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Bauer MB, Currie KPM. Serotonin and the serotonin transporter in the adrenal gland. VITAMINS AND HORMONES 2023; 124:39-78. [PMID: 38408804 PMCID: PMC11217909 DOI: 10.1016/bs.vh.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
The adrenal glands are key components of the mammalian endocrine system, helping maintain physiological homeostasis and the coordinated response to stress. Each adrenal gland has two morphologically and functionally distinct regions, the outer cortex and inner medulla. The cortex is organized into three concentric zones which secrete steroid hormones, including aldosterone and cortisol. Neural crest-derived chromaffin cells in the medulla are innervated by preganglionic sympathetic neurons and secrete catecholamines (epinephrine, norepinephrine) and neuropeptides into the bloodstream, thereby functioning as the neuroendocrine arm of the sympathetic nervous system. In this article we review serotonin (5-HT) and the serotonin transporter (SERT; SLC6A4) in the adrenal gland. In the adrenal cortex, 5-HT, primarily sourced from resident mast cells, acts as a paracrine signal to stimulate aldosterone and cortisol secretion through 5-HT4/5-HT7 receptors. Medullary chromaffin cells contain a small amount of 5-HT due to SERT-mediated uptake and express 5-HT1A receptors which inhibit secretion. The atypical mechanism of the 5-HT1A receptors and interaction with SERT fine tune this autocrine pathway to control stress-evoked catecholamine secretion. Receptor-independent signaling by SERT/intracellular 5-HT modulates the amount and kinetics of transmitter release from single vesicle fusion events. SERT might also influence stress-evoked upregulation of tyrosine hydroxylase transcription. Transient signaling via 5-HT3 receptors during embryonic development can limit the number of chromaffin cells found in the mature adrenal gland. Together, this emerging evidence suggests that the adrenal medulla is a peripheral hub for serotonergic control of the sympathoadrenal stress response.
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Affiliation(s)
- Mary Beth Bauer
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, South Broadway, Camden, NJ, United States
| | - Kevin P M Currie
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, South Broadway, Camden, NJ, United States.
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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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Panteleev SS, Sivachenko IB, Lyubashina OA. The central effects of buspirone on abdominal pain in rats. Neurogastroenterol Motil 2018; 30:e13431. [PMID: 30101506 DOI: 10.1111/nmo.13431] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/08/2018] [Accepted: 06/24/2018] [Indexed: 12/28/2022]
Abstract
BACKGROUND Buspirone, a partial agonist of the 5-HT1a receptor (5-HT1a R), owing to potential antinociceptive properties may be useful in treatment of abdominal pain in IBS patients. The pain-related effects of buspirone are mediated via the 5-HT1a Rs, specifically located within the ventrolateral medulla (VLM). The most animal studies of the 5-HT1a R involvement in pain control have been carried out with somatic behavioral tests. The 5-HT1a R contribution in visceral pain transmission within the VLM is unclear. The objective of our study was to evaluate the 5-HT1a R contribution in abdominal pain transmission within the VLM. METHODS Using animal model of abdominal pain (urethane-anaesthetized rats), based on the noxious colorectal distension (CRD) as pain stimulus we studied effects of buspirone (1.0-4.0 mg kg-1 , iv) on the CRD-induced VLM neuron and blood pressure responses as markers of abdominal pain before and after the 5-HT1a R blockade by antagonist, WAY 100,635. RESULTS The CRD induced a significant increase in VLM neuron activity up to 201.5 ± 18.0% and depressor reactions up to 68 ± 1.8% of baseline. Buspirone (1.0-4.0 mg kg-1 , iv) resulted in an inhibition of the CRD-induced neuron responses which were changed inversely with dose increase and decreased depressor reactions directly with dose increase. These effects were antagonized by intracerebroventricular WAY 100,635. CONCLUSION Buspirone exerts complex biphasic action on the pain-related VLM neuron activity inversely depending on dose. The final effect of buspirone depends on the functional balance between of activation the pre- and postsynaptic 5-HT1a Rs in mediating pain control networks.
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Affiliation(s)
- S S Panteleev
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology, Russian Academy of Sciences, Saint Petersburg, Russia.,Department of Neuropharmacology, Valdman Institute of Pharmacology, First Saint-Petersburg Pavlov State Medical University, Saint Petersburg, Russia
| | - I B Sivachenko
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology, Russian Academy of Sciences, Saint Petersburg, Russia
| | - O A Lyubashina
- Laboratory of Cortico-Visceral Physiology, Pavlov Institute of Physiology, Russian Academy of Sciences, Saint Petersburg, Russia.,Department of Neuropharmacology, Valdman Institute of Pharmacology, First Saint-Petersburg Pavlov State Medical University, Saint Petersburg, Russia
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Brindley RL, Bauer MB, Blakely RD, Currie KP. Serotonin and Serotonin Transporters in the Adrenal Medulla: A Potential Hub for Modulation of the Sympathetic Stress Response. ACS Chem Neurosci 2017; 8:943-954. [PMID: 28406285 PMCID: PMC5541362 DOI: 10.1021/acschemneuro.7b00026] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Serotonin (5-HT) is an important neurotransmitter in the central nervous system where it modulates circuits involved in mood, cognition, movement, arousal, and autonomic function. The 5-HT transporter (SERT; SLC6A4) is a key regulator of 5-HT signaling, and genetic variations in SERT are associated with various disorders including depression, anxiety, and autism. This review focuses on the role of SERT in the sympathetic nervous system. Autonomic/sympathetic dysfunction is evident in patients with depression, anxiety, and other diseases linked to serotonergic signaling. Experimentally, loss of SERT function (SERT knockout mice or chronic pharmacological block) has been reported to augment the sympathetic stress response. Alterations to serotonergic signaling in the CNS and thus central drive to the peripheral sympathetic nervous system are presumed to underlie this augmentation. Although less widely recognized, SERT is robustly expressed in chromaffin cells of the adrenal medulla, the neuroendocrine arm of the sympathetic nervous system. Adrenal chromaffin cells do not synthesize 5-HT but accumulate small amounts by SERT-mediated uptake. Recent evidence demonstrated that 5-HT1A receptors inhibit catecholamine secretion from adrenal chromaffin cells via an atypical mechanism that does not involve modulation of cellular excitability or voltage-gated Ca2+ channels. This raises the possibility that the adrenal medulla is a previously unrecognized peripheral hub for serotonergic control of the sympathetic stress response. As a framework for future investigation, a model is proposed in which stress-evoked adrenal catecholamine secretion is fine-tuned by SERT-modulated autocrine 5-HT signaling.
