Evidence for the presence of dopaminergic receptors in vas deferens

Specific dopaminergic recognition sites were identified in membranes prepared from rat vas deferens with the ligand (3H)-haloperidol. Specific binding, defined as the difference of (3H)-haloperidol binding in the presence or absence of an excess of unlabelled haloperidol (100 microM), was saturable and a Scatchard analysis of the data revealed a Kd = 21 nM and a Bmax = 74 fmol/mg prot. (+)-Butaclamol was several times more active in displacing (3H)-haloperidol from binding sites than its pharmacologically inactive enantiomer, (-)-butaclamol, demonstrating stereospecificity of binding. Dopamine displaced 50% of (3H)-haloperidol binding at a concentration of approximately 10 microM, while norepinephrine, epinephrine and serotonin were practically ineffective at this concentration. Our results support the notion that there are dopaminergic receptors in the rat vas deferens. We speculate that some of the known effects of dopamine and dopaminergic drugs on sexual behavior may be mediated peripherally and not solely via the CNS as is usually assumed.