The Experts below are selected from a list of 732 Experts worldwide ranked by ideXlab platform

Hiroshi Onimaru - One of the best experts on this subject based on the ideXlab platform.

  • Optogenetic analysis of Respiratory neuronal networks in the ventral medulla of neonatal rats producing channelrhodopsin in Phox2b-positive cells
    Pflügers Archiv - European Journal of Physiology, 2019
    Co-Authors: Keiko Ikeda, Hiroyuki Igarashi, Satoru Arata, Kiyoshi Kawakami, Kazuto Kobayashi, Masahiko Izumizaki, Hiroshi Onimaru
    Abstract:

    Paired-like homeobox gene Phox2b is predominantly expressed in pre-inspiratory neurons in the parafacial Respiratory group (pFRG) in newborn rat rostral ventrolateral medulla. To analyse detailed local networks of the Respiratory centre using optogenetics, the effects of selective activation of Phox2b-positive neurons in the ventral medulla on Respiratory Rhythm Generation were examined in brainstem–spinal cord preparations isolated from transgenic newborn rats with Phox2b-positive cells expressing channelrhodopsin variant ChRFR(C167A). Photostimulation up to 43 s increased the Respiratory rate > 200% of control, whereas short photostimulation (1.5 s) of the rostral pFRG reset the Respiratory Rhythm. At the cellular level, photostimulation depolarised Phox2b-positive pre-inspiratory, inspiratory and Respiratory-modulated tonic neurons and Phox2b-negative pre-inspiratory neurons. In contrast, changes in membrane potential of Phox2b-negative inspiratory and expiratory neurons varied depending on characteristics of ongoing synaptic connections in local Respiratory networks in the rostral medulla. In the presence of tetrodotoxin, photostimulation depolarised Phox2b-positive cells, but caused no significant changes in membrane potential of Phox2b-negative cells. We concluded that depolarisation of Phox2b-positive neurons was due to cell-autonomous photo-activation and summation of excitatory postsynaptic potentials, whereas membrane potential changes of Phox2b-negative neurons depended on the network configuration. Our findings shed further light on local networks among Respiratory-related neurons in the rostral ventrolateral medulla and emphasise the important role of pre-inspiratory neurons in Respiratory Rhythm Generation in the neonatal rat en bloc preparation.

  • Knockout of sodium pump α3 subunit gene (Atp1a3−/−) results in perinatal seizure and defective Respiratory Rhythm Generation
    Brain research, 2017
    Co-Authors: Keiko Ikeda, Hiroshi Onimaru, Kiyoshi Kawakami
    Abstract:

    ATP1A3 encodes a neuron-specific human α3 subunit isoform of the sodium pump that plays an important role in neuronal excitability. Point and deletion mutations in ATP1A3 have been recognized in diverse neurological disorders. Three ATP1A3 disorders, alternating hemiplegia of childhood (AHC); apnea; and severe infantile epileptic encephalopathy often appear shortly after birth. To gain insight into the pathophysiology of these disorders and to understand the functional roles of the sodium pump α3 subunit in the brain in vivo during this period of development, we examined the phenotype of Atp1a3 knockout homozygous mouse fetuses (Atp1a3-/-). We focused on fetuses just before birth because at birth, about half of them showed severe seizure, and none could continue effective breathing and died soon after birth, without any gross anatomical anomalies. We examined c-Fos expression in the brains of Atp1a3-/- and found a significantly increased number of c-Fos-expressing cells in various regions of the brains, with unique distribution in the cerebellum, when compared with wild-type littermates (Atp1a3+/+). We also measured contents of monoamine neurotransmitters in the brains and found higher contents, especially of dopamine and noradrenaline, in the brains of Atp1a3-/- compared with those of Atp1a3+/+. In addition, we found various abnormal Respiratory Rhythms produced in the brainstem of Atp1a3-/-. These results suggest that Atp1a3 plays a critical role in neural function during development and at birth.

  • Effects of a TRPV1 agonist capsaicin on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats
    Pflügers Archiv - European Journal of Physiology, 2017
    Co-Authors: Mariho Tani, Kiyoshi Kawakami, Keiko Ikeda, Sayumi Kotani, Chikara Hayakawa, Saki Irie, Hiroshi Onimaru
    Abstract:

