Mesencephalic Areas Controlling Pulsatile Oxytocin Release in the Suckled Rat

Juss, TS; Wakerley, J. B.

doi:10.1677/joe.0.0910233

Cited by 61 publications

(34 citation statements)

References 19 publications

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“…The question that then arises is whether the neural impulses might already have been synchronized by some gating mechanism. This possibility has been suggested by various results: lesions of the rat ventral tegmentum probably including B9 serotonin neurones (Juss & Wakerley, 1981) or i.c.v. injections of serotonin and serotonergic antagonists disturbed the regularity of burst or milk ejection patterns without modifying their amplitudes.…”

Section: Synchronization Of Oxytocin Cellsmentioning

confidence: 93%

Paired recordings from supraoptic and paraventricular oxytocin cells in suckled rats: recruitment and synchronization.

Belin¹,

Moos²

1986

The Journal of Physiology

160

108

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SUMMARY1. Oxytocin cells in the paraventricular (p.v.) and contralateral supraoptic (s.o.) nuclei were pair-recorded (with two micro-electrodes) in suckled rats after being anaesthetized with urethane (1-2 g/kg), to study (a) the synchronization of their neurosecretory bursts, (b) the importance of cell recruitment and (c) their firing characteristics. The synchronization of paired bursts was determined by measuring the onset time-lag (time in milliseconds between the onset of two corresponding bursts) and the maximum firing time-lag (time in milliseconds between the two shortest interspike intervals for the corresponding bursts). For each cell, the characteristics studied were: the background activity and the frequency and amplitude (total number of spikes) of the neurosecretory bursts.2. All paired p.v.-s.o. cells recorded were activated simultaneously 12-18 s before each milk ejection. The onset of a burst could vary either way, up to 680 ms, in relation to the other (mean onset time-lag was 206+ 18 ms; n = 85) but the maximum activation periods fitted more closely, the mean maximum firing time-lag being 122+ 14 ms (n = 64). Both parameters varied randomly, in duration and order (a) from one pair of cells to another, (b) from one pair of bursts to another for successive bursts of a given pair of cells and (c) independently, whether the cells were in the p.v. or the s.o. nucleus. However, in most cases, the neurosecretory burst with the highest amplitude began and reached its peak firing rate before the corresponding burst from the other cell.3. Cell recruitment was observed when the milk ejection reflex began, for both the p.v. and the s.o. cells. The bursts of the non-responsive cells developed progressively with the reflex, but, as soon as a cell was recruited, all its successive bursts were simultaneous with those of the first-recruited oxytocin cells.4. During a regular pattern of milk ejections, the mean background activity of sixty p.v. cells (3-1+0±2 spikes/s) was significantly higher than that of their s.o.

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Section: Synchronization Of Oxytocin Cellsmentioning

confidence: 93%

Paired recordings from supraoptic and paraventricular oxytocin cells in suckled rats: recruitment and synchronization.

Belin¹,

Moos²

1986

The Journal of Physiology

160

108

View full text Add to dashboard Cite

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“…At the end of surgery the rat was given an i.v. injection of propranolol (250jug/kg body wt; this dose increases the probability that the milk-ejection reflex will occur in the anaesthetized rat: Juss & Wakerley, 1981). The position of the stimulating electrode was adjusted in steps of 0.1 mm below a depth of 8-5 mm until the increase in intramammary pressure evoked by a train of 90 shocks (50 Hz; 0 75 mA peak-to-peak; matched biphasic pulses; 2 ms pulse width) was maximal, and produced a response similar to that evoked by i.v.…”

Section: Methodsmentioning

confidence: 99%

Regulation of the milk ejection reflex in the rat.

Dyball¹,

Leng²

1986

The Journal of Physiology

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SUMMARY1. Extracellular recordings were made from neurones in or near the supraoptic nucleus in suckled lactating rats under urethane anaesthesia to investigate the mechanism by which the firing of oxytocin cells is synchronized during reflex milk ejection.2. Cells synaptically driven but not antidromically activated by neural stalk stimulation, which thus probably receive an afferent input from supraoptic neurones, were classified as 'regular' or 'bursters' on the basis of their spontaneous electrical activity. The majority (twelve out of eighteen) of synaptically excited cells (o.d. +) were bursters and the majority of inhibited (o.d. -) cells (eleven out of nineteen) were regular, but only one o.d. + burster showed any change of activity (inhibition) before milk ejection.3. Putative oxytocin cells in suckled lactating rats showed a firing pattern between milk-ejection bursts which could not be distinguished from that of putative oxytocin cells in male animals. The mode interspike interval between milk ejections was 47-1 + 3*1 ms (mean + S.E. of mean) compared with 47-3 + 3-3 ms in male rats, and fewer than 1-4 00 of interspike intervals were less than 20 ms in duration. By contrast, within milk-ejection bursts 40 %/O of interspike intervals were in the range 8-20 ins.4. Short trains (10 or 20) of pulses applied to the neural stalk at regular (5 min) intervals, in an attempt to simulate the initial part of the milk ejection burst, failed to trigger bursts. In only 2 of 150 tests was the interval between train and milk-ejection burst less than 10 s, and after the pulse train all but one cell showed reduced activity for 1-3 s. The trains of pulses were however not without effect: they significantly (P< 0-01) enhanced the chance of a milk-ejection burst occurring within the next 2-5 min.5. Our observation that pulse trains do not trigger bursts suggests that local positive feed-back mechanisms are not responsible for orchestrating the activation of oxytocin cells during the milk-ejection reflex. Moreover, because spontaneous firing pattern is the same in lactating and non-lactating rats, we found no evidence that the anatomical changes in the synaptic organization within the supraoptic nuclei in lactation have any influence on the firing of oxytocin cells. It is likely, however, since pulse trains alter the timing of milk ejections, that oxytocin released locally in the region of the supraoptic nucleus can influence reflex milk ejection. The R. E. J. DYBALL AND G. LENG effect may involve a temporary change in the membrane properties of oxytocin cells, and occurs over a longer time scale than is usually associated with neurotransmitter action.

