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  • 1
    Electronic Resource
    Electronic Resource
    Reproducible increases in intramammary pressure after spinal cord stimulation in lactating rats (1984)
    Springer
    Experimental brain research 55 (1984), S. 313-316 
    Details
    ISSN: 1432-1106
    Keywords: Milk-ejection ; Spinal cord ; Stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intramammary pressure was recorded in anaesthetized lactating rats during electrical stimulation of the anterolateral pathways in the T12/L1 region of the spinal cord. In 18 rats, electrical stimulation at 10 Hz or more for 10–30 s caused a reproducible increase in intramammary pressure. The mammary gland responses were similar to those resulting from stimulation of the neurohypophysis with the same parameters, and were eliminated after complete destruction of the neural stalk; they were not associated with any consistent change in blood pressure. In 3 rats, a mammary gland response to spinal cord stimulation was obtained only after administration of the β-adrenergic blocker, propranolol, which facilitates suckling-induced reflex milk-ejections. These results suggest that spinal cord stimulation can cause the release of oxytocin; the functional significance of such a release is discussed in relation to the milk-ejection reflex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237281
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  • 2
    Electronic Resource
    Electronic Resource
    Electrophysiological evidence for connections between septal neurones and the supraoptic nucleus of the hypothalamus of the rat (1981)
    Springer
    Experimental brain research 42 (1981), S. 260-268 
    Details
    ISSN: 1432-1106
    Keywords: Septum ; Supraoptic nucleus ; Vasopressin ; Oxytocin ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to see whether septal neurones are connected to the hypothalamic neurones secreting vasopressin or oxytocin, neurones in different regions of the septum were recorded during electrical stimulation of the supraoptic nucleus. The position of the stimulating electrode within the latter was verified using lactating rats in which milk ejections could be induced by a train of electrical pulses applied to the nucleus. The responses of septal neurones to single pulse stimulation were then analysed by post-stimulus time histograms. In the septum ipsilateral to the site of stimulation, 42% of the neurones were antidromically invaded, 20% were orthodromically excited and 21% were inhibited following supraoptic stimulation. In the contralateral septum, 2% of the cells tested were antidromically invaded, 3% were excited and 16% inhibited. In the medial septum, 14% of the neurones were orthodromically excited, and 48% were inhibited. These results provide electrophysiological evidence for direct connections between septal neurones and the ipsilateral supraoptic nucleus of the hypothalamus, and give further support to the hypothesis of a septal influence on the activity of vasopressin- or oxytocin-releasing cells in the magnocellular system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237493
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  • 3
    Electronic Resource
    Electronic Resource
    Sleep is not a prerequisite for the milk ejection reflex in the pig (1981)
    Springer
    Experimental brain research 43 (1981), S. 107-110 
    Details
    ISSN: 1432-1106
    Keywords: Suckling ; Pig ; Milk ejection ; Sleep ; EEG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electroencephalographic and electromyographic activities were recorded together with variations in intramammary pressure in unanaesthetized lactating sows during suckling. During each suckling period, milk ejection resulted in a sudden and brief rise in intramammary pressure. From the onset of suckling to the beginning of milk ejection, polygraphic recordings as well as observations of behaviour revealed that the sow was invariably in a state of arousal. This suggests that, unlike what has been proposed for the rat, sleep is not a necessary component of the milk ejection reflex in the pig.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238817
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical activity of septal neurones during suckling and the milk ejection reflex in the lactating rat (1982)
    Springer
    Experimental brain research 47 (1982), S. 203-208 
    Details
    ISSN: 1432-1106
    Keywords: Septum ; Supraoptic nucleus ; Oxytocin ; Milk ejection ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular recordings from neurones in the lateral septum were performed in urethane anaesthetised lactating rats to study the eventual role of the septum in the control of suckling-induced oxytocin release. The connections of these neurones with the supraoptic nucleus, which contains cells secreting oxytocin, were assessed electrophysiologically by single pulse stimulation of the ipsilateral supraoptic nucleus. The neurones were thus classified into four categories: antidromically activated, orthodromically activated or inhibited, and unresponsive neurones. One hundred septal neurones were recorded in animals not exposed to suckling. A second group of 40 cells were analysed during suckling and one or more reflex milk ejections. The mean firing rates of each category of septal neurone did not differ significantly during suckling from the values observed in the absence of suckling. During suckling, almost all the recorded septal cells showed no significant alteration in their level of firing in relation to milk ejections. Two neurones presented an activation in the period between two milk ejections that seemed related to arousal. One neurone was clearly inhibited at the time of milk ejection. Our observations suggest that the septum does not represent an essential component of the pathways necessary for the milk ejection reflex induced by suckling, although it could exert an inhibitory action modulating either the intervals between two successive milk ejections, or the amount of oxytocin released.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239379
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  • 5
    Electronic Resource
    Electronic Resource