    The heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channels are expressed in the peripheral and central nervous systems. However, there is no report on how the activation of TRPV1 causes the modulation of neuronal activity in the medullary Respiratory center. We examined effects of capsaicin, a specific agonist of TRPV1 channels, on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats. Capsaicin induced a biphasic response in the Respiratory Rhythm (a transient decrease followed by an increase in the C4 rate). The second-phase excitatory effect (but not the initial inhibitory effect) in the biphasic response was partly blocked by capsazepine or AMG9810 (TRPV1 antagonists). Capsaicin caused strong desensitization. After its washout, the strength of C4 burst inspiratory activity was augmented once per four to five Respiratory cycles. The preinspiratory and inspiratory neurons showed tonic firings due to membrane depolarization during the initial inhibitory phase. In the presence of TTX, capsaicin increased the fluctuation of the membrane potential of the CO_2-sensitive preinspiratory neurons in the parafacial Respiratory group (pFRG), accompanied by slight depolarization. The C4 inspiratory activity did not stop, even 60–90 min after the application of 50/100 μM capsaicin. Voltage-sensitive dye imaging demonstrated that the spatiotemporal pattern of the Respiratory Rhythm generating networks after application of capsaicin (50 μM, 70–90 min) was highly similar to the control. A histochemical analysis using TRPV1 channel protein antibodies and mRNA demonstrated that the TRPV1 channel-positive cells were widely distributed in the reticular formation of the medulla, including the pFRG. Our results showed that the application of capsaicin in the medulla has various influences on the Respiratory center: transient inhibitory and subsequent excitatory effects on the Respiratory Rhythm and periodical augmentation of the inspiratory burst pattern. The effects of capsaicin were partially blocked by TRPV1 antagonists but could be also induced at least partially via the non-specific action. Our results also suggested a minor contribution of the TRPV1 channels to central chemoreception.

  • effects of α2 adorenoceptor agonist dexmedetomidine on Respiratory Rhythm Generation of newborn rats
    Neuroscience Letters, 2015
    Co-Authors: Kayo Tsuzawa, Yoshino Minoura, Shinhiro Takeda, Katsunori Inagaki, Hiroshi Onimaru
    Abstract:

    Dexmedetomidine, an α2-adrenoceptor agonist which has a slight side effect on breathing, is clinically used as an analgesic and sedative agent. Previous studies have shown depressing or modest effects of α2-adorenoceptor agonists on Respiratory Rhythm Generation in newborn rat preparation in vitro. In contrast, it was recently reported that dexmedetomidine induced long-lasting activation of Respiratory Rhythm in brainstem-spinal cord preparation isolated from neonatal mice. In the present study, we examined whether dexmedetomidine induces any effects on Respiratory Rhythm in brainstem-spinal cord preparation isolated from newborn rats. We also examined the effects of dexmedetomidine on reflex response in the spinal cord, which is presumed to be an indication of nociceptive response. We found that the administration of dexmedetomidine, at the range of 0.1-10μM, dose-dependently depressed Respiratory Rhythm and that the inhibitory effect was reversed by atipamezole, an α2-adorenoceptor antagonist. Spinal cord reflex responses were depressed by the application of dexmedetomidine at the range of 0.1-1nM, a lower concentration than that affecting Respiratory Rhythm. The inhibitory effect was also reversed by atipamezole. Our findings provide neuronal mechanisms that support the clinical use of dexmedetomidine, which shows sedative and antinociceptive effects with minimal side effects on breathing.

  • effects of riluzole on Respiratory Rhythm Generation in the brainstem spinal cord preparation from newborn rat
    Neuroscience Research, 2015
    Co-Authors: Shih Tien Lin, Hiroshi Onimaru
    Abstract:

    The persistent sodium channel is an important pacemaker component in Rhythm Generation. In the present study, we examined the effects of a persistent sodium channel blocker, riluzole on pre-inspiratory (Pre-I) and inspiratory neurons in the rostral medulla as well as on 4th cervical ventral root (C4)-inspiratory activity in brainstem-spinal cord preparations. Preparations were isolated from postnatal day 0-3 Wistar rats and were superfused with artificial cerebrospinal fluid, equilibrated with 95% O2 and 5% CO2, pH 7.4, at 25-26 °C. The C4 inspiratory burst rate decreased in a dose-dependent manner (50-200 μM) after 15 min application of riluzole. Riluzole caused a strong reduction in the drive potential of Pre-I neurons but not of inspiratory neurons. After washout, C4 inspiratory burst gradually changed into an episodic pattern, in which one burst consisted of 3-9 short separate bursts. Riluzole also depressed the induction of repetitive firing induced by depolarizing stimulation. Under voltage clamp conditions, riluzole suppressed the negative-slope component of Pre-I neurons. Riluzole also depressed the intrinsic burst Generation of Pre-I neurons in low calcium and high magnesium solution. Our findings indicate that the burst Generation of Pre-I neurons is more sensitive than inspiratory burst Generation to riluzole and thus suggested that persistent sodium channels have an important role in the burst Generation of Pre-I neurons and are involved in the primary Respiratory Rhythm Generation.

Kiyoshi Kawakami - One of the best experts on this subject based on the ideXlab platform.

