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Hofmann GC, Gama de Barcellos Filho P, Khodadadi F, Ostrowski D, Kline DD, Hasser EM. Vagotomy blunts cardiorespiratory responses to vagal afferent stimulation via pre- and postsynaptic effects in the nucleus tractus solitarii. J Physiol 2024; 602:1147-1174. [PMID: 38377124 DOI: 10.1113/jp285854] [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: 10/26/2023] [Accepted: 01/29/2024] [Indexed: 02/22/2024] Open
Abstract
Viscerosensory information travels to the brain via vagal afferents, where it is first integrated within the brainstem nucleus tractus solitarii (nTS), a critical contributor to cardiorespiratory function and site of neuroplasticity. We have shown that decreasing input to the nTS via unilateral vagus nerve transection (vagotomy) induces morphological changes in nTS glia and reduces sighs during hypoxia. The mechanisms behind post-vagotomy changes are not well understood. We hypothesized that chronic vagotomy alters cardiorespiratory responses to vagal afferent stimulation via blunted nTS neuronal activity. Male Sprague-Dawley rats (6 weeks old) underwent right cervical vagotomy caudal to the nodose ganglion, or sham surgery. After 1 week, rats were anaesthetized, ventilated and instrumented to measure mean arterial pressure (MAP), heart rate (HR), and splanchnic sympathetic and phrenic nerve activity (SSNA and PhrNA, respectively). Vagal afferent stimulation (2-50 Hz) decreased cardiorespiratory parameters and increased neuronal Ca2+ measured by in vivo photometry and in vitro slice imaging of nTS GCaMP8m. Vagotomy attenuated both these reflex and neuronal Ca2+ responses compared to shams. Vagotomy also reduced presynaptic Ca2+ responses to stimulation (Cal-520 imaging) in the nTS slice. The decrease in HR, SSNA and PhrNA due to nTS nanoinjection of exogenous glutamate also was tempered following vagotomy. This effect was not restored by blocking excitatory amino acid transporters. However, the blunted responses were mimicked by NMDA, not AMPA, nanoinjection and were associated with reduced NR1 subunits in the nTS. Altogether, these results demonstrate that vagotomy induces multiple changes within the nTS tripartite synapse that influence cardiorespiratory reflex responses to afferent stimulation. KEY POINTS: Multiple mechanisms within the nucleus tractus solitarii (nTS) contribute to functional changes following vagal nerve transection. Vagotomy results in reduced cardiorespiratory reflex responses to vagal afferent stimulation and nTS glutamate nanoinjection. Blunted responses occur via reduced presynaptic Ca2+ activation and attenuated NMDA receptor expression and function, leading to a reduction in nTS neuronal activation. These results provide insight into the control of autonomic and respiratory function, as well as the plasticity that can occur in response to nerve damage and cardiorespiratory disease.
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Affiliation(s)
- Gabrielle C Hofmann
- Comparative Medicine, University of Missouri, Columbia, Missouri, USA
- Area Pathobiology, University of Missouri, Columbia, Missouri, USA
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
| | - Procopio Gama de Barcellos Filho
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
| | - Fateme Khodadadi
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
| | - Daniela Ostrowski
- Department of Pharmacology, A.T. Still University, Kirksville, Missouri, USA
| | - David D Kline
- Area Pathobiology, University of Missouri, Columbia, Missouri, USA
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
- Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - Eileen M Hasser
- Area Pathobiology, University of Missouri, Columbia, Missouri, USA
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
- Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
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Souza JR, Lima-Silveira L, Accorsi-Mendonça D, Machado BH. Enhancement of the Evoked Excitatory Transmission in the Nucleus Tractus Solitarius Neurons after Sustained Hypoxia in Mice Depends on A 2A Receptors. Neuroscience 2024; 536:57-71. [PMID: 37979842 DOI: 10.1016/j.neuroscience.2023.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 11/06/2023] [Accepted: 11/11/2023] [Indexed: 11/20/2023]
Abstract
The first synapses of the afferents of peripheral chemoreceptors are located in the Nucleus Tractus Solitarius (NTS) and there is evidence that short-term sustained hypoxia (SH - 24 h, FiO2 0.1) facilitates glutamatergic transmission in NTS neurons of rats. Adenosine is an important neuromodulator of synaptic transmission and hypoxia contributes to increase its extracellular concentration. The A2A receptors mediate the excitatory actions of adenosine and are active players in the modulation of neuronal networks in the NTS. Herein, we used knockout mice for A2A receptors (A2AKO) and electrophysiological recordings of NTS neurons were performed to evaluate the contribution of these receptors in the changes in synaptic transmission in NTS neurons of mice submitted to SH. The membrane passive properties and excitability of NTS neurons were not affected by SH and were similar between A2AKO and wild-type mice. The overall amplitude of spontaneous glutamatergic currents in NTS neurons of A2AKO mice was lower than in Balb/c WT mice. SH increased the amplitude of evoked glutamatergic currents of NTS neurons from WT mice by a non-presynaptic mechanism, but this enhancement was not observed in NTS neurons of A2AKO mice. Under normoxia, the amplitude of evoked glutamatergic currents was similar between WT and A2AKO mice. The data indicate that A2A receptors (a) modulate spontaneous glutamatergic currents, (b) do not modulate the evoked glutamatergic transmission in the NTS neurons under control conditions, and (c) are required for the enhancement of glutamatergic transmission observed in the NTS neurons of mice submitted to SH.
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Affiliation(s)
- Juliana R Souza
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Ludmila Lima-Silveira
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil.
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Collins SA, Stinson HE, Himes A, Nestor-Kalinoski A, Ninan I. Sex-specific modulation of the medial prefrontal cortex by glutamatergic median raphe neurons. SCIENCE ADVANCES 2023; 9:eadg4800. [PMID: 37948526 PMCID: PMC10637752 DOI: 10.1126/sciadv.adg4800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 10/13/2023] [Indexed: 11/12/2023]
Abstract
A substantial proportion of raphe neurons are glutamatergic. However, little is known about how these glutamatergic neurons modulate the forebrain. We investigated how glutamatergic median raphe nucleus (MRN) input modulates the medial prefrontal cortex (mPFC), a critical component of fear circuitry. We show that vesicular glutamate transporter 3 (VGLUT3)-expressing MRN neurons activate VGLUT3- and somatostatin-expressing neurons in the mPFC. Consistent with this modulation of mPFC GABAergic neurons, activation of MRN (VGLUT3) neurons enhances GABAergic transmission in mPFC pyramidal neurons and attenuates fear memory in female but not male mice. Serotonin plays a key role in MRN (VGLUT3) neuron-mediated GABAergic plasticity in the mPFC. In agreement with these female-specific effects, we observed sex differences in glutamatergic transmission onto MRN (VGLUT3) neurons and in mPFC (VGLUT3) neuron-mediated dual release of glutamate and GABA. Our results demonstrate a cell type-specific modulation of the mPFC by MRN (VGLUT3) neurons and reveal a sex-specific role of this neuromodulation in mPFC synaptic plasticity.
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Affiliation(s)
- Stuart A. Collins
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Hannah E. Stinson
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Amanda Himes
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Andrea Nestor-Kalinoski
- Department of Surgery, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
| | - Ipe Ninan
- Department of Neurosciences, University of Toledo College of Medicine and Life Sciences, Toledo, OH, USA
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Ruyle BC, Lima-Silveira L, Martinez D, Cummings KJ, Heesch CM, Kline DD, Hasser EM. Paraventricular nucleus projections to the nucleus tractus solitarii are essential for full expression of hypoxia-induced peripheral chemoreflex responses. J Physiol 2023; 601:4309-4336. [PMID: 37632733 DOI: 10.1113/jp284907] [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: 05/26/2023] [Accepted: 07/13/2023] [Indexed: 08/28/2023] Open
Abstract
The hypothalamic paraventricular nucleus (PVN) is essential to peripheral chemoreflex neurocircuitry, but the specific efferent pathways utilized are not well defined. The PVN sends dense projections to the nucleus tractus solitarii (nTS), which exhibits neuronal activation following a hypoxic challenge. We hypothesized that nTS-projecting PVN (PVN-nTS) neurons contribute to hypoxia-induced nTS neuronal activation and cardiorespiratory responses. To selectively target PVN-nTS neurons, rats underwent bilateral nTS nanoinjection of retrogradely transported adeno-associated virus (AAV) driving Cre recombinase expression. We then nanoinjected into PVN AAVs driving Cre-dependent expression of Gq or Gi designer receptors exclusively activated by designer drugs (DREADDs) to test the degree that selective activation or inhibition, respectively, of the PVN-nTS pathway affects the hypoxic ventilatory response (HVR) of conscious rats. We used immunohistochemistry for Fos and extracellular recordings to examine how DREADD activation influences PVN-nTS neuronal activation by hypoxia. Pathway activation enhanced the HVR at moderate hypoxic intensities and increased PVN and nTS Fos immunoreactivity in normoxia and hypoxia. In contrast, PVN-nTS inhibition reduced both the HVR and PVN and nTS neuronal activation following hypoxia. To further confirm selective pathway effects on central cardiorespiratory output, rats underwent hypoxia before and after bilateral nTS nanoinjections of C21 to activate or inhibit PVN-nTS terminals. PVN terminal activation within the nTS enhanced tachycardic, sympathetic and phrenic (PhrNA) nerve activity responses to hypoxia whereas inhibition attenuated hypoxia-induced increases in nTS neuronal action potential discharge and PhrNA. The results demonstrate the PVN-nTS pathway enhances nTS neuronal activation and is necessary for full cardiorespiratory responses to hypoxia. KEY POINTS: The hypothalamic paraventricular nucleus (PVN) contributes to peripheral chemoreflex cardiorespiratory responses, but specific PVN efferent pathways are not known. The nucleus tractus solitarii (nTS) is the first integration site of the peripheral chemoreflex, and the nTS receives dense projections from the PVN. Selective GqDREADD activation of the PVN-nTS pathway was shown to enhance ventilatory responses to hypoxia and activation (Fos immunoreactivity (IR)) of nTS neurons in conscious rats, augmenting the sympathetic and phrenic nerve activity (SSNA and PhrNA) responses to hypoxia in anaesthetized rats. Selective GiDREADD inhibition of PVN-nTS neurons attenuates ventilatory responses, nTS neuronal Fos-IR, action potential discharge and PhrNA responses to hypoxia. These results demonstrate that a projection from the PVN to the nTS is critical for full chemoreflex responses to hypoxia.
