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KMID : 0620719990050010025
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Natural Product Sciences
1999 Volume.5 No. 1 p.25 ~ p.32
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Studies on the Cardiovascular Effects of Ambrein Pretreatment in Rats
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Raza, M .
Taha, S . A ./El-Khawad, I . E .
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Abstract
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The pharmacological actions of ambrein were investigated alone. or in combination as a pretreatment with agonists (adrenaline, noradrenaline, acetylcholine, histamine, nicotine). antagonists (atropine, atenolol) and calcium channel blocker (verapamil) in vivo in anaesthetized SWR rats using blood pressure, heart rate and myocardial contractility as parameters. Ambrein in the dose range of 50-200 ㎎/㎏ to the normotensive anaesthetized rats demonstrated negative chronotropic effect and increased the myocardial contractility significantly. At the mid dose (100 ㎎/㎏) this increase in contractile force was 36% and 44% above the normal at 30 min and 60 min intervals post-treatment, respectively. Both of the lower and high doses (50 ㎎/㎏ and 200 ㎎/㎏) had similar effects. Furthermore, this contractile response was dose related. Also, this compound produced a considerable increase in myocardial contractility when used as a pretreatment with some agonists and antagonists. The results on blood pressure did not show a considerable change when ambrein was used alone. However, ambrein pretreatment at the dose of 100 ㎎/㎏ did not block the effects of adrenaline, noradrenaline, isoprenaline and acetylcholine on heart rate and blood pressure. On the other hand, this pretreatment attenuated the sympathoadrenal effects of nicotine significantly. Chronotropic and blood pressure changes produced by histamine were also inhibited by ambrein pretreatment. This pretreannent significantly reversed the effects of atenolol but failed to demonstrate any change in the negative chronotropic, inotropic and hypotensive responses induced by varapamil. It is concluded that ambrein induced nonselective dose dependent antagonism of the effects of some agonists and antagonists require contribution of some neuromediators. However, the positive inotropic effects of ambrein possibly involve the enhancement of slow Ca channels and/or activation of β-adrenergic receptors in the heart. At this moment it is difficult to explain the exact mode of action of ambrein and the studies dealing with Ca channel blocker and adrenergic Mocker followed by ambrein may help to define the factors which contribute to its positive isotropic effects.
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