1
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Firth BL, Craig PM, Drake DAR, Power M. Impacts of temperature and turbidity on the gill physiology of darter species. Comp Biochem Physiol A Mol Integr Physiol 2024; 291:111589. [PMID: 38253199 DOI: 10.1016/j.cbpa.2024.111589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/18/2024] [Accepted: 01/19/2024] [Indexed: 01/24/2024]
Abstract
Fish gills are complex organs that have direct contact with the environment and perform numerous functions including gas exchange and ion regulation. Determining if gill morphometry can change under different environmental conditions to maintain and/or improve gas exchange and ion regulation is important for understanding if gill plasticity can improve survival with increasing environmental change. We assessed gill morphology (gas exchange and ion regulation metrics), hematocrit and gill Na+/K+ ATPase activity of wild-captured blackside darter (Percina maculata), greenside darter (Etheostoma blennioides), and johnny darter (Etheostoma nigrum) at two temperatures (10 and 25 °C) and turbidity levels (8 and 94 NTU). Samples were collected August and October 2020 in the Grand River to assess temperature differences, and August 2020 in the Thames River to assess turbidity differences. Significant effects of temperature and/or turbidity only impacted ionocyte number, lamellae width, and hematocrit. An increase in temperature decreased ionocyte number while an increase in turbidity increased lamellae width. Hematocrit had a species-specific response for both temperature and turbidity. Findings suggest that the three darter species have limited plasticity in gill morphology, with no observed compensatory changes in hematocrit or Na+/K+ ATPase activity to maintain homeostasis under the different environmental conditions.
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Affiliation(s)
- Britney L Firth
- Department of Biology, University of Waterloo, Waterloo, ON, Canada.
| | - Paul M Craig
- Department of Biology, University of Waterloo, Waterloo, ON, Canada. https://twitter.com/pcraig77
| | - D Andrew R Drake
- Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada, Burlington, ON, Canada
| | - Michael Power
- Department of Biology, University of Waterloo, Waterloo, ON, Canada
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2
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Astrocytic contribution to glutamate-related central respiratory chemoreception in vertebrates. Respir Physiol Neurobiol 2021; 294:103744. [PMID: 34302992 DOI: 10.1016/j.resp.2021.103744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/01/2021] [Accepted: 07/18/2021] [Indexed: 12/24/2022]
Abstract
Central respiratory chemoreceptors play a key role in the respiratory homeostasis by sensing CO2 and H+ in brain and activating the respiratory neural network. This ability of specific brain regions to respond to acidosis and hypercapnia is based on neuronal and glial mechanisms. Several decades ago, glutamatergic transmission was proposed to be involved as a main mechanism in central chemoreception. However, a complete identification of mechanism has been elusive. At the rostral medulla, chemosensitive neurons of the retrotrapezoid nucleus (RTN) are glutamatergic and they are stimulated by ATP released by RTN astrocytes in response to hypercapnia. In addition, recent findings show that caudal medullary astrocytes in brainstem can also contribute as CO2 and H+ sensors that release D-serine and glutamate, both gliotransmitters able to activate the respiratory neural network. In this review, we describe the mammalian astrocytic glutamatergic contribution to the central respiratory chemoreception trying to trace in vertebrates the emergence of several components involved in this process.
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3
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Rocha ACG, Cristina-Silva C, Taxini CL, da Costa Silva KS, Lima VTM, Macari M, Bícego KC, Szawka RE, Gargaglioni LH. Embryonic Thermal Manipulation Affects Ventilation, Metabolism, Thermal Control and Central Dopamine in Newly Hatched and Juvenile Chicks. Front Physiol 2021; 12:699142. [PMID: 34220555 PMCID: PMC8249324 DOI: 10.3389/fphys.2021.699142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 05/20/2021] [Indexed: 11/29/2022] Open
Abstract
The first third of incubation is critical for embryonic development, and environmental changes during this phase can affect the physiology and survival of the embryos. We evaluated the effects of low (LT), control (CT), and high (HT) temperatures during the first 5 days of incubation on ventilation (V.E), body temperature (Tb), oxygen consumption (V.O2), respiratory equivalent (V.E/V.O2), and brain monoamines on 3-days-old (3d) and 14-days-old (14d) male and female chickens. The body mass of LT animals of both ages and sexes was higher compared to HT and CT animals (except for 3d males). The heart mass of 14d HT animals was higher than that of CT animals. Thermal manipulation did not affect V.E, V.O2 or V.E/V.O2 of 3d animals in normoxia, except for 3d LT males V.E, which was lower than CT. Regarding 14d animals, the HT females showed a decrease in V.E and V.O2 compared to CT and LT groups, while the HT males displayed a lower V.O2 compared to CT males, but no changes in V.E/V.O2. Both sexes of 14d HT chickens presented a greater Tb compared to CT animals. Thermal manipulations increased the dopamine turnover in the brainstem of 3d females. No differences were observed in ventilatory and metabolic parameters in the 3d animals of either sexes, and 14d males under 7% CO2. The hypercapnic hyperventilation was attenuated in the 14d HT females due to changes in V.O2, without alterations in V.E. The 14d LT males showed a lower V.E, during hypercapnia, compared to CT, without changes in V.O2, resulting in an attenuation in V.E/V.O2. During hypoxia, 3d LT females showed an attenuated hyperventilation, modulated by a higher V.O2. In 14d LT and HT females, the increase in V.E was greater and the hypometabolic response was attenuated, compared to CT females, which resulted in no change in the V.E/V.O2. In conclusion, thermal manipulations affect hypercapnia-induced hyperventilation more so than hypoxic challenge, and at both ages, females are more affected by thermal manipulation than males.
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Affiliation(s)
- Aline C G Rocha
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, São Paulo, Brazil
| | - Caroline Cristina-Silva
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, São Paulo, Brazil
| | | | - Kaoma Stephani da Costa Silva
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais - UFMG, Belo Horizonte, Brazil
| | - Virgínia T M Lima
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais - UFMG, Belo Horizonte, Brazil
| | - Marcos Macari
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, São Paulo, Brazil
| | - Kênia C Bícego
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, São Paulo, Brazil
| | - Raphael E Szawka
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais - UFMG, Belo Horizonte, Brazil
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinarian Sciences, São Paulo State University, São Paulo, Brazil
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4
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Dale N. CO 2 sensing by connexin26 and its role in the control of breathing. Interface Focus 2021; 11:20200029. [PMID: 33633831 PMCID: PMC7898151 DOI: 10.1098/rsfs.2020.0029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/14/2022] Open
Abstract
Breathing is essential to provide the O2 required for metabolism and to remove its inevitable CO2 by-product. The rate and depth of breathing is controlled to regulate the excretion of CO2 to maintain the pH of arterial blood at physiological values. A widespread consensus is that chemosensory cells in the carotid body and brainstem measure blood and tissue pH and adjust the rate of breathing to ensure its homeostatic regulation. In this review, I shall consider the evidence that underlies this consensus and highlight historical data indicating that direct sensing of CO2 also plays a significant role in the regulation of breathing. I shall then review work from my laboratory that provides a molecular mechanism for the direct detection of CO2 via the gap junction protein connexin26 (Cx26) and demonstrates the contribution of this mechanism to the chemosensory regulation of breathing. As there are many pathological mutations of Cx26 in humans, I shall discuss which of these alter the CO2 sensitivity of Cx26 and the extent to which these mutations could affect human breathing. I finish by discussing the evolution of the CO2 sensitivity of Cx26 and its link to the evolution of amniotes.
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Affiliation(s)
- Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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5
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Wang X, Lv Y, Xie J, Li B, Zhou T, Chen Y, Chen Y, Song J. Brain regions of marine medaka activated by acute and short-term ocean acidification. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 720:137279. [PMID: 32145610 DOI: 10.1016/j.scitotenv.2020.137279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/10/2020] [Accepted: 02/11/2020] [Indexed: 05/28/2023]
Abstract
Altered behaviors have been reported in many marine fish following exposure to high CO2 concentrations. However, the mechanistic link between elevated CO2 and activation of brain regions in fish is unknown. Herein, we examined the relative quantification and location of c-Fos expression in marine medaka following acute (360 min) and short-term (7 d) exposure to CO2-enriched water (1000 ppm and 1800 ppm CO2). In the control and two treatment groups, pH was stable at 8.21, 7.92 and 7.64, respectively. After acute exposure to seawater acidified by enrichment with CO2, there was a clear upregulation of c-Fos protein in the medaka brain (P < 0.05). c-Fos protein expression peaked after 120 min exposure in the two treatment groups and thereafter began to decline. There were marked increases in c-Fos-labeling in the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata. After 1800 ppm CO2 exposure for 7 d, medaka showed significant preference for dark zones during the initial 2 min period. c-Fos protein expression in the ventricular and periventricular zones of the diencephalon in medaka exposed to 1000 ppm and 1800 ppm CO2 were 0.51 ± 0.10 and 1.34 ± 0.30, respectively, which were significantly higher than controls (P < 0.05). Highest doublecortin protein expression occurred in theventricular zones of the diencephalon and mesencephalon. These findings suggest that the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata of marine medaka are involved in rapid acid-base regulation. Prolonged ocean acidification may induce cell mitosis and differentiation in the adult medaka brain.
