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Frazure M, Greene CL, Iceman KE, Howland DR, Pitts T. Dysphagia as a Missing Link Between Post-surgical- and Opioid-Related Pneumonia. Lung 2024; 202:179-187. [PMID: 38538927 DOI: 10.1007/s00408-024-00672-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 01/21/2024] [Indexed: 04/07/2024]
Abstract
PURPOSE Postoperative pneumonia remains a common complication of surgery, despite increased attention. The purpose of our study was to determine the effects of routine surgery and post-surgical opioid administration on airway protection risk. METHODS Eight healthy adult cats were evaluated to determine changes in airway protection status and for evidence of dysphagia in two experiments. (1) In four female cats, airway protection status was tracked following routine abdominal surgery (spay surgery) plus low-dose opioid administration (buprenorphine 0.015 mg/kg, IM, q8-12 h; n = 5). (2) Using a cross-over design, four naive cats (2 male, 2 female) were treated with moderate-dose (0.02 mg/kg) or high-dose (0.04 mg/kg) buprenorphine (IM, q8-12 h; n = 5). RESULTS Airway protection was significantly affected in both experiments, but the most severe deficits occurred post-surgically as 75% of the animals exhibited silent aspiration. CONCLUSION Oropharyngeal swallow is impaired by the partial mu-opioid receptor agonist buprenorphine, most remarkably in the postoperative setting. These findings have implications for the prevention and management of aspiration pneumonia in vulnerable populations.
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Affiliation(s)
- Michael Frazure
- Department of Physiology, School of Medicine, University of Louisville, Louisville, KY, USA
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, KY, USA
| | - Clinton L Greene
- Department of Speech Language and Hearing Sciences and Dalton Cardiovascular Center, University of Missouri, 701 S Fifth St, Columbia, MO, 65203, USA
| | - Kimberly E Iceman
- Department of Speech Language and Hearing Sciences and Dalton Cardiovascular Center, University of Missouri, 701 S Fifth St, Columbia, MO, 65203, USA
| | - Dena R Howland
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, KY, USA
| | - Teresa Pitts
- Department of Speech Language and Hearing Sciences and Dalton Cardiovascular Center, University of Missouri, 701 S Fifth St, Columbia, MO, 65203, USA.
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2
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Poliacek I, Martvon L, Simera M, Veternik M, Misek J, Cibulkova L, Iceman KE, Bolser DC, Pitts T. Cough and swallow after laparotomy in anesthetized cats. Respir Physiol Neurobiol 2024; 319:104179. [PMID: 37858661 DOI: 10.1016/j.resp.2023.104179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/02/2023] [Accepted: 10/14/2023] [Indexed: 10/21/2023]
Abstract
An anesthetized cat animal model was used to evaluate changes in cough and swallow after a small midline upper abdominal incision (laparotomy). Two additional conditions were tested: sealing the laparotomy with gentle suctioning via a small cannula, and subsequent closure of the abdominal wall with suture. These abdominal wall manipulations resulted in no changes in the cough reflex, but produced higher motor drive to pharyngeal musculature (thyropharyngeus and geniohyoid muscles) during swallow. Swallow-breathing coordination phase preference shifted towards swallow occurring more during the inspiratory phase. There were no significant changes in cough motor pattern, or cough and swallow number and temporal features. The respiratory changes were limited to reduced inspiratory motor drive to the diaphragm. The results are consistent with an important role of sensory feedback from the abdominal wall in regulation of swallow motor pattern. The level of reflex modulation may depend on the extent of injury and likely on its position in the abdomen.
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Affiliation(s)
- Ivan Poliacek
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic
| | - Lukas Martvon
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic; Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Medical Education Support Center, Martin, Slovak Republic.
| | - Michal Simera
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic
| | - Marcel Veternik
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic
| | - Jakub Misek
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic
| | - Lucia Cibulkova
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Mala Hora 4, 03601 Martin, Slovak Republic
| | - Kimberly E Iceman
- Department of Speech Language Hearing Sciences, Dalton Cardiovascular Center, University of Missouri, Columbia, MO, USA
| | - Donald C Bolser
- Dept. of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Teresa Pitts
- Department of Speech Language Hearing Sciences, Dalton Cardiovascular Center, University of Missouri, Columbia, MO, USA
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3
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Abstract
Despite centuries of investigation, questions and controversies remain regarding the fundamental genesis and motor pattern of swallow. Two significant topics include inspiratory muscle activity during swallow (Schluckatmung, i.e., "swallow-breath") and anatomical boundaries of the swallow pattern generator. We discuss the long history of reports regarding the presence or absence of Schluckatmung and the possible advantages of and neural basis for such activity, leading to current theories and novel experimental directions.
