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KMID : 0352519840210010145
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Korea Univercity Medical Journal
1984 Volume.21 No. 1 p.145 ~ p.154
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Influences of Adrenoceptor blockades on the Suppression indueed by Clonidine of Morphine-induced Increase of Plasma Corticosterone level in Mice
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Abstract
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Clonidine is a potent, centrally acting, antihypertensive that produces analgesia and suppresses the opioid withdrawal signs. Ganong et al. reported that catecholamine and clonidine inhibit the ACTH liberation from an anterior pituitary gland.
In order to ascertain whether the suppression induced by clonidine of morphine-induced increase of plasma corticosterone level is related with the stimulation of alpha-2-adrenoceptor, the influences of phenoxybenzamine, yohimbine, and propranolol on the suppression induced by clonidine of morphine-induced increase of plasma corticosterone level in male mice.
The results obtained were summarized as follows:
1. Clonidine 100g/kg or 500g/kg did not affect the basal plasma corticosterone level.
2. Plasma corticosterone level was slightly increased by phenoxybenzamine 10mg/kg or yohimbine 5mg/kg.
3. Plasma corticosterone level was significantly increased by morphine 20mg/kg, ACTH 5g/k_- and picrotoxin 4rng/kg. And the morphine-induced increase was not affected by the clonidine 100g1kg but significantly suppressed by the clonidine 500g/kg. But the ACTH-or picrotoxin-induced increase was not affected by even the clonidine 500g/kg.
4. The suppressing effect of clonidine 500g/kg on the morphine-induced increase was not affected by the pretreatment of propranolol 5mg/kg but significantly inhibited by the pre-treatment of phenoxybenzamine 10mg/kg or yohimbine 5mg/kg.
The results suggest that clonidine dose not affect the basal level of plasma adrenal corticosteroid and the suppression mechanism of clonidine on the morphine-induced increase of plasma corticosterone level is mediated through the stimulation of alpha-2-adrenoceptor.
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