1
|
Yaguchi K, Hagihara M, Konno A, Hirai H, Yukinaga H, Miyamichi K. Dynamic modulation of pulsatile activities of oxytocin neurons in lactating wild-type mice. PLoS One 2023; 18:e0285589. [PMID: 37163565 PMCID: PMC10171594 DOI: 10.1371/journal.pone.0285589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 04/27/2023] [Indexed: 05/12/2023] Open
Abstract
Breastfeeding, which is essential for the survival of mammalian infants, is critically mediated by pulsatile secretion of the pituitary hormone oxytocin from the central oxytocin neurons located in the paraventricular and supraoptic hypothalamic nuclei of mothers. Despite its importance, the molecular and neural circuit mechanisms of the milk ejection reflex remain poorly understood, in part because a mouse model to study lactation was only recently established. In our previous study, we successfully introduced fiber photometry-based chronic imaging of the pulsatile activities of oxytocin neurons during lactation. However, the necessity of Cre recombinase-based double knock-in mice substantially compromised the use of various Cre-dependent neuroscience toolkits. To overcome this obstacle, we developed a simple Cre-free method for monitoring oxytocin neurons by an adeno-associated virus vector driving GCaMP6s under a 2.6 kb mouse oxytocin mini-promoter. Using this method, we monitored calcium ion transients of oxytocin neurons in the paraventricular nucleus in wild-type C57BL/6N and ICR mothers without genetic crossing. By combining this method with video recordings of mothers and pups, we found that the pulsatile activities of oxytocin neurons require physical mother-pup contact for the milk ejection reflex. Notably, the frequencies of photometric signals were dynamically modulated by mother-pup reunions after isolation and during natural weaning stages. Collectively, the present study illuminates the temporal dynamics of pulsatile activities of oxytocin neurons in wild-type mice and provides a tool to characterize maternal oxytocin functions.
Collapse
Affiliation(s)
- Kasane Yaguchi
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto, Kyoto, Japan
| | - Mitsue Hagihara
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo, Japan
| | - Ayumu Konno
- Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
- Viral Vector Core, Gunma University Initiative for Advanced Research (GIAR), Maebashi, Gunma, Japan
| | - Hirokazu Hirai
- Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
- Viral Vector Core, Gunma University Initiative for Advanced Research (GIAR), Maebashi, Gunma, Japan
| | - Hiroko Yukinaga
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo, Japan
| | - Kazunari Miyamichi
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo, Japan
| |
Collapse
|
2
|
Tsingotjidou AS. Oxytocin: A Multi-Functional Biomolecule with Potential Actions in Dysfunctional Conditions; From Animal Studies and Beyond. Biomolecules 2022; 12:1603. [PMID: 36358953 PMCID: PMC9687803 DOI: 10.3390/biom12111603] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 10/20/2022] [Accepted: 10/23/2022] [Indexed: 10/13/2023] Open
Abstract
Oxytocin is a hormone secreted from definite neuroendocrine neurons located in specific nuclei in the hypothalamus (mainly from paraventricular and supraoptic nuclei), and its main known function is the contraction of uterine and/or mammary gland cells responsible for parturition and breastfeeding. Among the actions of the peripherally secreted oxytocin is the prevention of different degenerative disorders. These actions have been proven in cell culture and in animal models or have been tested in humans based on hypotheses from previous studies. This review presents the knowledge gained from the previous studies, displays the results from oxytocin intervention and/or treatment and proposes that the well described actions of oxytocin might be connected to other numerous, diverse actions of the biomolecule.
Collapse
Affiliation(s)
- Anastasia S Tsingotjidou
- Laboratory of Anatomy, Histology and Embryology, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, 54 124 Thessaloniki, Greece
| |
Collapse
|
3
|
Yukinaga H, Hagihara M, Tsujimoto K, Chiang HL, Kato S, Kobayashi K, Miyamichi K. Recording and manipulation of the maternal oxytocin neural activities in mice. Curr Biol 2022; 32:3821-3829.e6. [PMID: 35868323 DOI: 10.1016/j.cub.2022.06.083] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 06/07/2022] [Accepted: 06/28/2022] [Indexed: 11/26/2022]
Abstract
Pulsatile release of the hormone oxytocin (OT) mediates uterine contraction during parturition and milk ejection during lactation.1-3 These pulses are generated by the unique activity patterns of the central neuroendocrine OT neurons located in the paraventricular and supraoptic hypothalamus. Classical studies have characterized putative OT neurons by in vivo extracellular recording techniques in rats and rabbits.1,4-10 Due to technical limitations, however, the identity of OT neurons in these previous studies was speculative based on their electrophysiological characteristics and axonal projection to the posterior pituitary, not on OT gene expression. To pinpoint OT neural activities among other hypothalamic neurons that project to the pituitary11,12 and make better use of cell-type-specific neuroscience toolkits,13 a mouse model needs to be developed for the studies of parturition and lactation. We herein introduce viral genetic approaches in mice to characterize the maternal activities of OT neurons by fiber photometry. A sharp photometric peak of OT neurons appeared at approximately 520 s following simultaneous suckling stimuli from three pups. The amplitude of the peaks increased as the mother mice experienced lactation, irrespective of the age of the pups, suggesting the intrinsic plasticity of maternal OT neurons. Based on a mono-synaptic input map to OT neurons, we pharmacogenetically activated the inhibitory neurons in the bed nucleus of the stria terminalis and found the suppression of the activities of OT neurons. Collectively, our study illuminates temporal dynamics in the maternal neural activities of OT neurons and identifies one of its modulatory inputs.
Collapse
Affiliation(s)
- Hiroko Yukinaga
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan
| | - Mitsue Hagihara
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan
| | - Kazuko Tsujimoto
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan
| | - Hsiao-Ling Chiang
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan
| | - Shigeki Kato
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Kazuto Kobayashi
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Kazunari Miyamichi
- Laboratory for Comparative Connectomics, Riken Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan; PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
| |
Collapse
|
4
|
Leithead AB, Tasker JG, Harony‐Nicolas H. The interplay between glutamatergic circuits and oxytocin neurons in the hypothalamus and its relevance to neurodevelopmental disorders. J Neuroendocrinol 2021; 33:e13061. [PMID: 34786775 PMCID: PMC8951898 DOI: 10.1111/jne.13061] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 10/14/2021] [Accepted: 10/30/2021] [Indexed: 11/27/2022]
Abstract
Oxytocin (OXT) neurons of the hypothalamus are at the center of several physiological functions, including milk ejection, uterus contraction, and maternal and social behavior. In lactating females, OXT neurons show a pattern of burst firing and inter-neuron synchronization during suckling that leads to pulsatile release of surges of OXT into the bloodstream to stimulate milk ejection. This pattern of firing and population synchronization may be facilitated in part by hypothalamic glutamatergic circuits, as has been observed in vitro using brain slices obtained from male rats and neonates. However, it remains unknown how hypothalamic glutamatergic circuits influence OXT cell activity outside the context of lactation. In this review, we summarize the in vivo and in vitro studies that describe the synchronized burst firing pattern of OXT neurons and the implication of hypothalamic glutamate in this pattern of firing. We also make note of the few studies that have traced glutamatergic afferents to the hypothalamic paraventricular and supraoptic nuclei. Finally, we discuss the genetic findings implicating several glutamatergic genes in neurodevelopmental disorders, including autism spectrum disorder, thus underscoring the need for future studies to investigate the impact of these mutations on hypothalamic glutamatergic circuits and the OXT system.
Collapse
Affiliation(s)
- Amanda B. Leithead
- Department of PsychiatryIcahn School of Medicine at Mount SinaiNew YorkNYUSA
- Seaver Autism Center for Research and TreatmentNew YorkNYUSA
- Department of NeuroscienceIcahn School of Medicine at Mount SinaiNew YorkNYUSA
- Friedman Brain Institute at the Icahn School of Medicine at Mount SinaiNew YorkNYUSA
| | - Jeffrey G. Tasker
- Neurobiology DivisionDepartment of Cell and Molecular BiologyTulane UniversityNew OrleansLAUSA
| | - Hala Harony‐Nicolas
- Department of PsychiatryIcahn School of Medicine at Mount SinaiNew YorkNYUSA
- Seaver Autism Center for Research and TreatmentNew YorkNYUSA
- Department of NeuroscienceIcahn School of Medicine at Mount SinaiNew YorkNYUSA
- Friedman Brain Institute at the Icahn School of Medicine at Mount SinaiNew YorkNYUSA
- Mindich Child Health and Development Institute at the Icahn School of Medicine at Mount SinaiNew YorkNYUSA
| |
Collapse
|
5
|
Perkinson MR, Kim JS, Iremonger KJ, Brown CH. Visualising oxytocin neurone activity in vivo: The key to unlocking central regulation of parturition and lactation. J Neuroendocrinol 2021; 33:e13012. [PMID: 34289195 DOI: 10.1111/jne.13012] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/22/2021] [Accepted: 07/05/2021] [Indexed: 11/26/2022]
Abstract
During parturition and lactation, oxytocin neurones in the supraoptic and paraventricular nuclei fire high-frequency bursts of action potentials that are coordinated across the entire population. Each burst generates a large pulse of oxytocin release into the circulation to induce uterine contraction for parturition and mammary duct contraction for milk ejection. Bursts are stimulated by cervical stretch during parturition and by suckling during lactation. However, the mechanisms by which these stimuli are translated into episodic bursts are poorly understood, as are the mechanisms that coordinate bursts across the oxytocin neurone population. An elegant series of experiments conducted in the 1980s and 1990s used serial paired recordings to show that oxytocin neurones do not act as a syncytium during bursts; rather, they start each burst within a few hundred milliseconds of each other but with no distinct "leaders" or "followers". In addition to afferent noradrenergic inputs that relay the systemic stimuli to oxytocin neurones, bursts depend on somato-dendritic oxytocin release within the hypothalamus. Hence, bursts are considered to be an emergent property of oxytocin neurones that is bootstrapped by appropriate afferent stimulation. Although much progress was made using traditional electrophysiological recordings in head-fixed anaesthetised animals, research has effectively stalled in the last few decades. However, the emergence of new technologies to monitor neuronal activity in freely-behaving animals has reinvigorated efforts to understand the biology underpinning burst firing in oxytocin neurones. Here, we report the use of fibre photometry to monitor the dynamics of milk ejection bursts in the oxytocin neurone population of freely-behaving mice. This approach will shed light on the neural mechanisms that control the oxytocin bursts underpinning parturition and lactation.
