Lack of neuropeptide Y receptor detection in human bladder and prostate

Objective To investigate the presence of functional neuropeptide Y (NPY) re ceptors in human bladder and prostate (both richly endowed with NPY-contain ing nerve fibers) using peptide YY (PYY) as the agonist. Materials and methods Binding studies were conducted using [I-125]PYY as th e radioligand. Organ-bath studies were performed on isolated tissue strips for direct (postjunctional) contractile effects and for (prejunctional) inh ibition of field stimulation effects. Any possible degradation of PYY was d etermined using high-performance liquid chromatography (HPLC). Results In the radioligand binding studies no quantifiable specific [I-125] PYY binding was detected in human bladder or prostate, while specific high- affinity binding was readily seen in rat cerebral cortex. In organ-bath exp eriments, PYY (up to 1 mu mol/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 b y PYY. Field stimulation-induced contraction was not affected by PYY in eit her human bladder or prostate, but was readily inhibited in rat vas deferen s. HPLC detected no relevant PYY degradation by human bladder or prostate h omogenates. Conclusion Human bladder and prostate express only very few if any function al NPY receptors.