Thesis (M.Sc.)--Chulalongkorn University, 1984

A primary investigation of the pharmacological action of 3α-dihydrocadambine, indole glycosidic alkaloid (ALKALOID) from the leaves of Anthocephalus chinensis A. Rich. have been studied in anaesthetized rats, whilst iso¬lated right and left rat atrial strips were also studied. An intravenous infusion of ALKALOID 0.4, 0.8, 1.6 and 3.2 mg/kg B.W. caused dose-dependent sustained hypotensive effect in both systolic and diastolic blood pressures with accompanied by bi-phasic initial reduction followed by a small increase in heart rate. Prior administration of propranolol 1 and 2 mg/kg B.W. or mepyramine 10 mg/kg B.W. plus cimetidine 20 mg/kg B.W. did not indicate an inhibi¬tion on hypotensive effect of ALKALOID. Only atropine 0.3 mg/kg B.W. showed a partial reduction in hypotensive effect of ALKALOID at all doses significantly, while hexa¬methonium 3.5 mg/kg B.W. reduced slightly. Furthermore, the hypertensive effect of tyramine was not abolished by ALKALOID. The ALKALOID produced dose-dependent reduction in isolated rat atrial rate but slightly exhibited depression effect on left atrial isometric tension. In conclusion, there are more than one mechanisms of ALKALOID which induced a sustained reduction in blood pressure: mediate via cholinergic receptors or act somehow on central nervous system, whilst a direct action on vas¬cular resistance may be suggested. However, more studies are required to illuminate the detail mechanism of this alkaloid on cardiovascular and other systems.