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Affiliation(s)
- Rebecca L. Brindley
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mary Beth Bauer
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Randy D. Blakely
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, and Florida Atlantic University Brain Institute, Jupiter, FL, USA
| | - Kevin P.M. Currie
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
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Lemes EV, Colombari E, Zoccal DB. Generation of active expiration by serotoninergic mechanisms of the ventral medulla of rats. J Appl Physiol (1985) 2016; 121:1135-1144. [PMID: 27660299 DOI: 10.1152/japplphysiol.00470.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/19/2016] [Accepted: 09/19/2016] [Indexed: 01/16/2023] Open
Abstract
Abdominal expiratory activity is absent at rest and is evoked during metabolic challenges, such as hypercapnia and hypoxia, or after the exposure to intermittent hypoxia (IH). The mechanisms engaged during this process are not completely understood. In this study, we hypothesized that serotonin (5-HT), acting in the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG), is able to generate active expiration. In anesthetized (urethane, ip), tracheostomized, spontaneously-breathing adult male Holtzman rats we microinjected a serotoninergic agonist and antagonist bilaterally in the RTN/pFRG and recorded diaphragm and abdominal muscle activities. We found that episodic (3 times, 5 min apart), but not single microinjections of 5-HT (1 mM) in the RTN/pFRG elicited an enduring (>30 min) increase in abdominal activity. This response was amplified in vagotomized rats and blocked by previous 5-HT receptor antagonism with ketanserin (10 µM). Episodic 5-HT microinjections in the RTN/pFRG also potentiated the inspiratory and expiratory reflex responses to hypercapnia. The antagonism of 5-HT receptors in the RTN/pFRG also prevented the long-term facilitation (>30 min) of abdominal activity in response to acute IH exposure (10 × 6-7% O for 45 s every 5 min). Our findings indicate the activation of serotoninergic mechanisms in the RTN/pFRG is sufficient to increase abdominal expiratory activity at resting conditions and required for the emergence of active expiration after IH in anesthetized animals.
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Affiliation(s)
- Eduardo V Lemes
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
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Fajemiroye JO, Amaral NO, da Silva EF, Galdino PM, de Oliveira TS, Ghedini PC, Zjawiony JK, Costa EA, Pedrino GR, Menegatti R. Hypotensive and antihypertensive potential of 4-[(1-phenyl-1H-pyrazol-4-yl) methyl]1-piperazine carboxylic acid ethyl ester: a piperazine derivative. Life Sci 2014; 112:90-6. [PMID: 25072354 DOI: 10.1016/j.lfs.2014.07.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/27/2014] [Accepted: 07/16/2014] [Indexed: 01/18/2023]
Abstract
AIMS Clinical complaints on the first-line of cardiovascular medications make continuous search for new drugs a necessity. This study evaluated the cardiovascular effects and mechanism of 4-[(1-phenyl-1H-pyrazol-4-yl)methyl]1-piperazine carboxylic acid ethyl ester (LQFM008). MAIN METHODS Normotensive male Wistar or spontaneously hypertensive rats (anesthetized or conscious) were used to evaluate the effect of LQFM008 on the mean arterial pressure (MAP), heart rate (HR), arterial blood flow (ABF), arterial vascular conductance (AVC), baroreflex effectiveness index (BI), systolic blood pressure (SBP), diastolic blood pressure (DBP) and vascular function. KEY FINDINGS In anesthetized normotensive rats, LQFM008 (7.3, 14.3 or 28.6 μmol/kg, i.v.) reduced MAP (-21.1±2.7; -23.9±4.7 or -32.4±8.3 mmHg, respectively) and AVC (22%, 32% or 38%) in a dose-dependent manner. LQFM008 elicited a temporal reduction in the SBP and DBP without changes to the BI of conscious normotensive rats. In hypertensive rats, LQFM008 (7.3, 14.3 or 28.6 μmol/kg, i.v.) reduced MAP (-2.3±2.6; -29.3±2.7 or -38.4±2.8 mmHg, respectively) and increased HR (1.6±3.7; 15.4±4.9 or 25.5±6.2 bmp, respectively) in a dose-dependent manner. A week of oral administration of LQFM008 47.7 μmol/kg elicited a temporal reduction in SBP of hypertensive rats. Pretreatments with atropine, WAY-100635 or L-NAME blocked the effect of LQFM008. In addition, LQFM008-induced endothelium-dependent vascular relaxation was inhibited by L-NAME. SIGNIFICANCE Our findings showed hypotensive, antihypertensive and vasorelaxant effects of LQFM008 and suggest the participation of nitric oxide, 5-HT1A and muscarinic receptors.
