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Belt-and-Suspenders as a Biological Design Principle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 605:99-103. [DOI: 10.1007/978-0-387-73693-8_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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52
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Fournier S, Allard M, Roussin S, Kinkead R. Developmental changes in central O2 chemoreflex in Rana catesbeiana: the role of noradrenergic modulation. ACTA ACUST UNITED AC 2007; 210:3015-26. [PMID: 17704076 DOI: 10.1242/jeb.005983] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The in vitro brainstem preparation from Rana catesbeiana shows a functional central O(2) chemoreflex. Acute brainstem exposure to hypoxic superfusate elicits lung burst frequency responses that change over the course of development. Based on studies suggesting that brainstem noradrenergic neurons are involved in this reflex, we tested the following two hypotheses in vitro: (1) activation of adrenoceptors is necessary for the expression of the fictive lung ventilation response to hypoxia, and (2) changes in fast, Cl(-)-dependent neurotransmission (GABA/glycine) contribute to developmental changes in noradrenergic modulation. Experiments were performed on preparations from pre-metamorphics tadpoles (TK stages V-XIII) and adult bullfrogs. Acute exposure to hypoxic superfusate (98% N(2), 2% CO(2)) increased fictive lung ventilation frequency in the pre-metamorphic group, whereas a decrease was observed in adults. Buccal burst frequency was unchanged by hypoxia. Noradrenaline (NA; 5 micromol l(-1)) bath application mimicked both fictive breathing responses and application of the alpha(1)-antagonist prazosine (0.5 micromol l(-1)) blocked the lung burst response to hypoxia in both groups. Blocking GABA(A)/glycine receptors with a bicuculine/strychnine mixture (1.25 micromol l(-1)/1.5 micromol l(-1), respectively) or activation of GABA(B) pre-synaptic autoreceptors with baclofen (0.5 micromol l(-1)) prevented the lung burst response to hypoxia and to the alpha(1)-agonist phenylephrine (25 micromol l(-1)) in both stage groups. We conclude that NA modulation contributes to the central O(2) chemoreflex in bullfrog, which acts via GABA/glycine pathways. These data suggest that maturation of GABA/glycine neurotransmission contributes to the developmental changes in this chemoreflex.
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Affiliation(s)
- Stéphanie Fournier
- Department of Pediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec City, QC, Canada
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53
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Mutolo D, Bongianni F, Einum J, Dubuc R, Pantaleo T. Opioid-induced depression in the lamprey respiratory network. Neuroscience 2007; 150:720-9. [PMID: 17949922 DOI: 10.1016/j.neuroscience.2007.09.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 08/20/2007] [Accepted: 09/18/2007] [Indexed: 11/24/2022]
Abstract
The role of opioid receptors in modulating respiratory activity was investigated in in vitro brainstem preparations of adult lampreys by bath application of agonists and antagonists. The vagal motor output was used to monitor respiratory activity. Neuronal recordings were also performed to characterize the rostrolateral trigeminal region that has been suggested to be critical for respiratory rhythmogenesis. Microinjections of the micro-opioid receptor agonist [d-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) were also made into this region and at different locations within the brainstem. Bath application of DAMGO (0.5-2 microM) caused marked decreases in respiratory frequency up to complete apnea. Bath application of the delta-opioid receptor agonist [d-Pen(2,5)]-enkephalin (DPDPE) at 10-40 microM induced less pronounced depressant respiratory effects, while no changes in respiratory activity were induced by the kappa-opioid receptor agonist trans-(1S,2S)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide (U50488) at 10-40 microM. Bath application of the opioid receptor antagonists naloxone and naltrindole did not affect baseline respiratory activity, but prevented agonist-induced effects. DAMGO microinjections (1 mM; 0.5-1 nl) at sites rostrolateral to the trigeminal motor nucleus, where respiration-related neuronal activity was recorded, abolished the respiratory rhythm. The results show that opioids may have an important role in the lamprey respiratory network and that micro-opioid receptor activation is the most effective in causing respiratory depression. They also indicate that endogenous opioids are not required for the generation of baseline respiratory activity. Apneic responses induced by DAMGO microinjections support the hypothesis that a specific opioid-sensitive region rostrolateral to the trigeminal motor nucleus, that we have termed the paratrigeminal respiratory group (pTRG), likely has a pivotal role in respiratory rhythmogenesis. Since the lamprey diverged from the main vertebrate line around 450 million years ago, our results also imply that the inhibitory role of opioids on respiration is present at an early stage of vertebrate evolution.
