1
|
Vincent SG, Fisher JT. In vivo cardiopulmonary impact of skeletal M 3Dq DREADD expression: a pilot study. J Comp Physiol B 2021; 191:1059-1070. [PMID: 34272586 PMCID: PMC8572194 DOI: 10.1007/s00360-021-01387-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 05/23/2021] [Accepted: 07/06/2021] [Indexed: 01/07/2023]
Abstract
The muscarinic M3 receptor (M3R) is implicated in cardiopulmonary control and many other peripheral physiologic functions. Previous observations report mortality in mice expressing a Gq-linked designer G-protein coupled receptor (Dq) selectively in striated muscle, while M3Dq DREADD (Designer Receptor Exclusively Activated by Designer Drug), selectively expressed in skeletal muscle (SKM) impacts glucose metabolism. We investigated whether activation of SKM M3Dq impacts cardiopulmonary function. Heart rate (HR), body temperature (Tb) and locomotor activity (ACT) were measured in 4 conscious, chronically instrumented M3Dq DREADD mice and 4 wildtype controls. Circadian values of HR, BT and ACT were not different between genotypes (p > 0.05). Activation of the M3Dq DREADD by clozapine N-oxide (CNO; 0.1 mg/kg) resulted in: a significant drop in heart rate, 2 h after injection, compared with a time-matched baseline control period from the same animals (460 ± 28 vs. 532 ± 6, p < 0.05), significantly lower ACT compared to the baseline control (p < 0.05) and reduced pulmonary minute ventilation compared to pre-CNO control (p < 0.05). M3Dq DREADD activation did not cause bronchoconstriction (separate protocol), however, there was a concomitant reduction in HR, Tb and ventilation, accompanied by cardiac arrhythmias. We speculate that reductions in Tb, HR and ventilation reflect a mechanistic link between SKM Gq signaling and the metabolic responses associated with the initiation of torpor. Supported by the Canadian Institutes of Health Research (CIHR MOP-81211).
Collapse
Affiliation(s)
- Sandra G. Vincent
- Department of Biomedical and Molecular Sciences and Division of Respirology, Department of Medicine, Queen’s University, Kingston, ON K7L 3N6 Canada
| | - John T. Fisher
- Department of Biomedical and Molecular Sciences and Division of Respirology, Department of Medicine, Queen’s University, Kingston, ON K7L 3N6 Canada
| |
Collapse
|
2
|
Moreira TS, Sobrinho CR, Falquetto B, Oliveira LM, Lima JD, Mulkey DK, Takakura AC. The retrotrapezoid nucleus and the neuromodulation of breathing. J Neurophysiol 2020; 125:699-719. [PMID: 33427575 DOI: 10.1152/jn.00497.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Breathing is regulated by a host of arousal and sleep-wake state-dependent neuromodulators to maintain respiratory homeostasis. Modulators such as acetylcholine, norepinephrine, histamine, serotonin (5-HT), adenosine triphosphate (ATP), substance P, somatostatin, bombesin, orexin, and leptin can serve complementary or off-setting functions depending on the target cell type and signaling mechanisms engaged. Abnormalities in any of these modulatory mechanisms can destabilize breathing, suggesting that modulatory mechanisms are not overly redundant but rather work in concert to maintain stable respiratory output. The present review focuses on the modulation of a specific cluster of neurons located in the ventral medullary surface, named retrotrapezoid nucleus, that are activated by changes in tissue CO2/H+ and regulate several aspects of breathing, including inspiration and active expiration.