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Affiliation(s)
| | - Nathalia Oda Amaral
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Elaine Fernanda da Silva
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Pablinny Morreira Galdino
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Thiago Sardinha de Oliveira
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Paulo César Ghedini
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Jordan K Zjawiony
- Department of Pharmacognosy and National Center for Natural Product Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677-1848, USA
| | - Elson Alves Costa
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Gustavo Rodrigues Pedrino
- Department of Physiological Sciences, Federal University of Goiás, Campus Samambaia, 74001-970 Goiâania, GO, Brazil
| | - Ricardo Menegatti
- Pharmacy Faculty, Federal University of Goiás, Setor Universitário, 74000-000, Goiânia, GO, Brazil
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Mechanism of sympathetic activation and blood pressure elevation in humans and animals following acute intermittent hypoxia. PROGRESS IN BRAIN RESEARCH 2014; 209:131-46. [PMID: 24746046 DOI: 10.1016/b978-0-444-63274-6.00007-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Sleep apnea is associated with repeated episodes of hypoxemia, causing marked increase in sympathetic nerve activity and blood pressure. Considerable evidence suggests that intermittent hypoxia (IH) resulting from apnea is the primary stimulus for sympathetic overactivity in sleep apnea patients. Several IH protocols have been developed either in animals or in humans to investigate mechanisms underlying the altered autonomic regulation of the circulation. Most of these protocols involve several days (10-40 days) of IH exposure, that is, chronic intermittent hypoxia (CIH). Recent data suggest that a single session of IH exposure, that is, acute intermittent hypoxia (AIH), is already capable of increasing tonic sympathetic nerve output (sympathetic long-term facilitation, LTF) and altering chemo- and baroreflexes with or without elevation of blood pressure. This indicates that IH alters the autonomic neurocirculatory at a very early time point, although the mechanisms underlying this neuroplasticity have not been explored in detail. The purpose of this chapter is to briefly review the effects of AIH on sympathetic LTF and alteration of autonomic reflexes in comparison with the studies from CIH studies. We will also discuss the potential central and peripheral mechanism underlying sympathetic LTF.
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Chien CL, Lin MS, Lai HL, Wu YS, Chang CP, Chen HM, Chang C, Su CK, Chern Y. Lack of type VI adenylyl cyclase (AC6) leads to abnormal sympathetic tone in neonatal mice. Exp Neurol 2013; 248:10-5. [DOI: 10.1016/j.expneurol.2013.05.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 05/17/2013] [Accepted: 05/20/2013] [Indexed: 02/07/2023]
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Egwuenu EJ, Fong AY, Pilowsky PM. Intrathecal melanin-concentrating hormone reduces sympathetic tone and blocks cardiovascular reflexes. Am J Physiol Regul Integr Comp Physiol 2012; 303:R624-32. [DOI: 10.1152/ajpregu.00215.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Melanin-concentrating hormone (MCH) is a neuropeptide that acts to increase feeding behavior and decrease energy expenditure. The role of MCH in central cardiorespiratory regulation is still poorly understood. Experiments were conducted on urethane-anesthetized, vagotomized, and artificially ventilated male Sprague-Dawley rats ( n = 22) to ascertain whether MCH modulates sympathetic vasomotor tone, as well as barosympathetic, chemosympathetic, and somatosympathetic reflexes at the level of the spinal cord. Intrathecal injection of 10 μl of MCH produced a dose-dependent hypotension, bradycardia, and sympathoinhibition. Peak response was observed following administration of 1 mM MCH, causing a decrease in mean arterial pressure of 39 ± 2 mmHg ( P < 0.001), splanchnic sympathetic nerve activity of 78 ± 11% ( P < 0.001), and heart rate of 87 ± 11 beats per minute (bpm) ( P < 0.01). The two peaks of the somatosympathetic reflex were decreased by intrathecal MCH, 7 ± 3% ( P < 0.01) and 31 ± 6% ( P < 0.01), respectively, and the spinal component of the reflex was accentuated 96 ± 23% ( P < 0.05), with respect to the baseline for MCH, compared with the two peaks and spinal component of the somatosympathetic reflex elicited following saline injection with respect to the baseline for saline. MCH decreased the sympathetic gain to 120 s of hyperoxic hypercapnea (10% CO2 in 90% O2) and to 10–12 s poikilocapneic anoxia (100% N2) from 0.74 ± 0.14%/s to 0.23 ± 0.04%/s ( P < 0.05) and 16.47 ± 3.2% to 4.35 ± 1.56% ( P < 0.05), respectively. There was a 34% decrease in gain and a 62% decrease in range of the sympathetic baroreflex with intrathecal MCH. These data demonstrate that spinal MCH blunts the central regulation of sympathetic tone and adaptive sympathetic reflexes.
