Lack of neuropeptide Y receptor detection in human bladder and prostate

Objective. To investigate the presence of functional neuropeptide Y (NPY) receptors in human bladder and prostate (both richly endowed with NPY-containing nerve fibers) using peptide YY (PYY) as the agonist. Materials and methods. Binding studies were conducted using [¹²⁵I]PYY as the radioligand. Organ-bath studies were performed on isolated tissue strips for direct (postjunctional) contractile effects and for (prejunctional) inhibition of field stimulation effects. Any possible degradation of PYY was determined using high-performance liquid chromatography (HPLC). Results. In the radioligand binding studies no quantifiable specific [¹²⁵I]PYY binding was detected in human bladder or prostate, while specific high-affinity binding was readily seen in rat cerebral cortex. In organ-bath experiments, PYY (up to 1 μmol/L) caused no contraction of human prostate or bladder, whereas noradrenaline and carbachol, respectively, were effective; the potency or efficacy of noradrenaline and carbachol were not altered by PYY. Field stimulation-induced contraction was not affected by PYY in either human bladder or prostate, but was readily inhibited in rat vas deferens. HPLC detected no relevant PYY degradation by human bladder or prostate homogenates. Conclusion. Human bladder and prostate express only very few if any functional NPY receptors.