1
|
Sithirungson S, Sonsuwan N, Chattipakorn SC, Chattipakorn N, Shinlapawittayatorn K. Functional roles of orexin in obstructive sleep apnea: From clinical observation to mechanistic insights. Sleep Med 2023; 101:40-49. [PMID: 36334500 DOI: 10.1016/j.sleep.2022.10.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 09/23/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
Obstructive sleep apnea is the most common sleep-related breathing disorder. Repetitive episodes of the obstructive respiratory events lead to arousal, sleep fragmentation, and excessive daytime sleepiness. Orexin, also known as hypocretin, is one of the most important neurotransmitters responsible for sleep and arousal regulation. Deficiency of orexin has been shown to be involved in the pathogenesis of narcolepsy, which shares cardinal symptoms of sleep apnea and excessive daytime sleep with obstructive sleep apnea. However, the relationship between orexin and obstructive sleep apnea is not well defined. In this review, we summarize the current evidence, from in vitro, in vivo, and clinical data, regarding the association between orexin and obstructive sleep apnea. The effects of orexin on sleep apnea, as well as how the consequences of obstructive sleep apnea affect the orexin system function are also discussed. Additionally, the contrary findings are also included and discussed.
Collapse
Affiliation(s)
- Suchanya Sithirungson
- Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - Nuntigar Sonsuwan
- Department of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - Siriporn C Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand; Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - Nipon Chattipakorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand; Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, 50200, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand
| | - Krekwit Shinlapawittayatorn
- Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand; Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University, Chiang Mai, 50200, Thailand; Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
| |
Collapse
|
2
|
Sobrinho CR, Milla BM, Soto-Perez J, Moreira TS, Mulkey DK. Histamine/H1 receptor signaling in the parafacial region increases activity of chemosensitive neurons and respiratory activity in rats. J Neurophysiol 2022; 128:218-228. [PMID: 35704395 DOI: 10.1152/jn.00015.2022] [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
Histaminergic neurons of the tuberomammillary nucleus (TMN) are pH-sensitive and contribute to CO2/H+-dependent behaviors including arousal and respiratory activity. TMN neurons project to several respiratory centers including the ventral parafacial region (pF) where chemosensitive retrotrapezoid (RTN) neurons are located, and since RTN neurons are an important source of CO2/H+-dependent respiratory drive, we wondered whether histamine contributes to RTN chemoreception. To test this, we characterized effects of histamine on mean arterial pressure (MAP) and diaphragm muscle activity (DIAEMG) in urethane-anaesthetized, vagotomized and artificially ventilated male Wistar rats. Unilateral injection of histamine (25 mM) in the pF increased DIAEMG amplitude without changing DIAEMG frequency and MAP. Bilateral pF injections of the H1 receptor antagonist diphenhydramine hydrochloride (DPH; 0.5 mM) decreased baseline DIAEMG amplitude and frequency and MAP. Despite the strong inhibitory effect of DPH on baseline breathing, the hypercapnic ventilatory response was preserved under these experimental conditions. At the cellular level, chemosensitive RTN neurons showed a dose-dependent excitatory response to histamine that was blunted by DPH and mimicked by the H1 receptor agonist 2-pyridylethylamine dihydrochloride (2PYEA) under both control conditions and when fast neurotransmitter receptors are blocked. We also tested effects of 2PYEA in the presence of serotonin, another wake-on neurotransmitter that activates RTN chemoreceptors partly by activation of Gq-coupled receptors. We found the response to 2PYEA was diminished in serotonin, suggesting RTN neurons have a limited capacity to respond to multiple Gq-coupled modulators. These results suggest histamine can modulate breathing at the pF level by a mechanism involving H1 receptors.