  • Optogenetic analysis of Respiratory neuronal networks in the ventral medulla of neonatal rats producing channelrhodopsin in Phox2b-positive cells
    Pflügers Archiv - European Journal of Physiology, 2019
    Co-Authors: Keiko Ikeda, Hiroyuki Igarashi, Satoru Arata, Kiyoshi Kawakami, Kazuto Kobayashi, Masahiko Izumizaki, Hiroshi Onimaru
    Abstract:

    Paired-like homeobox gene Phox2b is predominantly expressed in pre-inspiratory neurons in the parafacial Respiratory group (pFRG) in newborn rat rostral ventrolateral medulla. To analyse detailed local networks of the Respiratory centre using optogenetics, the effects of selective activation of Phox2b-positive neurons in the ventral medulla on Respiratory Rhythm Generation were examined in brainstem–spinal cord preparations isolated from transgenic newborn rats with Phox2b-positive cells expressing channelrhodopsin variant ChRFR(C167A). Photostimulation up to 43 s increased the Respiratory rate > 200% of control, whereas short photostimulation (1.5 s) of the rostral pFRG reset the Respiratory Rhythm. At the cellular level, photostimulation depolarised Phox2b-positive pre-inspiratory, inspiratory and Respiratory-modulated tonic neurons and Phox2b-negative pre-inspiratory neurons. In contrast, changes in membrane potential of Phox2b-negative inspiratory and expiratory neurons varied depending on characteristics of ongoing synaptic connections in local Respiratory networks in the rostral medulla. In the presence of tetrodotoxin, photostimulation depolarised Phox2b-positive cells, but caused no significant changes in membrane potential of Phox2b-negative cells. We concluded that depolarisation of Phox2b-positive neurons was due to cell-autonomous photo-activation and summation of excitatory postsynaptic potentials, whereas membrane potential changes of Phox2b-negative neurons depended on the network configuration. Our findings shed further light on local networks among Respiratory-related neurons in the rostral ventrolateral medulla and emphasise the important role of pre-inspiratory neurons in Respiratory Rhythm Generation in the neonatal rat en bloc preparation.

  • Knockout of sodium pump α3 subunit gene (Atp1a3−/−) results in perinatal seizure and defective Respiratory Rhythm Generation
    Brain research, 2017
    Co-Authors: Keiko Ikeda, Hiroshi Onimaru, Kiyoshi Kawakami
    Abstract:

    ATP1A3 encodes a neuron-specific human α3 subunit isoform of the sodium pump that plays an important role in neuronal excitability. Point and deletion mutations in ATP1A3 have been recognized in diverse neurological disorders. Three ATP1A3 disorders, alternating hemiplegia of childhood (AHC); apnea; and severe infantile epileptic encephalopathy often appear shortly after birth. To gain insight into the pathophysiology of these disorders and to understand the functional roles of the sodium pump α3 subunit in the brain in vivo during this period of development, we examined the phenotype of Atp1a3 knockout homozygous mouse fetuses (Atp1a3-/-). We focused on fetuses just before birth because at birth, about half of them showed severe seizure, and none could continue effective breathing and died soon after birth, without any gross anatomical anomalies. We examined c-Fos expression in the brains of Atp1a3-/- and found a significantly increased number of c-Fos-expressing cells in various regions of the brains, with unique distribution in the cerebellum, when compared with wild-type littermates (Atp1a3+/+). We also measured contents of monoamine neurotransmitters in the brains and found higher contents, especially of dopamine and noradrenaline, in the brains of Atp1a3-/- compared with those of Atp1a3+/+. In addition, we found various abnormal Respiratory Rhythms produced in the brainstem of Atp1a3-/-. These results suggest that Atp1a3 plays a critical role in neural function during development and at birth.

  • Effects of a TRPV1 agonist capsaicin on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats
    Pflügers Archiv - European Journal of Physiology, 2017
    Co-Authors: Mariho Tani, Kiyoshi Kawakami, Keiko Ikeda, Sayumi Kotani, Chikara Hayakawa, Saki Irie, Hiroshi Onimaru
    Abstract:

