Dopaminergic, but not cholinergic, involvement in regulation of hypoglycemia-induced oxytocin release in man.
ABSTRACT The plasma oxytocin response to insulin-induced hypoglycemia was evaluated in 20 normal male subjects in the basal state (insulin tolerance test (ITT) alone) and after pretreatment with the muscarinic antagonist pirenzepine (40 mg IV 10 min before the ITT in six subjects), the nicotinic antagonist trimethaphan (0.3 mg/min IV for 30 min before the ITT in six subjects), and the dopaminergic receptor agonist bromocriptine (2.5 mg PO 1 hr before the ITT in eight subjects). The drugs did not modify arterial blood pressure nor produce side effects capable of altering oxytocin secretion. Neither pirenzepine nor trimethaphan administration changed the oxytocin response to hypoglycemia, whereas bromocriptine significantly reduced the oxytocin increase during the ITT. These data suggest the involvement of dopaminergic, but not of cholinergic, muscarinic or nicotinic, receptors in the oxytocin response to hypoglycemia.
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ABSTRACT: . Volpi R, Chiodera P, Capretti L, Caffarri G, Giuliani N, Caiazza A, Coiro V (University of Parma, Hospital of Codogno, Hospital of Guastalla, Hospital of Fidenza, Italy). Effect of residual endogenous insulin secretion on the abnormal oxytocin response to hypoglycaemia in insulin-dependent diabetics. J Intern Med 1998; 244: 43–8.Objectives Arginine-vasopressin (AVP) and oxytocin (OT) secretions are abnormally stimulated by hypoglycaemia in patients with IDDM. Since previous studies showed that AVP secretion is influenced by the persistence of residual endogenous insulin secretion, we wondered whether this factor also regulates OT secretion.DesignCase-control study: the OT response to insulin-induced hypoglycaemia was measured in normal and diabetic patients with or without residual endogenous insulin secretion.SubjectsTen normal male subjects, 10 C-peptide positive (CpP) and 11 C-peptide negative (CpN) male diabetic patients.TestsPreliminary studies: plasma C-peptide levels were measured after intravenous administration of 1 mg glucagon.Insulin tolerance test (ITT): diabetics were studied after optimization of their metabolic status by 3 days of treatment with constant subcutaneous insulin infusion. CpP and CpN diabetics and normal controls were tested with an intravenous administration of 0.15 IU per kg body weight insulin. Blood samples for OT assay were taken just before the rapid injection of insulin (time 0) and at time 15, 30, 45 and 60 min.ResultsThe basal concentrations of OT were similar in all groups. Insulin induced a similar hypoglycaemic nadir in all groups at 30 min, even though diabetic groups showed a delayed recovery in blood glucose levels. The glycaemic pattern was similar in all diabetic patients. Hypoglycaemia-induced OT rise was significantly higher in the two diabetic groups than in the normal group. However, CpN patients showed significantly higher OT increments than CpP subjects.Conclusions These data indicate that a residual endogenous insulin secretion exerts a partial protective action against the hypothalamic-pituitary disorder affecting the OT secretory system in IDDM.Journal of Internal Medicine 07/1998; 243(7):43-48. DOI:10.1111/j.1365-2796.1998.00313.x · 5.79 Impact Factor
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ABSTRACT: basal values and pituitary responses) in oligo-and azospermic patients. Recent Progress in Andrology. Giornate Aquilane Internazionali di Andrologia. Aprile 21-23, 1977, pagg. 1-2. 5) VALENTI G., CHIODERA P., VOLPI R., TARDITI E., BANCHINI A., CEDA G.P., VESCOVI P.P.: Interrelazioni tra ghiandole endocrine e obesità nell'anziano. Giornale di Gerontologia 10: 977-990, 1977.Journal of endocrinological investigation 04/2012; 35(4-35):357-358. · 1.55 Impact Factor
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ABSTRACT: Oxytocin has been shown to influence insulin, glucagon and blood glucose levels in various experimental situations. The present study was performed in order to obtain support for a possible interaction of glucose and oxytocin under physiological conditions. We therefore studied whether or not short-term food deprivation (24 hours) affects basal oxytocin levels in male, female and lactating rats, since this is a situation when glucose is mobilized to prevent hypoglycaemia. Secondly, we studied whether oxytocin levels rise in a situation when blood glucose levels fall, i.e. following i.p. injection of insulin (20 U kg-1). In order to explore the role of oxytocin more directly, we investigated whether i.p. injection of the oxytocin antagonist 1-deamino-2-D-Tyr-(OEt)-4-Thr-8-Orn-oxytocin affects blood glucose levels. Plasma levels of oxytocin, insulin and glucagon were measured with radioimmunoassay in samples obtained after decapitation. We found that oxytocin levels were significantly increased following short-term food deprivation in lactating rats. We also found that insulin-induced hypoglycaemia could elevate plasma levels of oxytocin in female and male rats. In addition, administration of an oxytocin antagonist cause a small, but significant decrease in blood glucose levels after 30 min. These data imply that oxytocin may be one of several factors that take part in the control of blood glucose regulation.Acta Physiologica Scandinavica 04/1992; 144(3):355-9. DOI:10.1111/j.1748-1716.1992.tb09305.x · 2.55 Impact Factor