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Affiliation(s)
- Teresa Pitts
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky
| | - Kimberly E Iceman
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky
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4
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Musselwhite MN, Shen TY, Rose MJ, Iceman KE, Poliacek I, Pitts T, Bolser DC. THE INFLUENCE OF CO 2 ON SPATIOTEMPORAL FEATURES OF MECHANICALLY INDUCED COUGH IN ANESTHETIZED CATS. Respir Physiol Neurobiol 2022; 307:103964. [PMID: 36174962 DOI: 10.1016/j.resp.2022.103964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 08/10/2022] [Accepted: 09/19/2022] [Indexed: 11/27/2022]
Abstract
Effective cough requires a significant increase in lung volume used to produce the shear forces on the airway to clear aspirated material. This increase in tidal volume during cough, along with an increase in tidal frequency during bouts of paroxysmal cough produces profound hyperventilation and thus reduces arterial CO2. While there are several reports in the literature regarding the effects of hypercapnia, hyperoxia, and hypoxia on cough, there is little research quantifying the effects of hypocapnia on the cough reflex. We hypothesized that decreased CO2 would enhance coughing. In 12 spontaneously breathing adult male cats, we compared bouts of prolonged mechanically stimulated cough, in which cough induced hyperventilation (CHV) was allowed to occur, with isocapnic cough trials where we maintained eupneic end-tidal CO2 by adding CO2 to the inspired gas. Isocapnia slightly increased cough number and decreased esophageal pressures with no change in EMG magnitudes or phase durations. The cough-to-eupnea transition was also analyzed between CHV, isocapnia, and a third group of animals that were mechanically hyperventilated to apnea. The transition to eupnea was highly sensitive to added CO2, and CHV apneas were much shorter than those produced by mechanical hyperventilation. We suggest that the cough pattern generator is relatively insensitive to CHV. In the immediate post-cough period, the appearance of breathing while CO2 is very low suggests a transient reduction in apneic threshold following a paroxysmal cough bout.
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Affiliation(s)
- M Nicholas Musselwhite
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida. 1333 Center Dr, Gainesville, Florida, 32603, United States of America.
| | - Tabitha Y Shen
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida. 1333 Center Dr, Gainesville, Florida, 32603, United States of America
| | - Melanie J Rose
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida. 1333 Center Dr, Gainesville, Florida, 32603, United States of America
| | - Kimberly E Iceman
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville. 511 S Floyd St, MDR 616, Louisville, Kentucky, 40202, United States of America
| | - Ivan Poliacek
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics. Malá hora 4A, 036 01 Martin-Záturčie, Slovakia
| | - Teresa Pitts
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville. 511 S Floyd St, MDR 616, Louisville, Kentucky, 40202, United States of America.
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida. 1333 Center Dr, Gainesville, Florida, 32603, United States of America
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Pitts T, Iceman KE, Huff A, Musselwhite MN, Frazure ML, Young KC, Greene CL, Howland DR. Laryngeal and swallow dysregulation following acute cervical spinal cord injury. J Neurophysiol 2022; 128:405-417. [PMID: 35830612 PMCID: PMC9359645 DOI: 10.1152/jn.00469.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Laryngeal function is vital to airway protection. While swallow is mediated by the brainstem, mechanisms underlying increased risk of dysphagia after cervical spinal cord injury (SCI) are unknown. We hypothesized that loss of descending phrenic drive affects swallow and breathing differently, and loss of ascending spinal afferent information alters swallow regulation. We recorded electromyograms from upper airway and chest wall muscles in freely breathing pentobarbital-anesthetized cats and rats. Inspiratory laryngeal activity increased ~two-fold following C2 lateral-hemisection. Ipsilateral to the injury, crural diaphragm EMG amplitude was reduced during breathing (62 ± 25% change post-injury), but no animal had complete termination of activity; 75% of animals increased contralateral diaphragm recruitment, but this did not reach significance. During swallow, laryngeal adductor and pharyngeal constrictor muscles increased activity, and diaphragm activity was bilaterally suppressed. This was unexpected because of the ipsilateral-specific response during breathing. Swallow-breathing coordination was also disrupted and more swallows occurred during early expiration. Finally, to determine if the chest wall is a major source of feedback for laryngeal regulation, we performed T1 total transections in rats. As in the C2 lateral-hemisection, inspiratory laryngeal recruitment was the first feature noted. In contrast to the C2 lateral-hemisection, diaphragmatic drive increased after T1 transection. Overall, we found that SCI alters laryngeal drive during swallow and breathing, and reduced swallow-related diaphragm activity. Our results show behavior-specific effects, suggesting SCI affects swallow more than breathing, and emphasizes the need for additional studies on the effects of ascending afferents from the spinal cord on laryngeal function.
