THE AFFERENT PATHWAY OF THE MILK-EJECTION REFLEX IN THE MID-BRAIN OF THE GOAT

1972 ◽  
Vol 52 (2) ◽  
pp. 333-341 ◽  
Author(s):  
G. S. KNAGGS ◽  
A. S. McNEILLY ◽  
J. S. TINDAL
Keyword(s):  
Guinea Pig ◽  
Afferent Pathway ◽  
Milk Ejection ◽  
Spinothalamic Tract ◽  
Blood Samples ◽  
Indifferent Electrode ◽  
Oxytocin Release ◽  
Milk Ejection Reflex ◽  
Fuller’S Earth ◽  
Stimulation Of

SUMMARY The position of the pathway for the release of oxytocin in the mid-brain was ascertained by exploration of a transverse stereotaxic plane (A4) in 23 anaesthetized goats. Electrical stimulation was applied between a monopolar electrode and an indifferent electrode in the scalp. Oxytocin release was monitored by simultaneous collection of blood samples during stimulation from a catheter in a jugular vein. The blood samples were extracted by the Sephadex G-25 or fuller's earth method and assayed for oxytocin content on the lactating guinea-pig preparation. Oxytocin release occurred occasionally after stimulation of certain sites in the tectum, central grey and reticular formation. Regular releases of oxytocin, however, were only obtained after stimulation of a pathway which was compact and lay in the lateral tegmentum of the mid-brain in association with the spinothalamic tract. The position of this pathway corresponds to that described previously for the afferent pathway of the milk-ejection reflex in the mid-brain of the guinea-pig and rabbit. In these three species therefore, the impulses concerned in oxytocin release appear to ascend through the mid-brain in the spinothalamic tract.

PREFERENTIAL RELEASE OF OXYTOCIN FROM THE NEUROHYPOPHYSIS AFTER ELECTRICAL STIMULATION OF THE AFFERENT PATH OF THE MILK-EJECTION REFLEX IN THE BRAIN OF THE GUINEA-PIG

1968 ◽  
Vol 40 (2) ◽  
pp. 205-214 ◽  
Author(s):  
J. S. TINDAL ◽  
G. S. KNAGGS ◽  
A. TURVEY
Keyword(s):  
Blood Pressure ◽  
Electrical Stimulation ◽  
Guinea Pig ◽  
Arterial Blood Pressure ◽  
Pituitary Stalk ◽  
Milk Ejection ◽  
Arterial Blood ◽  
Milk Ejection Reflex ◽  
The Brain ◽  
Stimulation Of

SUMMARY Discrete portions of the afferent path of the milk-ejection reflex have been explored in the brain of the lactating guinea-pig. Both intramammary pressure and arterial blood pressure were recorded to detect release of oxytocin and vasopressin. It was found that the milk-ejection responses which occurred after electrical stimulation of the pathway in the midbrain and hypothalamus were caused by the release of oxytocin without detectable release of vasopressin. A mixture of oxytocin and vasopressin, in the ratio of approximately 3:1, was released only after electrical stimulation of the rostral tuberal region of the hypothalamus adjacent to the pituitary stalk. It is concluded that the afferent path in the brain of the guinea-pig studied is concerned with the preferential release of oxytocin from the neurohypophysis and that it is the pathway of the milk-ejection reflex.

DETERMINATION OF THE DETAILED HYPOTHALAMIC ROUTE OF THE MILK-EJECTION REFLEX IN THE GUINEA-PIG

1971 ◽  
Vol 50 (1) ◽  
pp. 135-152 ◽  
Author(s):  
J. S. TINDAL ◽  
G. S. KNAGGS
Keyword(s):  
Electrical Stimulation ◽  
Lateral Hypothalamus ◽  
Third Ventricle ◽  
Milk Ejection ◽  
Lateral Direction ◽  
Reflex Pathway ◽  
Oxytocin Release ◽  
Far Lateral ◽  
Milk Ejection Reflex ◽  
Stimulation Of

