The Alpha-Adrenoceptor Blocking Properties of Cryptolepine on the Rat Isolated Vas Deferens

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Abstract
Cryptolepine, an alkaloid of Crypto-lepsis sanguinolenta (Lindl. Schlecter) is an antagonist of noradrenaline on the rat isolated vas deferens. It is of about the same potency as phentolamine (pA2 of phentolamine = 7.5 ± 0.40, pA2 of cryptolepine = 6.6 ± 0.35). We here report a potentiatory effect of small doses of cryptolepine (3.0 × 10-7-10-6M) on the effect of noradrenaline, an effect which has not been obtained with phentolamine, and methoxamine - induced contractions of the vas deferens. Cocaine antagonised the potentiatory effects of small doses of cryptolepine. Inhibition of neuronal uptake is suggested as the probable mechanism for the observed potentiation. tolepis sanguinolenta (Lindl. Schlecter), family Asclepiadaceae, [5]. It is a shrub indigenous to tropical Africa and its extracts have found application in traditional medicine, in the treatment of malaria and other infections, [6]. Raymond Hamet reported that the alkaloid had significant hypotensive effect in dogs, with marked vasodilator properties. It also caused a fall in body temperature. Boakye-Yiadom and Dwuma-Badu [3, 4] reported that the alkaloid had antibacterial effects.