Collapse
Affiliation(s)
- Cleyton R Sobrinho
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, Brazil.,Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| | - Brenda M Milla
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| | - Jaseph Soto-Perez
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, Brazil
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| |
Collapse
|
3
|
Sergeeva OA, Mazur K, Kernder A, Haas HL, De Luca R. Tachykinins amplify the action of capsaicin on central histaminergic neurons. Peptides 2022; 150:170729. [PMID: 34958850 DOI: 10.1016/j.peptides.2021.170729] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 11/27/2021] [Accepted: 12/23/2021] [Indexed: 12/30/2022]
Abstract
Substance P (SP), a product of the tachykinin 1 (Tac1) gene, is expressed in many hypothalamic neurons. Its wake-promoting potential could be mediated through histaminergic (HA) neurons of the tuberomamillary nucleus (TMN), where functional expression of neurokinin receptors (NKRs) waits to be characterized. As in the process of nociception in the peripheral nervous system (PNS) capsaicin-receptor (transient potential vanilloid 1: TRPV1) signalling is amplified by local release of histamine and SP, we tested the involvement of tachykinins in the capsaicin-induced long-lasting enhancement (LLEcaps) of HA neurons firing by investigating selective neurokinin receptor ligands in the hypothalamic mouse brain slice preparation using patch-clamp recordings in cell-attached mode combined with single-cell RT-PCR. We report that the majority of HA neurons respond to SP (EC50 3 nM), express the SP precursor tachykinin 1 (Tac1) gene and at least one of the neurokinin receptors. Responses to selective agonists of three known neurokinin receptors were sensitive to corresponding antagonists. LLEcaps was significantly impaired by the neurokinin receptor antagonists, indicating that in hypothalamus, as in the PNS, release of tachykinins downstream to TRPV1 activation is able to boost the release of histamine. The excitatory action of SP on histaminergic neurons adds another pathway to the noradrenergic and orexinergic ones to synergistically enhance cortical arousal. We show NK1R to play a prominent role on HA neurons and thus the control of wakefulness.
Collapse
Affiliation(s)
- O A Sergeeva
- Institute of Clinical Neuroscience and Medical Psychology (ICNMP), Group of Molecular Neurophysiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany; Institute of Neural and Sensory Physiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany.
| | - K Mazur
- Institute of Clinical Neuroscience and Medical Psychology (ICNMP), Group of Molecular Neurophysiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany
| | - A Kernder
- Institute of Neural and Sensory Physiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany
| | - H L Haas
- Institute of Neural and Sensory Physiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany
| | - R De Luca
- Institute of Neural and Sensory Physiology, Heinrich-Heine-University, Medical Faculty, D-40225, Düsseldorf, Germany
| |
Collapse
|
4
|
Plancoulaine S, Guyon A, Inocente CO, Germe P, Zhang M, Robert P, Lin JS, Franco P. Cerebrospinal Fluid Histamine Levels in Healthy Children and Potential Implication for SIDS: Observational Study in a French Tertiary Care Hospital. Front Pediatr 2022; 10:819496. [PMID: 35450108 PMCID: PMC9016218 DOI: 10.3389/fped.2022.819496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 03/09/2022] [Indexed: 12/02/2022] Open
Abstract
OBJECTIVE A defect of the waking systems could constitute a factor of vulnerability for sudden infant death syndrome (SIDS). A decrease in orexin levels, which promotes wakefulness and activates histaminergic neurons (another hypothalamic wake-promoting system) has already been demonstrated between 2 and 6 months. This work aims to study the levels of histamine (HA), tele-methylhistamine (t-MeHA), its direct metabolite, and t-MeHA/HA ratio in the cerebrospinal fluid (CSF) of healthy children, to evaluate the maturation of the histaminergic system and its possible involvement in SIDS. METHODS Seventy Eight French children between 0 and 20 years (48.7% boys) were included, all of whom had a clinical indication for lumbar puncture, but subsequently found to be normal. Measurements of HA and t-MeHA in CSF were performed by reverse phase liquid chromatography coupled to mass spectrometry detection. Statistical analyses were performed using Spearman correlations and Non-parametric pairwise ranking tests. RESULTS A negative correlation was found between age and CSF HA (r = -0.44, p < 10-4) and t-MeHA (r = -0.70, p < 10-4) levels. In pairwise comparisons, no difference in CSF HA and t-MeHA levels was observed between youngest age groups (i.e., 0-2 mo vs. 3-6 mo), but CSF HA and t-MeHA levels were significantly lower in older children (i.e., >6 mo vs. 0-6 mo). The CSF HA decrease with age was only observed in boys, who also presented global lower CSF HA levels than girls. CONCLUSION CSF HA and t-MeHA levels decrease with age in boys, and global levels are lower in boys than in girls. These results reveal changes in histaminergic transmission and metabolism during maturation. Whether lower CSF histamine values in boys compared to girls could contribute to their higher risk of SIDS warrants further research.
