The pituitary and the maintenance of milk secretion

1958 ◽  
Vol 149 (936) ◽  
pp. 330-336 ◽  
Keyword(s):  
Anterior Pituitary ◽  
Causal Factor ◽  
Complete Inhibition ◽  
Posterior Pituitary ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Complete Cessation ◽  
Lack Of Information ◽  
Milk Ejection Reflex

Following the demonstration by Strieker & Grüter (1928) of the lactogenic effects of anterior-pituitary extracts, the importance of the role of the pituitary in maintaining lactation was further emphasized by observations that removal of the pituitary in the lactating animal resulted in a rapid and complete cessation of lactation (for references, see Folley 1952). For a time it was generally assumed that the loss of the anterior pituitary was the causal factor in the cessation of lactation, but when the role of the posterior pituitary in milk ejection was established it became obvious that interference with the milk-ejection reflex could well be the cause of the failure of lactation after hypophysectomy. It therefore seemed desirable to repeat some of the earlier studies on the effect of hypophysectomy on lactation, in order to determine whether the restoration of milk-ejection by the regular administration of oxytocin would affect the results and possibly allow us to distinguish a failure of milk ejection from a failure of milk secretion. In this connexion it may be noted that reports on the maintenance of lactation after hypophysectomy, by administering anterior-pituitary preparations, have been remarkably few, and this lack of information possibly reflects the unsuccessful outcome of attempts which may have failed because milk ejection was not restored. At Shinfield we have studied the effect of hypophysectomy in the lactating rat, both in the presence and absence of adequate oxytocin therapy, and have confirmed that hypophysectomy results in a rapid and complete inhibition of milk secretion (see Cowie 1957), and there seems to be no reason to doubt that this will also be true for other species.

THE ROLE OF THE NEUROHYPOPHYSIS IN THE MILK-EJECTION REFLEX

1952 ◽  
Vol 8 (2) ◽  
pp. 148-161 ◽  
Author(s):  
B. A. CROSS ◽  
G. W. HARRIS
Keyword(s):  
Intravenous Injection ◽  
Mammary Glands ◽  
Posterior Pituitary ◽  
Pituitary Extract ◽  
Active Process ◽  
Milk Ejection ◽  
Marked Diminution ◽  
Milk Ejection Reflex ◽  
Stimulation Of

1. Nursing and suckling behaviour of rabbits is described, and evidence given that an active process of milk ejection ('let-down') occurs in this as in other species. 2. Intravenous injection of posterior pituitary extracts in anaesthetized rabbits resulted in ejection of milk from a cannulated teat duct. The threshold dose was about 5 mU. and maximal responses were produced by 200 mU. of extract. Whole posterior pituitary extract was more effective than the oxytocic fraction, which was in turn more effective than the vasopressor fraction. 3. Stimulation of the supraopticohypophysial (s.o.h.) tract in anaesthetized rabbits also resulted in ejection of milk from a cannulated duct. Kymographic records of this response were similar to those obtained after injection of appropriate doses of posterior pituitary extract. 4. Lesions in the s.o.h. tract in lactating rabbits caused a marked diminution in the quantity of milk obtained by their litters in standard suckling tests, and incomplete evacuation of the mammary glands. Intravenous injection of posterior pituitary extract (30–200 mU.) into the does immediately before nursing gave a marked increase in the amount of milk obtained by the young and complete evacuation of the mammary glands. Stimulation of the region of the s.o.h. tract in these animals failed to elicit milk ejection from cannulated teat ducts. 5. Rabbits with hypothalamic lesions that did not involve the s.o.h. tract showed a normal milk-ejection reflex when suckled by their young, and a milk-ejection response after electrical stimulation of the s.o.h. tract.

THE MAINTENANCE OF LACTATION IN THE RAT AFTER HYPOPHYSIAL ANTERIOR LOBECTOMY DURING PREGNANCY

1961 ◽  
Vol 22 (4) ◽  
pp. 403-408 ◽  
Author(s):  
A. T. COWIE ◽  
J. S. TINDAL
Keyword(s):  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Anterior Lobe ◽  
Milk Secretion ◽  
Adrenocorticotrophic Hormone ◽  
Milk Ejection ◽  
Growth Indices ◽  
Partial Restoration ◽  
Hypophysectomized Rats ◽  
Milk Ejection Reflex

SUMMARY Experiments to determine the pituitary hormones necessary for the maintenance of lactation in the rat in the absence of either the anterior lobe of the pituitary or the entire pituitary are described. The anterior pituitary or the whole of the pituitary was removed on the 12th day of pregnancy and prolactin (25 i.u. twice daily) plus adrenocorticotrophic hormone (ACTH) (2 i.u./day) was given to the animals from parturition to the 10th day of lactation inclusive. The lactational performances of the two operated groups of rats, as judged by the litter-growth indices, were 53% (anterior lobectomy) and 43% (hypophysectomy) of normal. The milk-ejection reflex was completely restored in the anterior-lobectomized rats by the time of parturition, but the hypophysectomized rats required a further 2 days before milk ejection appeared to be normal. Our experiments confirm that prolactin and ACTH are two important factors in the maintenance of milk secretion in the rat. Since only partial restoration was achieved, however, it is clear that other factors, presumably of anterior-pituitary origin, are required for the full restoration of lactation.