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Affiliation(s)
- D Mutolo
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy.
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54
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Alonso JF, Mañanas MA, Hoyer D, Topor ZL, Bruce EN. Evaluation of Respiratory Muscles Activity by Means of Cross Mutual Information Function at Different Levels of Ventilatory Effort. IEEE Trans Biomed Eng 2007; 54:1573-82. [PMID: 17867349 DOI: 10.1109/tbme.2007.893494] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Analysis of respiratory muscles activity is an effective technique for the study of pulmonary diseases such as obstructive sleep apnea syndrome (OSAS). Respiratory diseases, especially those associated with changes in the mechanical properties of the respiratory apparatus, are often associated with disruptions of the normally highly coordinated contractions of respiratory muscles. Due to the complexity of the respiratory control, the assessment of OSAS related dysfunctions by linear methods are not sufficient. Therefore, the objective of this study was the detection of diagnostically relevant nonlinear complex respiratory mechanisms. Two aims of this work were: (1) to assess coordination of respiratory muscles contractions through evaluation of interactions between respiratory signals and myographic signals through nonlinear analysis by means of cross mutual information function (CMIF); (2) to differentiate between functioning of respiratory muscles in patients with OSAS and in normal subjects. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from three respiratory muscles: genioglossus, sternomastoid and diaphragm. Inspiratory pressure and flow were also acquired. All signals were measured in eight patients with OSAS and eight healthy subjects during an increased respiratory effort while awake. Several variables were defined and calculated from CMIF in order to describe correlation between signals. The results indicate different nonlinear couplings of respiratory muscles in both populations. This effect is progressively more evident at higher levels of respiratory effort.
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Affiliation(s)
- Joan Francesc Alonso
- Department of Automatic Control, Biomedical Engineering Research Center, Technical University of Catalonia (UPC), 5th Pau Gargalo St., E-08028 Barcelona, Spain.
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55
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Martel B, Guimond JC, Gariépy JF, Gravel J, Auclair F, Kolta A, Lund JP, Dubuc R. Respiratory rhythms generated in the lamprey rhombencephalon. Neuroscience 2007; 148:279-93. [PMID: 17618060 DOI: 10.1016/j.neuroscience.2007.05.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Revised: 05/22/2007] [Accepted: 05/24/2007] [Indexed: 10/23/2022]
Abstract
Brainstem networks generating the respiratory rhythm in lampreys are still not fully characterized. In this study, we described the patterns of respiratory activities and we identified the general location of underlying neural networks. In a semi-intact preparation including the brain and gills, rhythmic discharges were recorded bilaterally with surface electrodes placed over the vagal motoneurons. The main respiratory output driving rhythmic gill movements consisted of short bursts (40.9+/-15.6 ms) of discharge occurring at a frequency of 1.0+/-0.3 Hz. This fast pattern was interrupted by long bursts (506.3+/-174.6 ms) recurring with an average period of 37.4+/-24.9 s. After isolating the brainstem by cutting all cranial nerves, the frequency of the short respiratory bursts did not change significantly, but the slow pattern was less frequent. Local injections of a glutamate agonist (AMPA) and antagonists (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or D,L-amino-5-phosphonopentanoic acid (AP5)) were made over different brainstem regions to influence respiratory output. The results were similar in the semi-intact and isolated-brainstem preparations. Unilateral injection of AP5 or CNQX over a rostral rhombencephalic region, lateral to the rostral pole of the trigeminal motor nucleus, decreased the frequency of the fast respiratory rhythm bilaterally or stopped it altogether. Injection of AMPA at the same site increased the rate of the fast respiratory rhythm and decreased the frequency of the slow pattern. The activity recorded in this area was synchronous with that recorded over the vagal motoneurons. After a complete transverse lesion of the brainstem caudal to the trigeminal motor nucleus, the fast rhythm was confined to the rostral area, while only the slow activity persisted in the vagal motoneurons. Our results support the hypothesis that normal breathing depends on the activity of neurons located in the rostral rhombencephalon in lampreys, whereas the caudal rhombencephalon generates the slow pattern.
