Sleep is not a prerequisite for the milk ejection reflex in the pig

1981 ◽  
Vol 43 (1) ◽  
Author(s):  
D.A. Poulain ◽  
F. Rodriguez ◽  
F. Ellendorff
Keyword(s):  
Milk Ejection ◽  
Milk Ejection Reflex

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.

scholarly journals Neuroendocrine Control of the Milk Ejection Reflex

1983 ◽  
Vol 66 (10) ◽  
pp. 2226-2235 ◽  
Author(s):  
Gordon T. Goodman ◽  
Clark E. Grosvenor
Keyword(s):  
Milk Ejection ◽  
Neuroendocrine Control ◽  
Milk Ejection Reflex

Effects of Central GABAB Receptor Modulation upon the Milk Ejection Reflex in the Rat

1996 ◽  
Vol 63 (4) ◽  
pp. 368-376 ◽  
Author(s):  
Daniel L. Voisin ◽  
Allan E. Herbison ◽  
Chris Chapman ◽  
Dominique A. Poulain
Keyword(s):  
Milk Ejection ◽  
Receptor Modulation ◽  
Milk Ejection Reflex

Reappraisal of the influence of mammary distension on the frequency of milk ejection in the rat

1985 ◽  
Vol 105 (1) ◽  
pp. 127-132
Author(s):  
C. M. Riggs ◽  
R. C. Sutherland ◽  
J. B. Wakerley
Keyword(s):  
Mammary Glands ◽  
Relative Amplitude ◽  
Milk Ejection ◽  
Behavioural Responses ◽  
Per Se ◽  
Milk Ejection Reflex

ABSTRACT Experiments were performed to reinvestigate the importance of mammary engorgement for activation of the milk-ejection reflex in the rat. Reflex milk ejection (measured by intramammary pressure recordings during a 2-h suckling test under anaesthesia) was compared in rats with engorged mammary glands (15-h separation from the pups, followed by sham-removal of milk) and in rats with drained mammary glands (15-h separation, followed by milk removal using a foster litter and exogenous oxytocin). In experiment 1, multiple small (2 mu.) doses of oxytocin were used for milk removal: these were effective in emptying the mammary glands and caused no subsequent impairment or change in sensitivity of the mammary response to oxytocin. Using this draining procedure, no significant differences were observed in either the number or relative amplitude of the milk ejections, or the occurrence of pup stretch reactions between engorged and drained rats. Similar results were seen in experiment 2, where an identical draining protocol was used, but the rats were pretreated with propranolol before the suckling test. In experiment 3, large (250 mu.) oxytocin doses were used for milk removal, as in previous studies. Again mammary draining had no effect on milk ejection in a subsequent suckling test (with propranolol pretreatment). However, the number of stretch reactions shown by the pups was significantly (P < 0·001) reduced from 8·6 ± 1·4/2 h to 1·9 ± 0·6/2 h. This effect probably related to long-term impairment of the oxytocin response of the mammary glands following the draining procedure, and could not be attributed to the draining per se. The dissociation of milk ejections and pup behavioural responses using this method of draining the glands explains previous reports, based on behavioural observations, that mammary draining profoundly disrupts milk ejection. It is concluded that mammary engorgement in fact has little influence on the activation of the milk-ejection reflex in the rat. J. Endocr. (1985) 105, 127–132

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.

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