    The heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channels are expressed in the peripheral and central nervous systems. However, there is no report on how the activation of TRPV1 causes the modulation of neuronal activity in the medullary Respiratory center. We examined effects of capsaicin, a specific agonist of TRPV1 channels, on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats. Capsaicin induced a biphasic response in the Respiratory Rhythm (a transient decrease followed by an increase in the C4 rate). The second-phase excitatory effect (but not the initial inhibitory effect) in the biphasic response was partly blocked by capsazepine or AMG9810 (TRPV1 antagonists). Capsaicin caused strong desensitization. After its washout, the strength of C4 burst inspiratory activity was augmented once per four to five Respiratory cycles. The preinspiratory and inspiratory neurons showed tonic firings due to membrane depolarization during the initial inhibitory phase. In the presence of TTX, capsaicin increased the fluctuation of the membrane potential of the CO_2-sensitive preinspiratory neurons in the parafacial Respiratory group (pFRG), accompanied by slight depolarization. The C4 inspiratory activity did not stop, even 60–90 min after the application of 50/100 μM capsaicin. Voltage-sensitive dye imaging demonstrated that the spatiotemporal pattern of the Respiratory Rhythm generating networks after application of capsaicin (50 μM, 70–90 min) was highly similar to the control. A histochemical analysis using TRPV1 channel protein antibodies and mRNA demonstrated that the TRPV1 channel-positive cells were widely distributed in the reticular formation of the medulla, including the pFRG. Our results showed that the application of capsaicin in the medulla has various influences on the Respiratory center: transient inhibitory and subsequent excitatory effects on the Respiratory Rhythm and periodical augmentation of the inspiratory burst pattern. The effects of capsaicin were partially blocked by TRPV1 antagonists but could be also induced at least partially via the non-specific action. Our results also suggested a minor contribution of the TRPV1 channels to central chemoreception.

  • RESEARCH ARTICLE A Phox2b BAC Transgenic Rat Line Useful for Understanding Respiratory Rhythm Generator Neural Circuitry
    2016
    Co-Authors: Keiko Ikeda, Hiroyuki Igarashi, Satoru Arata, Masanori Takahashi, Shigeru Sato, Toru Ishizuka, Hiromu Yawo, Michelle E. Southard-smith, Kiyoshi Kawakami
    Abstract:

    The key role of the Respiratory neural center is Respiratory Rhythm Generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for Respiratory Rhythm Generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial Respiratory group (pFRG) and the pre-Bötzinger complex group (preBötC). The pFRG partially overlaps in the retrotra-pezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a tran-scription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is charac-terized by blunted ventilatory response to hypercapnia. Here we describe the Generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cell

  • a phox2b bac transgenic rat line useful for understanding Respiratory Rhythm generator neural circuitry
    PLOS ONE, 2015
    Co-Authors: Hiroyuki Igarashi, Satoru Arata, Keiko Ikeda, Masanori Takahashi, Shigeru Sato, Toru Ishizuka, Hiromu Yawo, Michelle E Southardsmith, Kiyoshi Kawakami
    Abstract:

    The key role of the Respiratory neural center is Respiratory Rhythm Generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for Respiratory Rhythm Generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial Respiratory group (pFRG) and the pre-Botzinger complex group (preBotC). The pFRG partially overlaps in the retrotrapezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a transcription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is characterized by blunted ventilatory response to hypercapnia. Here we describe the Generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cells during development, it is a potentially powerful tool for dissecting the entire picture of the Respiratory neural network during development and for identifying the CO2/O2 sensor molecules in the adult central and peripheral nervous systems.

Keiko Ikeda - One of the best experts on this subject based on the ideXlab platform.

  • Optogenetic analysis of Respiratory neuronal networks in the ventral medulla of neonatal rats producing channelrhodopsin in Phox2b-positive cells
    Pflügers Archiv - European Journal of Physiology, 2019
    Co-Authors: Keiko Ikeda, Hiroyuki Igarashi, Satoru Arata, Kiyoshi Kawakami, Kazuto Kobayashi, Masahiko Izumizaki, Hiroshi Onimaru
    Abstract:

    Paired-like homeobox gene Phox2b is predominantly expressed in pre-inspiratory neurons in the parafacial Respiratory group (pFRG) in newborn rat rostral ventrolateral medulla. To analyse detailed local networks of the Respiratory centre using optogenetics, the effects of selective activation of Phox2b-positive neurons in the ventral medulla on Respiratory Rhythm Generation were examined in brainstem–spinal cord preparations isolated from transgenic newborn rats with Phox2b-positive cells expressing channelrhodopsin variant ChRFR(C167A). Photostimulation up to 43 s increased the Respiratory rate > 200% of control, whereas short photostimulation (1.5 s) of the rostral pFRG reset the Respiratory Rhythm. At the cellular level, photostimulation depolarised Phox2b-positive pre-inspiratory, inspiratory and Respiratory-modulated tonic neurons and Phox2b-negative pre-inspiratory neurons. In contrast, changes in membrane potential of Phox2b-negative inspiratory and expiratory neurons varied depending on characteristics of ongoing synaptic connections in local Respiratory networks in the rostral medulla. In the presence of tetrodotoxin, photostimulation depolarised Phox2b-positive cells, but caused no significant changes in membrane potential of Phox2b-negative cells. We concluded that depolarisation of Phox2b-positive neurons was due to cell-autonomous photo-activation and summation of excitatory postsynaptic potentials, whereas membrane potential changes of Phox2b-negative neurons depended on the network configuration. Our findings shed further light on local networks among Respiratory-related neurons in the rostral ventrolateral medulla and emphasise the important role of pre-inspiratory neurons in Respiratory Rhythm Generation in the neonatal rat en bloc preparation.