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Affiliation(s)
- Teresa Pitts
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Kimberly E Iceman
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Alyssa Huff
- Center for Integrative Brain Research, Seattle Children's Hospital, Seattle, WA, United States
| | - Matthew Nicholas Musselwhite
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Michael L Frazure
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Kellyanna C Young
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Clinton L Greene
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States
| | - Dena Ruth Howland
- Kentucky Spinal Cord Injury Center, Department of Neurological Surgery, University of Louisville, Louisville, KY, United States.,Research Service, Robley Rex VA Medical Center, Louisville, KY, United States
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Musselwhite MN, Young KC, Frazure ML, Greene CL, Iceman KE, Pitts T. The 5‐HT
1A
Agonist 8‐OH‐DPAT Enhances Submental Laryngeal Elevator EMG Amplitude During Swallow. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- M. N. Musselwhite
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Kellyanna C. Young
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Michael L. Frazure
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Clinton L. Greene
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
- Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Kimberly E. Iceman
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Teresa Pitts
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
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7
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Young KC, Musselwhite MN, Frazure ML, Greene CL, Iceman KE, Pitts T. The laryngeal adductor reflex (LAR) is modulated by the serotonin 5‐HT
1A
agonist 8‐OH‐DPAT. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kellyanna C. Young
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - M. N. Musselwhite
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Michael L. Frazure
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Clinton L. Greene
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Kimberly E. Iceman
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
| | - Teresa Pitts
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research CenterUniversity of LouisvilleLouisvilleKY
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8
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Musselwhite MN, Shen TY, Rose MJ, Iceman KE, Poliacek I, Pitts T, Bolser DC. Differential effects of acute cerebellectomy on cough in spontaneously breathing cats. PLoS One 2021; 16:e0253060. [PMID: 34153070 PMCID: PMC8216514 DOI: 10.1371/journal.pone.0253060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/27/2021] [Indexed: 11/29/2022] Open
Abstract
The role of the cerebellum in controlling the cough motor pattern is not well understood. We hypothesized that cerebellectomy would disinhibit motor drive to respiratory muscles during cough. Cough was induced by mechanical stimulation of the tracheobronchial airways in anesthetized, spontaneously breathing adult cats (8 male, 1 female), and electromyograms (EMGs) were recorded from upper airway, chest wall, and abdominal respiratory muscles. Cough trials were performed before and at two time points after total cerebellectomy (10 minutes and >1 hour). Unlike a prior report in paralyzed, decerebrated, and artificially ventilated animals, we observed that cerebellectomy had no effect on cough frequency. After cerebellectomy, thoracic inspiratory muscle EMG magnitudes increased during cough (diaphragm EMG increased by 14% at 10 minutes, p = 0.04; parasternal by 34% at 10 minutes and by 32% at >1 hour, p = 0.001 and 0.03 respectively). During cough at 10 minutes after cerebellectomy, inspiratory esophageal pressure was increased by 44% (p = 0.004), thyroarytenoid (laryngeal adductor) muscle EMG amplitude increased 13% (p = 0.04), and no change was observed in the posterior cricoarytenoid (laryngeal abductor) EMG. Cough phase durations did not change. Blood pressure and heart rate were reduced after cerebellectomy, and respiratory rate also decreased due to an increase in duration of the expiratory phase of breathing. Changes in cough-related EMG magnitudes of respiratory muscles suggest that the cerebellum exerts inhibitory control of cough motor drive, but not cough number or phase timing in response to mechanical stimuli in this model early after cerebellectomy. However, results varied widely at >1 hour after cerebellectomy, with some animals exhibiting enhancement or suppression of one or more components of the cough motor behavior. These results suggest that, while the cerebellum and behavior-related sensory feedback regulate cough, it may be difficult to predict the nature of the modulation based on total cerebellectomy.
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Affiliation(s)
- M. Nicholas Musselwhite
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
- * E-mail: (MNM); (TP)
| | - Tabitha Y. Shen
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Melanie J. Rose
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Kimberly E. Iceman
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Ivan Poliacek
- Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Institute of Medical Biophysics, Martin, Slovak Republic
| | - Teresa Pitts
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
- * E-mail: (MNM); (TP)
| | - Donald C. Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
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9
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Frazure ML, Brown AD, Greene CL, Iceman KE, Pitts T. Rapid activation of esophageal mechanoreceptors alters the pharyngeal phase of swallow: Evidence for inspiratory activity during swallow. PLoS One 2021; 16:e0248994. [PMID: 33798212 PMCID: PMC8018667 DOI: 10.1371/journal.pone.0248994] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 03/09/2021] [Indexed: 11/17/2022] Open
Abstract
Swallow is a complex behavior that consists of three coordinated phases: oral, pharyngeal, and esophageal. Esophageal distension (EDist) has been shown to elicit pharyngeal swallow, but the physiologic characteristics of EDist-induced pharyngeal swallow have not been specifically described. We examined the effect of rapid EDist on oropharyngeal swallow, with and without an oral water stimulus, in spontaneously breathing, sodium pentobarbital anesthetized cats (n = 5). Electromyograms (EMGs) of activity of 8 muscles were used to evaluate swallow: mylohyoid (MyHy), geniohyoid (GeHy), thyrohyoid (ThHy), thyropharyngeus (ThPh), thyroarytenoid (ThAr), cricopharyngeus (upper esophageal sphincter: UES), parasternal (PS), and costal diaphragm (Dia). Swallow was defined as quiescence of the UES with overlapping upper airway activity, and it was analyzed across three stimulus conditions: 1) oropharyngeal water infusion only, 2) rapid esophageal distension (EDist) only, and 3) combined stimuli. Results show a significant effect of stimulus condition on swallow EMG amplitude of the mylohyoid, geniohyoid, thyroarytenoid, diaphragm, and UES muscles. Collectively, we found that, compared to rapid cervical esophageal distension alone, the stimulus condition of rapid distension combined with water infusion is correlated with increased laryngeal adductor and diaphragm swallow-related EMG activity (schluckatmung), and post-swallow UES recruitment. We hypothesize that these effects of upper esophageal distension activate the brainstem swallow network, and function to protect the airway through initiation and/or modulation of a pharyngeal swallow response.
