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Baumer-Harrison C, Patel S, Scott KA, Krause EG, de Kloet AD. Optical perturbation of Agtr1a-containing neurons and afferents within the caudal nucleus of the solitary tract modulates sodium intake. Physiol Behav 2024; 284:114624. [PMID: 38959991 DOI: 10.1016/j.physbeh.2024.114624] [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: 02/07/2024] [Revised: 06/30/2024] [Accepted: 06/30/2024] [Indexed: 07/05/2024]
Abstract
Angiotensin-II (Ang-II) production is driven by deviations in blood volume and osmolality, and serves the role of regulating blood pressure and fluid intake to maintain cardiovascular and hydromineral homeostasis. These actions are mediated by Ang-II acting on its type 1a receptor (AT1aR) within the central nervous system and periphery. Of relevance, AT1aR are expressed on sensory afferents responsible for conveying cardiovascular information to the nucleus of the solitary tract (NTS). We have previously determined that optical excitation of neurons and vagal afferents within the NTS that express AT1aR (referred to as NTSAT1aR) mimics the perception of increased vascular stretch and induces compensatory responses to restore blood pressure. Here, we test whether NTSAT1aR are also involved in the modulation of water and sodium intake. We directed the light-sensitive excitatory channelrhodopsin-2 (ChR2) or inhibitory halorhodopsin (Halo) to Agtr1a-containing neurons and measured water and sodium chloride (NaCl) intake in the presence and absence of optical stimulation within the NTS during various challenges to fluid homeostasis. Optical perturbation of NTSAT1aR modulates NaCl intake, such that excitation attenuates, whereas inhibition increases intake. This effect is only observed in the water-deprived condition, suggesting that NTSAT1aR are involved in the regulation of sodium intake during an imbalance in both the intracellular and extracellular fluid compartments. Furthermore, optical excitation of NTSAT1aR increases c-Fos expression within oxytocinergic neurons of the paraventricular nucleus of the hypothalamus (PVN), indicating that the regulation of sodium intake by NTSAT1aR may be mediated by oxytocin. Collectively, these results reveal that NTSAT1aR are sufficient and necessary to modulate sodium intake relative to perceived changes in vascular stretch.
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Affiliation(s)
- Caitlin Baumer-Harrison
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL, 32611, United States; Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL, 32611, United States; Center for Smell and Taste, University of Florida, Gainesville, FL, 32611, United States; Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, United States.
| | - Sagar Patel
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL, 32611, United States
| | - Karen A Scott
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL, 32611, United States; Department of Pharmacodynamics, College of Pharmacy, University of Florida, 32611, United States; Neuroscience Institute, Georgia State University, Atlanta, GA, 30302, United States
| | - Eric G Krause
- Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL, 32611, United States; Department of Pharmacodynamics, College of Pharmacy, University of Florida, 32611, United States; Neuroscience Institute, Georgia State University, Atlanta, GA, 30302, United States
| | - Annette D de Kloet
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL, 32611, United States; Center for Integrative Cardiovascular and Metabolic Diseases, University of Florida, Gainesville, FL, 32611, United States; Center for Smell and Taste, University of Florida, Gainesville, FL, 32611, United States; Neuroscience Institute, Georgia State University, Atlanta, GA, 30302, United States
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Wang J, Lv F, Yin W, Gao Z, Liu H, Wang Z, Sun J. The organum vasculosum of the lamina terminalis and subfornical organ: regulation of thirst. Front Neurosci 2023; 17:1223836. [PMID: 37732311 PMCID: PMC10507174 DOI: 10.3389/fnins.2023.1223836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 08/22/2023] [Indexed: 09/22/2023] Open
Abstract
Thirst and water intake are regulated by the organum vasculosum of the lamina terminalis (OVLT) and subfornical organ (SFO), located around the anteroventral third ventricle, which plays a critical role in sensing dynamic changes in sodium and water balance in body fluids. Meanwhile, neural circuits involved in thirst regulation and intracellular mechanisms underlying the osmosensitive function of OVLT and SFO are reviewed. Having specific Nax channels in the glial cells and other channels (such as TRPV1 and TRPV4), the OVLT and SFO detect the increased Na+ concentration or hyperosmolality to orchestrate osmotic stimuli to the insular and cingulate cortex to evoke thirst. Meanwhile, the osmotic stimuli are relayed to the supraoptic nucleus (SON) and paraventricular nucleus of the hypothalamus (PVN) via direct neural projections or the median preoptic nucleus (MnPO) to promote the secretion of vasopressin which plays a vital role in the regulation of body fluid homeostasis. Importantly, the vital role of OVLT in sleep-arousal regulation is discussed, where vasopressin is proposed as the mediator in the regulation when OVLT senses osmotic stimuli.