SUMMARY The effect of various types of surgical damage to the forebrain on the release of oxytocin in response to electrical stimulation of the discrete ascending milk-ejection reflex pathway in the mid-brain was investigated in 99 anaesthetized lactating guinea-pigs. Oxytocin release was measured by comparison of experimental milk-ejection responses with the response to i.v. injection of known amounts of synthetic oxytocin. Removal of the entire telencephalon, including cerebral cortex, hippocampi, amygdalae and forebrain rostral to the hypothalamus, did not affect the subsequent release of oxytocin after electrical stimulation of the pathway in the mid-brain, from which it was concluded that the reflex pathway within the forebrain is entirely diencephalic. Transection of the hypothalamus immediately rostral to the paraventricular (PV) nuclei was without effect, while transection immediately caudal to the PV nuclei blocked the release of oxytocin. Destruction of the PV nuclei by a radiofrequency lesion which spared the supraoptic (SO) nuclei blocked the release of oxytocin. Undercutting both PV nuclei so as to isolate them from the ventral hypothalamus blocked the release of oxytocin. Undercutting the PV nucleus ipsilateral to the stimulated side of the mid-brain blocked the release of oxytocin, while undercutting the contralateral PV nucleus had no effect. The PV nuclei, therefore, lie on the ascending path of the milk-ejection reflex, the SO nuclei do not, and, from the mid-brain forwards, the ascending pathway remains uncrossed. The course of the reflex pathway was traced rostrally from the mesodiencephalic junction by making narrow transverse knife-cuts and determining which cuts reduced or blocked the release of oxytocin after mid-brain stimulation. At this level, the pathway on each side of the brain is represented by separate dorsal and ventral paths and in the present study it was found that the ventral path is more important than the dorsal path in terms of oxytocin release. The ventral path passes forward in the medial forebrain bundle, in the far-lateral hypothalamus, while the dorsal path enters the posterior hypothalamus dorsally in the periventricular region at the top of the third ventricle and impinges on the thalamic reuniens nucleus. Shortly afterwards the dorsal path swings abruptly in the lateral direction to join the ventral path in the lateral hypothalamus. The reunited pathway then moves forward in this position until it is level with the PV nuclei, where it swings dorsomedially to relay with the lateral tip of the ipsilateral PV nucleus, and in doing so intermingles with the descending neurosecretory fibres from this nucleus.

PROBLEMS IN ELECTRICAL STIMULATION OF AFFERENT PATHWAYS FOR OXYTOCIN RELEASE

1971 ◽  
Vol 51 (2) ◽  
pp. 347-358 ◽  
Author(s):  
I. URBAN ◽  
R. L. MOSS ◽  
B. A. CROSS
Keyword(s):  
Milk Ejection ◽  
Unit Recording ◽  
Afferent Pathways ◽  
Present Evidence ◽  
Systematic Exploration ◽  
Oxytocin Release ◽  
Stimulation Experiments ◽  
Milk Ejection Reflex ◽  
Synthetic Oxytocin ◽  
Stimulation Of

SUMMARY Recent investigations in the rabbit have indicated the presence of well-defined afferent nervous pathways for release of neurohypophysial oxytocin. To study these pathways for later use in hypothalamic unit recording, intramammary pressure responses (milk ejection) and arterial pressure were recorded in 45 lactating rabbits with post-pontine brainstem transection. Systematic exploration of the mid-brain tegmentum and ventromedial forebrain areas was carried out with a bipolar stimulating electrode. Release of oxytocin, shown by milk-ejection responses similar to those evoked by a 1–2 mu. synthetic oxytocin occurring in the absence of detectable pressor effects, was recorded in less than half the animals. The location of positive stimulation sites was very variable between animals and reproducibility of responses from the same site was poor. It is concluded that present evidence does not support a discrete afferent path in the mid-brain for the milk-ejection reflex and a possible explanation for the inconstant results of stimulation experiments is suggested.

