The Differential Involvement of α1-Adrenoceptor Subtypes in the Molecular Effects of Antidepressant Drugs

We investigated whether the functional involvement of α1-adrenergic receptors (α1-AR) in the effects induced by antidepressant drugs, desipramine, and milnacipran varies depending on the α1-AR subtype. First, using a mouse line with triple knockout (KO) of genes encoding all three α1-AR subtypes (ABD-KO) and autoradiographic analysis, we demonstrated that the inactivation of α1-AR did not affect the density of other types of adrenergic receptors, α2- and β-AR in the mouse brain. Subsequently, we utilized three mouse knockout lines with selective knockout of the gene encoding a single α1-adrenergic receptor subtype (A-KO, B-KO, and D-KO). We analyzed the impact of these mutations on tissue levels of monoaminergic neurotransmitters in the hypothalamus (HY). Next, we assessed how a specific mutation affects the chronic effects of desipramine and milnacipran in the selected brain regions of male and female mice at various molecular levels: mRNA expression of genes encoding for α1-AR subtypes, gene expression profiling, and phosphorylation of selected signaling proteins (ERK1/2, Akt, GSK3β). The main finding is that the deletion of the α1D subtype predominantly reduced the chronic effects of milnacipran at the examined transcriptomic and proteomic levels. The pattern of changes differed by gender. Our study revealed the functional diversity between α1-AR subtypes in the molecular mechanisms of antidepressants' drug action.