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Affiliation(s)
- Xiaojie Wang
- Institute for Marine Biosystem and Neurosciences, Shanghai Ocean University, Shanghai 201306, China; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China; National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, China.
| | - Yutao Lv
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Jinling Xie
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Baolin Li
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Tangjian Zhou
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Yaqi Chen
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Yi Chen
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Jiakun Song
- Institute for Marine Biosystem and Neurosciences, Shanghai Ocean University, Shanghai 201306, China; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China
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6
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Gam LTH, Thanh Huong DT, Tuong DD, Phuong NT, Jensen FB, Wang T, Bayley M. Effects of temperature on acid-base regulation, gill ventilation and air breathing in the clown knifefish, Chitala ornata. J Exp Biol 2020; 223:jeb216481. [PMID: 32001546 DOI: 10.1242/jeb.216481] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/23/2020] [Indexed: 11/20/2022]
Abstract
Chitala ornata is a facultative air-breathing fish, which at low temperatures shows an arterial PCO2 (PaCO2 ) level only slightly elevated above that of water breathers. By holding fish with in-dwelling catheters at temperatures from 25 to 36°C and measuring blood gasses, we show that this animal follows the ubiquitous poikilotherm pattern of reducing arterial pH with increasing temperature. Surprisingly, the temperature increase caused an elevation of PaCO2 from 5 to 12 mmHg while the plasma bicarbonate concentration remained constant at around 8 mmol l-1 The temperature increase also gave rise to a larger fractional increase in air breathing than in gill ventilation frequency. These findings suggest that air breathing, and hence the partitioning of gas exchange, is to some extent regulated by acid-base status in air-breathing fish and that these bimodal breathers will be increasingly likely to adopt respiratory pH control as temperature rises, providing an interesting avenue for future research.
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Affiliation(s)
- Le Thi Hong Gam
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Do Thi Thanh Huong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Dang Diem Tuong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Nguyen Thanh Phuong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Frank Bo Jensen
- Department of Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
- Aarhus Institute of Advanced Studies, 8000 Aarhus C, Denmark
| | - Mark Bayley
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
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7
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Nunan BL, Silva AS, Wang T, da Silva GS. Respiratory control of acid-base status in lungfish. Comp Biochem Physiol A Mol Integr Physiol 2019; 237:110533. [DOI: 10.1016/j.cbpa.2019.110533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 07/02/2019] [Accepted: 07/31/2019] [Indexed: 01/19/2023]
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8
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Chemoreceptors as a key to understanding carcinogenesis process. Semin Cancer Biol 2019; 60:362-364. [PMID: 31622661 DOI: 10.1016/j.semcancer.2019.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/04/2019] [Accepted: 10/04/2019] [Indexed: 11/22/2022]
Abstract
The tissue organization field theory (TOFT) presented completely new, different from the previous one, perspective of research on neoplasm processes. It implicates that secretory neuroepithelial-like cells (NECs), putative chemoreceptors are probably responsible for the control of squamous epithelial cells proliferation in the digestive tract during hypoxia in gut breathing fish (GBF). On the other hand, chemoreceptors dysfunction can lead to uncontrolled proliferation and risk of cancer development in mammals, including humans. The studies on NECs like cells (signal capturing and transduction) may be crucial for understanding the processes of controlling the proliferation of squamous epithelial cells in the digestive tract of GBF fish during hypoxia states. This knowledge can contribute to the explanation of cancer processes.
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9
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Sex differences in breathing. Comp Biochem Physiol A Mol Integr Physiol 2019; 238:110543. [PMID: 31445081 DOI: 10.1016/j.cbpa.2019.110543] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 01/15/2023]
Abstract
Breathing is a vital behavior that ensures both the adequate supply of oxygen and the elimination of CO2, and it is influenced by many factors. Despite that most of the studies in respiratory physiology rely heavily on male subjects, there is much evidence to suggest that sex is an important factor in the respiratory control system, including the susceptibility for some diseases. These different respiratory responses in males and females may be related to the actions of sex hormones, especially in adulthood. These hormones affect neuromodulatory systems that influence the central medullary rhythm/pontine pattern generator and integrator, sensory inputs to the integrator and motor output to the respiratory muscles. In this article, we will first review the sex dependence on the prevalence of some respiratory-related diseases. Then, we will discuss the role of sex and gonadal hormones in respiratory control under resting conditions and during respiratory challenges, such as hypoxia and hypercapnia, and whether hormonal fluctuations during the estrous/menstrual cycle affect breathing control. We will then discuss the role of the locus coeruleus, a sexually dimorphic CO2/pH-chemosensitive nucleus, on breathing regulation in males and females. Next, we will highlight the studies that exist regarding sex differences in respiratory control during development. Finally, the few existing studies regarding the influence of sex on breathing control in non-mammalian vertebrates will be discussed.
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10
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Seasonal variation of hypoxic and hypercarbic ventilatory responses in the lizard Tropidurus torquatus. Comp Biochem Physiol A Mol Integr Physiol 2019; 237:110534. [PMID: 31401309 DOI: 10.1016/j.cbpa.2019.110534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 07/27/2019] [Accepted: 08/01/2019] [Indexed: 12/23/2022]
Abstract
Carbon dioxide (CO2) and oxygen (O2) influence the breathing pattern of reptiles, especially when CO2 is in excess or O2 at low concentrations and the effects of these gases on the respiratory response varies according to the species. In addition to respiratory gases, seasonal changes can also modulate breathing pattern and ventilatory responses to hypoxia and hypercarbia. Therefore, the present study investigated the breathing pattern and ventilatory responses to hypercarbia (5% CO2) and hypoxia (5% O2) of the Neotropical lizard Tropidurus torquatus over a period of one year, covering all seasons (summer, autumn, winter and spring). Our data suggest that like other ectothermic sauropsids, Tropidurus torquatus possesses distinct ventilatory responses to hypoxia and hypercarbia, being more sensitive to changes in CO2 than in O2. Additionally, the ventilatory responses to hypoxia were more pronounced during summer and hypercanic and pos-hypercapnic ventilatory response was reduced during spring, suggesting that seasonality modulates the control of ventilation in this species.
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11
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Levy J, Facchinetti P, Jan C, Achour M, Bouvier C, Brunet JF, Delzescaux T, Giuliano F. Tridimensional mapping of Phox2b expressing neurons in the brainstem of adult Macaca fascicularis and identification of the retrotrapezoid nucleus. J Comp Neurol 2019; 527:2875-2884. [PMID: 31071232 DOI: 10.1002/cne.24713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/29/2019] [Accepted: 04/29/2019] [Indexed: 11/08/2022]
Abstract
Chemosensitivity is a key mechanism for the regulation of breathing in vertebrates. The retrotrapezoid nucleus is a crucial hub for respiratory chemoreception within the brainstem. It integrates chemosensory information that are both peripheral from the carotid bodies (via the nucleus of the solitary tract) and central through the direct sensing of extracellular protons. To date, the location of a genetically defined RTN has only been ascertained in rodents. We first demonstrated that Phox2b, a key determinant for the development of the visceral nervous system and branchiomotor nuclei in the brainstem including the RTN, had a similar distribution in the brainstem of adult macaques compared to adult rats. Second, based on previous description of a specific molecular signature for the RTN in rats, and on an innovative technique for duplex in situ hybridization, we identified parafacial neurons which coexpressed Phox2b and ppGal mRNAs. They were located ventrally to the nucleus of the facial nerve and extended from the caudal part of the nucleus of the superior olive to the rostral tip of the inferior olive. Using the previously described blockface technique, deformations were corrected to allow the proper alignment and stacking of digitized sections, hence providing for the first time a 3D reconstruction of the macaque brainstem, Phox2b distribution and the primate retrotrapezoid nucleus. This description should help bridging the gap between rodents and humans for the description of key respiratory structures in the brainstem.
