NON-COMPETITIVE-NON-EQUILIBRIUM ALPHA-ADRENOCEPTOR BLOCKING PROPERTIES OF N-BENZYL IODOACETAMIDE, BETSAMIDE
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1979
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Abstract
N-Benzyl iodoacetamide, betsamide, at 10 mg/kg i.v. blocked the hypertensive and contractile responses of the nictitating membrane of the cat to adrenaline [epinephrine]. The blockade had a lag period before full development. Pretreatment of cats with betsamide for 7 or 18 h showed a non-equilibrium type of .alpha.-adrenoceptor blockade. The responses of the nictitating membrane to adrenaline were markedly depressed and did not recover after high doses of adrenaline. In the same cats, adrenaline caused a profound hypotension. The effect of betsamide lasted for at least 72 h. In the rat isolated vas deferens, 3 .times. 10-5 M betsamide non-competitively blocked the contractile responses to noradrenaline [norepinephrine], the adrenoceptor blockade was less effective when betsamide was applied with noradrenaline. The blockade lasted for > 24 h and was not reversible after extensive washing. Betsamide antagonized the contractile effects of the guinea pig trachea to adrenaline and isoprenaline. Results are discussed in relation to a probable mechanism of action.