Antidiuretic effects of oxytocin in the Brattleboro rat

Summary The antidiuretic activity of oxytocin (OT) was measured in Brattleboro rats with congenital diabetes insipidus. A dose dependent antidiuretic response was found in animals receiving chronic infusions of 0.1 g/h, 1.0 g/h, and 5 g/h of OT. OT infused at the rate of 5 g/h over a 7-day period completely reversed the symptoms of diabetes insipidus. The results support the concept that OT serves as a weak agonist of vasopressin at the level of the kidney and at pharmacological levels exhibits antidiuretic activity.     

The effects of beta-endorphin on arginine-8-vasopressin and oxytocin levels in rat brain areas

Measurements were made of the effects of intracerebroventricular treatment with beta-endorphin (BE; 100 ng) on the arginine-8-vasopressin (AVP) and oxytocin contents of rat hypothalamic and limbic brain areas (hippocampus, amygdala and septum). The hormone concentrations were determined by radioimmunoassay. The administration of BE resulted in a significant reduction of the AVP level in the amygdala in a naloxone-reversible manner. Naloxone (Nal) administered subcutaneously significantly increased the AVP content in the septum. The results revealed that BE and Nal had regionally specific effects on the activity of the vasopressinergic system but not on that of the oxytocinergic system in the brain.     

The effects of beta-endorphin on arginine-8-vasopressin and oxytocin levels in rat brain areas

Summary Measurements were made of the effects of intracerebroventricular treatment with beta-endorphin (BE; 100 ng) on the arginine-8-vasopressin (AVP) and oxytocin contents of rat hypothalamic and limbic brain areas (hippocampus, amygdala and septum). The hormone concentrations were determined by radioimmunoassay. The administration of BE resulted in a significant reduction of the AVP level in the amygdala in a naloxone-reversible manner. Naloxone (Nal) administered subcutaneously significantly increased the AVP content in the septum. The results revealed that BE and Nal had regionally specific effects on the activity of the vasopressinergic system but not on that of the oxytocinergic system in the brain.     

Antidiuretic and thermogenic effects of intracerebroventricular prostaglandin H2 in ethanol-anaesthetized rats

Summary When PGH₂ was administered intracerebroventricularly at doses of 5 and 15 nmoles in ethanol-anaesthetized rats, alcohol diuresis was inhibited and rectal temperature, blood pressure and heart rate were all significantly increased.     

Antidiuretic hormone concentration in blood perfusing the adenohypophysis

Zusammenfassung Der antidiuretische Hormon-(ADH, Vasopressin) Gehalt des die Adenohypophyse durchströmenden Blutes wird für die Ruhephase mit 6 mU/ml und nach schwerem Blutverlust mit 2 U/ml berechnet. Die bisher allgemein vertretene Auffassung, nach welcher das ADH in einer für die normale Stimulation der adenohypophysären Sekretion des ACTH ungenügenden Konzentration vorhanden ist, kann nicht aufrechterhalten bleiben.     

Effect of human serum oxytocinase on the antidiuretic action of lysine vasopressin and oxytocin in the rat

Zusammenfassung Nach i.v. Dauerinfusion von Lysin-Vasopressin oder Oxytocin wird bei der experimentellen Analyse der Wirkung menschlicher Oxytocinase eine Erniedrigung des antidiuretischen Effekts gefunden; diese rührt vom Absinken der Peptidkonzentration sowohl im Blutplasma als auch am Wirkort her.     

Comparison of the mode of action of oxytocin and lysine-vasopressin on the isolated rat uterus

Zusammenfassung Ein der Rezeptorentheorie zugrunde liegender Vergleich der Dosis-Wirkungs-Beziehung zwischen Oxytocin und Lysine-vasopressin an der isolierten Rattengebärmutter hat gezeigt, dass während der Evolution die Oktapeptide der Neurohypophyse sowohl ihre Affinität für den Rezeptor als auch ihre maximale Aktivität bei Absättigung des Rezeptors, «intrinsic activity», verändert haben. Weiterhin wurde gefunden, dass Magnesium-Ionen in einer Konzentration von 0.5 mM nicht nur, wie bisher angenommen, die Affinität der Hormone, sondern auch ihre maximale Aktivität bei Absättigung des Rezeptors beeinflussen.     

