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KMID : 0378019840270090096
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New Medical Journal
1984 Volume.27 No. 9 p.96 ~ p.104
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Suppressing Effect of Alpha-Methyldopa on the Morphine-induced Increase of the Plasma Corticosterone Level in Mice
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Abstract
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Ganong et al. reported that catecholamines and clonidine inhibit the ACTH liberation from an anterior pituitary gland. And Chun et al. suggested that the inhibitory effect of clonidine probably appeared to be mediated by its agonistic effect on the alpha2 -adrenoceptors in the central nervous system.
Therefore, the present study was undertaken to determine if alpha-methyldopa, a centrallyacting antihypertensive including the property of alpha2-adrenoceptor agonist, also produces the inhibition of the morphine-induced increase of plasma corticosterone level, and if so, if it acts in a "clonidine-like" fashion in male mice.
The results obtained were summarized as follows;
1. Alpha-methyldopate HCI(10mg/kg, 50mg/k, and 250mg/kg) did not affect the plasmacorticosterone level.
2. Morphine (20mg/kg) significantly increased the plasma corticosterone level, and the morphine-induced increase was dose-dependently suppressed by the above doses of alpha-methyldopate.
3. The picrotoxin-induced increase of the plasma corticosterone level was moderately suppressed by alpha-methyldopate, 250mg/kg, but the ACTH-induced increase of the level was not affected by alpha-methyldopate.
4. The suppressing effect of alpha-methyldopate on the morphine-induced increase of the plasma corticosterone level was not affected by prazosin and propranolol but significantly inhibited by phenoxybenzamine, yohimbine, and haloperidol.
The above results suggest that the suppression mechanism of alpha-methyldopa on the morphine-induced increase of the plasma corticosterone level may be mediated through the stimulation of alpha2-adrenoceptor and dopamine receptor in the central nervous system.
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