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Endogenous Opioids Modulate the Oxytocin Response to Insulin‐Induced Hypoglycaemia and Partially Mediate the Inhibitory Effect of Ethanol in Man
Author(s) -
Coiro V.,
Capretti L.,
Davoli C.,
SperoniJ G.,
Bianconi L.,
Cavazzini U.,
Marcato A.,
Papadia C.,
Volpi R.,
Chioderat P.
Publication year - 1991
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1991.tb00294.x
Subject(s) - (+) naloxone , endocrinology , medicine , bolus (digestion) , ethanol , insulin , endogenous opioid , saline , oxytocin , narcotic antagonist , opioid , chemistry , receptor , biochemistry
The possible inhibition exerted by ethanol on the oxytocin (OT) response to insulin‐induced hypoglycaemia was tested in man. Furthermore, the possibilities that endogenous opioids play a role in the control of hypoglycaemia and/or ethanol action on OT were examined. Insulin tolerance tests were performed in three groups of eight age‐ and weight‐matched normal men treated with: 1) naloxone, group 1 1 mg bolus naloxone + 2.5 mg over 105 min, group 2 2 mg bolus naloxone + 5 mg over 105 min, group 3 4 mg bolus naloxone + 10 mg over 105 min; 2) ethanol (50 ml in 110ml of whiskey) to all the groups; 3) a combination of ethanol + naloxone; 4) normal saline. Furthermore, the effect of ethanol + naloxone (4+10mg) in the absence of insulin‐induced hypoglycaemia was evaluated in seven additional subjects. During this latter test, the plasma levels of OT remained unchanged. Insulin‐induced hypoglycaemia produced a 2.2‐fold increment in plasma OT levels in the control experiments. This response was not changed by the treatment with the lowest dose of naloxone (1+2.5mg) in group 1, but it was significantly enhanced by administration of naloxone at higher doses (mean peak OT levels rose 2.8‐fold in both group 2 and group 3). In all subjects the OT response to hypoglycaemia was completely abolished by ethanol. However, when ethanol was given together with naloxone, the hypoglycaemia‐induced OT rise was only partially inhibited by ethanol. At all doses naloxone produced similar effects; in fact, in all groups OT rose 1.5‐fold in response to hypoglycaemia during insulin tolerance test + ethanol + naloxone. Neither naloxone nor ethanol altered the basal secretion of OT, as tested during 45 min before the insulin tolerance test. These data demonstrate that the OT response to insulin‐induced hypoglycaemia is inhibited by ethanol. Furthermore, the data indicate that endogenous opioids are involved in the control of hypoglycaemia‐stimulated OT secretion and partially modulate ethanol inhibitory action.