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Haynes RL, Trachtenberg F, Darnall R, Haas EA, Goldstein RD, Mena OJ, Krous HF, Kinney HC. Altered 5-HT2A/C receptor binding in the medulla oblongata in the sudden infant death syndrome (SIDS): Part I. Tissue-based evidence for serotonin receptor signaling abnormalities in cardiorespiratory- and arousal-related circuits. J Neuropathol Exp Neurol 2023; 82:467-482. [PMID: 37226597 PMCID: PMC10209647 DOI: 10.1093/jnen/nlad030] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023] Open
Abstract
The sudden infant death syndrome (SIDS), the leading cause of postneonatal infant mortality in the United States, is typically associated with a sleep period. Previously, we showed evidence of serotonergic abnormalities in the medulla (e.g. altered serotonin (5-HT)1A receptor binding), in SIDS cases. In rodents, 5-HT2A/C receptor signaling contributes to arousal and autoresuscitation, protecting brain oxygen status during sleep. Nonetheless, the role of 5-HT2A/C receptors in the pathophysiology of SIDS is unclear. We hypothesize that in SIDS, 5-HT2A/C receptor binding is altered in medullary nuclei that are key for arousal and autoresuscitation. Here, we report altered 5-HT2A/C binding in several key medullary nuclei in SIDS cases (n = 58) compared to controls (n = 12). In some nuclei the reduced 5-HT2A/C and 5-HT1A binding overlapped, suggesting abnormal 5-HT receptor interactions. The data presented here (Part 1) suggest that a subset of SIDS is due in part to abnormal 5-HT2A/C and 5-HT1A signaling across multiple medullary nuclei vital for arousal and autoresuscitation. In Part II to follow, we highlight 8 medullary subnetworks with altered 5-HT receptor binding in SIDS. We propose the existence of an integrative brainstem network that fails to facilitate arousal and/or autoresuscitation in SIDS cases.
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Affiliation(s)
- Robin L Haynes
- CJ Murphy Laboratory for SIDS Research, Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
- Robert’s Program on Sudden Unexpected Death in Pediatrics, Division of General Pediatrics, Department of Pediatrics, Boston Children’s Hospital, Boston, Massachusetts, USA
| | | | - Ryan Darnall
- CJ Murphy Laboratory for SIDS Research, Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Elisabeth A Haas
- Department of Research, Rady Children’s Hospital, San Diego, California, USA
| | - Richard D Goldstein
- Robert’s Program on Sudden Unexpected Death in Pediatrics, Division of General Pediatrics, Department of Pediatrics, Boston Children’s Hospital, Boston, Massachusetts, USA
- Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Othon J Mena
- San Diego County Medical Examiner Office, San Diego, California, USA
| | - Henry F Krous
- University of California, San Diego, San Diego, California, USA
- Rady Children’s Hospital, San Diego, California, USA
| | - Hannah C Kinney
- CJ Murphy Laboratory for SIDS Research, Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
- Robert’s Program on Sudden Unexpected Death in Pediatrics, Division of General Pediatrics, Department of Pediatrics, Boston Children’s Hospital, Boston, Massachusetts, USA
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Spinieli RL, Cornelius-Green J, Cummings KJ. A serotonin-deficient rat model of neurogenic hypertension: influence of sex and sympathetic vascular tone. J Neurophysiol 2022; 128:1199-1206. [PMID: 36169206 PMCID: PMC9621705 DOI: 10.1152/jn.00358.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/22/2022] [Accepted: 09/26/2022] [Indexed: 11/22/2022] Open
Abstract