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Affiliation(s)
- Michael L Frazure
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America.,Department of Physiology, University of Louisville, Louisville, Kentucky, United States of America
| | - Alyssa D Brown
- School of Medicine, University of Louisville, Louisville, Kentucky, United States of America.,Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America
| | - Clinton L Greene
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Kimberly E Iceman
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Teresa Pitts
- Department of Neurological Surgery and Kentucky Spinal Cord Injury Research Center, College of Medicine, University of Louisville, Louisville, Kentucky, United States of America
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10
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Huff A, Reed MD, Iceman KE, Howland DR, Pitts T. Sex-specific vagal and spinal modulation of swallow and its coordination with breathing. PLoS One 2020; 15:e0234194. [PMID: 32525920 PMCID: PMC7289368 DOI: 10.1371/journal.pone.0234194] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 05/20/2020] [Indexed: 12/18/2022] Open
Abstract
Swallow-breathing coordination is influenced by changes in lung volume, which is modulated by feedback from both vagal and spinal sensory afferents. The purpose of this study was to manipulate feedback from these afferents, with and without a simultaneous mechanical challenge (chest compression), in order to assess the influence of each sensory pathway on swallow in rats. We hypothesized that manipulation of afferent feedback would shift the occurrence of swallow toward the inspiratory phase of breathing. Afferent feedback was perturbed by lidocaine nebulization, extra-thoracic vagotomy, or lidocaine administration to the pleural space in sodium pentobarbital anesthetized rats (N = 43). These different afferent perturbations were performed both in control conditions (no chest compression), and with chest compression. Manipulating pulmonary stretch receptor-mediated volume feedback in male animals decreased swallow occurrence. Female rats appear to rely more on spinal afferent feedback, as swallow occurrence shifted to late expiration with chest compression and vagotomy or lidocaine injections. Results suggest that sex-specific mechanisms modulate swallow-breathing coordination, and that vagal feedback is inhibitory to swallow-related muscles, while spinal feedback from pleural afferents has excitatory effects. This study supports the theory that a balance of vagal and spinal afferent feedback is necessary to maintain an optimal swallow pattern and swallow-breathing coordination.
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Affiliation(s)
- Alyssa Huff
- Department of Physiology, University of Louisville, Louisville, Kentucky, United States of America
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America
| | - Mitchell D. Reed
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America
| | - Kimberly E. Iceman
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America
| | - Dena R. Howland
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America
- Research Service, Robley Rex Veterans Affairs Medical Center, Louisville, Kentucky, United States of America
| | - Teresa Pitts
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America
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11
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King SN, Shen TY, Musselwhite MN, Huff A, Reed MD, Poliacek I, Howland DR, Dixon W, Morris KF, Bolser DC, Iceman KE, Pitts T. Swallow Motor Pattern Is Modulated by Fixed or Stochastic Alterations in Afferent Feedback. Front Hum Neurosci 2020; 14:112. [PMID: 32327986 PMCID: PMC7160698 DOI: 10.3389/fnhum.2020.00112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 03/12/2020] [Indexed: 11/30/2022] Open
Abstract
Afferent feedback can appreciably alter the pharyngeal phase of swallow. In order to measure the stability of the swallow motor pattern during several types of alterations in afferent feedback, we assessed swallow during a conventional water challenge in four anesthetized cats, and compared that to swallows induced by fixed (20 Hz) and stochastic (1-20Hz) electrical stimulation applied to the superior laryngeal nerve. The swallow motor patterns were evaluated by electromyographic activity (EMG) of eight muscles, based on their functional significance: laryngeal elevators (mylohyoid, geniohyoid, and thyrohyoid); laryngeal adductor (thyroarytenoid); inferior pharyngeal constrictor (thyropharyngeus); upper esophageal sphincter (cricopharyngeus); and inspiratory activity (parasternal and costal diaphragm). Both the fixed and stochastic electrical stimulation paradigms increased activity of the laryngeal elevators, produced short-term facilitation evidenced by increasing swallow durations over the stimulus period, and conversely inhibited swallow-related diaphragm activity. Both the fixed and stochastic stimulus conditions also increased specific EMG amplitudes, which never occurred with the water challenges. Stochastic stimulation increased swallow excitability, as measured by an increase in the number of swallows produced. Consistent with our previous results, changes in the swallow motor pattern for pairs of muscles were only sometimes correlated with each other. We conclude that alterations in afferent feedback produced particular variations of the swallow motor pattern. We hypothesize that specific SLN feedback might modulate the swallow central pattern generator during aberrant feeding conditions (food/liquid entering the airway), which may protect the airway and serve as potentially important clinical diagnostic indicators.