Collapse
Affiliation(s)
- Michael R Perkinson
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| | - Joon S Kim
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| | - Karl J Iremonger
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| | - Colin H Brown
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| |
Collapse
|
6
|
Li D, Liu X, Li T, Wang X, Jia S, Wang P, Wang YF. Involvement of Protein Kinase A in Oxytocin Neuronal Activity in Rat Dams with Pup Deprivation. Neurochem Res 2021; 46:980-991. [PMID: 33611682 DOI: 10.1007/s11064-020-03218-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/20/2020] [Accepted: 12/27/2020] [Indexed: 10/22/2022]
Abstract
Oxytocin (OT) neuronal activity is the key factor for breastfeeding and it can be disrupted by mother-baby separation. To explore cellular mechanisms underlying OT neuronal activity, we studied the role of protein kinase A (PKA) in OT neuronal activity in the supraoptic nucleus (SON) using a rodent model of pup deprivation (PD) Intermittent (IPD) or continuous (CPD) PD significantly reduced suckling duration and number of milk ejections in lactating rats, particularly those with CPD. In Western blots of the SON, PD increased expressions of OT receptor (OTR) and its immediate downstream effectors, Gαq and Gβ subunits, particularly IPD, but reduced the expression of catalytic subunit of PKA (cPKA). In brain slices, inhibition of PKA blocked prostaglandin E2-evoked increase in firing activity including burst firing in OT neurons. In IPD dams, filamentous actin formed ring-like structures in the cytoplasmic region of OT neurons, which was reduced in CPD. Moreover, molecular association between actin and cPKA also reduced in PD dams. Incubation of brain slices with OT reduced the expression of cPKA, which was blocked by pretreatment with atosiban, an antagonist of OTR. These results indicate that PD disrupts OT neuronal activity through dissociating the Gq proteins and PKA in OTR-associated signaling cascade, which couples with reduced interactions between filamentous actin and PKA in OT neurons in the SON. This study highlights that PKA can be a novel target treating abnormal OT neuronal activity and its associated diseases.
Collapse
Affiliation(s)
- Dongyang Li
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
- Department of Physiology, Hainan Medical University, Haikou, China
| | - Xiaoyu Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
| | - Tong Li
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
| | - Xiaoran Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
| | - Shuwei Jia
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
| | - Ping Wang
- Department of Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China
| | - Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, 150081, China.
| |
Collapse
|
7
|
Wang SC, Parpura V, Wang YF. Astroglial Regulation of Magnocellular Neuroendocrine Cell Activities in the Supraoptic Nucleus. Neurochem Res 2020; 46:2586-2600. [PMID: 33216313 DOI: 10.1007/s11064-020-03172-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/02/2020] [Accepted: 11/09/2020] [Indexed: 01/02/2023]
Abstract
Studies on the interactions between astrocytes and neurons in the hypothalamo-neurohypophysial system have significantly facilitated our understanding of the regulation of neural activities. This has been exemplified in the interactions between astrocytes and magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON), specifically during osmotic stimulation and lactation. In response to changes in neurochemical environment in the SON, astrocytic morphology and functions change significantly, which further modulates MNC activity and the secretion of vasopressin and oxytocin. In osmotic regulation, short-term dehydration or water overload causes transient retraction or expansion of astrocytic processes, which increases or decreases the activity of SON neurons, respectively. Prolonged osmotic stimulation causes adaptive change in astrocytic plasticity in the SON, which allows osmosensory neurons to reserve osmosensitivity at new levels. During lactation, changes in neurochemical environment cause retraction of astrocytic processes around oxytocin neurons, which increases MNC's ability to secrete oxytocin. During suckling by a baby/pup, astrocytic processes in the mother/dams exhibit alternative retraction and expansion around oxytocin neurons, which mirrors intermittently synchronized activation of oxytocin neurons and the post-excitation inhibition, respectively. The morphological and functional plasticities of astrocytes depend on a series of cellular events involving glial fibrillary acidic protein, aquaporin 4, volume regulated anion channels, transporters and other astrocytic functional molecules. This review further explores mechanisms underlying astroglial regulation of the neuroendocrine neuronal activities in acute processes based on the knowledge from studies on the SON.
Collapse
Affiliation(s)
- Stephani C Wang
- Division of Cardiology, Department of Medicine, University of California-Irvine, Irvine, CA, USA
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, 35242, USA.
| | - Yu-Feng Wang
- Department of Physiology School of Basic Medical Sciences, Harbin Medical University, 157 Baojian Road, Nangang, Harbin, 150086, China.
| |
Collapse
|
8
|
Li D, Liu X, Liu H, Li T, Jia S, Wang X, Wang P, Qin D, Wang YF. Key Roles of Cyclooxygenase 2-Protein Kinase A-Hyperpolarization-activated Cyclic Nucleotide-gated Channel 3 Pathway in the Regulation of Oxytocin Neuronal Activity in Lactating Rats with Intermittent Pup-Deprivation. Neuroscience 2020; 452:13-25. [PMID: 33137408 DOI: 10.1016/j.neuroscience.2020.10.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 10/09/2020] [Indexed: 12/14/2022]
Abstract
Suckling-evoked pulsatile release of oxytocin (OT) from the posterior pituitary plays a key role in breastfeeding, which relies on burst-like discharges of OT neurons. To explore cellular mechanisms regulating OT neuronal activity, using lactating rats with pup-deprivation (PD) during postpartum day 1-5, we observed the involvement of prostaglandin, cyclic AMP/protein kinase A (PKA) and hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) signaling pathway in OT neuronal activity. PD gradually reduced lactation efficiency. Intermittent PD (IPD) was largely reversed by intranasally-applied OT (IAO) but not by hypodermically-applied OT. IPD caused involution-like histological changes in the mammary glands, increased hypothalamic OT release but did not influence plasma OT concentrations. In the supraoptic nucleus, IPD increased OT receptor (OTR) expressions in OT neurons as well as Gαq subunit, Gβ subunit and cyclooxygenase 2 (Cox-2). These effects except that on Gβ subunit were reversed by IAO. Notably, IPD increased the expression of catalytic subunit of PKA in the SON, specifically in vasopressin neurons but not in OT neurons. In addition, IPD increased the expression of HCN3. IAO partially reversed these changes in the SON. Lastly, blocking HCN3 blocked excitation and burst firing in OT neurons-evoked by prostaglandin E2, a key mediator of OT-evoked burst firing; blocking Cox-2 or PKA reduced the molecular association between OTR and HCN3. Thus, there is a prostaglandin-cAMP/PKA-HCN3 pathway in the regulation of OT neuronal activity. PD disrupts lactation performance through uncoupling OTR and PKA-HCN3 signaling. The reversal effect of IAO highlights its therapeutic potential in PD-evoked hypogalactia.
Collapse
Affiliation(s)
- Dongyang Li
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Xiaoyu Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Haitao Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Tong Li
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Shuwei Jia
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Xiaoran Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Ping Wang
- Department of Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Danian Qin
- Department of Physiology, Shantou University of Medical College, Shantou, China
| | - Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China.
| |
Collapse
|
9
|
Akahoshi N, Handa H, Takemoto R, Kamata S, Yoshida M, Onaka T, Ishii I. Preeclampsia-Like Features and Partial Lactation Failure in Mice Lacking Cystathionine γ-Lyase-An Animal Model of Cystathioninuria. Int J Mol Sci 2019; 20:ijms20143507. [PMID: 31319489 PMCID: PMC6679037 DOI: 10.3390/ijms20143507] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/10/2019] [Accepted: 07/16/2019] [Indexed: 01/01/2023] Open
Abstract
Elevated plasma homocysteine levels are considered as a risk factor for cardiovascular diseases as well as preeclampsia—a pregnancy disorder characterized by hypertension and proteinuria. We previously generated mice lacking cystathionine γ-lyase (Cth) as cystathioninuria models and found them to be with cystathioninemia/homocysteinemia. We investigated whether Cth-deficient (Cth−/−) pregnant mice display any features of preeclampsia. Cth−/− females developed normally but showed mild hypertension (~10 mmHg systolic blood pressure elevation) in late pregnancy and mild proteinuria throughout development/pregnancy. Cth−/− dams had normal numbers of pups and exhibited normal maternal behavior except slightly lower breastfeeding activity. However, half of them could not raise their pups owing to defective lactation; they could produce/store the first milk in their mammary glands but not often provide milk to their pups after the first ejection. The serum oxytocin levels and oxytocin receptor expression in the mammary glands were comparable between wild-type and Cth−/− dams, but the contraction responses of mammary gland myoepithelial cells to oxytocin were significantly lower in Cth−/− dams. The contraction responses to oxytocin were lower in uteruses isolated from Cth−/− mice. Our results suggest that elevated homocysteine or other unknown factors in preeclampsia-like Cth−/− dams interfere with oxytocin that regulates milk ejection reflex.
Collapse
Affiliation(s)
- Noriyuki Akahoshi
- Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan
| | - Hiroki Handa
- Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan
| | - Rintaro Takemoto
- Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan
| | - Shotaro Kamata
- Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan
| | - Masahide Yoshida
- Department of Physiology, Jichi Medical University, Tochigi 329-0498, Japan
| | - Tatsushi Onaka
- Department of Physiology, Jichi Medical University, Tochigi 329-0498, Japan
| | - Isao Ishii
- Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan.
| |
Collapse
|
10
|
Valtcheva S, Froemke RC. Neuromodulation of maternal circuits by oxytocin. Cell Tissue Res 2019; 375:57-68. [PMID: 30062614 PMCID: PMC6336509 DOI: 10.1007/s00441-018-2883-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/03/2018] [Indexed: 12/31/2022]
Abstract
Motherhood in mammals involves tremendous changes throughout the body and central nervous system, which support attention and nurturing of infants. Maternal care consists of complex behaviors, such as nursing and protection of the offspring, requiring new mothers to become highly sensitive to infant needs. Long-lasting neural plasticity in various regions of the cerebral cortex may enable the perception and recognition of infant cues, important for appropriate caregiving responses. Recent findings have demonstrated that the neuropeptide oxytocin is involved in a number of physiological processes, including parturition and lactation and dynamically shaping neuronal responses to infant stimuli as well. Here, we review experience-dependent changes within the cortex occurring throughout motherhood, focusing on plasticity of the somatosensory and auditory cortex. We outline the role of oxytocin in gating cortical plasticity and discuss potential mechanisms regulating oxytocin release in response to different sensory stimuli.
Collapse
Affiliation(s)
- Silvana Valtcheva
- Skirball Institute for Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
- Neuroscience Institute, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
- Department of Otolaryngology, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
- Department of Neuroscience and Physiology, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
| | - Robert C Froemke
- Skirball Institute for Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA.
- Neuroscience Institute, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA.
- Department of Otolaryngology, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA.
- Department of Neuroscience and Physiology, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA.