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Affiliation(s)
- B Martel
- Centre de Recherche en Sciences Neurologiques, Université de Montréal, Casier Postal 6128, Succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7
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56
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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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57
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Fournier S, Kinkead R. Noradrenergic modulation of respiratory motor output during tadpole development: Role of alpha-adrenoceptors. ACTA ACUST UNITED AC 2006; 209:3685-94. [PMID: 16943508 DOI: 10.1242/jeb.02418] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Noradrenaline (NA) is an important modulator of respiratory activity. Results from in vitro studies using immature rodents suggest that the effects exerted by NA change during development, but these investigations have been limited to neonatal stages. To address this issue, we used in vitro brainstem preparations of an ectotherm, Rana catesbeiana, at three developmental stages: pre-metamorphic tadpoles, metamorphic tadpoles and fully mature adult bullfrogs. We first compared the effects of NA bath application (0.02-10 micromol l(-1)) on brainstem preparations from both pre-metamorphic (Taylor-Köllros stages VII-XI) and metamorphic tadpoles (TK stages XVIII-XXIII) and adult frogs. The fictive lung ventilation frequency response to NA application was both dose- and stage-dependent. Although no net change was observed in the pre-metamorphic group, NA application decreased fictive lung burst frequency in preparations from more mature animals. These effects were attenuated by application of alpha-adrenoceptor antagonists. Conversely, NA application elicited dose- and stage-dependent increases in fictive buccal ventilation frequency. We then assessed the contribution of alpha-adrenoceptors towards these responses by applying specific agonists (alpha1: phenylephrine; alpha2: clonidine; concentration range from 10 to 200 micromol l(-1) for both). Of the two agonists used, only phenylephrine application consistently mimicked the lung burst frequency response observed during NA application in each stage group. However, both agonists decreased buccal burst frequency, thus suggesting that other (beta) adrenoceptor types mediate this response. We conclude that modulation of both buccal and lung-related motor outputs change during development. NA modulation affects both types of respiratory activities in a distinct fashion, owing to the different adrenoceptor type involved.
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Affiliation(s)
- Stéphanie Fournier
- Department of Pediatrics, Université Laval, Centre de Recherche du Centre Hospitalier Universitaire de Québec, 10 rue de l'Espinay, Québec City, QC G1L 3L5, Canada
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58
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Abstract
This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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59
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Brainerd EL, Owerkowicz T. Functional morphology and evolution of aspiration breathing in tetrapods. Respir Physiol Neurobiol 2006; 154:73-88. [PMID: 16861059 DOI: 10.1016/j.resp.2006.06.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Revised: 06/08/2006] [Accepted: 06/12/2006] [Indexed: 11/28/2022]
Abstract
In the evolution of aspiration breathing, the responsibility for lung ventilation gradually shifted from the hyobranchial to the axial musculoskeletal system, with axial muscles taking over exhalation first, at the base of Tetrapoda, and then inhalation as well at the base of Amniota. This shift from hyobranchial to axial breathing freed the tongue and head to adapt to more diverse feeding styles, but generated a mechanical conflict between costal ventilation and high-speed locomotion. Some "lizards" (non-serpentine squamates) have been shown to circumvent this speed-dependent axial constraint with accessory gular pumping during locomotion, and here we present a new survey of gular pumping behavior in the tuatara and 40 lizard species. We observed gular pumping behavior in 32 of the 40 lizards and in the tuatara, indicating that the ability to inflate the lungs by gular pumping is a shared-derived character for Lepidosauria. Gular pump breathing in lepidosaurs may be homologous with buccal pumping in amphibians, but non-ventilatory buccal oscillation and gular flutter have persisted throughout amniote evolution and gular pumping may have evolved independently by modification of buccal oscillation. In addition to gular pumping in some lizards, three other innovations have evolved repeatedly in the major amniote clades to circumvent the speed-dependent axial constraint: accessory inspiratory muscles (mammals, crocodylians and turtles), changing locomotor posture (mammals and birds) and respiratory-locomotor phase coupling to reduce the mechanical conflict between aspiration breathing and locomotion (mammals and birds).