  • Knockout of sodium pump α3 subunit gene (Atp1a3−/−) results in perinatal seizure and defective Respiratory Rhythm Generation
    Brain research, 2017
    Co-Authors: Keiko Ikeda, Hiroshi Onimaru, Kiyoshi Kawakami
    Abstract:

    ATP1A3 encodes a neuron-specific human α3 subunit isoform of the sodium pump that plays an important role in neuronal excitability. Point and deletion mutations in ATP1A3 have been recognized in diverse neurological disorders. Three ATP1A3 disorders, alternating hemiplegia of childhood (AHC); apnea; and severe infantile epileptic encephalopathy often appear shortly after birth. To gain insight into the pathophysiology of these disorders and to understand the functional roles of the sodium pump α3 subunit in the brain in vivo during this period of development, we examined the phenotype of Atp1a3 knockout homozygous mouse fetuses (Atp1a3-/-). We focused on fetuses just before birth because at birth, about half of them showed severe seizure, and none could continue effective breathing and died soon after birth, without any gross anatomical anomalies. We examined c-Fos expression in the brains of Atp1a3-/- and found a significantly increased number of c-Fos-expressing cells in various regions of the brains, with unique distribution in the cerebellum, when compared with wild-type littermates (Atp1a3+/+). We also measured contents of monoamine neurotransmitters in the brains and found higher contents, especially of dopamine and noradrenaline, in the brains of Atp1a3-/- compared with those of Atp1a3+/+. In addition, we found various abnormal Respiratory Rhythms produced in the brainstem of Atp1a3-/-. These results suggest that Atp1a3 plays a critical role in neural function during development and at birth.

  • Effects of a TRPV1 agonist capsaicin on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats
    Pflügers Archiv - European Journal of Physiology, 2017
    Co-Authors: Mariho Tani, Kiyoshi Kawakami, Keiko Ikeda, Sayumi Kotani, Chikara Hayakawa, Saki Irie, Hiroshi Onimaru
    Abstract:

    The heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channels are expressed in the peripheral and central nervous systems. However, there is no report on how the activation of TRPV1 causes the modulation of neuronal activity in the medullary Respiratory center. We examined effects of capsaicin, a specific agonist of TRPV1 channels, on Respiratory Rhythm Generation in brainstem-spinal cord preparation from newborn rats. Capsaicin induced a biphasic response in the Respiratory Rhythm (a transient decrease followed by an increase in the C4 rate). The second-phase excitatory effect (but not the initial inhibitory effect) in the biphasic response was partly blocked by capsazepine or AMG9810 (TRPV1 antagonists). Capsaicin caused strong desensitization. After its washout, the strength of C4 burst inspiratory activity was augmented once per four to five Respiratory cycles. The preinspiratory and inspiratory neurons showed tonic firings due to membrane depolarization during the initial inhibitory phase. In the presence of TTX, capsaicin increased the fluctuation of the membrane potential of the CO_2-sensitive preinspiratory neurons in the parafacial Respiratory group (pFRG), accompanied by slight depolarization. The C4 inspiratory activity did not stop, even 60–90 min after the application of 50/100 μM capsaicin. Voltage-sensitive dye imaging demonstrated that the spatiotemporal pattern of the Respiratory Rhythm generating networks after application of capsaicin (50 μM, 70–90 min) was highly similar to the control. A histochemical analysis using TRPV1 channel protein antibodies and mRNA demonstrated that the TRPV1 channel-positive cells were widely distributed in the reticular formation of the medulla, including the pFRG. Our results showed that the application of capsaicin in the medulla has various influences on the Respiratory center: transient inhibitory and subsequent excitatory effects on the Respiratory Rhythm and periodical augmentation of the inspiratory burst pattern. The effects of capsaicin were partially blocked by TRPV1 antagonists but could be also induced at least partially via the non-specific action. Our results also suggested a minor contribution of the TRPV1 channels to central chemoreception.

  • RESEARCH ARTICLE A Phox2b BAC Transgenic Rat Line Useful for Understanding Respiratory Rhythm Generator Neural Circuitry
    2016
    Co-Authors: Keiko Ikeda, Hiroyuki Igarashi, Satoru Arata, Masanori Takahashi, Shigeru Sato, Toru Ishizuka, Hiromu Yawo, Michelle E. Southard-smith, Kiyoshi Kawakami
    Abstract:

    The key role of the Respiratory neural center is Respiratory Rhythm Generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for Respiratory Rhythm Generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial Respiratory group (pFRG) and the pre-Bötzinger complex group (preBötC). The pFRG partially overlaps in the retrotra-pezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a tran-scription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is charac-terized by blunted ventilatory response to hypercapnia. Here we describe the Generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cell