- Howard Hughes Medical Institute Faculty Scholar, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA.
| |
Collapse
|
11
|
Augustine RA, Seymour AJ, Campbell RE, Grattan DR, Brown CH. Integrative neuro-humoral regulation of oxytocin neuron activity in pregnancy and lactation. J Neuroendocrinol 2018; 30. [PMID: 29323764 DOI: 10.1111/jne.12569] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 01/07/2018] [Indexed: 02/02/2023]
Abstract
Oxytocin is required for normal birth and lactation. Oxytocin is synthesised by hypothalamic supraoptic and paraventricular nuclei neurons and is released into the circulation from the posterior pituitary gland. Under basal conditions, circulating oxytocin levels are relatively constant but during birth and lactation, pulsatile oxytocin release triggers rhythmic contraction of the uterus during birth and milk ejection during suckling. Oxytocin levels are principally determined by the pattern of action potential firing that is, in turn, determined by the interplay between the intrinsic properties of the oxytocin neurons, regulation of their excitability by surrounding glia as well as by synaptic drive from their afferent inputs. During birth and suckling, oxytocin neurons fire high-frequency bursts of action potentials that are coordinated across the population of neurons and these bursts underpin the pulsatile secretion of oxytocin required for normal birth and lactation. Neuroglial regulation of oxytocin neurons changes during pregnancy to favour burst firing. However, these changes still require afferent input activity to drive activity. While it has long been known that noradrenergic inputs to oxytocin neurons are activated during birth and lactation, the involvement of other afferent inputs is less clear. Here, we provide a brief overview of the current understanding of the mechanisms that regulate oxytocin neuron activity during pregnancy and lactation, and focus on recent evidence from our laboratory identifying an input that increases kisspeptin production to excite oxytocin neurons in late pregnancy. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Rachael A Augustine
- Department of Physiology Brain Health Research Centre, Centre for Neuroendocrinology
| | - Alexander J Seymour
- Department of Physiology Brain Health Research Centre, Centre for Neuroendocrinology
| | - Rebecca E Campbell
- Department of Physiology Brain Health Research Centre, Centre for Neuroendocrinology
| | - David R Grattan
- Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - Colin H Brown
- Department of Physiology Brain Health Research Centre, Centre for Neuroendocrinology
| |
Collapse
|
12
|
Abstract
The posterior pituitary gland secretes oxytocin and vasopressin (the antidiuretic hormone) into the blood system. Oxytocin is required for normal delivery of the young and for delivery of milk to the young during lactation. Vasopressin increases water reabsorption in the kidney to maintain body fluid balance and causes vasoconstriction to increase blood pressure. Oxytocin and vasopressin secretion occurs from the axon terminals of magnocellular neurons whose cell bodies are principally found in the hypothalamic supraoptic nucleus and paraventricular nucleus. The physiological functions of oxytocin and vasopressin depend on their secretion, which is principally determined by the pattern of action potentials initiated at the cell bodies. Appropriate secretion of oxytocin and vasopressin to meet the challenges of changing physiological conditions relies mainly on integration of afferent information on reproductive, osmotic, and cardiovascular status with local regulation of magnocellular neurons by glia as well as intrinsic regulation by the magnocellular neurons themselves. This review focuses on the control of magnocellular neuron activity with a particular emphasis on their regulation by reproductive function, body fluid balance, and cardiovascular status. © 2016 American Physiological Society. Compr Physiol 6:1701-1741, 2016.
Collapse
Affiliation(s)
- Colin H Brown
- Brain Health Research Centre, Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
| |
Collapse
|
13
|
Veening JG, de Jong TR, Waldinger MD, Korte SM, Olivier B. The role of oxytocin in male and female reproductive behavior. Eur J Pharmacol 2014; 753:209-28. [PMID: 25088178 DOI: 10.1016/j.ejphar.2014.07.045] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 05/30/2014] [Accepted: 07/24/2014] [Indexed: 01/01/2023]
Abstract
Oxytocin (OT) is a nonapeptide with an impressive variety of physiological functions. Among them, the 'prosocial' effects have been discussed in several recent reviews, but the direct effects on male and female sexual behavior did receive much less attention so far. As our contribution to honor the lifelong interest of Berend Olivier in the control mechanisms of sexual behavior, we decided to explore the role of OT in the present review. In the successive sections, some physiological mechanisms and the 'pair-bonding' effects of OT will be discussed, followed by sections about desire, female appetitive and copulatory behavior, including lordosis and orgasm. At the male side, the effects on erection and ejaculation are reviewed, followed by a section about 'premature ejaculation' and a possible role of OT in its treatment. In addition to OT, serotonin receives some attention as one of the main mechanisms controlling the effects of OT. In the succeeding sections, the importance of OT for 'the fruits of labor' is discussed, as it plays an important role in both maternal and paternal behavior. Finally, we pay attention to an intriguing brain area, the ventrolateral part of the ventromedial hypothalamic nucleus (VMHvl), apparently functioning in both sexual and aggressive behavior, which are at first view completely opposite behavioral systems.
Collapse
Affiliation(s)
- J G Veening
- Department of Psychopharmacology, Division of Pharmacology, University of Utrecht, Utrecht, The Netherlands; Department of Anatomy, Radboud University Medical Center, Nijmegen, The Netherlands.
| | - T R de Jong
- Department of Behavioral and Molecular Neurobiology, University of Regensburg, 93053 Regensburg, Germany
| | - M D Waldinger
- Department of Psychopharmacology, Division of Pharmacology, University of Utrecht, Utrecht, The Netherlands
| | - S M Korte
- Department of Psychopharmacology, Division of Pharmacology, University of Utrecht, Utrecht, The Netherlands
| | - B Olivier
- Department of Psychopharmacology, Division of Pharmacology, University of Utrecht, Utrecht, The Netherlands
| |
Collapse
|
14
|
Brown CH, Bains JS, Ludwig M, Stern JE. Physiological regulation of magnocellular neurosecretory cell activity: integration of intrinsic, local and afferent mechanisms. J Neuroendocrinol 2013; 25:678-710. [PMID: 23701531 PMCID: PMC3852704 DOI: 10.1111/jne.12051] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 01/12/2023]
Abstract
The hypothalamic supraoptic and paraventricular nuclei contain magnocellular neurosecretory cells (MNCs) that project to the posterior pituitary gland where they secrete either oxytocin or vasopressin (the antidiuretic hormone) into the circulation. Oxytocin is important for delivery at birth and is essential for milk ejection during suckling. Vasopressin primarily promotes water reabsorption in the kidney to maintain body fluid balance, but also increases vasoconstriction. The profile of oxytocin and vasopressin secretion is principally determined by the pattern of action potentials initiated at the cell bodies. Although it has long been known that the activity of MNCs depends upon afferent inputs that relay information on reproductive, osmotic and cardiovascular status, it has recently become clear that activity depends critically on local regulation by glial cells, as well as intrinsic regulation by the MNCs themselves. Here, we provide an overview of recent advances in our understanding of how intrinsic and local extrinsic mechanisms integrate with afferent inputs to generate appropriate physiological regulation of oxytocin and vasopressin MNC activity.
Collapse
Affiliation(s)
- C H Brown
- Department of Physiology and Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand.
| | | | | | | |
Collapse
|
15
|
Nonsocial functions of hypothalamic oxytocin. ISRN NEUROSCIENCE 2013; 2013:179272. [PMID: 24967304 PMCID: PMC4045544 DOI: 10.1155/2013/179272] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 04/23/2013] [Indexed: 01/06/2023]
Abstract
Oxytocin (OXT) is a hypothalamic neuropeptide composed of nine amino acids. The functions of OXT cover a variety of social and nonsocial activity/behaviors. Therapeutic effects of OXT on aberrant social behaviors are attracting more attention, such as social memory, attachment, sexual behavior, maternal behavior, aggression, pair bonding, and trust. The nonsocial behaviors/functions of brain OXT have also received renewed attention, which covers brain development, reproduction, sex, endocrine, immune regulation, learning and memory, pain perception, energy balance, and almost all the functions of peripheral organ systems. Coordinating with brain OXT, locally produced OXT also involves the central and peripheral actions of OXT. Disorders in OXT secretion and functions can cause a series of aberrant social behaviors, such as depression, autism, and schizophrenia as well as disturbance of nonsocial behaviors/functions, such as anorexia, obesity, lactation failure, osteoporosis, diabetes, and carcinogenesis. As more and more OXT functions are identified, it is essential to provide a general view of OXT functions in order to explore the therapeutic potentials of OXT. In this review, we will focus on roles of hypothalamic OXT on central and peripheral nonsocial functions.
Collapse
|
16
|
Wang YF, Negoro H, Higuchi T. Lesions of hypothalamic mammillary body desynchronise milk-ejection bursts of rat bilateral supraoptic oxytocin neurones. J Neuroendocrinol 2013; 25:67-75. [PMID: 22849304 DOI: 10.1111/j.1365-2826.2012.02368.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 06/17/2012] [Accepted: 07/27/2012] [Indexed: 11/30/2022]
Abstract
Successful milk ejection depends on a bolus release of oxytocin, which results from the synchronised burst firing of magnocellular oxytocin neurones in several hypothalamic nuclei. Despite extensive studies of the mechanism underlying the burst synchrony of oxytocin neurones in the same nucleus, brain regions controlling burst synchronisation among different nuclei remain elusive. We hypothesised that some structures in the ventroposterior hypothalamus may function as the major component of neural circuits controlling burst synchronisation of bilateral oxytocin neurones. To test this hypothesis, we recorded burst firing of bilateral oxytocin neurones in the two supraoptic nuclei after microsurgical disconnection of different hypothalamic regions in anaesthetised lactating rats. The results obtained showed that the interhemispheric section of the caudal part of the hypothalamus but not the rostral hypothalamus resulted in burst desynchronisation. The difference in burst onset time between paired bursts of bilateral oxytocin neurones was 129.2 ± 34.7 s, which is significantly (P < 0.01) longer than that of sham-lesioned controls (0.24 ± 0.02 s). Hypothalamic lesions leading to the desynchronisation involved the mammillary body, supramammillary nucleus and tuberomammillary nucleus in the ventroposterior hypothalamus. Consistently, electrolytic lesion of the median part of this mammillary body region also desynchronised the burst of bilateral oxytocin neurones and disrupted milk ejections. These results indicate that the mammillary body region is critically involved in the burst synchronisation of bilateral oxytocin neurones during suckling and possibly functions as the major component of a putative synchronisation centre.
