title: Central opioids: a possible role in parturition?
abstract: Pregnant rats were implanted with subcutaneous minipumps to deliver either naloxone or saline. The time-course of subsequent parturition was different between the two groups: the interval between successive births was significantly shorter for the naloxone-treated rats. This supports the hypothesis that the opioid innervation of the neurohypophysis, which is known to influence oxytocin release profoundly, has a physiological role in parturition. To test the further hypothesis that this role is particularly important in a stressful environment, pregnant rats, again implanted with minipumps, were regularly transferred, at 15-min intervals beginning with the birth of the first pup, between their normal cage and the unfamiliar environment of a glass observation chamber. No difference was noted between the time-courses of parturition for the naloxone- and saline-treated groups, although the time-courses were markedly altered from those observed in rats not subjected to an unfamiliar environment. We conclude that opioid modulation of oxytocin release may play a role in 'spacing' the delivery of successive births during normal parturition.
authors.forename: G
authors.initials: G
authors.lastname: Leng
authors.forename: S
authors.initials: S
authors.lastname: Mansfield
authors.forename: R J
authors.initials: RJ
authors.lastname: Bicknell
authors.forename: A D
authors.initials: AD
authors.lastname: Dean
authors.forename: C D
authors.initials: CD
authors.lastname: Ingram
authors.forename: M I
authors.initials: MI
authors.lastname: Marsh
authors.forename: J O
authors.initials: JO
authors.lastname: Yates
authors.forename: R G
authors.initials: RG
authors.lastname: Dyer
mesh_terms: D000818:Animals; D004723:Endorphins / Q000494:pharmacology; D005260:Female; D007743:Labor, Obstetric / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D049590:Postpartum Period; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological; D013997:Time Factors; D014590:Uterine Contraction / Q000187:drug effects; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin