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Earlier studies showed that the extract of Nelumbo nucifera Gaertn., an aquatic Indian plant, produced hypoglycaemia and an improvement of glucose tolerance in normal rabbits. Further investigations were undertaken. Chronic administration of plant extracts (test drugs) to normal rats did not produce a sustained fall of fasting blood sugar levels although daily doses caused hypoglycaemia as an acute effect; concurrent glucose tolerance studies showed beneficial effects. In uitro studies with rat hemidiaphragms revealed that test drug treatment of donor animals significantly enhanced the effect of insulin. The improvement of glucose tolerance therefore may also be due to increased peripheral glucose utilization caused by increased sensitivity of skeletal muscles to endogenous insulin. Comparative studies were also carried out in moderately diabetic rabbits using test drugs (equivalent to lo00 mg/kg of crude material) and standard drugs phenformin and tolbutamide (100 mg/kg each). The test drugs showed acute and chronic effects in suppressing hyperglycaemia, but were less potent than standard drugs. However, test drugs significantly improved glucose tolerance in these animals. With severely diabetic rabbits, these drugs proved to be ineffective even at four-fold higher doses. Toxicity studies in normal rats did not show any deleterious effect on kidney, heart or liver during an 8-week study period.

Nebmbo nucifera Gaertn, an Indian aquatic herb, has been studied for its potential utility in the treatment of Diabetes mellitus. The powdered sun-dried flowers (test drug), as well as the aqueous and alcoholic extracts of these, produced significant hypoglycaemia in fasting normal albino rabbits. There was no significant difference in the activities of lOOOmg/kg of the test drug and equivalent amounts of the extracts; the effect was approximately 50% of that produced by 250mg/kg of tolbutamide. Glucose tolerance studies with normal rabbits showed that oral doses of both extracts, equivalent to 1OOO mglkg of the test drug, produced significant depression of the peak rise in fasting blood sugar after glucose load; the effects of both extracts were comparable to that produced by 250 mg/kg of tolbutamide. A study of glucose tolerance curves shows that the duration of hyperglycaemia was also notably reduced compared with the controls. In normal rabbits, the extracts, in doses mentioned above, significantly depressed hyperglycaemia induced by injection of adrenaline hydrochloride 0.5 mglkg S.C. Since the test drug and extracts were found to be effective in studies of the above parameters in normal animals, further chronic studies on normal and diabetic animals are planned.

1 Clonidine (1.25, 2.5 and 5.0 pugkg -) was studied for its effect on the cardiac arrhythmias and lethality induced by slow intravenous infusion of ouabain in guinea-pigs. 2 Clonidine produced significant delays in the onset of the arrhythmic stages and lethality. However, clonidine did not offer any such protection in reserpinised guinea-pigs, whereas its effects were unaltered in atropinized guinea-pigs.3 Idazoxan (l00.ugkg-1, i.v.) abolished the antiarrhythmic effect of clonidine whereas corynanthine(1 mg kg-1, i.v.) had no such effect. 4 Clonidine inhibited the rate of the ouabain-induced rise in blood pressure and the peak pressor response.5 In isolated paced left atria of the guinea-pig, clonidine (3.75 x 1O-4M) did not offer any protection against rapid and/or irregular extrasystolic contractions induced by ouabain. 6 It is concluded that the antiarrhythmic effect of clonidine is due to its effects on the indirect neural components of digitalis toxicity mediated by the stimulation of a2-adrenoceptors, without any direct antiarrhythmic effect on the myocardium.