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Affiliation(s)
- Jonathan Levy
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France.,Service de Médecine Physique et de Réadaptation-APHP, Hôpital Raymond Poincaré, Garches, France.,Fondation Garches-APHP, Hôpital Raymond Poincaré, Garches, France
| | - Patricia Facchinetti
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France
| | - Caroline Jan
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,CNRS-CEA UMR9199-Neurodegenerative Diseases Laboratory, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - Mélyna Achour
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France
| | - Clément Bouvier
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,NEOXIA, Paris, France
| | - Jean-François Brunet
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole normale supérieure, CNRS, INSERM, PSL Université, Paris, France
| | - Thierry Delzescaux
- Molecular Imaging Research Center (MIRCen)-Commissariat à l'Énergie Atomique (CEA), Fontenay-aux-Roses, France.,CNRS-CEA UMR9199-Neurodegenerative Diseases Laboratory, Université Paris-Saclay, Fontenay-aux-Roses, France
| | - François Giuliano
- INSERM UMR1179-Handicap Neuromusculaire, Université de Versailles Saint-Quentin-en-Yvelines, Montigny-le-Bretonneux, France.,Service de Médecine Physique et de Réadaptation-APHP, Hôpital Raymond Poincaré, Garches, France
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12
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Bayley M, Damsgaard C, Thomsen M, Malte H, Wang T. Learning to Air-Breathe: The First Steps. Physiology (Bethesda) 2019; 34:14-29. [DOI: 10.1152/physiol.00028.2018] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Air-breathing in vertebrates has evolved many times among the bony fish while in water. Its appearance has had a fundamental impact on the regulation of ventilation and acid-base status. We review the physico-chemical constraints imposed by water and air, place the extant air-breathing fish into this framework, and show how that the advantages of combining control of ventilation and acid-base status are only available to the most obligate of air-breathing fish, thus highlighting promising avenues for research.
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Affiliation(s)
- Mark Bayley
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Christian Damsgaard
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mikkel Thomsen
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Hans Malte
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Tobias Wang
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
- Aarhus Institute of Advanced Sciences, Aarhus University, Aarhus, Denmark
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13
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Abstract
Respiratory chemoreceptors in vertebrates are specialized cells that detect chemical changes in the environment or arterial blood supply and initiate autonomic responses, such as hyperventilation or changes in heart rate, to improve O2 uptake and delivery to tissues. These chemoreceptors are sensitive to changes in O2, CO2 and/or H+. In fish and mammals, respiratory chemoreceptors may be additionally sensitive to ammonia, hypoglycemia, and numerous other stimuli. Thus, chemoreceptors that affect respiration respond to different types of stimuli (or modalities) and are considered to be "polymodal". This review discusses the polymodal nature of respiratory chemoreceptors in vertebrates with a particular emphasis on chemoreceptors of the carotid body and pulmonary epithelium in mammals, and on neuroepithelial cells in water- and air-breathing fish. A major goal will be to examine the evidence for putative polymodal chemoreceptors in fish within the context of studies on mammalian models, for which polymodal chemoreceptors are well described, in order to improve our understanding of the evolution of polymodal chemoreceptors in vertebrates, and to aid in future studies that aim to identify putative receptors in air- and water-breathing fish.
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14
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de Wolf E, Cook J, Dale N. Evolutionary adaptation of the sensitivity of connexin26 hemichannels to CO2. Proc Biol Sci 2017; 284:20162723. [PMID: 28148750 PMCID: PMC5310615 DOI: 10.1098/rspb.2016.2723] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 01/06/2017] [Indexed: 11/12/2022] Open
Abstract
CO2 readily combines with H2O to form [Formula: see text] and H+ Because an increase of only 100 nM in the concentration of H+ (a decrease of 0.1 unit of pH) in blood can prove fatal, the regulated excretion of CO2 during breathing is an essential life-preserving process. In rodents and humans, this vital process is mediated in part via the direct sensing of CO2 via connexin26 (Cx26). CO2 binds to hemichannels of Cx26 causing them to open and allow release of the neurotransmitter ATP. If Cx26 were to be a universal and important CO2 sensor across all homeothermic animals, then a simple hypothesis would posit that it should exhibit evolutionary adaptation in animals with different homeostatic set points for the regulation of partial pressure of arterial CO2 (PaCO2). In humans and rats, PaCO2 is regulated around a set point of 40 mmHg. By contrast, birds are able to maintain cerebral blood flow and breathing at much lower levels of PaCO2 Fossorial mammals, such as the mole rat, live exclusively underground in burrows that are both hypoxic and hypercapnic and can thrive under very hypercapnic conditions. We have therefore compared the CO2 sensitivity of Cx26 from human, chicken, rat and mole rat (Heterocephalus glaber). We find that both the affinity and cooperativity of CO2 binding to Cx26 have been subjected to evolutionary adaption in a manner consistent with the homeostatic requirements of these four species. This is analogous to the evolutionary adaptation of haemoglobin to the needs of O2 transport across the animal kingdom and supports the hypothesis that Cx26 is an important and universal CO2 sensor in homeotherms.
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Affiliation(s)
- Elizabeth de Wolf
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry CV4 7AL, UK
| | - Jonathan Cook
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry CV4 7AL, UK
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Gibbet Hill Rd, Coventry CV4 7AL, UK
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15
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Hillman SS, Hedrick MS. A metabolic hypothesis for the evolution of temperature effects on the arterial PCO2 and pH of vertebrate ectotherms. J Exp Biol 2017; 221:jeb.168955. [DOI: 10.1242/jeb.168955] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/14/2017] [Indexed: 11/20/2022]
Abstract
Body temperature increases in ectothermic vertebrates characteristically lead to both increases in arterial PCO2 (PaCO2) and declines in resting arterial pH (pHa) of about 0.017 pH units/°C increase in temperature. This ‘alphastat’ pH pattern has previously been interpreted as being evolutionarily-driven by the maintenance of a constant protonation state on the imidazole moiety of histidine protein residues, hence stabilizing protein structure-function. Analysis of the existing data for interclass responses of ectothermic vertebrates show different degrees of PaCO2 increases and pH declines with temperature between the classes with reptiles>amphibians>fish. The PaCO2 at the temperature where maximal aerobic metabolism (VO2max) is achieved is significantly and positively correlated with temperature for all vertebrate classes. For ectotherms, the PaCO2 where VO2max is greatest is also correlated with VO2max indicating there is an increased driving force for CO2 efflux that is lowest in fish, intermediate in amphibians and highest in reptiles. The pattern of increased PaCO2 and the resultant reduction of pHa to increased body temperature would serve to increase CO2 efflux, O2 delivery, blood buffering capacity and maintain ventilatory scope. This represents a new hypothesis for the selective advantage of arterial pH regulation from a systems physiology perspective in addition to the advantages of maintenance of protein structure-function.
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Affiliation(s)
- Stanley S. Hillman
- Department of Biology, Portland State University, Portland, OR 97207, USA
| | - Michael S. Hedrick
- Department of Biological Sciences, California State University East Bay, Hayward, CA 94542, USA
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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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Belão T, Zeraik V, Florindo L, Kalinin A, Leite C, Rantin F. Control of cardiorespiratory function in response to hypoxia in an air-breathing fish, the African sharptooth catfish, Clarias gariepinus. Comp Biochem Physiol A Mol Integr Physiol 2015; 187:130-40. [DOI: 10.1016/j.cbpa.2015.05.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 05/12/2015] [Accepted: 05/15/2015] [Indexed: 12/17/2022]
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18
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Zhang L, Michele Nawata C, De Boeck G, Wood CM. Rh protein expression in branchial neuroepithelial cells, and the role of ammonia in ventilatory control in fish. Comp Biochem Physiol A Mol Integr Physiol 2014; 186:39-51. [PMID: 25465530 DOI: 10.1016/j.cbpa.2014.10.004] [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: 06/22/2014] [Revised: 10/14/2014] [Accepted: 10/14/2014] [Indexed: 01/02/2023]
Abstract
Bill Milsom has made seminal contributions to our understanding of ventilatory control in a wide range of vertebrates. Teleosts are particularly interesting, because they produce a 3rd, potentially toxic respiratory gas (ammonia) in large amounts. Fish are well known to hyperventilate under high environmental ammonia (HEA), but only recently has the potential role of ammonia in normal ventilatory control been investigated. It is now clear that ammonia can act directly as a ventilatory stimulant in trout, independent of its effects on acid-base balance. Even in ureotelic dogfish sharks, acute elevations in ammonia cause increases in ventilation. Peripherally, the detection of elevated ammonia resides in gill arches I and II in trout, and in vitro, neuroepithelial cells (NECs) from these arches are sensitive to ammonia, responding with elevations in intracellular Ca(2+) ([Ca(2+)]i). Centrally, hyperventilatory responses to ammonia correlate more closely with concentrations of ammonia in the brain than in plasma or CSF. After chronic HEA exposure, ventilatory responsiveness to ammonia is lost, associated with both an attenuation of the [Ca(2+)]i response in NECs, and the absence of elevation in brain ammonia concentration. Chronic exposure to HEA also causes increases in the mRNA expression of several Rh proteins (ammonia-conductive channels) in both brain and gills. "Single cell" PCR techniques have been used to isolate the individual responses of NECs versus other gill cell types. We suggest several circumstances (post-feeding, post-exercise) where the role of ammonia as a ventilatory stimulant may have adaptive benefits for O2 uptake in fish.