    The Glutamatergic Innervation of Oxytocin- and Vasopressin-secreting Neurons in the Rat Supraoptic Nucleus and its Contribution to Lactation-induced Synaptic Plasticity (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 8 (1996), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present ultrastructural study analysed the distribution of glutamatergic synapses on oxytocin- and vasopressin-secreting neurons in the rat supraoptic nucleus (SON) after post-embedding immunogold labelling for glutamate and GABA, oxytocin or vasopressin. About 20% of SON axo—somatic synapses were enriched in glutamate immunoreactivity, visible over synaptic-like vesicles, mitochondria and synaptic densities. Double labelling for glutamate and GABA showed that putative glutamatergic terminals were distinct from GABAergic terminals. In ultrathin sections stained for glutamate and either oxytocin or vasopressin, the proportion of glutamatergic synapses was similar on oxytocinergic and vasopressinergic somata in virgin rats under basal conditions of peptide release as well as in lactating rats, in which oxytocin secretion is enhanced. Cross-sectional soma areas were significantly increased in lactating rats: oxytocinergic profiles were, on average, ˜40% larger than in virgin rats. However, the incidence of axo—somatic glutamatergic synapses (assessed as mean number of synapses per 100 μm of plasmalemma or proportion of somatic surface apposed to synaptic active zones) did not diminish, indicating that there was a compensatory increase of synapses during lactation. Also, we found an increase in the number of glutamatergic terminals making synaptic contact simultaneously onto two or more oxytocinergic elements in the same plane of section. Our observations therefore indicate that SON oxytocinergic and vasopressinergic neurons are innervated to a similar extent by a relatively large proportion of glutamatergic synapses. They reveal, moreover, that glutamatergic afferents participate in the lactation-induced synaptic plasticity of the oxytocinergic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1996.tb01600.x
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  • 6
    Electronic Resource
    Electronic Resource
    Visualization of local afferent inputs to magnocellular oxytocin neurons in vitro (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We recently showed that oxytocin (OT) neurons in organotypic slice cultures obtained from postnatal rat hypothalamus display complex patterns of electrical activity, similar to those of adult magnocellular OT neurons in vivo. Here we used such cultures to investigate the identity and, in particular, the origin of afferent inputs responsible for this activity. Multiple immunostaining with light and confocal microscopy showed that the somata and dendrites of oxytocinergic neurons were contacted by numerous synapses, visualized by their reaction to the synaptic markers, synaptophysin or synapsin. Many were GABAergic, displaying immunoreactivities for glutamic acid decarboxylase or γ-aminobutyric acid (GABA); others were enriched in glutamate immunoreactivity. Such afferents presumably arose from GABA- or glutamate-immunoreactive neurons, respectively, with distinct and characteristic morphologies and topographies. A few dopaminergic boutons (tyrosine hydroxylase- or dopamine-immunopositive) impinged on OT neurons; they arose from dopamine-positive neurons located along the third ventricle. No noradrenergic profiles were detected. Despite the presence of choline acetyl-transferase (ChAT)-immunoreactive neurons, there were no cholinergic contacts. Lastly, we found oxytocinergic synapses, identified by immunoreaction for OT-related neurophysin and synapsin, contacting OT somata and dendrites.Our observations thus demonstrate that inhibitory and excitatory inputs to OT neurons derive from local intrahypothalamic GABA and glutamate neurons, in close proximity to the neurons. They also reveal that OT neurons are innervated by hypothalamic dopaminergic neurons. Finally, they confirm the existence of homotypic OT synaptic contacts which derive from local OT neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1999.00620.x
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  • 7
    Electronic Resource
    Electronic Resource
    Development of Oxytocinergic Neurons in Monolayer Cultures Derived from Embryonic, Fetal and Postnatal Rat Hypothalami (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 4 (1992), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Monolayer cultures from hypothalami of embryonic, fetal and postnatal rats were established to study the development of oxytocin-secreting neurons in vitro. Particular culture conditions, known to enhance the survival and growth of different types of neural cells in vitro, were used to investigate the conditions necessary for the appearance and survival of these peptide-producing cells in culture. They included increasing the concentration of potassium in the culture milieu and/or the addition of triiodothyronine (T3). The use of immunocytochemical procedures with a monoclonal antibody that recognizes oxytocin-associated neurophysin (NP-OT) and polyclonal antibodies specific for oxytocin permitted us to identify the neurons. In cultures derived from embryonic (E16-E17) hypothalami, no NP-OT- or oxytocin-positive neurons were detected and their appearance could not be provoked by increasing extracellular potassium concentration or by administration of T3. On the other hand, in cultures obtained from fetal (E18-E19) rat hypothalami, a few neurons showed immunoreactivity for NP-OT (but not for oxytocin); the immunoreactivity was localized essentially in somata and proximal portions of neurites. When 108 M T3 was included in the culture medium, there were cells showing immunoreactivity not only for NP—OT, but also for oxytocin, visible in somata and in dendritic- and axonal-like processes. In comparison, T3 did not influence the total number of neurons developing in these cultures. Lastly, in cultures derived from young postnatal (PO—P2) rat hypothalami, NP—OT- and oxytocin-immunopositive neurons were found regularly; their appearance did not require any special pretreatment of the cultures. In all cultures, high extracellular potassium concentration (25 mM) resulted in a general improvement in the survival of neurons but did not induce the appearance of more oxytocin-immunoreactive cells. Our observations support in vivo results showing that although presumptive oxytocin-producing cells appear early in the development of the hypothalamus, their maturation, and in particular, their ability to produce oxytocin, occurs late at the time of birth. A factor that selectively enhances their differentiation, is the thyroid hormone, T3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1992.tb00190.x
