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Whitaker-Fornek JR, Nelson JK, Pilarski JQ. Chloride Modulates Central pH Sensitivity and Plasticity of Brainstem Breathing-Related Biorhythms in Zebra Finch Embryos. Dev Psychobiol 2024; 66:e22518. [PMID: 38924086 PMCID: PMC11210689 DOI: 10.1002/dev.22518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 05/26/2024] [Accepted: 05/28/2024] [Indexed: 06/28/2024]
Abstract
All terrestrial vertebrate life must transition from aquatic gas exchange in the embryonic environment to aerial or pulmonary respiration at birth. In addition to being able to breathe air, neonates must possess functional sensory feedback systems for maintaining acid-base balance. Respiratory neurons in the brainstem act as pH sensors that can adjust breathing to regulate systemic pH. The central pH sensitivity of breathing-related motor output develops over the embryonic period in the zebra finch (Taeniopygia guttata). Due to the key role of chloride ions in electrochemical stability and developmental plasticity, we tested chloride's role in the development of central pH sensitivity. We blocked gamma-aminobutyric acid-A receptors and cation-chloride cotransport that subtly modulated the low-pH effects on early breathing biorhythms. Further, chloride-free artificial cerebrospinal fluid altered the pattern and timing of breathing biorhythms and blocked the stimulating effect of acidosis in E12-14 brainstems. Early and middle stage embryos exhibited rebound plasticity in brainstem motor outputs during low-pH treatment, which was eliminated by chloride-free solution. Results show that chloride modulates low-pH sensitivity and rebound plasticity in the zebra finch embryonic brainstem, but work is needed to determine the cellular and circuit mechanisms that control functional chloride balance during acid-base disturbances.
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Affiliation(s)
| | - Jennie K. Nelson
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho
| | - Jason Q. Pilarski
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho
- Department of Dental Sciences, Idaho State University, Pocatello, Idaho
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2
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Saunders SE, Santin JM. Compensatory changes in GABAergic inhibition are differentially expressed in the respiratory network to promote function following hibernation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.09.561534. [PMID: 37873475 PMCID: PMC10592683 DOI: 10.1101/2023.10.09.561534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The respiratory network must produce consistent output throughout an animal's life. Although respiratory motor plasticity is well appreciated, how plasticity mechanisms are organized to give rise to robustness following perturbations that disrupt breathing is less clear. During underwater hibernation, respiratory neurons of bullfrogs remain inactive for months, providing a large disturbance that must be overcome to restart breathing. As a result, motoneurons upregulate excitatory synapses to promote the drive to breathe. Reduced inhibition often occurs in parallel with increased excitation, yet the loss of inhibition can destabilize respiratory motor output. Thus, we hypothesized that GABAergic inhibition would decrease following hibernation, but this decrease would be expressed differentially throughout the network. We confirmed that respiratory frequency was under control of GABAAR signaling, but after hibernation, it became less reliant on inhibition. The loss of inhibition was confined to the respiratory rhythm-generating centers: non-respiratory motor activity and large seizure-like bursts were similarly triggered by GABAA receptor blockade in controls and hibernators. Supporting reduced presynaptic GABA release, firing rate of respiratory motoneurons was constrained by a phasic GABAAR tone, but after hibernation, this tone was decreased despite the same postsynaptic receptor strength as controls. Thus, selectively reducing inhibition in respiratory premotor networks promotes stability of breathing, while wholesale loss of GABAARs causes non-specific hyperexcitability throughout the brainstem. These results suggest that different parts of the respiratory network select distinct strategies involving either excitation (motoneurons) or inhibition (rhythm generator) to minimize pathological network states when engaging plasticity that protects the drive to breathe.
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Affiliation(s)
- Sandy E Saunders
- University of Missouri-Columbia, Missouri, United States of America
| | - Joseph M Santin
- University of Missouri-Columbia, Missouri, United States of America
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3
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Saunders SE, Santin JM. Activation of respiratory-related bursting in an isolated medullary section from adult bullfrogs. J Exp Biol 2023; 226:jeb245951. [PMID: 37665261 PMCID: PMC10546875 DOI: 10.1242/jeb.245951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 08/16/2023] [Indexed: 09/05/2023]
Abstract
Breathing is generated by a rhythmic neural circuit in the brainstem, which contains conserved elements across vertebrate groups. In adult frogs, the 'lung area' located in the reticularis parvocellularis is thought to represent the core rhythm generator for breathing. Although this region is necessary for breathing-related motor output, whether it functions as an endogenous oscillator when isolated from other brainstem centers is not clear. Therefore, we generated thick brainstem sections that encompass the lung area to determine whether it can generate breathing-related motor output in a highly reduced preparation. Brainstem sections did not produce activity. However, subsaturating block of glycine receptors reliably led to the emergence of rhythmic motor output that was further enhanced by blockade of GABAA receptors. Output occurred in singlets and multi-burst episodes resembling the intact network. However, burst frequency was slower and individual bursts had longer durations than those produced by the intact preparation. In addition, burst frequency was reduced by noradrenaline and μ-opioids, and increased by serotonin, as observed in the intact network and in vivo. These results suggest that the lung area can be activated to produce rhythmic respiratory-related motor output in a reduced brainstem section and provide new insights into respiratory rhythm generation in adult amphibians. First, clustering breaths into episodes can occur within the rhythm-generating network without long-range input from structures such as the pons. Second, local inhibition near, or within, the rhythmogenic center may need to be overridden to express the respiratory rhythm.
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Affiliation(s)
- Sandy E. Saunders
- Biological Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Joseph M. Santin
- Biological Sciences, University of Missouri, Columbia, MO 65211, USA
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Janes TA, Guay LM, Fournier S, Kinkead R. Persistent augmentation of fictive air breathing by hypoxia: An in vitro study of the role of GABA B signaling in pre-metamorphic tadpoles. Comp Biochem Physiol A Mol Integr Physiol 2023; 281:111437. [PMID: 37088410 DOI: 10.1016/j.cbpa.2023.111437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 04/14/2023] [Accepted: 04/18/2023] [Indexed: 04/25/2023]
Abstract
Tadpole development is influenced by environmental cues and hypoxia can favor the emergence of the neural networks driving air breathing. Exposing isolated brainstems from pre-metamorphic tadpoles to acute hypoxia (~0% O2; 15 min) leads to a progressive increase in fictive air breaths (~3 fold) in the hours that follow stimulation. Here, we first determined whether this effect persists over longer periods (<18 h); we then evaluated maturity of the motor output by comparing the breathing pattern of hypoxia-exposed brainstems to that of preparations from adult bullfrogs under basal conditions. Because progressive withdrawal of GABAB-mediated inhibition contributes to the developmental increase in fictive lung ventilation, we then hypothesised that hypoxia reduces respiratory sensitivity to baclofen (selective GABAB-agonist). Experiments were performed on isolated brainstem preparations from pre-metamorphic tadpoles (TK stages IV to XIV); respiratory-related neural activity was recorded from cranial nerves V/VII and X before and 18 h after exposure to hypoxia (0% O2 + 2% CO2; 25 min). Time-control experiments (no hypoxia) were performed. Exposing pre-metamorphic tadpoles to hypoxia did not affect gill burst frequency, but augmented the frequency of fictive lung bursts and the incidence of episodic breathing levels intermediate between pre-metamorphic and adult preparations. Addition of baclofen to the aCSF (0,2 μM - 20 min) reduced lung burst frequency, but the response of hypoxia-exposed brainstems was greater than controls. We conclude that acute hypoxia facilitates development and maturation of the motor command driving air breathing. We propose that a greater number of active rhythmogenic neurons expressing GABAb receptors contributes to this effect.
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Affiliation(s)
- Tara A Janes
- Department of Pediatrics, Université Laval & Research Center of the Québec Heart & Lung Institute, Québec, QC, Canada; Department of Physiology, Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada
| | - Loralie Mei Guay
- Department of Pediatrics, Université Laval & Research Center of the Québec Heart & Lung Institute, Québec, QC, Canada
| | - Stéphanie Fournier
- Department of Pediatrics, Université Laval & Research Center of the Québec Heart & Lung Institute, Québec, QC, Canada
| | - Richard Kinkead
- Department of Pediatrics, Université Laval & Research Center of the Québec Heart & Lung Institute, Québec, QC, Canada.
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Adams S, Zubov T, Bueschke N, Santin JM. Neuromodulation or energy failure? Metabolic limitations silence network output in the hypoxic amphibian brainstem. Am J Physiol Regul Integr Comp Physiol 2021; 320:R105-R116. [PMID: 33175586 PMCID: PMC7948128 DOI: 10.1152/ajpregu.00209.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/10/2020] [Accepted: 11/02/2020] [Indexed: 11/22/2022]
Abstract
Hypoxia tolerance in the vertebrate brain often involves chemical modulators that arrest neuronal activity to conserve energy. However, in intact networks, it can be difficult to determine whether hypoxia triggers modulators to stop activity in a protective manner or whether activity stops because rates of ATP synthesis are insufficient to support network function. Here, we assessed the extent to which neuromodulation or metabolic limitations arrest activity in the respiratory network of bullfrogs-a circuit that survives moderate periods of oxygen deprivation, presumably, by activating an inhibitory noradrenergic pathway. We confirmed that hypoxia and norepinephrine (NE) reduce network output, consistent with the view that hypoxia may cause the release of NE to inhibit activity. However, these responses differed qualitatively; hypoxia, but not NE, elicited a large motor burst and silenced the network. The stereotyped response to hypoxia persisted in the presence of both NE and an adrenergic receptor blocker that eliminates sensitivity to NE, indicating that noradrenergic signaling does not cause the arrest. Pharmacological inhibition of glycolysis and mitochondrial respiration recapitulated all features of hypoxia on network activity, implying that reduced ATP synthesis underlies the effects of hypoxia. Finally, activating modulatory mechanisms that dampen neuronal excitability when ATP levels fall, KATP channels and AMP-dependent protein kinase, did not resemble the hypoxic response. These results suggest that energy failure-rather than inhibitory modulation-silences the respiratory network during hypoxia and emphasize the need to account for metabolic limitations before concluding that modulators arrest activity as an adaptation for energy conservation in the nervous system.