THE BLOOD LEVELS OF OXYTOCIN DURING SUCKLING AND HAND-MILKING IN THE GOAT WITH SOME OBSERVATIONS ON THE PATTERN OF HORMONE RELEASE

1972 ◽  
Vol 52 (1) ◽  
pp. 177-188 ◽  
Author(s):  
A. S. McNEILLY
Keyword(s):  
Relative Effectiveness ◽  
Large Degree ◽  
Blood Levels ◽  
Hormone Release ◽  
Early Lactation ◽  
Milk Ejection ◽  
Blood Samples ◽  
Conditioning Period ◽  
Oxytocin Release ◽  
Milk Ejection Reflex

SUMMARY Thirty-six series of serial jugular blood samples were collected from 12 goats during suckling during the first 3 weeks of lactation and the transient appearance of oxytocin (5–86 μu./ml plasma) was detected in 24 of the series. Blood oxytocin was assayed on the lactating guinea-pig mammary gland. Forty series of serial blood samples were also collected from 12 goats during hand-milking over the first 6 weeks of lactation and the transient appearance of oxytocin (5–160 μu./ml plasma) was observed in 25 of these. The results indicated that: (1) oxytocin may be released at any time during the suckling or milking process; (2) in only 16% of experiments where oxytocin was released and 5·6% of all experiments investigated could a conditioned release of oxytocin be induced in goats before suckling and in no case before hand-milking despite a vigorous and prolonged conditioning period; (3) there is a large degree of variability in the pattern of oxytocin release between animals and between individual suckling and milking episodes in the same animal; (4) suckling and hand-milking are equally effective in causing the release of oxytocin; (5) stimuli arising during various stages of the suckling and hand-milking routines may be assigned a figure indicative of the relative effectiveness of these stimuli in terms of percentage probability in causing oxytocin release; (6) there is a greater probability of oxytocin release occurring before suckling than before hand-milking; (7) there is a very marked similarity in the pattern of oxytocin release both during and after teat stimulation in response to suckling and milking stimuli; (8) there is a greater probability of oxytocin being released in response to hand-milking during early lactation than during late lactation; (9) the milk-ejection reflex in the goat does not appear to be important for the achievement of normal milk yields during suckling or hand-milking.

MESENCEPHALIC AREAS CONTROLLING PULSATILE OXYTOCIN RELEASE IN THE SUCKLED RAT

1981 ◽  
Vol 91 (2) ◽  
pp. 233-244 ◽  
Author(s):  
T. S. JUSS ◽  
J. B. WAKERLEY
Keyword(s):  
Medial Geniculate Body ◽  
Milk Ejection ◽  
Ventral Tegmentum ◽  
Irregular Pattern ◽  
Oxytocin Release ◽  
Medial Geniculate ◽  
Radiofrequency Lesions ◽  
Milk Ejection Reflex ◽  
Bilateral Lesions ◽  
And Control

Experiments were performed on anaesthetized lactating rats to investigate the effects of radiofrequency lesions of the mesencephalon on the milk-ejection reflex. In lesioned and control rats, intramammary pressure recordings were used to estimate oxytocin release (number and relative amplitude of the intermittent milk-ejection responses) during a 3-h suckling test with ten pups. Bilateral lesions (diameter 0·5–1·5 mm) of the lateral tegmentum (near the brachium of the inferior colliculus and medial geniculate body) seriously disrupted the milk-ejection reflex, reducing the number of rats ejecting milk (two out of ten v. all 12 controls, P<0·001) and the amount of oxytocin they released (1·35±0·35 (s.e.m.) v. 15·52±2·19 mu. for controls, P<0·05). Unilateral lesions of the lateral tegmentum also impaired milk ejection and, if the suckling stimulus was restricted only to the contralateral nipples, oxytocin release was virtually abolished. Bilateral lesions placed more medially in the intermediate tegmentum were far less disruptive (eight out of nine rats ejected milk), though the amount of oxytocin released in this group (8·64±1·88 mu.) was still significantly (P<0·05) lower than controls. All rats with lesions of the central grey (nine) or ventral tegmentum (eight) displayed reflex milk ejection, as did those with multiple lesions of the tectum, central grey and ventral tegmentum (seven); in these three groups the amounts of oxytocin released (13·88±2·68, 13·10±1·90 and 11·04±1·95 mu. respectively) did not differ significantly from controls. Damage to the ventral tegmentum produced an irregular pattern of milk ejection characterized by occasional abnormally short (<2 min) milk-ejection intervals, though the overall number of responses in 3 h was less than that of controls (20·83±1·82 v. 14·50±1·30 mu., P<0·05). In conclusion, these results delineate two mesencephalic areas of particular importance in the milk-ejection reflex: (a) the lateral tegmentum, which appears to be concerned with transmission of the suckling stimulus from the contralateral nipples and is indispensable for oxytocin release, and (b) the ventral tegmentum which, although not an essential component of the reflex, may contribute to the timing of the intermittent milk-ejection responses.

