Studies on Cryptolepine

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Abstract
Cryptolepine, (1-8 .mu.g/ml) concentration dependently and competitively (pA2 [competitive antagonistic activity] = 6.40 .+-. 0.03, slope = 1.0) antagonized the vasoconstrictor effect of nordrenaline [norepinephrine] on the isolated perfused rat mesenteric artery, without producing vasodilatation. Prostaglandin[PG]E3 (2.5 .mu.g/ml) completely reversed cryptolepine block of the response of the artery to noradrenaline during normal Kreb''s solution perfusion, but failed to reverse cryptolepine block of the response of the tissue in Ca2+-free Kreb''s perfusion medium. Increasing the Ca2+ concentration from zero did not restore the reversal of the cryptolepine blockade. Ca2+ ions may play a significant role in the PGE2 induced reversal of cryptolepine block of noradrenaline vasoconstrictor response of the tissue.