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Affiliation(s)
- Sasha Adams
- Department of Biology, The University of North Carolina at Greensboro, Greensboro, North Carolina
| | - Tanya Zubov
- Department of Biology, The University of North Carolina at Greensboro, Greensboro, North Carolina
| | - Nikolaus Bueschke
- Department of Biology, The University of North Carolina at Greensboro, Greensboro, North Carolina
| | - Joseph M Santin
- Department of Biology, The University of North Carolina at Greensboro, Greensboro, North Carolina
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Is there a common drive for buccal movements associated with buccal and lung 'breath' in Lithobates catesbeianus? Respir Physiol Neurobiol 2020; 275:103382. [PMID: 31926342 DOI: 10.1016/j.resp.2020.103382] [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] [Received: 06/06/2019] [Revised: 12/09/2019] [Accepted: 01/06/2020] [Indexed: 11/20/2022]
Abstract
In amphibians, there is some evidence that (1) anatomically separate brainstem respiratory oscillators are involved in rhythm generation, one for the buccal rhythm and another for the lung rhythm and (2) they become functionally coupled during metamorphosis. The present analysis, performed on neurograms recorded using brainstem preparations from Lithobates catesbeianus, aims to investigate the temporal organisation of lung and buccal burst types. Continuous Wavelet Transfom applied to the separated buccal and lung signals of a neurogram revealed that both buccal and lung frequency profiles exhibited the same low frequency peak around 1 Hz. This suggests that a common 'clock' organises both rhythms within an animal. A cross-correlation analysis applied to the buccal and lung burst signals revealed their similar intrinsic oscillation features, occurring at approximately 25 Hz. These observations suggest that a coupling between the lung and buccal oscillators emerges at metamorphosis. This coupling may be related to inter-connectivity between the two oscillators, and to a putative common drive.
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Janes TA, Rousseau JP, Fournier S, Kiernan EA, Harris MB, Taylor BE, Kinkead R. Development of central respiratory control in anurans: The role of neurochemicals in the emergence of air-breathing and the hypoxic response. Respir Physiol Neurobiol 2019; 270:103266. [PMID: 31408738 PMCID: PMC7476778 DOI: 10.1016/j.resp.2019.103266] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/10/2019] [Accepted: 08/05/2019] [Indexed: 01/08/2023]
Abstract
Physiological and environmental factors impacting respiratory homeostasis vary throughout the course of an animal's lifespan from embryo to adult and can shape respiratory development. The developmental emergence of complex neural networks for aerial breathing dates back to ancestral vertebrates, and represents the most important process for respiratory development in extant taxa ranging from fish to mammals. While substantial progress has been made towards elucidating the anatomical and physiological underpinnings of functional respiratory control networks for air-breathing, much less is known about the mechanisms establishing these networks during early neurodevelopment. This is especially true of the complex neurochemical ensembles key to the development of air-breathing. One approach to this issue has been to utilize comparative models such as anuran amphibians, which offer a unique perspective into early neurodevelopment. Here, we review the developmental emergence of respiratory behaviours in anuran amphibians with emphasis on contributions of neurochemicals to this process and highlight opportunities for future research.
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Affiliation(s)
- Tara A Janes
- Department of Pediatrics, Université Laval & Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC, Canada
| | - Jean-Philippe Rousseau
- Department of Pediatrics, Université Laval & Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC, Canada
| | - Stéphanie Fournier
- Department of Pediatrics, Université Laval & Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC, Canada
| | - Elizabeth A Kiernan
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison Wisconsin, USA
| | - Michael B Harris
- Department of Biological Sciences, California State University Long Beach, California, USA
| | - Barbara E Taylor
- Department of Biological Sciences, California State University Long Beach, California, USA
| | - Richard Kinkead
- Department of Pediatrics, Université Laval & Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC, Canada.
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Reed MD, Iceman KE, Harris MB, Taylor BE. Buccal rhythmogenesis and CO 2 sensitivity in Lithobates catesbeianus tadpole brainstems across metamorphosis. Respir Physiol Neurobiol 2019; 268:103251. [PMID: 31279052 DOI: 10.1016/j.resp.2019.103251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 06/19/2019] [Accepted: 07/02/2019] [Indexed: 11/19/2022]
Abstract
Bullfrog tadpoles ventilate both the buccal cavity and lung. In isolated brainstems, the midbrain/pons influences CO2 responsiveness and timing of lung ventilatory bursting, depending on larval development. However, little is known about midbrain/pons influences on buccal burst patterns. As such, we investigated how removal of this region affects buccal burst shape and CO2 responsiveness across development. We measured facial nerve activity in brainstems isolated from tadpoles during early and late developmental stages, under normal and elevated levels of CO2. Brainstems were either left intact or transected by removing the midbrain/pons. In late stage preparations, buccal burst pattern differed between intact and reduced preparations, and bursts were responsive to elevated CO2 in these reduced preparations. These results suggest the midbrain/pons affects tadpole buccal burst pattern and CO2 responsiveness, perhaps similar to its influences on lung ventilation.
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Affiliation(s)
- Mitchell D Reed
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States.
| | - Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, Valparaiso University, Valparaiso, IN, 46383, United States
| | - Michael B Harris
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, California State University Long Beach, Long Beach, CA, 90840, United States
| | - Barbara E Taylor
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, California State University Long Beach, Long Beach, CA, 90840, United States
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Janes TA, Fournier S, Chamberland S, Funk GD, Kinkead R. Respiratory motoneuron properties during the transition from gill to lung breathing in the American bullfrog. Am J Physiol Regul Integr Comp Physiol 2019; 316:R281-R297. [PMID: 30601705 PMCID: PMC6459380 DOI: 10.1152/ajpregu.00303.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/24/2018] [Accepted: 12/30/2018] [Indexed: 12/23/2022]
Abstract
Amphibian respiratory development involves a dramatic metamorphic transition from gill to lung breathing and coordination of distinct motor outputs. To determine whether the emergence of adult respiratory motor patterns was associated with similarly dramatic changes in motoneuron (MN) properties, we characterized the intrinsic electrical properties of American bullfrog trigeminal MNs innervating respiratory muscles comprising the buccal pump. In premetamorphic tadpoles (TK stages IX-XVIII) and adult frogs, morphometric analyses and whole cell recordings were performed in trigeminal MNs identified by fluorescent retrograde labeling. Based on the amplitude of the depolarizing sag induced by hyperpolarizing voltage steps, two MN subtypes (I and II) were identified in tadpoles and adults. Compared with type II MNs, type I MNs had larger sag amplitudes (suggesting a larger hyperpolarization-activated inward current), greater input resistance, lower rheobase, hyperpolarized action potential threshold, steeper frequency-current relationships, and fast firing rates and received fewer excitatory postsynaptic currents. Postmetamorphosis, type I MNs exhibited similar sag, enhanced postinhibitory rebound, and increased action potential amplitude with a smaller-magnitude fast afterhyperpolarization. Compared with tadpoles, type II MNs from frogs received higher-frequency, larger-amplitude excitatory postsynaptic currents. Input resistance decreased and rheobase increased postmetamorphosis in all MNs, concurrent with increased soma area and hyperpolarized action potential threshold. We suggest that type I MNs are likely recruited in response to smaller, buccal-related synaptic inputs as well as larger lung-related inputs, whereas type II MNs are likely recruited in response to stronger synaptic inputs associated with larger buccal breaths, lung breaths, or nonrespiratory behaviors involving powerful muscle contractions.
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Affiliation(s)
- Tara A Janes
- Department of Pediatrics, Université Laval and Institut Universitaire de Cardiologie et de Pneumologie de Québec , Québec City, Québec , Canada
| | - Stéphanie Fournier
- Department of Pediatrics, Université Laval and Institut Universitaire de Cardiologie et de Pneumologie de Québec , Québec City, Québec , Canada
| | - Simon Chamberland
- Department of Neuroscience and Physiology and New York University Neuroscience Institute, New York University Langone Medical Center , New York, New York
| | - Gregory D Funk
- Department of Physiology, Neuroscience and Mental Health Institute, Women and Children's Health Research Institute, University of Alberta , Edmonton, Alberta , Canada
| | - Richard Kinkead
- Department of Pediatrics, Université Laval and Institut Universitaire de Cardiologie et de Pneumologie de Québec , Québec City, Québec , Canada
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Reed MD, Iceman KE, Harris MB, Taylor BE. The rostral medulla of bullfrog tadpoles contains critical lung rhythmogenic and chemosensitive regions across metamorphosis. Comp Biochem Physiol A Mol Integr Physiol 2018; 225:7-15. [PMID: 29890210 DOI: 10.1016/j.cbpa.2018.05.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 05/14/2018] [Accepted: 05/30/2018] [Indexed: 11/18/2022]
Abstract
The development of amphibian breathing provides insight into vertebrate respiratory control mechanisms. Neural oscillators in the rostral and caudal medulla drive ventilation in amphibians, and previous reports describe ventilatory oscillators and CO2 sensitive regions arise during different stages of amphibian metamorphosis. However, inconsistent findings have been enigmatic, and make comparisons to potential mammalian counterparts challenging. In the current study we assessed amphibian central CO2 responsiveness and respiratory rhythm generation during two different developmental stages. Whole-nerve recordings of respiratory burst activity in cranial and spinal nerves were made from intact or transected brainstems isolated from tadpoles during early or late stages of metamorphosis. Brainstems were transected at the level of the trigeminal nerve, removing rostral structures including the nucleus isthmi, midbrain, and locus coeruleus, or transected at the level of the glossopharyngeal nerve, removing the putative buccal oscillator and caudal medulla. Removal of caudal structures stimulated the frequency of lung ventilatory bursts and revealed a hypercapnic response in normally unresponsive preparations derived from early stage tadpoles. In preparations derived from late stage tadpoles, removal of rostral or caudal structures reduced lung burst frequency, while CO2 responsiveness was retained. Our results illustrate that structures within the rostral medulla are capable of sensing CO2 throughout metamorphic development. Similarly, the region controlling lung ventilation appears to be contained in the rostral medulla throughout metamorphosis. This work offers insight into the consistency of rhythmic respiratory and chemosensitive capacities during metamorphosis.
