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Yamauchi M, Dostal J, Kimura H, Strohl KP. Effects of buspirone on posthypoxic ventilatory behavior in the C57BL/6J and A/J mouse strains. J Appl Physiol (1985) 2008; 105:518-26. [PMID: 18511527 DOI: 10.1152/japplphysiol.00069.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Buspirone, a partial agonist of the serotonergic 5-HT1A receptor, improves breathing irregularities in humans with Rett syndrome or brain stem injury. The purpose of this study was to examine whether buspirone alters posthypoxic ventilatory behavior in C57BL/6J (B6) and A/J mouse strains. Measurements of ventilatory behavior were collected from unanesthetized adult male mice (n=6 for each strain) using the plethysmographic method. Mice were given intraperitoneal injections of vehicle or several doses of buspirone and exposed to 2 min of hypoxia (10% O2) followed by rapid reoxygenation (100% O2). Twenty minutes later, mice were tested for hypercapnic response (8% CO(2)-92% O2). On a separate day, mice were injected with the 5-HT1A receptor antagonist 4-iodo-N-{2-[4-(methoxyphenyl)-1-piperazinyl] ethyl}-N-2-pyridinylbenzamide (p-MPPI) before the injection of buspirone, and measurements were repeated. In separate studies, arterial blood-gas analysis was performed for each strain (n=12 in B6 and 10 in A/J) with buspirone or vehicle. In both strains, buspirone stimulated ventilation at rest. In the B6 mice, the hypoxic response was unchanged, but the response to hypercapnia was reduced with buspirone (5 mg/kg; P<0.05). With reoxygenation, vehicle-treated B6 exhibited periodic breathing and greater variation in ventilation compared with A/J (P<0.01). In B6 animals, >or=3 mg/kg of buspirone reduced variation and prevented the occurrence of posthypoxic periodic breathing. Both effects were reversed by p-MPPI. Treatment effect of buspirone was not explained by a difference in resting arterial blood gases. We conclude that buspirone improves posthypoxic ventilatory irregularities in the B6 mouse through its agonist effects on the 5-HT1A receptor.
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Affiliation(s)
- Motoo Yamauchi
- Department of Medicine, Case Western Reserve University, VA Medical Center, Research Service K216, 10701 East Blvd., Cleveland, OH 44106, USA.
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Morse L, Teng YD, Pham L, Newton K, Yu D, Liao WL, Kohler T, Müller R, Graves D, Stashenko P, Battaglino R. Spinal cord injury causes rapid osteoclastic resorption and growth plate abnormalities in growing rats (SCI-induced bone loss in growing rats). Osteoporos Int 2008; 19:645-52. [PMID: 17987335 PMCID: PMC4370281 DOI: 10.1007/s00198-007-0494-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Accepted: 09/21/2007] [Indexed: 01/08/2023]
Abstract
UNLABELLED Spinal cord injury causes severe bone loss. We report osteoclast resorption with severe trabecular and cortical bone loss, decreased bone mineral apposition, and growth plate abnormalities in a rodent model of contusion spinal cord injury. These findings will help elucidate the mechanisms of osteoporosis following neurological trauma. INTRODUCTION Limited understanding of the mechanism(s) that underlie spinal cord injury (SCI)-induced bone loss has led to few treatment options. As SCI-induced osteoporosis carries significant morbidity and can worsen already profound disability, there is an urgency to advance knowledge regarding this pathophysiology. METHODS A clinically relevant contusion model of experimental spinal cord injury was used to generate severe lower thoracic SCI by weight-drop (10 g x 50 mm) in adolescent male Sprague-Dawley rats. Body weight and gender-matched naïve (no surgery) rats served as controls. Bone microarchitecture was determined by micro-computed tomographic imaging. Mature osteoclasts were identified by TRAP staining and bone apposition rate was determined by dynamic histomorphometry. RESULTS At 10 days post-injury we detected a marked 48% decrease in trabecular bone and a 35% decrease in cortical bone at the distal femoral metaphysis by micro-CT. A 330% increase in the number of mature osteoclasts was detected at the growth plate in the injured animals that corresponded with cellular disorganization at the chondro-osseous junction. Appositional growth studies demonstrated decreased new bone formation with a mineralization defect indicative of osteoblast dysfunction. CONCLUSIONS Contusion SCI results in a rapid bone loss that is the result of increased bone resorption and decreased bone formation.
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Affiliation(s)
- L Morse
- Department of Physical Medicine and Rehabilitation, Harvard Medical School and Spaulding Rehabilitation Hospital, Boston, MA 02115, USA.