Collapse
Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Cleyton R Sobrinho
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Barbara Falquetto
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Janayna D Lima
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| |
Collapse
|
3
|
Thomsen M, Sørensen G, Dencker D. Physiological roles of CNS muscarinic receptors gained from knockout mice. Neuropharmacology 2017; 136:411-420. [PMID: 28911965 DOI: 10.1016/j.neuropharm.2017.09.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 09/06/2017] [Accepted: 09/08/2017] [Indexed: 12/29/2022]
Abstract
Because the five muscarinic acetylcholine receptor subtypes have overlapping distributions in many CNS tissues, and because ligands with a high degree of selectivity for a given subtype long remained elusive, it has been difficult to determine the physiological functions of each receptor. Genetically engineered knockout mice, in which one or more muscarinic acetylcholine receptor subtype has been inactivated, have been instrumental in identifying muscarinic receptor functions in the CNS, at the neuronal, circuit, and behavioral level. These studies revealed important functions of muscarinic receptors modulating neuronal activity and neurotransmitter release in many brain regions, shaping neuronal plasticity, and affecting functions ranging from motor and sensory function to cognitive processes. As gene targeting technology evolves including the use of conditional, cell type specific strains, knockout mice are likely to continue to provide valuable insights into brain physiology and pathophysiology, and advance the development of new medications for a range of conditions such as Alzheimer's disease, Parkinson's disease, schizophrenia, and addictions, as well as non-opioid analgesics. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.
Collapse
Affiliation(s)
- Morgane Thomsen
- Laboratory of Neuropsychiatry, Psychiatric Center Copenhagen and University of Copenhagen, Denmark; Alcohol and Drug Abuse Research Center, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA.
| | - Gunnar Sørensen
- Alcohol and Drug Abuse Research Center, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA
| | - Ditte Dencker
- Laboratory of Neuropsychiatry, Psychiatric Center Copenhagen and University of Copenhagen, Denmark
| |
Collapse
|
4
|
Role of Astrocytes in Central Respiratory Chemoreception. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:109-145. [PMID: 27714687 DOI: 10.1007/978-3-319-40764-7_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Astrocytes perform various homeostatic functions in the nervous system beyond that of a supportive or metabolic role for neurons. A growing body of evidence indicates that astrocytes are crucial for central respiratory chemoreception. This review presents a classical overview of respiratory central chemoreception and the new evidence for astrocytes as brainstem sensors in the respiratory response to hypercapnia. We review properties of astrocytes for chemosensory function and for modulation of the respiratory network. We propose that astrocytes not only mediate between CO2/H+ levels and motor responses, but they also allow for two emergent functions: (1) Amplifying the responses of intrinsic chemosensitive neurons through feedforward signaling via gliotransmitters and; (2) Recruiting non-intrinsically chemosensitive cells thanks to volume spreading of signals (calcium waves and gliotransmitters) to regions distant from the CO2/H+ sensitive domains. Thus, astrocytes may both increase the intensity of the neuron responses at the chemosensitive sites and recruit of a greater number of respiratory neurons to participate in the response to hypercapnia.
Collapse
|
5
|
The effect of centrally injected CDP-choline on respiratory system; involvement of phospholipase to thromboxane signaling pathway. Respir Physiol Neurobiol 2014; 195:50-8. [PMID: 24560778 DOI: 10.1016/j.resp.2014.02.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 02/12/2014] [Accepted: 02/12/2014] [Indexed: 11/22/2022]
Abstract
CDP-choline is an endogenous metabolite in phosphatidylcholine biosynthesis. Exogenous administration of CDP-choline has been shown to affect brain metabolism and to exhibit cardiovascular, neuroendocrine neuroprotective actions. On the other hand, little is known regarding its respiratory actions and/or central mechanism of its respiratory effect. Therefore the current study was designed to investigate the possible effects of centrally injected CDP-choline on respiratory system and the mediation of the central cholinergic receptors and phospholipase to thromboxane signaling pathway on CDP-choline-induced respiratory effects in anaesthetized rats. Intracerebroventricularly (i.c.v.) administration of CDP-choline induced dose- and time-dependent increased respiratory rates, tidal volume and minute ventilation of male anaesthetized Spraque Dawley rats. İ.c.v. pretreatment with atropine failed to alter the hyperventilation responses to CDP-choline whereas mecamylamine, cholinergic nicotinic receptor antagonist, mepacrine, phospholipase A2 inhibitor, and neomycin phospholipase C inhibitor, blocked completely the hyperventilation induced by CDP-choline. In addition, central pretreatment with furegrelate, thromboxane A2 synthesis inhibitor, also partially blocked CDP-choline-evoked hyperventilation effects. These data show that centrally administered CDP-choline induces hyperventilation which is mediated by activation of central nicotinic receptors and phospholipase to thromboxane signaling pathway.