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Affiliation(s)
- Mitchell D Reed
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States.
| | - Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biology, Valparaiso University, Valparaiso, IN 46383, United States
| | - Michael B Harris
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States
| | - Barbara E Taylor
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States
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Garlet QI, Pires LDC, Milanesi LH, Marafiga JR, Baldisserotto B, Mello CF, Heinzmann BM. (+)-Dehydrofukinone modulates membrane potential and delays seizure onset by GABAa receptor-mediated mechanism in mice. Toxicol Appl Pharmacol 2017; 332:52-63. [PMID: 28733205 DOI: 10.1016/j.taap.2017.07.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/03/2017] [Accepted: 07/17/2017] [Indexed: 12/19/2022]
Abstract
(+)-Dehydrofukinone (DHF), isolated from Nectandra grandiflora (Lauraceae) essential oil, induces sedation and anesthesia by modulation of GABAa receptors. However, no study has addressed whether DHF modulates other cellular events involved in the control of cellular excitability, such as seizure behavior. Therefore, the aim of the present study was to investigate the effect of DHF on cellular excitability and seizure behavior in mice. For this purpose, we used isolated nerve terminals (synaptosomes) to examine the effect of DHF on the plasma membrane potential, the involvement of GABAa receptors and the downstream activation of Ca2+ mobilization. Finally, we performed an in vivo assay in order to verify whether DHF could impact on seizures induced by pentylenetetrazole (PTZ) in mice. The results showed that DHF induced a GABA-dependent sustained hyperpolarization, sensitive to flumazenil and absent in low-[Cl-] medium. Additionally, (1-100μM) DHF decreased KCl-evoked calcium mobilization over time in a concentration-dependent manner and this effect was prevented by flumazenil. DHF increased the latency to myoclonic jerks (10mg/kg), delayed the onset of generalized tonic-clonic seizures (10, 30 and 100mg/kg), and these effects were also blocked by the pretreatment with flumazenil. Our data indicate that DHF has anticonvulsant properties and the molecular target underlying this effect is likely to be the facilitation of GABAergic neuronal inhibition. The present study highlights the therapeutic potential of the natural compound DHF as a suppressor of neuronal excitability.
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Affiliation(s)
- Quelen Iane Garlet
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Luana da Costa Pires
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Laura Hautrive Milanesi
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Joseane Righes Marafiga
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Bernardo Baldisserotto
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Carlos Fernando Mello
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - Berta Maria Heinzmann
- Post-Graduation Program in Pharmacology, Federal University of Santa Maria, Santa Maria, RS, Brazil.
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Santin JM, Hartzler LK. Environmentally induced return to juvenile-like chemosensitivity in the respiratory control system of adult bullfrog, Lithobates catesbeianus. J Physiol 2016; 594:6349-6367. [PMID: 27444338 DOI: 10.1113/jp272777] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS The degree to which developmental programmes or environmental signals determine physiological phenotypes remains a major question in physiology. Vertebrates change environments during development, confounding interpretation of the degree to which development (i.e. permanent processes) or phenotypic plasticity (i.e. reversible processes) produces phenotypes. Tadpoles mainly breathe water for gas exchange and frogs may breathe water or air depending on their environment and are, therefore, exemplary models to differentiate the degree to which life-stage vs. environmental context drives developmental phenotypes associated with neural control of lung breathing. Using isolated brainstem preparations and patch clamp electrophysiology, we demonstrate that adult bullfrogs acclimatized to water-breathing conditions do not exhibit CO2 and O2 chemosensitivity of lung breathing, similar to water-breathing tadpoles. Our results establish that phenotypes associated with developmental stage may arise from plasticity per se and suggest that a developmental trajectory coinciding with environmental change obscures origins of stage-dependent physiological phenotypes by masking plasticity. ABSTRACT An unanswered question in developmental physiology is to what extent does the environment vs. a genetic programme produce phenotypes? Developing animals inhabit different environments and switch from one to another. Thus a developmental time course overlapping with environmental change confounds interpretations as to whether development (i.e. permanent processes) or phenotypic plasticity (i.e. reversible processes) generates phenotypes. Tadpoles of the American bullfrog, Lithobates catesbeianus, breathe water at early life-stages and minimally use lungs for gas exchange. As adults, bullfrogs rely on lungs for gas exchange, but spend months per year in ice-covered ponds without lung breathing. Aquatic submergence, therefore, removes environmental pressures requiring lung breathing and enables separation of adulthood from environmental factors associated with adulthood that necessitate control of lung ventilation. To test the hypothesis that postmetamorphic respiratory control phenotypes arise through permanent developmental changes vs. reversible environmental signals, we measured respiratory-related nerve discharge in isolated brainstem preparations and action potential firing from CO2 -sensitive neurons in bullfrogs acclimatized to semi-terrestrial (air-breathing) and aquatic-overwintering (no air-breathing) habitats. We found that aquatic overwintering significantly reduced neuroventilatory responses to CO2 and O2 involved in lung breathing. Strikingly, this gas sensitivity profile reflects that of water-breathing tadpoles. We further demonstrated that aquatic overwintering reduced CO2 -induced firing responses of chemosensitive neurons. In contrast, respiratory rhythm generating processes remained adult-like after submergence. Our results establish that phenotypes associated with life-stage can arise from phenotypic plasticity per se. This provides evidence that developmental time courses coinciding with environmental changes obscure interpretations regarding origins of stage-dependent physiological phenotypes by masking plasticity.
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Affiliation(s)
- Joseph M Santin
- Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45435, USA. .,Biomedical Sciences PhD Program, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45435, USA.
| | - Lynn K Hartzler
- Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45435, USA
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The neural control of respiration in lampreys. Respir Physiol Neurobiol 2016; 234:14-25. [PMID: 27562521 DOI: 10.1016/j.resp.2016.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 08/08/2016] [Accepted: 08/21/2016] [Indexed: 11/24/2022]
Abstract
This review focuses on past and recent findings that have contributed to characterize the neural networks controlling respiration in the lamprey, a basal vertebrate. As in other vertebrates, respiration in lampreys is generated centrally in the brainstem. It is characterized by the presence of a fast and a slow respiratory rhythm. The anatomical and the basic physiological properties of the neural networks underlying the generation of the fast rhythm have been more thoroughly investigated; less is known about the generation of the slow respiratory rhythm. Comparative aspects with respiratory generators in other vertebrates as well as the mechanisms of modulation of respiration in association with locomotion are discussed.
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14
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Ranohavimparany A, Bautin N, Fiamma MN, Similowski T, Straus C. Source of ventilatory complexity in the postmetamorphic tadpole brainstem, Pelophylax ridibundus: A pharmacological study. Respir Physiol Neurobiol 2016; 224:27-36. [DOI: 10.1016/j.resp.2014.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/22/2014] [Accepted: 11/06/2014] [Indexed: 10/24/2022]
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15
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Kovalecz G, Kecskes S, Birinyi A, Matesz C. Possible neural network mediating jaw opening during prey-catching behavior of the frog. Brain Res Bull 2015; 119:19-24. [PMID: 26444079 DOI: 10.1016/j.brainresbull.2015.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/10/2015] [Accepted: 09/29/2015] [Indexed: 12/01/2022]
Abstract
The prey-catching behavior of the frog is a complex, well-timed sequence of stimulus response chain of movements. After visual analysis of the prey, a size dependent program is selected in the motor pattern generator of the brainstem. Besides this predetermined feeding program, various direct and indirect sensory inputs provide flexible adjustment for the optimal contraction of the executive muscles. The aim of the present study was to investigate whether trigeminal primary afferents establish direct contacts with the jaw opening motoneurons innervated by the facial nerve. The experiments were carried out on Rana esculenta (Pelophylax esculentus), where the trigeminal and facial nerves were labeled simultaneously with different fluorescent dyes. Using a confocal laser scanning microscope, close appositions were detected between trigeminal afferent fibers and somatodendritic components of the facial motoneurons. Quantitative analysis revealed that the majority of close contacts were encountered on the dendrites of facial motoneurons and approximately 10% of them were located on the perikarya. We suggest that the identified contacts between the trigeminal afferents and facial motoneurons presented here may be one of the morphological substrate in the feedback and feedforward modulation of the rapidly changing activity of the jaw opening muscle during the prey-catching behavior.
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Affiliation(s)
- Gabriella Kovalecz
- Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary
| | - Szilvia Kecskes
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary
| | - András Birinyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary
| | - Clara Matesz
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary; MTA-DE Neuroscience Research Group, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary; Division of Oral Anatomy, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4032, Hungary.
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Johnson SM, Hedrick MS, Krause BM, Nilles JP, Chapman MA. Respiratory neuron characterization reveals intrinsic bursting properties in isolated adult turtle brainstems (Trachemys scripta). Respir Physiol Neurobiol 2014; 224:52-61. [PMID: 25462012 DOI: 10.1016/j.resp.2014.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 11/03/2014] [Accepted: 11/06/2014] [Indexed: 11/25/2022]
Abstract
It is not known whether respiratory neurons with intrinsic bursting properties exist within ectothermic vertebrate respiratory control systems. Thus, isolated adult turtle brainstems spontaneously producing respiratory motor output were used to identify and classify respiratory neurons based on their firing pattern relative to hypoglossal (XII) nerve activity. Most respiratory neurons (183/212) had peak activity during the expiratory phase, while inspiratory, post-inspiratory, and novel pre-expiratory neurons were less common. During synaptic blockade conditions, ∼10% of respiratory neurons fired bursts of action potentials, with post-inspiratory cells (6/9) having the highest percentage of intrinsic burst properties. Most intrinsically bursting respiratory neurons were clustered at the level of the vagus (X) nerve root. Synaptic inhibition blockade caused seizure-like activity throughout the turtle brainstem, which shows that the turtle respiratory control system is not transformed into a network driven by intrinsically bursting respiratory neurons. We hypothesize that intrinsically bursting respiratory neurons are evolutionarily conserved and represent a potential rhythmogenic mechanism contributing to respiration in adult turtles.
