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McAdams RM, McPherson RJ, Kapur R, Phillips B, Shen DD, Juul SE. Dexmedetomidine reduces cranial temperature in hypothermic neonatal rats. Pediatr Res 2015; 77:772-8. [PMID: 25751572 DOI: 10.1038/pr.2015.45] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/21/2014] [Indexed: 01/20/2023]
Abstract
BACKGROUND The α2-adrenergic agonist dexmedetomidine (DEX) is increasingly used for prolonged sedation of critically ill neonates, but there are currently no data evaluating possible consequences of prolonged neonatal DEX exposure. We evaluated the pharmacokinetics and histological consequences of neonatal DEX exposure. METHODS DEX was administered (s.c.) to naive (uninjured) neonatal Lewis rats to provide acute (25 µg/kg, ×1) or prolonged (25 µg/kg three times daily, ×2 or ×4 d) exposure. Therapeutic hypothermia was simulated using a water-cooled blanket. Cranial temperatures were measured using an infrared thermometer. DEX concentrations were measured by LC-MS in plasma and homogenized brainstem tissue for pharmacokinetic analysis. Cortex, cerebellum, and brainstem were evaluated for evidence of inflammation or injury. RESULTS Prolonged neonatal DEX exposure was not associated with renal or brain pathology or indices of gliosis, macrophage activation, or apoptosis in either hypothermic or control rats. Plasma and brain DEX concentrations were tightly correlated. DEX peaked within 15 min in brain and reduced cranial temperature from 32 to 30 °C within 30 min after injection in cooled rats. CONCLUSION Prolonged DEX treatment in neonatal rats was not associated with abnormal brain histology. These data provide reassuring preliminary results for using DEX with therapeutic hypothermia to treat near-term brain injury.
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Affiliation(s)
- Ryan M McAdams
- 1] Department of Pediatrics, University of Washington, Seattle, Washington [2] Seattle Children's Hospital, Seattle, Washington
| | | | - Raj Kapur
- 1] Seattle Children's Hospital, Seattle, Washington [2] Department of Pathology, University of Washington, Seattle, Washington
| | - Brian Phillips
- Department of Pharmaceutics, University of Washington, Seattle, Washington
| | - Danny D Shen
- Department of Pharmaceutics, University of Washington, Seattle, Washington
| | - Sandra E Juul
- 1] Department of Pediatrics, University of Washington, Seattle, Washington [2] Seattle Children's Hospital, Seattle, Washington
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2
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Santiago FE, Fior-Chadi DR, Carrettiero DC. Alpha2-adrenoceptor and adenosine A1 receptor within the nucleus tractus solitarii in hypertension development. Auton Neurosci 2014; 187:36-44. [PMID: 25466830 DOI: 10.1016/j.autneu.2014.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 10/21/2014] [Accepted: 11/01/2014] [Indexed: 02/07/2023]
Abstract
Alpha2-adrenoceptor and A1 adenosine receptor systems within the nucleus tractus solitarii (NTS) play an important role in cardiovascular control. Deregulation of these systems may result in an elevated sympathetic tone, one of the root causes of neurogenic hypertension. The dorsomedial/dorsolateral and subpostremal NTS subnuclei of spontaneously hypertensive rats (SHR) show density changes in both receptors, even at 15 days of age, prior to the onset of hypertension. In addition, adenosine A1 receptors have been specifically reported to modulate alpha2-adrenoceptors in several brain regions, including the NTS, via a PLC-dependent pathway involving cross regulation between sympathetic neurons and astrocytes. The physiological cross talk between these receptor systems is also deregulated in SHR suggesting that alpha2-adrenoceptor and A1 adenosine receptor might be germane to the development of hypertension. In this review, we will focus on these systems within the NTS during development, pointing out some interesting modulations in processes, and chemical changes within specific subnuclei of NTS circuitry, that might have implications for neurogenic hypertension.
