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Ryczko D, Simon A, Ijspeert AJ. Walking with Salamanders: From Molecules to Biorobotics. Trends Neurosci 2020; 43:916-930. [PMID: 33010947 DOI: 10.1016/j.tins.2020.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/12/2020] [Accepted: 08/27/2020] [Indexed: 12/13/2022]
Abstract
How do four-legged animals adapt their locomotion to the environment? How do central and peripheral mechanisms interact within the spinal cord to produce adaptive locomotion and how is locomotion recovered when spinal circuits are perturbed? Salamanders are the only tetrapods that regenerate voluntary locomotion after full spinal transection. Given their evolutionary position, they provide a unique opportunity to bridge discoveries made in fish and mammalian models. Genetic dissection of salamander neural circuits is becoming feasible with new methods for precise manipulation, elimination, and visualisation of cells. These approaches can be combined with classical tools in neuroscience and with modelling and a robotic environment. We propose that salamanders provide a blueprint of the function, evolution, and regeneration of tetrapod locomotor circuits.
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Affiliation(s)
- Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada; Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada.
| | - András Simon
- Karolinska Institute, Department of Cell and Molecular Biology, Biomedicum, Solnavägen 9, 17163 Stockholm, Sweden
| | - Auke Jan Ijspeert
- Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
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Flaive A, Cabelguen JM, Ryczko D. The serotonin reuptake blocker citalopram destabilizes fictive locomotor activity in salamander axial circuits through 5-HT 1A receptors. J Neurophysiol 2020; 123:2326-2342. [PMID: 32401145 DOI: 10.1152/jn.00179.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Serotoninergic (5-HT) neurons are powerful modulators of spinal locomotor circuits. Most studies on 5-HT modulation focused on the effect of exogenous 5-HT and these studies provided key information about the cellular mechanisms involved. Less is known about the effects of increased release of endogenous 5-HT with selective serotonin reuptake inhibitors. In mammals, such molecules were shown to destabilize the fictive locomotor output of spinal limb networks through 5-HT1A receptors. However, in tetrapods little is known about the effects of increased 5-HT release on the locomotor output of axial networks, which are coordinated with limb circuits during locomotion from basal vertebrates to mammals. Here, we examined the effect of citalopram on fictive locomotion generated in axial segments of isolated spinal cords in salamanders, a tetrapod where raphe 5-HT reticulospinal neurons and intraspinal 5-HT neurons are present as in other vertebrates. Using electrophysiological recordings of ventral roots, we show that fictive locomotion generated by bath-applied glutamatergic agonists is destabilized by citalopram. Citalopram-induced destabilization was prevented by a 5-HT1A receptor antagonist, whereas a 5-HT1A receptor agonist destabilized fictive locomotion. Using immunofluorescence experiments, we found 5-HT-positive fibers and varicosities in proximity with motoneurons and glutamatergic interneurons that are likely involved in rhythmogenesis. Our results show that increasing 5-HT release has a deleterious effect on axial locomotor activity through 5-HT1A receptors. This is consistent with studies in limb networks of turtle and mouse, suggesting that this part of the complex 5-HT modulation of spinal locomotor circuits is common to limb and axial networks in limbed vertebrates.NEW & NOTEWORTHY Little is known about the modulation exerted by endogenous serotonin on axial locomotor circuits in tetrapods. Using axial ventral root recordings in salamanders, we found that a serotonin reuptake blocker destabilized fictive locomotor activity through 5-HT1A receptors. Our anatomical results suggest that serotonin is released on motoneurons and glutamatergic interneurons possibly involved in rhythmogenesis. Our study suggests that common serotoninergic mechanisms modulate axial motor circuits in amphibians and limb motor circuits in reptiles and mammals.