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Affiliation(s)
- Elizabeth L Brainerd
- Department of Ecology and Evolutionary Biology, Box G-B210, Brown University, Providence, RI 02912, USA.
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60
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Vasilakos K, Kimura N, Wilson RJA, Remmers JE. Lung and Buccal Ventilation in the Frog: Uncoupling Coupled Oscillators. Physiol Biochem Zool 2006; 79:1010-8. [PMID: 17041867 DOI: 10.1086/507655] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2006] [Indexed: 11/03/2022]
Abstract
The frog, with two distinct ventilatory acts, provides a useful model to investigate the prospective interaction of two oscillators in generating the respiratory rhythm. Building on evidence supporting the existence of separate oscillators generating buccal and lung ventilation, we have attempted to uncouple the two rhythms in the isolated brain stem preparation. Opioid preferentially inhibits the lung rhythm, suggesting an uncoupling of the lung from the buccal oscillator. Reduction of the superfusate chloride concentration alters both the buccal and the lung rhythms. Joint application of opioid and reduced-chloride superfusate leads to an increase in the variability of the buccal burst-to-lung burst intervals. This increase in variability suggests that chloride-mediated mechanisms are involved in coupling the buccal oscillator to the lung oscillator. Given the results from these interventions, we propose a simple schematic model of the frog respiratory rhythm generator, outlining the coupling of the lung and buccal oscillators.
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61
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Wysocki M, Fiamma MN, Straus C, Poon CS, Similowski T. Chaotic dynamics of resting ventilatory flow in humans assessed through noise titration. Respir Physiol Neurobiol 2006; 153:54-65. [PMID: 16303337 DOI: 10.1016/j.resp.2005.09.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Revised: 09/14/2005] [Accepted: 09/15/2005] [Indexed: 11/26/2022]
Abstract
The mammalian ventilatory behaviour exhibits nonlinear dynamics as reflected by certain nonlinearity or complexity indicators (e.g. correlation dimension, approximate entropy, Lyapunov exponents, etc.) but this is not sufficient to determine its possible chaotic nature. To address this, we applied the noise titration technique, previously shown to discern and quantify chaos in short and noisy time series, to ventilatory flow recordings obtained in quietly breathing normal humans. Nine subjects (8 men and 1 woman, 24-42 years) were studied during 15-min epochs of ventilatory steady-state (10.1+/-3.0 breaths/min, tidal volume 0.63+/-0.2 L). Noise titration applied to the unfiltered signals subsampled at 5 Hz detected nonlinearity in all cases (noise limit 20.2+/-12.5%). Noise limit values were weakly correlated to the correlation dimension and the largest Lyapunov exponent of the signals. This study shows that the noise titration approach evidences a chaotic dimension to the behavior of ventilatory flow over time in normal humans during tidal breathing.
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Affiliation(s)
- Marc Wysocki
- Hamilton Medical AG, Via Nova, CH-7403 Rhäzuns, Switzerland.