Collapse
|
6
|
Tadmouri A, Champagnat J, Morin-Surun M. Activation of microglia and astrocytes in the nucleus tractus solitarius during ventilatory acclimatization to 10% hypoxia in unanesthetized mice. J Neurosci Res 2014; 92:627-33. [DOI: 10.1002/jnr.23336] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 10/23/2013] [Accepted: 10/29/2013] [Indexed: 12/24/2022]
Affiliation(s)
- A. Tadmouri
- Neurobiologie Génétique et Intégrative, UPR 3294, Neurobiologie et Développement; Institut de Neurobiologie Alfred Fessard, CNRS; Gif sur Yvette France
| | - J. Champagnat
- Neurobiologie Génétique et Intégrative, UPR 3294, Neurobiologie et Développement; Institut de Neurobiologie Alfred Fessard, CNRS; Gif sur Yvette France
| | - M.P. Morin-Surun
- Neurobiologie Génétique et Intégrative, UPR 3294, Neurobiologie et Développement; Institut de Neurobiologie Alfred Fessard, CNRS; Gif sur Yvette France
| |
Collapse
|
7
|
Kimura S, Haji A. Pharmacological strategy for overcoming opioid-induced ventilatory disturbances. Eur J Pharmacol 2014; 725:87-90. [DOI: 10.1016/j.ejphar.2013.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 08/21/2013] [Indexed: 01/17/2023]
|
8
|
Effects of cholinesterase inhibitors and serotonin-1A receptor agonists on morphine-induced ventilatory depression and antinociception in rats. Eur J Pharmacol 2013; 703:33-41. [PMID: 23438874 DOI: 10.1016/j.ejphar.2013.02.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 02/01/2013] [Accepted: 02/07/2013] [Indexed: 11/24/2022]
Abstract
Ventilatory depression is a serious side-effect of opioid analgesics. Naloxone, an antagonist of opioid receptors, eliminates not only ventilatory depression but also analgesic effect of opioids. Pharmacological dissociation of adverse reactions from the main action is important clinically and basically. Cholinergic and serotonergic mechanisms are suggested to counteract the opioid-induced ventilatory disturbances, but their influence on analgesia is still controversial. The present study evaluated the effects of cholinesterase inhibitors and serotonin-1A (5-HT1A) receptor agonists on morphine (1.0mg/kg, i.v.)-induced ventilatory depression and analgesia in rats. In anesthetized animals, spontaneous ventilation and hind leg withdrawal reflexes against nociceptive thermal stimuli were measured simultaneously. Physostigmine (0.1 and 0.2mg/kg, i.v.) and donepezil (0.5 and 1.0mg/kg, i.v.) relieved the morphine-induced ventilatory depression and enhanced its antinociception. On the other hand, (±)-8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.03 and 0.1mg/kg, i.v.) and buspirone (0.1 and 0.3mg/kg, i.v.) did not influence antinociception of morphine while they restored the decreased ventilation. In unanesthetized animals, hypercapnic ventilatory response was measured by using whole-body plethysmography. Physostigmine (0.3mg/kg, i.p.), donepezil (1.0mg/kg, i.p.), 8-OH-DPAT (0.3mg/kg, i.p.) and buspirone (3.0mg/kg, i.p.) all recovered the morphine (10mg/kg, i.p.)-induced depression of hypercapnic ventilatory response. The present study suggests that activation of cholinergic or serotonergic (5-HT1A) mechanisms may be a useful therapeutic approach for morphine-induced ventilatory depression without loss of its analgesic action.
