Characterization of the rat myometrial contractile response to neuropeptide Y.
The in vitro contractile effect of neuropeptide Y (NPY) on rat myometrial strips was for the first time demonstrated and characterised, and the EC50 value estimated to be 267 +/- 87 nM. This effect is presumably mediated by the NPY1 receptor being responsible for postsynaptic effects throughout the peripherial nervous system, thus indicating a direct uterotonic effect of NPY. Further, the effect was demonstrated to the dependent on extracellular Ca2+. Short-term exposures to NPY markedly desensitized the tissue affecting subsequent responses to NPY as well as to oxytocin (OT). This desensitization was time and concentration-dependent, but lasted less than three hours. However, long-term infusions of NPY for 5 days increased to response to both NPY and OT. Long-term infusions of OT caused a marked decrease of the NPY response, and it is concluded that common pathways for up and down regulation of the myometrial responsiveness to several peptide hormones may exist.
Atke
A
A
Department of Medical Physiology, University of Copenhagen, Denmark.
Henriksen
J S
JS
Jacobsen
H S
HS
Vilhardt
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005260:Female; D009119:Muscle Contraction / Q000187:drug effects*; D009215:Myometrium / Q000502:physiology*; D009478:Neuropeptide Y / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017476:Receptors, Neuropeptide Y / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; C062259:neuropeptide Y, Leu(31)-Pro(34)-; D010121:Oxytocin; D014700:Verapamil; D002118:Calcium