NEUROHORMONAL MECHANISMS IN EMOTIONAL INHIBITION OF MILK EJECTION

1955 ◽  
Vol 12 (1) ◽  
pp. 29-37 ◽  
Author(s):  
B. A. CROSS
Keyword(s):  
Emotional Disturbance ◽  
Posterior Pituitary ◽  
Milk Ejection ◽  
Emotional Inhibition ◽  
Conscious Animal ◽  
Adrenal System ◽  
Oxytocin Release ◽  
Posterior Pituitary Gland ◽  
Milk Ejection Reflex ◽  
Main Factor

SUMMARY 1. Fifteen lactating rabbits were maintained on a regime of one daily nursing in which litter weights, milk yields and duration of nursing were recorded. 2. Sodium pentobarbitone anaesthesia blocked the milk-ejection reflex and prevented the removal of more than 15% of the full milk yield by the young. Intravenous injection of 50 mU oxytocin regularly restored normal milk removal; 10 and 20 mU did not. 3. In thirty-five out of forty-two experiments in which the does were suckled while under forcible restraint the amount of milk removed was reduced by 20–100%. In twenty-nine cases injection of 50 mU oxytocin restored normal milk removal. In the remaining six experiments this replacement therapy was fully effective only after the does had been anaesthetized. 4. Kymograph records of milk-ejection responses showed that normal milk removal was associated with a reflex milk-ejection response similar to that produced by 50 mU oxytocin, and incomplete milk removal with a reduced (=5 mU oxytocin) or absent milk-ejection response. Where injection of 50 mU oxytocin failed to restore normal milk removal in the conscious animal, the resulting milk-ejection response was reduced by an amount similar to that produced by injection of 1μg adrenaline. 5. The results indicate that, while activation of the sympathetico-adrenal system does occur, the main factor in emotional disturbance of the milk-ejection reflex is a partial or complete inhibition of oxytocin release from the posterior pituitary gland.

THE ROLE OF THE DORSAL TRACTS OF THE SPINAL CORD AND OF THE MESENCEPHALIC AND THALAMIC LEMNISCAL SYSTEM IN THE MILK-EJECTION REFLEX DURING MILKING IN THE EWE

1970 ◽  
Vol 47 (1) ◽  
pp. 45-53 ◽  
Author(s):  
PH. RICHARD ◽  
I. URBAN ◽  
R. DENAMUR
Keyword(s):  
Spinal Cord ◽  
Sensory System ◽  
Medial Lemniscus ◽  
Milk Ejection ◽  
Milk Ejection Reflex ◽  
Ventral Posterolateral Nucleus ◽  
Bilateral Destruction ◽  
Lemniscal System ◽  
Cervical Level

SUMMARY The milk-ejection reflex after different lesions of the sensory system was studied by mechanical milking of the ewe. Only animals with lesions which did not produce locomotor ataxia were investigated. Section of the dorsal tract of the spinal cord at different thoracic levels blocked the milk-ejection reflex. This was not due to postoperative shock, because the same type of lesion made at the sacral level was without effect. Moreover, unilateral section of this tract blocked the reflex when milking was limited to the ipsilateral mammary gland. At the cervical level, the interruption of the dorsal tract was ineffective, which can probably be explained by the existence, in sheep, of the spino-cervico-thalamic tract. The latter becomes ventral at the cervical level. Lesions of the lemniscal system in the mesencephalon (bilateral coagulation of the medial lemniscus) and in the thalamus (bilateral destruction of the ventral posterolateral nucleus) do not inhibit the milk-ejection reflex. The role of the spinal lemniscal system is discussed in relation to the work of others and to the electrophysiological results obtained by one of us. It is suggested that two sensory systems (lemniscal and extralemniscal) have to interact to induce the release of oxytocin evoked by the stimuli of mammary origin during milking.

scholarly journals 60 YEARS OF NEUROENDOCRINOLOGY: The posterior pituitary, from Geoffrey Harris to our present understanding

2015 ◽  
Vol 226 (2) ◽  
pp. T173-T185 ◽  
Author(s):  
Gareth Leng ◽  
Rafael Pineda ◽  
Nancy Sabatier ◽  
Mike Ludwig
Keyword(s):  
Morphological Changes ◽  
Hormone Secretion ◽  
Posterior Pituitary ◽  
Milk Ejection ◽  
Physiological Importance ◽  
Peptide Release ◽  
Vasopressin Secretion ◽  
Milk Ejection Reflex ◽  
Pulsatile Hormone Secretion ◽  
Present Understanding