Collapse
Affiliation(s)
| | - Aurore Guyon
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France.,Bioprojet Biotech, Saint-Grégoire, France
| | - Clara-Odilia Inocente
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France
| | - Philippine Germe
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France
| | - Min Zhang
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France
| | | | - Jian-Sheng Lin
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France
| | - Patricia Franco
- Integrative Physiology of the Brain Arousal System, CRNL, INSERM-U1028, CNRS UMR5292, University Lyon 1, Lyon, France.,Pediatric Sleep Unit, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, University Lyon 1, Lyon, France
| |
Collapse
|
5
|
Different Peas in the Same Pod: The Histaminergic Neuronal Heterogeneity. Curr Top Behav Neurosci 2021; 59:303-327. [PMID: 34455575 DOI: 10.1007/7854_2021_241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The histaminergic neuronal system is recently receiving increasing attention, as much has been learned over the past 25 years about histamine role as a neurotransmitter. Indeed, this amine is crucial in maintaining arousal and provides important contributions to regulate circadian rhythms, energy, endocrine homeostasis, motor behavior, and cognition. The extent to which these distinct physiological functions are operated by independent histamine neuronal subpopulation is unclear. In the rat brain histamine neuronal cell bodies are grouped within the tuberomamillary nucleus of the posterior hypothalamus in five clusters, E1-E5, each sending overlapping axons throughout the entire central nervous system with no strict topographical pattern. These features lead to the concept that histamine regulation of a wide range of functions in the central nervous system is achieved by the histaminergic neuronal system as a whole. However, increasing experimental evidence suggesting that the histaminergic system is organized into distinct pathways modulated by selective mechanisms challenges this view. In this review, we summarized experimental evidence supporting the heterogeneity of histamine neurons, and their organization in functionally distinct circuits impinging on separate brain regions and displaying selective control mechanisms. This implies independent functions of subsets of histaminergic neurons according to their respective origin and terminal projections with relevant consequences for the development of specific compounds that affect only subsets of histamine neurons, thus increasing the target specificity.
Collapse
|
6
|
Kansagra S, Ghusayni R, Kherallah B, Gunduz T, McLean M, Prange L, Kravitz RM, Mikati MA. Polysomnography Findings and Sleep Disorders in Children With Alternating Hemiplegia of Childhood. J Clin Sleep Med 2019; 15:65-70. [PMID: 30621840 DOI: 10.5664/jcsm.7572] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/06/2018] [Indexed: 01/03/2023]
Abstract
STUDY OBJECTIVES Patients with alternating hemiplegia of childhood (AHC) experience bouts of hemiplegia and other paroxysmal spells that resolve during sleep. Patients often have multiple comorbidities that could negatively affect sleep, yet sleep quality and sleep pathology in AHC are not well characterized. This study aimed to report sleep data from both polysomnography (PSG) and clinical evaluations in children with AHC. METHODS We analyzed nocturnal PSG and clinical sleep evaluation results of a cohort of 22 consecutive pediatric patients with AHC who were seen in our AHC multidisciplinary clinic and who underwent evaluations according to our comprehensive AHC clinical pathway. This pathway includes, regardless of presenting symptoms, baseline PSG and evaluation by a board-certified pediatric sleep specialist. RESULTS Out of 22 patients, 20 had at least one type of sleep problem. Six had obstructive sleep apnea as documented on polysomnogram, of whom two had no prior report of sleep-disordered breathing symptoms. Patients had abnormal mean overall apnea-hypopnea index of 5.8 (range 0-38.7) events/h and an abnormal mean arousal index of 15.0 (range 4.8-46.6) events/h. Based on sleep history, 16 patients had difficulty falling asleep, staying asleep, or both; 9 had behavioral insomnia of childhood; and 2 had delayed sleep-wake phase syndrome. CONCLUSIONS Sleep dysfunction is common among children with AHC. Physicians should routinely screen for sleep pathology, with a low threshold to obtain a nocturnal PSG.
