The effect of pinealectomy on serum progesterone and oestradiol levels during the last stage of pregnancy in rats

Summary Pinealectomy leads to significantly higher levels of progesterone (on days 19 and 20 of gestation) and oestradiol (on days 21 and 22) in the serum of pregnant rats. These results indicate that during the last phase of pregnancy the pineal gland may be modifying the levels of gonadal hormones, although not affecting the sequence of the physiological events.Acknowledgment. The authors wish to thank Miss Ute Schmidt for her invaluable technical assistance.     

Enhancement of serum FSH levels after pinealectomy

Summary The effect of pinealectomy on the circadian periodicity in serum gonadotropins was investigated in adult male rats. Pinealectomy resulted in an elevation of the serum FSH concentration 7 days after the operation. A 4-fold increase in serum FSH over 24 h with no concommitant increase in serum LH following pinealectomy suggests that the control of FSH secretion could be mediated via the pineal gland.     

Enhancement of serum FSH levels after pinealectomy

The effect of pinealectomy on the circadian periodicity in serum gonadotropins was investigated in adult male rats. Pinealectomy resulted in an elevation of the serum FSH concentration 7 days after the operation. A 4-fold increase in serum FSH over 24 h with no concommitant increase in serum LH following pinealectomy suggests that the control of FSH secretion could be mediated via the pineal gland.     

Lesions in suprachiasmatic nuclei simulate effects of pinealectomy on prolactin release in ovariectomized and sulpiride-treated female rats

Summary Previous studies indicate that the pineal gland alters prolactin secretion, and it was suggested that at least part of the effect of the pineal hormone melatonin on prolactin release may be mediated by the hypothalamic structures. In this study, pinealectomy and lesions of the suprachiasmatic nuclei were found to alter serum levels of prolactin in the same direction, an effect that was counteracted by daily afternoon melatonin administration. Melatonin, but not other pineal indoles, also prevented sulpiride-induced prolactin secretion in pinealectomized or suprachiasmatic nuclei-lesioned and ovariectomized rats, which suggested that the pineal gland can modulate prolactin secretion by acting through a dopamine mechanism independent of hypothalamic suprachiasmatic structures.The authors thank Ms Karen Shashok for revising the English style. This work was supported in part by a grant GG85-0168 from the Comisión Asesora de Investigación Cientifica y Ténica. The NIAMDD, through the National Pituitary Agency, supplied the radioimmunoassay materials for prolactin determinations.     

Lesions in suprachiasmatic nuclei simulate effects of pinealectomy on prolactin release in ovariectomized and sulpiride-treated female rats

Previous studies indicate that the pineal gland alters prolactin secretion, and it was suggested that at least part of the effect of the pineal hormone melatonin on prolactin release may be mediated by the hypothalamic structures. In this study, pinealectomy and lesions of the suprachiasmatic nuclei were found to alter serum levels of prolactin in the same direction, an effect that was counteracted by daily afternoon melatonin administration. Melatonin, but not other pineal indoles, also prevented sulpiride-induced prolactin secretion in pinealectomized or suprachiasmatic nuclei-lesioned and ovariectomized rats, which suggested that the pineal gland can modulate prolactin secretion by acting through a dopamine mechanism independent of hypothalamic suprachiasmatic structures.     

Effects of estrogen or progesterone on prepuberal ovaries implanted in castrated adult male rats

Résumé Des greffons d'ovaire de rat impubère placés dans la chambre antérieure de l'il du mâle castré, après traitement avec 0,5 mg de dipropionate d'stradiol ou avec deux doses de 1 mg de progestérone, ont montré une évidente ovulation. On interprète ce fait comme dû á l'action des hormones injectées dans le système nerveux central et qui favorisent le mécanisme de l'ovulation.     

Influence of estrogen and progesterone on the oxygen consumption of rats,with reference to the role played by the thyroid

Résumé Une seule dose de 2 g d'estradiol a augmenté la consommation d'oxygène des rats castrés, seulement quand les thyroïdes étaient intactes. Une dose unique de 0,40 mg de progestérone a augmenté aussi la consommation d'oxygène des rats castrés, en présence ou absence des thyroïdes. A ces doses, il n'y a ni synergisme ni antagonisme entre l'estrogène et le progestérone dans leur influence sur la consommation d'oxygène.     

Do luteinized unruptured follicles secrete progesterone in mature female rats

Unruptured luteinized follicles were shown to secrete less progesterone than did postovulatory corpora lutea in cyclic female rats.     

Proestrous gonadotropin levels in thyroparathyroidectomized female rats

Summary Intact and TPTx animals showed the expected afternoon increase in serum LH, FSH and prolactin levels. But the afternoon increase in serum LH levels in TPTx rats was less than that observed for intact animals (p<0.01). Neither serum prolactin nor FSH levels were altered by TPTx.The excellent technical and secretarial assistance ofS. Hemelt andD. Landman is gratefully acknowledged.     

Comparison between serum LH and FSH levels in male and female rats during the perinatal period]

In the newborn female Rat, no transient LH and FSH serum surges were observed between 0 and 2 hrs., as compared with the newborn male. In the newborn female, a progressive increase in serum gonadotropins was observed between 2 and 6 hrs. These results indicate that, at birth, the pituitary-gonadal axis reacts in a different way in male and female Rats.     

Influence of pinealectomy on corticotropin (ACTH)

Sensory deprivation produced by removing the eyes and olfactory bulbs in male rats allowed pinealectomy to markedly augment the post-adrenalectomy elevation of ACTH levels. Pineal removal or sensory deprivation separately did not have this effect. Thus, intact sensory input and an intact pineal gland are independently capable of restricting the post-adrenalectomy rise in ACTH levels.     

Influence of pinealectomy on corticotropin (ACTH)

Summary Sensory deprivation produced by removing the eyes and olfactory bulbs in male rats allowed pinealectomy to markedly augment the post-adrenalectomy elevation of ACTH levels. Pineal removal or sensory deprivation separately did not have this effect. Thus, intact sensory input and an intact pineal gland are independently capable of restricting the post-adrenalectomy rise in ACTH levels.This work was supported in part by NIH Grant No. P30 HD 10202. We thank F. Lynd and R.J. Reiter for advice, P. Starr and J. Sackman for technical assistance, and Bess Mitchell for typing.     

The effect of glycine on serum luteinizing hormone in adult female rats

The response of serum luteinizing hormone to glycine has been studied during the estrous cycle in adult female rats. I.p. administration of 200 mg of glycine significantly elevated serum luteinizing hormone levels at all stages of the estrous cycle.     

The effect of glycine on serum luteinizing hormone in adult female rats

Summary The response of serum luteinizing hormone to glycine has been studied during the estrous cycle in adult female rats. I.p. administration of 200 mg of glycine significantly elevated serum luteinizing hormone levels at all stages of the estrous cycle.The authors wish to express their gratitude to Dr A.F. Parlow, NIAMDD Rat Pituitary Hormone Program, for the kind supply of radioimmunoassay kits.