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Affiliation(s)
- Li Zhang
- Dept. of Biology, McMaster University, Hamilton, Canada; Key Laboratory of Marine Bio-resources Sustainable Utilization, South China Sea Institute of Oceanology, Guangzhou, China
| | - C Michele Nawata
- Dept. of Biology, McMaster University, Hamilton, Canada; Dept. of Physiology, University of Arizona, Tucson, USA; Bamfield Marine Sciences Centre, Bamfield, Canada
| | - Gudrun De Boeck
- Bamfield Marine Sciences Centre, Bamfield, Canada; SPHERE, Dept. of Biology, University of Antwerp, Antwerp, Belgium
| | - Chris M Wood
- Dept. of Biology, McMaster University, Hamilton, Canada; Bamfield Marine Sciences Centre, Bamfield, Canada; Dept. of Zoology, University of British Columbia, Vancouver, Canada.
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Marschand RE, Wilson JL, Burleson ML, Crossley DA, Hedrick MS. Effects of prolonged lung inflation or deflation on pulmonary stretch receptor discharge in the alligator (Alligator mississippiensis). Respir Physiol Neurobiol 2014; 200:25-32. [PMID: 24874556 DOI: 10.1016/j.resp.2014.05.006] [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: 01/31/2014] [Revised: 05/08/2014] [Accepted: 05/11/2014] [Indexed: 11/26/2022]
Abstract
The American alligator (Alligator mississippiensis) is a semi-aquatic diving reptile that has a periodic breathing pattern. Previous work identified pulmonary stretch receptors, that are rapidly and slowly adapting, as well as intrapulmonary chemoreceptors (IPC), sensitive to CO2, that modulate breathing patterns in alligators. The purpose of the present study was to quantify the effects of prolonged lung inflation and deflation (simulated dives) on pulmonary stretch receptors (PSR) and/or IPC discharge characteristics. The effects of airway pressure (0-20 cm H2O), hypercapnia (7% CO2), and hypoxia (5% O2) on dynamic and static responses of PSR were studied in juvenile alligators (mean mass=246 g) at 24°C. Alligators were initially anesthetized with isoflurane, cranially pithed, tracheotomized and artificially ventilated. Vagal afferent tonic and phasic activity was recorded with platinum hook electrodes. Receptor activity was a mixture of slowly adapting PSR (SAR) and rapidly adapting PSR (RAR) with varying thresholds and degrees of adaptation, without CO2 sensitivity. Receptor activity before, during and after 1 min periods of lung inflation and deflation was quantified to examine the effect of simulated breath-hold dives. Some PSR showed a change in dynamic response, exhibiting inhibition for several breaths after prolonged lung inflation. Following 1 min deflation, RAR, but not SAR, exhibited a significant potentiation of burst frequency relative to control. For SAR, the post-inflation receptor inhibition was blocked by CO2 and hypoxia; for RAR, the post-inflation inhibition was potentiated by CO2 and blocked by hypoxia. These results suggest that changes in PSR firing following prolonged inflation and deflation may promote post-dive ventilation in alligators. We hypothesize that PSR in alligators may be involved in recovery of breathing patterns and lung volume during pre- and post-diving behavior and apneic periods in diving reptiles.
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Affiliation(s)
- Rachel E Marschand
- Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Jenna L Wilson
- Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Mark L Burleson
- Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Dane A Crossley
- Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States
| | - Michael S Hedrick
- Developmental Integrative Biology Research Cluster, Department of Biological Sciences, University of North Texas, Denton, TX 76203, United States.
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20
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Espinha LP, Souza FA, Capalbo AC, Bícego KC, Macari M, Gargaglioni LH. Age and gender influence the cardiorespiratory function and metabolic rate of broiler chicks during normocapnia and hypercapnia. Respir Physiol Neurobiol 2014; 200:50-6. [DOI: 10.1016/j.resp.2014.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 05/26/2014] [Accepted: 05/29/2014] [Indexed: 01/26/2023]
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21
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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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22
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Malan A. The Evolution of Mammalian Hibernation: Lessons from Comparative Acid-Base Physiology. Integr Comp Biol 2014; 54:484-96. [DOI: 10.1093/icb/icu002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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23
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Abstract
Hibernation in endotherms and ectotherms is characterized by an energy-conserving metabolic depression due to low body temperatures and poorly understood temperature-independent mechanisms. Rates of gas exchange are correspondly reduced. In hibernating mammals, ventilation falls even more than metabolic rate leading to a relative respiratory acidosis that may contribute to metabolic depression. Breathing in some mammals becomes episodic and in some small mammals significant apneic gas exchange may occur by passive diffusion via airways or skin. In ectothermic vertebrates, extrapulmonary gas exchange predominates and in reptiles and amphibians hibernating underwater accounts for all gas exchange. In aerated water diffusive exchange permits amphibians and many species of turtles to remain fully aerobic, but hypoxic conditions can challenge many of these animals. Oxygen uptake into blood in both endotherms and ectotherms is enhanced by increased affinity of hemoglobin for O₂ at low temperature. Regulation of gas exchange in hibernating mammals is predominately linked to CO₂/pH, and in episodic breathers, control is principally directed at the duration of the apneic period. Control in submerged hibernating ectotherms is poorly understood, although skin-diffusing capacity may increase under hypoxic conditions. In aerated water blood pH of frogs and turtles either adheres to alphastat regulation (pH ∼8.0) or may even exhibit respiratory alkalosis. Arousal in hibernating mammals leads to restoration of euthermic temperature, metabolic rate, and gas exchange and occurs periodically even as ambient temperatures remain low, whereas body temperature, metabolic rate, and gas exchange of hibernating ectotherms are tightly linked to ambient temperature.
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Affiliation(s)
- William K Milsom
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia, Canada
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24
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Zeraik VM, Belão TC, Florindo LH, Kalinin AL, Rantin FT. Branchial O2 chemoreceptors in Nile tilapia Oreochromis niloticus: Control of cardiorespiratory function in response to hypoxia. Comp Biochem Physiol A Mol Integr Physiol 2013; 166:17-25. [DOI: 10.1016/j.cbpa.2013.04.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 04/24/2013] [Accepted: 04/29/2013] [Indexed: 01/15/2023]
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25
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Mechanisms and consequences of carbon dioxide sensing in fish. Respir Physiol Neurobiol 2012; 184:309-15. [DOI: 10.1016/j.resp.2012.06.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 06/09/2012] [Accepted: 06/10/2012] [Indexed: 11/20/2022]
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26
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Lefevre S, Wang T, Huong DTT, Phuong NT, Bayley M. Partitioning of oxygen uptake and cost of surfacing during swimming in the air-breathing catfish Pangasianodon hypophthalmus. J Comp Physiol B 2012; 183:215-21. [DOI: 10.1007/s00360-012-0701-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 07/24/2012] [Accepted: 07/27/2012] [Indexed: 11/25/2022]
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27
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Fonseca EM, da Silva GS, Fernandes M, Giusti H, Noronha-de-Souza CR, Glass ML, Bícego KC, Gargaglioni LH. The breathing pattern and the ventilatory response to aquatic and aerial hypoxia and hypercarbia in the frog Pipa carvalhoi. Comp Biochem Physiol A Mol Integr Physiol 2012; 162:281-7. [DOI: 10.1016/j.cbpa.2012.03.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 03/27/2012] [Accepted: 03/27/2012] [Indexed: 11/30/2022]
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Gilmour KM. New insights into the many functions of carbonic anhydrase in fish gills. Respir Physiol Neurobiol 2012; 184:223-30. [PMID: 22706265 DOI: 10.1016/j.resp.2012.06.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 05/31/2012] [Accepted: 06/01/2012] [Indexed: 01/25/2023]
Abstract
Carbonic anhydrase (CA) is a zinc metalloenzyme that catalyzes the reversible reactions of carbon dioxide and water: CO(2) + H(2)O ↔ H(+) + HCO(3)(-). It has long been recognized that CA is abundant in the fish gill, with attention focused on the role of CA in catalyzing the hydration of CO(2) to provide H(+) and HCO(3)(-) for the branchial ion transport processes that underlie systemic ionic and acid-base regulation. Recent work has explored the diversity of CA isoforms in the fish gill. By linking these isoforms to different cell types in the gill, and by exploiting the diversity of fish species available for study, this work is increasing our understanding of the many roles that CA plays in the fish gill. In particular, recent work has revealed that fish utilize more than one model of CO(2) excretion, that to understand the role of CA and the gill in ionic regulation and acid-base balance means characterizing the transporter and CA complement of individual cell types, and that CA plays roles in branchial sensory mechanisms. The goal of this brief review is to summarize these new developments, while at the same time highlighting key areas in which further research is needed.
