Assessment of the adrenergic effects of orphenadrine in rat vas deferens

The peripheral adrenergic effects of orphenadrine, an antiparkinsonian drug , have been evaluated in the rat vas deferens to investigate whether these properties are the same as those of other phencyclidine ligands. In the low micromolar range, orphenadrine enhanced electrically-evoked and exogenous noradrenaline contractile responses in the epididymal portion of rat vas deferens. It also induced spontaneous activity that was inhibited b y prazosin (1 mu M) but not by atropine (20 nM). It inhibited accumulation of [H-3]noradrenaline in rat vas deferens (IC50 = 14.2+/-2.3 mu M). Orphena drine competitively inhibited [H-3]nisoxetine binding in rat vas deferens m embranes (K-i = 1.05+/-0.20 mu M). It can be concluded that orphenadrine, at low micromolar concentrations, in teracts with the noradrenaline reuptake system inhibiting its functionality and thus potentiating the effect of noradrenaline.