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Affiliation(s)
- Stephen M Johnson
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, United States.
| | - Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542, United States
| | - Bryan M Krause
- Neuroscience Training Program, University of Wisconsin, Madison, WI 53706, United States
| | - Jacob P Nilles
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, United States
| | - Mark A Chapman
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, United States
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Bongianni F, Mutolo D, Cinelli E, Pantaleo T. Neural mechanisms underlying respiratory rhythm generation in the lamprey. Respir Physiol Neurobiol 2014; 224:17-26. [PMID: 25220696 DOI: 10.1016/j.resp.2014.09.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 09/04/2014] [Accepted: 09/05/2014] [Indexed: 11/24/2022]
Abstract
The isolated brainstem of the adult lamprey spontaneously generates respiratory activity. The paratrigeminal respiratory group (pTRG), the proposed respiratory central pattern generator, has been anatomically and functionally characterized. It is sensitive to opioids, neurokinins and acetylcholine. Excitatory amino acids, but not GABA and glycine, play a crucial role in the respiratory rhythmogenesis. These results are corroborated by immunohistochemical data. While only GABA exerts an important modulatory control on the pTRG, both GABA and glycine markedly influence the respiratory frequency via neurons projecting from the vagal motoneuron region to the pTRG. Noticeably, the removal of GABAergic transmission within the pTRG causes the resumption of rhythmic activity during apnea induced by blockade of glutamatergic transmission. The same result is obtained by microinjections of substance P or nicotine into the pTRG during apnea. The results prompted us to present some considerations on the phylogenesis of respiratory pattern generation. They may also encourage comparative studies on the basic mechanisms underlying respiratory rhythmogenesis of vertebrates.
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Affiliation(s)
- Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy.
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
| | - Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
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18
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Côté É, Rousseau JP, Fournier S, Kinkead R. Control of Breathing in In Vitro Brain Stem Preparation from Goldfish (Carassius auratus; Linnaeus). Physiol Biochem Zool 2014; 87:464-74. [DOI: 10.1086/675939] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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19
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Cinelli E, Mutolo D, Robertson B, Grillner S, Contini M, Pantaleo T, Bongianni F. GABAergic and glycinergic inputs modulate rhythmogenic mechanisms in the lamprey respiratory network. J Physiol 2014; 592:1823-38. [PMID: 24492840 DOI: 10.1113/jphysiol.2013.268086] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have previously shown that GABA and glycine modulate respiratory activity in the in vitro brainstem preparations of the lamprey and that blockade of GABAA and glycine receptors restores the respiratory rhythm during apnoea caused by blockade of ionotropic glutamate receptors. However, the neural substrates involved in these effects are unknown. To address this issue, the role of GABAA, GABAB and glycine receptors within the paratrigeminal respiratory group (pTRG), the proposed respiratory central pattern generator, and the vagal motoneuron region was investigated both during apnoea induced by blockade of glutamatergic transmission and under basal conditions through microinjections of specific antagonists. The removal of GABAergic, but not glycinergic transmission within the pTRG, causes the resumption of rhythmic respiratory activity during apnoea, and reveals the presence of a modulatory control of the pTRG under basal conditions. A blockade of GABAA and glycine receptors within the vagal region strongly increases the respiratory frequency through disinhibition of neurons projecting to the pTRG from the vagal region. These neurons were retrogradely labelled (neurobiotin) from the pTRG. Intense GABA immunoreactivity is observed both within the pTRG and the vagal area, which corroborates present findings. The results confirm the pTRG as a primary site of respiratory rhythm generation, and suggest that inhibition modulates the activity of rhythm-generating neurons, without any direct role in burst formation and termination mechanisms.
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Affiliation(s)
- Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy.
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20
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Duchcherer M, Baghdadwala MI, Paramonov J, Wilson RJ. Localization of essential rhombomeres for respiratory rhythm generation in bullfrog tadpoles using a binary search algorithm: Rhombomere 7 is essential for the gill rhythm and suppresses lung bursts before metamorphosis. Dev Neurobiol 2013; 73:888-98. [DOI: 10.1002/dneu.22108] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 06/27/2013] [Accepted: 07/01/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Maryana Duchcherer
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology; University of Calgary; Calgary Alberta Canada T2N 4N1
| | - Mufaddal I. Baghdadwala
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology; University of Calgary; Calgary Alberta Canada T2N 4N1
| | - Jenny Paramonov
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology; University of Calgary; Calgary Alberta Canada T2N 4N1
| | - Richard J.A. Wilson
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology; University of Calgary; Calgary Alberta Canada T2N 4N1
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Kottick A, Baghdadwala MI, Ferguson EV, Wilson RJA. Transmission of the respiratory rhythm to trigeminal and hypoglossal motor neurons in the American Bullfrog (Lithobates catesbeiana). Respir Physiol Neurobiol 2013; 188:180-91. [PMID: 23791823 DOI: 10.1016/j.resp.2013.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 06/10/2013] [Accepted: 06/11/2013] [Indexed: 11/16/2022]
Abstract
Spatially distinct, interacting oscillators in the bullfrog medulla generate and coordinated buccal and lung ventilatory rhythms, but how these rhythms are transmitted onto trigeminal and hypoglossal motor neurons is unknown. Using a vertically-mounted isolated brainstem preparation, the Sheep Dip, we identified the regions of the brainstem containing motor nuclei using a solution capable of blocking synaptic release and, following washout, locally exposed these regions to 5 μM NBQX and/or 50 μM AP5. Local application of NBQX significantly reduced the amplitude of buccal and lung bursts on the trigeminal nerve, and lung bursts on the hypoglossal nerve. Local AP5 caused a significant reduction in lung burst amplitude on both nerves, but for buccal bursts, hypoglossal amplitude increased and trigeminal amplitude was unchanged. Local co-application of NBQX and AP5 eliminated fictive respiratory motor output completely in both nerves. These results are consistent with mammalian data, suggesting a critical role for glutamate in transmission of respiratory activity from oscillators to motor neurons.
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Affiliation(s)
- Andrew Kottick
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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22
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Emergent central pattern generator behavior in gap-junction-coupled Hodgkin-Huxley style neuron model. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2012; 2012:173910. [PMID: 23365558 PMCID: PMC3529455 DOI: 10.1155/2012/173910] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 10/23/2012] [Accepted: 10/30/2012] [Indexed: 01/09/2023]
Abstract
Most models of central pattern generators (CPGs) involve two distinct nuclei mutually inhibiting one another via synapses. Here, we present a single-nucleus model of biologically realistic Hodgkin-Huxley neurons with random gap junction coupling. Despite no explicit division of neurons into two groups, we observe a spontaneous division of neurons into two distinct firing groups. In addition, we also demonstrate this phenomenon in a simplified version of the model, highlighting the importance of afterhyperpolarization currents (I(AHP)) to CPGs utilizing gap junction coupling. The properties of these CPGs also appear sensitive to gap junction conductance, probability of gap junction coupling between cells, topology of gap junction coupling, and, to a lesser extent, input current into our simulated nucleus.
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Fournier S, Dubé PL, Kinkead R. Corticosterone promotes emergence of fictive air breathing in Xenopus laevis Daudin tadpole brainstems. J Exp Biol 2012; 215:1144-50. [DOI: 10.1242/jeb.061234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
The emergence of air breathing during amphibian metamorphosis requires significant changes to the brainstem circuits that generate and regulate breathing. However, the mechanisms controlling this developmental process are unknown. Because corticosterone plays an important role in the neuroendocrine regulation of amphibian metamorphosis, we tested the hypothesis that corticosterone augments fictive air breathing frequency in Xenopus laevis. To do so, we compared the fictive air breathing frequency produced by in vitro brainstem preparations from pre-metamorphic tadpoles and adult frogs before and after 1 h application of corticosterone (100 nmol l–1). Fictive breathing measurements related to gill and lung ventilation were recorded extracellularly from cranial nerve rootlets V and X. Corticosterone application had no immediate effect on respiratory-related motor output produced by brainstems from either developmental stage. One hour after corticosterone wash out, fictive lung ventilation frequency was increased whereas gill burst frequency was decreased. This effect was stage specific as it was significant only in preparations from tadpoles. GABA application (0.001–0.5 mmol l–1) augmented fictive air breathing in tadpole preparations. However, this effect of GABA was no longer observed following corticosterone treatment. An increase in circulating corticosterone is one of the endocrine processes that orchestrate central nervous system remodelling during metamorphosis. The age-specific effects of corticosterone application indicate that this hormone can act as an important regulator of respiratory control development in Xenopus tadpoles. Concurrent changes in GABAergic neurotransmission probably contribute to this maturation process, leading to the emergence of air breathing in this species.
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Affiliation(s)
- Stéphanie Fournier
- Department of Paediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Hôpital St-François d’Assise, 10 rue de l’Espinay, Québec City, QC, Canada, G1L 3L5
| | - Pierre-Luc Dubé
- Department of Paediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Hôpital St-François d’Assise, 10 rue de l’Espinay, Québec City, QC, Canada, G1L 3L5
| | - Richard Kinkead
- Department of Paediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Hôpital St-François d’Assise, 10 rue de l’Espinay, Québec City, QC, Canada, G1L 3L5
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Comparative transcriptomics and gene expression in larval tiger salamander (Ambystoma tigrinum) gill and lung tissues as revealed by pyrosequencing. Gene 2011; 492:329-38. [PMID: 22138480 DOI: 10.1016/j.gene.2011.11.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 10/21/2011] [Accepted: 11/10/2011] [Indexed: 01/15/2023]
Abstract
Biologists are beginning to unravel the complexities of gene expression in model organisms by studying the transcriptome, the complement of genes that are transcribed in a given tissue. It is unclear, however, if findings from model systems apply to non-model organisms because of environmental effects on gene expression. Furthermore, there have been few efforts to quantify how transcriptome or gene expression varies across individuals and across tissues in natural environments. Herein, we describe transcriptomic profiling of gene expression in lung and gill tissue of three larval tiger salamanders. We do so with a hierarchical experimental design that captures variation in expression among genes, among tissues, and among individuals. Using 454 pyrosequencing, we produced high-quality sequence data of 59 megabases and assembled ~200,000 reads into 19,501 contigs. These contigs BLASTed to 3,599 transcripts, of which 721 were expressed in both tissues, 1,668 were unique to gill, and 1,210 unique to lung. Our data showed tissue-specific patterns in gene expression level with variation among transcripts and individuals. We identified genes and gene ontology terms related to respiration and compared their relative expression levels between gill and lung tissues. We also found evidence of exogenous genes associated with larval salamanders, and we identified ~1400 potential molecular markers (microsatellites and single nucleotide polymorphisms) that are associated with expressed genes. Given the tissue-specific differences we observed in transcriptomes, these data reinforce the idea that changes in gene expression serve as a primary mechanism underlying phenotypic plasticity.
