Mianserin--an analysis of its peripheral autonomic actions

The autonomic profile of mianserin has been compared with that of yohimbine, phentolamine, phenoxybenzamine and desmethylimipramine. The effects of mianserin on tyramine and noradrenaline pressor responses in the pithed rat were consistent with alpha-adrenoceptor antagonist and uptake blocking properties. In isolated tissue experiments, the selectivity of mianserin for pre- and postsynaptic alpha-adrenoceptors was similar to that of phentolamine. In pitched rats mianserin antagonised the pressor response produced by clonidine and reversed the inhibitory actions of clonidine on cardiac nerve stimulation. In contrast mianserin only caused slight reversal of the inhibitory effects of clonidine on hypogastric nerve stimulation. Uptake blockade itself inhibits hypogastric nerve stimulation and this could counteract any antagonism of the effects of clonidine at the presynaptic alpha-adrenoceptor. The results demonstrate the uptake blocking properties of mianserin and its antagonism at both pre- and postsynaptic alpha-adrenoceptors.