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62
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Gargaglioni LH, Milsom WK. Control of breathing in anuran amphibians. Comp Biochem Physiol A Mol Integr Physiol 2006; 147:665-684. [PMID: 16949847 DOI: 10.1016/j.cbpa.2006.06.040] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 06/21/2006] [Accepted: 06/24/2006] [Indexed: 11/27/2022]
Abstract
The primary role of the respiratory system is to ensure adequate tissue oxygenation, eliminate carbon dioxide and help to regulate acid-base status. To maintain this homeostasis, amphibians possess an array of receptors located at peripheral and central chemoreceptive sites that sense respiration-related variables in both internal and external environments. As in mammals, input from these receptors is integrated at central rhythmogenic and pattern-forming elements in the medulla in a manner that meets the demands determined by the environment within the constraints of the behavior and breathing pattern of the animal. Also as in mammals, while outputs from areas in the midbrain may modulate respiration directly, they do not play a significant role in the production of the normal respiratory rhythm. However, despite these similarities, the breathing patterns of the two classes are different: mammals maintain homeostasis of arterial blood gases through rhythmic and continuous breathing, whereas amphibians display an intermittent pattern of aerial respiration. While the latter is also often rhythmic, it allows a degree of fluctuation in key respiratory variables that has led some to suggest that control is not as tight in these animals. In this review we will focus specifically on recent advances in studies of the control of ventilation in anuran amphibians. This is the group of amphibians that has attracted the most recent attention from respiratory physiologists.
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Affiliation(s)
- Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, Sao Paulo State University-FCAV at Jaboticabal, SP, Brazil.
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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63
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Wilson RJA, Vasilakos K, Remmers JE. Phylogeny of vertebrate respiratory rhythm generators: the Oscillator Homology Hypothesis. Respir Physiol Neurobiol 2006; 154:47-60. [PMID: 16750658 DOI: 10.1016/j.resp.2006.04.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Revised: 04/11/2006] [Accepted: 04/11/2006] [Indexed: 11/30/2022]
Abstract
A revolution is underway in our understanding of respiratory rhythm generation in mammals. Until recently, a major focus of research within the field has centered around the question of locating and elucidating the mechanism of rhythmogenesis of a single respiratory neuronal oscillator which is reiterated bilaterally within the brainstem. Now it appears that each hemisection may contain at least two oscillators that interact to generate the respiratory rhythm in mammals. Comparative studies have hinted at the existence of multiple respiratory oscillators in non-mammalian vertebrates for some time, raising the possibility of homologous oscillators. Here, we consider available tools to identify neuronal oscillators and critically review the evidence for the importance and existence of multiple respiratory oscillators in vertebrates. First focusing on a comparison between frogs and mammals, we then evaluate the hypothesis that ventilatory oscillators in extant tetrapods evolved from ancestral oscillators present in fish (the Oscillator Homology Hypothesis). While supporting data are incomplete, the Oscillator Homology Hypothesis will likely serve as a useful framework to motivate further studies of respiratory rhythm generation in lower vertebrates.
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Affiliation(s)
- Richard J A Wilson
- Department of Physiology and Biophysics, University of Calgary, Calgary, Alta., Canada.
