Planta Med 1982; 44(4): 241-245
DOI: 10.1055/s-2007-971458
Research Articles

© Hippokrates Verlag Stuttgart

Preferential Blockade of Pre-Synaptic Alpha-Adrenoceptors on the Rat Isolated Vas Deferens by Cryptolepine, 7: Studies on Cryptolepine

B. K. Noamesi, S. O. A. Bamgbose
  • Dept. of Pharmacology, College of Medicine, University of Lagos
Further Information

Publication History

1981

Publication Date:
29 March 2007 (online)

Abstract

The twitch response of the rat isolated vas deferens to electrical field stimulation, (1 to 10 Hz, 1 to 2 m. sec.), reduced by noradrenaline (1 to 2 µg ml-1) was further enhanced by cryptolepine (5 to 10 µg ml-1). Cryptolepine (0.1 to 0.2 µg ml-1) antagonised the inhibition of the twitch produced by clonidine (1 to 2 ng ml-1) but did not antagonise the phenylephrine effect. Cryptolepine (1 to 2 µg ml-1) inhibited the potentiation of the twitch response and contraction of the muscle produced by phenylephrine (0.3 µg ml-1). Potentiation of the twitch produced by cocaine (1 to 5 µg ml-1) was also enhanced by Cryptolepine (1 to 2 µg ml-1).

The results demonstrated by the difference in the concentration of Cryptolepine required to block pre-and post-junctional α-adrenoceptor effects of clonidine and phenylephrine suggest that cryptolepine has preferential presynaptic α-adrenoceptor blokking action.