Neuromuscular and Cardiovascular Actions of Tetramethylpyrazine from the Stem of Jatropha podagrica

Abstract

The neuromuscular and cardiovascular activities of an amide alkaloid (tetramethylpyrazine, TMP2) isolated from the stem of Jatropha podagrica Hook (Euphorbiaceae) have been investigated in some experimental animals. The results obtained show that the alkaloidal extract possesses neuromuscular-blocking and hypotensive effects. The extract also inhibited the indirect electrically-evoked contractions of the nictitating membrane of anaesthetized cats. The neuromuscular activity of the extract was found to be similar to that of d-tubocurarine. In anaesthetized cats, the hypotension induced by the alkaloid was not altered by cervical bilateral vagotomy, atropinization or mepyramine pretreatment, suggesting that the hypotensive effect is unlikely to be mediated via cholinergic or histamine Ht-receptor stimulation mechanisms. Plausible mechanisms of the hypotensive action of the extract are discussed.