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25
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Straus C, Samara Z, Fiamma MN, Bautin N, Ranohavimparany A, Le Coz P, Golmard JL, Darré P, Zelter M, Poon CS, Similowski T. Effects of maturation and acidosis on the chaos-like complexity of the neural respiratory output in the isolated brainstem of the tadpole, Rana esculenta. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1163-74. [PMID: 21325645 PMCID: PMC3094042 DOI: 10.1152/ajpregu.00710.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 02/14/2011] [Indexed: 11/22/2022]
Abstract
Human ventilation at rest exhibits mathematical chaos-like complexity that can be described as long-term unpredictability mediated (in whole or in part) by some low-dimensional nonlinear deterministic process. Although various physiological and pathological situations can affect respiratory complexity, the underlying mechanisms remain incompletely elucidated. If such chaos-like complexity is an intrinsic property of central respiratory generators, it should appear or increase when these structures mature or are stimulated. To test this hypothesis, we employed the isolated tadpole brainstem model [Rana (Pelophylax) esculenta] and recorded the neural respiratory output (buccal and lung rhythms) of pre- (n = 8) and postmetamorphic tadpoles (n = 8), at physiologic (7.8) and acidic pH (7.4). We analyzed the root mean square of the cranial nerve V or VII neurograms. Development and acidosis had no effect on buccal period. Lung frequency increased with development (P < 0.0001). It also increased with acidosis, but in postmetamorphic tadpoles only (P < 0.05). The noise-titration technique evidenced low-dimensional nonlinearities in all the postmetamorphic brainstems, at both pH. Chaos-like complexity, assessed through the noise limit, increased from pH 7.8 to pH 7.4 (P < 0.01). In contrast, linear models best fitted the ventilatory rhythm in all but one of the premetamorphic preparations at pH 7.8 (P < 0.005 vs. postmetamorphic) and in four at pH 7.4 (not significant vs. postmetamorphic). Therefore, in a lower vertebrate model, the brainstem respiratory central rhythm generator accounts for ventilatory chaos-like complexity, especially in the postmetamorphic stage and at low pH. According to the ventilatory generators homology theory, this may also be the case in mammals.
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Affiliation(s)
- Christian Straus
- Service Central d'Explorations Fonctionnelles Respiratoires, Groupe Hospitalier Pitie-Salpetriere, 47-83 Boulevard de l'Hôpital, Paris Cedex 13, France
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26
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Brundage CM, Cartagena CM, Potter EA, Taylor BE. Nicotine elicits a developmentally dependent depression in bullfrog neuroventilatory response to CO2. Respir Physiol Neurobiol 2010; 170:226-35. [DOI: 10.1016/j.resp.2010.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 01/07/2010] [Accepted: 01/08/2010] [Indexed: 11/28/2022]
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Kinkead R. Phylogenetic trends in respiratory rhythmogenesis: Insights from ectothermic vertebrates. Respir Physiol Neurobiol 2009; 168:39-48. [DOI: 10.1016/j.resp.2009.05.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 05/27/2009] [Accepted: 05/28/2009] [Indexed: 11/26/2022]
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28
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Horcholle-Bossavit G, Quenet B. Neural model of frog ventilatory rhythmogenesis. Biosystems 2009; 97:35-43. [PMID: 19376192 DOI: 10.1016/j.biosystems.2009.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 04/09/2009] [Accepted: 04/09/2009] [Indexed: 10/20/2022]
Abstract
In the adult frog respiratory system, periods of rhythmic movements of the buccal floor are interspersed by lung ventilation episodes. The ventilatory activity results from the interaction of two hypothesized oscillators in the brainstem. Here, we model these oscillators with two coupled neural networks, whose co-activation results in the emergence of new dynamics. One of the networks is built with "loop chains" of excitatory and inhibitory neurones producing periodic activities. We define two groups of excitatory neurones whose oscillatory antiphasic sums of activities represent output signals as possible motor commands towards antagonist buccal muscles. The other oscillator is a small network with a self-modulated excitatory input to an excitatory neurone whose episodic firings synchronise some neurones of the first network chains. When this oscillator is silent, the output signals exhibit only regular oscillations, and, when active, the synchronisation process reconfigures the output signals whose new features are representative of lung ventilation motor patterns. The biological interest of this formal model is illustrated by the persistence of the relevant dynamical features when perturbations are introduced in the model, i.e. dynamic noises and architecture modifications. The implementation of the networks with clock-driven continuous time neurones provides simulations with physiological time scales.
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Gargaglioni LH, Bícegoa KC, Branco LGS. Brain monoaminergic neurons and ventilatory control in vertebrates. Respir Physiol Neurobiol 2009; 164:112-22. [PMID: 18550453 DOI: 10.1016/j.resp.2008.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2008] [Revised: 04/15/2008] [Accepted: 04/23/2008] [Indexed: 10/22/2022]
Abstract
Monoamines (noradrenaline (NA), adrenaline (AD), dopamine (DA) and serotonin (5-HT) are key neurotransmitters that are implicated in multiple physiological and pathological brain mechanisms, including control of respiration. The monoaminergic system is known to be widely distributed in the animal kingdom, which indicates a considerable degree of phylogenetic conservation of this system amongst vertebrates. Substantial progress has been made in uncovering the participation of the brain monoamines in the breathing regulation of mammals, since they are involved in the maturation of the respiratory network as well as in the modulation of its intrinsic and synaptic properties. On the other hand, for the non-mammalian vertebrates, most of the knowledge of central monoaminergic modulation in respiratory control, which is actually very little, has emerged from studies using anuran amphibians. This article reviews the available data on the role of brain monoaminergic systems in the control of ventilation in terrestrial vertebrates. Emphasis is given to the comparative aspects of the brain noradrenergic, adrenergic, dopaminergic and serotonergic neuronal groups in breathing regulation, after first briefly considering the distribution of monoaminergic neurons in the vertebrate brain.
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Affiliation(s)
- Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, State University of Sao Paulo, FCAV at Jaboticabal, SP, Brazil.
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Chen AK, Hedrick MS. Role of glutamate and substance P in the amphibian respiratory network during development. Respir Physiol Neurobiol 2008; 162:24-31. [PMID: 18450524 PMCID: PMC2504693 DOI: 10.1016/j.resp.2008.03.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 03/18/2008] [Accepted: 03/24/2008] [Indexed: 01/08/2023]
Abstract
This study tested the hypothesis that glutamatergic ionotropic (AMPA/kainate) receptors and neurokinin receptors (NKR) are important in the regulation of respiratory motor output during development in the bullfrog. The roles of these receptors were studied with in vitro brainstem preparations from pre-metamorphic tadpoles and post-metamorphic frogs. Brainstems were superfused with an artificial cerebrospinal fluid at 20-22 degrees C containing CNQX, a selective non-NMDA antagonist, or with substance P (SP), an agonist of NKR. Blockade of glutamate receptors with CNQX in both groups caused a reduction of lung burst frequency that was reversibly abolished at 5 microM (P<0.01). CNQX, but not SP, application produced a significant increase (P<0.05) in gill and buccal frequency in tadpoles and frogs, respectively. SP caused a significant increase (P<0.05) in lung burst frequency at 5 microM in both groups. These results suggest that glutamatergic activation of AMPA/kainate receptors is necessary for generation of lung burst activity and that SP is an excitatory neurotransmitter for lung burst frequency generation. Both glutamate and SP provide excitatory input for lung burst generation throughout the aquatic to terrestrial developmental transition in bullfrogs.
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Affiliation(s)
- Anna K. Chen
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542 USA
| | - Michael S. Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542 USA
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Fournier S, Kinkead R. Role of pontine neurons in central O(2) chemoreflex during development in bullfrogs (Lithobates catesbeiana). Neuroscience 2008; 155:983-96. [PMID: 18590803 DOI: 10.1016/j.neuroscience.2008.05.044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 05/20/2008] [Accepted: 05/26/2008] [Indexed: 11/25/2022]
Abstract
The present study used an in vitro brainstem preparation from pre-metamorphic tadpoles and adult bullfrogs (Lithobates catesbeiana) to understand the neural mechanisms associated with central O(2) chemosensitivity and its maturation. In this species, brainstem hypoxia increases fictive lung ventilation in tadpoles but decreases in adults. Previous studies have shown that alpha(1)-adrenoceptor inactivation prevents these responses, suggesting that noradrenergic neurons are involved. We first tested the hypothesis that the pons (which includes noradrenergic neurons from the locus coeruleus; LC) plays a role in the lung burst frequency response to central hypoxia by comparing the effects of brainstem transection at the LC level between pre-metamorphic tadpoles and adults. Data show that brainstem transection prevents the lung burst frequency response in both stage groups. During development, the progressive decrease in the Na(+)/K(+)/Cl(-) co-transporter NKCC1 contributes to the maturation of neural networks. Because NKCC1 becomes activated during hypoxia, we then tested the hypothesis that NKCC1 contributes to maturation of the central O(2) chemoreflex. Double labeling experiments showed that the proportion of tyrosine hydroxylase positive neurons expressing NKCC1 in the LC decreases during development. Inactivation of NKCC1 with bumetanide bath application reversed the lung burst response to hypoxia in tadpoles. Bumetanide inhibited the response in adults. These data indicate that a structure within the pons (potentially the LC) is necessary to the central hypoxic chemoreflex and demonstrate that NKCC1 plays a role in central O(2) chemosensitivity and its maturation in this species.