Previously we showed that a loss of central nervous system (CNS) 5-hydroxytryptamine (5-HT) (tryptophan hydroxylase 2 knockout; TPH2-/-) leads to hypertension in male rats during wakefulness and REM sleep. Here, we tested the hypotheses that hypertension is also revealed in female TPH2-/- when sex hormones are controlled, and that the especially high arterial blood pressure (ABP) of male TPH2-/- rats is due to increased sympathetic vascular tone. The ABP of females was measured specifically during proestrus or estrus and again following ovariectomy. The ABP of males was measured before and after α-adrenergic blockade. Prior to ovariectomy, the ABP of female TPH2-/- rats was ∼3 mmHg higher than TPH2+/+ during REM sleep while in proestrus/estrus. This difference increased to ∼9 mmHg following ovariectomy (P = 0.047). Hypertension of female TPH2-/- was most obvious upon the transition to rapid eye movement (REM) sleep from the previous state (P < 0.0001). Mean arterial pressure (MAP) of male TPH2-/- rats was ∼14 mmHg higher than male TPH2+/+ (P = 0.02), a difference that was eliminated by α-adrenergic blockade. Male TPH2-/- had normal plasma levels of 5-HT, norepinephrine, and epinephrine, whereas plasma dopamine was reduced by 50% compared with TPH2+/+ (P < 0.0001). From these data, we conclude that: 1) a deficiency of CNS 5-HT leads to hypertension in males and females alike, although in females the effect is mild and possibly obscured by ovarian hormones; 2) hypertension in females, like males, is most apparent in REM sleep, indicating a neural origin, and 3) increased sympathetic vascular tone underlies the elevated ABP of TPH2-/- rats.NEW & NOTEWORTHY We show that hypertension is evident in female 5-HT-deficient TPH2-/- rats when sex hormones are controlled, an effect most evident upon the transition to REM sleep. In addition, our data strongly suggest that increased sympathetic vascular tone contributes to the hypertension present in this 5-HT-deficient model of neurogenic hypertension.
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Affiliation(s)
- Richard L Spinieli
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Jennifer Cornelius-Green
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Kevin J Cummings
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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3
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Vandenbeuch A, Wilson CE, Kinnamon SC. Optogenetic Activation of Type III Taste Cells Modulates Taste Responses. Chem Senses 2021; 45:533-539. [PMID: 32582939 DOI: 10.1093/chemse/bjaa044] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Studies have suggested that communication between taste cells shapes the gustatory signal before transmission to the brain. To further explore the possibility of intragemmal signal modulation, we adopted an optogenetic approach to stimulate sour-sensitive (Type III) taste cells using mice expressing Cre recombinase under a specific Type III cell promoter, Pkd2l1 (polycystic kidney disease-2-like 1), crossed with mice expressing Cre-dependent channelrhodopsin (ChR2). The application of blue light onto the tongue allowed for the specific stimulation of Type III cells and circumvented the nonspecific effects of chemical stimulation. To understand whether taste modality information is preprocessed in the taste bud before transmission to the sensory nerves, we recorded chorda tympani nerve activity during light and/or chemical tastant application to the tongue. To assess intragemmal modulation, we compared nerve responses to various tastants with or without concurrent light-induced activation of the Type III cells. Our results show that light significantly decreased taste responses to sweet, bitter, salty, and acidic stimuli. On the contrary, the light response was not consistently affected by sweet or bitter stimuli, suggesting that activation of Type II cells does not affect nerve responses to stimuli that activate Type III cells.
