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α‐ADRENOCEPTOR BLOCKING PROPERTIES OF RAUBASINE IN PITHED RATS
Author(s) -
DEMICHEL PATRICIA,
GOMOND PATRICK,
ROQUEBERT JACQUES
Publication year - 1982
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1982.tb09317.x
Subject(s) - yohimbine , clonidine , phenylephrine , stimulation , antagonist , endocrinology , medicine , prazosin , chemistry , pharmacology , blood pressure , receptor
1 Raubasine was compared with yohimbine and corynanthine in pithed rats. Antagonist activity at α 1 ‐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. 2 Antagonist activity at α 2 ‐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. 3 The results indicate that, in vivo , raubasine, like corynanthine, is a selective antagonist at α 1 ‐adrenoceptors and that yohimbine is more potent in blocking α 2 ‐than α 1 ‐adrenoceptors.