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Affiliation(s)
- Brian C Ruyle
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
| | - Ludmila Lima-Silveira
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Diana Martinez
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Kevin J Cummings
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Cheryl M Heesch
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - David D Kline
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
| | - Eileen M Hasser
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
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Lyubashina OA, Sivachenko IB, Sushkevich BM, Busygina II. Opposing effects of 5-HT1A receptor agonist buspirone on supraspinal abdominal pain transmission in normal and visceral hypersensitive rats. J Neurosci Res 2023; 101:1555-1571. [PMID: 37331003 DOI: 10.1002/jnr.25222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 05/11/2023] [Accepted: 05/28/2023] [Indexed: 06/20/2023]
Abstract
The serotonergic 5-HT1A receptors are implicated in the central mechanisms of visceral pain, but their role in these processes is controversial. Considering existing evidences for organic inflammation-triggered neuroplastic changes in the brain serotonergic circuitry, the ambiguous contribution of 5-HT1A receptors to supraspinal control of visceral pain in normal and post-inflammatory conditions can be assumed. In this study performed on male Wistar rats, we used microelectrode recording of the caudal ventrolateral medulla (CVLM) neuron responses to colorectal distension (CRD) and electromyography recording of CRD-evoked visceromotor reactions (VMRs) to evaluate post-colitis changes in the effects of 5-HT1A agonist buspirone on supraspinal visceral nociceptive transmission. In rats recovered from trinitrobenzene sulfonic acid colitis, the CRD-induced CVLM neuronal excitation and VMRs were increased compared with those in healthy animals, revealing post-inflammatory intestinal hypersensitivity. Intravenous buspirone (2 and 4 mg/kg) under urethane anesthesia dose-dependently suppressed CVLM excitatory neuron responses to noxious CRD in healthy rats, but caused dose-independent increase in the already enhanced nociceptive activation of CVLM neurons in post-colitis animals, losing also its normally occurring faciliatory effect on CRD-evoked inhibitory medullary neurotransmission and suppressive action on hemodynamic reactions to CRD. In line with this, subcutaneous injection of buspirone (2 mg/kg) in conscious rats, which attenuated CRD-induced VMRs in controls, further increased VMRs in hypersensitive animals. The data obtained indicate a shift from anti- to pronociceptive contribution of 5-HT1A-dependent mechanisms to supraspinal transmission of visceral nociception in intestinal hypersensitivity conditions, arguing for the disutility of buspirone and possibly other 5-HT1A agonists for relieving post-inflammatory abdominal pain.
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Affiliation(s)
- Olga A Lyubashina
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Ivan B Sivachenko
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Boris M Sushkevich
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, Saint Petersburg, Russia
| | - Irina I Busygina
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, Saint Petersburg, Russia
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Ostrowski D, Heesch CM, Kline DD, Hasser EM. Nucleus tractus solitarii is required for the development and maintenance of phrenic and sympathetic long-term facilitation after acute intermittent hypoxia. Front Physiol 2023; 14:1120341. [PMID: 36846346 PMCID: PMC9949380 DOI: 10.3389/fphys.2023.1120341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/26/2023] [Indexed: 02/11/2023] Open
Abstract
Exposure to acute intermittent hypoxia (AIH) induces prolonged increases (long term facilitation, LTF) in phrenic and sympathetic nerve activity (PhrNA, SNA) under basal conditions, and enhanced respiratory and sympathetic responses to hypoxia. The mechanisms and neurocircuitry involved are not fully defined. We tested the hypothesis that the nucleus tractus solitarii (nTS) is vital to augmentation of hypoxic responses and the initiation and maintenance of elevated phrenic (p) and splanchnic sympathetic (s) LTF following AIH. nTS neuronal activity was inhibited by nanoinjection of the GABAA receptor agonist muscimol before AIH exposure or after development of AIH-induced LTF. AIH but not sustained hypoxia induced pLTF and sLTF with maintained respiratory modulation of SSNA. nTS muscimol before AIH increased baseline SSNA with minor effects on PhrNA. nTS inhibition also markedly blunted hypoxic PhrNA and SSNA responses, and prevented altered sympathorespiratory coupling during hypoxia. Inhibiting nTS neuronal activity before AIH exposure also prevented the development of pLTF during AIH and the elevated SSNA after muscimol did not increase further during or following AIH exposure. Furthermore, nTS neuronal inhibition after the development of AIH-induced LTF substantially reversed but did not eliminate the facilitation of PhrNA. Together these findings demonstrate that mechanisms within the nTS are critical for initiation of pLTF during AIH. Moreover, ongoing nTS neuronal activity is required for full expression of sustained elevations in PhrNA following exposure to AIH although other regions likely also are important. Together, the data indicate that AIH-induced alterations within the nTS contribute to both the development and maintenance of pLTF.
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Affiliation(s)
- Daniela Ostrowski
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, United States,Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States,Department of Biology, Truman State University, Kirksville, MO, United States
| | - Cheryl M. Heesch
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, United States,Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States
| | - David D. Kline
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, United States,Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - Eileen M. Hasser
- Department of Biomedical Sciences, University of Missouri, Columbia, MO, United States,Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States,*Correspondence: Eileen M. Hasser,
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Lima-Silveira L, Hasser EM, Kline DD. Cardiovascular deconditioning increases GABA signaling in the nucleus tractus solitarii. J Neurophysiol 2022; 128:28-39. [PMID: 35642806 PMCID: PMC9236861 DOI: 10.1152/jn.00102.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nucleus tractus solitarii (nTS) is the major integrative brainstem region for autonomic modulation and processing of cardiovascular reflexes. GABA and glutamate are the main inhibitory and excitatory neurotransmitters, respectively, within this nucleus. Alterations in the GABA-glutamate regulation in the nTS are related to numerous cardiovascular comorbidities. Bedridden individuals and people exposed to microgravity exhibit dysautonomia and cardiovascular deconditioning that are mimicked in the hindlimb unloading (HU) rat model. We have previously shown in the nTS that HU increases glutamatergic neurotransmission yet decreases neuronal excitability. In this study, we investigated the effects of HU on nTS GABAergic neurotransmission. We hypothesized that HU potentiates GABA signaling via increased GABAergic release and postsynaptic GABA receptor expression. Following HU or control postural exposure, GABAergic neurotransmission was assessed using whole cell patch clamp whereas the magnitude of GABA release was evaluated via an intensity-based GABA sensing fluorescence reporter (iGABASnFR). In response to GABA interneuron stimulation, the evoked inhibitory postsynaptic current (nTS-IPSC) amplitude and area, as well as iGABASnFR fluorescence, were greater in HU than in control. HU also elevated the frequency but not the amplitude of spontaneous miniature IPSCs. Picoapplication of GABA produced similar postsynaptic current responses in nTS neurons of HU and control. Moreover, HU did not alter GABAA receptor α1 subunit expression, indicating minimal alterations in postsynaptic membrane receptor expression. These results indicate that HU increases GABAergic signaling in the nTS likely via augmented release of GABA from presynaptic terminals. Altogether, our data indicate GABA plasticity contributes to the autonomic and cardiovascular alterations following cardiovascular deconditioning (CVD).NEW & NOTEWORTHY Gravity influences distribution of blood volume and autonomic function. Microgravity and prolonged bed rest induce cardiovascular deconditioning (CVD). We used hindlimb unloading (HU), a rat analog for bed rest, to investigate CVD-induced neuroplasticity in the brainstem. Our data demonstrate that HU increases GABA modulation of nucleus tractus solitarii (nTS) neurons via presynaptic plasticity. Given the importance of nTS in integrating cardiovascular reflexes, this study provides new evidence on the central mechanisms behind CVD following HU.
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Affiliation(s)
- Ludmila Lima-Silveira
- 1Department of Biomedical Sciences, University of Missouri, Columbia, Missouri,3Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Eileen M. Hasser
- 1Department of Biomedical Sciences, University of Missouri, Columbia, Missouri,2Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri,3Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - David D. Kline
- 1Department of Biomedical Sciences, University of Missouri, Columbia, Missouri,2Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri,3Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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8
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Martinez D, Lima-Silveira L, Matott MP, Hasser EM, Kline DD. Gamma-Aminobutyric Acid Transporters in the Nucleus Tractus Solitarii Regulate Inhibitory and Excitatory Synaptic Currents That Influence Cardiorespiratory Function. Front Physiol 2022; 12:821110. [PMID: 35095576 PMCID: PMC8795970 DOI: 10.3389/fphys.2021.821110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 12/22/2021] [Indexed: 12/29/2022] Open
Abstract
The brainstem nucleus tractus solitarii (nTS) processes and modulates the afferent arc of critical peripheral cardiorespiratory reflexes. Sensory afferents release glutamate to initiate the central component of these reflexes, and glutamate concentration is critically controlled by its removal via astrocytic neurotransmitter transporters. Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the nTS providing tonic and phasic modulation of neuronal activity. GABA is removed from the extracellular space through GABA transporters (GATs), however, the role of GATs in nTS synaptic transmission and their influence on cardiorespiratory function is unknown. We hypothesized that GATs tonically restrain nTS inhibitory signaling and given the considerable nTS GABA-glutamate cross-talk, modify excitatory signaling and thus cardiorespiratory function. Reverse transcription real-time polymerase chain reaction (RT-PCR), immunoblot and immunohistochemistry showed expression of GAT-1 and GAT-3 mRNA and protein within the rat nTS, with GAT-3 greater than GAT-1, and GAT-3 colocalizing with astrocyte S100B. Recordings in rat nTS slices demonstrated GAT-3 block decreased spontaneous inhibitory postsynaptic current (IPSC) frequency and reduced IPSC amplitude evoked from electrical stimulation of the medial nTS. Block of GAT-3 also increased spontaneous excitatory postsynaptic current (EPSC) frequency yet did not alter sensory afferent-evoked EPSC amplitude. Block of GAT-3 in the nTS of anesthetized rats increased mean arterial pressure, heart rate, sympathetic nerve activity, and minute phrenic nerve activity. These results demonstrate inhibitory and excitatory neurotransmission in the nTS is significantly modulated by endogenous GAT-3 to influence basal cardiorespiratory function.