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Affiliation(s)
- Kathleen M Gilmour
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N 6N5, Canada.
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Metabolic changes associated with acid–base regulation during hypercarbia in the CO2-tolerant chondrostean, white sturgeon (Acipenser transmontanus). Comp Biochem Physiol A Mol Integr Physiol 2012; 161:61-8. [DOI: 10.1016/j.cbpa.2011.09.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 09/08/2011] [Accepted: 09/08/2011] [Indexed: 01/05/2023]
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30
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Hempleman SC, Pilarski JQ. Prenatal development of respiratory chemoreceptors in endothermic vertebrates. Respir Physiol Neurobiol 2011; 178:156-62. [PMID: 21569865 PMCID: PMC3146631 DOI: 10.1016/j.resp.2011.04.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2011] [Revised: 04/27/2011] [Accepted: 04/28/2011] [Indexed: 10/18/2022]
Abstract
Respiratory chemoreceptors are neurons that detect PCO(2), PO(2), and/or pH in body fluids and provide sensory feedback for the control of breathing. They play a critical role in coupling pulmonary ventilation to metabolic demand in endothermic vertebrates. During birth in mammals and hatching in birds, the state change from placental or chorioallantoic gas exchange to pulmonary respiration makes acute demands on the neonatal lungs and ventilatory control system, including the respiratory chemoreceptors. Here we review the literature on prenatal development of carotid body chemoreceptors, central chemoreceptors, and airway chemoreceptors, with emphasis on the histology, histochemistry, and neurophysiology of chemosensory cells or their afferents, and their physiological genomics if known. In general, respiratory chemoreceptors develop prenatally and are functional but immature at birth or hatching. Each type of respiratory chemoreceptor has a unique prenatal developmental time course, and all studied to date require a period of postnatal maturation to express the full adult response.
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Affiliation(s)
- Steven C Hempleman
- Department of Biology, Northern Arizona University, Flagstaff, AZ 86011-5640, USA.
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31
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Chronic hypoxia and chronic hypercapnia differentially regulate an NMDA-sensitive component of the acute hypercapnic ventilatory response in the cane toad (Rhinella marina). J Comp Physiol B 2011; 181:793-805. [DOI: 10.1007/s00360-011-0556-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 01/18/2011] [Accepted: 01/31/2011] [Indexed: 10/18/2022]
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de Lima Boijink C, Florindo LH, Leite CAC, Kalinin AL, Milsom WK, Rantin FT. Hypercarbic cardiorespiratory reflexes in the facultative air-breathing fish jeju (Hoplerythrinus unitaeniatus): the role of branchial CO2 chemoreceptors. J Exp Biol 2010; 213:2797-807. [DOI: 10.1242/jeb.040733] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
The aim of the present study was to determine the roles that externally versus internally oriented CO2/H+-sensitive chemoreceptors might play in promoting cardiorespiratory responses to environmental hypercarbia in the air-breathing fish, Hoplerythrinus unitaeniatus (jeju). Fish were exposed to graded hypercarbia (1, 2.5, 5, 10 and 20% CO2) and also to graded levels of environmental acidosis (pH ~7.0, 6.0, 5.8, 5.6, 5.3 and 4.7) equal to the pH levels of the hypercarbic water to distinguish the relative roles of CO2versus H+. We also injected boluses of CO2-equilibrated solutions (5, 10 and 20% CO2) and acid solutions equilibrated to the same pH as the CO2 boluses into the caudal vein (internal) and buccal cavity (external) to distinguish between internal and external stimuli. The putative location of the chemoreceptors was determined by bilateral denervation of branches of cranial nerves IX (glossopharyngeal) and X (vagus) to the gills. The data indicate that the chemoreceptors eliciting bradycardia, hypertension and gill ventilatory responses (increased frequency and amplitude) to hypercarbia are exclusively branchial, externally oriented and respond specifically to changes in CO2 and not H+. Those involved in producing the cardiovascular responses appeared to be distributed across all gill arches while those involved in the gill ventilatory responses were located primarily on the first gill arch. Higher levels of aquatic CO2 depressed gill ventilation and stimulated air breathing. The chemoreceptors involved in producing air breathing in response to hypercarbia also appeared to be branchial, distributed across all gill arches and responded specifically to changes in aquatic CO2. This would suggest that chemoreceptor groups with different orientations (blood versus water) are involved in eliciting air-breathing responses to hypercarbia in jeju.
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Affiliation(s)
- Cheila de Lima Boijink
- Departament of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil
| | - Luiz Henrique Florindo
- Departament of Zoology and Botany, Aquaculture Center (CAUNESP), São Paulo State University – UNESP, 15054-000, São José do Rio Preto, SP, Brazil
- National Institute of Science and Technology – Comparative Physiology (FAPESP/CNPq), Brazil
| | - Cleo A. Costa Leite
- Departament of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil
- National Institute of Science and Technology – Comparative Physiology (FAPESP/CNPq), Brazil
| | - Ana Lúcia Kalinin
- Departament of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil
- National Institute of Science and Technology – Comparative Physiology (FAPESP/CNPq), Brazil
| | - William K. Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Francisco Tadeu Rantin
- Departament of Physiological Sciences, Federal University of São Carlos, 13565-905 São Carlos, SP, Brazil
- National Institute of Science and Technology – Comparative Physiology (FAPESP/CNPq), Brazil
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Milsom WK. Adaptive trends in respiratory control: a comparative perspective. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1-10. [DOI: 10.1152/ajpregu.00069.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In 1941, August Krogh published a monograph entitled The Comparative Physiology of Respiratory Mechanisms (Philadelphia, PA: University of Pennsylvania Press, 1941). Since that time comparative studies have continued to contribute significantly to our understanding of the fundamentals of respiratory physiology and the adaptive trends in these processes that support a broad range of metabolic performance under demanding environmental conditions. This review specifically focuses on recent advances in our understanding of adaptive trends in respiratory control. Respiratory rhythm generators most likely arose from, and must remain integrated with, rhythm generators for chewing, suckling, and swallowing. Within the central nervous system there are multiple “segmental” rhythm generators, and through evolution there is a caudal shift in the predominant respiratory rhythm-generating site. All sites, however, may still be capable of producing or modulating respiratory rhythm under appropriate conditions. Expression of the respiratory rhythm is conditional on (tonic) input. Once the rhythm is expressed, it is often episodic as the basic medullary rhythm is turned on/off subject to a hierarchy of controls. Breathing patterns reflect differences in pulmonary mechanics resulting from differences in body wall and lung architecture and are modulated in different species by various combinations of upper and lower airway mechanoreceptors and arterial chemoreceptors to protect airways, reduce dead space ventilation, enhance gas exchange efficiency, and reduce the cost of breathing.