Collapse
Affiliation(s)
- Y-F Wang
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA 71103-4228, USA.
| | | | | |
Collapse
|
17
|
González-Mariscal G, Toribio A, Gallegos JA, Serrano-Meneses MA. Characteristics of suckling stimulation determine the daily duration of mother-young contact and milk output in rabbits. Dev Psychobiol 2012; 55:809-17. [DOI: 10.1002/dev.21071] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/26/2012] [Indexed: 11/09/2022]
Affiliation(s)
- Gabriela González-Mariscal
- Centro de Investigación en Reproducción Animal; CINVESTAV-Universidad Autónoma de Tlaxcala; Apdo. Postal 62 Tlaxcala, Tlax. 90000 Mexico
| | - Ariadna Toribio
- Centro de Investigación en Reproducción Animal; CINVESTAV-Universidad Autónoma de Tlaxcala; Apdo. Postal 62 Tlaxcala, Tlax. 90000 Mexico
| | - José Antonio Gallegos
- Centro de Investigación en Reproducción Animal; CINVESTAV-Universidad Autónoma de Tlaxcala; Apdo. Postal 62 Tlaxcala, Tlax. 90000 Mexico
| | - Martín A. Serrano-Meneses
- Centro de Investigación en Reproducción Animal; CINVESTAV-Universidad Autónoma de Tlaxcala; Apdo. Postal 62 Tlaxcala, Tlax. 90000 Mexico
| |
Collapse
|
18
|
Kojima S, Stewart RA, Demas GE, Alberts JR. Maternal contact differentially modulates central and peripheral oxytocin in rat pups during a brief regime of mother-pup interaction that induces a filial huddling preference. J Neuroendocrinol 2012; 24:831-40. [PMID: 22260655 PMCID: PMC4060530 DOI: 10.1111/j.1365-2826.2012.02280.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Central oxytocin mediates the acquisition of a filial preference for maternal odour in rat pups, manifested by their huddling preferences. The present study was designed to examine whether maternal care modulates oxytocin concentrations in rat pups and, if so, how different types of maternal contact are associated with the pups' oxytocin concentrations. Pairs of 14-day-old littermates were removed from their home cage for 1 h and then placed with a lactating foster mother for 2 h, or they remained isolated at room temperature. Enzyme immunoassays revealed that maternal care and maternal separation can differentially modulate pups' oxytocin concentrations. Both hypothalamic and serum oxytocin increased during the 1-h separation. Pups placed with a foster mother after the separation maintained the same concentrations in the hypothalamus and serum through the fostering period. By contrast, pups placed with no mother showed a further increase in hypothalamic oxytocin but serum oxytocin decreased. Behavioural analyses revealed that skin-to-skin contact with the mother, but not simple physical contact or maternal licking/grooming, was positively correlated with the pups' hypothalamic oxytocin concentrations. These neuroendocrine data match previous findings showing that skin-to-skin contact with mother facilitates the acquisition of the pups' huddling preference for a maternally-associated odour. Taken together, the present study suggests that maternal skin-to-skin contact stimulates pups' central oxytocin, at the same time as creating the conditions for inducing a preference for maternal odour and establishing a social affiliation in rat pups; the natural schedule of maternal separation and reunion may modulate pups' oxytocin concentrations, providing scaffolding for the acquisition of their filial huddling preference.
Collapse
Affiliation(s)
- S Kojima
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
| | | | | | | |
Collapse
|
19
|
Qiu J, Hindmarch CCT, Yao ST, Tasker JG, Murphy D. Transcriptomic analysis of the osmotic and reproductive remodeling of the female rat supraoptic nucleus. Endocrinology 2011; 152:3483-91. [PMID: 21791562 PMCID: PMC3159778 DOI: 10.1210/en.2011-1044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The supraoptic nucleus (SON) of the hypothalamus is an important integrative brain structure that coordinates responses to perturbations in water balance and regulates maternal physiology through the release of the neuropeptide hormones vasopressin and oxytocin into the circulation. Both dehydration and lactation evoke a dramatic morphological remodeling of the SON, a process known as function-related plasticity. We hypothesize that some of the changes seen in SON remodeling are mediated by differential gene expression, and have thus used microarrays to document global changes in transcript abundance that accompany chronic dehydration in female rats, and in lactation. In situ hybridization analysis has confirmed the differential expression of three of these genes, namely TNF-induced protein 6, gonadotropin-inducible transcription factor 1, and ornithine decarboxylase antizyme inhibitor 1. Comparison of differential gene expression patterns in male and female rats subjected to dehydration and in lactating rats has enabled the identification of common elements that are significantly enriched in gene classes with particular functions. Two of these are related to the requirement for increased protein synthesis and hormone delivery in the physiologically stimulated SON (translation initiation factor activity and endoplasmic reticulum-Golgi intermediate compartment, respectively), whereas others are consistent with the concept of SON morphological plasticity (collagen fibril organization, extracellular matrix organization and biogenesis, extracellular structure organization and biogenesis, and homophilic cell adhesion). We suggest that the genes coordinately regulated in the SON as a consequence of dehydration and lactation form a network that mediates the plastic processes operational in the physiologically activated SON.
Collapse
Affiliation(s)
- Jing Qiu
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Whitson Street, Bristol BS1 3NY, United Kingdom
| | | | | | | | | |
Collapse
|
20
|
Armstrong WE, Wang L, Li C, Teruyama R. Performance, properties and plasticity of identified oxytocin and vasopressin neurones in vitro. J Neuroendocrinol 2010; 22:330-42. [PMID: 20210845 PMCID: PMC2910405 DOI: 10.1111/j.1365-2826.2010.01989.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The neurohypophysial hormones oxytocin (OT) and vasopressin (VP) originate from hypothalamic neurosecretory cells in the paraventricular and supraoptic (SON) nuclei. The firing rate and pattern of action potentials arising from these neurones determine the timing and quantity of peripheral hormone release. We have used immunochemical identification of biocytin-filled SON neurones in hypothalamic slices in vitro to uncover differences between OT and VP neurones in membrane and synaptic properties, firing patterns, and plasticity during pregnancy and lactation. In this review, we summarise some recent findings from this approach: (i) VP neuronal excitability is influenced by slow (sDAP) and fast (fDAP) depolarising afterpotentials that underlie phasic bursting activity. The fDAP may relate to a transient receptor potential (TRP) channel, type melastatin (TRPM4 and/or TRPM5), both of which are immunochemically localised more to VP neurones, and especially, to their dendrites. Both TRPM4 and TRPM5 mRNAs are found in the SON, but single cell reverse transcriptase-polymerisation suggests that TRPM4 might be the more prominent channel. Phasic bursting in VP neurones is little influenced by spontaneous synaptic activity in slices, being shaped largely by intrinsic currents. (ii) The firing pattern of OT neurones ranges from irregular to continuous, with the coefficient of variation determined by randomly distributed, spontaneous GABAergic, inhibitory synaptic currents (sIPSCs). These sIPSCs are four- to five-fold more frequent in OT versus VP neurones, and much more frequent than spontaneous excitatory synaptic currents. (iii) Both cell types express Ca(2+)-dependent afterhyperpolarisations (AHPs), including an apamin-sensitive, medium duration AHP and a slower, apamin-insensitive AHP (sAHP). In OT neurones, both AHPs are enhanced during pregnancy and lactation. During pregnancy, the plasticity of the sAHP is blocked by antagonism of central OT receptors. AHP enhancement is mimicked by exposing slices from day 19 pregnant rats to OT and oestradiol, suggesting that central OT and sex steroids programme this plasticity during pregnancy by direct hypothalamic actions. In conclusion, the differences in VP and OT neuronal function are underlain by differences in both membrane and synaptic properties, and differentially modulated by reproductive state.
Collapse
Affiliation(s)
- W E Armstrong
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
| | | | | | | |
Collapse
|
21
|
Popescu IR, Morton LA, Franco A, Di S, Ueta Y, Tasker JG. Synchronized bursts of miniature inhibitory postsynaptic currents. J Physiol 2010; 588:939-51. [PMID: 20123785 DOI: 10.1113/jphysiol.2009.181461] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Spike-independent miniature postsynaptic currents are generally stochastic and are therefore not thought to mediate information relay in neuronal circuits. However, we recorded endogenous bursts of IPSCs in hypothalamic magnocellular neurones in the presence of TTX, which implicated a coordinated mechanism of spike-independent GABA release. IPSC bursts were identical in the absence of TTX, although the burst incidence increased 5-fold, indicating that IPSC bursts were composed of miniature IPSCs (mIPSCs), and that the probability of burst generation increased with action potential activity. IPSC bursts required extracellular calcium, although they were not dependent on calcium influx through voltage-gated calcium channels or on calcium mobilization from intracellular stores. Current injections simulating IPSC bursts were capable of triggering and terminating action potential trains. In 25% of dual recordings, a subset of IPSC bursts were highly synchronized in onset in pairs of magnocellular neurones. Synchronized IPSC bursts displayed properties that were consistent with simultaneous release at GABA synapses shared between pairs of postsynaptic magnocellular neurones. Synchronized bursts of inhibitory synaptic inputs represent a novel mechanism that may contribute to the action potential burst generation, termination and synchronization responsible for pulsatile hormone release from neuroendocrine cells.
Collapse
Affiliation(s)
- Ion R Popescu
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, USA
| | | | | | | | | | | |
Collapse
|
22
|
HONDA K, HIGUCHI T. Effects of Unilateral Electrolytic Lesion of the Dorsomedial Nucleus of the Hypothalamus on Milk-ejection Reflex in the Rat. J Reprod Dev 2010; 56:98-102. [DOI: 10.1262/jrd.09-090e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Kazumasa HONDA
- Faculty of Nursing and Welfare Sciences, Fukui Prefectural University
| | - Takashi HIGUCHI
- Department of Physiology, Faculty of Medical Sciences, University of Fukui
| |
Collapse
|
23
|
Wang YF, Hamilton K. Chronic vs. acute interactions between supraoptic oxytocin neurons and astrocytes during lactation: role of glial fibrillary acidic protein plasticity. ScientificWorldJournal 2009; 9:1308-20. [PMID: 19936568 PMCID: PMC3548440 DOI: 10.1100/tsw.2009.148] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In this article, we review studies of astrocytic-neuronal interactions and their effects on the activity of oxytocin (OXT) neurons within the magnocellular hypothalamo-neurohypophysial system. Previous work over several decades has shown that withdrawal of astrocyte processes increases OXT neuron excitability in the hypothalamic supraoptic nucleus (SON) during lactation. However, chronically disabling astrocyte withdrawal does not significantly affect the functioning of OXT neurons during suckling. Nevertheless, acute changes in a cytoskeletal element of astrocytes, glial fibrillary acidic protein (GFAP), occur in concert with changes in OXT neuronal activity during suckling. Here, we compare these changes in GFAP and related proteins with chronic changes that persist throughout lactation. During lactation, a decrease in GFAP levels accompanies retraction of astrocyte processes surrounding OXT neurons in the SON, resulting from high extracellular levels of OXT. During the initial stage of suckling, acute increases in OXT levels further strengthen this GFAP reduction and facilitate the retraction of astrocyte processes. This change, in turn, facilitates burst discharges of OXT neurons and leads to a transient increase in excitatory neurochemicals. This transient neurochemical surge acts to reverse GFAP expression and results in postburst inhibition of OXT neurons. The acute changes in astrocyte GFAP levels seen during suckling likely recur periodically, accompanied by rhythmic changes in glutamate metabolism, water transport, gliotransmitter release, and spatial relationships between astrocytes and OXT neurons. In the neurohypophysis, astrocyte retraction and reversal with accompanying GFAP plasticity also likely occur during lactation and suckling, which facilitates OXT release coordinated with its action in the SON. These studies of the dynamic interactions that occur between astrocytes and OXT neurons mediated by GFAP extend our understanding of astrocyte functions within the central nervous system.