  • a phox2b bac transgenic rat line useful for understanding Respiratory Rhythm generator neural circuitry
    PLOS ONE, 2015
    Co-Authors: Hiroyuki Igarashi, Satoru Arata, Keiko Ikeda, Masanori Takahashi, Shigeru Sato, Toru Ishizuka, Hiromu Yawo, Michelle E Southardsmith, Kiyoshi Kawakami
    Abstract:

    The key role of the Respiratory neural center is Respiratory Rhythm Generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for Respiratory Rhythm Generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial Respiratory group (pFRG) and the pre-Botzinger complex group (preBotC). The pFRG partially overlaps in the retrotrapezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a transcription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is characterized by blunted ventilatory response to hypercapnia. Here we describe the Generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cells during development, it is a potentially powerful tool for dissecting the entire picture of the Respiratory neural network during development and for identifying the CO2/O2 sensor molecules in the adult central and peripheral nervous systems.

Jan-marino Ramirez - One of the best experts on this subject based on the ideXlab platform.

  • Respiratory Rhythm Generation
    2019
    Co-Authors: D W Richter, Klaus Ballanyi, Jan-marino Ramirez
    Abstract:

    The central mechanisms generating the Respiratory Rhythm require a high degree of coordination of synaptic interactions and specific membrane properties of Respiratory neurons. This chapter deals with our opinions concerning the mechanisms underlying Rhythm Generation and the processes of dynamic adjustment of Respiratory neuronal activity in neonatal and mature mammals as analyzed under in vivo and in vitro conditions. The bulbar network consists of six populations of Respiratory neurons which have been characterized in the cat by the timing and pattern of their respiration-related membrane potential changes and action potential burst discharges. They are pre-inspiratory, early-inspiratory, throughout-inspiratory, late-inspiratory, post-inspiratory, and expiratory neurons. The diversity of results dealing with the importance of synaptic inhibition for Rhythm Generation seems to be explained by differences in the experimental conditions, the analyses either being performed in vitro or in vivo on the intact Respiratory network that is interconnected with many other structures.

  • the dynamic basis of Respiratory Rhythm Generation one breath at a time
    Annual Review of Neuroscience, 2018
    Co-Authors: Jan-marino Ramirez, Nathan A Baertsch
    Abstract:

    Rhythmicity is a universal timing mechanism in the brain, and the Rhythmogenic mechanisms are generally dynamic. This is illustrated for the neuronal control of breathing, a behavior that occurs as a one-, two-, or three-phase Rhythm. Each breath is assembled stochastically, and increasing evidence suggests that each phase can be generated independently by a dedicated excitatory microcircuit. Within each microcircuit, Rhythmicity emerges through three entangled mechanisms: (a) glutamatergic transmission, which is amplified by (b) intrinsic bursting and opposed by (c) concurrent inhibition. This Rhythmogenic triangle is dynamically tuned by neuromodulators and other network interactions. The ability of coupled oscillators to reconfigure and recombine may allow breathing to remain robust yet plastic enough to conform to nonventilatory behaviors such as vocalization, swallowing, and coughing. Lessons learned from the Respiratory network may translate to other highly dynamic and integrated Rhythmic systems, i...

  • Respiratory Rhythm Generation: triple oscillator hypothesis
    F1000Research, 2017
    Co-Authors: Tatiana M. Anderson, Jan-marino Ramirez
    Abstract:

    Breathing is vital for survival but also interesting from the perspective of Rhythm Generation. This Rhythmic behavior is generated within the brainstem and is thought to emerge through the interaction between independent oscillatory neuronal networks. In mammals, breathing is composed of three phases – inspiration, post-inspiration, and active expiration – and this article discusses the concept that each phase is generated by anatomically distinct Rhythm-generating networks: the preBotzinger complex (preBotC), the post-inspiratory complex (PiCo), and the lateral parafacial nucleus (pF L ), respectively. The preBotC was first discovered 25 years ago and was shown to be both necessary and sufficient for the Generation of inspiration. More recently, networks have been described that are responsible for post-inspiration and active expiration. Here, we attempt to collate the current knowledge and hypotheses regarding how Respiratory Rhythms are generated, the role that inhibition plays, and the interactions between the medullary networks. Our considerations may have implications for Rhythm Generation in general.