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Affiliation(s)
- Suzanne N King
- Department of Otolaryngology-Head and Neck Surgery, University of Louisville, Louisville, KY, United States.,Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States
| | - Tabitha Y Shen
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, United States
| | - M Nicholas Musselwhite
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, United States
| | - Alyssa Huff
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States.,Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Mitchell D Reed
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States.,Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Ivan Poliacek
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, United States.,Department of Medical Biophysics, Jessenius Faculty of Medicine, Comenius University, Bratislava, Slovakia
| | - Dena R Howland
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States.,Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY, United States.,Robley Rex VA Medical Center, Louisville, KY, United States
| | - Warren Dixon
- Department of Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering, University of Florida, Gainesville, FL, United States
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, United States
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, United States
| | - Kimberly E Iceman
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States.,Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Teresa Pitts
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY, United States.,Department of Neurological Surgery, School of Medicine, University of Louisville, Louisville, KY, United States
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12
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Morris KF, Segers LS, Nuding SC, Lindsey BG, Pitts TG, Iceman KE, Bolser DC. SPARC‐Network‐Scale Interactions Among Simultaneously Recorded Brainstem Neurons In The Dorsal Medulla, Ventrolateral Medulla, And Pons: A Substrate For Central Autonomic Control And Processing Of Cardiovascular Afferent Feedback. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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Reed MD, Iceman KE, Harris MB, Taylor BE. Buccal rhythmogenesis and CO 2 sensitivity in Lithobates catesbeianus tadpole brainstems across metamorphosis. Respir Physiol Neurobiol 2019; 268:103251. [PMID: 31279052 DOI: 10.1016/j.resp.2019.103251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 06/19/2019] [Accepted: 07/02/2019] [Indexed: 11/19/2022]
Abstract
Bullfrog tadpoles ventilate both the buccal cavity and lung. In isolated brainstems, the midbrain/pons influences CO2 responsiveness and timing of lung ventilatory bursting, depending on larval development. However, little is known about midbrain/pons influences on buccal burst patterns. As such, we investigated how removal of this region affects buccal burst shape and CO2 responsiveness across development. We measured facial nerve activity in brainstems isolated from tadpoles during early and late developmental stages, under normal and elevated levels of CO2. Brainstems were either left intact or transected by removing the midbrain/pons. In late stage preparations, buccal burst pattern differed between intact and reduced preparations, and bursts were responsive to elevated CO2 in these reduced preparations. These results suggest the midbrain/pons affects tadpole buccal burst pattern and CO2 responsiveness, perhaps similar to its influences on lung ventilation.
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Affiliation(s)
- Mitchell D Reed
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States.
| | - Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, Valparaiso University, Valparaiso, IN, 46383, United States
| | - Michael B Harris
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, California State University Long Beach, Long Beach, CA, 90840, United States
| | - Barbara E Taylor
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, United States; Department of Biology, California State University Long Beach, Long Beach, CA, 90840, United States
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Reed MD, Iceman KE, Harris MB, Taylor BE. The rostral medulla of bullfrog tadpoles contains critical lung rhythmogenic and chemosensitive regions across metamorphosis. Comp Biochem Physiol A Mol Integr Physiol 2018; 225:7-15. [PMID: 29890210 DOI: 10.1016/j.cbpa.2018.05.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 05/14/2018] [Accepted: 05/30/2018] [Indexed: 11/18/2022]
Abstract
The development of amphibian breathing provides insight into vertebrate respiratory control mechanisms. Neural oscillators in the rostral and caudal medulla drive ventilation in amphibians, and previous reports describe ventilatory oscillators and CO2 sensitive regions arise during different stages of amphibian metamorphosis. However, inconsistent findings have been enigmatic, and make comparisons to potential mammalian counterparts challenging. In the current study we assessed amphibian central CO2 responsiveness and respiratory rhythm generation during two different developmental stages. Whole-nerve recordings of respiratory burst activity in cranial and spinal nerves were made from intact or transected brainstems isolated from tadpoles during early or late stages of metamorphosis. Brainstems were transected at the level of the trigeminal nerve, removing rostral structures including the nucleus isthmi, midbrain, and locus coeruleus, or transected at the level of the glossopharyngeal nerve, removing the putative buccal oscillator and caudal medulla. Removal of caudal structures stimulated the frequency of lung ventilatory bursts and revealed a hypercapnic response in normally unresponsive preparations derived from early stage tadpoles. In preparations derived from late stage tadpoles, removal of rostral or caudal structures reduced lung burst frequency, while CO2 responsiveness was retained. Our results illustrate that structures within the rostral medulla are capable of sensing CO2 throughout metamorphic development. Similarly, the region controlling lung ventilation appears to be contained in the rostral medulla throughout metamorphosis. This work offers insight into the consistency of rhythmic respiratory and chemosensitive capacities during metamorphosis.
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Affiliation(s)
- Mitchell D Reed
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States.
| | - Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biology, Valparaiso University, Valparaiso, IN 46383, United States
| | - Michael B Harris
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States
| | - Barbara E Taylor
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, United States; Department of Biological Sciences, California State University Long Beach, Long Beach, CA 90840, United States
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15
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Morris KF, Nuding SC, Segers LS, Iceman KE, O'Connor R, Dean JB, Ott MM, Alencar PA, Shuman D, Horton KK, Taylor-Clark TE, Bolser DC, Lindsey BG. Carotid chemoreceptors tune breathing via multipath routing: reticular chain and loop operations supported by parallel spike train correlations. J Neurophysiol 2017; 119:700-722. [PMID: 29046425 DOI: 10.1152/jn.00630.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We tested the hypothesis that carotid chemoreceptors tune breathing through parallel circuit paths that target distinct elements of an inspiratory neuron chain in the ventral respiratory column (VRC). Microelectrode arrays were used to monitor neuronal spike trains simultaneously in the VRC, peri-nucleus tractus solitarius (p-NTS)-medial medulla, the dorsal parafacial region of the lateral tegmental field (FTL-pF), and medullary raphe nuclei together with phrenic nerve activity during selective stimulation of carotid chemoreceptors or transient hypoxia in 19 decerebrate, neuromuscularly blocked, and artificially ventilated cats. Of 994 neurons tested, 56% had a significant change in firing rate. A total of 33,422 cell pairs were evaluated for signs of functional interaction; 63% of chemoresponsive neurons were elements of at least one pair with correlational signatures indicative of paucisynaptic relationships. We detected evidence for postinspiratory neuron inhibition of rostral VRC I-Driver (pre-Bötzinger) neurons, an interaction predicted to modulate breathing frequency, and for reciprocal excitation between chemoresponsive p-NTS neurons and more downstream VRC inspiratory neurons for control of breathing depth. Chemoresponsive pericolumnar tonic expiratory neurons, proposed to amplify inspiratory drive by disinhibition, were correlationally linked to afferent and efferent "chains" of chemoresponsive neurons extending to all monitored regions. The chains included coordinated clusters of chemoresponsive FTL-pF neurons with functional links to widespread medullary sites involved in the control of breathing. The results support long-standing concepts on brain stem network architecture and a circuit model for peripheral chemoreceptor modulation of breathing with multiple circuit loops and chains tuned by tegmental field neurons with quasi-periodic discharge patterns. NEW & NOTEWORTHY We tested the long-standing hypothesis that carotid chemoreceptors tune the frequency and depth of breathing through parallel circuit operations targeting the ventral respiratory column. Responses to stimulation of the chemoreceptors and identified functional connectivity support differential tuning of inspiratory neuron burst duration and firing rate and a model of brain stem network architecture incorporating tonic expiratory "hub" neurons regulated by convergent neuronal chains and loops through rostral lateral tegmental field neurons with quasi-periodic discharge patterns.
