Article date: November 1982
By: PATRICIA DEMICHEL, PATRICK GOMOND, JACQUES ROQUEBERT in Volume 77, Issue 3, pages 449-454
Raubasine was compared with yohimbine and corynanthine in pithed rats. Antagonist activity at α1‐adrenoceptors was evaluated on the pressor response to electrical stimulation of the spinal sympathetic outflow and to phenylephrine administration, both being reduced by raubasine in the dose range 1 to 4 mg/kg. Corynanthine was quantitatively similar, but yohimbine was not only less potent but also in doses of 0.125 to 0.5 mg/kg enhanced the effects of electrical stimulation.
Antagonist activity at α2‐adrenoceptors was determined against the inhibitory effects of clonidine on tachycardia induced by electrical stimulation of cardiac sympathetic nerves and against the pressor responses to B‐HT‐933 injection. Raubasine up to 4 mg/kg, like corynanthine, did not affect the pressor responses to B‐HT‐933 nor did it reduce the inhibitory effect of clonidine. By contrast yohimbine reduced the response to BHT‐933 and antagonized clonidine as well as enhancing the tachycardia caused by electrical stimulation.
The results indicate that, in vivo, raubasine, like corynanthine, is a selective antagonist at α1‐adrenoceptors and that yohimbine is more potent in blocking α2‐than α1‐adrenoceptors.
Raubasine was compared with yohimbine and corynanthine in pithed rats. Antagonist activity at α1‐adrenoceptors was evaluated on the pressor response to electrical stimulation of the spinal sympathetic outflow and to phenylephrine administration, both being reduced by raubasine in the dose range 1 to 4 mg/kg. Corynanthine was quantitatively similar, but yohimbine was not only less potent but also in doses of 0.125 to 0.5 mg/kg enhanced the effects of electrical stimulation.
Antagonist activity at α2‐adrenoceptors was determined against the inhibitory effects of clonidine on tachycardia induced by electrical stimulation of cardiac sympathetic nerves and against the pressor responses to B‐HT‐933 injection. Raubasine up to 4 mg/kg, like corynanthine, did not affect the pressor responses to B‐HT‐933 nor did it reduce the inhibitory effect of clonidine. By contrast yohimbine reduced the response to BHT‐933 and antagonized clonidine as well as enhancing the tachycardia caused by electrical stimulation.
The results indicate that, in vivo, raubasine, like corynanthine, is a selective antagonist at α1‐adrenoceptors and that yohimbine is more potent in blocking α2‐than α1‐adrenoceptors.
DOI: 10.1111/j.1476-5381.1982.tb09317.x
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