  • Respiratory Rhythm Generation: triple oscillator hypothesis [version 1; referees: 3 approved]
    F1000 Research Ltd, 2017
    Co-Authors: Tatiana M. Anderson, Jan-marino Ramirez
    Abstract:

    Breathing is vital for survival but also interesting from the perspective of Rhythm Generation. This Rhythmic behavior is generated within the brainstem and is thought to emerge through the interaction between independent oscillatory neuronal networks. In mammals, breathing is composed of three phases – inspiration, post-inspiration, and active expiration – and this article discusses the concept that each phase is generated by anatomically distinct Rhythm-generating networks: the preBötzinger complex (preBötC), the post-inspiratory complex (PiCo), and the lateral parafacial nucleus (pFL), respectively. The preBötC was first discovered 25 years ago and was shown to be both necessary and sufficient for the Generation of inspiration. More recently, networks have been described that are responsible for post-inspiration and active expiration. Here, we attempt to collate the current knowledge and hypotheses regarding how Respiratory Rhythms are generated, the role that inhibition plays, and the interactions between the medullary networks. Our considerations may have implications for Rhythm Generation in general

  • microcircuits in Respiratory Rhythm Generation commonalities with other Rhythm generating networks and evolutionary perspectives
    Current Opinion in Neurobiology, 2016
    Co-Authors: Jan-marino Ramirez, Tatiana Dashevskiy, Ibis Agosto Marlin, Nathan A Baertsch
    Abstract:

    Rhythmicity is critical for the Generation of Rhythmic behaviors and higher brain functions. This review discusses common mechanisms of Rhythm Generation, including the role of synaptic inhibition and excitation, with a focus on the mammalian Respiratory network. This network generates three phases of breathing and is highly integrated with brain regions associated with numerous non-ventilatory behaviors. We hypothesize that during evolution multiple Rhythmogenic microcircuits were recruited to accommodate the Generation of each breathing phase. While these microcircuits relied primarily on excitatory mechanisms, synaptic inhibition became increasingly important to coordinate the different microcircuits and to integrate breathing into a rich behavioral repertoire that links breathing to sensory processing, arousal, and emotions as well as learning and memory.

Jack L. Feldman - One of the best experts on this subject based on the ideXlab platform.

  • synaptically activated burst generating conductances may underlie a group pacemaker mechanism for Respiratory Rhythm Generation in mammals
    Progress in Brain Research, 2010
    Co-Authors: Christopher A. Del Negro, John A. Hayes, Benjamin R. Brush, Ryland W Pace, Ryoichi Teruyama, Jack L. Feldman
    Abstract:

    Abstract Breathing, chewing, and walking are critical life-sustaining behaviors in mammals that consist essentially of simple Rhythmic movements. Breathing movements in particular involve the diaphragm, thorax, and airways but emanate from a network in the lower brain stem. This network can be studied in reduced preparations in vitro and using simplified mathematical models that make testable predictions. An iterative approach that employs both in vitro and in silico models argues against canonical mechanisms for Respiratory Rhythm in neonatal rodents that involve reciprocal inhibition and pacemaker properties. We present an alternative model in which emergent network properties play a Rhythmogenic role. Specifically, we show evidence that synaptically activated burst-generating conductances—which are only available in the context of network activity—engender robust periodic bursts in Respiratory neurons. Because the cellular burst-generating mechanism is linked to network synaptic drive we dub this type of system a group pacemaker.

  • role of persistent sodium current in mouse prebotzinger complex neurons and Respiratory Rhythm Generation
    The Journal of Physiology, 2007
    Co-Authors: Ryland W Pace, Jack L. Feldman, Christopher A Del Negro, Devin D Mackay
    Abstract:

    Breathing movements in mammals depend on Respiratory neurons in the preBotzinger Complex (preBotC), which comprise a Rhythmic network and generate robust bursts that form the basis for inspiration. Persistent Na+ current (INaP) is widespread in the preBotC and is hypothesized to play a critical role in Rhythm Generation because of its subthreshold activation and slow inactivation properties that putatively promote long-lasting burst depolarizations. In neonatal mouse slice preparations that retain the preBotC and generate a Respiratory-related Rhythm, we tested the role of INaP with multiple Na+ channel antagonists: tetrodotoxin (TTX; 20 nm), riluzole (RIL; 10 μm), and the intracellular Na+ channel antagonist QX-314 (2 mm). Here we show that INaP promotes intraburst spiking in preBotC neurons but surprisingly does not contribute to the depolarization that underlies inspiratory bursts, i.e. the inspiratory drive potential. Local microinjection in the preBotC of 10 μm RIL or 20 nm TTX does not perturb Respiratory frequency, even in the presence of bath-applied 100 μm flufenamic acid (FFA), which attenuates a Ca2+-activated non-specific cation current (ICAN) that may also have burst-generating functionality. These data contradict the hypothesis that INaP in preBotC neurons is obligatory for Rhythmogenesis. However, in the presence of FFA, local microinjection of 10 μm RIL in the raphe obscurus causes Rhythm cessation, which suggests that INaP regulates the excitability of neurons outside the preBotC, including serotonergic raphe neurons that project to, and help maintain, Rhythmic preBotC function.