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Affiliation(s)
- Diana Martinez
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States
| | - Ludmila Lima-Silveira
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States
| | - Michael P Matott
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States
| | - Eileen M Hasser
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States.,Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, United States
| | - David D Kline
- Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, United States
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Ehlen JC, Forman CM, Ostrowski D, Ostrowski TD. Autonomic Dysfunction Impairs Baroreflex Function in an Alzheimer's Disease Animal Model. J Alzheimers Dis 2022; 90:1449-1464. [PMID: 36278348 PMCID: PMC9742304 DOI: 10.3233/jad-220496] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Alzheimer's disease (AD) patients frequently present with orthostatic hypotension. This inability to reflexively increase blood pressure on standing is a serious health concern and increases the risk of stroke and cardiovascular diseases. OBJECTIVE Since there are no clear mechanisms for orthostatic hypotension in human AD, the present study assessed the autonomic changes that could explain this comorbidity in an AD animal model. METHODS We used the established streptozotocin-induced rat model of AD (STZ-AD), which mimics many hallmark symptoms of sporadic AD in humans. Baroreflex responses were analyzed in anesthetized STZ-AD rats using femoral catheterization for blood pressure and heart rate, and autonomic activity was assessed using specific blockers and splanchnic sympathetic nerve recordings. Expression levels of autonomic receptors at the heart were examined using the western blot technique. RESULTS Baroreflex function in STZ-AD showed a blunted heart rate (HR) response to low blood pressure challenges, and the maximal sympathetic nerve activity was reduced. Conversely, HR responses to high blood pressure were similar to control, indicating no change in parasympathetic nerve activity. Under resting conditions, autonomic blockade demonstrated a baseline shift to increased sympathetic tone in STZ-AD. Protein expression levels of beta-1 adrenergic receptor and muscarinic acetylcholine receptor M2 in the heart were unchanged. CONCLUSION Our study provides the first data on the pathological influence of AD on baroreflex function, which primarily affected the sympathetic nervous system in STZ-AD. These results represent the first mechanisms that may correlate with the orthostatic hypotension in human AD.
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Affiliation(s)
- John C. Ehlen
- Department of Physiology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO, USA
| | | | | | - Tim D. Ostrowski
- Department of Physiology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO, USA
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Zhuang J, Xu F. Systemic 8-OH-DPAT challenge causes hyperventilation largely via activating pre-botzinger complex 5-HT 1A receptors. Respir Physiol Neurobiol 2021; 296:103810. [PMID: 34728431 DOI: 10.1016/j.resp.2021.103810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 09/23/2021] [Accepted: 10/27/2021] [Indexed: 11/24/2022]
Abstract
Systemic 8-OH-DPAT (a 5-HT1A receptor agonist) challenge evokes hyperventilation independent of peripheral 5-HT1A receptors. Though the pre-Botzinger Complex (PBC) is critical in generating respiratory rhythm and activation of local 5-HT1A receptors induces tachypnea via disinhibition of local GABAA neurons, its role in the respiratory response to systemic 8-OH-DPAT challenge is still unclear. In anesthetized rats, 8-OH-DPAT (100 μg/kg, iv) was injected twice to confirm the reproducibility of the evoked responses. The same challenges were performed after bilateral microinjections of (S)-WAY-100135 (a 5-HT1A receptor antagonist) or gabazine (a GABAA receptor antagonist) into the PBC. Our results showed that: 1) 8-OH-DPAT caused reproducible hyperventilation associated with hypotension and bradycardia; 2) microinjections of (S)-WAY-100135 into the PBC attenuated the hyperventilation by ˜60 % without effect on the evoked hypotension and bradycardia; and 3) the same hyperventilatory attenuation was also observed after microinjections of gabazine into the PBC. Our data suggest that PBC 5-HT1A receptors play a key role in the respiratory response to systemic 8-OH-DPAT challenge likely via disinhibiting local GABAergic neurons.
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Affiliation(s)
- Jianguo Zhuang
- Pathophysiology Program, Lovelace Biomedical Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM, 87108, United States
| | - Fadi Xu
- Pathophysiology Program, Lovelace Biomedical Research Institute, 2425 Ridgecrest Drive SE, Albuquerque, NM, 87108, United States.
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11
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Hofmann GC, Hasser EM, Kline DD. Unilateral vagotomy alters astrocyte and microglial morphology in the nucleus tractus solitarii of the rat. Am J Physiol Regul Integr Comp Physiol 2021; 320:R945-R959. [PMID: 33978480 PMCID: PMC8285617 DOI: 10.1152/ajpregu.00019.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 04/09/2021] [Accepted: 05/04/2021] [Indexed: 12/11/2022]
Abstract
The nucleus tractus solitarii (nTS) is the initial site of integration of sensory information from the cardiorespiratory system and contributes to reflex responses to hypoxia. Afferent fibers of the bilateral vagus nerves carry input from the heart, lungs, and other organs to the nTS where it is processed and modulated. Vagal afferents and nTS neurons are integrally associated with astrocytes and microglia that contribute to neuronal activity and influence cardiorespiratory control. We hypothesized that vagotomy would alter glial morphology and cardiorespiratory responses to hypoxia. Unilateral vagotomy (or sham surgery) was performed in rats. Prior to and seven days after surgery, baseline and hypoxic cardiorespiratory responses were monitored in conscious and anesthetized animals. The brainstem was sectioned and caudal, mid-area postrema (mid-AP), and rostral sections of the nTS were prepared for immunohistochemistry. Vagotomy increased immunoreactivity (-IR) of astrocytic glial fibrillary acidic protein (GFAP), specifically at mid-AP in the nTS. Similar results were found in the dorsal motor nucleus of the vagus (DMX). Vagotomy did not alter nTS astrocyte number, yet increased astrocyte branching and altered morphology. In addition, vagotomy both increased nTS microglia number and produced morphologic changes indicative of activation. Cardiorespiratory baseline parameters and hypoxic responses remained largely unchanged, but vagotomized animals displayed fewer augmented breaths (sighs) in response to hypoxia. Altogether, vagotomy alters nTS glial morphology, indicative of functional changes in astrocytes and microglia that may affect cardiorespiratory function in health and disease.
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Affiliation(s)
- Gabrielle C Hofmann
- Comparative Medicine, University of Missouri, Columbia, Missouri
- Area Pathobiology, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Eileen M Hasser
- Area Pathobiology, University of Missouri, Columbia, Missouri
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - David D Kline
- Area Pathobiology, University of Missouri, Columbia, Missouri
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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12
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Kur'yanova EV, Tryasuchev AV, Stupin VO, Zhukova YD. Peculiarities of Heart Rate Variability Changes in Random-Bred Male Rats during Transition into Anesthetic Sleep under Stimulation of Central Neurotransmitter Systems. Bull Exp Biol Med 2021; 170:585-589. [PMID: 33792819 DOI: 10.1007/s10517-021-05111-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Indexed: 10/21/2022]
Abstract
General anesthesia with Nembutal (40 mg/kg) dramatically decreased the power of all waves of HRV spectrum in rats, especially in LF and VLF frequency bands, but the HR and respiration rate were little changed. At this, individual spectral peaks in HF range were observed at the same frequencies (1.3-1.5 Hz), which are characteristic of the wakeful state. Preliminary stimulation of noradrenergic system with maprotiline (10 mg/kg) increased the power of HF waves and elevated the respiratory rate in narcotized rats in comparison with the control values, although it did not shift the spectral peak at 1.5 Hz in frequency axis. Preliminary stimulation of cholinergic system with galantamine (2 mg/kg) somewhat decreased the power of HF waves and respiratory rate in narcotized rats (in comparison with the control values); additionally, it shifted HF peak to 1.1-1.4 Hz. Activation of serotonergic system with 5-hydroxytryptophan (50 mg/kg) and fluoxetine (3 mg/kg) decreased the HR, the power of HF waves, and respiratory rate in narcotized rats. It also shifted the spectral peak of HF waves to 0.9-0.95 Hz. Preliminary stimulation of dopaminergic system with L-DOPA (20 ml/kg) and amantadine (20 ml/kg) increased the power of VLF waves in narcotized rats in comparison with the control values. Numerous peaks appeared in HF (1.1-1.2 Hz) and VLF frequency bands. Generally, preliminary stimulation of serotonergic or dopaminergic systems markedly affects the neural activity under following general anesthesia: first aggravates the effect of anesthesia on vital centers in CNS, whereas second weakens the effect of anesthesia at the suprasegmental level of neural control.