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Affiliation(s)
- William K. Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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Milsom WK. The phylogeny of central chemoreception. Respir Physiol Neurobiol 2010; 173:195-200. [PMID: 20594933 DOI: 10.1016/j.resp.2010.05.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 05/27/2010] [Accepted: 05/27/2010] [Indexed: 11/18/2022]
Abstract
Respiratory chemoreceptors responsive to changes in CO(2)/H(+) appear to be present in all vertebrates from fish to birds and mammals. They appear to have arisen first in the periphery sensitive to the external environment. Thus, in most fish CO(2)/H(+) chemoreceptors reside primarily in the gills and respond to changes in aquatic rather than arterial P(CO)₂ . In the air-breathing tetrapods (amphibians, mammals, reptiles and birds), the branchial arches regress developmentally and the derivatives of the branchial arteries are now exclusively internal. The receptors associated with these arteries now sense only arterial (not environmental) P(CO)₂/pH . Central CO(2)/H(+) chemoreception also appears to have arisen with the advent of air breathing, presumably as a second line of defense. These receptors may have arisen multiple times in association with several (but not all) of the independent origins of air breathing in fishes. There is strong evidence for multiple central sites of CO(2)/H(+) sensing, at least in amphibians and mammals, suggesting that it may not only have originated multiple times in different species but also multiple times within a single species.
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Affiliation(s)
- W K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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35
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Qin Z, Lewis JE, Perry SF. Zebrafish (Danio rerio) gill neuroepithelial cells are sensitive chemoreceptors for environmental CO2. J Physiol 2010; 588:861-72. [PMID: 20051495 DOI: 10.1113/jphysiol.2009.184739] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Adult zebrafish exhibit hyperventilatory responses to absolute environmental CO(2) levels as low as 0.13% ( mmHg), more than an order of magnitude lower than the typical arterial levels (40 mmHg) monitored by the mammalian carotid body. The sensory basis underlying the ability of fish to detect and respond to low ambient CO(2) levels is not clear. Here, we show that the neuroepithelial cells (NECs) of the zebrafish gill, known to sense O(2) levels, also respond to low levels of CO(2). An electrophysiological characterization of this response using both current and voltage clamp protocols revealed that for increasing CO(2) levels, a background K(+) channel was inhibited, resulting in a partial pressure-dependent depolarization of the NEC. To elucidate the signalling pathway underlying K(+) channel inhibition, we used immunocytochemistry to show that these NECs express carbonic anhydrase (CA), an enzyme involved in CO(2) sensing in the mammalian carotid body. Further, the NEC response to CO(2) (magnitude of membrane depolarization and time required to achieve maximal response), under conditions of constant pH, was reduced by 50% by the CA-inhibitor acetazolamide. This suggests that the CO(2) detection mechanism involves an intracellular sensor that is responsive to the rate of acidification associated with the hydration of CO(2) and which does not require a change of extracellular pH. Because some cells that were responsive to increasing also responded to hypoxia with membrane depolarization, the present results demonstrate that a subset of the NECs in the zebrafish gill are bimodal sensors of CO(2) and O(2).
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Affiliation(s)
- Z Qin
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada
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Brundage CM, Taylor BE. Timing and duration of developmental nicotine exposure contribute to attenuation of the tadpole hypercapnic neuroventilatory response. Dev Neurobiol 2009; 69:451-61. [PMID: 19360722 DOI: 10.1002/dneu.20720] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The ability for air-breathing vertebrates to adjust ventilation in response to increased CO(2) (hypercapnia) is fundamental to maintaining pH homeostasis. Developmental nicotine exposure has been shown to impair tadpole neuroventilatory responses to hypercapnia following 8-12 weeks of exposure. It is not clear, however, to what extent the timing of exposure during development and/or the duration over which the exposure takes place contribute to this impairment. Here, tadpoles were exposed to 30 microg/L of nicotine for 3- or 10-week durations, either early or late in tadpole development. Correlates of tadpole lung neuroventilation were monitored during normocapnic (1.5% CO(2)) and hypercapnic (5% CO(2)) conditions of isolated brainstems. Preparations derived from early metamorphic tadpoles failed to increase lung neuroventilation in response to hypercapnia whether they had been exposed to nicotine for 3 or 10 weeks. Preparations derived from late metamorphic tadpoles failed to respond to hypercapnia after being exposed to nicotine for 10 weeks. These results suggest that both the developmental timing and duration of exposure are important when considering nicotine's effect on the hypercapnic neuroventilatory response.
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Affiliation(s)
- Cord M Brundage
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA
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Perry S, Vulesevic B, Braun M, Gilmour K. Ventilation in Pacific hagfish (Eptatretus stoutii) during exposure to acute hypoxia or hypercapnia. Respir Physiol Neurobiol 2009; 167:227-34. [DOI: 10.1016/j.resp.2009.04.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 04/28/2009] [Accepted: 04/30/2009] [Indexed: 10/20/2022]
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Aestivation in the South American lungfish, Lepidosiren paradoxa: Effects on cardiovascular function, blood gases, osmolality and leptin levels. Respir Physiol Neurobiol 2008; 164:380-5. [DOI: 10.1016/j.resp.2008.08.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 08/26/2008] [Accepted: 08/29/2008] [Indexed: 11/20/2022]
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Baker CVH, O'Neill P, McCole RB. Lateral line, otic and epibranchial placodes: developmental and evolutionary links? JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:370-83. [PMID: 17638322 PMCID: PMC4209393 DOI: 10.1002/jez.b.21188] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Two embryonic cell populations, the neural crest and cranial ectodermal placodes, between them give rise to many of the unique characters of vertebrates. Neurogenic placode derivatives are vital for sensing both external and internal stimuli. In this speculative review, we discuss potential developmental and evolutionary relationships between two placode series that are usually considered to be entirely independent: lateral line placodes, which form the mechanosensory and electroreceptive hair cells of the anamniote lateral line system as well as their afferent neurons, and epibranchial placodes (geniculate, petrosal and nodose), which form Phox2b(+) visceral sensory neurons with input from both the external and internal environment. We illustrate their development using molecular data we recently obtained in shark embryos, and we describe their derivatives, including the possible geniculate placode origin of a mechanosensory sense organ associated with the first pharyngeal pouch/cleft (the anamniote spiracular organ/amniote paratympanic organ). We discuss how both lateral line and epibranchial placodes can be related in different ways to the otic placode (which forms the inner ear and its afferent neurons), and how both are important for protective somatic reflexes. Finally, we put forward a highly speculative proposal about the original function of the cells whose evolutionary descendants today include the derivatives of the lateral line, otic and epibranchial placodes, namely that they produced sensory receptors and neurons for Phox2b-dependent protective reflex circuits. We hope this review will stimulate both debate and a fresh look at possible developmental and evolutionary relationships between these seemingly disparate and independent placodes.
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Affiliation(s)
- Clare V H Baker
- Department of Physiology, Development and Neuroscience, Anatomy Building, Downing Street, Cambridge, United Kingdom.
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Olson KR, Healy MJ, Qin Z, Skovgaard N, Vulesevic B, Duff DW, Whitfield NL, Yang G, Wang R, Perry SF. Hydrogen sulfide as an oxygen sensor in trout gill chemoreceptors. Am J Physiol Regul Integr Comp Physiol 2008; 295:R669-80. [PMID: 18565835 DOI: 10.1152/ajpregu.00807.2007] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
O2 chemoreceptors elicit cardiorespiratory reflexes in all vertebrates, but consensus on O2-sensing signal transduction mechanism(s) is lacking. We recently proposed that hydrogen sulfide (H2S) metabolism is involved in O2 sensing in vascular smooth muscle. Here, we examined the possibility that H2S is an O2 sensor in trout chemoreceptors where the first pair of gills is a primary site of aquatic O2 sensing and the homolog of the mammalian carotid body. Intrabuccal injection of H2S in unanesthetized trout produced a dose-dependent bradycardia and increased ventilatory frequency and amplitude similar to the hypoxic response. Removal of the first, but not second, pair of gills significantly inhibited H2S-mediated bradycardia, consistent with the loss of aquatic chemoreceptors. mRNA for H2S-synthesizing enzymes, cystathionine beta-synthase and cystathionine gamma-lyase, was present in branchial tissue. Homogenized gills produced H2S enzymatically, and H2S production was inhibited by O2, whereas mitochondrial H2S consumption was O2 dependent. Ambient hypoxia did not affect plasma H2S in unanesthetized trout, but produced a PO2-dependent increase in a sulfide moiety suggestive of increased H2S production. In isolated zebrafish neuroepithelial cells, the putative chemoreceptive cells of fish, both hypoxia and H2S, produced a similar approximately 10-mV depolarization. These studies are consistent with H2S involvement in O2 sensing/signal transduction pathway(s) in chemoreceptive cells, as previously demonstrated in vascular smooth muscle. This novel mechanism, whereby H2S concentration ([H2S]) is governed by the balance between constitutive production and oxidation, tightly couples tissue [H2S] to PO2 and may provide an exquisitely sensitive, yet simple, O2 sensor in a variety of tissues.
