Abstract
The mechanism of the hypotensive effect of an amide alkaloid, tetramethylpyrazine
(TMPZ), obtained from the stem of Jatropha podagrica HOOK (Euphorbiaceae) has been investigated in some isolated vascular and extra-vascular
smooth muscle preparations. The results obtained show that the amide alkaloid inhibits
the contractions of the rabbit isolated perfused central ear artery induced by periarterial
electrical stimulation or intraluminally administered noradrenaline; reduces, like
papaverine, the amplitude of the spontaneous myogenic contractions, and noradrenaline-evoked
contractions of the rat isolated portal vein; inhibits the electrical stimulation-induced
or noradrenaline-evoked contractions of the guinea-pig isolated vas deferens and reduces
the periarterial electrical stimulation-induced or noradrenaline-evoked relaxations
of the rabbit isolated duodenum. The antagonism produced by the amide alkaloid on
the responses of these isolated tissue preparations to electrical stimulation or exogenously-added
noradrenaline was similar to that elicited by phentolamine, an alpha-adrenoceptor
antagonist. It is concluded that tetramethylpyrazine (TMPZ) probably causes hypotension
in experimental animals by (a) dilating blood vessels, and/or (b) acting as a non-specific
spasmolytic agent (like papaverine).
Key Word Index
Jatropha podagrica - Euphorbiaceae - Amide Alkaloid Tetramethylpyrazine - Hypotensive
Action - Alpha Adrenoceptor Blockade - Vasodilation - Non-Specific Spasmolytic Agent