Collapse
|
9
|
M3-receptor activation counteracts opioid-mediated apneusis, but the apneusis per se is not necessarily related to an impaired M3 mechanism in rats. Life Sci 2011; 89:685-90. [DOI: 10.1016/j.lfs.2011.08.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 07/14/2011] [Accepted: 08/02/2011] [Indexed: 11/23/2022]
|
10
|
Pilarski JQ, Wakefield HE, Fuglevand AJ, Levine RB, Fregosi RF. Increased nicotinic receptor desensitization in hypoglossal motor neurons following chronic developmental nicotine exposure. J Neurophysiol 2011; 107:257-64. [PMID: 22013232 DOI: 10.1152/jn.00623.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) are expressed on hypoglossal motor neurons (XII MNs) that innervate muscles of the tongue. Activation of XII MN nAChRs evokes depolarizing currents, which are important for regulating the size and stiffness of the upper airway. Although data show that chronic developmental nicotine exposure (DNE) blunts cholinergic neurotransmission in the XII motor nucleus, it is unclear how nAChRs are involved. Therefore, XII MN nAChR desensitization and recovery were examined in tissues from DNE or control pups using a medullary slice preparation and tight-seal whole cell patch-clamp recordings. nAChR-mediated inward currents were evoked by brief pressure pulses of nicotine or the α4β2 nAChR agonist RJR-2403. We found that, regardless of treatment, activatable nAChRs underwent desensitization, but, following DNE, nAChRs exhibited increased desensitization and delayed recovery. Similar results were produced using RJR-2403, showing that DNE influences primarily the α4β2 nAChR subtype. These results show that while some nAChRs preserve their responsiveness to acute nicotine following DNE, they more readily desensitize and recover more slowly from the desensitized state. These data provide new evidence that chronic DNE modulates XII MN nAChR function, and suggests an explanation for the association between DNE and the incidence of central and obstructive apneas.
Collapse
Affiliation(s)
- Jason Q Pilarski
- Idaho State University, Department of Biological Sciences and Dental Sciences, 921 S. 8th Avenue, Stop 8007, Pocatello, Idaho 83209, USA.
| | | | | | | | | |
Collapse
|
11
|
Champagnat J, Morin-Surun MP, Fortin G, Thoby-Brisson M. Developmental basis of the rostro-caudal organization of the brainstem respiratory rhythm generator. Philos Trans R Soc Lond B Biol Sci 2009; 364:2469-76. [PMID: 19651648 DOI: 10.1098/rstb.2009.0090] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The Hox genetic network plays a key role in the anteroposterior patterning of the rhombencephalon at pre- and early-segmental stages of development of the neural tube. In the mouse, it controls development of the entire brainstem respiratory neuronal network, including the pons, the parafacial respiratory group (pFRG) and the pre-Bötzinger complex (preBötC). Inactivation of Krox20/Egr2 eliminates the pFRG activity, thereby causing life-threatening neonatal apnoeas alternating with respiration at low frequency. Another respiratory abnormality, the complete absence of breathing, is induced when neuronal synchronization fails to develop in the preBötC. The present paper summarizes data on a third type of respiratory deficits induced by altering Hox function at pontine levels. Inactivation of Hoxa2, the most rostrally expressed Hox gene in the hindbrain, disturbs embryonic development of the pons and alters neonatal inspiratory shaping without affecting respiratory frequency and apnoeas. The same result is obtained by the Phox2a(+/-) mutation modifying the number of petrosal chemoafferent neurons, by eliminating acetylcholinesterase and by altering Hox-dependent development of the pons with retinoic acid administration at embryonic day 7.5. In addition, embryos treated with retinoic acid provide a mouse model for hyperpnoeic episodic breathing, widely reported in pre-term neonates, young girls with Rett's syndrome, patients with Joubert syndrome and adults with Cheyne-Stokes respiration. We conclude that specific respiratory deficits in vivo are assignable to anteroposterior segments of the brainstem, suggesting that the adult respiratory neuronal network is functionally organized according to the rhombomeric, Hox-dependent segmentation of the brainstem in embryos.
Collapse
Affiliation(s)
- J Champagnat
- Centre de Recherche de Gif, UPR 2216 (Neurobiologie Génétique et Intégrative), IFR 2118 (Institut de Neurobiologie Alfred Fessard), CNRS, 91198 Gif-sur-Yvette, France.