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Affiliation(s)
- Aurelie Vandenbeuch
- Department of Otolaryngology and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
| | - Courtney E Wilson
- Department of Otolaryngology and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
| | - Sue C Kinnamon
- Department of Otolaryngology and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
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Wei R, Gust SL, Tandio D, Maheux A, Nguyen KH, Wang J, Bourque S, Plane F, Hammond JR. Deletion of murine slc29a4 modifies vascular responses to adenosine and 5-hydroxytryptamine in a sexually dimorphic manner. Physiol Rep 2021; 8:e14395. [PMID: 32170814 PMCID: PMC7070170 DOI: 10.14814/phy2.14395] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/18/2020] [Accepted: 02/19/2020] [Indexed: 12/15/2022] Open
Abstract
Equilibrative nucleoside transporter 4 (ENT4), encoded by SLC29A4, mediates the flux of both 5‐hydroxytryptamine (5‐HT) and adenosine across cell membranes. We hypothesized that loss of ENT4 function in mice would modify the effects of these established regulators of vascular function. Male and female wild‐type (WT) and slc29a4‐null (ENT4‐KO) mice were compared with respect to their hemodynamics and mesenteric vascular function. Male ENT4‐KO mice had a complete loss of myogenic tone in their mesenteric resistance arteries. This was accompanied by a decrease in blood flow in the superior mesenteric artery in the male ENT4‐KO mice, and a reduced responsiveness to 5‐HT. In contrast, endothelium‐dependent relaxations of mesenteric arteries from female ENT4‐KO mice were more sensitive to Ca2+‐activated K+ (KCa) channel blockade than WT mice. Female ENT4‐KO mice also demonstrated an enhanced vasodilatory response to adenosine in vivo that was not seen in males. Ketanserin (5‐HT2A inhibitor) and GR55562 (5‐HT1B/1D inhibitor) decreased 5‐HT‐induced tone, but only ketanserin inhibited the relaxant effect of 5‐HT in mesenteric arteries. 5‐HT‐evoked increases in tone were elevated in arteries from ENT4‐KO mice upon block of endothelial relaxant pathways, with arteries from female ENT4‐KO mice showing the greatest increase. Adenosine A2b receptor expression was decreased, while other adenosine transporter subtypes, as well as adenosine deaminase and adenosine kinase were increased in mesenteric arteries from male, but not female, ENT4‐KO mice. These findings indicate that deletion of slc29a4 leads to sex‐specific changes in vascular function with significant consequences for regulation of blood flow and pressure by adenosine and 5‐HT.
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Affiliation(s)
- Ran Wei
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Stephen L Gust
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - David Tandio
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Alexia Maheux
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Khanh H Nguyen
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Joanne Wang
- Department of Pharmaceutics, University of Washington, Seattle, WA, USA
| | - Stephane Bourque
- Department of Anaesthesia and Pain Medicine, University of Alberta, Edmonton, AB, Canada
| | - Frances Plane
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - James R Hammond
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
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Podlewska S, Bugno R, Lacivita E, Leopoldo M, Bojarski AJ, Handzlik J. Low Basicity as a Characteristic for Atypical Ligands of Serotonin Receptor 5-HT2. Int J Mol Sci 2021; 22:ijms22031035. [PMID: 33494248 PMCID: PMC7864501 DOI: 10.3390/ijms22031035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/15/2021] [Accepted: 01/16/2021] [Indexed: 02/07/2023] Open
Abstract
Serotonin receptors are extensively examined by academic and industrial researchers, due to their vital roles, which they play in the organism and constituting therefore important drug targets. Up to very recently, it was assumed that the basic nitrogen in compound structure is a necessary component to make it active within this receptor system. Such nitrogen interacts in its protonated form with the aspartic acid from the third transmembrane helix (D3x32) forming a hydrogen bond tightly fitting the ligand in the protein binding site. However, there are several recent studies that report strong serotonin receptor affinity also for compounds without a basic moiety in their structures. In the study, we carried out a comprehensive in silico analysis of the low-basicity phenomenon of the selected serotonin receptor ligands. We focused on the crystallized representatives of the proteins of 5-HT1B, 5-HT2A, 5-HT2B, and 5-HT2C receptors, and examined the problem both from the ligand- and structure-based perspectives. The study was performed for the native proteins, and for D3x32A mutants. The investigation resulted in the determination of nonstandard structural requirements for activity towards serotonin receptors, which can be used in the design of new nonbasic ligands.