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“…Dubois-Dauphin et al [4,5] suggested that information from the suckling stimulus is relayed at the lateral cervical nucleus, crosses the midline and passes through the lateral tegmentum of the midbrain. At the level of the midbrain, Juss and Wakerley [6] showed that the lateral tegmentum is essential for milk-ejection reflex. Furthermore, they showed that unilateral lesion of this area prevents the response to contralateral suckling, but not ipsilateral suckling.…”

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confidence: 99%

Effects of Unilateral Electrolytic Lesion of the Dorsomedial Nucleus of the Hypothalamus on Milk-ejection Reflex in the Rat

Honda

Higuchi

2010

Journal of Reproduction and Development

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Abstract. The dorsomedial nucleus of the hypothalamus (DMH) has been suggested to be a final relay site for the afferent pathway of milk-ejection reflex (MER). The present experiments were undertaken to examine whether unilateral lesion of the DMH abolished MER induced by unilateral suckling by pups. The unilateral DMHs of urethaneanesthetized lactating rats were electrolytically lesioned. Then 5 pups were applied to nipples ipsilateral or contralateral to the lesioned DMH and the intramammary pressure was monitored to observe the occurrence of MER. The effects of bilateral suckling by 10 pups were also examined. Eighteen of the 29 rats displayed MER during ipsi-or bilateral suckling for about 1 h. Seventeen of these 18 rats did not show MER during contralateral suckling for about 1 h. The remaining rat that showed milk ejection during contralateral suckling had a lesion outside the DMH. In 2 additional rats, extracellular action potentials of single oxytocin (OT) cells located in the supraoptic nucleus ipsilateral to the lesioned DMH were recorded during suckling ipsi-and conralateral to the lesioned DMH. OT cells showed milkejection burst during ipsilateral suckling but not during contralateral suckling. The results suggest that the unilateral DMH receives information of suckling stimuli applied to contralateral nipples. Key words: Dorsomedial hypothalamic nucleus, Milk-ejection burst, Oxytocin neurone, Supraoptic nucleus (J. Reprod. Dev. 56: [98][99][100][101][102] 2010) uring suckling, oxytocin (OT) is released intermittently from the neurohypophysial terminals [1]. Each OT release, shown by an increase of intramammary pressure, is preceded by a synchronized short high-frequency burst of action potentials in most OT cells of the paraventricular (PVN) and supraoptic nucleus (SON) [2]. In spite of many studies on the neural mechanisms controlling such periodic and synchronized activation of OT cells during milk-ejection reflex, the exact mechanisms are still not fully understood.The afferent pathway for the milk-ejection reflex has been extensively studied. In the rat spinal cord, Fukuoka et al. [3] demonstrated that suckling stimulus is conveyed rostrally in the ipsilateral lateral funiculus. 5] suggested that information from the suckling stimulus is relayed at the lateral cervical nucleus, crosses the midline and passes through the lateral tegmentum of the midbrain. At the level of the midbrain, Juss and Wakerley [6] showed that the lateral tegmentum is essential for milk-ejection reflex. Furthermore, they showed that unilateral lesion of this area prevents the response to contralateral suckling, but not ipsilateral suckling. It has also been suggested that the Field of Forel and zona incerta might predominantly mediate transmission of the suckling stimulus from the midbrain to hypothalamic oxytocin neurons [7]. However, a retrograde tracing study by Tribollet et al. [8] showed that neurons in these areas are not labeled following injection of tracer into the SON, which suggests the existence of furthe...

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Mesencephalic Areas Controlling Pulsatile Oxytocin Release in the Suckled Rat

Cited by 61 publications

References 19 publications

Paired recordings from supraoptic and paraventricular oxytocin cells in suckled rats: recruitment and synchronization.

Paired recordings from supraoptic and paraventricular oxytocin cells in suckled rats: recruitment and synchronization.

Regulation of the milk ejection reflex in the rat.

Effects of Unilateral Electrolytic Lesion of the Dorsomedial Nucleus of the Hypothalamus on Milk-ejection Reflex in the Rat

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