Geoffrey Harris pioneered our understanding of the posterior pituitary, mainly with experiments that involved the electrical stimulation of the supraoptico-hypophysial tract. In the present essay, we explain how his observations included clues to the pulsatile nature of the oxytocin signal – clues that were followed up by subsequent workers, including his students and their students. These studies ultimately led to our present understanding of the milk-ejection reflex and of the role of oxytocin in parturition. Discoveries of wide significance followed, including: the recognition of the importance of pulsatile hormone secretion; the recognition of the importance of stimulus-secretion coupling mechanisms in interpreting the patterned electrical activity of neurons; the physiological importance of peptide release in the brain; the recognition that peptide release comes substantially from dendrites and can be regulated independently of nerve terminal secretion; and the importance of dynamic morphological changes to neuronal function in the hypothalamus. All of these discoveries followed from the drive to understand the milk-ejection reflex. We also reflect on Harris's observations on vasopressin secretion, on the effects of stress, and on oxytocin secretion during sexual activity.

THE RETICULO—HYPOTHALAMIC PATHWAY CONTROLLING THE RELEASE OF OXYTOCIN IN THE EWE

1972 ◽  
Vol 53 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Ph. RICHARD
Keyword(s):  
Medial Forebrain Bundle ◽  
Mesencephalic Reticular Formation ◽  
Milk Secretion ◽  
Milk Ejection ◽  
Small Areas ◽  
Specific Effects ◽  
The Central Nervous System ◽  
Milk Ejection Reflex ◽  
Electrical Activities ◽  
Vaginal Stimulation

SUMMARY The pathways of the milk-ejection reflex in the ewe have been described at the spinal and mesencephalic levels (Richard, 1970; Richard, Urban & Denamur, 1970). The present paper describes the pathways followed by impulses of mammary and vaginal origin between the mesencephalic reticular formation and the neurohypophysis. In the anaesthetized ewe the thalamus is not necessary for the transfer of impulses to the neurohypophysis as shown by studying the electrical activities evoked in the pituitary stalk by mammary or vaginal stimulation. These impulses follow a subthalamic pathway through the medial forebrain bundle. In conscious ewes small areas of coagulations in the pathways did not block the milk-ejection reflex during milking because the fibres are diffuse at all levels of the central nervous system. Larger lesions result in non-specific effects which interrupt milk secretion. Supra-diencephalic structures are not necessary for the milk-ejection reflex.

Functional role of intrahypothalamic release of oxytocin and vasopressin: consequences and controversies

1995 ◽  
Vol 268 (4) ◽  
pp. E537-E545 ◽  
Author(s):  
M. Ludwig
Keyword(s):  
Milk Ejection ◽  
In Vitro Techniques ◽  
Hypothalamic Nuclei ◽  
Peptide Release ◽  
Functional Consequences ◽  
Milk Ejection Reflex ◽  
And Behavior

This brief review of vasopressin (VP) and oxytocin (OT) release into the extracellular space of the supraoptic (SON) and paraventricular (PVN) nuclei focuses on recent data illustrating the significance of their intranuclear release and the potential functional consequences. With the use of in vitro techniques, it has been demonstrated that administration of exogenous OT causes local peptide release and that, in vivo, this facilitates the milk ejection reflex. These findings lead to the idea that endogenous peptides are released into the hypothalamic nuclei. Microperfusion techniques have been used to monitor the dynamics of intranuclear OT and VP release in response to distinct stimuli. It is clear that intranuclear release of OT plays a role during reproductive states (parturition and lactation) and that intranuclear release of VP and OT is involved in osmoregulation. This review discusses 1) the origin of the intranuclearly released peptides, 2) stimuli which cause release into the hypothalamic nuclei, and 3) the function of intranuclear VP and OT, e.g., regulation of local morphology, feedback mechanisms and synchronization, and the possible role in regulating autonomic function and behavior.

scholarly journals Role of MRI T2-DRIVE in the assessment of pituitary stalk abnormalities without gadolinium in pituitary diseases

2018 ◽  
Vol 178 (6) ◽  
pp. 613-622 ◽  
Author(s):  
Elisabetta Godano ◽  
Giovanni Morana ◽  
Natascia Di Iorgi ◽  
Angela Pistorio ◽  
Anna Elsa Maria Allegri ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Intraclass Correlation ◽  
Pituitary Stalk ◽  
Posterior Pituitary ◽  
Significant Information ◽  
Post Contrast ◽  
Pituitary Dysfunction ◽  
Pituitary Diseases ◽  
Significant Difference