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Affiliation(s)
- Jiaxu Wang
- Department of Anatomy and Neurobiology, School of Medicine, Shandong University, Jinan, Shandong, China
| | - Fenglin Lv
- Department of Anatomy and Neurobiology, School of Medicine, Shandong University, Jinan, Shandong, China
| | - Wei Yin
- Department of Anatomy and Neurobiology, School of Medicine, Shandong University, Jinan, Shandong, China
| | - Zhanpeng Gao
- Department of Anatomy and Neurobiology, School of Medicine, Shandong University, Jinan, Shandong, China
| | - Hongyu Liu
- Institute of Sport and Exercise Medicine, North University of China, Taiyuan, China
| | - Zhen Wang
- Department of Cardiology, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jinhao Sun
- Department of Anatomy and Neurobiology, School of Medicine, Shandong University, Jinan, Shandong, China
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3
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Dampney RA, Michelini LC, Li DP, Pan HL. Regulation of sympathetic vasomotor activity by the hypothalamic paraventricular nucleus in normotensive and hypertensive states. Am J Physiol Heart Circ Physiol 2018; 315:H1200-H1214. [PMID: 30095973 PMCID: PMC6297824 DOI: 10.1152/ajpheart.00216.2018] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 07/13/2018] [Accepted: 07/25/2018] [Indexed: 12/22/2022]
Abstract
The hypothalamic paraventricular nucleus (PVN) is a unique and important brain region involved in the control of cardiovascular, neuroendocrine, and other physiological functions pertinent to homeostasis. The PVN is a major source of excitatory drive to the spinal sympathetic outflow via both direct and indirect projections. In this review, we discuss the role of the PVN in the regulation of sympathetic output in normal physiological conditions and in hypertension. In normal healthy animals, the PVN presympathetic neurons do not appear to have a major role in sustaining resting sympathetic vasomotor activity or in regulating sympathetic responses to short-term homeostatic challenges such as acute hypotension or hypoxia. Their role is, however, much more significant during longer-term challenges, such as sustained water deprivation, chronic intermittent hypoxia, and pregnancy. The PVN also appears to have a major role in generating the increased sympathetic vasomotor activity that is characteristic of multiple forms of hypertension. Recent studies in the spontaneously hypertensive rat model have shown that impaired inhibitory and enhanced excitatory synaptic inputs to PVN presympathetic neurons are the basis for the heightened sympathetic outflow in hypertension. We discuss the molecular mechanisms underlying the presynaptic and postsynaptic alterations in GABAergic and glutamatergic inputs to PVN presympathetic neurons in hypertension. In addition, we discuss the ability of exercise training to correct sympathetic hyperactivity by restoring blood-brain barrier integrity, reducing angiotensin II availability, and decreasing oxidative stress and inflammation in the PVN.
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Affiliation(s)
- Roger A Dampney
- Department of Physiology, University of Sydney , Sydney, New South Wales , Australia
| | - Lisete C Michelini
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo , São Paulo , Brazil
| | - De-Pei Li
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center , Houston, Texas
| | - Hui-Lin Pan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center , Houston, Texas
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4
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Abstract
Water intake is one of the most basic physiological responses and is essential to sustain life. The perception of thirst has a critical role in controlling body fluid homeostasis and if neglected or dysregulated can lead to life-threatening pathologies. Clear evidence suggests that the perception of thirst occurs in higher-order centres, such as the anterior cingulate cortex (ACC) and insular cortex (IC), which receive information from midline thalamic relay nuclei. Multiple brain regions, notably circumventricular organs such as the organum vasculosum lamina terminalis (OVLT) and subfornical organ (SFO), monitor changes in blood osmolality, solute load and hormone circulation and are thought to orchestrate appropriate responses to maintain extracellular fluid near ideal set points by engaging the medial thalamic-ACC/IC network. Thirst has long been thought of as a negative homeostatic feedback response to increases in blood solute concentration or decreases in blood volume. However, emerging evidence suggests a clear role for thirst as a feedforward adaptive anticipatory response that precedes physiological challenges. These anticipatory responses are promoted by rises in core body temperature, food intake (prandial) and signals from the circadian clock. Feedforward signals are also important mediators of satiety, inhibiting thirst well before the physiological state is restored by fluid ingestion. In this Review, we discuss the importance of thirst for body fluid balance and outline our current understanding of the neural mechanisms that underlie the various types of homeostatic and anticipatory thirst.