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Affiliation(s)
- E V Kur'yanova
- Department of Physiology, Morphology, Genetics, and Biomedicine, Astrakhan State University, Astrakhan, Russia.
| | - A V Tryasuchev
- Department of Physiology, Morphology, Genetics, and Biomedicine, Astrakhan State University, Astrakhan, Russia
| | - V O Stupin
- Department of Physiology, Morphology, Genetics, and Biomedicine, Astrakhan State University, Astrakhan, Russia
| | - Yu D Zhukova
- Department of Physiology, Morphology, Genetics, and Biomedicine, Astrakhan State University, Astrakhan, Russia
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13
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Wang HQ, Wang ZZ, Chen NH. The receptor hypothesis and the pathogenesis of depression: Genetic bases and biological correlates. Pharmacol Res 2021; 167:105542. [PMID: 33711432 DOI: 10.1016/j.phrs.2021.105542] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 02/24/2021] [Accepted: 03/07/2021] [Indexed: 02/08/2023]
Abstract
Depression has become one of the most prevalent neuropsychiatric disorders characterized by anhedonia, anxiety, pessimism, or even suicidal thoughts. Receptor theory has been pointed out to explain the pathogenesis of depression, while it is still subject to debate. Additionally, gene abnormality accounts for nearly 40-50% of depression risk, which is a significant factor contributing to the onset of depression. Accordingly, studying on receptors and their gene abnormality are critical parts of the research on internal causes of depression. This review summarizes the pathogenesis of depression from six of the most related receptors and their associated genes, including N-methyl-D-aspartate receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, glucocorticoid receptor, 5-hydroxytryptamine receptor, GABAA receptor α2, and dopamine receptor; and several "non-classic" receptors, such as metabotropic glutamate receptor, opioid receptor, and insulin receptor. These receptors have received considerable critical attention and are highly implicated in the onset of depression. We begin by providing the biological mechanisms of action of these receptors on the pathogenesis of depression. Then we review the historical and social context about these receptors. Finally, we discuss the limitations of the current state of knowledge and outline insights on future research directions, aiming to provide more novel targets and theoretical basis for the early prevention, accurate diagnosis and prompt treatment of depression.
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Affiliation(s)
- Hui-Qin Wang
- Hunan University of Chinese Medicine & Hunan Engineering Technology Center of Standardization and Function of Chinese Herbal Decoction Pieces, Changsha 410208, Hunan, China; State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Zhen-Zhen Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
| | - Nai-Hong Chen
- Hunan University of Chinese Medicine & Hunan Engineering Technology Center of Standardization and Function of Chinese Herbal Decoction Pieces, Changsha 410208, Hunan, China; State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
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14
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Pascoaloti-Lima JC, Machado BH, Accorsi-Mendonça D. Sustained Hypoxia Reduces GABAergic Modulation on NTS Neurons Sending Projections to Ventral Medulla of Rats. Neuroscience 2021; 457:1-11. [PMID: 33421568 DOI: 10.1016/j.neuroscience.2020.12.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 11/26/2022]
Abstract
Peripheral chemoreflex is activated during short-term sustained hypoxia (SH), and the first synapse of these afferents is located in Nucleus Tractus Solitarius(NTS). NTS neurons projecting to the ventral lateral medulla (NTS-VLM) are part of the respiratory pathways of the chemoreflex. SH increases the magnitude of basal respiratory parameters in rats from Wistar-Hannover strain. In this study, we hypothesized that the observed changes in the respiratory pattern in response to SH were due to changes in the GABAergic modulation of the synaptic transmission of NTS-VLM neurons. We used an electrophysiological approach to record the synaptic activity of NTS neurons labeled with a retrograde tracer previously microinjected into VLM of Wistar-Hannover rats submitted to 24 h SH. The data are showing that: (a) the amplitude of evoked inhibitory currents in NTS-VLM neurons of SH rats was reduced and not accompanied by any change in rise-time and decay-time; (b) the 1/CV2 and the number of failures in response to evoked currents were also affected by SH; (c) the frequency of spontaneous inhibitory currents was reduced by SH without changes in amplitude and half-width. These effects of SH were observed in NTS-VLM neurons located in caudal and intermediate NTS, but not in NTS-VLM neurons located in the rostral NTS. We conclude that SH causes a reduction in inhibitory modulation onto NTS-VLM neurons by pre-synaptic mechanisms, which may contribute to the observed changes in the respiratory pattern of Wistar-Hannover rats submitted to SH.
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Affiliation(s)
- Júlio C Pascoaloti-Lima
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
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15
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Panteleev SS, Sivachenko IB, Lyubashina OA. The Buspirone-dependent Abdominal Pain Transmission Within the Nucleus Tractus Solitarius in the Rat. Neuroscience 2020; 452:326-334. [PMID: 33248152 DOI: 10.1016/j.neuroscience.2020.11.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 10/22/2020] [Accepted: 11/18/2020] [Indexed: 01/07/2023]
Abstract
Buspirone, a partial agonist of the 5-HT1aR, due to potential antinociceptive properties can be useful for abdominal pain treatment in IBS patients. Pain-related effects of buspirone can be mediated by the 5-HT1aRs, located within the nucleus tractus solitarius. The 5-HT1aR involvement in pain transmission within the NTS is unclear. The objective of our study was to evaluate the involvement of the 5-HT1aR in abdominal pain transmission within the NTS. Using a model of abdominal pain on urethane-anesthetized rats, two types of NTS pain-related neurons responding to the noxious colorectal distension (CRD) with excitatory and inhibitory sustained patterns of evoked activity were revealed. Buspirone (1.0-4.0 mg kg-1, iv) has complex time- and dose-depended action on the CRD-induced NTS neuron responses. Buspirone inhibits the responses of the excitatory neurons and inverts the responses of the inhibitory pain-related neurons but at a dose of 4.0 buspirone, the effect on NTS pain-related neurons attenuates. The inhibitory effect of buspirone on the CRD-evoked responses of the excitatory NTS neurons is completely blocked by an intra-cerebroventricular administration of buspirone agonist WAY100,635. The inhibitory responses do not change by this agonist. The inhibitory action of buspirone is mediated by supraspinal 5-HT1a receptors however, its excitatory effect on inhibitory neurons does not dependents on these receptors. We proposed that the NTS pain-related neurons could be involved in anti- or pronociceptive effects of buspirone on abdominal pain.
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Affiliation(s)
- Sergey S Panteleev
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, 6 Nab. Makarova, Saint-Petersburg 199034, Russia.
| | - Ivan B Sivachenko
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, 6 Nab. Makarova, Saint-Petersburg 199034, Russia.
| | - Olga A Lyubashina
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology of the Russian Academy of Sciences, 6 Nab. Makarova, Saint-Petersburg 199034, Russia; Department of Neuropharmacology, Valdman Institute of Pharmacology, First Saint-Petersburg Pavlov State Medical University, 6/8 Lev Tolstoy Street, Saint-Petersburg 197022, Russia.
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16
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Lima-Silveira L, Martinez D, Hasser EM, Kline DD. Mechanisms Underlying Neuroplasticity in the Nucleus Tractus Solitarii Following Hindlimb Unloading in Rats. Neuroscience 2020; 449:214-227. [PMID: 33039526 DOI: 10.1016/j.neuroscience.2020.09.043] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/15/2020] [Accepted: 09/20/2020] [Indexed: 12/11/2022]
Abstract
Hindlimb unloading (HU) in rats induces cardiovascular deconditioning (CVD) analogous to that observed in individuals exposed to microgravity or bed rest. Among other physiological changes, HU rats exhibit autonomic imbalance and altered baroreflex function. Lack of change in visceral afferent activity that projects to the brainstem in HU rats suggests that neuronal plasticity within central nuclei processing cardiovascular afferents may be responsible for these changes in CVD and HU. The nucleus tractus solitarii (nTS) is a critical brainstem region for autonomic control and integration of cardiovascular reflexes. In this study, we used patch electrophysiology, live-cell calcium imaging and molecular methods to investigate the effects of HU on glutamatergic synaptic transmission and intrinsic properties of nTS neurons. HU increased the amplitude of monosynaptic excitatory postsynaptic currents and presynaptic calcium entry evoked by afferent tractus solitarii stimulus (TS-EPSC); spontaneous (s) EPSCs were unaffected. The addition of a NMDA receptor antagonist (AP5) reduced TS-EPSC amplitude and sEPSC frequency in HU but not control. Despite the increase in glutamatergic inputs, HU neurons were more hyperpolarized and exhibited intrinsic decreased excitability compared to controls. After block of ionotropic glutamatergic and GABAergic synaptic transmission (NBQX, AP5, Gabazine), HU neuronal membrane potential depolarized and neuronal excitability was comparable to controls. These data demonstrate that HU increases presynaptic release and TS-EPSC amplitude, which includes a NMDA receptor component. Furthermore, the decreased excitability and hyperpolarized membrane after HU are associated with enhanced GABAergic modulation. This functional neuroplasticity in the nTS may underly the CVD induced by HU.
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Affiliation(s)
- Ludmila Lima-Silveira
- Department of Biomedical Sciences, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA; Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA.
| | - Diana Martinez
- Department of Biomedical Sciences, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA; Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA.
| | - Eileen M Hasser
- Department of Biomedical Sciences, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA; Department of Medical Pharmacology and Physiology, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA; Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA.
| | - David D Kline
- Department of Biomedical Sciences, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA; Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Dr., Columbia, MO 65211, USA.