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Affiliation(s)
- Sabina Podlewska
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Kraków, Poland
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
- Correspondence: (S.P.); (J.H.); Tel.: +48-12-66-23-301 (S.P.); +48-12-620-55-84 (J.H.)
| | - Ryszard Bugno
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
| | - Enza Lacivita
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, via E. Orabona 4, 70125 Bari, Italy; (E.L.); (M.L.)
| | - Marcello Leopoldo
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, via E. Orabona 4, 70125 Bari, Italy; (E.L.); (M.L.)
| | - Andrzej J. Bojarski
- Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343 Kraków, Poland; (R.B.); (A.J.B.)
| | - Jadwiga Handzlik
- Department of Technology and Biotechnology of Drugs, Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna Street, 30-688 Kraków, Poland
- Correspondence: (S.P.); (J.H.); Tel.: +48-12-66-23-301 (S.P.); +48-12-620-55-84 (J.H.)
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Magnusson JL, Emter CA, Cummings KJ. Sex- and age-based differences in the effect of central serotonin on arterial blood pressure regulation. J Appl Physiol (1985) 2020; 129:1310-1323. [PMID: 32909922 DOI: 10.1152/japplphysiol.00414.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Medullary serotonin (5-hydroxytryptamine; 5-HT) neurons project to multiple autonomic nuclei in the central nervous system (CNS). Infant rats lacking 5-HT have low arterial blood pressure (ABP) in quiet sleep, but the role of 5-HT in ABP regulation across vigilance states in adults has not been studied. We hypothesized that in adults, CNS 5-HT deficiency leads to hypotension mainly in quiet wakefulness (QW) and non-rapid eye movement (NREM) sleep, when 5-HT neurons are active. We tested male and female tryptophan hydroxylase 2 knockout rats (TPH2-/-), specifically deficient in CNS 5-HT, and wild-type (TPH2+/+) controls at 2-3, 5-8, and 12-13 mo of age. Compared with TPH2+/+, mean arterial pressure of 5-8- and 12-13-mo-old (middle-aged) male TPH2-/- rats was significantly elevated (∼10 mmHg) in QW and rapid eye movement (REM) sleep. Middle-aged male TPH2-/- rats also had more frequent extreme hypertensive events during prolonged episodes of REM sleep. Female TPH2-/- had normal ABP. The low- and very-low-frequency components of systolic ABP variability were significantly higher in middle-aged male, but not female, TPH2-/- rats compared with in TPH2+/+ rats, suggesting elevated sympathetic vascular tone in male TPH2-/- rats. However, the hypertension of male TPH2-/- rats was not ameliorated by ganglionic blockade. Hearts and lungs of middle-aged male TPH2-/- rats were significantly heavier than those of TPH2+/+ rats. We show that a loss of CNS 5-HT leads to high ABP only in middle-aged males during wakefulness and REM sleep, possibly due to increased vascular tone. It should be investigated whether elevated ventricular afterload associated with CNS 5-HT deficiency initiates cardiac remodeling or alters pulmonary hemodynamics.NEW & NOTEWORTHY The role of serotonin in arterial blood pressure (ABP) regulation across states of vigilance is unknown. We hypothesized that adult rats devoid of CNS serotonin (TPH2-/-) have low ABP in wakefulness and NREM sleep, when serotonin neurons are active. However, TPH2-/- rats experience higher ABP than TPH2+/+ rats in wakefulness and REM only, a phenotype present only in older males and not females. CNS serotonin may be critical for preventing high ABP in males with aging.
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Affiliation(s)
- Jennifer L Magnusson
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
| | - Craig A Emter
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
| | - Kevin J Cummings
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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Szőke H, Kovács Z, Bókkon I, Vagedes J, Szabó AE, Hegyi G, Sterner MG, Kiss Á, Kapócs G. Gut dysbiosis and serotonin: intestinal 5-HT as a ubiquitous membrane permeability regulator in host tissues, organs, and the brain. Rev Neurosci 2020; 31:415-425. [DOI: 10.1515/revneuro-2019-0095] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/16/2019] [Indexed: 12/12/2022]
Abstract
AbstractThe microbiota and microbiome and disruption of the gut-brain axis were linked to various metabolic, immunological, physiological, neurodevelopmental, and neuropsychiatric diseases. After a brief review of the relevant literature, we present our hypothesis that intestinal serotonin, produced by intestinal enterochromaffin cells, picked up and stored by circulating platelets, participates and has an important role in the regulation of membrane permeability in the intestine, brain, and other organs. In addition, intestinal serotonin may act as a hormone-like continuous regulatory signal for the whole body, including the brain. This regulatory signal function is mediated by platelets and is primarily dependent on and reflects the intestine’s actual health condition. This hypothesis may partially explain why gut dysbiosis could be linked to various human pathological conditions as well as neurodevelopmental and neuropsychiatric disorders.