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Affiliation(s)
- Kenneth R Olson
- Indiana University School of Medicine-South Bend, 1234 Notre Dame Ave., South Bend, IN 46617, USA.
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Srivaratharajah K, Cui A, McAneney J, Reid SG. Chronic hypoxic hypercapnia modifies in vivo and in vitro ventilatory chemoreflexes in the cane toad. Respir Physiol Neurobiol 2008; 160:249-58. [DOI: 10.1016/j.resp.2007.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 09/21/2007] [Accepted: 10/17/2007] [Indexed: 10/22/2022]
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Perry S, Euverman R, Wang T, Loong A, Chew S, Ip Y, Gilmour K. Control of breathing in African lungfish (Protopterus dolloi): A comparison of aquatic and cocooned (terrestrialized) animals. Respir Physiol Neurobiol 2008; 160:8-17. [DOI: 10.1016/j.resp.2007.06.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 06/28/2007] [Accepted: 06/29/2007] [Indexed: 11/15/2022]
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Milsom WK, Burleson ML. Peripheral arterial chemoreceptors and the evolution of the carotid body. Respir Physiol Neurobiol 2007; 157:4-11. [PMID: 17353155 DOI: 10.1016/j.resp.2007.02.007] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2006] [Revised: 02/12/2007] [Accepted: 02/12/2007] [Indexed: 01/31/2023]
Abstract
There has been a reduction in the distribution of peripheral respiratory O(2) chemoreceptors from multiple, dispersed sites in fish and amphibia to a single dominant receptor site in birds and mammals. In the process, the cells in the fish gill associated with O(2) chemosensing (5-HT containing neuroepithelial cells often found in association with ACh/catecholamine (CA) containing cells) are replaced by the glomus cells of the mammalian carotid body (which contain multiple putative neurotransmitter substances, including 5-HT, CA and ACh, all within the same cells), although this difference may be more superficial than first appears. While still highly speculative, these trends would appear to be correlated with the transition from aquatic respiration and bimodal breathing, and from animals with intra-cardiac shunts (two situations where the ability to sense O(2) at multiple sites would be an advantage), to strictly air breathing in animals with no intra-cardiac shunts. It is also tempting to speculate that while the basic O(2)-sensing mechanism is the same for all receptor cells, the receptor groups in fish have evolved in such a way to make the responses of some more sensitive to changes in O(2) delivery than others. The net result is that those receptors associated with the first gill arch of fish (the third branchial arch) become the carotid body in higher vertebrates associated with the regulation of ventilation and ensuring oxygen supply to the gas exchange surface. Those receptors associated with the second gill arch (fourth branchial arch) become the aortic bodies capable of sensing changes in oxygen content of the blood and primarily involved in regulating oxygen transport capacity through erythropoiesis and changes in blood volume.
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Affiliation(s)
- William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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McAneney J, Reid SG. Chronic hypoxia attenuates central respiratory-related pH/CO2 chemosensitivity in the cane toad. Respir Physiol Neurobiol 2007; 156:266-75. [PMID: 17140861 DOI: 10.1016/j.resp.2006.10.002] [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: 06/06/2006] [Revised: 10/18/2006] [Accepted: 10/19/2006] [Indexed: 11/22/2022]
Abstract
This study examined the effects of chronic hypoxia (CH) and mid-brain transection on central respiratory-related pH/CO(2) chemosensitivity in cane toads (Bufo marinus). Toads were exposed to 10 days of CH (10% O(2)) following which in vitro brainstem-spinal cord preparations, with the mid-brain attached, were used to examine central pH/CO(2) chemosensitivity. A reduction in artificial cerebral spinal fluid (aCSF) pH increased fictive breathing frequency (fR) and total fictive ventilation. CH reduced fictive fR and total fictive ventilation, compared to controls. Mid-brain transection caused an increase in fictive fR, at the lower aCSF pH levels, in both control and CH preparations. In the CH preparations, mid-brain transection restored fictive breathing to control levels. In both groups, mid-brain transection eliminated fictive breath clustering. The data indicate that CH attenuates central pH/CO(2)-sensitive fictive breathing but a mid-brain transection in the middle of the optic lobes abolishes this attenuation. The results suggest that CH induces inhibition of central pH/CO(2) chemoreceptor function via descending inputs from the mid-brain region.
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Affiliation(s)
- Jessica McAneney
- Centre for the Neurobiology of Stress, Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4 Canada
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Gilmour KM, Euverman RM, Esbaugh AJ, Kenney L, Chew SF, Ip YK, Perry SF. Mechanisms of acid–base regulation in the African lungfishProtopterus annectens. J Exp Biol 2007; 210:1944-59. [PMID: 17515420 DOI: 10.1242/jeb.02776] [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
SUMMARYAfrican lungfish Protopterus annectens utilized both respiratory and metabolic compensation to restore arterial pH to control levels following the imposition of a metabolic acidosis or alkalosis. Acid infusion (3 mmol kg–1 NH4Cl) to lower arterial pH by 0.24 units increased both pulmonary (by 1.8-fold) and branchial (by 1.7-fold) ventilation frequencies significantly, contributing to 4.8-fold and 1.9-fold increases in,respectively, aerial and aquatic CO2 excretion. This respiratory compensation appeared to be the main mechanism behind the restoration of arterial pH, because even though net acid excretion(JnetH+) increased following acid infusion in 7 of 11 fish, the mean increase in net acid excretion, 184.5±118.5μmol H+ kg–1 h–1 (mean± s.e.m., N=11), was not significantly different from zero. Base infusion (3 mmol kg–1 NaHCO3) to increase arterial pH by 0.29 units halved branchial ventilation frequency, although pulmonary ventilation frequency was unaffected. Correspondingly, aquatic CO2 excretion also fell significantly (by 3.7-fold) while aerial CO2 excretion was unaffected. Metabolic compensation consisting of negative net acid excretion (net base excretion) accompanied this respiratory compensation, with JnetH+ decreasing from 88.5±75.6 to –337.9±199.4 μmol H+kg–1 h–1 (N=8). Partitioning of net acid excretion into renal and extra-renal (assumed to be branchial and/or cutaneous) components revealed that under control conditions, net acid excretion occurred primarily by extra-renal routes. Finally, several genes that are involved in the exchange of acid–base equivalents between the animal and its environment (carbonic anhydrase, V-type H+-ATPase and Na+/HCO –3 cotransporter) were cloned, and their branchial and renal mRNA expressions were examined prior to and following acid or base infusion. In no case was mRNA expression significantly altered by metabolic acid–base disturbance. These findings suggest that lungfish, like tetrapods, alter ventilation to compensate for metabolic acid–base disturbances, a mechanism that is not employed by water-breathing fish. Like fish and amphibians, however, extra-renal routes play a key role in metabolic compensation.
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Affiliation(s)
- K M Gilmour
- Department of Biology and Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, ON, Canada.
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Amin-Naves J, Giusti H, Hoffmann A, Glass ML. Central ventilatory control in the South American lungfish, Lepidosiren paradoxa: contributions of pH and CO(2). J Comp Physiol B 2007; 177:529-34. [PMID: 17429654 DOI: 10.1007/s00360-007-0151-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 01/29/2007] [Accepted: 02/12/2007] [Indexed: 10/23/2022]
Abstract
Lungfish represent a probable sister group to the land vertebrates. Lungfish and tetrapods share features of respiratory control, including central, peripheral and intrapulmonary CO(2) receptors. We investigated whether or not central chemoreceptors in the lungfish, L. paradoxa, are stimulated by CO(2) and/or pH. Ventilation was measured by pneumotachography for diving animals. The fourth cerebral ventricle was equipped with two catheters for superfusion. Initially, two control groups were compared: (1) catheterized animals with no superfusion and (2) animals superfused with mock CSF solutions at pH = 7.45; PCO(2) = 21 mmHg. The two groups had virtually the same ventilation of about 40 ml BTPS kg(-1) h(-1) (P > 0.05). Next, PCO(2) was increased from 21 to 42 mmHg, while pH(CSF) was kept at 7.45, which increased ventilation from 40 to 75 ml BTPS kg(-1) h(-1). Conversely, a decrease of pH(CSF) from 7.45 to 7.20 (PCO(2) = 21 mmHg) increased ventilation to 111 ml BTPS kg(-1) h(-1). Further decreases of pH(CSF) had little effect on ventilation, and the combination of pH(CSF) = 7.10 and PCO(2) = 42 mmHg reduced ventilation to 63 ml BTPS kg(-1) h(-1).