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Affiliation(s)
- Fernando E Santiago
- Universidade Federal do ABC (UFABC), Centro de Ciências Naturais e Humanas, Santo André, SP, Brazil
| | - Débora R Fior-Chadi
- Universidade de São Paulo (USP), Departamento de Fisiologia, Instituto de Biociências, São Paulo, SP, Brazil
| | - Daniel C Carrettiero
- Universidade Federal do ABC (UFABC), Centro de Ciências Naturais e Humanas, Santo André, SP, Brazil.
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Laurila JMM, Wissel G, Xhaard H, Ruuskanen JO, Johnson MS, Scheinin M. Involvement of the first transmembrane segment of human α(2) -adrenoceptors in the subtype-selective binding of chlorpromazine, spiperone and spiroxatrine. Br J Pharmacol 2012; 164:1558-72. [PMID: 21649638 DOI: 10.1111/j.1476-5381.2011.01520.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Some large antagonist ligands (ARC239, chlorpromazine, prazosin, spiperone, spiroxatrine) bind to the human α(2A) -adrenoceptor with 10- to 100-fold lower affinity than to the α(2B)- and α(2C)-adrenoceptor subtypes. Previous mutagenesis studies have not explained this subtype selectivity. EXPERIMENTAL APPROACH The possible involvement of the extracellular amino terminus and transmembrane domain 1 (TM1) in subtype selectivity was elucidated with eight chimaeric receptors: six where TM1 and the N-terminus were exchanged between the α(2)-adrenoceptor subtypes and two where only TM1 was exchanged. Receptors were expressed in CHO cells and tested for ligand binding with nine chemically diverse antagonist ligands. For purposes of interpretation, molecular models of the three human α(2)-adrenoceptors were constructed based on the β(2)-adrenoceptor crystal structure. KEY RESULTS The affinities of three antagonists (spiperone, spiroxatrine and chlorpromazine) were significantly improved by TM1 substitutions of the α(2A)-adrenoceptor, but reciprocal effects were not seen for chimaeric receptors based on α(2B)- and α(2C)-adrenoceptors. Molecular docking of these ligands suggested that binding occurs in the orthosteric ligand binding pocket. CONCLUSIONS AND IMPLICATIONS TM1 is involved in determining the low affinity of some antagonist ligands at the human α(2A)-adrenoceptor. The exact mechanism is not known, but the position of TM1 at a large distance from the binding pocket indicates that TM1 does not participate in specific side-chain interactions with amino acids within the binding pocket of the receptor or with ligands bound therein. Instead, molecular models suggest that TM1 has indirect conformational effects related to the charge distribution or overall shape of the binding pocket.
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Affiliation(s)
- J M M Laurila
- Department of Pharmacology, Drug Development and Therapeutics, University of Turku, Turku, Finland
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4
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Carrettiero DC, Ferrari MF, Fior-Chadi DR. Alpha2-adrenergic receptor distribution and density within the nucleus tractus solitarii of normotensive and hypertensive rats during development. Auton Neurosci 2012; 166:39-46. [DOI: 10.1016/j.autneu.2011.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Revised: 09/29/2011] [Accepted: 10/01/2011] [Indexed: 02/07/2023]
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Kinney HC, Richerson GB, Dymecki SM, Darnall RA, Nattie EE. The brainstem and serotonin in the sudden infant death syndrome. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2009; 4:517-50. [PMID: 19400695 DOI: 10.1146/annurev.pathol.4.110807.092322] [Citation(s) in RCA: 230] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The sudden infant death syndrome (SIDS) is the sudden death of an infant under one year of age that is typically associated with sleep and that remains unexplained after a complete autopsy and death scene investigation. A leading hypothesis about its pathogenesis is that many cases result from defects in brainstem-mediated protective responses to homeostatic stressors occurring during sleep in a critical developmental period. Here we review the evidence for the brainstem hypothesis in SIDS with a focus upon abnormalities related to the neurotransmitter serotonin in the medulla oblongata, as these are the most robust pathologic findings to date. In this context, we synthesize the human autopsy data with genetic, whole-animal, and cellular data concerning the function and development of the medullary serotonergic system. These emerging data suggest an important underlying mechanism in SIDS that may help lead to identification of infants at risk and specific interventions to prevent death.