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Besnard S, Massé F, Verdaguer M, Cappelin B, Meurice JC, Gestreau C. Time- and dose-related effects of three 5-HT receptor ligands on the genioglossus activity in anesthetized and conscious rats. Sleep Breath 2008; 11:275-84. [PMID: 17457631 DOI: 10.1007/s11325-007-0107-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Clinical trials in obstructive sleep apnea syndrome patients reported moderate effects of serotoninergic drugs on oropharyngeal apneas, although numerous specific 5-HT ligands highly modulate the genioglossus muscle (GG) activity in experiments performed in anesthetized animals. The purpose of this study was to investigate time- and dose-related effects of central and systemic injections of 8-OHDPAT (5-HT1A agonist), SB224289 (5-HT1B antagonist), and DOI (5-HT2A/2C agonist) on the GG activity in anesthetized and conscious rats. Electromyographic recordings of the GG activity (GGemg) were analyzed after central and systemic injections of each drug in ketamine-xylazine anesthetized rats. Electroencephalograms (EEG), as well as neck and GG muscle activities (Nemg and GGemg), were recorded in 15 additional rats to analyze changes in sleep-wake states before and after systemic injection of the drugs. Central injections of 8-OHDPAT and DOI in anesthetized rats induced clear dose-related increases in phasic and tonic GGemg activities, respectively. The time-responses were inferior to 30 min with 8-OHDPAT and over 50 min with DOI. Moderate increases in phasic GGemg activity were also observed after central, but not peripheral injection of SB and DOI. The total sleep time measured in conscious rats significantly decreased after systemic injections of DOI and 8-OHDPAT, although no change was observed in phasic or tonic GGemg activity. The dose- and time-responses of the DOI in anesthetized rat partly explain the lack of GGemg tonic change in conscious rat. The moderate effect on the GGemg phasic activity of peripheral 5-HT1A ligand injection easily explains the lack of change in conscious rat. The serotonergic modulation of the respiratory component of the GGemg remains complex, but is highly sensitive to 5-HT1A receptors after central injection in rats under anesthesia. Forthcoming therapy in OSAS should be made of mixed profiled neurotransmitters and different routes of administration.
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Affiliation(s)
- S Besnard
- Neurophysiologie Clinique-Sommeil CHU de Poitiers, Université de Poitiers, 2 rue de la Milétrie, 86021 Poitiers cedex, France.
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Fuller DD, Doperalski NJ, Dougherty BJ, Sandhu MS, Bolser DC, Reier PJ. Modest spontaneous recovery of ventilation following chronic high cervical hemisection in rats. Exp Neurol 2008; 211:97-106. [PMID: 18308305 DOI: 10.1016/j.expneurol.2008.01.013] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 12/04/2007] [Accepted: 01/08/2008] [Indexed: 10/22/2022]
Abstract
Following C2 spinal hemisection (C2HS) in adult rats, ipsilateral phrenic motoneuron (PhMN) recovery occurs through a time-dependent activation of latent, crossed-spinal collaterals (i.e., spontaneous crossed phrenic phenomenon; sCPP) from contralateral bulbospinal axons. Ventilation is maintained during quiet breathing after C2HS, but the ability to increase ventilation during a respiratory stimulation (e.g. hypercapnia) is impaired. We hypothesized that long-term expression of the sCPP would correspond to a progressive normalization in ventilatory patterns during respiratory challenge. Breathing was assessed via plethsymography in unanesthetized animals and phrenic motor output was measured in urethane-anesthetized, paralyzed and vagotomized rats. At 2-week post-C2HS, minute ventilation (VE) was maintained during baseline (room air) conditions as expected but was substantially blunted during hypercapnic challenge (68+/-3% of VE in uninjured, weight-matched rats). However, by 12 weeks the spinal-lesioned rats achieved a hypercapnic VE response that was 85+/-7% of control (p=0.017 vs. 2 wks). These rats also exhibited augmented breaths (AB's) or "sighs" more frequently (p<0.05) than controls; however, total AB volume was significantly less than control at 2- and 12-week post-injury (69+/-4% and 80+/-5%, p<0.05, respectively). We also noted that phrenic neurograms demonstrated a consistent delay in onset of the ipsilateral vs. contralateral inspiratory phrenic burst at 2-12-week post-injury. Finally, the ipsilateral phrenic response to respiratory challenge (hypoxia) was greater, though not normalized, at 4-12- vs. 2-week post-injury. We conclude that recovery of ventilation deficits occurs over 2-12-week post-C2HS; however, intrinsic neuroplasticity remains insufficient to concurrently restore a normal level of ipsilateral phrenic output.
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Affiliation(s)
- D D Fuller
- University of Florida, College of Health and Health Professions, Department of Physical Therapy, 100 Newell Drive, Gainesville, FL 32610, USA.