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Affiliation(s)
- J Amin-Naves
- Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
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Dodd GAA, Scott GR, Milsom WK. Ventilatory roll off during sustained hypercapnia is gender specific in pekin ducks. Respir Physiol Neurobiol 2007; 156:47-60. [PMID: 17018266 DOI: 10.1016/j.resp.2006.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 06/29/2006] [Accepted: 07/12/2006] [Indexed: 10/24/2022]
Abstract
The objective of the present study was to examine the relative roles of peripheral versus central mechanisms in producing ventilatory adjustments in pekin ducks during prolonged (5 h) hypercapnia (5% inspired CO2), and to determine whether these adjustments differed between male and female ducks. After 20 min of CO2 exposure, intact ducks increased total ventilation (VE) 2.5-3-fold above control values, due to large increases (approximately 200%) in tidal volume (VT) and slightly smaller increases (approximately 140%) in breathing frequency (fR). This response was accompanied by respiratory acidosis (pHa fell from approximately 7.46 to approximately 7.41) and hypercapnia (PaCO2 increased from approximately 35 to approximately 40 Torr). In males, VE fell progressively thereafter due exclusively to a fall in fR, in parallel with a rapid partial recovery of pH (to 7.44) while PaCO2 continued to climb (to approximately 42 Torr). In females, VE remained elevated during hypercapnia, and no pH recovery occurred. This suggests that a respiratory decline resulting from acid-base compensation (probably due to HCO3- mobilization) occurred in males but not in females. Bicarbonate mobilization, and thus pH compensation, may have been reduced in females due to the CaCO3 requirements of eggshell formation. In males, the acute ventilatory response was reduced slightly by denervation of the carotid bodies or intrapulmonary chemoreceptors, but there was no effect of denervation of either receptor group on the responses to prolonged CO2. We conclude that pH compensation triggered by constant or increasing PaCO2, acting at central chemoreceptors, likely mediates the respiratory adjustments seen in male pekin ducks during hypercapnia. Furthermore, we suggest that this ventilatory response be considered a gender-specific hypercapnic ventilatory roll off, in the context of the various time domains of the hypercapnic ventilatory response.
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Affiliation(s)
- Graham A A Dodd
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Gheshmy A, Anari A, Besada D, Reid SG. Afferent input modulates the chronic hypercapnia-induced increase in respiratory-related central pH/CO2 chemosensitivity in the cane toad (Bufo marinus). J Exp Biol 2007; 210:227-37. [PMID: 17210960 DOI: 10.1242/jeb.02606] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The goal of this study was to examine the role of respiratory-related afferent input on the chronic hypercapnia (CHC)-induced increase in central respiratory-related pH/CO2 chemosensitivity in cane toads (Bufo marinus). Toads were exposed to CHC (3.5% CO2) for 10 days, following which in vitro brainstem-spinal cord preparations were used to assess central respiratory-related pH/CO2 chemosensitivity. Motor output from the vagus nerve root was used as an index of breathing (fictive breathing). Olfactory denervation (OD), prior to exposure to CHC, was used to remove the influence of CO2-sensitive olfactory chemoreceptors, which inhibit breathing. Exposure to chronic hyperoxic hypercapnia (CHH) was used to reduce the level of arterial chemoreceptor input compared with CHC alone. In vivo experiments examined the effects of CHC, CHH and OD on the acute hypercapnic ventilatory response of intact animals. In vitro, a reduction in artifical cerebral spinal fluid (aCSF) pH increased fictive breathing in preparations taken from control and CHC animals. CHC caused an increase in fictive breathing compared with controls. OD and CHH abolished the CHC-induced augmentation of fictive breathing. In vivo, CHC did not cause an augmentation of the acute hypercapnic ventilatory response. CHH reduced the in vivo acute hypercapnic ventilatory response compared with animals exposed to CHC. In vivo, OD reduced breathing frequency and increased breath amplitude in both control and CHC animals. The results suggest that afferent input from olfactory and arterial chemoreceptors, during CHC, is involved in triggering the CHC-induced increase in central respiratory-related pH/CO2 chemosensitivity.
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Affiliation(s)
- Afshan Gheshmy
- Centre for the Neurobiology of Stress, Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
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Amin-Naves J, Giusti H, Hoffmann A, Glass ML. Components to the acid–base related ventilatory drives in the South American lungfish Lepidosiren paradoxa. Respir Physiol Neurobiol 2007; 155:35-40. [PMID: 16713402 DOI: 10.1016/j.resp.2006.03.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 02/24/2006] [Accepted: 03/10/2006] [Indexed: 11/21/2022]
Abstract
Lungfish are closely related to terrestrial vertebrates (tetrapoda). Like tetrapods, the South American lungfish (Lepidosiren paradoxa) has central chemoreceptors involved in regulation of acid-base status. However, no data were available on peripheral CO(2)/[H(+)] receptors. Therefore, we tested the hypothesis that such receptors exist by measuring the ventilatory responses during a 5h exposure to combined aquatic/gas phase hypercarbia 7% (approximately 49 mmHg). Normocarbic control ventilation was 22 ml BTPS kg(-1)h(-1), and hypercarbia increased ventilation to 175 ml BTPS kg(-1)h(-1) at 5h. This procedure was repeated with the modification that normocarbic mock CSF (pH 7.45; P(CO2) = 20.7 mmHg) was applied to superfuse the cerebral ventricular system during the last 2h of the experiment. This served to eliminate the hypercarbic stimulus to the central chemoreceptors, while possible responses from peripheral chemoreceptors would remain intact. Peripheral receptors were detected, since ventilation became reduced to 62 ml BTPS kg(-1)h(-1) (P<0.05), which exceeds the initial normocarbic control ventilation (P<0.05). Based on this, the peripheral contribution accounted for 20% of the total response to hypercarbia, similar to the contribution of these receptors in man.
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Affiliation(s)
- J Amin-Naves
- Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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50
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Gravel J, Brocard F, Gariépy JF, Lund JP, Dubuc R. Modulation of respiratory activity by locomotion in lampreys. Neuroscience 2006; 144:1120-32. [PMID: 17137720 DOI: 10.1016/j.neuroscience.2006.10.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Revised: 10/10/2006] [Accepted: 10/10/2006] [Indexed: 11/25/2022]
Abstract
In vertebrates, locomotion is associated with changes in respiratory activity, but the neural mechanisms by which this occurs remain unknown. We began examining this in lampreys using a semi-intact preparation of young adult Petromyzon marinus, in which respiratory and locomotor behaviors can be recorded simultaneously with the activity of the underlying neural control systems. Spontaneous fictive respiration was recorded with suction electrodes positioned over the glossopharyngeal or the rostral vagal motor nucleus. In this preparation, locomotor activity, characterized by symmetrical tail movements (electromyogram recordings), was evoked by mechanical stimulation of the skin. During locomotion, the mean respiratory frequency and the mean area of the motor bursts were significantly increased (81.6+/-28.6% and 62.8+/-25.4%, respectively; P<0.05). The frequency returned to normal 92+/-51 s after the end of locomotion. There were fluctuations in the instantaneous respiratory and locomotor frequencies that were rhythmical but antiphasic for the two rhythmic activities. The changes in respiratory activity were also examined during bouts of locomotion occurring spontaneously, and it was found that a modification in respiratory activity preceded the onset of spontaneous locomotion by 3.5+/-2.6 s. This suggests that the early respiratory changes are anticipatory and are not caused by feedback generated by locomotion. The increase in respiratory frequency during locomotion induced by sensory stimulation persisted after removal of the mesencephalon. When both the mesencephalon and spinal cord were removed, resulting in the isolation of the rhombencephalon, changes in the respiratory activity were also present following skin stimulations that would have normally induced locomotion. Altogether, the results suggest that respiratory changes are programmed to adjust ventilation prior to motor activity, and that a central rhombencephalic mechanism is involved.
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Affiliation(s)
- J Gravel
- Département de Physiologie, Université de Montréal, Casier Postal 6128, Succursale Centre-ville, Montréal, Québec, Canada H3C 3J7
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