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64
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Forster HV. The parafacial respiratory group (pFRG)/pre-Botzinger complex (preBotC) is the primary site of respiratory rhythm generation in the mammal. J Appl Physiol (1985) 2006. [DOI: 10.1152/japplphysiol.00351.2006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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65
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Lalley PM. Opiate slowing of feline respiratory rhythm and effects on putative medullary phase-regulating neurons. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1387-96. [PMID: 16284086 DOI: 10.1152/ajpregu.00530.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Opiates have effects on respiratory neurons that depress tidal volume and air exchange, reduce chest wall compliance, and slow rhythm. The most dose-sensitive opioid effect is slowing of the respiratory rhythm through mechanisms that have not been thoroughly investigated. An in vivo dose-response analysis was performed on medullary respiratory neurons of adult cats to investigate two untested hypotheses related to mechanisms of opioid-mediated rhythm slowing: 1) Opiates suppress intrinsic conductances that limit discharge duration in medullary inspiratory and expiratory neurons, and 2) opiates delay the onset and lengthen the duration of discharges postsynaptically in phase-regulating postinspiratory and late-inspiratory neurons. In anesthetized and unanesthetized decerebrate cats, a threshold dose (3 μg/kg) of the μ-opioid receptor agonist fentanyl slowed respiratory rhythm by prolonging discharges of inspiratory and expiratory bulbospinal neurons. Additional doses (2–4 μg/kg) of fentanyl also lengthened the interburst silent periods in each type of neuron and delayed the rate of membrane depolarization to firing threshold without altering synaptic drive potential amplitude, input resistance, peak action potential frequency, action potential shape, or afterhyperpolarization. Fentanyl also prolonged discharges of postinspiratory and late-inspiratory neurons in doses that slowed the rhythm of inspiratory and expiratory neurons without altering peak membrane depolarization and hyperpolarization, input resistance, or action potential properties. The temporal changes evoked in the tested neurons can explain the slowing of network respiratory rhythm, but the lack of significant, direct opioid-mediated membrane effects suggests that actions emanating from other types of upstream bulbar respiratory neurons account for rhythm slowing.
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Affiliation(s)
- Peter M Lalley
- Dept. of Physiology, Medical Sciences Center, Univ. of Wisconsin, 1300 Univ. Ave., Madison, WI 53706, USA.
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66
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Feldman JL, Del Negro CA. Looking for inspiration: new perspectives on respiratory rhythm. Nat Rev Neurosci 2006; 7:232-42. [PMID: 16495944 PMCID: PMC2819067 DOI: 10.1038/nrn1871] [Citation(s) in RCA: 602] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recent experiments in vivo and in vitro have advanced our understanding of the sites and mechanisms involved in mammalian respiratory rhythm generation. Here we evaluate and interpret the new evidence for two separate brainstem respiratory oscillators and for the essential role of emergent network properties in rhythm generation. Lesion studies suggest that respiratory cell death might explain morbidity and mortality associated with neurodegenerative disorders and ageing.
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Affiliation(s)
- Jack L Feldman
- Department of Neurobiology, David Geffen School of Medicine at the University of California, Los Angeles, BOX 951763, Los Angeles, California 90095-1763, USA.
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67
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Feldman JL, Janczewski WA. Point:Counterpoint: The parafacial respiratory group (pFRG)/pre-Botzinger complex (preBotC) is the primary site of respiratory rhythm generation in the mammal. Point: the PFRG is the primary site of respiratory rhythm generation in the mammal. J Appl Physiol (1985) 2006; 100:2096-7; discussion 2097-8, 2103-8. [PMID: 16767809 DOI: 10.1152/japplphysiol.00119.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Jack L Feldman
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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68
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Affiliation(s)
- Patrice G Guyenet
- University of Virginia, Department of Pharmacology, Charlottesville, USA
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69
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Janczewski WA, Feldman JL. Distinct rhythm generators for inspiration and expiration in the juvenile rat. J Physiol 2005; 570:407-20. [PMID: 16293645 PMCID: PMC1464316 DOI: 10.1113/jphysiol.2005.098848] [Citation(s) in RCA: 308] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Inspiration and active expiration are commonly viewed as antagonistic phases of a unitary oscillator that generates respiratory rhythm. This view conflicts with observations we report here in juvenile rats, where by administration of fentanyl, a selective mu-opiate agonist, and induction of lung reflexes, we separately manipulated the frequency of inspirations and expirations. Moreover, completely transecting the brainstem at the caudal end of the facial nucleus abolished active expirations, while rhythmic inspirations continued. We hypothesize that inspiration and expiration are generated by coupled, anatomically separate rhythm generators, one generating active expiration located close to the facial nucleus in the region of the retrotrapezoid nucleus/parafacial respiratory group, the other generating inspiration located more caudally in the preBötzinger Complex.
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Affiliation(s)
- Wiktor A Janczewski
- Department of Neurobiology, David Geffen School of Medicine, Los Angeles, CA 90095-1763, USA.
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