Differential blockade by (-)mianserin of the alpha 2-adrenoceptors mediating inhibition of noradrenaline and serotonin release from rat brain synaptosomes.
Mianserin and its two enantiomers were studied as antagonists of the alpha 2-adrenoceptors mediating inhibition of noradrenaline and 5-hydroxytryptamine release in rat brain cortex. The inhibitory effect of exogenous noradrenaline on the release of 3H-noradrenaline evoked by 15 mM KCl from superfused cortical synaptosomes was antagonized by racemic mianserin and by (+)mianserin; the (-)enantiomer was ineffective. In contrast, both (+)mianserin and (-)mianserin antagonized the inhibitory effect of noradrenaline on the release of 3H-5-hydroxytryptamine. The results suggest that the alpha 2-autoreceptors on noradrenergic nerve endings differ from the alpha 2-adrenoceptors located on serotoninergic terminals.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003984:Dibenzazepines / Q000494:pharmacology*; D008297:Male; D008803:Mianserin / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D013237:Stereoisomerism; D013574:Synaptosomes / Q000378:metabolism*
D000317:Adrenergic alpha-Antagonists; D003984:Dibenzazepines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D008803:Mianserin; D012701:Serotonin; D009638:Norepinephrine