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Shahid IZ, Rahman AA, Pilowsky PM. Orexin A in rat rostral ventrolateral medulla is pressor, sympatho-excitatory, increases barosensitivity and attenuates the somato-sympathetic reflex. Br J Pharmacol 2012; 165:2292-303. [PMID: 21951179 DOI: 10.1111/j.1476-5381.2011.01694.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND AND PURPOSE The rostral ventrolateral medulla (RVLM) maintains sympathetic nerve activity (SNA), and integrates adaptive reflexes. Orexin A-immunoreactive neurones in the lateral hypothalamus project to the RVLM. Microinjection of orexin A into RVLM increases blood pressure and heart rate. However, the expression of orexin receptors, and effects of orexin A in the RVLM on splanchnic SNA (sSNA), respiration and adaptive reflexes are unknown. EXPERIMENTAL APPROACH The effect of orexin A on baseline cardio-respiratory variables as well as the somato-sympathetic, baroreceptor and chemoreceptor reflexes in RVLM were investigated in urethane-anaesthetized, vagotomized and artificially ventilated male Sprague-Dawley rats (n= 50). orexin A and its receptors were detected with fluorescence immunohistochemistry. KEY RESULTS Tyrosine hydroxylase-immunoreactive neurones in the RVLM were frequently co-localized with orexin 1 (OX(1) ) and orexin 2 (OX(2) ) receptors and closely apposed to orexin A-immunoreactive terminals. Orexin A injected into the RVLM was pressor and sympatho-excitatory. Peak effects were observed at 50 pmol with increased mean arterial pressure (42 mmHg) and SNA (45%). Responses to orexin A (50 pmol) were attenuated by the OX(1) receptor antagonist, SB334867, and reproduced by the OX(2) receptor agonist, [Ala(11) , D-Leu(15) ]orexin B. Orexin A attenuated the somato-sympathetic reflex but increased baroreflex sensitivity. Orexin A increased or reduced sympatho-excitation following hypoxia or hypercapnia respectively. CONCLUSIONS AND IMPLICATIONS Although central cardio-respiratory control mechanisms at rest do not rely on orexin, responses to adaptive stimuli are dramatically affected by the functional state of orexin receptors.
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Affiliation(s)
- Israt Z Shahid
- Australian School of Advanced Medicine, Macquarie University, Sydney, Australia
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Gaede AH, Pilowsky PM. Catestatin in rat RVLM is sympathoexcitatory, increases barosensitivity, and attenuates chemosensitivity and the somatosympathetic reflex. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1538-45. [PMID: 20926765 DOI: 10.1152/ajpregu.00335.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The fundamental role and corollary effects of neuropeptides that govern cardiorespiratory control in the brain stem are poorly understood. One such regulatory peptide, catestatin [Cts, human chromogranin A-(352-372)], noncompetitively inhibits nicotinic-cholinergic-stimulated catecholamine release. Previously, we demonstrated the presence of chromogranin A mRNA in brain stem neurons that are important for the maintenance of arterial pressure. In the present study, using immunofluorescence histochemistry, we show that Cts immunoreactivity is colocalized with tyrosine hydroxylase in C1 neurons of the rostral ventrolateral medulla (RVLM, n = 3). Furthermore, we investigated the effects of Cts on resting blood pressure, splanchnic sympathetic nerve activity, phrenic nerve activity, heart rate, and adaptive reflexes. Cts (1 mM in 50 nl or 100 μM in 50-100 nl) was microinjected into the RVLM in urethane-anesthetized, vagotomized, ventilated Sprague-Dawley rats (n = 19). Cardiovascular responses to stimulation of carotid baroreceptors, peripheral chemoreceptors, and the sciatic nerve (somatosympathetic reflex) were analyzed. Cts (1 mM in 50 nl) increased resting arterial pressure (28 ± 3 mmHg at 2 min postinjection), sympathetic nerve activity (15 ± 3% at 2 min postinjection), and phrenic discharge amplitude (31 ± 4% at 10 min postinjection). Cts increased sympathetic barosensitivity 40% (slope increased from -0.05 ± 0.01 before Cts to -0.07 ± 0.01 after Cts) and attenuated the somatosympathetic reflex [1st peak: 36% (from 132 ± 32.1 to 84.0 ± 17.0 μV); 2nd peak: 44% (from 65.1 ± 21.4 to 36.6 ± 14.1 μV)] and chemoreflex (blood pressure response to anoxia decreased 55%, sympathetic response decreased 46%). The results suggest that Cts activates sympathoexcitatory bulbospinal neurons in the RVLM and plays an important regulatory role in adaptive reflexes.