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Affiliation(s)
- S Fournier
- Department of Pediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, QC, Canada
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Oku Y, Kimura N, Masumiya H, Okada Y. Spatiotemporal organization of frog respiratory neurons visualized on the ventral medullary surface. Respir Physiol Neurobiol 2008; 161:281-90. [PMID: 18448395 DOI: 10.1016/j.resp.2008.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 03/05/2008] [Accepted: 03/06/2008] [Indexed: 10/22/2022]
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Fournier S, Allard M, Roussin S, Kinkead R. Developmental changes in central O2 chemoreflex in Rana catesbeiana: the role of noradrenergic modulation. ACTA ACUST UNITED AC 2007; 210:3015-26. [PMID: 17704076 DOI: 10.1242/jeb.005983] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The in vitro brainstem preparation from Rana catesbeiana shows a functional central O(2) chemoreflex. Acute brainstem exposure to hypoxic superfusate elicits lung burst frequency responses that change over the course of development. Based on studies suggesting that brainstem noradrenergic neurons are involved in this reflex, we tested the following two hypotheses in vitro: (1) activation of adrenoceptors is necessary for the expression of the fictive lung ventilation response to hypoxia, and (2) changes in fast, Cl(-)-dependent neurotransmission (GABA/glycine) contribute to developmental changes in noradrenergic modulation. Experiments were performed on preparations from pre-metamorphics tadpoles (TK stages V-XIII) and adult bullfrogs. Acute exposure to hypoxic superfusate (98% N(2), 2% CO(2)) increased fictive lung ventilation frequency in the pre-metamorphic group, whereas a decrease was observed in adults. Buccal burst frequency was unchanged by hypoxia. Noradrenaline (NA; 5 micromol l(-1)) bath application mimicked both fictive breathing responses and application of the alpha(1)-antagonist prazosine (0.5 micromol l(-1)) blocked the lung burst response to hypoxia in both groups. Blocking GABA(A)/glycine receptors with a bicuculine/strychnine mixture (1.25 micromol l(-1)/1.5 micromol l(-1), respectively) or activation of GABA(B) pre-synaptic autoreceptors with baclofen (0.5 micromol l(-1)) prevented the lung burst response to hypoxia and to the alpha(1)-agonist phenylephrine (25 micromol l(-1)) in both stage groups. We conclude that NA modulation contributes to the central O(2) chemoreflex in bullfrog, which acts via GABA/glycine pathways. These data suggest that maturation of GABA/glycine neurotransmission contributes to the developmental changes in this chemoreflex.
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Affiliation(s)
- Stéphanie Fournier
- Department of Pediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, QC, Canada
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Belzile O, Gulemetova R, Kinkead R. Effects of medullary Raphé stimulation on fictive lung ventilation during development in Rana catesbeiana. J Exp Biol 2007; 210:2046-56. [PMID: 17562878 DOI: 10.1242/jeb.003202] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
To better understand serotonergic modulation of air breathing during bullfrog development, we measured changes in fictive lung ventilation frequency associated with focal stimulation of the rostral region of the medullary Raphé neurons. Electrical (3 to 33 Hz) and chemical(glutamate microinjections; 0.5 mol l–1, 0.3–10 nl)activation of Raphé neurons was performed in brainstem preparations from three developmental stages (pre- and metamorphic tadpoles and adult frogs). Fictive lung ventilation was recorded extracelluarly from the Vth and Xth cranial nerves. Electrical stimulation of Raphé neurons caused a frequency-dependent increase in lung burst frequency in pre-metamorphic tadpoles only. In metamorphic tadpoles, an increase in fictive lung ventilation was observed at 20 Hz only. Electrical stimulation had no effect in preparations from adult frogs. Glutamate microinjections elicited similar responses as a lung burst frequency increase was observed in the pre-metamorphic group only. Regardless of the stimulation technique used, the increase in fictive lung ventilation was attenuated by the selective 5-HT3 antagonist tropisetron (5–20 μmol l–1). Results from immunohistochemical analysis of the Raphé region stimulated do not correlate with functional data as the number of 5-HT immunoreactive neurons within this region increases during development. We conclude that, in this preparation, stimulation of lung ventilation by the medullary Raphé is restricted to early(pre-metamorphic) stages.
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Affiliation(s)
- Olivier Belzile
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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Cano-Martínez A, Vargas-González A, Guarner-Lans V. Temperature effect on contractile activity of the Ambystoma dumerilii heart previously treated with isoproterenol. Comp Biochem Physiol A Mol Integr Physiol 2006; 147:743-749. [PMID: 17196415 DOI: 10.1016/j.cbpa.2006.10.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 10/20/2006] [Accepted: 10/22/2006] [Indexed: 10/24/2022]
Abstract
The spontaneous heart rate (HR) and ventricular (V) and atrium (A) tensions (T) were evaluated through isolated organ assays at different temperatures in hearts from Ambystoma dumerilii control and treated with isoproterenol (ISO) [(150 mg/kg i.p. each 24 h, for 3 days)] on days 1, 5, 30 and 90 after ISO. In control hearts, the HR increased and the T decreased when temperature was augmented. One day after ISO the HR (43-24%) and T (50-25%) decreased with respect to control, between 8 and 24 degrees C. Five, 30 and 90 days after ISO, HR showed a gradual recovery with similar effect when the temperature was changed; but the AT increased and VT decreased at temperatures between 8 and 12 degrees C and were only recovered at temperatures above 12 degrees C. Our results indicate that the HR recovers after ISO in A. dumerilii independently of temperature. The recovery of AT and VT is similar to HR at temperatures higher than 12 degrees C and the increases in VT could be compensating the decrease in VT caused by ISO, at temperatures lower than 12 degrees C. The changes in heart contractile activity of A. dumerilii after insult show the thermic plasticity that is observed in ectothermic vertebrates.
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Affiliation(s)
- A Cano-Martínez
- Departamento de Fisiología, Instituto Nacional de Cardiología "Ignacio Chávez", Juan Badiano # 1, Colonia Sección XVI, Tlalpan, México D.F. 14080, Mexico.
| | - A Vargas-González
- Departamento de Fisiología, Instituto Nacional de Cardiología "Ignacio Chávez", Juan Badiano # 1, Colonia Sección XVI, Tlalpan, México D.F. 14080, Mexico
| | - V Guarner-Lans
- Departamento de Fisiología, Instituto Nacional de Cardiología "Ignacio Chávez", Juan Badiano # 1, Colonia Sección XVI, Tlalpan, México D.F. 14080, Mexico
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Gargaglioni LH, Milsom WK. Control of breathing in anuran amphibians. Comp Biochem Physiol A Mol Integr Physiol 2006; 147:665-684. [PMID: 16949847 DOI: 10.1016/j.cbpa.2006.06.040] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 06/21/2006] [Accepted: 06/24/2006] [Indexed: 11/27/2022]
Abstract
The primary role of the respiratory system is to ensure adequate tissue oxygenation, eliminate carbon dioxide and help to regulate acid-base status. To maintain this homeostasis, amphibians possess an array of receptors located at peripheral and central chemoreceptive sites that sense respiration-related variables in both internal and external environments. As in mammals, input from these receptors is integrated at central rhythmogenic and pattern-forming elements in the medulla in a manner that meets the demands determined by the environment within the constraints of the behavior and breathing pattern of the animal. Also as in mammals, while outputs from areas in the midbrain may modulate respiration directly, they do not play a significant role in the production of the normal respiratory rhythm. However, despite these similarities, the breathing patterns of the two classes are different: mammals maintain homeostasis of arterial blood gases through rhythmic and continuous breathing, whereas amphibians display an intermittent pattern of aerial respiration. While the latter is also often rhythmic, it allows a degree of fluctuation in key respiratory variables that has led some to suggest that control is not as tight in these animals. In this review we will focus specifically on recent advances in studies of the control of ventilation in anuran amphibians. This is the group of amphibians that has attracted the most recent attention from respiratory physiologists.
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Affiliation(s)
- Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, Sao Paulo State University-FCAV at Jaboticabal, SP, Brazil.
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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Wilson RJA, Vasilakos K, Remmers JE. Phylogeny of vertebrate respiratory rhythm generators: the Oscillator Homology Hypothesis. Respir Physiol Neurobiol 2006; 154:47-60. [PMID: 16750658 DOI: 10.1016/j.resp.2006.04.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Revised: 04/11/2006] [Accepted: 04/11/2006] [Indexed: 11/30/2022]
Abstract
A revolution is underway in our understanding of respiratory rhythm generation in mammals. Until recently, a major focus of research within the field has centered around the question of locating and elucidating the mechanism of rhythmogenesis of a single respiratory neuronal oscillator which is reiterated bilaterally within the brainstem. Now it appears that each hemisection may contain at least two oscillators that interact to generate the respiratory rhythm in mammals. Comparative studies have hinted at the existence of multiple respiratory oscillators in non-mammalian vertebrates for some time, raising the possibility of homologous oscillators. Here, we consider available tools to identify neuronal oscillators and critically review the evidence for the importance and existence of multiple respiratory oscillators in vertebrates. First focusing on a comparison between frogs and mammals, we then evaluate the hypothesis that ventilatory oscillators in extant tetrapods evolved from ancestral oscillators present in fish (the Oscillator Homology Hypothesis). While supporting data are incomplete, the Oscillator Homology Hypothesis will likely serve as a useful framework to motivate further studies of respiratory rhythm generation in lower vertebrates.
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Affiliation(s)
- Richard J A Wilson
- Department of Physiology and Biophysics, University of Calgary, Calgary, Alta., Canada.