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Affiliation(s)
- Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Sarah C Nuding
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Lauren S Segers
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Kimberly E Iceman
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Russell O'Connor
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Mackenzie M Ott
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Pierina A Alencar
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Dale Shuman
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Kofi-Kermit Horton
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Thomas E Taylor-Clark
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida , Gainesville, Florida
| | - Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
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16
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Nuding SC, Segers LS, Iceman KE, O'Connor R, Dean JB, Bolser DC, Baekey DM, Dick TE, Shannon R, Morris KF, Lindsey BG. Functional connectivity in raphé-pontomedullary circuits supports active suppression of breathing during hypocapnic apnea. J Neurophysiol 2015; 114:2162-86. [PMID: 26203111 PMCID: PMC4600964 DOI: 10.1152/jn.00608.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 07/18/2015] [Indexed: 01/17/2023] Open
Abstract
Hyperventilation is a common feature of disordered breathing. Apnea ensues if CO2 drive is sufficiently reduced. We tested the hypothesis that medullary raphé, ventral respiratory column (VRC), and pontine neurons have functional connectivity and persistent or evoked activities appropriate for roles in the suppression of drive and rhythm during hyperventilation and apnea. Phrenic nerve activity, arterial blood pressure, end-tidal CO2, and other parameters were monitored in 10 decerebrate, vagotomized, neuromuscularly-blocked, and artificially ventilated cats. Multielectrode arrays recorded spiking activity of 649 neurons. Loss and return of rhythmic activity during passive hyperventilation to apnea were identified with the S-transform. Diverse fluctuating activity patterns were recorded in the raphé-pontomedullary respiratory network during the transition to hypocapnic apnea. The firing rates of 160 neurons increased during apnea; the rates of 241 others decreased or stopped. VRC inspiratory neurons were usually the last to cease firing or lose rhythmic activity during the transition to apnea. Mayer wave-related oscillations (0.04-0.1 Hz) in firing rate were also disrupted during apnea. Four-hundred neurons (62%) were elements of pairs with at least one hyperventilation-responsive neuron and a correlational signature of interaction identified by cross-correlation or gravitational clustering. Our results support a model with distinct groups of chemoresponsive raphé neurons contributing to hypocapnic apnea through parallel processes that incorporate disfacilitation and active inhibition of inspiratory motor drive by expiratory neurons. During apnea, carotid chemoreceptors can evoke rhythm reemergence and an inspiratory shift in the balance of reciprocal inhibition via suppression of ongoing tonic expiratory neuron activity.
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Affiliation(s)
- Sarah C Nuding
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Lauren S Segers
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Kimberly E Iceman
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Russell O'Connor
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Jay B Dean
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Donald C Bolser
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida; and
| | - David M Baekey
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida; and
| | - Thomas E Dick
- Departments of Medicine and Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Roger Shannon
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida
| | - Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida;
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17
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Abstract
BACKGROUND Anesthetics have a profound influence on a myriad of autonomic processes. Mechanisms of general anesthesia, and how these mechanisms give rise to the multifaceted state of anesthesia, are largely unknown. The ascending and descending serotonin (5-HT) networks are key modulators of autonomic pathways, and are critically involved in homeostatic reflexes across the motor, somatosensory, limbic and autonomic systems. These 5-HT networks are thought to contribute to anesthetic effects, but how anesthetics affect 5-HT neuron function remains a pertinent question. We hypothesized that the volatile anesthetic isoflurane inhibits action potential discharge of medullary raphé 5-HT neurons. METHODS We conducted extracellular recordings on individual neurons in the medullary raphé region of the unanesthetized in situ perfused brainstem preparation to determine how exposure to isoflurane affects 5-HT neurons. We examined changes in 5-HT neuron baseline firing in response to treatment with either 1, 1.5, or 2% isoflurane. We measured isoflurane concentrations by gas chromatography-mass spectrometry (GC-MS) analysis. RESULTS Exposure to isoflurane inhibited action potential discharge in raphé 5-HT neurons. We document a concentration-dependent inhibition over a range of concentrations approximating isoflurane MAC (minimum alveolar concentration required for surgical anesthesia). Delivered concentrations of isoflurane were confirmed using GC-MS analysis. CONCLUSIONS These findings illustrate that halogenated anesthetics greatly affect 5-HT neuron firing and suggest 5-HT neuron contributions to mechanisms of general anesthesia.
