Neuropeptide Y (NPY) and peptide YY (PYY) effects in the epididymis of the guinea-pig: evidence of a pre-junctional PYY-selective receptor
Abstract
1. The effects of peptide YY (PYY), neuropeptide Y (NPY) and structurally related peptides upon field stimulation-induced and phenylephrine-mediated contractile responses in the cauda epididymis of the guinea-pig were investigated. 2. Preparations of cauda epididymis responded to field stimulation with contractions which were completely attenuated by both the neurotoxin, tetrodotoxin (500 nM), and also by the alpha-adrenoceptor antagonist, phentolamine (3 microM). PYY (n=7) and the truncated peptide analogue PYY(3-36) (n=5) inhibited field stimulation-induced contractions (pIC50+s.e.mean: 8.9+/-0.2 and 9.4+/-0.2, respectively). Pancreatic polypeptide (PP, up to 1 microM, n=6), NPY (up to 100 nM, n=6) and the NPY analogues [Leu31,Pro34]NPY (n=6) and NPY(13-36) (both up to 1 microM, n=5) had no significant effect. 3. The NPY Y1 receptor antagonist BIBP3226 ((R)-N2-(diphenylacetyl)-N[(4-hydroxyphenyl)-methyl]-argininami de) at 750 nM (n=6) and 7.5 microM (n=6) did not affect the PYY-mediated inhibition of field stimulation-induced contractions (pIC50 8.9+/-0.3 and 9.0+/-0.3, respectively). In the presence of BIBP3226 (7.5 microM), NPY (n=6) inhibited field stimulation-induced contractions (pIC50 8.0+/-0.2). 4. NPY, PYY and PYY(3-3...Continue Reading
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