Tetramethylpyrazine, a calcium antagonist.

Tetramethylpyrazine (TMP) is a compound purified from a medicinal plant Ligusticum wallichii Franch. Its effects on in vivo blood pressure, in vitro vascular contractility, and intracellular calcium regulation in rats were examined in the present study to see if it was a possible calcium antagonist in the vascular tissue. Data showed that TMP was hypotensive and had a direct vascular effect. It not only blocked the entry of extracellular calcium through calcium channels but also inhibited the release of intracellular stored calcium in the vascular smooth muscle cell. It was a true calcium antagonist.