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Affiliation(s)
- Claire Gizowski
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre and Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G1A4, Canada
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5
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Abstract
Osmosensory neurons are specialized cells activated by increases in blood osmolality to trigger thirst, secretion of the antidiuretic hormone vasopressin, and elevated sympathetic tone during dehydration. In addition to multiple extrinsic factors modulating their activity, osmosensory neurons are intrinsically osmosensitive, as they are activated by increased osmolality in the absence of neighboring cells or synaptic contacts. This intrinsic osmosensitivity is a mechanical process associated with osmolality-induced changes in cell volume. This review summarises recent findings revealing molecular mechanisms underlying the mechanical activation of osmosensory neurons and highlighting important roles of microtubules, actin, and mechanosensitive ion channels in this process.
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Rahmouni K. Cardiovascular Regulation by the Arcuate Nucleus of the Hypothalamus: Neurocircuitry and Signaling Systems. Hypertension 2016; 67:1064-71. [PMID: 27045026 PMCID: PMC4865428 DOI: 10.1161/hypertensionaha.115.06425] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Kamal Rahmouni
- From the Department of Pharmacology and Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City.
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7
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Margatho L, Porcari C, Macchione A, da Silva Souza G, Caeiro X, Antunes-Rodrigues J, Vivas L, Godino A. Temporal dissociation between sodium depletion and sodium appetite appearance: Involvement of inhibitory and stimulatory signals. Neuroscience 2015; 297:78-88. [DOI: 10.1016/j.neuroscience.2015.03.059] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 03/20/2015] [Accepted: 03/25/2015] [Indexed: 12/23/2022]
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Stachniak TJ, Trudel E, Bourque CW. Cell-specific retrograde signals mediate antiparallel effects of angiotensin II on osmoreceptor afferents to vasopressin and oxytocin neurons. Cell Rep 2014; 8:355-62. [PMID: 25043186 DOI: 10.1016/j.celrep.2014.06.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 05/24/2014] [Accepted: 06/18/2014] [Indexed: 11/16/2022] Open
Abstract
Homeostatic control of extracellular fluid osmolality in rats requires a parallel excitation of vasopressin (VP) and oxytocin (OT) neurosecretory neurons by osmoreceptor afferents to regulate the amount of water and sodium in the urine under normal conditions. However, during decreased blood volume (hypovolemia), natriuresis is suppressed, whereas osmotically driven antidiuresis is enhanced to promote retention of isotonic fluid. Because Angiotensin II (Ang II) is released centrally to indicate hypovolemia, we hypothesized that Ang II can evoke a state-dependent switch in circuit function. Here, we show that Ang II, a neuropeptide released centrally during hypovolemia, suppresses osmoreceptor-mediated synaptic excitation of OT neurons while potentiating excitation of VP neurons. Ang II does this by inducing cell-autonomous release of nitric oxide by VP neurons and endocannabinoids by OT neurons to respectively enhance and reduce glutamate release by osmoreceptor afferents. These findings indicate that peptide modulators such as Ang II can regulate synaptic communication to achieve a state-dependent and target-specific modulation of circuit activity.
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Affiliation(s)
- Tevye J Stachniak
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, QC H3G1A4, Canada; Discovery Neuroscience, F. Hoffman-La Roche AG, Basel 4051, Switzerland
| | - Eric Trudel
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, QC H3G1A4, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Research Institute of the McGill University Health Centre, Montreal, QC H3G1A4, Canada.