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8-OH-DPAT suppresses spontaneous central apneas in the C57BL/6J mouse strain. Respir Physiol Neurobiol 2007; 161:10-5. [PMID: 18155647 DOI: 10.1016/j.resp.2007.11.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2007] [Revised: 11/07/2007] [Accepted: 11/08/2007] [Indexed: 11/23/2022]
Abstract
Apneas are common and prognostically relevant disorders of the central control of breathing, but pharmacological interventions are dissatisfying. The respiratory phenotype of C57BL/6J mice is characterized by the occurrence of spontaneous central apneas with laryngeal closure. In the present study we investigated the impact of the 5-HT(1A) receptor agonist 8-OH-DPAT on apneas in C57BL/6J mice, because of the important role of serotonin in the regulation of breathing and previous reports showing that serotonergic drugs can affect central apneas. Whole-body plethysmography in awake, unrestrained mice revealed that intraperitoneal application of 8-OH-DPAT (10microgkg(-1)) decreased the occurrence of spontaneous apneas from 1.91+/-0.25 to 1.05+/-0.05 apneas min(-1). The efficacy of 5-HT(1A) receptor activation was further verified in the in situ working heart-brainstem preparation. Here the apneas occurred at a frequency of 1.33+/-0.19min(-1). Intra-arterial perfusion with 1-2microM 8-OH-DPAT completely abolished spontaneous apneas. These results suggest that 5-HT(1A) receptor activation may be a potential treatment option for central apneas.
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Zimmer MB, Nantwi K, Goshgarian HG. Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options. J Spinal Cord Med 2007; 203:98-108. [PMID: 17853653 DOI: 10.1016/j.resp.2014.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 02/09/2023] Open
Abstract
Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.
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Affiliation(s)
- M Beth Zimmer
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48201, USA.
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Bravo G, Ibarra A, Guizar-Sahagún G, Rojas G, Hong E. Indorenate improves motor function in rats with chronic spinal cord injury. Basic Clin Pharmacol Toxicol 2007; 100:67-70. [PMID: 17214613 DOI: 10.1111/j.1742-7843.2007.00004.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The effect of indorenate (5-methoxytryptamine, beta-methyl carboxylate hydrochloride), a 5-HT1A agonist, was investigated on the motor performance of rats with chronic spinal cord injury. Four months after a ninth thoracic vertebrae spinal cord contusion, 29 rats were randomly allocated into two groups: saline solution and indorenate-treated animals with daily doses incremented at weekly intervals. The locomotor performance of all rats was measured by the Basso, Beattie, and Bresnahan (BBB) rating scale. The results showed that at the end of the treatment, the motor activity of indorenate group was significantly better than that presented by saline solution group. The 80% of indorenate, (against 15% of saline solution) did not show detriment on motor activity. When we analysed the motor activity of rats with basal BBB lower than 10, a significant improvement of motor recovery in indorenate-treated animals was observed. The benefits observed in locomotor function at low doses followed by increasing doses could be associated with pharmacological treatment by indorenate, a well-known 5-HT1A receptor agonist. Our results suggest a potential mechanism by which serotonergic agents may improve motor function in rats with chronic spinal cord injury.
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Affiliation(s)
- Guadalupe Bravo
- Department of Pharmacobiology, CINVESTAV-IPN, Sede Sur, Mexico.
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Zimmer MB, Nantwi K, Goshgarian HG. Effect of spinal cord injury on the respiratory system: basic research and current clinical treatment options. J Spinal Cord Med 2007; 30:319-30. [PMID: 17853653 PMCID: PMC2031930 DOI: 10.1080/10790268.2007.11753947] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Accepted: 02/05/2007] [Indexed: 10/21/2022] Open
Abstract
Spinal cord injury (SCI) often leads to an impairment of the respiratory system. The more rostral the level of injury, the more likely the injury will affect ventilation. In fact, respiratory insufficiency is the number one cause of mortality and morbidity after SCI. This review highlights the progress that has been made in basic and clinical research, while noting the gaps in our knowledge. Basic research has focused on a hemisection injury model to examine methods aimed at improving respiratory function after SCI, but contusion injury models have also been used. Increasing synaptic plasticity, strengthening spared axonal pathways, and the disinhibition of phrenic motor neurons all result in the activation of a latent respiratory motor pathway that restores function to a previously paralyzed hemidiaphragm in animal models. Human clinical studies have revealed that respiratory function is negatively impacted by SCI. Respiratory muscle training regimens may improve inspiratory function after SCI, but more thorough and carefully designed studies are needed to adequately address this issue. Phrenic nerve and diaphragm pacing are options available to wean patients from standard mechanical ventilation. The techniques aimed at improving respiratory function in humans with SCI have both pros and cons, but having more options available to the clinician allows for more individualized treatment, resulting in better patient care. Despite significant progress in both basic and clinical research, there is still a significant gap in our understanding of the effect of SCI on the respiratory system.
