RESUMO
The neuromuscular blocking properties of an alkaloidal extract from the root of Inula royleana have been investigated in vitro using a combination of mechanical and electrophysiological approaches. Neurogenic twitches of the frog sartorius were profoundly inhibited by concentrations of the extract > or = 20 micrograms/ml, being reduced to 50% of control amplitude in approximately 90 s at a concentration of > or = 20 micrograms/ml. They were partially reversed by neostigmine (6 micrograms/ml), and by prolonged washout of the extract. Muscle surface action potentials, recorded with extracellular electrodes, also declined rapidly in amplitude in the presence of the extract. Direct muscle stimulation during inhibition by the extract elicited contractions and action potentials whose magnitudes were similar to control responses. Resting membrane potentials, and the intracellular input impedance of the skeletal muscle cells, were not significantly changed by the alkaloids. These results indicate that the extract has significant neuromuscular blocking activity of a partially or slowly reversible nature. The block appears to be exerted at the postjunctional end-plate nicotine receptors, thus offering promise for the identification of novel cholinergic receptor antagonist(s).
Assuntos
Potenciais de Ação/efeitos dos fármacos , Alcaloides/farmacologia , Animais , Estimulação Elétrica , Eletrofisiologia , Índia , Inula , Potenciais da Membrana/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Neostigmina/farmacologia , Bloqueadores Neuromusculares/farmacologia , Parassimpatomiméticos/farmacologia , Técnicas de Patch-Clamp , Extratos Vegetais/farmacologia , Plantas Medicinais/química , Rana pipiens , Nervo Isquiático/efeitos dos fármacosRESUMO
Synthetic analogues of a monoterpenic fragment of aplasmomycin were tested for their antimalarial activity in Plasmodium falciparum culture in vitro. The antimalarial activities of these agents were evaluated in chloroquine sensitive strains. Parasite growth was inhibited in a dose dependent manner in the presence of the synthetic compounds (3-9).