Effects of oblongine chloride, an alkaloid from Leontice leontopetalum on guinea-pig isolated smooth muscle and heart

Cardiovascular effects of oblongine chloride, an alkaloid from Leontice leontopetalum, in the anaesthetized guinea‐pig

“…The observation that propranolol did not block oblongine-induced hypotension is consistent with our previous conclusion (Abdalla et al, 1993) that oblongine chloride does not interact with P-adrenergic receptors, and indicates that the hypotensive effect of oblongine chloride is not due to the stimulation of padrenergic receptors of the vascular smooth muscle. Furthermore, the hypotensive effect of oblongine chloride is unlikely to be due to a decrease in the cardiac output since: (a) the hypotension was associated with an increase in heart rate rather than a decrease, (b) oblongine chloride was found to cause an increase in the contractility of the guinea-pig isolated atrium and the isolated perfused heart except when used in high concentrations with the latter preparation where it caused an inhibition (Abdalla et al, 1993). and (c) oblongine chloride caused an increase in blood flow suggesting an increase rather than a decrease in cardiac output.…”

“…The increase in heart rate observed with intravenous doses of oblongine chloride may represent a reflex tachycardia in response to oblongine-induced hypotension since it was found that oblongine chloride did not increase the beating rate of the isolated spontaneously beating atrium and indeed, in high concentrations, it caused an inhibition of the beating rate of the isolated perfused heart (Abdalla et al, 1993). The observation that propranolol did not block oblongine-induced hypotension is consistent with our previous conclusion (Abdalla et al, 1993) that oblongine chloride does not interact with P-adrenergic receptors, and indicates that the hypotensive effect of oblongine chloride is not due to the stimulation of padrenergic receptors of the vascular smooth muscle. Furthermore, the hypotensive effect of oblongine chloride is unlikely to be due to a decrease in the cardiac output since: (a) the hypotension was associated with an increase in heart rate rather than a decrease, (b) oblongine chloride was found to cause an increase in the contractility of the guinea-pig isolated atrium and the isolated perfused heart except when used in high concentrations with the latter preparation where it caused an inhibition (Abdalla et al, 1993).…”

“…The present study demonstrates the effects of oblongine chloride on blood pressure, heart rate and blood flow of anaesthetized guinea-pigs. The effects of oblongine chloride on blood pressure are consistent with those observed in a previous study which demonstrated that the compound caused relaxation of epinephrineprecontracted pulmonary artery of the guinea-pig (Abdalla et al, 1993). If such relaxation prevails in other blood vessels, it would lead to a reduction in the peripheral resistance which may explain in part the hypotensive effect of oblongine chloride observed in the present experiments.…”

“…If such relaxation prevails in other blood vessels, it would lead to a reduction in the peripheral resistance which may explain in part the hypotensive effect of oblongine chloride observed in the present experiments. The increase in heart rate observed with intravenous doses of oblongine chloride may represent a reflex tachycardia in response to oblongine-induced hypotension since it was found that oblongine chloride did not increase the beating rate of the isolated spontaneously beating atrium and indeed, in high concentrations, it caused an inhibition of the beating rate of the isolated perfused heart (Abdalla et al, 1993). The observation that propranolol did not block oblongine-induced hypotension is consistent with our previous conclusion (Abdalla et al, 1993) that oblongine chloride does not interact with P-adrenergic receptors, and indicates that the hypotensive effect of oblongine chloride is not due to the stimulation of padrenergic receptors of the vascular smooth muscle.…”

“…We have studied the effects of oblongine chloride on guinea-pig isolated smooth muscle and heart and found that it has a potent relaxant effect on smooth muscle and a positive inotropic effect on the isolated atria and perfused heart. Our study suggested that the effects of oblongine chloride may be mediated in part by interaction with the purinergic receptors and in part by interference with arachidonic acid metabolism but not by stimulation of padrenergic receptors in the above tissues (Abdalla et al, 1993). We have also evaluated some of the in oiuo effects of oblongine chloride.…”