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Affiliation(s)
- Aurélie Flaive
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Jean-Marie Cabelguen
- Neurocentre Magendie, INSERM U 862, Université de Bordeaux, Bordeaux Cedex, France
| | - Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada.,Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Quebec, Canada.,Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada.,Centre des neurosciences de Sherbrooke, Sherbrooke, Quebec, Canada
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Yaeger DB, Coddington EJ. Calcium-induced calcium release activates spontaneous miniature outward currents in newt medullary reticular formation neurons. J Neurophysiol 2018; 120:3140-3154. [PMID: 29897864 DOI: 10.1152/jn.00616.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Neurons in the medullary reticular formation are involved in the control of postural and locomotor behaviors in all vertebrates. Reticulospinal neurons in this brain region provide one of the major descending projections to the spinal cord. Although neurons in the newt medullary reticular formation have been extensively studied using in vivo extracellular recordings, little is known of their intrinsic biophysical properties or of the underlying circuitry of this region. Using whole cell patch-clamp recordings in brain slices containing the rostromedial reticular formation from adult male newts, we observed spontaneous miniature outward currents (SMOCs) in ~2/3 of neurons. Although SMOCs superficially resembled inhibitory postsynaptic currents (IPSCs), they had slower risetimes and decay times than spontaneous IPSCs. SMOCs required intracellular Ca2+ release from ryanodine receptors and were also dependent on the influx of extracellular Ca2+. SMOCs were unaffected by apamin but were partially blocked by iberiotoxin and charybdotoxin, indicating that SMOCs were mediated by big-conductance Ca2+-activated K+ channels. Application of the sarco/endoplasmic Ca2+ ATPase inhibitor cyclopiazonic acid blocked the generation of SMOCs and also increased neural excitability. Neurons with SMOCs had significantly broader action potentials, slower membrane time constants, and higher input resistance than neurons without SMOCs. Thus, SMOCs may serve as a mechanism to regulate action potential threshold in a majority of neurons within the newt medullary reticular formation. NEW & NOTEWORTHY The medullary reticular formation exerts a powerful influence on sensorimotor integration and subsequent motor behavior, yet little is known about the neurons involved. In this study, we identify a transient potassium current that regulates action potential threshold in a majority of medullary reticular neurons.
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Tsutsui K, Haraguchi S, Vaudry H. 7α-Hydroxypregnenolone regulating locomotor behavior identified in the brain and pineal gland across vertebrates. Gen Comp Endocrinol 2018; 265:97-105. [PMID: 28919448 DOI: 10.1016/j.ygcen.2017.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 08/30/2017] [Accepted: 09/13/2017] [Indexed: 01/29/2023]
Abstract
The brain synthesizes steroids de novo from cholesterol, which are called neurosteroids. Based on extensive studies on neurosteroids over the past thirty years, it is now accepted that neurosteroidogenesis in the brain is a conserved property across vertebrates. However, the formation of bioactive neurosteroids in the brain is still incompletely elucidated in vertebrates. In fact, we recently identified 7α-hydroxypregnenolone (7α-OH PREG) as a novel bioactive neurosteroid stimulating locomotor behavior in the brain of several vertebrates. The follow-up studies have demonstrated that the stimulatory action of brain 7α-OH PREG on locomotor behavior is mediated by the dopaminergic system across vertebrates. More recently, we have further demonstrated that the pineal gland, an endocrine organ located close to the brain, is a major site of the formation of bioactive neurosteroids. In addition to the brain, the pineal gland actively produces 7α-OH PREG de novo from cholesterol as a major pineal neurosteroid that acts on the brain to control locomotor rhythms. This review summarizes the identification, biosynthesis and mode of action of brain and pineal 7α-OH PREG, a new bioactive neurosteroid regulating locomotor behavior, across vertebrates.
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Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan.
| | - Shogo Haraguchi
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan; Department of Biochemistry, Showa University School of Medicine, Tokyo 142-8555, Japan
| | - Hubert Vaudry
- INSERM U1239, Laboratory of Neuronal and Neuroendocrine Differentiation and Communication, Normandy University, 76000 Rouen, France
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Tsutsui K. How to contribute to the progress of neuroendocrinology: New insights from discovering novel neuropeptides and neurosteroids regulating pituitary and brain functions. Gen Comp Endocrinol 2016; 227:3-15. [PMID: 26145291 DOI: 10.1016/j.ygcen.2015.05.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 04/28/2015] [Accepted: 05/07/2015] [Indexed: 12/29/2022]
Abstract
Obtaining new insights by discovering novel neuropeptides and neurosteroids regulating pituitary and brain functions is essential for the progress of neuroendocrinology. At the beginning of 1970s, gonadotropin-releasing hormone (GnRH) was discovered in mammals. Since then, it was generally accepted that GnRH is the only hypothalamic neuropeptide regulating gonadotropin release in vertebrates. In 2000, however, gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that actively inhibits gonadotropin release, was discovered in quail. The follow-up studies demonstrated that GnIH acts as a new key player for regulation of reproduction across vertebrates. It now appears that GnIH acts on the pituitary and the brain to serve a number of behavioral and physiological functions. On the other hand, a new concept has been established that the brain synthesizes steroids, called neurosteroids. The formation of neurosteroids in the brain was originally demonstrated in mammals and subsequently in other vertebrates. Recently, 7α-hydroxypregnenolone was discovered as a novel bioactive neurosteroid inducing locomotor behavior of vertebrates, indicating that neurosteroidogenesis in the brain is still incompletely elucidated in vertebrates. At the beginning of 2010s, it was further found that the pineal gland actively produces neurosteroids. Pineal neurosteroids act on the brain to regulate locomotor rhythms and neuronal survival. Furthermore, the interaction of neuropeptides and neurosteroids is becoming clear. GnIH decreases aggressive behavior by regulating neuroestrogen synthesis in the brain. This review summarizes these new insights by discovering novel neuropeptides and neurosteroids in the field of neuroendocrinology.
