Central inhibitory effects of muscimol and bicuculline on the milk ejection reflex in the anaesthetized rat

1995 ◽  
Vol 485 (3) ◽  
pp. 873-873
Keyword(s):  
Inhibitory Effects ◽  
Milk Ejection ◽  
Milk Ejection Reflex ◽  
Anaesthetized Rat

THE MILK-EJECTION REFLEX OF THE RAT: A 20- TO 40-FOLD ACCELERATION IN THE FIRING OF PARAVENTRICULAR NEURONES DURING OXYTOCIN RELEASE

1973 ◽  
Vol 57 (3) ◽  
pp. 477-493 ◽  
Author(s):  
J. B. WAKERLEY ◽  
D. W. LINCOLN
Keyword(s):  
Electrical Activity ◽  
Milk Ejection ◽  
Unit Recording ◽  
Natural Stimulus ◽  
Spike Discharge ◽  
Oxytocin Release ◽  
Milk Ejection Reflex ◽  
Conscious Animals ◽  
Explosive Acceleration ◽  
Anaesthetized Rat

SUMMARY Antidromically-identified paraventricular (PV) neurones were studied in the anaesthetized rat during milk ejection (ME) evoked by the natural stimulus provided by the suckling young. An intermittent pattern of ME was observed, though the ME interval was slightly longer (10–20 min) in the doe during unit recording than in unoperated or conscious animals (5–15 min). PV neurones displayed a steady background of spike discharge in both the non-lactating rat and lactating rat during suckling. The firing rates ranged from 0 to 9·4 spikes/s and were exponentially distributed with 32% of the units firing at <1 spike/s. Phasic patterns of discharge were seen in 18% of the units. Fifty-eight per cent of the PV units displayed a stereotyped and explosive acceleration in spike activity some 15–20 s before the rise in intramammary pressure at ME. The peak firing rate during this brief (2–4 s) response was in the range of 24–84 spikes/s. A prominent after-inhibition was then displayed by these responsive units, though this second component of the response was variable in duration (7–56 s). The electrical activity of the remaining units, including all the cells with phasic discharge, was not correlated with ME. There was no apparent change in the intensity of the suckling stimulus at the time of PV activation, i.e. 15–20 s before ME. Secondly, the activity of the PV neurones was not influenced by the rise in the intramammary pressure and the increased sucking of the pups at the time of ME. Simulation of an individual ME was obtained with both 1 mu. exogenous oxytocin, i.v., and electrical stimulation of the neurohypophysis (50 pulses/s for 4 s). The latencies to ME ranged from 7–14 s and 11–23 s, respectively. In conclusion, an explosive increase in the electrical activity of PV neurones precipitates the release of oxytocin at ME.

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

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

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
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