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Affiliation(s)
- Hannah C Kinney
- Department of Pathology, Children's Hospital Boston and Harvard Medical School, Boston, MA 02115, USA.
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6
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Walker SM, Fitzgerald M. Characterization of spinal alpha-adrenergic modulation of nociceptive transmission and hyperalgesia throughout postnatal development in rats. Br J Pharmacol 2007; 151:1334-42. [PMID: 17533423 PMCID: PMC2189833 DOI: 10.1038/sj.bjp.0707290] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The selective alpha(2)-adrenergic agonist dexmedetomidine is used clinically for analgesia and sedation, but effects in early life are not well characterized. Investigation of age-related effects of dexmedetomidine is important for evaluating responses to exogenously administered analgesics and provides insight into postnatal function of noradrenergic pathways. EXPERIMENTAL APPROACH We examined effects of epidural dexmedetomidine in anaesthetized rat pups (3, 10 and 21 postnatal days) using a quantitative model of nociception and C-fibre induced hyperalgesia. Electromyographic recordings of withdrawal responses to hindpaw mechanical stimuli measured effects of dexmedetomidine upon the baseline reflex and the response to mustard oil application on the hindpaw (primary hyperalgesia) or hindlimb (secondary hyperalgesia). In addition, we compared epidural with systemic administration, examined effects of spinal transection and evaluated heart rate changes following dexmedetomidine. KEY RESULTS Epidural dexmedetomidine dose-dependently prevented mustard oil-induced hyperalgesia at all ages but dose requirements were lower in the youngest pups. Higher doses also suppressed the baseline nociceptive reflex when given epidurally, but had no effect when given systemically. Analgesic efficacy was the same for primary and secondary hyperalgesia, and was not diminished by spinal cord transection. CONCLUSIONS AND IMPLICATIONS Our laboratory studies predict that spinally mediated alpha(2)-agonist analgesia would be effective throughout postnatal development, dose requirements would be lower in early life and selective anti-hyperalgesic effects could be achieved with epidural administration at doses lower than associated with antinociceptive or cardiovascular effects. Clinical trials of alpha(2) agonists in neonates and infants should consider developmentally regulated changes.
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Affiliation(s)
- S M Walker
- Portex Anaesthesia Unit, UCL Institute of Child Health, University College London, London, UK.
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Darnall RA, Ariagno RL, Kinney HC. The late preterm infant and the control of breathing, sleep, and brainstem development: a review. Clin Perinatol 2006; 33:883-914; abstract x. [PMID: 17148011 DOI: 10.1016/j.clp.2006.10.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The brainstem development of infants born between 33 and 38 weeks' gestation is less mature than that of a full-term infant. During late gestation, there are dramatic and nonlinear developmental changes in the brainstem. This translates into immaturity of upper airway and lung volume control, laryngeal reflexes, chemical control of breathing, and sleep mechanisms. Ten percent of late preterm infants have significant apnea of prematurity and they frequently have delays in establishing coordination of feeding and breathing. Unfortunately, there is a paucity of clinical, physiologic, neuroanatomic, and neurochemical data in this specific group of infants. Research focused on this group of infants will not only further our understanding of brainstem maturation during this high risk period, but will help develop focused plans for their management.
