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KMID : 0376219820190010049
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Chonnam Medical Journal
1982 Volume.19 No. 1 p.49 ~ p.57
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Study on al-and a2-Adrenoceptors in the Smooth Muscle
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Abstract
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1. Responses of isolated strips of rat and rabbit small intestine to field stimulation were variable: a contraction, a relaxation or a transient relaxation following a contraction in rat and a contraction or a contraction following a transient inhibition of spontaneous pendular movements in rabbit.
2. Clonidine and guanabenz inhibited markedly the contraction and relaxation by the stimulation. This inhibitory effect of two drugs was antagonized by yohimbine but not by prazosin.
3. Phenylephrine (0.5,ug/ue) inhibited markedly the contraction and relaxation the stimulaiton. This inhibitory effect of phenylephrine was antagonized by prazosin but not yohimbine.
4. Atropine inhibited markedly the contraction by the stimulation.
5. Relaxant responses of the strips to phenylephrine and clonidine were markedly weakened by prazosine but not by yohimbine.
6. The above results suggest that two types of a-adrenoceptors, presynaptic a-adrenoceptors(a2) and postsynaptic a-adrenoceptors(a,) exist in the rat and rabbit small intestine, and that the former mediates inhibition -of the release of norepinephrine and acetylcholine from adrenergic and chloinergic nerve endings by´ the stimulation and the latter is involved in inhibitory effects on intestinal movements.
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