Experiments were carried out to establish whether infusion of relaxin prolongs gestation and labour in the rat by suppressing release of oxytocin, and whether the effects of relaxin on birth could be reversed by the opioid antagonist naloxone. Female rats were implanted with subcutaneous osmotic minipumps for the infusion of purified porcine relaxin into the jugular vein for 84 h from either day 19 or day 20 of gestation. Infusion of relaxin delayed the onset of labour and in those animals which delivered during relaxin infusion, delivery was longer by approximately 45 min. Plasma oxytocin levels 40 min after delivery of the first fetus were 45·25 ± 3·6 pmol/l (mean ± s.d.) in unoperated controls and significantly (P < 0·01) depressed (23·89 ± 3·9) in rats that delivered during infusion of relaxin. Rats that delivered after the infusion of relaxin had finished, gave birth significantly (P < 0·05) faster than controls and plasma oxytocin levels were significantly (P < 0·01) raised (77·87 ±15·9 pmol/l). Naloxone treatment (1 mg/kg; i.m.) given immediately after the delivery of the first fetus reversed the inhibitory effect of relaxin and the interval between successive deliveries was slightly faster than that of controls. Plasma oxytocin levels in relaxin-infused naloxone-treated rats were significantly (P < 0·01) higher than values in unoperated control rats. The results confirm that relaxin suppresses oxytocin release possibly through an opioid system and this may be important in the control of the timing of birth.
J. Endocr. (1986) 111, 99–102
Journal of Endocrinology is committed to supporting researchers in demonstrating the impact of their articles published in the journal.
The two types of article metrics we measure are (i) more traditional full-text views and pdf downloads, and (ii) Altmetric data, which shows the wider impact of articles in a range of non-traditional sources, such as social media.
More information is on the Reasons to publish page.
| Sept 2018 onwards | Past Year | Past 30 Days | |
|---|---|---|---|
| Full Text Views | 8 | 2 | 0 |
| PDF Downloads | 4 | 2 | 0 |
Online ISSN: 1479-6805
Print ISSN: 0022-0795
Strengthening biomedical communities
to advance science and health
CONTACT US
Bioscientifica Ltd | Starling House | 1600 Bristol Parkway North | Bristol BS34 8YU | UK
Bioscientifica Ltd | Registered in England no 3190519