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Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan.
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6
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Ryczko D, Auclair F, Cabelguen JM, Dubuc R. The mesencephalic locomotor region sends a bilateral glutamatergic drive to hindbrain reticulospinal neurons in a tetrapod. J Comp Neurol 2015; 524:1361-83. [PMID: 26470600 PMCID: PMC5019149 DOI: 10.1002/cne.23911] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 10/01/2015] [Accepted: 10/07/2015] [Indexed: 01/09/2023]
Abstract
In vertebrates, stimulation of the mesencephalic locomotor region (MLR) on one side evokes symmetrical locomotor movements on both sides. How this occurs was previously examined in detail in a swimmer using body undulations (lamprey), but in tetrapods the downstream projections from the MLR to brainstem neurons are not fully understood. Here we examined the brainstem circuits from the MLR to identified reticulospinal neurons in the salamander Notophthalmus viridescens. Using neural tracing, we show that the MLR sends bilateral projections to the middle reticular nucleus (mRN, rostral hindbrain) and the inferior reticular nucleus (iRN, caudal hindbrain). Ca2+ imaging coupled to electrophysiology in in vitro isolated brains revealed very similar responses in reticulospinal neurons on both sides to a unilateral MLR stimulation. As the strength of MLR stimulation was increased, the responses increased in size in reticulospinal neurons of the mRN and iRN, but the responses in the iRN were smaller. Bath‐application or local microinjections of glutamatergic antagonists markedly reduced reticulospinal neuron responses, indicating that the MLR sends glutamatergic inputs to reticulospinal neurons. In addition, reticulospinal cells responded to glutamate microinjections and the size of the responses paralleled the amount of glutamate microinjected. Immunofluorescence coupled with anatomical tracing confirmed the presence of glutamatergic projections from the MLR to reticulospinal neurons. Overall, we show that the brainstem circuits activated by the MLR in the salamander are organized similarly to those previously described in lampreys, indicating that the anatomo‐physiological features of the locomotor drive are well conserved in vertebrates. J. Comp. Neurol. 524:1361–1383, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Dimitri Ryczko
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada
| | - Francois Auclair
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada
| | - Jean-Marie Cabelguen
- INSERM U862 - Neurocentre Magendie, Motor System Diseases Team, Bordeaux Cedex, France
| | - Réjean Dubuc
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Département des sciences de l'activité physique, Université du Québec à Montréal, Québec, Canada
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Tsutsui K, Haraguchi S. Breakthrough in neuroendocrinology by discovering novel neuropeptides and neurosteroids: 2. Discovery of neurosteroids and pineal neurosteroids. Gen Comp Endocrinol 2014; 205:11-22. [PMID: 24704561 DOI: 10.1016/j.ygcen.2014.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bargmann-Scharrer's discovery of "neurosecretion" in the first half of the 20th century has since matured into the scientific discipline of neuroendocrinology. Identification of novel neurohormones, such as neuropeptides and neurosteroids, is essential for the progress of neuroendocrinology. Our studies over the past two decades have significantly broadened the horizons of this field of research by identifying novel neuropeptides and neurosteroids in vertebrates that have opened new lines of scientific investigation in neuroendocrinology. We have established de novo synthesis and functions of neurosteroids in the brain of various vertebrates. Recently, we discovered 7α-hydroxypregnenolone (7α-OH PREG), a novel bioactive neurosteroid that acts as a key regulator for inducing locomotor behavior by means of the dopaminergic system. We further discovered that the pineal gland, an endocrine organ located close to the brain, is an important site of production of neurosteroids de novo from cholesterol (CHOL). The pineal gland secretes 7α-OH PREG and 3α,5α-tetrahydroprogesterone (3α,5α-THP; allopregnanolone) that are involved in locomotor rhythms and neuronal survival, respectively. Subsequently, we have demonstrated their mode of action and functional significance. This review summarizes the discovery of these novel neurosteroids and its contribution to the progress of neuroendocrinology.