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Affiliation(s)
- Robert A Darnall
- Department of Physiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
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Rochette A, Troncin R, Raux O, Dadure C, Lubrano JF, Barbotte E, Capdevila X. Clonidine added to bupivacaine in neonatal spinal anesthesia: a prospective comparison in 124 preterm and term infants. Paediatr Anaesth 2005; 15:1072-7. [PMID: 16324026 DOI: 10.1111/j.1460-9592.2005.01664.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Spinal anesthesia (SA) remains the 'gold standard' in neonatal anesthesia for inguinal herniorrhaphy but its short duration impedes its usefulness. We previously demonstrated that clonidine prolongs neonatal SA without immediate side effects. METHODS We conducted a prospective observational study of 124 infants undergoing herniorrhaphy under SA with bupivacaine and clonidine. Two cohorts, term (n = 57) and former preterm (n = 67) infants, were evaluated and compared with regard to episodes of apnea, desaturation, and bradycardia within 24 h of SA. RESULTS In both groups, postoperative desaturation episodes were unchanged after SA, compared with the 12 preoperative hours, despite significantly increased apnea (P < 0.003 and <0.011 respectively). Transient bradycardias occurred in former preterm infants (P < 0.014): they spontaneously resolved in all cases. Mean arterial pressure did not vary during the study. Upper sensory level of SA, sedation on entering the postanesthesia care unit (PACU) and duration of stay in the PACU were similar in both groups. CONCLUSIONS The clinical significance of short apneas, recovering spontaneously without desaturation, remains debatable. It is concluded that addition of clonidine to neonatal SA results in acceptable side effects. Side effects must be compared with the potential advantages before future recommendations.
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Affiliation(s)
- Alain Rochette
- Department of Anesthesiology and Intensive Care Medicine A, University Hospital Lapeyronie, Montpellier, France.
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9
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Ruuskanen JO, Peitsaro N, Kaslin JVM, Panula P, Scheinin M. Expression and function of alpha-adrenoceptors in zebrafish: drug effects, mRNA and receptor distributions. J Neurochem 2005; 94:1559-69. [PMID: 16000146 DOI: 10.1111/j.1471-4159.2005.03305.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The alpha2-adrenoceptors are G-protein-coupled receptors that mediate many of the physiological effects of norepinephrine and epinephrine. Mammals have three subtypes of alpha2-adrenoceptors, alpha2A, alpha2B and alpha2C. Zebrafish, a teleost fish used widely as a model organism, has five distinct alpha2-adrenoceptor genes. The zebrafish has emerged as a powerful tool to study development and genetics, with many mutations causing diseases reminiscent of human diseases. Three of the zebrafish adra2 genes code for orthologues of the mammalian alpha2-adrenoceptors, while two genes code for alpha2Da- and alpha2Db- adrenoceptors, representing a duplicated, fourth alpha2-adrenoceptor subtype. The three different mammalian alpha2-adrenoceptor subtypes have distinct expression patterns in different organs and tissues, and mediate different physiological functions. The zebrafish alpha2-adrenergic system, with five different alpha2-adrenoceptors, appears more complicated. In order to deduce the physiological functions of the zebrafish alpha2-adrenoceptors, we localized the expression of the five different alpha2-adrenoceptor subtypes using RT-PCR, mRNA in situ hybridization, and receptor autoradiography using the radiolabelled alpha2-adrenoceptor antagonist [ethyl-3H]RS-79948-197. Localization of the alpha2A-, alpha2B- and alpha2C-adrenoceptors in zebrafish shows marked conservation when compared with mammals. The zebrafish alpha2A, alpha2Da, and alpha2Db each partially follow the distribution pattern of the mammalian alpha2A: a possible indication of subfunction partitioning between these subtypes. The alpha2-adrenergic system is functional in zebrafish also in vivo, as demonstrated by marked locomotor inhibition, similarly to mammals, and lightening of skin colour induced by the specific alpha2-adrenoceptor agonist, dexmedetomidine. Both effects were antagonized by the specific alpha2-adrenoceptor antagonist atipamezole.