Collapse
Affiliation(s)
- Yu-Feng Wang
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, Shreveport, USA.
| | | |
Collapse
|
24
|
Tsingotjidou AS, Papadopoulos GC. The Milk-Ejection Reflex in the Sheep: An Anatomical Study on the Afferent Pathway. Anat Histol Embryol 2008; 37:245-50. [DOI: 10.1111/j.1439-0264.2007.00833.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
25
|
Oxytocin-induced postinhibitory rebound firing facilitates bursting activity in oxytocin neurons. J Neurosci 2008; 28:385-94. [PMID: 18184781 DOI: 10.1523/jneurosci.5198-07.2008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During parturition and lactation, neurosecretory oxytocin (OT) neurons in the hypothalamus achieve pulsatile hormone secretion by coordinated bursts of firing that occur throughout the neuronal population. This activity is partly controlled by somatodendritic release of OT, which facilitates the onset and recurrence of synchronized bursting. To further investigate the cellular mechanisms underlying the control exerted by OT on the activity of its own neurons, we studied the effects of the peptide on membrane potential and synaptic activity in OT neurons in hypothalamic organotypic slice cultures. Bath application of low concentrations of OT (<100 nM) facilitated GABA(A) receptor-mediated inhibitory transmission through a presynaptic mechanism without affecting membrane potential and excitatory glutamatergic synaptic activity. The facilitatory action of OT on GABAergic transmission was dose-dependent, starting at 25 nM and disappearing at concentrations >100 nM. As shown previously, higher concentrations of OT (>500 nM) had the opposite effect, inhibiting GABA(A) receptors via a postsynaptic mechanism. Surprisingly, OT-mediated facilitation of GABAergic transmission promoted action potential firing in 40% of the neurons. Each action potential occurred at the end of the repolarizing phase of an inhibitory potential. Pharmacological dissection revealed that this firing involved the activation of low-threshold activated calcium channels. Detailed statistical analysis showed that OT-mediated firing upregulated bursting activity in OT neurons. It is thus likely to optimize OT secretion and, as a consequence, facilitate delivery and milk ejection in mammals.
Collapse
|
26
|
Affiliation(s)
- William E Armstrong
- Department of Anatomy and Neurobiology, Neuroscience Institute, University of Tennessee Health Science Center, 855 Monroe Avenue, Memphis, TN 38163, USA.
| |
Collapse
|
27
|
Honda K, Higuchi T. Oxytocin neurons in the supraoptic nucleus receive excitatory inputs from the bilateral dorsomedial hypothalamic nuclei. Brain Res Bull 2007; 74:237-42. [PMID: 17720545 DOI: 10.1016/j.brainresbull.2007.06.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 05/29/2007] [Accepted: 06/01/2007] [Indexed: 10/23/2022]
Abstract
To examine whether inputs from the dorsomedial hypothalamic nucleus (DMH) alter the discharge of putative oxytocin (OT) neurons with hypothesis that excitation of DMH neurons would increase the activity of OT neurons, electrical stimulation was applied to the DMH in both sides of the hypothalamus while electrical activity of single OT neurons in the supraoptic nucleus (SON) was recorded in urethane-anesthetized lactating rats. About half of the OT neurons showed orthodromic excitation or inhibition followed by excitation in response to electrical stimulation of the DMH on both sides. Continuous electrical stimulation of the DMH both ipsi- and contralateral to the recording side at 10-50 Hz for 30-60 s increased firing rate in 58% of OT neurons tested. Continuous electrical stimulation of the DMH not only excited spiking activity of single OT neurons but also increased intramammary pressure. The results may suggest that some of the projections from the DMH to the SON are bilateral and possibly contribute to coordinated bilateral activation of OT neurons in the hypothalamus during the milk-ejection reflex.
Collapse
Affiliation(s)
- Kazumasa Honda
- Faculty of Nursing and Welfare Sciences, Fukui Prefectural University, Matsuoka-kenjojima, Eiheiji-cho, Fukui 910-1195, Japan.
| | | |
Collapse
|
28
|
Cohen I, Huberfeld G, Miles R. Emergence of disinhibition-induced synchrony in the CA3 region of the guinea pig hippocampus in vitro. J Physiol 2005; 570:583-94. [PMID: 16322056 PMCID: PMC1479869 DOI: 10.1113/jphysiol.2005.097899] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Suppressing inhibition mediated by GABAA receptors induces rhythmic bursts of synchronous firing in the CA3 region of the hippocampus. Extracellular and intracellular records were made from guinea pig hippocampal slices to examine the emergence of this synchrony. We found that application of GABAA receptor antagonists initiated a sequence of changes in the activity of the CA3 neuronal population. First, the frequency of firing detected in multiunit records increased. Then, firing began to oscillate with increases followed by decreases in firing that occurred at intervals of 0.5-2 s. The coherence of the rhythmic activity at a single site increased with time, and discharges at distant sites in the CA3 region became correlated. Fluctuations in firing were associated with extracellular field potentials. Finally, epileptiform events associated with large field potentials began to recur at intervals of 5-10 s. The onset of fully synchronous events was sudden and correlated with a large increase in the amplitude of the field potential. Thus the CA3 population can express states of partial population synchrony preceding the onset of epileptiform discharges. A similar activity was induced and maintained by applying low doses of GABAA receptor antagonists. Intracellular records suggest that inhibitory signalling mediated by GABAB receptors contributes to the emergence of this activity. States of partial synchrony in the CA3 region exposed to GABAA receptor antagonists therefore depend on alternating periods of firing, presumably dependent on excitatory synaptic mechanisms, and silence, mediated in part by the activation of GABAB receptors.
Collapse
Affiliation(s)
- Ivan Cohen
- INSERM U739, CHU Pité-Salpêtrière, UPMC, 105 bd de l'Hôpital, Paris, France.
| | | | | |
Collapse
|
29
|
Moos F, Marganiec A, Fontanaud P, Guillou-Duvoid A, Alonso G. Synchronization of oxytocin neurons in suckled rats: possible role of bilateral innervation of hypothalamic supraoptic nuclei by single medullary neurons. Eur J Neurosci 2004; 20:66-78. [PMID: 15245480 DOI: 10.1111/j.0953-816x.2004.03455.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have previously shown that oxytocin neurons located in the four hypothalamic magnocellular nuclei display synchronous bursts of action potentials before each milk ejection. The mechanisms involved in such a synchronization have, however, not yet been elucidated. In this study, we test the hypothesis of an extranuclear synchronization arising from a common extrahypothalamic input innervating bilateral magnocellular nuclei. First, two different retrograde tracers were injected into the right and left supraoptic nuclei of rats that were fixed 5-7 days later. Each tracer labelled numerous neurons in various brain regions ipsilateral or contralateral to the injection site, but colocalization of the two tracers within the same cell body could only be detected bilaterally in neurons in the ventromedial regions of the medulla oblongata. The axonal projections of these medullary neurons were then visualized by the unilateral microinjection of an anterograde tracer (BDA) within the ventromedial medulla oblongata. BDA-labelled axons afferent to the hypothalamus were found to branch towards both supraoptic nuclei through medial portions of the optic chiasma. Finally, in anaesthetized lactating rats, surgical lesions were placed medially through the optic chiasma and the electrical activity of oxytocin neurons in bilateral supraoptic nuclei was pair-recorded during suckling. The incidence of synchronous bursts in oxytocin neurons located within bilateral supraoptic nuclei were dramatically altered only when the medial portions of the optic chiasma were totally lesioned. Taken together, these data suggest that medullary neurons afferent to bilateral supraoptic nuclei are involved in the recruitment and synchronization of bursting in oxytocin neurons during suckling.
Collapse
Affiliation(s)
- Françoise Moos
- CNRS UMR 5101, Biologie des Neurones Endocrines, CCIPE, 141 rue de la Cardonille, 34094 Montpellier Cedex 05, France.
| | | | | | | | | |
Collapse
|
30
|
Honda K, Narita K, Murata T, Higuchi T. Prolactin releasing peptides modulate background firing rate and milk-ejection related burst of oxytocin cells in the supraoptic nucleus. Brain Res Bull 2004; 63:315-9. [PMID: 15196657 DOI: 10.1016/j.brainresbull.2004.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Revised: 03/31/2004] [Accepted: 04/01/2004] [Indexed: 10/26/2022]
Abstract
The hypothalamic dorsomedial nucleus is suggested to be a final relay site for the afferent pathway of milk-ejection reflex. Existence of prolactin releasing peptide-immunoreactive cells in the dorsomedial nucleus and synaptic contact of prolactin releasing peptide-immunoreactive terminals with oxytocin cells was reported. Experiments were done to test the effect of prolactin releasing peptide on the electrical activity of oxytocin cells in the supraoptic nucleus. In rat brain slice preparations, oxytocin cells were unresponsive to the peptide. In lactating rats, although lateral ventricular injection of prolactin releasing peptide (20 nmol) was ineffective, a hundred nanomoles of the peptide increased basal activity and amplitude of milk-ejection related burst firing of oxytocin cells. Cells responded to lateral ventricular injection of peptides were unresponsive to direct application of peptides by pressure ejection from the recording electrode. These results suggest that prolactin releasing peptide may modulate electrical activity of oxytocin cells not through its direct action on oxytocin cells but through its action on area other than supraoptic nucleus.
Collapse
Affiliation(s)
- Kazumasa Honda
- Department of Physiology, Fukui Medical University, Matsuoka, Fukui 910-1193, Japan.
| | | | | | | |
Collapse
|
31
|
Wang YF, Hatton GI. Milk ejection burst-like electrical activity evoked in supraoptic oxytocin neurons in slices from lactating rats. J Neurophysiol 2004; 91:2312-21. [PMID: 14724260 DOI: 10.1152/jn.00697.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
To examine the mechanisms underlying milk-ejection bursts of oxytocin (OT) neurons during suckling, both in vivo and in vitro studies were performed on supraoptic OT neurons from lactating rats. The bursts were first recorded extracellularly in anesthetized rats. Burst-related electrical parameters were essentially the same as previous reports except for a trend toward transient decreases in basal firing rates immediately preceding the burst. From putative OT neurons in slices with extracellular recordings, bursts that closely mimicked the in vivo bursts were elicited by phenylephrine, an alpha1-adrenoceptor agonist, in a low-Ca(2+) medium. Moreover, in whole cell patch-clamp recordings, the in vitro bursts were recorded from immunocytochemically identified OT neurons. After a transient decrease in the basal firing rate, the in vitro bursts started with a sudden increase in the firing rate, quickly reaching a peak level, then gradually decaying, and ended with a postburst inhibition. A brief depolarization of the membrane potential and an increase in membrane conductance appeared after the onset of the burst. Spikes during a burst were characterized by a significant increase in the duration and decrease in the amplitude around the peak rate firing. These bursts were significantly different from short-lasting burst firing of vasopressin neurons in membrane potential changes, time to reach peak firing rate, spike amplitude and duration during peak rate firing. Our extensive analysis of these results suggests that the in vitro burst is a useful model for further study of mechanisms underlying milk-ejection bursts of OT neurons in vivo.
