| Research Abstract |
In this study we used capsaicin, piperine, and diallyl disulfide as pungent agents extracted from spices. We did next three kinds of experiments to clarify unknown direct or indirect physiological effects of these agents, using a whole body or isolated preparation of heart and uterus of rats and guinea pigs.
Study 1 : Effects of capsaicin on isolated ventricular papillary muscle from rat and guinea pig. Capsaicin showed dual effects on the contractile tension of rat papillary muscle. That is, the low concentration (0.1muM) increased the amplitude of tension, but the high concentration (*10muM) decreased it. The increase in the tension at low concentration never happened in the presence of beta-blocker, propranolol. Effective concentration 50% (EC_<50>) of capsaicin in the amplitude of tension at 1Hz was around 10muM.On the other hand, all concentrations used decreased the tension of rat papillary muscle in a concentration-dependent manner. EC_<50> at 1Hz was around 0.1muM,showing a high
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sensitivity to capsaicin in rat. In the same animal, we investigated the effects of capsaicin on the rested-state contraction (RSC) to know its electrophysiological actions on intracellular Ca store, and compared the findings with effects of caffeine and ryanodine, because RSC is believed to be mostly dependent on extra Ca released from the Ca store. As a result, capsaicin had no direct effect on the Ca store. Our data suggest that capsaicin-induced negative inotropic action is largely due to a block of Ca channels, as we have reported previously, using isolated single ventricular cells (Jpn.J.Physiol.43 [Suppl.2] : s155,1993).
Study 2 : Comparison of contractile effects between capsaicin, piperine and diallyl disulfide in isolated rat myometrium
All three agents, capsaicin, piperine and diallyl disulfide repressed the amplitude and frequency of spontaneous contraction of isolated rat myometrium. Diallyl disulfide was the most effective in inhibiting the amplitude of the tension, followed by piperine and capsaicin in that order. EC_<50> 's in inhibiting the amplitude were 20muM in diallyl disulfide, 50muM in piperine and 0.1mM in capsaicin. EC_<50> 's in inhibiting the frequency were 20muM in diallyl disulfide and 0.1mM in capsaicin. Piperine showed no or little effect on the frequency. It is suggested that these agents decrease the tension, via a block of Ca channels.
Study 3 : Effects of capsaicin, piperine and diallyl disulfide on the respiration and periferal blood flow of diabetic and non-diabetic rats
In olfactory experiments, three agents increased the number of respiration per minute and periferal blood flow in the abdomen of spontaneous diabetic rats, while they had no or little effect in non-diabetic ones. In taste experiments, three agents produced a little increase in the respiration of non-diabetic rats, but these produced a decrease in that of diabetics. The blood flow in diabetic rats was decreased by three agents, but that in non-diabetic rats was not effected. To elucidate these experimental facts, we need further experiments. Less
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