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Affiliation(s)
- S L Johansen
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - K E Iceman
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - C R Iceman
- Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 99775, USA
| | - B E Taylor
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - M B Harris
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA.
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18
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Massey CA, Iceman KE, Johansen SL, Wu Y, Harris MB, Richerson GB. Isoflurane abolishes spontaneous firing of serotonin neurons and masks their pH/CO₂ chemosensitivity. J Neurophysiol 2015; 113:2879-88. [PMID: 25695656 DOI: 10.1152/jn.01073.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 02/18/2015] [Indexed: 11/22/2022] Open
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) neurons from the mouse and rat rostral medulla are stimulated by increased CO2 when studied in culture or brain slices. However, the response of 5-HT neurons has been variable when animals are exposed to hypercapnia in vivo. Here we examined whether halogenated inhalational anesthetics, which activate TWIK-related acid-sensitive K(+) (TASK) channels, could mask an effect of CO2 on 5-HT neurons. During in vivo plethysmography in mice, isoflurane (1%) markedly reduced the hypercapnic ventilatory response (HCVR) by 78-96% depending upon mouse strain and ambient temperature. In a perfused rat brain stem preparation, isoflurane (1%) reduced or silenced spontaneous firing of medullary 5-HT neurons in situ and abolished their responses to elevated perfusate Pco2. In dissociated cell cultures, isoflurane (1%) hyperpolarized 5-HT neurons by 6.52 ± 3.94 mV and inhibited spontaneous firing. A subsequent decrease in pH from 7.4 to 7.2 depolarized neurons by 4.07 ± 2.10 mV, but that was insufficient to reach threshold for firing. Depolarizing current restored baseline firing and the firing frequency response to acidosis, indicating that isoflurane did not block the underlying mechanisms mediating chemosensitivity. These results demonstrate that isoflurane masks 5-HT neuron chemosensitivity in vitro and in situ and markedly decreases the HCVR in vivo. The use of this class of anesthetic has a particularly potent inhibitory effect on chemosensitivity of 5-HT neurons.
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Affiliation(s)
- Cory A Massey
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa Hospitals and Clinics, Iowa City, Iowa; Department of Neurology and NIH/NINDS Center for SUDEP Research, University of Iowa Hospitals and Clinics, Iowa City, Iowa;
| | - Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska
| | - Sara L Johansen
- Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska
| | - Yuanming Wu
- Department of Neurology and NIH/NINDS Center for SUDEP Research, University of Iowa Hospitals and Clinics, Iowa City, Iowa
| | - Michael B Harris
- Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska; Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska
| | - George B Richerson
- Department of Neurology and NIH/NINDS Center for SUDEP Research, University of Iowa Hospitals and Clinics, Iowa City, Iowa; Department of Molecular Physiology and Biophysics, University of Iowa Hospitals and Clinics, Iowa City, Iowa; and Department of Veterans Affairs Medical Center, Iowa City, Iowa
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19
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Iceman KE, Corcoran AE, Taylor BE, Harris MB. CO2-inhibited neurons in the medullary raphé are GABAergic. Respir Physiol Neurobiol 2014; 203:28-34. [PMID: 25087734 DOI: 10.1016/j.resp.2014.07.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Revised: 07/24/2014] [Accepted: 07/24/2014] [Indexed: 11/28/2022]
Abstract
Previous studies have reported subsets of medullary raphé neurons that are either stimulated or inhibited by CO2/pH in vitro, in situ, and in vivo. We tested the hypothesis that medullary raphé CO2-inhibited neurons are GABAergic. Extracellular recordings in unanesthetized juvenile in situ rat preparations showed reversible hypercapnia-induced suppression of 19% (63/323) of medullary raphé neurons, and this suppression persisted after antagonism of NMDA, AMPA/kainate, and GABAA receptors. We stained a subset of CO2-inhibited cells and found that most (11/12) had glutamic acid decarboxylase 67 immunoreactivity (GAD67-ir). These data indicate that the majority of acidosis-inhibited medullary raphé neurons are GABAergic, and that their chemosensitivity is independent of major fast synaptic inputs. Thus, CO2-sensitive GABAergic neurons may play a role in central CO2/pH chemoreception.
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Affiliation(s)
- Kimberly E Iceman
- Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Andrea E Corcoran
- Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Barbara E Taylor
- Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Michael B Harris
- Institute of Arctic Biology and Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
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20
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Abstract
Serotonin/substance P synthesizing cells in the raphé nuclei of the brain are candidates for designation as central chemoreceptors that are stimulated by CO2/pH. We have previously demonstrated that these neurons are CO2-stimulated in situ. Evidence also suggests that CO2-inhibited raphé neurons recorded in vitro and in situ synthesize GABA. Unknown is whether there are other types of chemosensitive cells in the raphé. Here, we showed that a previously unrecognized pool of raphé neurons also exhibit chemosensitivity, and that they are not serotonergic. We used extracellular recording of individual raphé neurons in the unanesthetized juvenile rat in situ perfused decerebrate brainstem preparation to assess chemosensitivity of raphé neurons. Subsequent juxtacellular labeling of individually recorded cells, and immunohistochemistry for the serotonin synthesizing enzyme tryptophan hydroxylase and for neurokinin-1 receptor (NK1R; the receptor for substance P) indicated a group of CO2-stimulated cells that are not serotonergic, but express NK1R and are closely apposed to surrounding serotonergic cells. CO2-stimulated 5-HT and non-5-HT cells constitute distinct groups that have different firing characteristics and hypercapnic sensitivities. Non-5-HT cells fire faster and are more robustly stimulated by CO2 than are 5-HT cells. Thus, we have characterized a previously unrecognized type of CO2-stimulated medullary raphé neuron that is not serotonergic, but may receive input from neighboring serotonin/substance P synthesizing chemosensitive neurons. The potential network properties of the three types of chemosensitive raphé neurons (the present non-5-HT cells, serotonergic cells, and CO2-inhibited cells) remain to be elucidated.
