Biomaterial Database

Posterior pituitary lobectomy abolishes the suckling-induced rise in prolactin (PRL): evidence for a PRL-releasing factor in the posterior pituitary. 1987

I Murai, and N Ben-Jonathan

The aim of this study was to determine the role of the posterior pituitary in the regulation of PRL release during suckling. Lactating rats were subjected to posterior pituitary lobectomy (LOBEX) or sham surgery (SHAM) and separation from pups in the evening; experimental manipulations and blood collection were performed the next morning. In the first experiment rats were divided into three groups: SHAM, LOBEX, and LOBEX treated with a vasopressin analog, 1-desamino-8-D-arginine vasopressin and oxytocin. Plasma PRL levels in SHAM rats increased 20- to 25-fold upon introduction of pups and remained elevated for the duration of suckling. In contrast, basal plasma PRL levels in LOBEX rats were 3- to 4-fold higher than in SHAM but suckling failed to induce a further increase. Treatment of LOBEX rats with 1-desamino-8-D-arginine vasopressin and oxytocin reduced water consumption and allowed for milk ejection and milk intake by the pups but did not restore the suckling-induced rise in PRL. The second experiment tested the functional integrity of the hypothalamic dopamine (DA) and serotonergic systems after LOBEX and the ability of LOBEX-lactating rats to respond to PRL-releasing stimuli other than suckling. Injections of alpha-methyl-para tyrosine, an inhibitor of tyrosine hydroxylase, and 5-hydroxytryptophan, a precursor of serotonin, caused 20- to 30-fold rises in plasma PRL levels in both LOBEX and SHAM rats. Exposure to ether elicited a 3- to 4-fold rise in PRL which was higher in magnitude and of longer duration in LOBEX than in SHAM rats. CONCLUSIONS Removal of the posterior pituitary from lactating rats results in an increase in basal PRL levels and a complete abolishment of the suckling-induced rise. Vasopressin and oxytocin restore water balance and milk ejection in the LOBEX rat but fail to affect PRL secretion. The LOBEX-lactating rat is not refractory to PRL-releasing stimuli other than suckling and its hypothalamic DA and serotonergic systems are functionally intact. In addition to DA, the posterior pituitary appears to contain a PRL-releasing factor(s) which mediates the suckling-induced rise in PRL.

UI	MeSH Term	Description	Entries
D007031	Hypothalamus	Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.	Lamina Terminalis,Preoptico-Hypothalamic Area,Area, Preoptico-Hypothalamic,Areas, Preoptico-Hypothalamic,Preoptico Hypothalamic Area,Preoptico-Hypothalamic Areas
D007774	Lactation	The processes of milk secretion by the maternal MAMMARY GLANDS after PARTURITION. The proliferation of the mammary glandular tissue, milk synthesis, and milk expulsion or let down are regulated by the interactions of several hormones including ESTRADIOL; PROGESTERONE; PROLACTIN; and OXYTOCIN.	Lactation, Prolonged,Milk Secretion,Lactations, Prolonged,Milk Secretions,Prolonged Lactation,Prolonged Lactations
D008781	Methyltyrosines	A group of compounds that are methyl derivatives of the amino acid TYROSINE.
D008893	Milk Ejection	Expulsion of milk from the mammary alveolar lumen, which is surrounded by a layer of milk-secreting EPITHELIAL CELLS and a network of myoepithelial cells. Contraction of the myoepithelial cells is regulated by neuroendocrine signals.	Milk Let-down,Ejection, Milk,Milk Let down
D010121	Oxytocin	A nonapeptide hormone released from the neurohypophysis (PITUITARY GLAND, POSTERIOR). It differs from VASOPRESSIN by two amino acids at residues 3 and 8. Oxytocin acts on SMOOTH MUSCLE CELLS, such as causing UTERINE CONTRACTIONS and MILK EJECTION.	Ocytocin,Pitocin,Syntocinon
D010904	Pituitary Gland, Posterior	Neural tissue of the pituitary gland, also known as the neurohypophysis. It consists of the distal AXONS of neurons that produce VASOPRESSIN and OXYTOCIN in the SUPRAOPTIC NUCLEUS and the PARAVENTRICULAR NUCLEUS. These axons travel down through the MEDIAN EMINENCE, the hypothalamic infundibulum of the PITUITARY STALK, to the posterior lobe of the pituitary gland.	Neurohypophysis,Infundibular Process,Lobus Nervosus,Neural Lobe,Pars Nervosa of Pituitary,Posterior Lobe of Pituitary,Gland, Posterior Pituitary,Infundibular Processes,Lobe, Neural,Lobes, Neural,Nervosus, Lobus,Neural Lobes,Pituitary Pars Nervosa,Pituitary Posterior Lobe,Posterior Pituitary Gland,Posterior Pituitary Glands,Process, Infundibular,Processes, Infundibular
D011247	Pregnancy	The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.	Gestation,Pregnancies
D011388	Prolactin	A lactogenic hormone secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). It is a polypeptide of approximately 23 kD. Besides its major action on lactation, in some species prolactin exerts effects on reproduction, maternal behavior, fat metabolism, immunomodulation and osmoregulation. Prolactin receptors are present in the mammary gland, hypothalamus, liver, ovary, testis, and prostate.	Lactogenic Hormone, Pituitary,Mammotropic Hormone, Pituitary,Mammotropin,PRL (Prolactin),Hormone, Pituitary Lactogenic,Hormone, Pituitary Mammotropic,Pituitary Lactogenic Hormone,Pituitary Mammotropic Hormone
D011919	Rats, Inbred Strains	Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.	August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D003894	Deamino Arginine Vasopressin	A synthetic analog of the pituitary hormone, ARGININE VASOPRESSIN. Its action is mediated by the VASOPRESSIN receptor V2. It has prolonged antidiuretic activity, but little pressor effects. It also modulates levels of circulating FACTOR VIII and VON WILLEBRAND FACTOR.	Desmopressin,Vasopressin, Deamino Arginine,1-Deamino-8-D-arginine Vasopressin,1-Desamino-8-arginine Vasopressin,Adiuretin,Adiuretin SD,Apo-Desmopressin,DDAVP,Desmogalen,Desmopressin Acetate,Desmopressin Monoacetate,Desmopressin Monoacetate, Trihydrate,Desmopressine Ferring,Desmospray,Desmotabs,Minirin,Minurin,Nocutil,Octim,Octostim,Acetate, Desmopressin,Arginine Vasopressin, Deamino,Ferring, Desmopressine,Monoacetate, Desmopressin,Monoacetate, Trihydrate Desmopressin,Trihydrate Desmopressin Monoacetate,Vasopressin, 1-Deamino-8-D-arginine,Vasopressin, 1-Desamino-8-arginine