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Affiliation(s)
- Jori O Ruuskanen
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Turku, Finland
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10
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Dygalo NN, Bannova AV, Kalinina TS, Shishkina GT. Clonidine increases caspase-3 mRNA level and DNA fragmentation in the developing rat brainstem. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 152:225-31. [PMID: 15351510 DOI: 10.1016/j.devbrainres.2004.06.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/29/2004] [Indexed: 11/15/2022]
Abstract
The densities of alpha2-adrenergic receptors, labeled by 3H-clonidine or 3H-RX821002, reach a peak in the rat brainstem during the first week of its life. This enables the agonist of alpha2-adrenergic receptor clonidine, which is used as a component of anaesthetic solution in infants and children, to have specific effects in this structure of the developing brain. Clonidine was injected into the fetal brain (5 microg in 5 microl of saline) or subcutaneously to the pups (1, 10 microg in 50 microl of saline) 3 days before investigation. Clonidine increased the level of apoptotic enzyme caspase-3 mRNA expression, as measured by RT-PCR and enhanced the DNA fragmentation, as determined by gel electrophoresis, in the brainstem of the 21-day-old fetuses and 8-day-old rats. In the cortex of 8-day-old rat, the alpha2-adrenergic receptors are at a much lower level than the brainstem. Clonidine treatment had no evident effects on caspase-3 mRNA level and DNA fragmentation in the cortex of an 8-day-old rat. The data suggest that clonidine facilitates cell death in the developing brainstem. This drug effect provides a potential mechanism whereby clonidine during early life could induce long-lasting alterations in brain neurochemistry, autonomic functions and behavior.
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MESH Headings
- Adrenergic alpha-Agonists/metabolism
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic alpha-Antagonists/metabolism
- Aging/metabolism
- Animals
- Animals, Newborn
- Binding, Competitive/drug effects
- Binding, Competitive/physiology
- Brain Stem/drug effects
- Brain Stem/growth & development
- Brain Stem/metabolism
- Caspase 3
- Caspases/genetics
- Cell Differentiation/drug effects
- Cell Differentiation/physiology
- Clonidine/metabolism
- Clonidine/pharmacology
- DNA Fragmentation/drug effects
- DNA Fragmentation/physiology
- Female
- Idazoxan/analogs & derivatives
- Idazoxan/metabolism
- Male
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/metabolism
- Up-Regulation/drug effects
- Up-Regulation/physiology
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Affiliation(s)
- Nikolai N Dygalo
- Functional Neurogenomics Laboratory, Institute of Cytology and Genetics, Russian Academy of Science, Lavrentjev av. 10, Novosibirsk 630090, Russia.
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Ozawa Y, Takashima S, Tada H. α2-Adrenergic receptor subtype alterations in the brainstem in the sudden infant death syndrome. PATHOPHYSIOLOGY 2004. [DOI: 10.1016/j.pathophys.2004.01.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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Ozawa Y, Takashima S, Tada H. Alpha2-adrenergic receptor subtype alterations in the brainstem in the sudden infant death syndrome. Early Hum Dev 2003; 75 Suppl:S129-38. [PMID: 14693399 DOI: 10.1016/j.earlhumdev.2003.08.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND The sudden infant death syndrome (SIDS) is still the main cause of postneonatal infant death. However, the causes and mechanisms of SIDS have never been completely elucidated. Catecholamines, via alpha2-adrenergic receptor (alpha2-AR) interactions, are known to influence brainstem autonomic and respiratory activity. AIMS To examine the catecholaminergic system abnormalities in SIDS victims, we investigated the alterations of alpha2-AR subtypes. SUBJECTS AND METHODS We examined the developmental changes of alpha2-AR subtypes in the brainstem, especially in cardiorespiratory nuclei, in 21 SIDS victims and 17 age-matched controls by means of immunohistochemical methods. For statistical analysis, the chi2-test or Fisher's exact probability test was performed. RESULTS There was a significant decrease in alpha2A-AR immunoreactivity in the solitary nucleus and ventrolateral medulla (VLM) in the medulla oblongata in SIDS victims compared with in control cases, but there were no significant differences of the alpha2B and alpha2C-AR immunoreactivity in the brainstem between SIDS victims and controls. CONCLUSION Alpha2A-AR immunoreactivity was selectively decreased in the solitary nucleus and VLM in the medulla oblongata in SIDS victims, so there was no possibility that it was secondary to chronic hypoxia or repeated ischemia. It may be related to some impairment of the cardiorespiratory neuronal system. Therefore, SIDS victims may be vulnerable to asphyxia, hypoxia, and/or hypercapnia, and fail to exhibit brainstem responses.