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17
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Han L, Wu KLK, Kwan PY, Chua OWH, Shum DKY, Chan YS. 5-HT 1A receptor-mediated attenuation of synaptic transmission in rat medial vestibular nucleus impacts on vestibular-related motor function. J Physiol 2020; 599:253-267. [PMID: 33006159 DOI: 10.1113/jp280610] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 09/29/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Chemogenetic activation of medial vestibular nucleus-projecting 5-HT neurons resulted in deficits in vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. The 5-HT1A receptor mediates the vestibular-related behavioural effects of 5-HT in the vestibular nucleus. 5-HT1A receptor activation attenuated evoked excitatory postsynaptic currents and evoked inhibitory postsynaptic currents via a presynaptic mechanism in the vestibular nucleus. ABSTRACT While the anxiolytic effects of serotonergic neuromodulation are well studied, its role in sensorimotor coordination and postural control is unclear. In this study, we show that an increase of serotonin (5-hydroxytryptamine, 5-HT) at the medial vestibular nucleus (MVN), a brainstem centre for vestibulospinal coordination, by either direct cannula administration or chemogenetic stimulation of MVN-projecting serotonergic neurons, adversely affected performance of rats in vestibular-mediated tasks, including negative geotaxis, balance beam and rota-rod tests. Application of the 5-HT1 and 5-HT7 receptor co-agonist 8-hydroxy-2-(di-n-propylamino) tetralin recapitulated the effect of 5-HT, while co-administration of the specific 5-HT1A receptor antagonist WAY 100135 effectively abolished all 5-HT-induced behavioural deficits. This indicated that 5-HT1A receptors mediated the effects of 5-HT in the rat MVN. Using whole-cell patch-clamp recording, we demonstrated that 5-HT1A receptor activation attenuated both evoked excitatory and evoked inhibitory postsynaptic currents through a presynaptic mechanism in the rat MVN. The results thus highlight the 5-HT1A receptor as the gain controller of vestibular-related brainstem circuits for posture and balance.
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Affiliation(s)
- Lei Han
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China
| | - Kenneth Lap-Kei Wu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China
| | - Pui-Yi Kwan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China
| | - Oscar Wing-Ho Chua
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China
| | - Daisy Kwok-Yan Shum
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China.,State Key Laboratory of Brain and Cognitive Science, The University of Hong Kong, Hong Kong, PR China
| | - Ying-Shing Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, PR China.,State Key Laboratory of Brain and Cognitive Science, The University of Hong Kong, Hong Kong, PR China
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18
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Cinelli E, Mutolo D, Iovino L, Pantaleo T, Bongianni F. Key role of 5-HT 1A receptors in the modulation of the neuronal network underlying the respiratory rhythm generation in lampreys. Eur J Neurosci 2020; 52:3903-3917. [PMID: 32378271 DOI: 10.1111/ejn.14769] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/06/2020] [Accepted: 04/29/2020] [Indexed: 12/17/2022]
Abstract
In mammals, 5-HTexcitatory respiratory effects imply 5-HT1A receptor-mediated disinhibition of pre-Bötzinger complex neurons. In the lamprey, 5-HT1A receptors are involved in the neural control of locomotion, but their role in the respiratory regulation, particularly at the level of the putative respiratory rhythm generator, the paratrigeminal respiratory group (pTRG), is not known. We here investigate the respiratory function of inhibitory 5-HT1A receptors within the pTRG of the isolated brainstem of the adult lamprey. The 5-HT1A receptor agonists either bath applied or microinjected into the pTRG did not cause significant effects. However, the selective 5-HT1A receptor antagonist (S)-WAY 100135 bath applied or microinjected into the pTRG induced depressing respiratory effects or even apnoea, thus revealing that 5-HT exerts a 5-HT1A receptor-mediated potent tonic influence on respiration and contributes to maintain baseline levels of respiratory activity. Microinjections of strychnine or bicuculline, either alone or in combination, into the pTRG prevented (S)-WAY 100135-induced apnoea. In addition, immunohistochemical studies corroborate the present findings suggesting that 5-HT1A receptors are widely expressed in close apposition to the soma of glycine-immunoreactive cells located within the pTRG region. The results show that in the lamprey respiratory network, 5-HT exerts a tonic influence on respiration by a potent inhibitory control on both GABAergic and glycinergic mechanisms. The observed disinhibitory effects resemble the excitatory respiratory modulation exerted by 5-HT1A receptor-mediated inhibition of glycinergic and/or GABAergic neurons present in mammals, supporting the notion that some features of the neuronal network subserving respiratory rhythm generation are highly conserved throughout phylogeny.
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Affiliation(s)
- Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Firenze, Italy
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Firenze, Italy
| | - Ludovica Iovino
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Firenze, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Firenze, Italy
| | - Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Firenze, Italy
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19
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Martinez D, Rogers RC, Hermann GE, Hasser EM, Kline DD. Astrocytic glutamate transporters reduce the neuronal and physiological influence of metabotropic glutamate receptors in nucleus tractus solitarii. Am J Physiol Regul Integr Comp Physiol 2020; 318:R545-R564. [PMID: 31967862 PMCID: PMC7099463 DOI: 10.1152/ajpregu.00319.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Astrocytic excitatory amino acid transporters (EAATs) are critical to restraining synaptic and neuronal activity in the nucleus tractus solitarii (nTS). Relief of nTS EAAT restraint generates two opposing effects, an increase in neuronal excitability that reduces blood pressure and breathing and an attenuation in afferent [tractus solitarius (TS)]-driven excitatory postsynaptic current (EPSC) amplitude. Although the former is due, in part, to activation of ionotropic glutamate receptors, there remains a substantial contribution from another unidentified glutamate receptor. In addition, the mechanism(s) by which EAAT inhibition reduced TS-EPSC amplitude is unknown. Metabotropic glutamate receptors (mGluRs) differentially modulate nTS excitability. Activation of group I mGluRs on nTS neuron somas leads to depolarization, whereas group II/III mGluRs on sensory afferents decrease TS-EPSC amplitude. Thus we hypothesize that EAATs control postsynaptic excitability and TS-EPSC amplitude via restraint of mGluR activation. To test this hypothesis, we used in vivo recording, brain slice electrophysiology, and imaging of glutamate release and TS-afferent Ca2+. Results show that EAAT blockade in the nTS with (3S)-3-[[3-[[4-(trifluoromethyl)benzoyl]amino]phenyl]methoxy]-l-aspartic acid (TFB-TBOA) induced group I mGluR-mediated depressor, bradycardic, and apneic responses that were accompanied by neuronal depolarization, elevated discharge, and increased spontaneous synaptic activity. Conversely, upon TS stimulation TFB-TBOA elevated extracellular glutamate to decrease presynaptic Ca2+ and TS-EPSC amplitude via activation of group II/III mGluRs. Together, these data suggest an important role of EAATs in restraining mGluR activation and overall cardiorespiratory function.
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Affiliation(s)
- Diana Martinez
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | | | | | - Eileen M. Hasser
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri,2Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
| | - David D. Kline
- 1Department of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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20
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Vicente MC, Humphrey CM, Gargaglioni LH, Ostrowski TD. Decreased excitability of locus coeruleus neurons during hypercapnia is exaggerated in the streptozotocin-model of Alzheimer's disease. Exp Neurol 2020; 328:113250. [PMID: 32088169 DOI: 10.1016/j.expneurol.2020.113250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 02/04/2020] [Accepted: 02/17/2020] [Indexed: 10/25/2022]
Abstract
The locus coeruleus (LC) is a pontine nucleus important for respiratory control and central chemoreception. It is affected in Alzheimer's disease (AD) and alteration of LC cell function may account for respiratory problems observed in AD patients. In the current study, we tested the electrophysiological properties and CO2/pH sensitivity of LC neurons in a model for AD. Sporadic AD was induced in rats by intracerebroventricular injection of 2 mg/kg streptozotocin (STZ), which induces behavioral and molecular impairments found in AD. LC neurons were recorded using the patch clamp technique and tested for responses to CO2 (10% CO2, pH = 7.0). The majority (~60%) of noradrenergic LC neurons in adult rats were inhibited by CO2 exposure as indicated by a significant decrease in action potential (AP) discharge to step depolarizations. The STZ-AD rat model had a greater sensitivity to CO2 than controls. The increased CO2-sensitivity was demonstrated by a significantly stronger inhibition of activity during hypercapnia that was in part due to hyperpolarization of the resting membrane potential. Reduction of AP discharge in both groups was generally accompanied by lower LC network activity, depolarized AP threshold, increased AP repolarization, and increased current through a subpopulation of voltage-gated K+ channels (KV). The latter was indicated by enhanced transient KV currents particularly in the STZ-AD group. Interestingly, steady-state KV currents were reduced under hypercapnia, a change that would favor enhanced AP discharge. However, the collective response of most LC neurons in adult rats, and particularly those in the STZ-AD group, was inhibited by CO2.
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Affiliation(s)
- Mariane C Vicente
- Department of Physiology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO, USA; Department of Animal Morphology and Physiology, Sao Paulo State University-UNESP/FCAV at Jaboticabal, SP, Brazil
| | - Chuma M Humphrey
- Department of Biology, Truman State University, Kirksville, MO, USA
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, Sao Paulo State University-UNESP/FCAV at Jaboticabal, SP, Brazil
| | - Tim D Ostrowski
- Department of Physiology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO, USA.
