6-nitrodopamine is a major endogenous modulator of human vas deferens contractility.

Background: Rat isolated vas deferens releases 6-nitrodopamine (6-ND), and the spasmogenic activity of this novel catecholamine is significantly reduced by tricyclic compounds such as amitriptyline, desipramine, and carbamazepine and by antagonists of the α -adrenergic receptors such as doxazosin, tamsulosin, and prazosin.

Objectives: To investigate the liberation of 6-ND by human epididymal vas deferens (HEVDs) and its pharmacological actions.

Methods: The in vitro liberation of 6-ND, dopamine, noradrenaline, and adrenaline from human vas deferens was evaluated by LC-MS/MS.

β- and β/β-adrenergic receptor antagonists block 6-nitrodopamine-induced contractions of the rat isolated epididymal vas deferens.

6-Nitrodopamine (6-ND) is an endogenous modulator of the contractility in the rat isolated epididymal vas deferens (RIEVD) and considered to be the main peripheral mediator of the emission process. Use of selective and unselective β-adrenergic receptor antagonists has been associated with ejaculatory failure. Here, the effects of selective β- and β/β-adrenergic receptor antagonists on RIEVD contractions induced by 6-ND, dopamine, noradrenaline, adrenaline, and electric-field stimulation (EFS) were investigated.