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Affiliation(s)
- Henrik Szőke
- Department of CAM, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
- Doctorate School, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
| | - Zoltán Kovács
- Doctorate School, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
| | - István Bókkon
- Vision Research Institute, Neuroscience and Consciousness Research Department, Lowell, MA, USA
- Psychosomatic Outpatient Clinics, Budapest, Hungary
| | - Jan Vagedes
- University of Tübingen, Children’s Hospital, Tübingen, Germany
- ARCIM Institute (Academic Research in Complementary and Integrative Medicine), Filderstadt, Germany
| | | | - Gabriella Hegyi
- Department of CAM, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
- Doctorate School, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
| | | | - Ágnes Kiss
- Doctorate School, Faculty of Health Sciences, University of Pécs, Pécs, Hungary
| | - Gábor Kapócs
- Buda Family-Centered Mental Health Centre, Department of Psychiatry and Psychiatric Rehabilitation, Teaching Department of Semmelweis University, New Saint John Hospital, Budapest, Hungary
- Institute for Behavioral Sciences, Semmelweis University, Budapest, Hungary
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Davis MR, Magnusson JL, Cummings KJ. Increased central cholinergic drive contributes to the apneas of serotonin-deficient rat pups during active sleep. J Appl Physiol (1985) 2019; 126:1175-1183. [PMID: 30763168 DOI: 10.1152/japplphysiol.00909.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Infant rat pups lacking central nervous system (CNS) serotonin (5-hydroxytryptamine; 5-HT) have unstable breathing during prolonged periods of active sleep. Given that cholinergic neurons are drivers of active sleep and project to respiratory patterning regions in the brainstem, we hypothesized that 5-HT preserves respiratory stability in active sleep by dampening central cholinergic drive. We used whole-body plethysmography coupled with nuchal electromyography to monitor the breathing pattern of 2-wk-old tryptophan hydroxylase 2 (TPH2)+/+ and TPH2-deficient (TPH2-/-) pups in active sleep, before and after muscarinic blockade. For the group 1 experiment we injected methylatropine (Ap-M), a CNS-impermeant form of atropine, followed ~30 min later by an injection of atropine sulfate (Ap-S), the CNS-permeant form (both 1 mg/kg, 10 μl bolus iv); both injections occurred within an active sleep episode. We analyzed the effect of each drug on the coefficient of variation of the respiratory period (CV-P) during active sleep. For the group 2 experiment rats were cycled through several episodes of active and quiet sleep before administration of Ap-S (1 mg/kg, 200 μl ip) or vehicle. We assessed the effect of Ap-S on the apnea indices of both genotypes during quiet and active sleep. In group 1 Ap-S significantly reduced the CV-P of TPH2-/- pups (P = 0.03), an effect not observed in TPH2+/+ pups or following Ap-M. In group 2 the apnea index of TPH2-/- pups was significantly reduced following Ap-S injection (P = 0.04), whereas the apnea index of TPH2+/+ littermates was unaffected (P = 0.58). These findings suggest that central 5-HT reduces apnea and stabilizes breathing by reducing cholinergic signaling through muscarinic receptors. NEW & NOTEWORTHY Serotonin in the central nervous system (CNS) is necessary for maintaining the stability of breathing in the early postnatal period, particularly during active sleep. Here we show that the administration of atropine to the CNS selectively stabilizes the respiratory pattern of tryptophan hydroxylase 2-deficient rat pups and reduces their apneas. This suggests that CNS serotonin stabilizes breathing at least in part by reducing central cholinergic drive.
