a constant potential by passing a steady hyperpolarizing current across the membrane, depolarization. Both effects were associated with a reduction in membrane input resistance. Moreover, the arecoline-induced excitatory effects were antagonized by the muscarinic receptor antagonist, atropine, but not by the nicotinic receptor antagonist, hexamethonium. Methoctramine, a selective M2-muscarinic receptor antagonist, was also effective in reversing the arecoline-induced effects, with a dissociation equilibrium constant of 14.2+/-1.2 nM (n=6). These results therefore suggest that arecoline exerts its excitatory actions by binding to M2-muscarinic receptors on the cell membrane of neurons of the locus coeruleus.

Interleukin-8 secretion by cultured oral epidermoid carcinoma cells induced with nicotine and/or arecoline treatments.

Abstract: Interleukin-8 (IL-8) is one of the multifunctional cytokines that can play a role on immune and inflammatory activities. Other in vitro observations indicated that IL-8 is a growth factor for keratinocytes. However, as the role of IL-8 in oral cancer cells is unclear, this study is thus designed to examine IL-8 secretion in cultured oral epidermoid carcinoma KB CCL17 cells treated with nicotine and/or arecoline. The cultures were treated with nicotine (1 or 100 microM) and arecoline (1 or 100 microM), alone or both, for 72 hrs. Enzyme-linked immunosorbent assay (ELISA) was used to examine IL-8 concentrations in culture supernatants. A repeated measure analysis of variance was used to identify differences among the treatments. Nicotine and arecoline, single or combined treatment, increased IL-8 secretion in KB CCL17 cells. When monoclonal 1 microgram/ml of antibody was added against IL-1 alpha or IL-1 beta in the treatment, IL-8 concentration significantly decreased compared with the non-added one. Exposure of cells to antibody against IL-1 alpha or IL-1 beta showed no significant increase in cell growth as compared with the control (medium alone). However, incubation of cells for 72 hrs in the presence of nicotine and/or arecoline treatments and antibody against IL-1 alpha or IL-1 beta significantly increased cell growth as compared with the antibody free one. It was concluded that IL-8 secretion by KB CCL17 cells may be partially mediated by IL-1 which could inhibit the KB CCL17 cell growth. Thus, IL-8 may be a vital participant in the cascade of interacting cytokines during smoking and areca quid chewing, inducing inflammation in oral cancer.

Heart rate responses to a muscarinic agonist in rats with experimentally induced acute and subacute chagasic myocarditis.

Abstract: We administered arecoline to rats, with experimentally induced chagasic myocarditis, in order to study the sinus node sensitivity to a muscarinic agonist. Sixteen month old rats were inoculated with 200,000 T. cruzi parasites ("Y" strain). Between days 18 and 21 (acute stage), 8 infected rats and 8 age-matched controls received intravenous arecoline as a bolus injection at the following doses: 5. 0, 10.0, 20.0, 40.0, and 80.0 microg/kg. Heart rate was recorded before, during and after each dose of arecoline. The remaining 8 infected animals and 8 controls were subjected to the same experimental procedure during the subacute stage, i.e., days 60 to 70 after inoculation. The baseline heart rate, of the animals studied during the acute stage (349 +/- 68 bpm, mean +/- SD), was higher than that of the controls (250 +/- 50 bpm, p < 0.005). The heart rate changes were expressed as percentage changes over baseline values. A dose-response curve was constructed for each group of animals. Log scales were used to plot the systematically doubled doses of arecoline and the induced-heart rate changes. The slope of the regression line for the acutely infected animals (r = - 0.99, b =1.78) was not different from that for the control animals (r = - 0.97, b = 1.61). The infected animals studied during the subacute stage (r = - 0.99, b = 1.81) were also not different from the age-matched controls (r = - 0.99, b = 1.26, NS). Consequently, our results show no pharmacological evidence of postjunctional hypersensitivity to the muscarinic agonist arecoline. Therefore, these results indirectly suggest that the postganglionic parasympathetic innervation, of the sinus node of rats with autopsy proved chagasic myocarditis, is not irreversibly damaged by Trypanosoma cruzi.

[Studies on the effect-increasing components for molluscacides in nut of Areca catech L].

Abstract: OBJECTIVE To investigate the effect-increasing action of Areca catech for molluscacide. METHOD Experiments were conducted on the effect-increasing components isolated from the dry nut of A. catech. RESULT Arecoline has been proved the most effect-increasing component. CONCLUSION When used with SPA arecoline could reduce markedly the doses of the two agents.

Synthesis of (.+-.)-Isofagomine and Its Stereoisomers from Arecoline.

Abstract: (±)-Isofagomine (1) and all its stereoisomers were prepared in a short synthesis from arecoline. The double bond of arecoline was isomerised to be no longer conjugated to the carboxy, and the ester reduced to (hydroxymethyl)tetrahydropyridine 5 which after dihydroxylation of the alkene, separation and N-demethylation gave 1 and its isomers.