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21
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Extensive Inhibitory Gating of Viscerosensory Signals by a Sparse Network of Somatostatin Neurons. J Neurosci 2019; 39:8038-8050. [PMID: 31471471 DOI: 10.1523/jneurosci.3036-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 08/07/2019] [Accepted: 08/10/2019] [Indexed: 01/07/2023] Open
Abstract
Integration and modulation of primary afferent sensory information begins at the first terminating sites within the CNS, where central inhibitory circuits play an integral role. Viscerosensory information is conveyed to the nucleus of the solitary tract (NTS) where it initiates neuroendocrine, behavioral, and autonomic reflex responses that ensure optimal internal organ function. This excitatory input is modulated by diverse, local inhibitory interneurons, whose functions are not clearly understood. Here we show that, in male rats, 65% of somatostatin-expressing (SST) NTS neurons also express GAD67, supporting their likely role as inhibitory interneurons. Using whole-cell recordings of NTS neurons, from horizontal brainstem slices of male and female SST-yellow fluorescent protein (YFP) and SST-channelrhodopsin 2 (ChR2)-YFP mice, we quantified the impact of SST-NTS neurons on viscerosensory processing. Light-evoked excitatory photocurrents were reliably obtained from SST-ChR2-YFP neurons (n = 16) and the stimulation-response characteristics determined. Most SST neurons (57%) received direct input from solitary tract (ST) afferents, indicating that they form part of a feedforward circuit. All recorded SST-negative NTS neurons (n = 72) received SST-ChR2 input. ChR2-evoked PSCs were largely inhibitory and, in contrast to previous reports, were mediated by both GABA and glycine. When timed to coincide, the ChR2-activated SST input suppressed ST-evoked action potentials at second-order NTS neurons, demonstrating strong modulation of primary viscerosensory input. These data indicate that the SST inhibitory network innervates broadly within the NTS, with the potential to gate viscerosensory input to powerfully alter autonomic reflex function and other behaviors.SIGNIFICANCE STATEMENT Sensory afferent input is modulated according to state. For example the baroreflex is altered during a stress response or exercise, but the basic mechanisms underpinning this sensory modulation are not fully understood in any sensory system. Here we demonstrate that the neuronal processing of viscerosensory information begins with synaptic gating at the first central synapse with second-order neurons in the NTS. These data reveal that the somatostatin subclass of inhibitory interneurons are driven by visceral sensory input to play a major role in gating viscerosensory signals, placing them within a feedforward circuit within the NTS.
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Iovino L, Mutolo D, Cinelli E, Contini M, Pantaleo T, Bongianni F. Breathing stimulation mediated by 5-HT1A and 5-HT3 receptors within the preBötzinger complex of the adult rabbit. Brain Res 2019; 1704:26-39. [DOI: 10.1016/j.brainres.2018.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 09/10/2018] [Accepted: 09/18/2018] [Indexed: 02/06/2023]
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Wu HF, Chen YJ, Chu MC, Hsu YT, Lu TY, Chen IT, Chen PS, Lin HC. Deep Brain Stimulation Modified Autism-Like Deficits via the Serotonin System in a Valproic Acid-Induced Rat Model. Int J Mol Sci 2018; 19:ijms19092840. [PMID: 30235871 PMCID: PMC6164279 DOI: 10.3390/ijms19092840] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 09/13/2018] [Accepted: 09/18/2018] [Indexed: 01/30/2023] Open
Abstract
Deep brain stimulation (DBS) is known to be a promising treatment for resistant depression, which acts via the serotonin (5-hydroxytryptamine, 5-HT) system in the infralimbic prefrontal cortex (ILPFC). Previous study revealed that dysfunction of brain 5-HT homeostasis is related to a valproate (VPA)-induced rat autism spectrum disorder (ASD) model. Whether ILPFC DBS rescues deficits in VPA-induced offspring through the 5-HT system is not known. Using VPA-induced offspring, we therefore explored the effect of DBS in autistic phenotypes and further investigated the underlying mechanism. Using combined behavioral and molecular approaches, we observed that applying DBS and 5-HT1A receptor agonist treatment with 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) reversed sociability deficits, anxiety and hyperactivity in the VPA-exposed offspring. We then administered the selective 5-HT1A receptor antagonist N-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide maleate (WAY 100635), following which the effect of DBS in terms of improving autistic behaviors was blocked in the VPA-exposed offspring. Furthermore, we found that both 8-OH-DPAT and DBS treatment rescued autistic behaviors by decreasing the expressions of NR2B subunit of N-methyl-D-aspartate receptors (NMDARs) and the β₃ subunit of γ-aminobutyric acid type A receptors (GABAAR) in the PFC region. These results provided the first evidence of characteristic behavioral changes in VPA-induced offspring caused by DBS via the 5-HT system in the ILPFC.
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Affiliation(s)
- Han-Fang Wu
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - Yi-Ju Chen
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - Ming-Chia Chu
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - Ya-Ting Hsu
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - Ting-Yi Lu
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - I-Tuan Chen
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
| | - Po See Chen
- Department of Psychiatry, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan.
- Addiction Research Center, National Cheng Kung University, Tainan 70101, Taiwan.
| | - Hui-Ching Lin
- Department and Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
- Brain Research Center, National Yang-Ming University, Taipei 11221, Taiwan.
- Ph.D. Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan.
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Abstract
Currently, panic disorder (PD) is considered a mental disorder based on the assumptions that panic attacks (PAs) are “false alarms” that arise from abnormally sensitive defense systems in the central nervous system and that PD is treated with therapies specifically acting on anxiety or fear mechanisms. This article aims to propose an alternative perspective based on the results of some experimental studies. Our heuristic proposal suggests not only that PD may be a mental disorder but also that patients with PD have real abnormal body functioning, mainly involving cardiorespiratory and balance systems, leading to a decline in global physical fitness. PAs, as well as physical symptoms or discomfort in some environmental situations, may be “real alarms” signaling that the adaptability resources of an organism are insufficient to respond appropriately to some internal or external changes, thus representing the transient conscious awareness of an imbalance in body functioning. The antipanic properties of several modern treatments for PD may include their beneficial effects on body functions. Although anxiety or fear mechanisms are evidently involved in PD, we hypothesize that a reduction of physical fitness is the “primum movens” of PD, while anxiety or fear is induced and sustained by repeated signals of impaired body functioning. We propose considering panic in a broader perspective that offers a central role to the body and to contemplate the possible role of somatic treatments in PD.
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Affiliation(s)
- Giampaolo Perna
- Department of Clinical Neurosciences, Hermanas Hospitalarias, Villa San Benedetto Menni Hospital, FoRiPsi, Albese con Cassano, Como, Italy.,Department of Psychiatry and Neuropsychology, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, Netherlands.,Department of Psychiatry and Behavioral Sciences, Leonard Miller School of Medicine, Miami University, Miami, USA
| | - Daniela Caldirola
- Department of Clinical Neurosciences, Hermanas Hospitalarias, Villa San Benedetto Menni Hospital, FoRiPsi, Albese con Cassano, Como, Italy
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Guo JD, O'Flaherty BM, Rainnie DG. Serotonin gating of cortical and thalamic glutamate inputs onto principal neurons of the basolateral amygdala. Neuropharmacology 2017; 126:224-232. [PMID: 28899729 DOI: 10.1016/j.neuropharm.2017.09.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 08/31/2017] [Accepted: 09/08/2017] [Indexed: 12/13/2022]
Abstract
The basolateral amygdala (BLA) is a key site for crossmodal association of sensory stimuli and an important relay in the neural circuitry of emotion. Indeed, the BLA receives substantial glutamatergic inputs from multiple brain regions including the prefrontal cortex and thalamic nuclei. Modulation of glutamatergic transmission in the BLA regulates stress- and anxiety-related behaviors. Serotonin (5-HT) also plays an important role in regulating stress-related behavior through activation of both pre- and postsynaptic 5-HT receptors. Multiple 5-HT receptors are expressed in the BLA, where 5-HT has been reported to modulate glutamatergic transmission. However, the 5-HT receptor subtype mediating this effect is not yet clear. The aim of this study was to use patch-clamp recordings from BLA neurons in an ex vivo slice preparation to examine 1) the effect of 5-HT on extrinsic sensory inputs, and 2) to determine if any pathway specificity exists in 5-HT regulation of glutamatergic transmission. Two independent input pathways into the BLA were stimulated: the external capsule to mimic cortical input, and the internal capsule to mimic thalamic input. Bath application of 5-HT reversibly reduced the amplitude of evoked excitatory postsynaptic currents (eEPSCs) induced by stimulation of both pathways. The decrease was associated with an increase in the paired-pulse ratio and coefficient of variation of eEPSC amplitude, suggesting 5-HT acts presynaptically. Moreover, the effect of 5-HT in both pathways was mimicked by the selective 5-HT1B receptor agonist CP93129, but not by the 5-HT1A receptor agonist 8-OH DPAT. Similarly the effect of exogenous 5-HT was blocked by the 5-HT1B receptor antagonist GR55562, but not affected by the 5-HT1A receptor antagonist WAY 100635 or the 5-HT2 receptor antagonists pirenperone and MDL 100907. Together these data suggest 5-HT gates cortical and thalamic glutamatergic inputs into the BLA by activating presynaptic 5-HT1B receptors.
