This study was aimed to explore underlying mechanism(s) of cardiovascular effects of piperine. Intravenous administration of piperine caused a dose-dependent (1 to 10 mg/kg) decrease in mean arterial pressure (MAP) in normotensive anesthetized rats; the next higher dose (30 mg/kg) did not cause any further change in MAP. The fall in blood pressure (BP) was followed by small increase in MAP after each dose. In Langendorrf's rabbit heart preparation, piperine caused partial inhibition and verapamil caused complete inhibition of force and rate of ventricular contractions and coronary flow. In rabbit aortic rings, piperine inhibited high K+ (80 mM) precontractions and partially inhibited phenylephrine (PE), suggesting Ca2+ channel blockade (CCB), which was further confirmed when pretreatment of tissues with piperine caused rightward shift in Ca2+ concentration-response curves, similar to verapamil. In Ca2+-free medium, piperine (1 to 30 microM) exhibited vasoconstrictor effect. In rat aorta, piperine demonstrated endothelium-independent vasodilator effect and was more potent against high K+ precontractions than PE. In bovine coronary artery preparations, piperine inhibited high K+ precontractions completely. These data indicate that piperine possesses a blood pressure-lowering effect mediated possibly through CCB, while consistent decrease in BP was restricted by associated vasoconstrictor effect. Additionally, species selectivity exists in the CCB effect of piperine.

AbstrtactBackground: This study was aimed to find out the central and peripheral analgesic activity of hydro methanolic extract of aerial parts of Onosma bracteatum. Material and methods: The central and peripheral analgesic activity is evaluated by tail flick test and acetic acid induced writhing test at the doses of 50, 100, 250 and 500mg/kg body weight respectively in animal models. Results: The results obtained from Tail flick test revealed that O. bracteatum possesses potent analgesic effects by inducing significant increase in latency period in dose dependent manner at all doses at 1, 2 and 3 hours post feeding respectively. The maximum effect was observed at a dose of 500mg/kg i.e. 258.9% (p<0.05) at 3hrs post feeding. Diclofenac sodium (5mg/kg body weight) run as standard also increased the latency period continuously and highest activity was noted at 3hr i.e. 284.5% (p<0.05). Acetic acid induced writhing test also showed significant activity in a similar manner by O. bracteatum i.e 54% (p<0.05) at 500mg/kg while standard drug Diclofenic sodium (5mg/kg body weight) showed 45.9% (p<0.05) activity. Conclusion: It is concluded that O. bracteatum possesses significant central and peripheral analgesic activity in animal model.

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Objective: To investigate and determine the antidiarrhoeal and spasmolytic potential of fruit of Aegle marmelos is due to CCBs compounds and not tannic acid. Materials and methods: The extract of ripe and dry fruit of A. marmelos (Am.Cr) was prepared in methanol: water (70:30). The antidiarrhoeal activities of the extract, loperamide and tannic acid were studied in vivo; in castor oil induced diarrhoeal model in mice whereas spasmolytic effect was studied in vitro; in isolated mice ileum. Calcium channel blocking (CCB) activity was investigated after preincubation of mice ileum by Am. Cr or loperamide and subsequent adding of K + 80 mM. Results: Am. Cr inhibited castor oil-induced diarrhoea: onset of diarrhoea, total no. of faeces, and total no. of wet faeces dose-dependently, the dose of 800 mg/mL was found statistically significant, total weight of feces and total weight of wet faeces were also inhibited. Concentration-dependent inhibition of spontaneous contraction and contractile effect of K + 80 mM after pre-incubation by Am. Cr were confirmed in isolated mice ileum. The results of Am. Cr are comparable with Loperamide. Tannic acid produced neither antidiarrhoeal effect nor exhibited CCB activity, however relaxant effect was observed in isolated mice ileum. Conclusion: The antidiarrhoeal and spasmolytic effects of Am.Cr may be mediated through compounds which posses CCB effect. Tannic acid exhibited relaxant effect only which is not sufficient evidence scientifically to classify as antidiarrhoeal.