The effect of opioid antagonism and environmental restriction on plasma oxytocin and vasopressin concentrations in parturient gilts

in Journal of Endocrinology
Authors:
S Jarvis
Search for other papers by S Jarvis in
Current site
Google Scholar
PubMed
Close
,
AB Lawrence
Search for other papers by AB Lawrence in
Current site
Google Scholar
PubMed
Close
,
KA McLean
Search for other papers by KA McLean in
Current site
Google Scholar
PubMed
Close
,
J Chirnside
Search for other papers by J Chirnside in
Current site
Google Scholar
PubMed
Close
,
LA Deans
Search for other papers by LA Deans in
Current site
Google Scholar
PubMed
Close
,
SK Calvert
Search for other papers by SK Calvert in
Current site
Google Scholar
PubMed
Close
,
CL Gilbert
Search for other papers by CL Gilbert in
Current site
Google Scholar
PubMed
Close
,
JA Goode
Search for other papers by JA Goode in
Current site
Google Scholar
PubMed
Close
, and
ML Forsling
Search for other papers by ML Forsling in
Current site
Google Scholar
PubMed
Close
Free access

Sign up for journal news

Oxytocin plays an important role at parturition due to its involvement in uterine contractions, foetal expulsion and the onset of maternal behaviour. The role of the related neurohypophysial hormone, vasopressin, is less clear; however, there is some evidence that it is also involved in maternal behaviour and its role in osmotic regulation is well established. The aim of this study was to investigate the inhibitory effects of endogenous opioids on these hormones during the expulsive phase of parturition in the pig, and to examine how opioid restraint interacts with environmental restriction. The subjects of this study were 31 Large Whitex Landrace primiparous sows (gilts). An indwelling jugular catheter was implanted under general anaesthesia at 12 days before the expected parturition day (EPD). From 5 days before the EPD 15 of the gilts were individually housed in a restrictive parturition crate without straw and 16 were individually housed in a straw-bedded pen. Blood samples were taken with increasing frequency towards and during parturition through a catheter extension to reduce disturbance. At 7.5 min after the birth of the first piglet half of the gilts in each environment received a dose of the opioid receptor antagonist naloxone (1 mg/kg, i.v.) with the remaining gilts receiving saline as a control. Overall, there was no effect of environment on either circulating oxytocin or vasopressin. However, both oxytocin and vasopressin were inhibited by endogenous opioids during the expulsive phase. The inhibitory effects of opioids on these hormones did not appear to have any adverse effects on the progress of parturition as judged by cumulative piglet birth intervals. The regulation of the opioid inhibition of oxytocin and vasopressin during parturition is discussed in relation to other neurotransmitters and whether opioid inhibition of these neurohypophysial hormones is part of the 'normal' physiological response to parturition or whether it is stress-induced.

 

  • Collapse
  • Expand