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Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan.
| | - Shogo Haraguchi
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan
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Bicanski A, Ryczko D, Cabelguen JM, Ijspeert AJ. From lamprey to salamander: an exploratory modeling study on the architecture of the spinal locomotor networks in the salamander. BIOLOGICAL CYBERNETICS 2013; 107:565-587. [PMID: 23463500 DOI: 10.1007/s00422-012-0538-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 11/20/2012] [Indexed: 06/01/2023]
Abstract
The evolutionary transition from water to land required new locomotor modes and corresponding adjustments of the spinal "central pattern generators" for locomotion. Salamanders resemble the first terrestrial tetrapods and represent a key animal for the study of these changes. Based on recent physiological data from salamanders, and previous work on the swimming, limbless lamprey, we present a model of the basic oscillatory network in the salamander spinal cord, the spinal segment. Model neurons are of the Hodgkin-Huxley type. Spinal hemisegments contain sparsely connected excitatory and inhibitory neuron populations, and are coupled to a contralateral hemisegment. The model yields a large range of experimental findings, especially the NMDA-induced oscillations observed in isolated axial hemisegments and segments of the salamander Pleurodeles waltlii. The model reproduces most of the effects of the blockade of AMPA synapses, glycinergic synapses, calcium-activated potassium current, persistent sodium current, and [Formula: see text]-current. Driving segments with a population of brainstem neurons yields fast oscillations in the in vivo swimming frequency range. A minimal modification to the conductances involved in burst-termination yields the slower stepping frequency range. Slow oscillators can impose their frequency on fast oscillators, as is likely the case during gait transitions from swimming to stepping. Our study shows that a lamprey-like network can potentially serve as a building block of axial and limb oscillators for swimming and stepping in salamanders.
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Affiliation(s)
- Andrej Bicanski
- Biorobotics Laboratory, School of Engineering, École Polytechnique Fédérale de Lausanne, Station 14, 1015 , Lausanne, VD, Switzerland,
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Bicanski A, Ryczko D, Knuesel J, Harischandra N, Charrier V, Ekeberg Ö, Cabelguen JM, Ijspeert AJ. Decoding the mechanisms of gait generation in salamanders by combining neurobiology, modeling and robotics. BIOLOGICAL CYBERNETICS 2013; 107:545-564. [PMID: 23430277 DOI: 10.1007/s00422-012-0543-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 12/13/2012] [Indexed: 06/01/2023]
Abstract
Vertebrate animals exhibit impressive locomotor skills. These locomotor skills are due to the complex interactions between the environment, the musculo-skeletal system and the central nervous system, in particular the spinal locomotor circuits. We are interested in decoding these interactions in the salamander, a key animal from an evolutionary point of view. It exhibits both swimming and stepping gaits and is faced with the problem of producing efficient propulsive forces using the same musculo-skeletal system in two environments with significant physical differences in density, viscosity and gravitational load. Yet its nervous system remains comparatively simple. Our approach is based on a combination of neurophysiological experiments, numerical modeling at different levels of abstraction, and robotic validation using an amphibious salamander-like robot. This article reviews the current state of our knowledge on salamander locomotion control, and presents how our approach has allowed us to obtain a first conceptual model of the salamander spinal locomotor networks. The model suggests that the salamander locomotor circuit can be seen as a lamprey-like circuit controlling axial movements of the trunk and tail, extended by specialized oscillatory centers controlling limb movements. The interplay between the two types of circuits determines the mode of locomotion under the influence of sensory feedback and descending drive, with stepping gaits at low drive, and swimming at high drive.
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Affiliation(s)
- Andrej Bicanski
- Biorobotics Laboratory, School of Engineering, École Polytechnique Fédérale de Lausanne, Station 14, 1015 , Lausanne, Vaud, Switzerland,
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Tsutsui K, Haraguchi S, Fukada Y, Vaudry H. Brain and pineal 7α-hydroxypregnenolone stimulating locomotor activity: identification, mode of action and regulation of biosynthesis. Front Neuroendocrinol 2013; 34:179-89. [PMID: 23685042 DOI: 10.1016/j.yfrne.2013.05.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 05/01/2013] [Accepted: 05/08/2013] [Indexed: 11/30/2022]
Abstract
Biologically active steroids synthesized in the central and peripheral nervous systems are termed neurosteroids. However, the biosynthetic pathways leading to the formation of neurosteroids are still incompletely elucidated. 7α-Hydroxypregnenolone, a novel bioactive neurosteroid stimulating locomotor activity, has been recently identified in the brain of newts and quail. Subsequently, the mode of action and regulation of biosynthesis of 7α-hydroxypregnenolone have been determined. Moreover, recent studies on birds have demonstrated that the pineal gland, an endocrine organ located close to the brain, is an important site of production of neurosteroids de novo from cholesterol. 7α-Hydroxypregnenolone is a major pineal neurosteroid that stimulates locomotor activity in juvenile chickens, connecting light-induced gene expression with locomotion. This review summarizes the advances in our understanding of the identification, mode of action and regulation of biosynthesis of brain and pineal 7α-hydroxypregnenolone, a potent stimulator of locomotor activity.
