title: Nocistatin inhibits pregnant rat uterine contractions in vitro: roles of calcitonin gene-related peptide and calcium-dependent potassium channel.
abstract: The endogenous neuropeptide nociceptin/orphanin FQ, translated from the prepronociceptin gene, exerts a contraction-inhibitory effect on the rat uterus. As nocistatin has been reported to cause functional antagonism of the pro-nociceptive effects of nociceptin, we set out to investigate its effects on the pregnant rat uterus and to elucidate its signalling pathway. The expression of prepronociceptin mRNA in the uterus and nocistatin levels in the uterus and the plasma were confirmed by RT-PCR and radioimmunoassay. The uterine levels of prepronociceptin mRNA and nocistatin were significantly increased by the last day of pregnancy, while the plasma nocistatin levels remained unchanged. In the isolated organ bath studies nocistatin inhibited the prostaglandin- and the KCl-evoked contractions in the uterus dose-dependently. This latter effect was decreased by preincubation with capsaicin. Incubation with calcitonin gene-related peptide after capsaicin treatment caused an elevation in the contraction-inhibitory effect of nocistatin. The effect of nocistatin was also decreased by the Ca(2+)-dependent K(+) channel inhibitor paxilline, against spontaneous uterine contractions. Nociceptin potentiated the action of nocistatin. Naloxone decreased the effect of nocistatin administered either alone or in combination with nociceptin. In Ca(2+)-poor environment, this effect of naloxone was suspended. Enzyme immunoassay for the uterine intracellular cAMP levels partially confirmed the results of in vitro contractility studies. We conclude that nocistatin, generated locally in the uterus, exerts an inhibitory effect, the mechanism being mediated in part by Ca(2+)-dependent K(+) channels, the elevation of cAMP levels and sensory neuropeptides.
authors.affiliation: Department of Pharmacodynamics and Biopharmacy, University of Szeged, H-6720 Szeged, Eötvös u. 6, Hungary.
authors.forename: Beáta H
authors.initials: BH
authors.lastname: Deák
authors.forename: Anna
authors.initials: A
authors.lastname: Klukovits
authors.forename: Kornélia
authors.initials: K
authors.lastname: Tekes
authors.forename: Eszter
authors.initials: E
authors.lastname: Ducza
authors.forename: George
authors.initials: G
authors.lastname: Falkay
authors.forename: Róbert
authors.initials: R
authors.lastname: Gáspár
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004347:Drug Interactions; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D018847:Opioid Peptides / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011247:Pregnancy; D011498:Protein Precursors / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000235:genetics; D014590:Uterine Contraction / Q000187:drug effects*; D014599:Uterus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D000097629:Nociceptin
chemical_list: D015740:Calcitonin Gene-Related Peptide; D002118:Calcium; D000242:Cyclic AMP; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D009270:Naloxone; D018847:Opioid Peptides; D011188:Potassium; D024681:Potassium Channels, Calcium-Activated; D011498:Protein Precursors; D012333:RNA, Messenger; D011957:Receptors, Opioid; D000097629:Nociceptin; C494842:Kcnma1 protein, rat; C111148:nocistatin; C121527:prepronociceptin
keywords: Calcitonin gene-related peptide; Nocistatin; Potassium channel; Pregnant rat; Uterine contractility