| | | | | | | |
Collapse
|
12
|
Boudinot E, Champagnat J, Foutz AS. M(1)/M(3) and M(2)/M(4) muscarinic receptor double-knockout mice present distinct respiratory phenotypes. Respir Physiol Neurobiol 2007; 161:54-61. [PMID: 18206430 DOI: 10.1016/j.resp.2007.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 11/14/2007] [Accepted: 12/01/2007] [Indexed: 11/27/2022]
Abstract
We investigated the role of muscarinic acetylcholine receptors in the control of breathing. Baseline breathing at rest and ventilatory responses to brief exposures to hypoxia (10% O(2)) and hypercapnia (3% and 5% CO(2)), measured by whole-body plethysmography in partially restrained animals, were compared in mice lacking either M(1) and M(3) or M(2) and M(4) muscarinic receptors, and in wild-type matched controls. M(1/3)R double-knockout mice showed at rest an elevated ventilation (V (E)) due to a large (57%) increase in tidal volume (V(T)). Chemosensory ventilatory responses were unaltered. M(2/4)R double-knockout mice were agitated and showed elevated V (E) and breathing frequency (f(R)) at rest when partially restrained, but unaltered V (E) and low f(R) when recorded unrestrained. Chemosensory ventilatory responses were unaltered. The results suggest that M(1) and M(3) receptors are involved in the control of tidal volume, while M(2) and M(4) receptors may be involved in the control of breathing frequency at rest and response to stress.
Collapse
Affiliation(s)
- E Boudinot
- Neurobiologie Génétique et Intégrative, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 91190 Gif-sur-Yvette, France
| | | | | |
Collapse
|
13
|
Wu M, Kc P, Mack SO, Haxhiu MA. Ablation of vagal preganglionic neurons innervating the extra-thoracic trachea affects ventilatory responses to hypercapnia and hypoxia. Respir Physiol Neurobiol 2005; 152:36-50. [PMID: 16099224 DOI: 10.1016/j.resp.2005.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Revised: 07/01/2005] [Accepted: 07/04/2005] [Indexed: 10/25/2022]
Abstract
This study tested the hypothesis that during hypercapnia or hypoxia, airway-related vagal preganglionic neurons (AVPNs) of the nucleus ambiguus (NA) release acetylcholine (ACh), which in a paracrine fashion, activates ACh receptors expressed by inspiratory rhythm generating cells. AVPNs in the NA were ablated by injecting a saporin- (SA) cholera toxin b subunit (CTb-SA) conjugate into the extra-thoracic trachea (n=6). Control animals were injected with free CTb (n=6). In CTb treated rats, baseline ventilation and ventilatory responses to hypercapnia (5 and 12% CO(2) in O(2)) or hypoxia (8% O(2) in N(2)) were similar (p>0.05) prior to and 5 days after injection. CTb-SA injected rats maintained rhythmic breathing patterns 5 days post injection, however, tachypneic responses to hypercapnia or hypoxia were significantly reduced. The number of choline acetyltransferase (ChAT) immunoreactive cells in the NA was much lower (p<0.05) in CTb-SA rats as compared to animals receiving CTb only. These results suggest that AVPNs participate in the respiratory frequency response to hypercapnia or hypoxia.
Collapse
Affiliation(s)
- Mingfei Wu
- Specialized Neuroscience Research Program, Department of Physiology and Biophysics, Howard University College of Medicine, 520 'W' Street NW, Washington, DC 20059, USA
| | | | | | | |
Collapse
|
14
|
Wiemann M, Frede S, Bingmann D, Kiwull P, Kiwull-Schöne H. Sodium/Proton Exchanger 3 in the Medulla Oblongata and Set Point of Breathing Control. Am J Respir Crit Care Med 2005; 172:244-9. [PMID: 15947281 DOI: 10.1164/rccm.200411-1567oc] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE In vivo inhibition of the sodium/proton exchanger 3 (NHE3) in chemosensitive neurons of the ventrolateral brainstem augments central respiratory drive in anesthetized rabbits. OBJECTIVES To further explore the possible role of this exchanger for the control of breathing, we examined the individual relationship between brainstem NHE3 abundance and ventilation in rabbits during wakefulness. METHODS In 32 adult male rabbits on standard nutritional alkali load, alveolar ventilation, metabolic CO2 production, and blood gases were determined, together with arterial and urinary acid-base status and renal base control functions. Expression of NHE3 in brainstem tissue from the obex region was determined by quantitative real-time reverse-transcription polymerase chain reaction analysis. MEASUREMENTS AND MAIN RESULTS Regarding the distribution above and below the median, we classified high and low brainstem NHE3 animals, expressing a mean (+/- SEM) NHE3 mRNA of 2.08 +/- 0.28 and 0.72 +/- 0.06 fg cDNA/mg RNA, respectively. Alveolar ventilation of high brainstem NHE3 animals was lower than that of low brainstem NHE3 animals (715 +/- 36 vs. 919 +/- 41 ml . minute(-1); p < 0.01), a finding also reflected by a marked difference in Pa(CO2) (5.24 +/- 0.16 vs. 4.44 +/- 0.15 kPa; p < 0.01). Among possible secondary factors, CO2 production, systemic base excess, and fractional renal base reabsorption were not found to be different. CONCLUSIONS We conclude that the level of brainstem NHE3 expression-most likely via intracellular pH modulation-contributes to the individual control of breathing and Pa(CO2) in conscious rabbits by adjusting the set point and the loop gain of the system.