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Affiliation(s)
- Andrea H Gaede
- Australian School of Advanced Medicine, Macquarie Univ., NSW 2109, Australia
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Moazzami A, Tjen-A-Looi SC, Guo ZL, Longhurst JC. Serotonergic projection from nucleus raphe pallidus to rostral ventrolateral medulla modulates cardiovascular reflex responses during acupuncture. J Appl Physiol (1985) 2010; 108:1336-46. [PMID: 20133441 PMCID: PMC2867542 DOI: 10.1152/japplphysiol.00477.2009] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 02/03/2010] [Indexed: 11/22/2022] Open
Abstract
We have demonstrated that stimulation of somatic afferents during electroacupuncture (EA) inhibits sympathoexcitatory cardiovascular rostral ventrolateral medulla (rVLM) neurons and reflex responses. Furthermore, EA at P5-P6 acupoints over the median nerve on the forelimb activate serotonin (5-HT)-containing neurons in the nucleus raphe pallidus (NRP). The present study, therefore, examined the role of the NRP and its synaptic input to neurons in the rVLM during the modulatory influence of EA. Since serotonergic neurons in the NRP project to the rVLM, we hypothesized that the NRP facilitates EA inhibition of the cardiovascular sympathoexcitatory reflex response through activation of 5-HT1A receptors in the rVLM. Animals were anesthetized and ventilated, and heart rate and blood pressure were monitored. We then inserted microinjection and recording electrodes in the rVLM and NRP. Application of bradykinin (10 microg/ml) on the gallbladder every 10 min induced consistent excitatory cardiovascular reflex responses. Stimulation with EA at P5-P6 acupoints reduced the increase in blood pressure from 41+/-4 to 22+/-4 mmHg for more than 70 min. Inactivation of NRP with 50 nl of kainic acid (1 mM) reversed the EA-related inhibition of the cardiovascular reflex response. Similarly, blockade of 5-HT1A receptors with the antagonist WAY-100635 (1 mM, 75 nl) microinjected into the rVLM reversed the EA-evoked inhibition. In the absence of EA, NRP microinjection of dl-homocysteic acid (4 nM, 50 nl), to mimic EA, reduced the cardiovascular and rVLM neuronal excitatory reflex response during stimulation of the gallbladder and splanchnic nerve, respectively. Blockade of 5-HT1A receptors in the rVLM reversed the NRP dl-homocysteic acid inhibition of the cardiovascular and neuronal reflex responses. Thus activation of the NRP, through a mechanism involving serotonergic neurons and 5-HT1A receptors in the rVLM during somatic stimulation with EA, attenuates sympathoexcitatory cardiovascular reflexes.
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Affiliation(s)
- Ali Moazzami
- Susan Samueli Center for Integrative Medicine, Department of Medicine, Medical Science 1 C240, School of Medicine, University of California, Irvine, CA 92697-4075, USA
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Pilowsky PM, Lung MSY, Spirovski D, McMullan S. Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters. Philos Trans R Soc Lond B Biol Sci 2009; 364:2537-52. [PMID: 19651655 DOI: 10.1098/rstb.2009.0092] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Central neurons in the brainstem and spinal cord are essential for the maintenance of sympathetic tone, the integration of responses to the activation of reflexes and central commands, and the generation of an appropriate respiratory motor output. Here, we will discuss work that aims to understand the role that metabotropic neurotransmitter systems play in central cardiorespiratory mechanisms. It is well known that blockade of glutamatergic, gamma-aminobutyric acidergic and glycinergic pathways causes major or even complete disruption of cardiorespiratory systems, whereas antagonism of other neurotransmitter systems barely affects circulation or ventilation. Despite the lack of an 'all-or-none' role for metabotropic neurotransmitters, they are nevertheless significant in modulating the effects of central command and peripheral adaptive reflexes. Finally, we propose that a likely explanation for the plethora of neurotransmitters and their receptors on cardiorespiratory neurons is to enable differential regulation of outputs in response to reflex inputs, while at the same time maintaining a tonic level of sympathetic activity that supports those organs that significantly autoregulate their blood supply, such as the heart, brain, retina and kidney. Such an explanation of the data now available enables the generation of many new testable hypotheses.
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Affiliation(s)
- Paul M Pilowsky
- Australian School of Advanced Medicine, Dow-Corning Building, Level 1, 3 Innovation Road, Macquarie University, 2109 NSW, Australia.
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15
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Neuropeptide Y in the rostral ventrolateral medulla blocks somatosympathetic reflexes in anesthetized rats. Auton Neurosci 2008; 142:64-70. [DOI: 10.1016/j.autneu.2008.05.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 05/07/2008] [Accepted: 05/08/2008] [Indexed: 01/21/2023]
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16
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McMullan S, Pathmanandavel K, Pilowsky PM, Goodchild AK. Somatic nerve stimulation evokes qualitatively different somatosympathetic responses in the cervical and splanchnic sympathetic nerves in the rat. Brain Res 2008; 1217:139-47. [DOI: 10.1016/j.brainres.2008.04.034] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 04/15/2008] [Accepted: 04/18/2008] [Indexed: 11/30/2022]
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17
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Hildreth CM, Padley JR, Pilowsky PM, Goodchild AK. Impaired serotonergic regulation of heart rate may underlie reduced baroreflex sensitivity in an animal model of depression. Am J Physiol Heart Circ Physiol 2008; 294:H474-80. [DOI: 10.1152/ajpheart.01009.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Serotonin (5-HT) is crucial to normal reflex vagal modulation of heart rate (HR). Reduced baroreflex sensitivity [spontaneous baroreflex sensitivity (sBRS)] and HR variability (HRV) reflect impaired neural, particularly vagal, control of HR and are independently associated with depression. In conscious, telemetered Flinders-Sensitive Line (FSL) rats, a well-validated animal model of depression, we tested the hypothesis that cardiovascular regulatory abnormalities are present and associated with deficient serotonergic control of reflex cardiovagal function. In FSL rats and control Flinders-Resistant (FRL) and Sprague-Dawley (SD) rat strains, diurnal measurements of HR, arterial pressure (AP), activity, sBRS, and HRV were made. All strains had normal and similar diurnal variations in HR, AP, and activity. In FRL rats, HR was elevated, contributing to the reduced HRV and sBRS in this strain. In FSL rats, sBRS and high-frequency power HRV were reduced during the night, indicating reduced reflex cardiovagal activity. The ratio of low- to high-frequency bands of HRV was increased in FSL rats, suggesting a relative predominance of cardiac sympathetic and/or reflex activity compared with FRL and SD rats. These data show that conscious FSL rats have cardiovascular regulatory abnormalities similar to depressed humans. Acute changes in HR, AP, temperature, and sBRS in response to 8-hydroxy-2-(di- n-propylamino)tetralin, a 5-HT1A, 5-HT1B, and 5-HT7 receptor agonist, were also determined. In FSL rats, despite inducing an exaggerated hypothermic effect, 8-hydroxy-2-(di- n-propylamino)tetralin did not decrease HR and AP or improve sBRS, suggesting impaired serotonergic neural control of cardiovagal activity. These data suggest that impaired serotonergic control of cardiac reflex function could be one mechanism linking reduced sBRS to increased cardiac risk in depression.