Collapse
Affiliation(s)
- Sujay Kansagra
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Ryan Ghusayni
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Bassil Kherallah
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Talha Gunduz
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Melissa McLean
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Lyndsey Prange
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Richard M Kravitz
- Division of Pediatric Pulmonary and Sleep Medicine, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| | - Mohamad A Mikati
- Division of Pediatric Neurology, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina
| |
Collapse
|
7
|
De Luca R, Mazur K, Kernder A, Suvorava T, Kojda G, Haas HL, Sergeeva OA. Mechanisms of N-oleoyldopamine activation of central histaminergic neurons. Neuropharmacology 2018; 143:327-338. [DOI: 10.1016/j.neuropharm.2018.09.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 08/30/2018] [Accepted: 09/07/2018] [Indexed: 12/18/2022]
|
8
|
Tarasiuk A, Segev Y. Abnormal Growth and Feeding Behavior in Upper Airway Obstruction in Rats. Front Endocrinol (Lausanne) 2018; 9:298. [PMID: 29915561 PMCID: PMC5994397 DOI: 10.3389/fendo.2018.00298] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/18/2018] [Indexed: 12/18/2022] Open
Abstract
Pediatric obstructive sleep apnea (OSA) is a syndrome manifesting with snoring and increased respiratory effort due to increased upper airway resistance. In addition to cause the abnormal sleep, this syndrome has been shown to elicit either growth retardation or metabolic syndrome and obesity. Treating OSA by adenotonsillectomy is usually associated with increased risk for obesity, despite near complete restoration of breathing and sleep. However, the underlying mechanism linking upper airways obstruction (AO) to persistent change in food intake, metabolism, and growth remains unclear. Rodent models have examined the impact of intermittent hypoxia on metabolism. However, an additional defining feature of OSA that is not related to intermittent hypoxia is enhanced respiratory loading leading to increased respiratory effort and abnormal sleep. The focus of this mini review is on recent evidence indicating the persistent abnormalities in endocrine regulation of feeding and growth that are not fully restored by the chronic upper AO removal in rats. Here, we highlight important aspects related to abnormal regulation of metabolism that are not related to intermittent hypoxia per se, in an animal model that mimics many of the clinical features of pediatric OSA. Our evidence from the AO model indicates that obstruction removal may not be sufficient to prevent the post-removal tendency for abnormal growth.
Collapse
Affiliation(s)
- Ariel Tarasiuk
- Sleep-Wake Disorders Unit, Soroka University Medical Center, Beer-Sheva, Israel
- Department of Physiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
- *Correspondence: Ariel Tarasiuk,
| | - Yael Segev
- Shraga Segal Department of Microbiology and Immunology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| |
Collapse
|
9
|
Dergacheva O, Yamanaka A, Schwartz AR, Polotsky VY, Mendelowitz D. Hypoxia and hypercapnia inhibit hypothalamic orexin neurons in rats. J Neurophysiol 2016; 116:2250-2259. [PMID: 27559138 DOI: 10.1152/jn.00196.2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 08/21/2016] [Indexed: 01/18/2023] Open
Abstract
Evidence of impaired function of orexin neurons has been found in individuals with cardiorespiratory disorders, such as obstructive sleep apnea (OSA) and sudden infant death syndrome (SIDS), but the mechanisms responsible are unknown. Individuals with OSA and SIDS experience repetitive breathing cessations and/or rebreathing of expired air, resulting in hypoxia/hypercapnia (H/H). In this study, we examined the responses of fluorescently identified rat orexin neurons in the lateral hypothalamus to acute H/H to test if and how these neurons alter their activity and function during this challenge. Experiments were conducted in an in vitro slice preparation using voltage-clamp and current-clamp configurations. H/H (10 min) induced hyperpolarization, accompanied by rapid depression, and finally, cessation of firing activity in orexin neurons. Hypoxia alone had similar but less potent effects. H/H did not alter the frequency of inhibitory glycinergic postsynaptic currents. The frequency of GABAergic currents was diminished but only at 8-10 min of H/H. In contrast, the frequency of excitatory glutamatergic postsynaptic events was diminished as early as 2-4 min of H/H. In the presence of glutamatergic receptor blockers, the inhibitory effects of H/H on the firing activity and membrane potential of orexin neurons persisted but to a lesser extent. In conclusion, both direct alteration of postsynaptic membrane properties and diminished glutamatergic neurotransmission likely contribute to the inhibition of orexin neurons by H/H. These mechanisms could be responsible for the decreased function of orexin in individuals at risk for OSA and SIDS.