Collapse
Affiliation(s)
- Yu-Feng Wang
- Department of Cell Biology and Neuroscience, University of California, Riverside, California 92521, USA
| | | |
Collapse
|
32
|
Morales T, Shapiro E, Mena F. beta-adrenergic mechanisms modulate central nervous system effects of prolactin on milk ejection. Physiol Behav 2001; 74:119-26. [PMID: 11564459 DOI: 10.1016/s0031-9384(01)00560-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is known that prolactin (PRL) is produced within the brain and numerous central actions of the hormone have been reported. In anesthetized lactating rats, central administration of PRL, i.e., intracerebroventricular (icv) or intrathecally (it), facilitated milk ejection (ME) by depressing the sympathetically mediated facilitatory tone of the mammary ductal system. However, it is not known whether or not the same effects and similar mechanisms take place in conscious rats after PRL administration. In the present study, the effects of centrally administered PRL, i.e., icv or it, on ME was determined in both conscious and anesthetized rats. In conscious rats, the rate of ME was determined by applying a 15-min period of suckling by the litter, following a 6-h period of isolation. In anesthetized rats, intramammary pressure (IMP) responses of the mammary glands to exogenous oxytocin (OT) were recorded. The results showed that, whereas in anesthetized rats, increased responsiveness of the mammary glands to OT were observed after PRL administration, an intense inhibition of ME occurred in conscious rats. Because, in conscious and anesthetized rats, these effects were prevented by prior administration of the beta-adrenergic blocker propranolol (PROP) to the mothers, this suggests that the PRL effects on ME are modulated through sympathomimetic and sympatholytic actions in conscious and anesthetized rats, respectively. Thus, as shown by ductal tone measurements, in conscious, but not in anesthetized rats, the effect of PRL was associated with increased ductal constriction within the mammary glands; an effect that was mimicked by icv administration of the beta-adrenergic agonist isoproterenol (ISOP) and that was prevented by PROP. Further, the sympatholytic action of icv-PRL in anesthetized rats prevented the effect on ductal tone of both icv-PRL in conscious rats and of ISOP in anesthetized rats. Taken together, these results clearly suggest that the central effects of PRL on ME are modulated by adrenergic mechanisms.
Collapse
Affiliation(s)
- T Morales
- Centro de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-UAQ, 76230, Juriquilla, Qro., Mexico
| | | | | |
Collapse
|
33
|
Morales T, Shapiro E, Marina N, Mena F. Sympathetic innervation of mammary glands mediates suckling-induced reflex inhibition of milk yield in rats. Physiol Behav 2001; 74:37-43. [PMID: 11564449 DOI: 10.1016/s0031-9384(01)00559-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Previous work has shown that physiologic activation of the sympathetic system may inhibit milk yield (ME) in rats. Thus, adrenal catecholamines (CAs) are released by suckling, but it is not known whether such inhibition results also from reflex activation by the same stimulus of neural sympathetics upon the mammary gland. The present experiments were designed to determine whether suckling inhibits ME induced by oxytocin (OT) in the urethane-anesthetized lactating rat, and whether such inhibition results from adrenal and/or neurally released CAs. Rats were isolated (6 h) from their pups and then anesthetized. OT (0.8 mU every 2 min) was administered intravenously to the mothers during suckling. Rats were either chronically implanted with cannulae into the lateral cerebral ventricles (intracerebroventricularly), bilaterally adrenalectomized (ADX), hypophysectomized (HX), spinal cord transected (SCT: T3-T4), or had the nipple area (NA) locally anesthetized before suckling. MEs were low in control, sham, ADX and HX rats, but not in rats given the beta-adrenergic blocker propranolol (PROP; intravenously or intracerebroventricularly injected), nor in SCT, NA or PROP-HX rats. As revealed by ductal resistance measurements as an indicator of ductal tone, suckling-induced inhibition of ME was due to ductal constriction within the mammary glands. These effects of suckling, however, could be prevented by prior activation of ductal mechanoreceptors. Together, these results indicate that suckling inhibits ME through the reflex activation of neurally mediated central beta-adrenergic mechanisms, and that these effects, in turn, can be regulated by ductal mechanoreceptor activation.
Collapse
Affiliation(s)
- T Morales
- Centro de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM, Apdo. Postal 1-1140 76230 Juriquilla, Querétaro, Qro., Mexico
| | | | | | | |
Collapse
|
34
|
Evidence for a hypothalamic oxytocin-sensitive pattern-generating network governing oxytocin neurons in vitro. J Neurosci 1998. [PMID: 9712636 DOI: 10.1523/jneurosci.18-17-06641.1998] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During lactation and parturition, magnocellular oxytocin (OT) neurons display a characteristic bursting electrical activity responsible for pulsatile OT release. We investigated this activity using hypothalamic organotypic slice cultures enriched in magnocellular OT neurons. As shown here, the neurons are functional and actively secrete amidated OT into the cultures. Intracellular recordings were made from 23 spontaneously bursting and 28 slow irregular neurons, all identified as oxytocinergic with biocytin and immunocytochemistry. The bursting electrical activity was similar to that described in vivo and was characterized by bursts of action potentials (20.1 +/- 4.3 Hz) lasting approximately 6 sec, over an irregular background activity. OT (0.1-1 microM), added to the medium, increased burst frequency, reducing interburst intervals by 70%. The peptide also triggered bursting in 27% of nonbursting neurons. These effects were mimicked by the oxytocin receptor (OTR) agonist [Thr4, Gly7]-OT and inhibited by the OTR antagonist desGly-NH2d(CH2)5[D-Tyr2,Thr4]OVT. Burst rhythmicity was independent of membrane potential. Hyperpolarization of the cells unmasked volleys of afferent EPSPs underlying the bursts, which were blocked by CNQX, an AMPA/kainate receptor antagonist. Our results reveal that OT neurons are part of a hypothalamic rhythmic network in which a glutamatergic input governs burst generation. OT neurons, in turn, exert a positive feedback on their afferent drive through the release of OT.
Collapse
|
35
|
Jourdain P, Israel JM, Dupouy B, Oliet SH, Allard M, Vitiello S, Theodosis DT, Poulain DA. Evidence for a hypothalamic oxytocin-sensitive pattern-generating network governing oxytocin neurons in vitro. J Neurosci 1998; 18:6641-9. [PMID: 9712636 PMCID: PMC6792984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
During lactation and parturition, magnocellular oxytocin (OT) neurons display a characteristic bursting electrical activity responsible for pulsatile OT release. We investigated this activity using hypothalamic organotypic slice cultures enriched in magnocellular OT neurons. As shown here, the neurons are functional and actively secrete amidated OT into the cultures. Intracellular recordings were made from 23 spontaneously bursting and 28 slow irregular neurons, all identified as oxytocinergic with biocytin and immunocytochemistry. The bursting electrical activity was similar to that described in vivo and was characterized by bursts of action potentials (20.1 +/- 4.3 Hz) lasting approximately 6 sec, over an irregular background activity. OT (0.1-1 microM), added to the medium, increased burst frequency, reducing interburst intervals by 70%. The peptide also triggered bursting in 27% of nonbursting neurons. These effects were mimicked by the oxytocin receptor (OTR) agonist [Thr4, Gly7]-OT and inhibited by the OTR antagonist desGly-NH2d(CH2)5[D-Tyr2,Thr4]OVT. Burst rhythmicity was independent of membrane potential. Hyperpolarization of the cells unmasked volleys of afferent EPSPs underlying the bursts, which were blocked by CNQX, an AMPA/kainate receptor antagonist. Our results reveal that OT neurons are part of a hypothalamic rhythmic network in which a glutamatergic input governs burst generation. OT neurons, in turn, exert a positive feedback on their afferent drive through the release of OT.
Collapse
Affiliation(s)
- P Jourdain
- Institut National de la Santé et de la Recherche Médicale U. 378, Institut François Magendie, F33077 Bordeaux Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Abstract
1. We tested whether firing characteristics are associated with the onset of bursting in oxytocin cells during suckling. Extracellular electrical activity of paraventricular and supraoptic oxytocin cells was recorded in lactating rats from the beginning of suckling up to the first milk-ejection burst, which occurred either within less than 1 h of suckling (bursting cells) or after injecting facilitatory drugs (non-bursting cells). 2. Significant differences in the distributions of firing rate (using low, intermediate and high categories, < or = 1, 1-3 and > 3 spikes s-1, respectively) of bursting and non-bursting cells were observed during suckling. Thirty minutes after pup application, most bursting cells (56%) had an intermediate firing rate, whereas non-bursting cells had either a low (36%) or high (40%) firing rate. 3. Thirty minutes after applying the pups, probability of bursting was highest for cells firing at 1-4 spikes s-1, and lowest for those firing above 5 spikes s-1. 4. Bursting cells with high initial firing rate decreased their firing rate substantially during suckling while most of those with low initial firing rate showed increases. For non-bursting cells, activity was maintained. 5. There were marked differences in firing rate and its evolution between paired bursting cells. The firing rates for non-bursting cell pairs were similar (mostly either low or high), and remained stable during suckling. 6. In conclusion, we suggest that, as suckling proceeds, probability of bursting is related to the firing rate of oxytocin cells within the whole population, more specifically to the proportion of cells within the animal initially or subsequently displaying a critical firing rate (between 1 and 3 spikes s-1). The firing rates of cells which eventually burst and which are firing outside this range change in a direction which brings them into the preferred range for bursting. 7. We suggest that when bursting occurs unaided, a majority of oxytocin cells fire in the preferred bursting range and facilitate the bursting of cells outside this range. Since such cooperativity does not develop between non-bursting cells, it might be due to centrally released oxytocin.
Collapse
Affiliation(s)
- D Brown
- Biomathematics Laboratory, Babraham Institute, Cambridge, UK
| | | |
Collapse
|
37
|
Wang YF, Negoro H, Honda K. Effect of interhemispheric sections of the hypothalamus on milk-ejection bursts of supraoptic oxytocin neurones during bilateral and unilateral suckling in the rat. Neurosci Lett 1997; 227:17-20. [PMID: 9178848 DOI: 10.1016/s0304-3940(97)00300-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The burst activity of oxytocin neurones was recorded from the supraoptic nucleus of lactating rats with or without interhemispheric sectioning of the hypothalamus during bilateral or unilateral suckling. The results showed that extensive interhemispheric sectioning did not abolish the burst of oxytocin neurones during bilateral and contralateral suckling (100% of 25 neurones and 95% of 20 neurones, respectively), but significantly reduced the number of oxytocin neurones that showed the burst during ipsilateral suckling (5.3% of 19 neurones). To orientate the crossing site of the signals for bilateral synchronization of the bursts of oxytocin neurones, interhemispheric sectioning of the rostral or caudal hypothalamus was attempted, but either sectioning partially blocked the occurrence of the bursts during ipsilateral suckling. These results suggest that there are two separate gates located on different sides of the hypothalamus and that the neural connections between the gates seem distributed diffusely.
