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KMID : 0360419840200020015
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Korean Journal of Pharmacology
1984 Volume.20 No. 2 p.15 ~ p.21
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Pharmacological Evaluation of the Mechanism of α-Adrenoceptor-Mediating Sleep in Chickens
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Abstract
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It was aimed to study the effects of a2-adrenoceptor agonists on the sleeping time in onetwo-day-old chickens. Furthermore, it was also evaluated whether a,-adrenoceptor agonist and antagonist might affect the sleeping in the chickens and discussed in relation with opiate receptor.
1) Guanabenz, clonidine, guanfacine and B-HT 933 decreased the latency of the loss of righting reflex in a dose-dependent manner, but B-HT 920 and oxymetazoline slightly prolonged it.
2) a27Adrenoceptor agonists produced dose-related increase in sleeping time. The potency was guanabenz>clonidine>oxymetazoline~B-HT 933,B-HT 920>guanfacine in this order.
3) a2-Adrenoceptor antagonists decreased guanabenz-induced sleeping time in a dose-dependent manner. The rank order of a2-adrenoceptor antagonists was yohimbine>rauwolscine> piperoxan~RX 781094.
4) Sleeping time caused by both ethanol and hexobarbital was not affected by yohimbine in chickens.
5) Methoxamine and phenylephrine showed little significant effect on the guanabenz-induced sleeping time. However, prazosin increased it. Paradoxically, corynanthine rather caused to decrease it.
These results suggest that the stimulation of central a2-adrenoceptor mediates sleeping, however it is remained uncertain in the role of central al adrenoceptor in chickens. In addition, the onetwo-day-old chickens may be considered as a useful, inexpensive and simple experimental model to evaluate the in vivo pharmacological action of the a2-adrenoceptor agonist and antagonist related to sedation.
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