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Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo 162-8480, Japan.
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Tsutsui K, Haraguchi S, Matsunaga M, Koyama T, Do Rego JL, Vaudry H. 7α-Hydroxypregnenolone, a new key regulator of amphibian locomotion: discovery, progress and prospect. Gen Comp Endocrinol 2012; 176:440-7. [PMID: 22138220 DOI: 10.1016/j.ygcen.2011.11.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 11/11/2011] [Accepted: 11/13/2011] [Indexed: 11/26/2022]
Abstract
Seasonally-breeding amphibians have served as excellent animal models to investigate the biosynthesis and biological actions of neurosteroids. Previous studies have demonstrated that the brain of amphibians possesses key steroidogenic enzymes and produces pregnenolone, a precursor of steroid hormones, and other various neurosteroids. We recently found that the brain of seasonally-breeding newts actively produces 7α-hydroxypregnenolone, a previously undescribed amphibian neurosteroid. This novel amphibian neurosteroid acts as a neuronal modulator to stimulate locomotor activity in newts. Subsequently, the mode of action of 7α-hydroxypregnenolone has been demonstrated in the newt brain. 7α-Hydroxypregnenolone stimulates locomotor activity through activation of the dopaminergic system. To understand the functional significance of 7α-hydroxypregnenolone in the regulation of locomotor activity, diurnal and seasonal changes in synthesis of 7α-hydroxypregnenolone have also been demonstrated in the newt brain. Melatonin derived from the pineal gland and eyes regulates 7α-hydroxypregnenolone synthesis in the brain, thus inducing diurnal locomotor changes. Prolactin, an adenohypophyseal hormone, regulates 7α-hydroxypregnenolone synthesis in the brain, and also induces seasonal locomotor changes. In addition, 7α-hydroxypregnenolone mediates corticosterone action to increase locomotor activity under stress. This review summarizes the discovery, progress and prospect of 7α-hydroxypregnenolone, a new key regulator of amphibian locomotion.
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Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University and Center for Medical Life Science of Waseda University, Tokyo 162-8480, Japan.
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Haraguchi S, Koyama T, Hasunuma I, Okuyama SI, Ubuka T, Kikuyama S, Do Rego JL, Vaudry H, Tsutsui K. Acute stress increases the synthesis of 7α-hydroxypregnenolone, a new key neurosteroid stimulating locomotor activity, through corticosterone action in newts. Endocrinology 2012; 153:794-805. [PMID: 22128027 DOI: 10.1210/en.2011-1422] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
7α-Hydroxypregnenolone (7α-OH PREG) is a newly identified bioactive neurosteroid stimulating locomotor activity in the brain of newt, a wild animal, which serves as an excellent model to investigate the biosynthesis and biological action of neurosteroids. Here, we show that acute stress increases 7α-OH PREG synthesis in the dorsomedial hypothalamus (DMH) through corticosterone (CORT) action in newts. A 30-min restraint stress increased 7α-OH PREG synthesis in the brain tissue concomitant with the increase in plasma CORT concentrations. A 30-min restraint stress also increased the expression of cytochrome P450(7α) (CYP7B), the steroidogenic enzyme of 7α-OH PREG formation, in the DMH. Decreasing plasma CORT concentrations by hypophysectomy or trilostane administration decreased 7α-OH PREG synthesis in the diencephalon, whereas administration of CORT to these animals increased 7α-OH PREG synthesis. Glucocorticoid receptor was present in DMH neurons expressing CYP7B. Thus, CORT appears to act directly on DMH neurons to increase 7α-OH PREG synthesis. We further investigated the biological action of 7α-OH PREG in the brain under stress. A 30-min restraint stress or central administration of 7α-OH PREG increased serotonin concentrations in the diencephalon. Double immunolabeling further showed colocalization of CYP7B and serotonin in the DMH. These results indicate that acute stress increases the synthesis of 7α-OH PREG via CORT action in the DMH, and 7α-OH PREG activates serotonergic neurons in the DMH that may coordinate behavioral responses to stress. This is the first demonstration of neurosteroid biosynthesis regulated by peripheral steroid hormone and of neurosteroid action in the brain under stress in any vertebrate class.