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Affiliation(s)
- Marina R Davis
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
| | - Jennifer L Magnusson
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
| | - Kevin J Cummings
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
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Dosumu-Johnson RT, Cocoran AE, Chang Y, Nattie E, Dymecki SM. Acute perturbation of Pet1-neuron activity in neonatal mice impairs cardiorespiratory homeostatic recovery. eLife 2018; 7:37857. [PMID: 30350781 PMCID: PMC6199134 DOI: 10.7554/elife.37857] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 09/09/2018] [Indexed: 12/02/2022] Open
Abstract
Cardiorespiratory recovery from apneas requires dynamic responses of brainstem circuitry. One implicated component is the raphe system of Pet1-expressing (largely serotonergic) neurons, however their precise requirement neonatally for homeostasis is unclear, yet central toward understanding newborn cardiorespiratory control and dysfunction. Here we show that acute in vivo perturbation of Pet1-neuron activity, via triggering cell-autonomously the synthetic inhibitory receptor hM4Di, resulted in altered baseline cardiorespiratory properties and diminished apnea survival. Respiratory more than heart rate recovery was impaired, uncoupling their normal linear relationship. Disordered gasp recovery from the initial apnea distinguished mice that would go on to die during subsequent apneas. Further, the risk likelihood of apnea-related mortality associated with suppression of Pet1 neurons was higher for animals with baseline elevated ventilatory equivalents for oxygen. These findings establish that Pet1 neurons play an active role in neonatal cardiorespiratory homeostasis and provide mechanistic plausibility for the serotonergic abnormalities associated with SIDS. Our survival depends on our heart and lungs working together to supply our cells with oxygen and remove carbon dioxide waste. The brain coordinates this process by controlling the activity of the heart and lungs. Yet sometimes a person may experience an event called an apnea and briefly stop breathing. If this happens, oxygen levels in the body fall while carbon dioxide levels rise. This in turn triggers a recovery process called autoresuscitation, which includes a series of large breaths or gasps, and each gasp is accompanied by increased heart rate due to specialized parts of the nervous system. This response usually restores normal breathing. Failure of autoresuscitation may underlie many cases of sudden infant death syndrome, or SIDS (also known as “cot death” or “crib death”). SIDS is the leading cause of death in young infants in the western world, and many infants who die from SIDS show abnormalities in the brain cells that produce a chemical called serotonin. Evidence suggests that serotonin helps control breathing. This raised the question: does the autoresuscitation recovery response rely on serotonin-producing neurons? To find out, Dosumu-Johnson et al. used one-week-old mouse pups that had been genetically engineered to respond to an injected drug by rapidly inhibiting their serotonin neurons. These animals are about the same age in mouse terms as infants at greatest risk for SIDS (~2-4 months of age). Inhibiting serotonin neurons made it harder for the mouse pups to recover from artificially induced apneas. Although their heart rate showed largely normal recovery – at least at first – their breathing did not. They took fewer gasps, and were more likely to die following such episodes. These findings shed new light on how young animals control their breathing and heart rate when mounting an autoresuscitation recovery from an apnea. The observed uncoupling of breathing and heart rate recovery responses suggests that different brain cells and circuits control the two. The results also suggest that abnormalities in the activity of serotonin neurons may make infants more susceptible to SIDS. As well as offering a possible explanation to families who have lost a child to SIDS, these findings could be used to develop screening tools to identify other infants at risk. They also point to potential cellular targets for drugs that could ultimately help prevent further cases.
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Affiliation(s)
| | - Andrea E Cocoran
- Department of Molecular & Systems Biology, The Geisel School of Medicine at Dartmouth, Hanover, United States
| | - YoonJeung Chang
- Department of Genetics, Harvard Medical School, Boston, United States
| | - Eugene Nattie
- Department of Molecular & Systems Biology, The Geisel School of Medicine at Dartmouth, Hanover, United States
| | - Susan M Dymecki
- Department of Genetics, Harvard Medical School, Boston, United States
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