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Affiliation(s)
- M Beth Zimmer
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan 48201, USA.
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Teng YD, Liao WL, Choi H, Konya D, Sabharwal S, Langer R, Sidman RL, Snyder EY, Frontera WR. Physical activity-mediated functional recovery after spinal cord injury: potential roles of neural stem cells. Regen Med 2006; 1:763-76. [PMID: 17465758 DOI: 10.2217/17460751.1.6.763] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
As data elucidating the complexity of spinal cord injury pathophysiology emerge, it is increasingly being recognized that successful repair will probably require a multifaceted approach that combines tactics from various biomedical disciplines, including pharmacology, cell transplantation, gene therapy and material sciences. Recently, new evidence highlighting the benefit of physical activity and rehabilitation interventions during the post-injury phase has provided novel possibilities in realizing effective repair after spinal cord injury. However, before a comprehensive therapeutic strategy that optimally utilizes the benefits of each of these disciplines can be designed, the basic mechanisms by which these various interventions act must be thoroughly explored and important synergistic and antagonistic interactions identified. In examining the mechanisms by which physical activity-based functional recovery after spinal cord injury is effected, endogenous neural stem cells, in our opinion, engender a potentially key role. Multipotent neural stem cells possess many faculties that abet recovery, including the ability to assess the local microenvironment and deliver biofactors that promote neuroplasticity and regeneration, as well as the potential to replenish damaged or eradicated cellular elements. Encouragingly, the functional recovery owing to physical activity-based therapies appears relatively robust, even when therapy is initiated in the chronic stage of spinal cord injury. In this article, we review experimental outcomes related to our hypothesis that endogenous neural stem cells mediate the functional recovery noted in spinal cord injury following physical activity-based treatments. Overall, the data advocates the incorporation of increased physical activity as a component of the multidimensional treatment of spinal cord injury and underscores the critical need to employ research-based mechanistic approaches for developing future advances in the rehabilitation of neurological injury and disorders.
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Affiliation(s)
- Yang D Teng
- Department of Neurosurgery, Harvard Medical School, Brigham and Women's Hospital and Children's Hospital Boston, Boston, MA 02115, USA.
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Zimmer MB, Goshgarian HG. Spinal activation of serotonin 1A receptors enhances latent respiratory activity after spinal cord injury. J Spinal Cord Med 2006; 29:147-55. [PMID: 16739558 PMCID: PMC1864797 DOI: 10.1080/10790268.2006.11753868] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 10/25/2005] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND/OBJECTIVE Hemisection of the cervical spinal cord results in paralysis of the ipsilateral hemidiaphragm. Removal of sensory feedback through cervical dorsal rhizotomy activates latent respiratory motor pathways and restores hemidiaphragm function. Because systemic administration of serotonin 1A receptor (5HT1A) agonists reversed the altered breathing patterns after spinal cord injury (SCI), we predicted that 5HT1A receptor activation after SCI (C2) would activate latent crossed motor pathways. Furthermore, because 5HT1 A receptors are heavily localized to dorsal horn neurons, we predicted that spinal administration of 5HT1A agonists should also activate latent motor pathways. METHODS Hemisection of the C2 spinal cord was performed 24 to 48 hours, 1 week, or 16 weeks before experimentation. Bilateral phrenic nerve activity was recorded in anesthetized, vagotomized, paralyzed Sprague-Dawley rats, and 8-OH-DPAT (5HT1A agonist) was applied to the dorsal aspect of the cervical spinal cord (C3-C7) or injected systemically. RESULTS Systemic administration of 8-OH-DPAT led to a significant increase in phrenic frequency and amplitude, whereas direct application to the spinal cord increased phrenic amplitude alone. Both systemic and spinal administration of 8-OH-DPAT consistently activated latent crossed phrenic activity. 8-OH-DPAT induced a greater respiratory response in spinal injured rats compared with controls. CONCLUSION The increase in crossed phrenic output after application of 8-OH-DPAT to the spinal cord suggests that dorsal horn inputs, respiratory and/or nonrespiratory, may inhibit phrenic motor output, especially after SCI. These findings support the idea that the administration of 5HT1A agonists may be a beneficial therapy in enhancing respiratory neural output in patients with SCI.
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Affiliation(s)
- M Beth Zimmer
- Wayne State University School of Medicine, Department of Anatomy and Cell Biology, 540 East Canfield, Detroit, MI 48201, USA.
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