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Gdovin MJ, Jackson VV, Zamora DA, Leiter JC. Effect of prevention of lung inflation on metamorphosis and respiration in the developing bullfrog tadpole, Rana catesbeiana. ACTA ACUST UNITED AC 2006; 305:335-47. [PMID: 16493648 DOI: 10.1002/jez.a.266] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We tested the hypothesis that respiratory development would be retarded in tadpoles reared in aquaria in which a barrier prevented access to the air-water interface. To test this hypothesis, we examined swimming behavior and respiration in intact tadpoles and gill and lung respiratory activity and central chemosensory responses in an in vitro brainstem preparation. The "barrier" tadpoles had significantly lower resting gill frequencies and higher lung breath attempts than control tadpoles at the same metamorphic stage. Control tadpoles swam greater distances and spent more time in the upper one third of the aquaria, while barrier tadpoles spent significantly more time at the bottom of the aquaria. There was significantly greater mortality for barrier tadpoles compared to control animals in the earliest and latest metamorphic stages. Mean body weight was significantly greater, and metamorphic rate was reduced in barrier tadpoles. Neither control nor barrier tadpole brainstem preparations demonstrated a gill ventilatory response to CO(2); however, both control and barrier preparations possessed significant lung frequency responses to central CO(2) chemoreceptor stimulation. Bath application of the GABA(A) and glycine receptor antagonists, bicuculline and strychnine, had greater effects on control tadpole gill burst activity and produced a similar large-amplitude bursting pattern in both control and barrier tadpoles, that was insensitive to CO(2) chemoreceptor stimulation. We conclude that development of the respiratory pattern was perturbed by the barrier, but the major effect was on gill ventilation rather than lung ventilation as we had expected.
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Affiliation(s)
- Matthew J Gdovin
- Department of Biology, University of Texas at San Antonio, 6900 North Loop 1604 West, San Antonio, Texas 78249, USA.
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39
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Hedrick MS. Development of respiratory rhythm generation in ectothermic vertebrates. Respir Physiol Neurobiol 2005; 149:29-41. [PMID: 15914099 DOI: 10.1016/j.resp.2005.03.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 03/17/2005] [Accepted: 03/18/2005] [Indexed: 11/30/2022]
Abstract
Compared with birds and mammals, very little is known about the development and regulation of respiratory rhythm generation in ectothermic vertebrates. The development and regulation of respiratory rhythm generation in ectothermic vertebrates (fish, amphibians and reptiles) should provide insight into the evolution of these mechanisms. One useful model for examining the development of respiratory rhythm generation in ectothermic vertebrates has emerged from studies with the North American bullfrog (Rana catesbeiana). A major advantage of bullfrogs as a comparative model for respiratory rhythm generation is that respiratory output may be measured at all stages of development, both in vivo and in vitro. An emerging view of recent studies in developing bullfrogs is that many of the mechanisms of respiratory rhythm generation are very similar to those seen in birds and mammals. The overall conclusion from these studies is that respiratory rhythm generation during development may be highly conserved during evolution. The development of respiratory rhythm generation in mammals may, therefore, reflect the antecedent mechanisms seen in ectothermic vertebrates. The main focus of this brief review is to discuss recent data on the development of respiratory rhythm generation in ectothermic vertebrates, with particular emphasis on the North American bullfrog (R. catesbeiana) as a model.
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Affiliation(s)
- Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542, USA.
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Hedrick MS, Chen AK, Jessop KL. Nitric oxide changes its role as a modulator of respiratory motor activity during development in the bullfrog (Rana catesbeiana). Comp Biochem Physiol A Mol Integr Physiol 2005; 142:231-40. [PMID: 16023875 DOI: 10.1016/j.cbpb.2005.06.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2005] [Revised: 06/10/2005] [Accepted: 06/12/2005] [Indexed: 10/25/2022]
Abstract
Nitric oxide (NO) is a unique chemical messenger that has been shown to play a role in the modulation of breathing in amphibians and other vertebrates. In the post-metamorphic tadpole and adult amphibian brainstem, NO, acting via the neuronal isoform of nitric oxide synthase (nNOS), is excitatory to the generation of lung burst activity. In this study, we examine the modulation of breathing by NO during development of the amphibian brainstem. Isolated brainstem preparations from pre-metamorphic and late-stage post-metamorphic tadpoles (Rana catesbeiana) were used to determine the role of NO in modulating central respiratory neural activity. Respiratory neural activity was monitored with suction electrodes recording extracellular activity of cranial nerve rootlets that innervate respiratory musculature. Brainstems were superfused with an artificial cerebrospinal fluid (aCSF) at 20-22 degrees C containing l-nitroarginine (l-NA; 1-10 mM), a non-selective NOS inhibitor. In pre-metamorphic tadpoles, l-NA increased fictive gill ventilation frequency and amplitude, and increased lung burst frequency. By contrast, l-NA applied to the post-metamorphic tadpole brainstem had little effect on fictive buccal activity, but significantly decreased lung burst frequency and the frequency of lung burst episodes. These data indicate that early in development, NO provides a tonic inhibitory input to gill and lung burst activity, but as development progresses, NO provides an excitatory input to lung ventilation. This changing role for NO coincides with the shift in importance in the different respiratory modes during development in amphibians; that is, pre-metamorphic tadpoles rely predominantly on gill ventilation whereas post-metamorphic tadpoles have lost the gills and are obligate air-breathers primarily using lungs for gas exchange. We hypothesize that NO provides a tonic input to the respiratory CPG during development and this changing role reflects the modulatory influence of NO on inhibitory or excitatory modulators or neurotransmitters involved in the generation of respiratory rhythm.
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Affiliation(s)
- Michael S Hedrick
- Department of Biological Sciences, California State University, East Bay, Hayward, CA 94542 USA.
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Vasilakos K, Wilson RJA, Kimura N, Remmers JE. Ancient gill and lung oscillators may generate the respiratory rhythm of frogs and rats. ACTA ACUST UNITED AC 2005; 62:369-85. [PMID: 15551345 DOI: 10.1002/neu.20102] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Though the mechanics of breathing differ fundamentally between amniotes and "lower" vertebrates, homologous rhythm generators may drive air breathing in all lunged vertebrates. In both frogs and rats, two coupled oscillators, one active during the inspiratory (I) phase and the other active during the preinspiratory (PreI) phase, have been hypothesized to generate the respiratory rhythm. We used opioids to uncouple these oscillators. In the intact rat, complete arrest of the external rhythm by opioid-induced suppression of the putative I oscillator, that is, pre-Bötzinger complex (PBC) oscillator, did not arrest the putative PreI oscillator. In the unanesthetized frog, the comparable PreI oscillator, that is, the putative buccal/gill oscillator, was refractory to opioids even though the comparable I oscillator, the putative lung oscillator, was arrested. Studies in en bloc brainstem preparations derived from both juvenile frogs and metamorphic tadpoles confirmed these results and suggested that opioids may play a role in the clustering of lung bursts into episodes. As the frog and rat respiratory circuitry produce functionally equivalent motor outputs during lung inflation, these data argue for a close homology between the frog and rat oscillators. We suggest that the respiratory rhythm of all lunged vertebrates is generated by paired coupled oscillators. These may have originated from the gill and lung oscillators of the earliest air breathers.
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Affiliation(s)
- Konstantinon Vasilakos
- Department of Medicine, University of Calgary, 3330 Hospital Drive, Calgary, Alberta, Canada T2N 4N1
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Winmill RE, Chen AK, Hedrick MS. Development of the respiratory response to hypoxia in the isolated brainstem of the bullfrog Rana catesbeiana. ACTA ACUST UNITED AC 2005; 208:213-22. [PMID: 15634841 DOI: 10.1242/jeb.01399] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The aim of this study was to examine the effects of cellular hypoxia, and the contribution of anaerobic metabolism, on respiratory activity in bullfrogs at different stages of development. Respiratory-related neural activity was recorded from cranial nerve rootlets in isolated brainstem preparations from pre-metamorphic (Taylor-Kollros (T-K) stages VIII-XVI) and postmetamorphic tadpoles (T-K stages XXIV-XXV) and adults. Changes in fictive gill/lung activity in brainstems from pre-metamorphic tadpoles and lung activity in postmetamorphic tadpoles and adults were examined during superfusion with control (98% O(2)/2% CO(2)) or hypoxic (98% N(2)/2% CO(2)) artificial cerebrospinal fluid (aCSF). Iodoacetate (IAA; 100 micromol l(-1)) was used in conjunction with hypoxic aCSF to inhibit glycolysis. Gill burst frequency in pre-metamorphic brainstems did not change over a 3 h exposure to hypoxia and fictive lung burst frequency slowed significantly, but only after 3 h hypoxia. Blockade of glycolysis with IAA during hypoxia significantly reduced the time respiratory activity could be maintained in pre-metamorphic, but not in adult, brainstems. In brainstems from post-metamorphic tadpoles and adults, lung burst frequency became significantly more episodic within 5-15 min hypoxic exposure, but respiratory neural activity was subsequently abolished in every preparation. The cessation of fictive breathing was restored to control levels upon reoxygenation. Neither tadpole nor adult brainstems exhibited changes in neural bursts resembling 'gasping' that is observed in mammalian brainstems exposed to severe hypoxia. There was also a significant increase in the frequency of 'non-respiratory' bursts in hypoxic postmetamorphic and adult brainstems, but not in pre-metamorphic brainstems. These results indicate that pre-metamorphic tadpoles are capable of maintaining respiratory activity for 3 h or more during severe hypoxia and rely to a great extent upon anaerobic metabolism to maintain respiratory motor output. Upon metamorphosis, however, hypoxia results in significant changes in respiratory frequency and pattern, including increased lung burst episodes, non-ventilatory bursts and a reversible cessation of respiratory activity. Adults have little or no ability to maintain respiratory activity through glycolysis but, instead, stop respiratory activity until oxygen is available. This 'switch' in the respiratory response to hypoxia coincides morphologically with the loss of gills and obligate air-breathing in the postmetamorphic frog. We hypothesize that the cessation of respiratory activity in post-metamorphic tadpoles and adults is an adaptive, energy-saving response to low oxygen.
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Affiliation(s)
- Rachel E Winmill
- Department of Biological Sciences, California State University, Hayward, Hayward, CA 94542, USA
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Abstract
Comparative developmental physiology spans genomics to physiological ecology and evolution. Although not a new discipline, comparative developmental physiology's position at the convergence of development, physiology and evolution gives it prominent new significance. The contributions of this discipline may be particularly influential as physiologists expand beyond genomics to a true systems synthesis, integrating molecular through organ function in multiple organ systems. This review considers how developing physiological systems are directed by genes yet respond to environment and how these characteristics both constrain and enable evolution of physiological characters. Experimental approaches and methodologies of comparative developmental physiology include studying event sequences (heterochrony and heterokairy), describing the onset and progression of physiological regulation, exploiting scaling, expanding the list of animal models, using genetic engineering, and capitalizing on new miniaturized technologies for physiological investigation down to the embryonic level. A synthesis of these approaches is likely to generate a more complete understanding of how physiological systems and, indeed, whole animals develop and how populations evolve.
