Mianserin hydrochloride (Org GB 94) is a tetracyclic compound with antidepressant properties that blocks alpha-adrenergic, histamine H1, and certain serotonin receptors; it may cause drowsiness and hematological issues.

Mianserin dose-dependently elevates extracellular norepinephrine levels in the prefrontal cortex with minimal impact on the reuptake of norepinephrine in the rat cerebral cortex, due to its blockade of presynaptic inhibitory α2-adrenergic receptors and induction of regeneration-mediated release enhancement. In neonatal 6-OHDA-lesioned rats, mianserin attenuates the effects of SKF38393 and M-CPP, indicating that the actions of dopamine receptor agonists are mediated through the 5-HT neurochemical system. Additionally, in the medial prefrontal cortex of neonatal 6-OHDA-lesioned rats, 10 mg/kg S.C. Mianserin increased extracellular dopamine approximately 6-fold.

In elevated plus-maze experiments, Eltoprazine and Mianserin exhibit opposite effects: Eltoprazine induces anxiogenic-like behavior, while Mianserin triggers an anxiolytic-like response. Mianserin leads to a decreased number of these sites, whereas Eltoprazine results in an increase. Additionally, a subcutaneous dose of 2 mg/kg Mianserin produces a significant statistical increase in dopamine levels, exceeding 30% when compared to saline.