Objective To investigate the role of T2-DRIVE MRI sequence in the accurate measurement of pituitary stalk (PS) size and the identification of PS abnormalities in patients with hypothalamic–pituitary disorders without the use of gadolinium. Design This was a retrospective study conducted on 242 patients who underwent MRI due to pituitary dysfunction between 2006 and 2015. Among 135 eligible patients, 102 showed eutopic posterior pituitary (PP) gland and 33 showed ‘ectopic’ PP (EPP). Methods Two readers independently measured the size of PS in patients with eutopic PP at the proximal, midpoint and distal levels on pre- and post-contrast T1-weighted as well as T2-DRIVE images; PS visibility was assessed on pre-contrast T1 and T2-DRIVE sequences in those with EPP. The length, height, width and volume of the anterior pituitary (AP), PP height and length and PP area were analyzed. Results Significant agreement between the two readers was obtained for T2-DRIVE PS measurements in patients with ‘eutopic’ PP; a significant difference was demonstrated between the intraclass correlation coefficient calculated on the T2-DRIVE and the T1-pre- and post-contrast sequences. The percentage of PS identified by T2-DRIVE in EPP patients was 72.7% compared to 30.3% of T1 pre-contrast sequences. A significant association was found between the visibility of PS on T2-DRIVE and the height of AP. Conclusion T2-DRIVE sequence is extremely precise and reliable for the evaluation of PS size and the recognition of PS abnormalities; the use of gadolinium-based contrast media does not add significant information and may thus be avoided.

SYMPATHETICO-ADRENAL INHIBITION OF THE NEUROHYPOPHYSIAL MILK-EJECTION MECHANISM

1953 ◽  
Vol 9 (1) ◽  
pp. 7-18 ◽  
Author(s):  
B. A. CROSS
Keyword(s):  
Electrical Stimulation ◽  
Inhibitory Effect ◽  
Posterior Pituitary ◽  
Pituitary Extract ◽  
Milk Ejection ◽  
Emotional Inhibition ◽  
Adrenal System ◽  
Ejection Mechanism ◽  
Milk Ejection Reflex ◽  
Stimulation Of

1. Emotional inhibition of the milk-ejection reflex in rabbits is described. 2. Injection of 5–50 μg adrenaline intravenously into does before nursing interfered with milk ejection, as shown by the failure of the young to withdraw more than three-quarters of the normal yield of milk. Injection of 150 mU (=milliunits) 'Pitocin' immediately after the adrenaline did not restore normal milk ejection. 3. Intravenous injection of 5 μg adrenaline suppressed the milk-ejection response to 50 mU posterior pituitary extract in anaesthetized rabbits with cannulated teats, provided the injection of adrenaline preceded that of the posterior pituitary extract. The inhibitory effect had not entirely disappeared in 2 min. 50μg adrenaline prevented the occurrence of milk ejection for 3½ min. 4. Intravenous doses of 5 μg adrenaline, but not smaller amounts, inhibited the milk-ejection response to electrical stimulation of the supraoptico-hypophysial tract, if injected before stimulation or during the latent period of the response. When injected after the commencement of milk ejection 5 μg adrenaline was without effect, but 50 μg abolished the response. 5. Electrical stimulation of the posterior hypothalamus produced inhibition of the milk-ejection response to injected oxytocic extract, together with pupillary dilatation and exophthalmos. The inhibition closely resembled that resulting from injection of adrenaline. 6. It is concluded that one mechanism involved in the emotional inhibition of milk ejection is an activation of the sympathetico-adrenal system, resulting in antagonism of the action of the neurohypophysial milk-ejection hormone on the contraction process within the mammary gland.

LACTATION IN THE RAT AFTER HYPOPHYSIAL POSTERIOR LOBECTOMY

1956 ◽  
Vol 14 (1) ◽  
pp. 54-65 ◽  
Author(s):  
G. K. BENSON ◽  
A. T. COWIE
Keyword(s):  
Diabetes Insipidus ◽  
Pituitary Hormone ◽  
Posterior Lobe ◽  
Posterior Pituitary ◽  
Milk Ejection ◽  
Milk Ejection Reflex ◽  
Posterior Pituitary Hormone

SUMMARY Ablation of the posterior lobe of the pituitary in the lactating rat abolished the milk-ejection reflex so that the pups could only be reared if injections of oxytocin were given to the mothers twice daily. When, however, these posterior lobectomized rats became pregnant a second time, parturition was normal and the milk-ejection reflex was sufficiently restored for the rats to rear their litters without oxytocin being administered. The animals, however, continued to exhibit diabetes insipidus. Measurements of residual neurohypophysial tissue showed that hypertrophy of the neural stalk had occurred after posterior lobectomy. These findings are discussed in relation to recent studies on the site of formation and the liberation of posterior-pituitary hormone(s) after hypophysectomy.

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