title: Opioid-mediated inhibition of oxytocin during insulin-induced hypoglycemic stimulation of vasopressin in man.
abstract: We have investigated the importance of endogenous opioids in the differential control of neurohypophysial peptide secretion. The effect of the opioid antagonist naloxone on the vasopressin and oxytocin responses to insulin-induced hypoglycemia was studied in 14 male subjects. Either saline (N = 8) or naloxone (4 mg bolus + 6 mg/h, N = 6) was infused iv during the study. After 60 min infusion soluble insulin 0.15 U/kg was injected. Naloxone infusion for 60 min did not alter basal plasma AVP or OT levels. Insulin-induced hypoglycemia led to a significant rise in plasma AVP in both saline and naloxone-infused subjects (P less than 0.05), which was maximal 45 min after insulin. There was no significant difference in the plasma AVP response to hypoglycemia between the 2 groups. Saline-infused subjects did not show any change in plasma OT in response to hypoglycemia whilst during concurrent naloxone infusion there was a significant rise in OT from 1.9 +/- 0.4 pmol/l before insulin to 3.2 +/- 1.3 pmol/l at 45 min (P less than 0.05). We conclude that there is opioid-mediated inhibition of OT which prevents its release when AVP is secreted in response to insulin-induced hypoglycemia.
authors.affiliation: Department of Medicine, Charing Cross and Westminster Medical School, Westminster Hospital, London, UK.
authors.forename: J R
authors.initials: JR
authors.lastname: Seckl
authors.forename: J A
authors.initials: JA
authors.lastname: Haddock
authors.forename: M J
authors.initials: MJ
authors.lastname: Dunne
authors.forename: S L
authors.initials: SL
authors.lastname: Lightman
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*; D011957:Receptors, Opioid / Q000187:drug effects*
chemical_list: D007328:Insulin; D011957:Receptors, Opioid; D001127:Arginine Vasopressin; D009270:Naloxone; D010121:Oxytocin