Effects of adrenoceptor agonists and antagonists on sulfobromophthalein disposition in mice

The effects of α₂-adrenoceptor agonists on sulfobromophthalein (BSP) disposition in mice were studied. It was found that agents with both central and peripheral activities (clonidine, guanabenz, B-HT 920 and methyldopa) as well as peripherally acting α₂-adrenoceptor agonists (para amino-clonidine and St 91) inhibited sulfobromophthalein disposition in the mouse, and also caused substantial hypothermia. The effects of these agonists were inhibited by yohimbine, a specific α₂-antagonist, except for those of para amino-clonidine where only partial reversal was achieved. The effects of clonidine on BSP disposition were also reversed by piperoxan but not by the α₁-adrenoceptor antagonists, prazosin and phenoxybenzamine, nor by the β-blocker, propranolol. These results suggest that, in mice, peripheral α₂-adrenoceptors are involved in the effects of the α-agonists on BSP disposition.