Collapse
Affiliation(s)
- Martin Wiemann
- Department of Physiology, University of Duisburg-Essen, 45122 Essen, Germany.
| | | | | | | | | |
Collapse
|
15
|
Kubin L, Fenik V. Pontine cholinergic mechanisms and their impact on respiratory regulation. Respir Physiol Neurobiol 2004; 143:235-49. [PMID: 15519558 DOI: 10.1016/j.resp.2004.04.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2004] [Indexed: 10/26/2022]
Abstract
Activation of pontomedullary cholinergic neurons may directly and indirectly cause depression of respiratory motoneuronal activity, activation of respiratory premotor neurons and acceleration of the respiratory rate during REM sleep, as well as activation of breathing during active wakefulness. These effects may be mediated by distinct subpopulations of cholinergic neurons. The relative inactivity of cholinergic neurons during slow-wave sleep also may contribute to the depressant effects of this state on breathing. Cholinergic muscarinic and nicotinic receptors are expressed in central respiratory neurons and motoneurons, thus allowing cholinergic neurons to act on the respiratory system directly. Additional effects of cholinergic activation are mediated indirectly by noradrenergic, serotonergic and other neurons of the reticular formation. Excitatory and suppressant respiratory effects with features of natural states of REM sleep or active wakefulness can be elicited in urethane-anesthetized rats by pontine microinjections of the cholinergic agonist, carbachol. Carbachol models help elucidate the neural basis of respiratory disorders associated with central cholinergic activation.
Collapse
Affiliation(s)
- Leszek Kubin
- Department of Animal Biology 209E/VET, School of Veterinary Medicine and Center for Sleep and Respiratory Neurobiology, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6046, USA.
| | | |
Collapse
|
16
|
Boudinot E, Emery MJ, Mouisel E, Chatonnet A, Champagnat J, Escourrou P, Foutz AS. Increased ventilation and CO2 chemosensitivity in acetylcholinesterase knockout mice. Respir Physiol Neurobiol 2004; 140:231-41. [PMID: 15186785 DOI: 10.1016/j.resp.2004.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2004] [Indexed: 11/17/2022]
Abstract
To investigate the effects of a permanent excess of acetylcholine (AChE) on respiration, breathing and chemosensitivity were analyzed from birth to adulthood in mice lacking the AChE gene (AChE-/-), in heterozygotes, and in control wild-type (AChE+/+) littermates. Breathing at rest and ventilatory responses to brief exposures to hypoxia (10% O2) and hypercapnia (3-5% CO2) were measured by whole-body plethysmography. At rest AChE-/- mice show larger tidal volumes (VT, + 96% in adults), overall ventilation (VE, + 70%), and mean inspiratory flow (+270%) than wild-type mice, with no change in breathing frequency (fR). AChE-/- mice have a slightly blunted response to hypoxia, but increased VE and fR responses to hypercapnia. Heterozygous animals present no consistent alterations of breathing at rest and chemosensitivity is normal. Adult AChE-/- mice have an increased VE/VO2 and a marginally higher normalized VO2. The results suggest that the hyperventilation and altered chemosensitivity in AChE-/- mice largely reflect alterations of central respiratory control.
Collapse
Affiliation(s)
- E Boudinot
- Neurobiologie Génétique et Intégrative, Institut de Neurobiologie Alfred Fessard, C.N.R.S., 91190 Gif-sur-Yvette, France
| | | | | | | | | | | | | |
Collapse
|