Collapse
Affiliation(s)
- Olga Dergacheva
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC;
| | - Akihiro Yamanaka
- Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Alan R Schwartz
- Johns Hopkins University School of Medicine, Baltimore, Maryland
| | | | - David Mendelowitz
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC
| |
Collapse
|
10
|
De Luca R, Suvorava T, Yang D, Baumgärtel W, Kojda G, Haas HL, Sergeeva OA. Identification of histaminergic neurons through histamine 3 receptor-mediated autoinhibition. Neuropharmacology 2015; 106:102-15. [PMID: 26297536 DOI: 10.1016/j.neuropharm.2015.08.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 07/30/2015] [Accepted: 08/16/2015] [Indexed: 10/23/2022]
Abstract
Using a reporter mouse model with expression of the tomato fluorescent protein under the dopamine transporter promoter (Tmt-DAT) we discovered a new group of neurons in the histaminergic tuberomamillary nucleus (TMN), which, in contrast to tuberoinfundibular dopaminergic neurons of the dorsomedial arcuate nucleus, do not express tyrosine hydroxylase but can synthesize and store dopamine. Tmt-DAT neurons located within TMN share electrophysiological properties with histaminergic neurons: spontaneous firing at a membrane potential around -50 mV and presence of hyperpolarization-activated cyclic nucleotide-gated ion channels. Histamine (30 μM) depolarizes and excites Tmt-DAT neurons through H1R activation but inhibits histaminergic neurons through H3R activation thus allowing a pharmacological identification of the different neurons. Single-cell RT-PCR revealed that all histaminergic neurons expressing histidine decarboxylase (HDC) also express H3R. This includes neurons retrogradely traced from the striatum whose inhibition by a selective H3R agonist was indistinguishable from the whole population. Prolonged depolarization reduces the autoinhibition. The potency of histamine at H3R depends on membrane potential and on extracellular and intracellular calcium. Autoinhibition can be impaired by preincubation with capsaicin, a ligand of the calcium-permeable TRPV1 channel or by blockade of Ca(2+)-ATPase with thapsigargin. The pharmacology of autoinhibition is revisited and physiological conditions for its functionality are determined. Usage of reporter mouse models for the safe identification of aminergic neurons under pathophysiological conditions is recommended. This article is part of the Special Issue entitled 'Histamine Receptors'.
Collapse
Affiliation(s)
- Roberto De Luca
- Department of Neurophysiology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Tatsiana Suvorava
- Institute for Pharmacology and Clinical Pharmacology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Danqing Yang
- Department of Neurophysiology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Wilhelm Baumgärtel
- Department of Neurophysiology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Georg Kojda
- Institute for Pharmacology and Clinical Pharmacology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Helmut L Haas
- Department of Neurophysiology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany
| | - Olga A Sergeeva
- Department of Neurophysiology, Heinrich-Heine-Universität, Medical Faculty, D-40225 Düsseldorf, Germany.
| |
Collapse
|