Collapse
Affiliation(s)
- Y F Wang
- Department of Physiology, Fukui Medical School, Matsuoka, Japan
| | | | | |
Collapse
|
38
|
Stern JE, Armstrong WE. Sustained outward rectification of oxytocinergic neurones in the rat supraoptic nucleus: ionic dependence and pharmacology. J Physiol 1997; 500 ( Pt 2):497-508. [PMID: 9147333 PMCID: PMC1159399 DOI: 10.1113/jphysiol.1997.sp022036] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. Intracellular recordings were obtained in vitro from oxytocin and vasopressin neurones from dioestrous and lactating female rats. Oxytocin neurones were characterized under current clamp by the expression of a depolarization-activated, sustained outward rectification (SOR) and a rebound depolarization (RD). 2. An increment in extracellular K+ shifted the expression of the SOR and RD towards a more depolarized membrane potential, indicating that the mechanisms underlying these events are dependent on extracellular potassium. 3. The SOR and RD were blocked by external tetraethylammonium (10 mM) and Ba2+ (0.1-0.5 mM). Cs+ (2 mM) blocked the hyperpolarization-activated inward rectification without affecting the expression of the SOR and RD. 4. The SOR was not affected by 4-aminopyridine (6 mM). However, the rebound amplitude was significantly enhanced, indicating that the activation of a transient outward current interacts with the expression of the rebound. 5. Iberiotoxin (100 nM) and apamin (50 nM), toxins known to block some calcium-dependent potassium conductances, did not affect the expression of the SOR and RD. 6. The SOR and RD were significantly reduced by Cd2+ (0.5 mM) but not by Ni2+ (0.25 mM). 7. Muscarine (10 microM) did not affect the SOR or the RD. 8. These results indicate that the SOR and RD depend upon a depolarization-activated, sustained outward potassium current, which might be calcium dependent. A current with these characteristics has never been described before in the magnocellular system. Voltage-clamp experiments are needed to completely characterize this potassium conductance selectively expressed by oxytocin neurones.
Collapse
Affiliation(s)
- J E Stern
- Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis 38163, USA.
| | | |
Collapse
|
39
|
Wang YF, Negoro H, Honda K. Amplitudes and time courses of milk ejection bursts of oxytocin neurons in the midbrain-hemitransected lactating rat. Brain Res 1996; 719:203-6. [PMID: 8782882 DOI: 10.1016/0006-8993(96)00029-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the midbrain-hemitransected rats, 22 pairs of oxytocin neurons were recorded from 17 rats. Of the bursts on the lesioned side, the amplitude was smaller, the onset time was later and the burst span was shorter (P < 0.01). These results indicated that the amplitude and time course of the burst of oxytocin neurons mainly depend on suckling information from the nipples on their opposite side.
Collapse
Affiliation(s)
- Y F Wang
- Department of Physiology, Fukui Medical School, Japan
| | | | | |
Collapse
|
40
|
Pincus SM, Gevers EF, Robinson IC, van den Berg G, Roelfsema F, Hartman ML, Veldhuis JD. Females secrete growth hormone with more process irregularity than males in both humans and rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:E107-15. [PMID: 8772482 DOI: 10.1152/ajpendo.1996.270.1.e107] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In humans, serum growth hormone (GH) concentrations are significantly higher in women than in men, but the neuroendocrine mechanisms that underlie such gender differences are not known. We compared normal episodic GH secretion in males and females in three distinct settings: two human studies employing quite different assay techniques (immunoradiometric assay and a high-sensitivity immunofluorimetric method) and a rat study. To quantify the amount of regularity in data, we utilized approximate entropy (ApEn), a scale- and model-independent statistic. In each study, females exhibited significantly greater statistical irregularity in GH concentration series than their male counterparts (P < 10(-3) for each human study, P < 10(-6) for the rat study), implying that mass and mode of GH secretion are regulated differently in males and females. The regularity comparisons indicated complete gender separation (100% specificity and sensitivity) for the rat study and nearly complete separation for the immunofluorimetric assay study. The consistency and statistical significance of these findings suggest that this gender difference may be broadly based within higher animals and that this may be readily evaluated objectively by analysis of ApEn.
Collapse
Affiliation(s)
- S M Pincus
- Division of Neurophysiology and Neuropharmacology, National Institute for Medical Research, London, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
41
|
Armstrong WE. Morphological and electrophysiological classification of hypothalamic supraoptic neurons. Prog Neurobiol 1995. [DOI: 10.1016/0301-0082(95)80005-s] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
42
|
Lambert RC, Moos FC, Richard P. Action of endogenous oxytocin within the paraventricular or supraoptic nuclei: a powerful link in the regulation of the bursting pattern of oxytocin neurons during the milk-ejection reflex in rats. Neuroscience 1993; 57:1027-38. [PMID: 8309542 DOI: 10.1016/0306-4522(93)90046-i] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
During suckling, the periodic and synchronous bursting activity of oxytocin neurons has been shown to be facilitated by oxytocin itself, acting via several target sites, including the magnocellular nuclei. To investigate the role of the endogenous oxytocin released within the magnocellular nuclei during the milk-ejection reflex in the rat, an oxytocin antagonist (50 microM solution of [d(CH2)5, Tyr(Me)2,Orn8]-vasotocin was pressure-injected into either one paraventricular or one supraoptic nucleus while recording the bursting pattern of oxytocin neurons within the injected nucleus and within a contralateral nucleus. The oxytocin antagonist was injected either during an ongoing milk-ejection reflex or during its facilitation induced by oxytocin (1 microliter of 1 microM solution injected into the third ventricle, i.e. 1 ng). During an ongoing milk-ejection reflex, injections of the oxytocin antagonist (10 nl of 50 microM solution, i.e. 50 ng) into the paraventricular or supraoptic nucleus decreased (more than 20% change) the burst amplitude (total number of spikes/burst) of neurons within the injected nucleus in 100% of tests, and simultaneously of contralateral neurons in 68% of tests. Burst periodicity of the entire population was also decreased in 50% of tests whatever the nucleus injected, but burst desynchronization was never observed. Successive injections of minute volumes of oxytocin (10 nl of 10 microM solution, i.e. 0.1 ng) into the paraventricular or supraoptic nucleus (which will progressively affect a greater number of neurons) first increased burst amplitude of oxytocin neurons within the injected nucleus and then increased simultaneously burst amplitude of contralateral neurons and burst frequency of the whole oxytocin neuron population. All these results suggest that the recruitment of a critical number of oxytocin neurons within one nucleus induces changes in the bursting activity of the oxytocin neurons in the four magnocellular nuclei. Within the minute following an intracerebroventricular oxytocin injection, the oxytocin antagonist injected into the supraoptic nucleus not only prevented the oxytocin-induced facilitation but also completely interrupted the milk-ejection reflex. When injected into the paraventricular nucleus, the oxytocin antagonist was less efficient: it decreased the oxytocin-induced facilitation but the reflex was not blocked. Similar partial inhibitory effect (decrease in burst amplitude and burst frequency) was also observed when the oxytocin antagonist was injected into the supraoptic nucleus after facilitation of the milk-ejection reflex by intracerebroventricular oxytocin injection. In conclusion, endogenous oxytocin released within the magnocellular nuclei during suckling represents a necessary link of the neuronal network regulating the bursting activity of oxytocin neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- R C Lambert
- Laboratoire de Neurobiologie Endocrinologique, URA 1197 CNRS, Université de Montpellier II, France
| | | | | |
Collapse
|
43
|
Herbert J. Peptides in the limbic system: neurochemical codes for co-ordinated adaptive responses to behavioural and physiological demand. Prog Neurobiol 1993; 41:723-91. [PMID: 7908139 DOI: 10.1016/0301-0082(93)90033-o] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Herbert
- Department of Anatomy, University of Cambridge, U.K
| |
Collapse
|
44
|
Russell JA, Coombes JE, Leng G, Bicknell RJ. Morphine tolerance and inhibition of oxytocin secretion by kappa-opioids acting on the rat neurohypophysis. J Physiol 1993; 469:365-86. [PMID: 8271202 PMCID: PMC1143875 DOI: 10.1113/jphysiol.1993.sp019818] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
1. The present study investigated the mechanisms by which endogenous opioids regulate oxytocin secretion at the level of the posterior pituitary gland. Effects of the selective kappa-agonist U50,488 on oxytocin secretion were studied in urethane-anaesthetized lactating rats. Oxytocin secretion in response to electrical stimulation (0.5 mA, matched biphasic 1 ms pulses, 50 Hz, 60-180 pulses) of the neurohypophysial stalk was bioassayed on-line by measuring increases in intramammary pressure, calibrated with exogenous oxytocin. Intravenous (I.V.) U50,488 inhibited electrically stimulated oxytocin secretion, without affecting mammary gland sensitivity to oxytocin. The inhibition was dose related, with an ID50 of 441 (+194, -136) micrograms/kg and was naloxone reversible. Antagonism of endogenous beta-adrenoceptor activation by propranolol (1 mg/kg) reduced the potency of U50,488. The selective mu-agonist morphine (up to 5 mg/kg), had no effect on electrically stimulated oxytocin secretion, but depressed the mammary response to oxytocin. 2. In lactating rats given intracerebroventricular (I.C.V.) morphine infusion for 5 days to induce tolerance and dependence, I.V. U50,488 still inhibited electrically stimulated oxytocin secretion, but the ID50 was reduced to 170 (+78, -54) micrograms/kg; thus at the posterior pituitary the sensitivity of kappa-receptors is enhanced rather than reduced in morphine-tolerant rats, indicating the absence of cross-tolerance. In these rats, naloxone produced a large, sustained, fluctuating increase in intramammary pressure indicating morphine-withdrawal excitation of oxytocin secretion; I.V. U50,488 diminished this response, confirmed by radioimmunoassay, demonstrating the independence of mu- and kappa-receptors regulating oxytocin secretion. 3. In pregnant rats, I.C.V. infusion of morphine from day 17-18 of pregnancy delayed the start of parturition by 4 h, but did not significantly affect the progress of parturition once established, indicating tolerance to the inhibitory actions of morphine on oxytocin secretion in parturition, and lack of cross-tolerance to endogenous opioids restraining oxytocin in parturition. 4. Neurointermediate lobes from control and I.C.V. morphine-infused virgin rats were impaled on electrodes and perifused in vitro. Vasopressin and oxytocin release from the glands was measured by radioimmunoassay. Each gland was exposed to two periods of electrical stimulation (13 Hz, for 3 min). Naloxone (5 x 10(-6) M) was added before the second stimulation; half the lobes from each I.C.V. treatment were exposed to 5 x 10(-5) M morphine throughout.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Analgesics/pharmacology
- Animals
- Biological Assay
- Drug Tolerance
- Electric Stimulation
- Female
- Injections, Intraventricular
- Labor, Obstetric/drug effects
- Lactation/physiology
- Morphine/administration & dosage
- Morphine/pharmacology
- Morphine Dependence/physiopathology
- Naloxone/pharmacology
- Oxytocin/metabolism
- Pituitary Gland, Posterior/drug effects
- Pituitary Gland, Posterior/metabolism
- Pituitary Gland, Posterior/physiology
- Pregnancy
- Propranolol/pharmacology
- Pyrrolidines/pharmacology
- Radioimmunoassay
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, kappa/drug effects
- Vasopressins/metabolism
Collapse
Affiliation(s)
- J A Russell
- Department of Physiology, University Medical School, Edinburgh
| | | | | | | |
Collapse
|
45
|
Takano S, Negoro H, Honda K, Higuchi T. Lesion and electrophysiological studies on the hypothalamic afferent pathway of the milk ejection reflex in the rat. Neuroscience 1992; 50:877-83. [PMID: 1448204 DOI: 10.1016/0306-4522(92)90211-j] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The afferent pathway of the milk ejection reflex in the hypothalamus was investigated with lesion and electrophysiological methods in anesthetized lactating rats. Destruction of the central region of the mid-hypothalamus (n = 12) blocked milk ejections induced by suckling, while that of the lateral region (n = 7) had no effect. In an electrophysiological study, extracellular recordings of neurons antidromically activated by electrical stimulation of the supraoptic nucleus were obtained from the ipsilateral hypothalamus caudal to the paraventricular nucleus (n = 84). Thirty-nine neurons were examined to see whether their firing activities changed during the milk ejection reflex. A group of 13 neurons were found to show changes in their activities prior to the reflex milk ejection; the neurons displayed a brief high-frequency burst of spikes before each milk ejection in the same manner as oxytocin neurons, and none of them antidromically responded to electrical stimulation of the neurohypophysis. The bursting neurons were recorded from the dorsomedial hypothalamic nucleus (n = 6), the region just lateral to that nucleus (n = 3) and the posterior hypothalamus (n = 4). The locations were included in a region whose destruction blocked the milk ejection reflex. These results indicate that the afferent pathway of the milk ejection reflex in the rat runs through the medial portion of the hypothalamus posterior to the paraventricular nucleus and that this region contains neurons which relay the input to the oxytocin neurons projecting in the neurohypophysis.