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Curran AK, Leiter JC. Baroreceptor-mediated inhibition of respiration after peripheral and central administration of a 5-HT1Areceptor agonist in neonatal piglets. Exp Physiol 2007; 92:757-67. [PMID: 17392335 DOI: 10.1113/expphysiol.2007.037481] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Inhibition of neurones in the ventral medulla accentuates the respiratory inhibition associated with acute blood pressure elevation in piglets. Activation of presynaptic 5-HT(1A) receptors inhibits serotonergic neurones in the ventral medulla and caudal raphé, and we tested the hypothesis that administration of 8-hydroxydipropylaminotetralin (8-OH-DPAT), a 5-HT(1A) agonist, within the rostroventral medulla and caudal raphé would enhance baroreceptor-mediated inhibition of respiratory activity in decerebrate, neonatal piglets. Baroreceptor stimulation was achieved by inflating a balloon in the distal aorta to elevate carotid blood pressure. After two to four control trials of baroreceptor stimulation, each piglet was given either a single intravenous (i.v.) dose of 10 microg kg(-1) 8-OH-DPAT or treated by adding 10 or 30 mm 8-OH-DPAT to the dialysate for approximately 10 min to inhibit serotonergic neurones, after which the baroreceptor stimulation trials were repeated. Baroreceptor stimulation reduced respiratory activity, particularly the respiratory frequency, which diminished from 35.7 +/- 3.3 to 33.8 +/- 3.1 breaths min(-1) (P < 0.02) and, following i.v. 8-OH-DPAT, baroreceptor-mediated inhibition of respiratory output was significantly accentuated (P < 0.05); the respiratory frequency declined from 34.5 +/- 3.6 to 26.5 +/- 2.9 breaths min(-1). Increasing aortic blood pressure reduced the respiratory frequency (P < 0.01), but focal dialysis of 10 or 30 mm 8-OH-DPAT had, on average, no effect on the ventilatory inhibition associated with an acute elevation of blood pressure. We conclude that activation of 5-HT(1A) receptors after systemic administration of 8-OH-DPAT enhanced baroreflex-mediated inhibition of ventilation, but this effect cannot be attributed to 5-HT(1A) receptor activation within the rostroventral medulla and caudal raphé.
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Affiliation(s)
- Aidan K Curran
- Department of Physiology, Dartmouth Medical School, Lebanon, NH 03756, USA
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19
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Osei-Owusu P, Scrogin K. Role of the arterial baroreflex in 5-HT1A receptor agonist-mediated sympathoexcitation following hypotensive hemorrhage. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1337-44. [PMID: 16397093 DOI: 10.1152/ajpregu.00671.2005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
5-HT1A-receptor agonists rapidly restore blood pressure and sympathetic activity in conscious rats subjected to hypotensive hemorrhage. 5-HT1A-receptor activation has also been shown to produce a robust increase in baroreceptor-dependent, pulse-synchronous firing of cardiac sympathetic nerves in anesthetized cats. To determine whether 5-HT1A-receptor agonists reverse hemorrhage-induced suppression of sympathetic activity through facilitation of the arterial baroreflex, the effects of the 5-HT1A-receptor agonist, 8-OH-DPAT, were assessed in male Sprague-Dawley rats subjected to sinoaortic baroreceptor denervation and subsequent hypotensive hemorrhage. 8-OH-DPAT produced rapid pressor and sympathoexcitatory responses in hemorrhaged animals that were attenuated, but not blocked, by sinoaortic denervation (SAD) (+49 +/- 4 vs. +37 +/- 4 mmHg; +165 +/- 30 vs. +92 +/- 24% baseline, P < 0.01). Spectral analysis of sympathetic activity showed that SAD abolished the 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT)-mediated increases in pulse-synchronous (13 +/- 1 vs. 5 +/- 1% total power for intact vs. SAD rats, P < 0.01) and Mayer wave-related bursting (18 +/- 3 vs. 8 +/- 1% total power, P < 0.05). However, 8-OH-DPAT continued to increase total power (+72 +/- 22 vs. -63 +/- 7% prehemorrhage total power, P < 0.05) and power at the respiratory frequency (35 +/- 2 vs. 25 +/- 4% total power) in SAD animals. These data indicate that full expression of the sympathoexcitatory effect of 8-OH-DPAT requires a functional arterial baroreflex. However, a portion of the effect is due to activation of arterial baroreflex-independent sympathetic pathways.