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Affiliation(s)
- K E Iceman
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA.
| | - M B Harris
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
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21
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Abstract
Brainstem central chemoreceptors are critical to the hypercapnic ventilatory response, but their location and identity are poorly understood. When studied in vitro, serotonin-synthesizing (5-HT) neurons within the rat medullary raphé are intrinsically stimulated by CO2/acidosis. The contributions of these neurons to central chemosensitivity in vivo, however, are controversial. Lacking is documentation of CO2-sensitive 5-HT neurons in intact experimental preparations and understanding of their spatial and proportional distribution. Here we test the hypothesis that 5-HT neurons in the rat medullary raphé are sensitive to arterial hypercapnia. We use extracellular recording and hypercapnic challenge of spontaneously active medullary raphé neurons in the unanesthetized in situ perfused decerebrate brainstem preparation to assess chemosensitivity of individual cells. Juxtacellular labeling of a subset of recorded neurons and subsequent immunohistochemistry for the 5-HT-synthesizing enzyme tryptophan hydroxylase (TPH) identify or exclude this neurotransmitter phenotype in electrophysiologically characterized chemosensitive and insensitive cells. We show that the medullary raphé houses a heterogeneous population, including chemosensitive and insensitive 5-HT neurons. Of 124 recorded cells, 16 cells were juxtacellularly filled, visualized, and immunohistochemically identified as 5-HT synthesizing, based on TPH-immunoreactivity. Forty-four percent of 5-HT cells were CO2 stimulated (increased firing rate with hypercapnia), while 56% were unstimulated. Our results demonstrate that medullary raphé neurons are heterogeneous and clearly include a subset of 5-HT neurons that are excited by arterial hypercapnia. Together with data identifying intrinsically CO2-sensitive 5-HT neurons in vitro, these results support a role for such cells as central chemoreceptors in the intact system.
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Affiliation(s)
- Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska
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22
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Johansen SL, Iceman KE, Richerson GB, Harris MB. Isoflurane stimulates firing frequency and masks chemosensitivity of CO
2
‐inhibited GABAergic neurons
in situ. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1137.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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23
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Iceman KE, Richerson GB, Harris MB. GABAergic neurons in the medullary raphé possess network independent chemosensitivity
in situ. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.894.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - George B. Richerson
- Departments of Neurology, and Molecular Physiology and BiophysicsUniversity of IowaIowa CityIA
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24
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Dave KR, Anthony Defazio R, Raval AP, Dashkin O, Saul I, Iceman KE, Perez-Pinzon MA, Drew KL. Protein kinase C epsilon activation delays neuronal depolarization during cardiac arrest in the euthermic arctic ground squirrel. J Neurochem 2009; 110:1170-9. [PMID: 19493168 DOI: 10.1111/j.1471-4159.2009.06196.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
During the pre-hibernation season, arctic ground squirrels (AGS) can tolerate 8 min of asphyxial cardiac arrest (CA) without detectable brain pathology. Better understanding of the mechanisms regulating innate ischemia tolerance in AGS has the potential to facilitate the development of novel prophylactic agents to induce ischemic tolerance in patients at risk of stroke or CA. We hypothesized that neuroprotection in AGS involves robust maintenance of ion homeostasis similar to anoxia-tolerant turtles. Ion homeostasis was assessed by monitoring ischemic depolarization (ID) in cerebral cortex during CA in vivo and during oxygen glucose deprivation in vitro in acutely prepared hippocampal slices. In both models, the onset of ID was significantly delayed in AGS compared with rats. The epsilon protein kinase C (epsilonPKC) is a key mediator of neuroprotection and inhibits both Na+/K+-ATPase and voltage-gated sodium channels, primary mediators of the collapse of ion homeostasis during ischemia. The selective peptide inhibitor of epsilonPKC (epsilonV1-2) shortened the time to ID in brain slices from AGS but not in rats despite evidence that epsilonV1-2 decreased activation of epsilonPKC in brain slices from both rats and AGS. These results support the hypothesis that epsilonPKC activation delays the collapse of ion homeostasis during ischemia in AGS.
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Affiliation(s)
- Kunjan R Dave
- Department of Neurology, Cerebral Vascular Disease Research Center, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida 33101, USA.
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25
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Brundage CM, Iceman KE, Taylor BE. Ethanol affects the respiratory control network through more than GABA receptors. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.783.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Cord M Brundage
- Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksAK
| | - Kimberly E Iceman
- Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksAK
| | - Barbara E Taylor
- Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksAK
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