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Affiliation(s)
- Yuri Ozawa
- Department of Neonatology, Toho University School of Medicine, 6-11-1 Ohmorinishi, Ohta, Tokyo 143-8541, Japan.
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Zec N, Kinney HC. Anatomic relationships of the human nucleus of the solitary tract in the medulla oblongata: a DiI labeling study. Auton Neurosci 2003; 105:131-44. [PMID: 12798209 DOI: 10.1016/s1566-0702(03)00027-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The nucleus of the solitary tract (nTS) is a major site of brainstem control of vital functions (e.g., cardiovascular reflexes and respiration). We examined anatomic relationships of the human nucleus of the solitary tract, using a bidirectional lipophilic fluorescent tracer 1-1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) in 10 postmortem human fetal midgestational medullae oblongatae. Labeling by diffusion of DiI from the nucleus of the solitary tract included: (1) neuropil of all future subdivisions of the nucleus of the solitary tract ipsilateral to the DiI crystal; (2) stellate cells in the caudal raphe at the junction of the nucleus raphe pallidus and the arcuate nucleus at the ventral medullary surface, as well as single fibers along the caudal raphe and the arcuate nucleus; (3) cells and fibers in other medullary areas related to autonomic and respiratory control, including the dorsal motor nucleus of the vagus, nucleus ambiguus complex/ventral respiratory group, rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM), and medullary reticular formation. The pattern of connections of the nucleus of the solitary tract already established by midgestation in the human fetus is consistent with the pattern previously demonstrated in adult experimental animals. A major finding of the study is that of the stellate cells at the junction of nucleus raphe pallidus and the arcuate nucleus at the ventral medullary surface, which project to the nucleus of the solitary tract, and could be homologous to chemosensitive serotonergic neurons at the midline ventral medullary surface of experimental animals. This connection between the ventral caudal raphe and the nucleus of the solitary tract may participate in chemoreception and central regulation of cardiorespiratory reflexes during human perinatal development; it is, therefore, relevant to the study of sudden infant death syndrome (SIDS).
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Affiliation(s)
- Natasa Zec
- Department of Neurology, Children's Hospital and Harvard Medical School, 300 Longwood Avenue, Enders Building 206, Boston, MA 02115, USA
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Kinney HC, Filiano JJ, White WF. Medullary serotonergic network deficiency in the sudden infant death syndrome: review of a 15-year study of a single dataset. J Neuropathol Exp Neurol 2001; 60:228-47. [PMID: 11245208 DOI: 10.1093/jnen/60.3.228] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The sudden infant death syndrome (SIDS) is the leading cause of postneonatal infant mortality in the United States today, despite a dramatic 38% decrease in incidence due to a national risk reduction campaign advocating the supine sleep position. Our research in SIDS brainstems, beginning in 1985 and involving a single, large dataset, has become increasingly focused upon a specific neurotransmitter (serotonin) and specific territories (ventral medulla and regions of the medullary reticular formation that contain secrotonergic neurons). Based on this research, we propose that SIDS, or a subset of SIDS, is due to a developmental abnormality in a medullary network composed of (at least in part) rhombic lip-derived, serotonergic neurons, including in the caudal raphé and arcuate nucleus (putative human homologue of the cat respiratory chemosensitive fields); and this abnormality results in a failure of protective responses to life-threatening stressors (e.g. asphyxia, hypoxia, hypercapnia) during sleep as the infant passes through a critical period in homeostatic control. We call this the medullary serotonergic network deficiency hypothesis. We review the triple-risk model for SIDS, the development of the dataset using tissue autoradiography for analyzing neurotransmitter receptor binding; age-dependent baseline neurochemical findings in the human brainstem during early life; the evidence for serotonergic, rhombic lip, and ventral medullary deficits in at least some SIDS victim; possible mechanisms of sudden infant death related to these deficits; and potential causes of the deficits in the medullary serotonergic network in SIDS victims. We conclude with a summary of future directions in SIDS brainstem research.
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Affiliation(s)
- H C Kinney
- Department of Pathology, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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