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  • 8
    Electronic Resource
    Electronic Resource
    Activity of phasic neurosecretory cells during haemorrhage (1975)
    [s.l.] : Nature Publishing Group
    Nature 258 (1975), S. 82-84 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Table 1 Changes in the activity quotient and intraburst frequency of phasic neurosecretory cells during blood removal and blood replacement Control values Change during blood removal Change during blood replacement Time from start (min) Activity quotient (Mean ±s.e.) Intraburst ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/258082a0
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of neonatal capsaicin treatment on the sensory innervation of the nipple and on the milk ejection reflex in the rat (1988)
    Springer
    Experimental brain research 73 (1988), S. 32-38 
    Details
    ISSN: 1432-1106
    Keywords: Neonatal capsaicin ; Horseradish peroxidase-wheat germ agglutinin (HRP-WGA) ; Transganglionic transport ; Nipple ; Spinal cord ; Pregnancy ; Lactation ; Milk ejection reflex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Much of the sensory innervation of the nipple is provided by fibers of small calibre (Aδ and C). In order to determine the contribution of unmyelinated C-fibers to this innervation and to the physiology of lactation, mammary afferents were studied in rats that had succeeded in lactating after neonatal treatment with capsaicin, a neurotoxin which selectively destroys C-fibers. After subcutaneous injection of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) into the nipple of capsaicintreated lactating rats, cell counts and surface area estimates of peroxidase-labelled and unlabelled cells were made in the corresponding dorsal root ganglia (DRG) and compared to values obtained in untreated lactating females that had received similar tracer injections. The segmental distribution of HRP-labelled primary sensory neurons in the capsaicintreated rats was similar to that in untreated controls, but the number of labelled cells was significantly reduced at each segmental level. This reduction reflected a marked decrease in C-fibers, since there was a striking reduction in the number of small HRP-labelled and unlabelled cell bodies in the DRG and unmyelinated fibers in the dorsal roots. Peroxidase labelling within the dorsal horn of capsaicin-treated rats was also substantially diminished. About 40% of the females that had been treated neonatally with capsaicin gave birth and lactated. Although the average weight gain of their litters was retarded with respect to that of litters of untreated controls, the milk ejection reflex appeared to function normally. Our observations thus indicate that although C-fibers are an important component of the sensory innervation of the nipple, their destruction early in postnatal development is not sufficient to impair reflex milk ejection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00279658
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  • 10
    Electronic Resource
    Electronic Resource
    Release of oxytocin within the supraoptic nucleus during the milk ejection reflex in rats (1989)
    Springer
    Experimental brain research 76 (1989), S. 593-602 
    Details
    ISSN: 1432-1106
    Keywords: Push-pull perfusion ; Supraoptic nucleus ; Oxytocin ; Suckling ; Milk ejection ; Osmotic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To investigate the hypothesis that oxytocin may be released within the magnocellular nuclei in vivo, push-pull cannula perfusions were performed in anaesthetized lactating rats in one supraoptic nucleus of the hypothalamus while recording the intramammary pressure and/or the electrical activity of oxytocin cells in the contralateral supraoptic nucleus. Oxytocin content was measured in samples collected over 15 min, under various conditions: 1) with no stimulation; 2) during suckling and suckling-induced reflex milk ejections; 3) during electrical stimulation of the neurohypophysis by trains of pulses that mimicked oxytocin cell bursts; 4) under osmotic stimulation by i.p. injection of 2 ml of 1.5 M NaCl to evoke a tonic and sustained oxytocin release from the neurohypophysis. Oxytocin release within the supraoptic nucleus increased significantly during the milk ejection reflex and, to a lesser extent, during burst-like electrical stimulation of the neurohypophysis. In suckled rats, the increase started before the first reflex milk ejection occurred. There was no apparent correlation between the amount of oxytocin in the perfusates and the number of milk ejections and oxytocin cell bursts occurring during each perfusion period. The amount of oxytocin in the perfusates further increased during facilitation of the milk ejection reflex by intraventricular injections of oxytocin or its analogue, isotocin. When suckling failed to evoke the milk ejection reflex, there was no change in intra-supraoptic oxytocin release. There was also no change after osmotic stimulation. When the push-pull cannula was positioned outside the supraoptic nucleus, there was no increase in the amount of oxytocin during the three types of stimulation tested. These results provide evidence for an endogenous release of oxytocin within the magnocellular nuclei in lactating rats. It is suggested that the increase in such a release induced by suckling is likely to be a pre-requisite for the onset and the maintenance of the characteristic intermittent bursting electrical activity of oxytocin cells leading to milk ejections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248916
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