RESUMEN
BACKGROUND: A report examining whether clinically available antidepressants increase urethral smooth muscle contraction via antagonistic effects on the α2-adrenoceptor (α2-AR) is lacking. OBJECTIVES: The present study was performed to evaluate the potential of clinically available antidepressants to reverse α2-AR-mediated contractile inhibition in rat vas deferens, in order to predict whether they can induce voiding impairment. METHOD: The effects of 18 antidepressants of different classes on electrical field stimulation (EFS)-induced contractions suppressed by 10-8 mol/L clonidine (a selective α2-AR agonist) in isolated rat vas deferens were investigated and related to their respective clinical blood concentrations. RESULTS: The EFS-induced contractions suppressed by clonidine were recovered by amitriptyline (a tricyclic antidepressant), mirtazapine (a noradrenergic and specific serotonergic antidepressant), and trazodone (a serotonin 5-HT2A receptor antagonist) at concentrations close to the clinical blood levels. EFS-induced contractions were also recovered by trimipramine, clomipramine (tricyclic antidepressants), mianserin (a tetracyclic antidepressant), sertraline (a selective serotonin reuptake inhibitor [SSRI]), and sulpiride (a dopamine D2-receptor antagonist), albeit at concentrations that substantially exceeded their clinically-achievable blood levels. EFS-induced contractions were not significantly affected by imipramine, nortriptyline, amoxapine (tricyclic antidepressants), maprotiline (a tetracyclic antidepressant), fluvoxamine, paroxetine, escitalopram (SSRIs), milnacipran, duloxetine (serotonin and noradrenaline reuptake inhibitors), and aripiprazole (a dopamine partial agonist). CONCLUSIONS: These findings suggest that amitriptyline, mirtazapine, and trazodone induce voiding impairment caused by increased urethral resistance by enhancing sympathetic nerve activities attributed to α2-AR antagonism.