Effects of subacute opioid administration during late pregnancy in the rat on the initiation, duration and outcome of parturition and maternal levels of oxytocin and arginine vasopressin

R. G. Evans, J. E. Olley, G. E. Rice, J. M. Abrahams

Research output: Contribution to journalArticleResearchpeer-review

13 Citations (Scopus)


1. The effects, on parturition in the rat, of subacute and acute opioid administration were studied. Further experiments investigated the role of modulation of maternal plasma and pituitary oxytocin (OXY) and arginine vasopressin (AVP) levels in these effects. 2. Subacute opioid (M320, buaprenorphine or bremazocine) administration prolonged the gestation of rats. This was accompanied by toxic effects on the offspring. Acute subcutaneous (s.c.) M320 (10 μg/kg) administration was accompanied by prolonged gestation without toxic effects. 3. Subacute M320 (10 μg/kg, s.c., twice daily) treatment was accompanied by increased interbirth intervals in parturient rats. 4. Maternal OXY but not AVP release, as assessed by measurement of plasma and pituitary immunoreactivity, was elevated during and up to 1 h after the completion of parturition. Subacute M320 treatment did not inhibit this elevated OXY release.

Original languageEnglish
Pages (from-to)169-178
Number of pages10
JournalClinical and Experimental Pharmacology and Physiology
Issue number3
Publication statusPublished - 1989


  • arginine vasopressin
  • duration of parturition
  • gestation
  • M320
  • neurohypophysis
  • opiate
  • oxytocin
  • parturition
  • receptors
  • toxicity

Cite this