Collapse
Affiliation(s)
- S Takano
- Department of Physiology, Fukui Medical School, Japan
| | | | | | | |
Collapse
|
46
|
Fénelon VS, Poulain DA. Electrical activity of dorsal horn neurons during the suckling-induced milk ejection reflex in the lactating rat. J Neuroendocrinol 1992; 4:575-84. [PMID: 21554642 DOI: 10.1111/j.1365-2826.1992.tb00206.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In lactating rats, suckling elicits the milk ejection reflex which consists of an intermittent synchronous activation of hypothalamic oxytocin neurons which releases oxytocin into the bloodstream. We here investigated the electrophysiological behaviour of spinal cord neurons linked to mammary innervation in relation to suckling and the suckling-induced milk ejection reflex. Experiments were carried out on 58 urethane-anaesthetized rats, paralysed with gallamine triethiodide and artificially ventilated. Fixation of the spinal cord and laminectomy significantly slowed down the reflex, which occurred in only 27% of the animals. In these rats, 31 dorsal horn neurons at the thoraco-lumbar level were found to be excited by nipple stimulation. During suckling by a litter of at least nine pups, they displayed an irregular pattern of brief bursts of activity (peak firing rate 22.0 ± 3.2 Hz, mean ± SD) correlated to the bouts of suckling of the pups. Seventeen out of 19 cells tested by stimulation of at least 2 adjacent nipples received convergent input from different ipsilateral nipples. Out of 11 cells tested, 8 were also activated by stimulation of a contralateral nipple. Fourteen out of 30 units were recorded through at least one reflex milk ejection. Their firing rate was significantly higher than the firing rate of cells recorded in animals which failed to milk eject (4.4 Hz ± 2.8 versus 1.5 Hz ± 0.7). At the moment of the high frequency discharge of action potentials, occurring in oxytocinergic cells 10 to 15 s before each milk ejection, spinal neurons showed no systematic change in electrical activity. In contrast, the stretch reaction of the pups, which corresponds to an intense period of suckling when milk ejection has started, induced, in 12 cells, a considerable increase in electrical activity. One unit was found to be inhibited by suckling and during the stretch reaction. Ten more units, which were not activated by stimulation of the nipples but responded to stimulation of excitatory receptive fields near the last three pairs of nipples, were recorded through reflex milk ejections: 8 remained silent during reflex milk ejections but 2 were activated when the pups stimulated their excitatory receptive field. We conclude that some dorsal horn neurons, able to respond readily to the suckling movements of pups, appear to receive an ungated input from the nipples. At the time of the activation of oxytocin neurons, they present no particular pattern of activation or inhibition which could account in a simple manner for the intermittence of the high frequency discharge in oxytocinergic cells. However, in so far as these dorsal horn neurons may be part of the milk ejection reflex pathway, their activity, showing convergence and summation of input, and being facilitated in milk ejecting animals, indicates that the reflex does undergo a certain degree of processing at the spinal cord level.
Collapse
Affiliation(s)
- V S Fénelon
- Laboratoire de Neuroendocrinologie Morphofonctionnelle, INSERM CJF 91.10, Université de Bordeaux II, Bordeaux, France
| | | |
Collapse
|
47
|
Kuchár S, Mozes S, Rybosová Z, Nováková V, Michalov M. Influence of early undernutrition in rats on their body fat and RNA content in VMH neurons. Physiol Behav 1992; 52:695-8. [PMID: 1384076 DOI: 10.1016/0031-9384(92)90399-m] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The RNA content of the ventromedial hypothalamus (VMH) and lateral hypothalamic area (LHA) neurons, and the epididymal, retroperitoneal, and liver fat content of 150-day-old male rats submitted to neonatal undernutrition, were investigated. The neonatal undernutrition was carried out by two different ways. First, by reducing the litters to two pups per nest from birth to weaning. The pups from normal litters (eight pups/nest) served as controls. Secondly, by separating half of the pups (four pups) from normal litters for 8 h daily during the first 5 postnatal days. The remaining nonseparated pups served as their controls. The data show that both groups of early undernourished pups had a significantly increased RNA content in the VMH neurons (RNA content in the LHA neurons was unchanged) and a significantly decreased epididymal, retroperitoneal, and liver fat content in comparison with their controls. The results indicate that early undernutrition leads to a permanent increase in the functional activity of VMH and alteration in fat metabolism in rats.
Collapse
Affiliation(s)
- S Kuchár
- Institute of Animal Physiology, Slovak Academy of Sciences, Kosice, Czechoslovakia
| | | | | | | | | |
Collapse
|
48
|
Karyakin MG, Alekseev NP. The influence of tactile stimulation of nipples on the milk ejection reflex in the rat. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 1992; 170:645-50. [PMID: 1507160 DOI: 10.1007/bf00199340] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Changes of positive pressure exerted by pups on nipples during sucking were investigated using anesthetized, lactating dams. It was found that, every 50-60 s, individual pups performed bouts of pressure oscillations (3/s) of high amplitude which lasted about 10-12 s and coincided with periods of increased motor activity. During the intervals, when pups were quiet, series of low-amplitude oscillations (3/s) were also observed. Using a strain measuring method to record the activity of sucking pups, synchronization of activity of two or more pups was found to occur periodically every 25-30 s and, most frequently, 10-30 s before the reflex increase of milk pressure. In further experiments, artificial tactile stimulation was applied to the dam's nipples using the joint action of suction and positive pressure. Following a short-term (10-20 s) increase in frequency and amplitude of artificial nipple stimulation, 60%-80% of all reflexive peaks of milk pressure were elicited with a latency of 19 +/- 5 s. This suggests that there are specific conditions under which the stimulation of nipples by pups may trigger the formation of the milk ejection reflex in the rat.
Collapse
Affiliation(s)
- M G Karyakin
- Institute of Physiology, St. Petersburg State University, Russia
| | | |
Collapse
|
49
|
Mozes S, Kuchár S, Michalov M, Nováková V. Influence of litter size on the RNA content of VMH and LHA in preweaning rats. Physiol Behav 1991; 50:1133-6. [PMID: 1724699 DOI: 10.1016/0031-9384(91)90573-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The nutritional status in the early postnatal period may significantly influence the development and functional activity of food intake regulating mechanisms. Therefore we investigated the weight gains and total RNA content of the ventromedial (VMH) and lateral (LHA) hypothalamic cells of rat pups in normal litters (8 pups/nest) and in reduced litters (2 pups/nest) reared permanently (from birth to weaning) or temporarily (from 1st to 5th day) in reduced nests. A significant decrease of weight gains was found in pups reared in reduced litters during the first 5 days which resulted in significant differences of body weight between the pups from normal and reduced litters on 5th day of life. On the 15th and 30th days, there were no significant differences in body weight between these animals, but the RNA content in VMH cells of pups reared in reduced litters was significantly increased on the 15th and 30th days. The RNA content in the LHA cells was unchanged. The results show that reducing a rat litter to 2 pups caused short-term undernutrition leading to permanent changes of the RNA content in the VMH neurons. The possible consequences of the permanently changed RNA content of this hypothalamic structure are discussed.
Collapse
Affiliation(s)
- S Mozes
- Institute of Animal Physiology, Slovak Academy of Sciences, Kosice, Czechoslovakia
| | | | | | | |
Collapse
|
50
|
Boudaba C, Poulain DA. Further Evidence that the Septum is not part of the Main Pathway of the Milk Ejection Reflex in the Rat. J Neuroendocrinol 1991; 3:199-204. [PMID: 19215522 DOI: 10.1111/j.1365-2826.1991.tb00263.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract The possible role of the medial septum in the control of oxytocin release and of the milk ejection reflex induced by suckling was investigated in lactating rats by using electrical stimulations and lesions. In anaesthetized animals, brief electrical stimulation of the medial septum at 5 to 50 Hz elicited a single brief milk ejection similar to natural reflex milk ejections, whereas prolonged low frequency stimulations (5 to 10 Hz) induced a prolonged inhibition of the reflex. In acute experiments under anaesthesia, lesions of the medial septum did not impair the amplitude and pattern of reflex milk ejections. In chronic experiments, lesions of the medial septum resulted first in a loss of body weight of the mothers and a parallel reduction in growth of the litters. After a few days, the litters gained weight normally, and the pattern of milk ejections was normal. Thus, the pathways which pass through or originate from the medial septum and which are excitatory for oxytocin release appear not to be involved in the regulation of the milk ejection reflex. In view of these results and those from our previous study on the lateral septum, we conclude that the whole septum is not essential to the milk ejection reflex. However, the effects of septal stimulation suggest that the medial and lateral septum may be involved in a secondary neural circuitry that can inhibit the reflex.
Collapse
Affiliation(s)
- C Boudaba
- INSERM U. 176, University of Bordeaux II, Bordeaux, France
| | | |
Collapse
|