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Affiliation(s)
- Shogo Haraguchi
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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Hubbard CS, Rose JD. Brainstem neuronal and behavioral activation by corticotropin-releasing hormone depend on the behavioral state of the animal. Horm Behav 2012; 61:121-33. [PMID: 22137972 PMCID: PMC4465356 DOI: 10.1016/j.yhbeh.2011.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 11/03/2011] [Accepted: 11/09/2011] [Indexed: 10/15/2022]
Abstract
Central administration of corticotropin-releasing hormone (CRH) is known to enhance locomotion across a wide range of vertebrates, including the roughskin newt, Taricha granulosa. The present study aimed to identify the CRH effects on locomotor-controlling medullary neurons that underlie the peptide's behavioral stimulating actions. Single neurons were recorded from the rostral medullary reticular formation before and after intraventricular infusion of CRH in freely behaving newts and newts paralyzed with a myoneural blocking agent. In behaving newts, most medullary neurons showed increased firing 3-23 min after CRH infusion. Decreases in firing were less common. Of particular importance was the finding that in behaving newts, medullary neurons showed a cyclic firing pattern that was strongly associated with an increase in the incidence of walking bouts, an effect blocked by pretreatment with the CRH antagonist, alpha-helical CRH and not seen following vehicle administration. In contrast, the majority of medullary neurons sampled in immobilized newts lacked temporal cyclicity in their firing patterns following intraventricular infusion of CRH. That is, there was no evidence for a fictive locomotor activity pattern. Our results indicate that the actual expression of locomotion is a critical factor in regulating the behavior-activating effects of CRH and underscore the importance of using an awake, unrestrained animal for analysis of a hormone's neurobehavioral actions.
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Haraguchi S, Matsunaga M, Vaudry H, Tsutsui K. Mode of action and functional significance of 7α-hydroxypregnenolone stimulating locomotor activity. Front Endocrinol (Lausanne) 2011; 2:23. [PMID: 22645507 PMCID: PMC3355833 DOI: 10.3389/fendo.2011.00023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Accepted: 08/04/2011] [Indexed: 11/13/2022] Open
Abstract
Previous studies over the past two decades have demonstrated that the brain and other nervous systems possess key steroidogenic enzymes and produces pregnenolone and other various neurosteroids in vertebrates in general. Recently, 7α-hydroxypregnenolone, a novel bioactive neurosteroid, was identified in the brain of newts and quail. Importantly, this novel neurosteroid is produced from pregnenolone through the enzymatic activity of cytochrome P450(7α) and acts on brain tissue as a neuronal modulator to stimulate locomotor activity in these vertebrates. Subsequently, the mode of action of 7α-hydroxypregnenolone was demonstrated. 7α-Hydroxypregnenolone stimulates locomotor activity through activation of the dopaminergic system. To understand the functional significance of 7α-hydroxypregnenolone in the regulation of locomotor activity, diurnal, and seasonal changes in 7α-hydroxypregnenolone synthesis were further characterized. Melatonin derived from the pineal gland and eyes regulates 7α-hydroxypregnenolone synthesis in the brain, thus inducing diurnal locomotor changes. Prolactin, an adenohypophyseal hormone, regulates 7α-hydroxypregnenolone synthesis in the brain, and also induces seasonal locomotor changes. In addition, 7α-hydroxypregnenolone mediates corticosterone action to modulate locomotor activity under stress. This review summarizes the current knowledge regarding the mode of action and functional significance of 7α-hydroxypregnenolone, a newly identified bioactive neurosteroid stimulating locomotor activity.
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Affiliation(s)
- Shogo Haraguchi
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda UniversityTokyo, Japan
| | - Masahiro Matsunaga
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda UniversityTokyo, Japan
| | - Hubert Vaudry
- Laboratory of Neuronal and Neuroendocrine Differentiation and Communication (INSERM U982), European Institute for Peptide Research, University of RouenMont-Saint-Aignan, France
| | - Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda UniversityTokyo, Japan
- *Correspondence: Kazuyoshi Tsutsui, Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, and Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan. e-mail:
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