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Affiliation(s)
- Patrick Osei-Owusu
- Dept. of Pharmacology and Experimental Therapeutics, Loyola Univ. Chicago, Stritch School of Medicine, 2160 First Ave., Maywood, IL 60153, USA
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Padley JR, Overstreet DH, Pilowsky PM, Goodchild AK. Impaired cardiac and sympathetic autonomic control in rats differing in acetylcholine receptor sensitivity. Am J Physiol Heart Circ Physiol 2005; 289:H1985-92. [PMID: 15951345 DOI: 10.1152/ajpheart.00430.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acetylcholine receptors (AChR) are important in premotor and efferent control of autonomic function; however, the extent to which cardiovascular function is affected by genetic variations in AChR sensitivity is unknown. We assessed heart rate variability (HRV) and baroreflex sensitivity (BRS) in rats bred for resistance (FRL) or sensitivity (FSL) to cholinergic agents compared with Sprague-Dawley rats (SD), confirmed by using hypothermic responses evoked by the muscarinic agonist oxotremorine (0.2 mg/kg ip) ( n ≥ 9 rats/group). Arterial pressure, ECG, and splanchnic sympathetic (SNA) and phrenic (PNA) nerve activities were acquired under anesthesia (urethane 1.3 g/kg ip). HRV was assessed in time and frequency domains from short-term R-R interval data, and spontaneous heart rate BRS was obtained by using a sequence method at rest and after administration of atropine methylnitrate (mATR, 2 mg/kg iv). Heart rate and SNA baroreflex gains were assessed by using conventional pharmacological methods. FRL and FSL were normotensive but displayed elevated heart rates, reduced HRV and HF power, and spontaneous BRS compared with SD. mATR had no effect on these parameters in FRL or FSL, indicating reduced cardiovagal tone. FSL exhibited reduced PNA frequency, longer baroreflex latency, and reduced baroreflex gain of heart rate and SNA compared with FRL and SD, indicating in FSL dual impairment of cardiac and circulatory baroreflexes. These findings show that AChR resistance results in reduced cardiac muscarinic receptor function leading to cardiovagal insufficiency. In contrast, AChR sensitivity results in autonomic and respiratory abnormalities arising from alterations in central muscarinic and or other neurotransmitter receptors.
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Affiliation(s)
- James R Padley
- Hypertension and Stroke Research Laboratories, Dept. of Physiology, University of Sydney, NSW Australia
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21
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Pollard H. Reflections on the "type O" disorder. J Manipulative Physiol Ther 2005; 28:547. [PMID: 16182031 DOI: 10.1016/j.jmpt.2005.07.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Revised: 06/06/2004] [Indexed: 02/01/2023]
Affiliation(s)
- Henry Pollard
- The ONE Research Foundation, 144 West D St, Encinitas, CA 92024, USA.
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Makeham JM, Goodchild AK, Pilowsky PM. NK1 receptor activation in rat rostral ventrolateral medulla selectively attenuates somato-sympathetic reflex while antagonism attenuates sympathetic chemoreflex. Am J Physiol Regul Integr Comp Physiol 2005; 288:R1707-15. [PMID: 15731401 DOI: 10.1152/ajpregu.00537.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of activation and blockade of the neurokinin 1 (NK1) receptor in the rostral ventrolateral medulla (RVLM) on arterial blood pressure (ABP), splanchnic sympathetic nerve activity (sSNA), phrenic nerve activity, the somato-sympathetic reflex, baroreflex, and chemoreflex were studied in urethane-anesthetized and artificially ventilated Sprague-Dawley rats. Bilateral microinjection of either the stable substance P analog (pGlu5, MePhe8, Sar9)SP(5–11) (DiMe-SP) or the highly selective NK1 agonist [Sar9, Met (O2)11]SP into the RVLM resulted in an increase in ABP, sSNA, and heart rate and an abolition of phrenic nerve activity. The effects of [Sar9, Met (O2)11]SP were blocked by the selective nonpeptide NK1 receptor antagonist WIN 51708. NK1 receptor activation also dramatically attenuated the somato-sympathetic reflex elicited by tibial nerve stimulation, while leaving the baroreflex and chemoreflex unaffected. This effect was again blocked by WIN 51708. NK1 receptor antagonism in the RVLM, with WIN 51708 significantly attenuated the sympathoexcitatory response to hypoxia but had no effect on baseline respiratory function. Our findings suggest that substance P and the NK1 receptor play a significant role in the cardiorespiratory reflexes integrated within the RVLM.
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Affiliation(s)
- John M Makeham
- Hypertension and Stroke Research Laboratory, Department of Physiology, University of Sydney, New South Wales, Australia
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23
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Verner TA, Goodchild AK, Pilowsky PM. A mapping study of cardiorespiratory responses to chemical stimulation of the midline medulla oblongata in ventilated and freely breathing rats. Am J Physiol Regul Integr Comp Physiol 2004; 287:R411-21. [PMID: 15031133 DOI: 10.1152/ajpregu.00019.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to examine the cardiorespiratory effects of chemically stimulating neurons in the midline medulla oblongata (MM) of artificially ventilated and freely breathing anesthetized rats. Earlier studies reported that stimulation of the MM elicits increases or decreases in mean arterial pressure (MAP) and phrenic nerve activity, depending on the mode and site of stimulation, anesthetic, and species. In the first series of experiments, rats were anesthetized with urethane, artificially ventilated, paralyzed, and bilaterally vagotomized. The rostrocaudal extent of the MM was mapped by microinjections of DL-homocysteic acid or L-glutamate (both 100 mM, 100 nl), and, in line with previous studies, most injections produced only small responses in MAP, heart rate, and splanchnic sympathetic nerve activity. Increases in respiratory parameters were evoked in caudal regions. However, activation of a discrete region of the MM at the level of the caudal pole of the facial nucleus (CP7) consistently caused a dramatic reduction in phrenic nerve amplitude and/or frequency and, in six rats, produced a prolonged apnea. The second series of experiments was carried out on freely breathing pentobarbitone sodium-anesthetized rats, with a diaphragmatic electromyogram used to monitor respiratory activity. Respiratory activity could again be abolished at CP7 after microinjections of glutamate (100 mM, 50 nl); however, these responses were accompanied by large decreases in MAP and moderate reductions in heart rate. This depression of respiratory activity may be due to activation of propriobulbar inhibitory neurons that project to known respiratory centers in the brain stem.