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Affiliation(s)
- Ji-Dong Guo
- Division of Behavioral Neuroscience & Psychiatric Disorders, Yerkes National Primate Research Center, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA.
| | - Brendan M O'Flaherty
- Division of Behavioral Neuroscience & Psychiatric Disorders, Yerkes National Primate Research Center, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Donald G Rainnie
- Division of Behavioral Neuroscience & Psychiatric Disorders, Yerkes National Primate Research Center, Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA, USA
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Matott MP, Kline DD, Hasser EM. Glial EAAT2 regulation of extracellular nTS glutamate critically controls neuronal activity and cardiorespiratory reflexes. J Physiol 2017; 595:6045-6063. [PMID: 28677303 PMCID: PMC5577520 DOI: 10.1113/jp274620] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 06/27/2017] [Indexed: 01/24/2023] Open
Abstract
KEY POINTS Excitatory amino acid transporter 2 (EAAT2) is present on astrocytes in the nucleus tractus solitarii (nTS), an important nucleus in cardiorespiratory control. Its specific role in influencing nTS neuronal activity and thereby basal and reflex cardiorespiratory function is unknown. The specific role of nTS EAAT2 was determined via whole animal and brainstem slice patch clamp experiments. Astrocytic EAAT2 buffers basal glutamate activation of AMPA-type glutamate receptors and therefore decreases baseline excitability of nTS neurons. EAAT2 modulates cardiorespiratory control and tempers excitatory cardiorespiratory responses to activation of the peripheral chemoreflex. This study supports the concept that nTS astrocyte transporters influence sympathetic nervous system activity and cardiorespiratory reflex function in health and disease. ABSTRACT Glutamatergic signalling is critical in the nucleus tractus solitarii (nTS) for cardiorespiratory homeostasis and initiation of sensory reflexes, including the chemoreflex activated during hypoxia. Maintenance of nTS glutamate concentration occurs in part through astrocytic excitatory amino acid transporters (EAATs). We previously established the importance of EAATs in the nTS by demonstrating their inhibition produced neuronal excitation to alter basal cardiorespiratory function. Since EAAT2 is the most expressed EAAT in the nTS, this study specifically determined EAAT2's role in nTS astrocytes, its influence on neuronal and synaptic properties, and ultimately on basal and reflex cardiorespiratory function. The EAAT2-specific antagonist dihydrokainate (DHK) was microinjected into the anaesthetized rat nTS or applied to rat nTS slices. DHK produced depressor, bradycardic and sympathoinhibitory responses and reduced neural respiration in the intact rat, mimicking responses to glutamate excitation. DHK also enhanced responses to glutamate microinjection. DHK elevated extracellular nTS glutamate concentration, depolarized neurons and enhanced spontaneous EPSCs. EAAT2 block also augmented action potential discharge in chemosensitive nTS neurons. Glial recordings confirmed EAAT2 is functional on nTS astrocytes. Neuronal excitation and cardiorespiratory effects following EAAT2 inhibition were due to activation of putative extrasynaptic AMPA receptors as their antagonism blocked DHK responses in the intact rat nTS and the slice. The DHK-induced elevation of extracellular glutamate and neuronal excitation augmented chemoreflex-mediated pressor, sympathoexcitatory and minute neural ventilation responses in the rat. These data shed new light on the important role astrocytic EAAT2 plays on buffering nTS excitation and overall cardiorespiratory function.
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Affiliation(s)
- Michael P. Matott
- Department of Biomedical Sciences, Dalton Cardiovascular Research CenterUniversity of Missouri134 Research Park DriveColumbiaMO65211USA
| | - David D. Kline
- Department of Biomedical Sciences, Dalton Cardiovascular Research CenterUniversity of Missouri134 Research Park DriveColumbiaMO65211USA
| | - Eileen M. Hasser
- Department of Biomedical SciencesDepartment of Medical Pharmacology and Physiology, Dalton Cardiovascular Research CenterUniversity of Missouri134 Research Park DriveColumbiaMO65211USA
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Ostrowski TD, Dantzler HA, Polo-Parada L, Kline DD. H 2O 2 augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels. Am J Physiol Cell Physiol 2017; 312:C651-C662. [PMID: 28274920 DOI: 10.1152/ajpcell.00195.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 03/06/2017] [Accepted: 03/08/2017] [Indexed: 12/20/2022]
Abstract
Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H2O2) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H2O2 on cytosolic Ca2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H2O2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca2+ concentration ([Ca2+]i). The H2O2-mediated increase in [Ca2+]i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca2+ source. The effect, however, was abolished by removal of extracellular Ca2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca2+ channels (VGCCs) as targets for H2O2 modulation. Recording of the total voltage-dependent Ca2+ current confirmed H2O2 enhanced Ca2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H2O2 The number of responder cells to H2O2 also decreased in the presence of dithiothreitol, suggesting the actions of H2O2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H2O2 increases [Ca2+]i and its Ca2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices.
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Affiliation(s)
- Tim D Ostrowski
- Department of Physiology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, Missouri.,Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Heather A Dantzler
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Luis Polo-Parada
- Department of Medical Pharmacology and Physiology, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri; and
| | - David D Kline
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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28
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Ebel DL, Torkilsen CG, Ostrowski TD. Blunted Respiratory Responses in the Streptozotocin-Induced Alzheimer's Disease Rat Model. J Alzheimers Dis 2017; 56:1197-1211. [PMID: 28106557 DOI: 10.3233/jad-160974] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Alzheimer's disease (AD) is known for the progressive decline of cognition and memory. In addition to these disease-defining symptoms, impairment of respiratory function is frequently observed and often expressed by sleep-disordered breathing or reduced ability to adjust respiration when oxygen demand is elevated. The mechanisms for this are widely unknown. Postmortem analysis from the brainstem of AD patients reveals pathological alterations, including in nuclei responsible for respiratory control. In this study, we analyzed respiratory responses and morphological changes in brainstem nuclei following intracerebroventricular (ICV) injections of streptozotocin (STZ), a rat model commonly used to mimic sporadic AD. ICV-STZ induced significant astrogliosis in the commissural part of the nucleus tractus solitarii, an area highly involved in respiration control. The astrogliosis was identified by a significant increase in S100B-immunofluorescence that is similar to the astrogliosis found in the CA1 region of the hippocampus. Using plethysmography, the control group displayed a typical age-dependent decrease of ventilation that was absent in the STZ rat group. This is indicative of elevated minute ventilation at rest after STZ treatment. Peripheral chemoreflex responses were significantly blunted in STZ rats as seen by a reduced respiratory rate and minute ventilation to hypoxia. Central chemoreflex responses to hypercapnia, on the other hand, only decreased in respiratory rate following STZ treatment. Overall, our results show that ICV-STZ induces respiratory dysfunction at rest and in response to hypoxia. This provides a new tool to study the underlying mechanisms of breathing disorders in clinical AD.
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Morinaga R, Nakamuta N, Yamamoto Y. Hypoxia-induced increases in serotonin-immunoreactive nerve fibers in the medulla oblongata of the rat. Acta Histochem 2016; 118:806-817. [PMID: 27825705 DOI: 10.1016/j.acthis.2016.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 10/25/2016] [Accepted: 10/27/2016] [Indexed: 10/20/2022]
Abstract
Hypoxia induces respiratory responses in mammals and serotonergic neurons in the medulla oblongata participate in respiratory control. However, the morphological changes in serotonergic neurons induced by hypoxia have not yet been examined and respiratory controls of serotonergic neurons have not been clarified. We herein investigated the distribution of immunoreactivity for serotonin (5-hydroxytryptamine; 5-HT) in the medulla oblongata of control rats and rats exposed to 1-6h of hypoxia (10% O2). We also examined the medulla oblongata by multiple immunofluorescence labeling for 5-HT, neurokinin 1 receptors (NK1R), a marker for some respiratory neurons in the pre-Bötzinger complex (PBC), and dopamine β-hydroxylase (DBH), a marker for catecholaminergic neurons. The number of 5-HT-immunoreactive nerve cell bodies in the raphe nuclei was higher in rats exposed to hypoxia than in control rats. The number of 5-HT-immunoreactive nerve fibers significantly increased in the rostral ventrolateral medulla of rats exposed to 1-6h of hypoxia, caudal ventrolateral medulla of rats exposed to 2-6h of hypoxia, and lateral part of the nucleus of the solitary tract and dorsal motor nucleus of the vagus nerve of rats exposed to 1-2h of hypoxia. Multiple immunofluorescence labeling showed that 5-HT-immunoreactive nerve fibers were close to NK1R-immunoreactive neurons in ventrolateral medulla and to DBH-immunoreactive neurons in the medulla. These results suggest that serotonergic neurons partly regulate respiratory control under hypoxic conditions by modulating the activity of NK1R-expressing and catecholaminergic neurons.
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Sévoz-Couche C, Brouillard C. Key role of 5-HT 3 receptors in the nucleus tractus solitarii in cardiovagal stress reactivity. Neurosci Biobehav Rev 2016; 74:423-432. [PMID: 27131969 DOI: 10.1016/j.neubiorev.2016.04.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 04/18/2016] [Accepted: 04/20/2016] [Indexed: 01/01/2023]
Abstract
Serotonin plays a modulatory role in central control of the autonomic nervous system (ANS). The nucleus tractus solitarii (NTS) in the medulla is an area of viscerosomatic integration innervated by both central and peripheral serotonergic fibers. Influences from different origins therefore trigger the release of serotonin into the NTS and exert multiple influences on the ANS. This major influence on the ANS is also mediated by activation of several receptors in the NTS. In particular, the NTS is the central zone with the highest density of serotonin3 (5-HT3) receptors. In this review, we present evidence that 5-HT3 receptors in the NTS play a key role in one of the crucial homeostatic responses to acute and chronic stress: inhibitory modulation of the parasympathetic component of the ANS. The possible functional interactions of 5-HT3 receptors with GABAA and NK1 receptors in the NTS are also discussed.