EFFECT OF ETHANOL ON UTERINE ACTIVITY DURING SUCKLING IN POST-PARTUM WOMEN

1968 ◽  
Vol 58 (1) ◽  
pp. 133-141 ◽  
Author(s):  
Gorm Wagner ◽  
Anna-Riitta Fuchs
Keyword(s):  
Post Partum ◽  
Blood Alcohol Concentration ◽  
Alcohol Concentration ◽  
Target Organ ◽  
Release Mechanism ◽  
Blood Alcohol ◽  
Milk Ejection ◽  
Oxytocin Release ◽  
Milk Ejection Reflex ◽  
Prior Administration

ABSTRACT Previous experiments indicated that in the rabbit, prior administration of ethyl alcohol inhibits the release of oxytocin elicited by suckling. According to preliminary studies, the same applies also in the human. In the present studies, the effect of ethanol on the milk-ejection reflex in post-partum women was investigated more thoroughly. The milk-ejection reflex was induced by suckling of the infant. The uterine response, recorded by external tocography, was used as a measure of the oxytocin release. Alcohol was administered by mouth as whisky or brandy in suitable dilutions in amounts varying from 0.5 to 1.1 g/kg body weight. By comparison of the uterine response to endogenous (released) and exogenous (injected) oxytocin, it was estimated that about 100–250 mU oxytocin are released by the suckling stimulus in the early puerperium. When alcohol was administered before the application of the stimulus, the release of oxytocin was partially or completely inhibited, but the uterus continued to respond to exogenous oxytocin. As shown previously in the rabbit, the effect of alcohol must thus be on the central release mechanism of oxytocin and not on the peripheral response of the target organ to oxytocin. The degree of inhibition of the oxytocin release was dependent on the alcohol concentration in the blood. With an average blood alcohol concentration of 0.07 per cent the uterine response to suckling during one nursing period was less than half of that observed under normal conditions.

Effect of stimulation intensity on oxytocin release before, during and after machine milking

2003 ◽  
Vol 70 (3) ◽  
pp. 349-354 ◽  
Author(s):  
Daniel Weiss ◽  
Alen Dzidic ◽  
Rupert M Bruckmaier
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Threshold Level ◽  
Flow Profile ◽  
Milk Ejection ◽  
Machine Milking ◽  
Milk Flow ◽  
Oxytocin Release ◽  
Stimulation Period ◽  
Stimulation Of

Release of oxytocin (OT) is essential for milk ejection in dairy cows (Lefcourt & Akers, 1983; Bruckmaier & Blum, 1998). During milk ejection, alveolar milk is shifted into the cistern, which causes an increase of intracisternal pressure (Bruckmaier et al. 1994). To initiate maximum milk ejection at the start of milking, increasing OT concentration beyond a threshold level is sufficient (Schams et al. 1983). Increasing OT concentration beyond this threshold has no additional effect on intracisternal pressure, i.e., milk ejection (Bruckmaier et al. 1994). Stimulatory effects of milking by hand or by machine or by suckling are well documented (Gorewit et al. 1992; Bar-Peled et al. 1995; Tancin et al. 1995; Bruckmaier & Blum, 1996). At the start of milking, stimulatory effects of machine milking without pre-stimulation or with a manual pre-stimulation and subsequent machine milking cause the release of comparable amounts of OT (Gorewit & Gassman, 1985; Mayer et al. 1985; Bruckmaier & Blum, 1996), whereas the timing of the applied pre-stimulation is important for the shape of the milk flow curve. Should the pre-stimulation period be too short, or absent altogether, the start of the main milk flow is delayed resulting in a bimodal milk flow profile (Bruckmaier & Blum, 1996). Furthermore, the stimulation of only one teat causes an OT release similar to that caused by stimulation of all four teats (Bruckmaier et al. 2001). However, milk production is greater for hand milking or suckling than for machine milking, possibly owing to higher OT concentrations (Gorewit et al. 1992; Bar-Peled et al. 1995).

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.

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