Oxytocin In Rats Research Articles

Effect of estrogen treatment on plasma oxytocin and vasopressin in ovariectomized rats.

Effects of estrogen treatment (estradiol benzoate 20μg per day for 2days) on plasma concentration of oxytocin and vasopressin were studied in ovariectomized female rats under urethane-anesthesia (1.2g/kg). Plasma oxytocin was measured by bioassay, while plasma vasopressin was determined by both bioassay and radioimmunoassay. Plasma oxytocin levels (46.2-232.2μU /ml) in the jugular blood of estrogentreated rats were found to be significantly (p<0.05) higher than those (non-detectable level to130.0μU/ml) of the ovariectomized control rats. The mean plasma vasopressin levels determined by bioassay were 172±66 (mean±SEM)%mu;U/ml in control rats and 176±32μU/ml in estrogen-treated rats. The mean concentrations of immunoreactive plasma vasopressin were60.1±19.6μU/ml in the control and75.5±26.8μU/ml in estrogen treated rats. Thus no significant change in plasma vasopressin due to the estrogen treatment was found, whatever method was employed to determine its concentrations.Anterior or posterior hypothalamic deafferentations were made in estrogen-treated ovariectomized rats. The facilitatory effect of estrogen on oxytocin release was not found in the rats with anterior deafferentation. The plasma oxytocin level in the estrogentreated rats with the anterior deafferentation was significantly (p<0.05) lower than that in the estrogen-treated rats without the hypothalamic deafferentation. On the other hand, the plasma oxytocin level in the estrogen-treated rats with posterior deafferentation did not show any significant difference from either that of ovariectomized control rats or that of estrogen-treated ovariectomized rats with intact brain.The present data indicate that estrogen stimulates oxytocin release in the female rat and that such an action of estrogen is exerted mainly by activating the anterior neural input to the neurosecretory cells in the hypothalamo-neurohypophysial system. Whether or not estrogen gives influence on the posterior neural input to the neurosecretory cells is equivocal in the present experiment.An additional experiment was made to determine the effect of urethane on plasma vasopressin. Urethane-anesthetized rats showed a significantly (p<0.01) higher plasma vasopressin level than conscious or pentobarbitone-anesthetized rats.

Radioimmunoassay of plasma and pituitary oxytocin in pregnant rats during various stages of pregnancy and parturition.

Radioimmunoassayable plasma and pituitary oxytocin (ROT) was measured during pregnancy and parturition. The highest mean plasma ROT level was seen in maternal rats on day 20 of pregnancy followed by a non significant decrease on day 21 reaching the basal level just before delivery. Plasma ROT level declined continuously up to the time of delivery of the first pup and then gradually increased until the completion of parturition. The highest maternal mean pituitary ROT level was found on day 21 pregnancy. Just before delivery of the first pup, the mean pituitary ROT level significantly declined by 22%. Pituitary ROT level declined steadily during the delivery of the first five pups. This pattern of reduction was reversed and ROT levels increased between the delivery of the fifth pup and the completion of labor. The increase of maternal pituitary and plasma ROT levels during delivery of the pups suggest that maternal ROT may play a role in normal parturition. Fetal hypothalamic-pituitary ROT does not seem to play any part in parturition.

Inhibition of oxytocic responses to oxytocin in pregnant rats by (1-L-penicillamine)oxytocin and (1-beta-mercapto-beta, beta-diethylpropionic acid)oxytocin.

SummaryThe ability of [1-L-pcnicillamine]oxytocin and [1-β-mercapto-β,β-diethyl-propionic acid]oxytocin to suppress the contractions induced by oxytocin in the uteri of 12- to 16-day-pregnant rats has been demonstrated, using a new technique for recording uterine activity in vivo.

Effect of hypothalamic extracts and exogenous prolactin on reaccumulation of prolactin in the pituitary of the lactating rat after suckling.

SUMMARY The reaccumulation after suckling of prolactin by the pituitary of spayed lactating rats was significantly increased after a single s.c. injection of acidic extract of rat hypothalamus (stalk-median eminence region) given at the start of the reaccumulation period. Injection of ammonium acetate, an extract of ovine hypothalamus rich in luteinizing hormone-releasing factor (LH-RF), extract of rat occipital cortex or oxytocin was ineffective. An extract of ovine hypothalamus rich in prolactin-inhibiting factor (PIF) (0·15 ml./rat) blocked the fall in pituitary prolactin concentration induced by suckling, but in the same or higher (0·3 ml.) doses neither increased nor depressed the reaccumulation of prolactin after suckling. A single s.c. injection after suckling of 2–8 mg. ovine prolactin in each of four instances significantly increased the amount of prolactin reaccumulated by the pituitary. The level attained was equal to or greater than that resulting from injecting rat hypothalamic extract. These results suggest that the increased blood level of prolactin after suckling stimulates the reaccumulation of prolactin in the pituitary possibly indirectly via a factor or factors in the hypothalamus.

Oxytocin and uterine function in pregnant and parturient rats.

Oxytocin and uterine function in pregnant and parturient rats.

THE INFLUENCE OF HYPOPHYSECTOMY AND OF ADRENALECTOMY ON THE URINARY CHANGES INDUCED BY OXYTOCIN IN RATS.

The Journal of PhysiologyVolume 171, Issue 3 p. 403-410 ArticleFree Access The influence of hypophysectomy and of adrenalectomy on the urinary changes induced by oxytocin in rats P. Lees, P. LeesSearch for more papers by this authorMary F. Lockett, Mary F. LockettSearch for more papers by this author P. Lees, P. LeesSearch for more papers by this authorMary F. Lockett, Mary F. LockettSearch for more papers by this author First published: 01 July 1964 https://doi.org/10.1113/jphysiol.1964.sp007386Citations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume171, Issue3July 1, 1964Pages 403-410 RelatedInformation

Oxytocin in pregnancy and labour.

The actions and functions of oxytocin in relation to the pregnant human uterus will be given special attention. Other aspects will be briefly reviewed with emphasis on recent work. The pharmacology of oxytocin and of related octapeptides has been reviewed by Van Dyke (1960) and by Berde & Cerletti (1960). (1) Renal effects. In dogs and rats oxytocin modifies renal pressor function (RPF) and urinary excretion of water, sodium, potassium and chloride. The effects vary with the dose, the rate of urine flow and the species. The kidney of man, however, seems to be refractory to oxytocin (Pickford 1960). (2) Cardiovascular effects. In men and non-pregnant women the rapid intravenous injection of oxytocin (200 to 600 mU) causes dilatation of skin and muscle vessels, a drop in blood pressure and a rise in cardiac output (Pickford 1960). Similar effects are produced by the macroinfusion (1000 to