Effect of nomifensine on anacoccygeus contraction induced by noradrenaline and electrical stimulation

  Nomifensine, an antidepressant agent, competitively inhibits dopamine uptake in the caudate-putamen and nucleus accumbens and binds to both dopaminergic and noradrenergic reuptake sites in the striatum and thalamus. In this study the effect of nomifensine on anacoccygeus contraction induced by noradrenaline and electrical stimulation was investigated in rats and compared to the effect of phentolamine, an α-adrenoceptor antagonist. Nomifensine and phentolamine produced a concentration-dependent reduction in the twitch heights. IC50 values for noradrenaline were 2.7 ± 0.02 x 10-7 M in the absence and 2.04 ± 0.027 x 10-6 M in the presence of nomifensine (3 µM/ml), and 3.4 ± 0.03 x 10-6 M in the presence of phentolamine (0.1 µM/ml). We may conclude that nomifensine has α-adrenergic blocker activity similar to phentolamine.