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Affiliation(s)
- Warren Burggren
- Department of Biological Sciences, University of North Texas, Denton, Texas 76203, USA.
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Belzile O, Simard E, Gulemetova R, Bairam A, Kinkead R. Un modèle amphibian pour l’étude du développement du contrôle de la respiration. Med Sci (Paris) 2004; 20:904-8. [PMID: 15461969 DOI: 10.1051/medsci/20042010904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Recent medical advances have made it possible for babies to survive premature birth at increasingly earlier developmental stages. This population requires costly and sophisticated medical care to address the problems associated with immaturity of the respiratory system. In addition to pulmonary complications, respiratory instability and apnea reflecting immaturity of the respiratory control system are major causes of hospitalization and morbidity in this highly vulnerable population. These medical concerns, combined with the curiosity of physiologists, have contributed to the expansion of research in respiratory neurobiology. While most researchers working in this field commonly use rodents as an animal model, recent research using in vitro brainstem preparation from bullfrogs (Rana catesbeiana) have revealed the technical advantages of this animal model, and shown that the basic principles underlying respiratory control and its ontogeny are very similar between these two groups of vertebrates. The present review highlights the recent advances in the area of research with a focus on intermittent (episodic) breathing and the role of serotonergic and GABAergic modulation of respiratory activity during development.
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Affiliation(s)
- Olivier Belzile
- Département de Pédiatrie, Université Laval, Centre de recherche, Hôpital Saint-François d'Assise, 10, rue de l'Espinay, Québec, G1L 3L5 Canada
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Winmill RE, Hedrick MS. Gap junction blockade with carbenoxolone differentially affects fictive breathing in larval and adult bullfrogs. Respir Physiol Neurobiol 2003; 138:239-51. [PMID: 14609513 DOI: 10.1016/j.resp.2003.08.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study examined the role of gap junctional communication in the modulation of respiratory related motor output using in vitro brainstem preparations of larval (N=14) and adult (N=14) bullfrogs (Rana catesbeiana). Superfusion of the isolated brainstem for at least 1 h with the gap junction blocker carbenoxolone (CBX; 100 microM and 1 mM) dissolved in artificial cerebrospinal fluid (aCSF) elicited significant changes in respiratory-related burst frequency in both larval and adult preparations. In tadpole preparations, both concentrations of CBX significantly decreased gill and lung burst frequency over 20-40 min, with 1 mM CBX producing complete cessation of gill and lung burst activity by 40 min in all preparations. There was little or no change in other burst characteristics such as burst amplitude or duration. By contrast, superfusion of the adult brainstem preparation with CBX significantly increased lung burst frequency over 10-20 min, and caused cessation of lung burst activity with 100 microM CBX (five of seven preparations) and with 1 mM CBX (seven of seven preparations). Adult preparations that ceased activity with 100 microM CBX recovered in control aCSF, but those in 1 mM did not recover, despite up to 3 h superfusion with control aCSF. In two additional adult preparations, 1 h exposure to hypercapnic aCSF (7-10% CO2) following the cessation of fictive breathing with 1 mM CBX failed to evoke respiratory activity. The inhibition of fictive breathing in tadpoles suggests that gap junctional communication may be important for respiratory rhythmogenesis prior to the development of central CO2 chemosensitivity. Following metamorphosis to the terrestrial adult, however, gap junctional communication may contribute to regulation of respiratory frequency and possibly the transduction of central CO2 chemosensitivity.
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Affiliation(s)
- Rachel E Winmill
- Department of Biological Sciences, California State University, Hayward, Hayward, CA 94542, USA
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46
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Winmill RE, Hedrick MS. Developmental changes in the modulation of respiratory rhythm generation by extracellular K+ in the isolated bullfrog brainstem. JOURNAL OF NEUROBIOLOGY 2003; 55:278-87. [PMID: 12717698 DOI: 10.1002/neu.10212] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study tested the hypothesis that voltage-dependent, respiratory-related activity in vitro, inferred from changes in [K(+)](o), changes during development in the amphibian brainstem. Respiratory-related neural activity was recorded from cranial nerve roots in isolated brainstem-spinal cord preparations from 7 premetamorphic tadpoles and 10 adults. Changes in fictive gill/lung activity in tadpoles and buccal/lung activity in adults were examined during superfusion with artificial CSF (aCSF) with [K(+)](o) ranging from 1 to 12 mM (4 mM control). In tadpoles, both fictive gill burst frequency (f(gill)) and lung burst frequency (f(lung)) were significantly dependent upon [K(+)](o) (r(2) > 0.75; p < 0.001) from 1 to 10 mM K(+), and there was a strong correlation between f(gill) and f(lung) (r(2) = 0.65; p < 0.001). When [K(+)](o) was raised to 12 mM, there was a reversible abolition of fictive breathing. In adults, fictive buccal frequency (f(buccal)), was significantly dependent on [K(+)](o) (r(2) = 0.47; p < 0.001), but [K(+)](o) had no effect on f(lung) (p > 0.2), and there was no significant correlation between f(buccal) and f(lung). These data suggest that the neural networks driving gill and lung burst activity in tadpoles may be strongly voltage modulated. In adults, buccal activity, the proposed remnant of gill ventilation in adults, also appears to be voltage dependent, but is not correlated with lung burst activity. These results suggest that lung burst activity in amphibians may shift from a "voltage-dependent" state to a "voltage-independent" state during development. This is consistent with the hypothesis that the fundamental mechanisms generating respiratory rhythm in the amphibian brainstem change during development. We hypothesize that lung respiratory rhythm generation in amphibians undergoes a developmental change from a pacemaker to network-driven process.
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Affiliation(s)
- Rachel E Winmill
- Department of Biological Sciences, California State University, Hayward, Hayward, California 94542, USA
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Hedrick MS, Winmill RE. Excitatory and inhibitory effects of tricaine (MS-222) on fictive breathing in isolated bullfrog brain stem. Am J Physiol Regul Integr Comp Physiol 2003; 284:R405-12. [PMID: 12414435 DOI: 10.1152/ajpregu.00418.2002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the direct effects of tricaine methanesulfonate (MS-222), a sodium-channel blocking local anesthetic, on respiratory motor output using an in vitro brain stem preparation of adult North American bullfrogs (Rana catesbeiana). Bullfrogs were anesthetized with halothane, and the brain stem was removed and superfused with artificial cerebrospinal fluid containing MS-222 at concentrations ranging from 0.1 to 1,000 micro M. At the lowest concentration of MS-222, respiratory frequency (fR) increased significantly (P < 0.05), but at higher concentrations, fR progressively decreased and was abolished in all preparations at 1,000 micro M (P < 0.01). Respiratory burst amplitude and burst duration were not affected by MS-222. The frequency of nonrespiratory neural activity did not significantly change with the addition of MS-222 below 1,000 micro M. These data indicate that MS-222 has a significant, direct effect on respiratory motor output from the central nervous system, producing both excitation and inhibition of fictive breathing. The results are consistent with other studies demonstrating that low concentrations of anesthetics generally cause excitation followed by depression at higher concentrations. Although the mechanisms underlying the excitatory effects of MS-222 in this study are unclear, they may include increased excitatory neurotransmission and/or disinhibition of inputs to the respiratory central pattern generator.
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Affiliation(s)
- Michael S Hedrick
- Department of Biological Sciences, California State University, Hayward, California 94542, USA.
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Morales RD, Hedrick MS. Temperature and pH/CO(2) modulate respiratory activity in the isolated brainstem of the bullfrog (Rana catesbeiana). Comp Biochem Physiol A Mol Integr Physiol 2002; 132:477-87. [PMID: 12020664 DOI: 10.1016/s1095-6433(02)00093-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effects of temperature and pH/CO(2) were examined in isolated brainstem preparations from adult North American bullfrogs (Rana catesbeiana). These experiments were undertaken to determine the effects of temperature on fictive breathing, central pH/CO(2) chemoreception, and to examine potential alphastat regulation of respiration in vitro. Adult bullfrog brainstem preparations were isolated, superfused with an artificial cerebrospinal fluid (aCSF) and respiratory-related neural activity was recorded from cranial nerves V, X and XII. In Series I experiments (N=8), brainstem preparations were superfused with aCSF equilibrated with 2% CO(2) at temperatures ranging from 10 to 30 degrees C. Neural activity was present in all preparations in the temperature range of 15-25 degrees C, but was absent in most preparations when aCSF was at 10 or 30 degrees C. The absence of fictive breathing at high (30 degrees C) temperatures was transient since fictive breathing could be restored upon returning the preparation to 20 degrees C. In Series II experiments (N=10), preparations were superfused with aCSF equilibrated with 0%, 2% and 5% CO(2) at temperatures of 15, 20 and 25 degrees C. Fictive breathing frequency (f(R)) was significantly dependent upon aCSF pH at all three temperatures, with slopes ranging from -0.82 min(-1) pH unit(-1) (15 degrees C) to -3.3 min(-1) pH unit(-1) (20 degrees C). There was a significant difference in these slopes (P<0.02), indicating that central chemoreceptor sensitivity increased over this temperature range. Fictive breathing frequency was significantly dependent upon the calculated alpha-imidazole (alpha(Im)) ionization (P<0.05), consistent with the alphastat hypothesis for the effects of temperature on the regulation of ventilation. However, most of the variation in f(R) was not explained by alpha(Im) (R(2)=0.05), suggesting that other factors account for the regulation of fictive breathing in this preparation. The results indicate that the in vitro brainstem preparation of adult bullfrogs has a limited temperature range (15-25 degrees C) over which fictive breathing is consistently active. Although there is a close correspondence of ventilation in vitro and in vivo at low temperatures, these data suggest that, as temperature increases, changes in ventilation in the intact animal are likely to be more dependent upon peripheral feedback which assumes a greater integrative role with respect to chemoreceptor drive, respiratory frequency and tidal volume.
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Affiliation(s)
- Rey D Morales
- Department of Biological Sciences, California State University, Hayward, Hayward, CA 94542, USA
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