  • sodium and calcium current mediated pacemaker neurons and Respiratory Rhythm Generation
    The Journal of Neuroscience, 2005
    Co-Authors: Christopher A Del Negro, John A. Hayes, Ryland W Pace, Consuelo Morgadovalle, Devin D Mackay, Erin A Crowder, Jack L. Feldman
    Abstract:

    The breathing motor pattern in mammals originates in brainstem networks. Whether pacemaker neurons play an obligatory role remains a key unanswered question. We performed whole-cell recordings in the preBotzinger Complex in slice preparations from neonatal rodents and tested for pacemaker activity. We observed persistent Na + current ( I NaP )-mediated bursting in ∼5% of inspiratory neurons in postnatal day 0 (P0)-P5 and in P8-P10 slices. I NaP -mediated bursting was voltage dependent and blocked by 20 μm riluzole (RIL). We found Ca 2+ current ( I Ca )-dependent bursting in 7.5% of inspiratory neurons in P8-P10 slices, but in P0-P5 slices these cells were exceedingly rare (0.6%). This bursting was voltage independent and blocked by 100 μm Cd 2+ or flufenamic acid (FFA) (10-200 μm), which suggests that a Ca 2+ -activated inward cationic current ( I CAN ) underlies burst Generation. These data substantiate our observation that P0-P5 slices exposed to RIL contain few (if any) pacemaker neurons, yet maintain Respiratory Rhythm. We also show that 20 nm TTX or coapplication of 20 μm RIL + FFA (100-200 μm) stops the Respiratory Rhythm, but that adding 2 μm substance P restarts it. We conclude that I NaP and I CAN enhance neuronal excitability and promote Rhythmogenesis, even if their magnitude is insufficient to support bursting-pacemaker activity in individual neurons. When I NaP and I CAN are removed pharmacologically, the Rhythm can be maintained by boosting neural excitability, which is inconsistent with a pacemaker-essential mechanism of Respiratory Rhythmogenesis by the preBotzinger complex.

  • sodium and calcium current mediated pacemaker neurons and Respiratory Rhythm Generation
    The Journal of Neuroscience, 2005
    Co-Authors: Christopher A. Del Negro, John A. Hayes, Ryland W Pace, Consuelo Morgadovalle, Devin D Mackay, Erin A Crowder, Jack L. Feldman
    Abstract:

    The breathing motor pattern in mammals originates in brainstem networks. Whether pacemaker neurons play an obligatory role remains a key unanswered question. We performed whole-cell recordings in the preBotzinger Complex in slice preparations from neonatal rodents and tested for pacemaker activity. We observed persistent Na+ current (I(NaP))-mediated bursting in approximately 5% of inspiratory neurons in postnatal day 0 (P0)-P5 and in P8-P10 slices. I(NaP)-mediated bursting was voltage dependent and blocked by 20 mum riluzole (RIL). We found Ca2+ current (I(Ca))-dependent bursting in 7.5% of inspiratory neurons in P8-P10 slices, but in P0-P5 slices these cells were exceedingly rare (0.6%). This bursting was voltage independent and blocked by 100 microm Cd2+ or flufenamic acid (FFA) (10-200 microm), which suggests that a Ca2+-activated inward cationic current (I(CAN)) underlies burst Generation. These data substantiate our observation that P0-P5 slices exposed to RIL contain few (if any) pacemaker neurons, yet maintain Respiratory Rhythm. We also show that 20 nm TTX or coapplication of 20 microm RIL + FFA (100-200 microm) stops the Respiratory Rhythm, but that adding 2 mum substance P restarts it. We conclude that I(NaP) and I(CAN) enhance neuronal excitability and promote Rhythmogenesis, even if their magnitude is insufficient to support bursting-pacemaker activity in individual neurons. When I(NaP) and I(CAN) are removed pharmacologically, the Rhythm can be maintained by boosting neural excitability, which is inconsistent with a pacemaker-essential mechanism of Respiratory Rhythmogenesis by the preBotzinger complex.

  • opioid induced quantal slowing reveals dual networks for Respiratory Rhythm Generation
    Neuron, 2003
    Co-Authors: Nicholas M Mellen, Wiktor A Janczewski, Christopher M Bocchiaro, Jack L. Feldman
    Abstract:

    Current consensus holds that a single medullary network generates Respiratory Rhythm in mammals. Pre-Botzinger Complex inspiratory (I) neurons, isolated in transverse slices, and preinspiratory (pre-I) neurons, found only in more intact en bloc preparations and in vivo, are each proposed as necessary for Rhythm Generation. Opioids slow I, but not pre-I, neuronal burst periods. In slices, opioids gradually lengthened Respiratory periods, whereas in more intact preparations, periods jumped nondeterministically to integer multiples of the control period (quantal slowing). These findings suggest that opioid-induced quantal slowing results from transmission failure of Rhythmic drive from pre-I neurons to preBotC I networks, depressed below threshold for spontaneous Rhythmic activity. Thus, both I (in the slice), and pre-I neurons are sufficient for Respiratory Rhythmogenesis.