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Affiliation(s)
- Caroline Sévoz-Couche
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France.
| | - Charly Brouillard
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
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Activation of 5-hyrdoxytryptamine 7 receptors within the rat nucleus tractus solitarii modulates synaptic properties. Brain Res 2016; 1635:12-26. [PMID: 26779891 DOI: 10.1016/j.brainres.2016.01.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 01/08/2016] [Accepted: 01/09/2016] [Indexed: 12/22/2022]
Abstract
Serotonin (5-HT) is a potent neuromodulator with multiple receptor types within the cardiorespiratory system, including the nucleus tractus solitarii (nTS)--the central termination site of visceral afferent fibers. The 5-HT7 receptor facilitates cardiorespiratory reflexes through its action in the brainstem and likely in the nTS. However, the mechanism and site of action for these effects is not clear. In this study, we examined the expression and function of 5-HT7 receptors in the nTS of Sprague-Dawley rats. 5-HT7 receptor mRNA and protein were identified across the rostrocaudal extent of the nTS. To determine 5-HT7 receptor function, we examined nTS synaptic properties following 5-HT7 receptor activation in monosynaptic nTS neurons in the in vitro brainstem slice preparation. Application of 5-HT7 receptor agonists altered tractus solitarii evoked and spontaneous excitatory postsynaptic currents which were attenuated with a selective 5-HT7 receptor antagonist. 5-HT7 receptor-mediated changes in excitatory postsynaptic currents were also altered by block of 5-HT1A and GABAA receptors. Interestingly, 5-HT7 receptor activation also reduced the amplitude but not frequency of GABAA-mediated inhibitory currents. Together these results indicate a complex role for 5-HT7 receptors in the nTS that mediate its diverse effects on cardiorespiratory parameters.
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32
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Matott MP, Ruyle BC, Hasser EM, Kline DD. Excitatory amino acid transporters tonically restrain nTS synaptic and neuronal activity to modulate cardiorespiratory function. J Neurophysiol 2015; 115:1691-702. [PMID: 26719090 DOI: 10.1152/jn.01054.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 12/24/2015] [Indexed: 11/22/2022] Open
Abstract
The nucleus tractus solitarii (nTS) is the initial central termination site for visceral afferents and is important for modulation and integration of multiple reflexes including cardiorespiratory reflexes. Glutamate is the primary excitatory neurotransmitter in the nTS and is removed from the extracellular milieu by excitatory amino acid transporters (EAATs). The goal of this study was to elucidate the role of EAATs in the nTS on basal synaptic and neuronal function and cardiorespiratory regulation. The majority of glutamate clearance in the central nervous system is believed to be mediated by astrocytic EAAT 1 and 2. We confirmed the presence of EAAT 1 and 2 within the nTS and their colocalization with astrocytic markers. EAAT blockade withdl-threo-β-benzyloxyaspartic acid (TBOA) produced a concentration-related depolarization, increased spontaneous excitatory postsynaptic current (EPSC) frequency, and enhanced action potential discharge in nTS neurons. Solitary tract-evoked EPSCs were significantly reduced by EAAT blockade. Microinjection of TBOA into the nTS of anesthetized rats induced apneic, sympathoinhibitory, depressor, and bradycardic responses. These effects mimicked the response to microinjection of exogenous glutamate, and glutamate responses were enhanced by EAAT blockade. Together these data indicate that EAATs tonically restrain nTS excitability to modulate cardiorespiratory function.
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Affiliation(s)
- Michael P Matott
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Brian C Ruyle
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Eileen M Hasser
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri; and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - David D Kline
- Department of Biomedical Sciences, University of Missouri, Columbia, Missouri, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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33
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Blecharz-Klin K, Joniec-Maciejak I, Jawna K, Pyrzanowska J, Piechal A, Wawer A, Widy-Tyszkiewicz E. Developmental exposure to paracetamol causes biochemical alterations in medulla oblongata. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2015; 40:369-374. [PMID: 26233562 DOI: 10.1016/j.etap.2015.07.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 07/02/2015] [Accepted: 07/03/2015] [Indexed: 06/04/2023]
Abstract
The effect and safety of prenatal and early life administration of paracetamol - routinely used over-the-counter antipyretic and analgesic medication on monoamines content and balance of amino acids in the medulla oblongata is still unknown. In this study we have determined the level of neurotransmitters in this structure in two-month old Wistar male rats exposed to paracetamol in the dose of 5 (P5, n=10) or 15mg/kg b.w. (P15, n=10) during prenatal period, lactation and till the end of the second month of life. Control group received drinking water (Con, n=10). Monoamines, their metabolites and amino acids concentration in medulla oblongata of rats were determined using high performance liquid chromatography (HPLC) in 60 postnatal day (PND60). This experiment shows that prenatal and early life paracetamol exposure modulates neurotransmission associated with serotonergic, noradrenergic and dopaminergic system in medulla oblongata. Reduction of alanine and taurine levels has also been established.
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Affiliation(s)
- Kamilla Blecharz-Klin
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Ilona Joniec-Maciejak
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Katarzyna Jawna
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Justyna Pyrzanowska
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Agnieszka Piechal
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Adriana Wawer
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland
| | - Ewa Widy-Tyszkiewicz
- Department of Experimental and Clinical Pharmacology, Medical University of Warsaw, Centre for Preclinical Research and Technology CePT, Banacha 1B, 02-097 Warsaw, Poland.
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Vantrease JE, Dudek N, DonCarlos LL, Scrogin KE. 5-HT1A receptors of the nucleus tractus solitarii facilitate sympathetic recovery following hypotensive hemorrhage in rats. Am J Physiol Heart Circ Physiol 2015; 309:H335-44. [PMID: 25980022 DOI: 10.1152/ajpheart.00117.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 05/13/2015] [Indexed: 11/22/2022]
Abstract
The role of serotonin in the hemodynamic response to blood loss remains controversial. Caudal raphe serotonin neurons are activated during hypotensive hemorrhage, and their destruction attenuates sympathetic increases following blood loss in unanesthetized rats. Caudal raphe neurons provide serotonin-positive projections to the nucleus tractus solitarii (NTS), and disruption of serotonin-positive nerve terminals in the NTS attenuates sympathetic recovery following hemorrhage. Administration of 5-HT1A-receptor agonists following hemorrhage augments sympathetic-mediated increases in venous tone and tissue hypoxia. These findings led us to hypothesize that severe blood loss promotes activation of 5-HT1A receptors in the NTS, which facilitates sympathetic recovery and peripheral tissue perfusion. Here, we developed an adeno-associated viral vector encoding an efficacious small hairpin RNA sequence targeting the rat 5-HT1A receptor. Unanesthetized rats subjected to NTS injection of the anti-rat 5-HT1A small hairpin RNA-encoding vector 4 wk prior showed normal blood pressure recovery, but an attenuated recovery of renal sympathetic nerve activity (-6.4 ± 12.9 vs. 42.6 ± 15.6% baseline, P < 0.05) 50 min after 21% estimated blood volume withdrawal. The same rats developed increased tissue hypoxia after hemorrhage, as indicated by prolonged elevations in lactate (2.77 ± 0.5 vs. 1.34 ± 0.2 mmol/l, 60 min after start of hemorrhage, P < 0.05). 5-HT1A mRNA levels in the commissural NTS were directly correlated with renal sympathetic nerve activity (P < 0.01) and inversely correlated with lactate (P < 0.05) 60 min after start of hemorrhage. The data suggest that 5-HT1A receptors in the commissural NTS facilitate tissue perfusion after blood loss likely by increasing sympathetic-mediated venous return.
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Affiliation(s)
- Jaime E Vantrease
- Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Nichole Dudek
- Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Lydia L DonCarlos
- Department of Cellular and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Neuroscience Institute, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
| | - Karie E Scrogin
- Department of Molecular Pharmacology and Therapeutics, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; Department of Cellular and Molecular Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois; and Neuroscience Institute, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois
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Hosford PS, Millar J, Ramage AG. Cardiovascular afferents cause the release of 5-HT in the nucleus tractus solitarii; this release is regulated by the low- (PMAT) not the high-affinity transporter (SERT). J Physiol 2015; 593:1715-29. [PMID: 25694117 PMCID: PMC4386968 DOI: 10.1113/jphysiol.2014.285312] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 01/16/2015] [Indexed: 12/31/2022] Open
Abstract
The nucleus tractus solitarii (NTS) integrates inputs from cardiovascular afferents and thus is crucial for cardiovascular homeostasis. These afferents primarily release glutamate, although 5-HT has also been shown to play a role in their actions. Using fast-cyclic voltammetry, an increase in 5-HT concentrations (range 12-50 nm) could be detected in the NTS in anaesthetized rats in response to electrical stimulation of the vagus and activation of cardiopulmonary, chemo- and baroreceptor reflexes. This 5-HT signal was not potentiated by the serotonin transporter (SERT) or the noradrenaline transporter (NET) inhibitors citalopram and desipramine (1 mg kg(-1) ). However, decynium-22 (600 μg kg(-1) ), an organic cation 3 transporter (OCT3)/plasma membrane monoamine transporter (PMAT) inhibitor, increased the 5-HT signal by 111 ± 21% from 29 ± 10 nm. The effectiveness of these inhibitors was tested against the removal time of 5-HT and noradrenaline applied by microinjection to the NTS. Citalopram and decynium-22 attenuated the removal of 5-HT but not noradrenaline, whereas desipramine had the reverse action. The OCT3 inhibitor corticosterone (10 mg kg(-1) ) had no effect. Blockade of glutamate receptors with topical kynurenate (10-50 nm) reduced the vagally evoked 5-HT signal by 50%, indicating that this release was from at least two sources. It is concluded that vagally evoked 5-HT release is under the regulation of the high-capacity, low-affinity transporter PMAT, not the low-capacity, high-affinity transporter SERT. This is the first demonstration that PMAT may be playing a physiological role in the regulation of 5-HT transmission and this could indicate that 5-HT is acting, in part, as a volume transmitter within the NTS.
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Affiliation(s)
- Patrick S Hosford
- Department of Neuroscience, Physiology and Pharmacology, University College LondonGower Street, London, WC1E 6BT, UK
| | - Julian Millar
- Department of Medical Education, Queen Mary's School of Medicine and DentistryWhitechapel, London, E1 2AD, UK
| | - Andrew G Ramage
- Department of Neuroscience, Physiology and Pharmacology, University College LondonGower Street, London, WC1E 6BT, UK
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