Absence of endotoxin-fever but not hyperthermia in Brattleboro rats

I.c.v. administration of bacterial endotoxin produced a fever in the Long-Evans rat but not in the Brattleboro rat. Similar administration of arachidonic acid, prostaglandin E2, prostacyclin, dibutyryl cAMP, norepinephrine, morphine and beta-endorphin caused hyperthermia in both Long-Evans and Brattleboro rats. Variable doses of exogenous arginine vasopressin (AVP) when centrally administered with endotoxin caused fever in the Brattleboro rat. It is suggested that AVP may play an important role in the production and release of endogenous pyrogen.     

The modifying effects of oxytocin on stress-induced changes in post-mortem muscle glycolysis in pigs

Summary The effect of ante-mortem i.m. administration of oxytocin on post-mortem muscle metabolism in Pietrain pigs was examined. Treatment with oxytocin significantly retarded post-mortem glycolysis and stopped the production of pale, soft, exudative meat.     

Absence of endotoxin-fever but not hyperthermia in Brattleboro rats

Summary I. c. v. administration of bacterial endotoxin produced a fever in the Long-Evans rat but not in the Brattleboro rat. Similar administration of arachidonic acid, prostaglandin E₂, prostacyclin, dibutyryl cAMP, norepinephrine, morphine and -endorphin caused hyperthermia in both Long-Evans and Brattleboro rats. Variable doses of exogenous arginine vasopressin (AVP) when centrally administered with endotoxin caused fever in the Brattleboro rat. It is suggested that AVP may play an important role in the production and release of endogenous pyrogen.     

Antidiuretic hormone involvement in the release of alpha-melanocyte-stimulating hormone by hyperosmotic stimuli

In the normal Wistar rat, the plasma alpha-MSH level was raised by hypertonic saline injection (as compared with control rats injected with isotonic saline). No such rise in alpha-MSH followed hypertonic saline administration in the Brattleboro (hereditary diabetes insipidus) animal (compared to isotonic saline injected controls). It is suggested that, in the rat, endogenous antidiuretic hormone is involved in the secretory response of the pars intermedia to osmotic stimuli.     

Peculiar response of Brattleboro rats to selenite

Summary Brattleboro rats were given, on the 10th day of life, a single high dose of sodium selenite. 90% of Brattleboro heterozygotes responded to the treatment by the formation of cataract whereas homozygotes with diabetes insipidus exhibited no cataract.     

Antidiuretic activities of substance P and its analogs

Summary Substance P (SP) and analogs, including 5 nucleoside (ARA or HRA)-peptides, were examined for antidiuretic activity in ethanolized rats. The activity was potent in the analogs embodying the C-terminal hexapeptide, weak in the nucleoside-pentapeptide, and negligible in the nucleoside-tetrapeptide. In addition, the activity was increased by acylation of the hexapeptide. The antidiuretic potencies were also compared with the hypotensive potencies.This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan, and by a grant from the Imanaga Foundation, Nagoya, Japan.     

The effects of halothane on ovulation in the rat

Zusammenfassung Halothan-Anaesthesie während der sogenannten «kritischen Periode» der Proöstrusphase bewirkt eine zentrale Hemmung der Spontanovulation bei der Ratte. Wie Barbiturate und Urethan ist deshalb Halothan als Anaesthetikum zur Erforschung neuroendokriner Mechanismen nur in beschränktem Masse geeignet.

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Supported by a group grant in Developmental Neurobiology from the Canadian Medical Research Council.