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Affiliation(s)
- Todd A Verner
- Hypertension and Stroke Research Laboratories, Department of Physiology, University of Sydney, Royal North Shore Hospital, St. Leonards NSW 2065, Australia
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Scrogin KE. 5-HT1A receptor agonist 8-OH-DPAT acts in the hindbrain to reverse the sympatholytic response to severe hemorrhage. Am J Physiol Regul Integr Comp Physiol 2003; 284:R782-91. [PMID: 12611395 DOI: 10.1152/ajpregu.00478.2002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Central administration of serotonergic 5-HT1A receptor agonists delays the reflex sympatholytic response to severe hemorrhage in conscious rats. To determine the region where 5-HT1A receptor agonists act to mediate this response, recovery of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) was compared in hemorrhaged rats after injection of the selective 5-HT1A agonist, (+)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), in various regions of the cerebroventricular system or the systemic circulation. Three minutes after injection of 8-OH-DPAT (48 nmol/kg), MAP and RSNA were higher in hemorrhaged rats given drug in the fourth ventricle (94 +/- 5 mmHg, 82 +/- 18% of baseline) or the systemic circulation (90 +/- 4 mmHg, 113 +/- 15% of baseline) than in rats given drug in the Aqueduct of Sylvius (63 +/- 4 mmHg, 27 +/- 11% of baseline), the lateral ventricle (42 +/- 3 mmHg, -8 +/- 18% of baseline), or in rats given saline in various brain regions (47 +/- 5 mmHg, -42 +/- 10% of baseline). A lower-dose injection of 8-OH-DPAT (10 nmol/kg) also accelerated the recovery of MAP and RSNA in hemorrhaged rats when given in the fourth ventricle (94 +/- 26 mmHg, 72 +/- 33% of baseline 3 min after injection) but not the systemic circulation (46 +/- 4 mmHg, -25 +/- 30% of baseline). These data indicate that 8-OH-DPAT acts on receptors in the hindbrain to reverse the sympatholytic response to hemorrhage in conscious rats.
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Affiliation(s)
- Karie E Scrogin
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60513, USA.
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Abstract
The central nervous system plays a critical role in the management of blood flow to the tissues and its return to the heart and lungs. This is achieved by a complex interplay of neural efferent pathways, humoral mechanisms and afferent pathways. In this review, we focus on recent progress (within the past 10 years) that has been made in the sympathetic control of arterial blood pressure with a special emphasis on the role of baroreceptor mechanisms and central neurotransmitters. In particular, we focus on new features since 1991, such as neurotransmission in the nucleus tractus solitarius, the role of neurons in the most caudal part of the ventrolateral medulla oblongata and the increasing understanding of the exquisite control of different sympathetic pathways by different neurotransmitter systems.
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Affiliation(s)
- Paul M Pilowsky
- Department of Physiology, University of Sydney, Royal North Shore Hospital, Sydney, Australia.
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Affiliation(s)
- Harald M Stauss
- Johannes-Müller-Institut für Physiologie, Humboldt-Universität zu Berlin (Charité), 10117 Berlin, Germany
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Dean C, Bago M. Renal sympathoinhibition mediated by 5-HT(1A) receptors in the RVLM during severe hemorrhage in rats. Am J Physiol Regul Integr Comp Physiol 2002; 282:R122-30. [PMID: 11742830 DOI: 10.1152/ajpregu.2002.282.1.r122] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of 5-hydroxytryptamine type 1A (5-HT(1A)) receptors in the rostral ventrolateral medulla (RVLM) in the mediation of the sympathoinhibitory and hypotensive responses to severe hemorrhage was examined in pentobarbital sodium-anesthetized rats. The control response to hemorrhage (1 ml/min to 50 mmHg) consisted of a fall in arterial blood pressure and an initial baroreflex increase in renal sympathetic nerve activity followed after 2 min by a rapid decline in blood pressure accompanied by a decrease in renal sympathetic nerve activity. In response to hemorrhage in animals in which the specific 5-HT(1A) receptor antagonist WAY-100635 was microinjected into the pressor area of the RVLM, the fall in blood pressure was delayed and attenuated while renal sympathetic nerve activity was increased and maintained above baseline. In barodenervated animals with blockade of RVLM 5-HT(1A) receptors, there was no change in renal sympathetic nerve activity in response to hemorrhage. These data suggest that renal sympathoinhibition elicited in response to severe hemorrhage is mediated by 5-HT(1A) receptors in the RVLM.
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Affiliation(s)
- C Dean
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53295, USA.
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