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Margatho LO, Elias CF, Elias LLK, Antunes-Rodrigues J. Oxytocin in the central amygdaloid nucleus modulates the neuroendocrine responses induced by hypertonic volume expansion in the rat. J Neuroendocrinol 2013; 25:466-77. [PMID: 23331859 DOI: 10.1111/jne.12021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 12/13/2012] [Accepted: 01/04/2013] [Indexed: 12/01/2022]
Abstract
The present study investigated the involvement of the oxytocinergic neurones that project into the central amygdala (CeA) in the control of electrolyte excretion and hormone secretion in unanaesthetised rats subjected to acute hypertonic blood volume expansion (BVE; 0.3 M NaCl, 2 ml/100 g of body weight over 1 min). Oxytocin and vasopressin mRNA expression in the paraventricular (Pa) and supraoptic nucleus (SON) of the hypothalamus were also determined using the real time-polymerase chain reaction and in situ hybridisation. Male Wistar rats with unilaterally implanted stainless steel cannulas in the CeA were used. Oxytocin (1 μg/0.2 μl), vasotocin, an oxytocin antagonist (1 μg/0.2 μl) or vehicle was injected into the CeA 20 min before the BVE. In rats treated with vehicle in the CeA, hypertonic BVE increased urinary volume, sodium excretion, plasma oxytocin (OT), vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and also increased the expression of OT and AVP mRNA in the Pa and SON. In rats pre-treated with OT in the CeA, previously to the hypertonic BVE, there were further significant increases in plasma AVP, OT and ANP levels, urinary sodium and urine output, as well as in gene expression (AVP and OT mRNA) in the Pa and SON compared to BVE alone. Vasotocin reduced sodium, urine output and ANP levels, although no changes were observed in plasma AVP and OT levels or in the expression of the AVP and OT genes in both hypothalamic nuclei. The results of the present study suggest that oxytocin in the CeA exerts a facilitatory role in the maintenance of hydroelectrolyte balance in response to changes in extracellular volume and osmolality.
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Affiliation(s)
- L O Margatho
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil.
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10
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Miller RL, Knuepfer MM, Wang MH, Denny GO, Gray PA, Loewy AD. Fos-activation of FoxP2 and Lmx1b neurons in the parabrachial nucleus evoked by hypotension and hypertension in conscious rats. Neuroscience 2012; 218:110-25. [PMID: 22641087 PMCID: PMC3405558 DOI: 10.1016/j.neuroscience.2012.05.049] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Revised: 05/17/2012] [Accepted: 05/17/2012] [Indexed: 02/07/2023]
Abstract
The parabrachial nucleus (PB) is a brainstem cell group that receives a strong input from the nucleus tractus solitarius regarding the physiological status of the internal organs and sends efferent projections throughout the forebrain. Since the neuroanatomical organization of the PB remains unclear, our first step was to use specific antibodies against two neural lineage transcription factors: Forkhead box protein2 (FoxP2) and LIM homeodomain transcription factor 1 beta (Lmx1b) to define the PB in adult rats. This allowed us to construct a cytoarchitectonic PB map based on the distribution of neurons that constitutively express these two transcription factors. Second, the in situ hybridization method combined with immunohistochemistry demonstrated that mRNA for glutamate vesicular transporter Vglut2 (Slc17a6) was present in most of the Lmx1b+ and FoxP2+ parabrachial neurons, indicating these neurons use glutamate as a transmitter. Third, conscious rats were maintained in a hypotensive or hypertensive state for 2h, and then, their brainstems were prepared by the standard c-Fos method which is a measure of neuronal activity. Both hypotension and hypertension resulted in c-Fos activation of Lmx1b+ neurons in the external lateral-outer subdivision of the PB (PBel-outer). Hypotension, but not hypertension, caused c-Fos activity in the FoxP2+ neurons of the central lateral PB (PBcl) subnucleus. The Kölliker-Fuse nucleus as well as the lateral crescent PB and rostral-most part of the PBcl contain neurons that co-express FoxP2+ and Lmx1b+, but none of these were activated after blood pressure changes. Salt-sensitive FoxP2 neurons in the pre-locus coeruleus and PBel-inner were not c-Fos activated following blood pressure changes. In summary, the present study shows that the PBel-outer and PBcl subnuclei originate from two different neural progenitors, contain glutamatergic neurons, and are affected by blood pressure changes, with the PBel-outer reacting to both hypo- and hypertension, and the PBcl signaling only hypotensive changes.
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Affiliation(s)
- Rebecca L. Miller
- Department of Anatomy and Neurobiology, 660 S. Euclid Ave, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Mark M. Knuepfer
- Department of Pharmacological & Physiological Science, St. Louis University School of Medicine, 1402 S. Grand Blvd, St. Louis, MO 63104, USA
| | - Michelle H. Wang
- Department of Anatomy and Neurobiology, 660 S. Euclid Ave, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - George O. Denny
- Department of Anatomy and Neurobiology, 660 S. Euclid Ave, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Paul A. Gray
- Department of Anatomy and Neurobiology, 660 S. Euclid Ave, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Arthur D. Loewy
- Department of Anatomy and Neurobiology, 660 S. Euclid Ave, Washington University School of Medicine, St. Louis, MO 63110, USA
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Sinno MH, Coquerel Q, Boukhettala N, Coëffier M, Gallas S, Terashi M, Ibrahim A, Breuillé D, Déchelotte P, Fetissov SO. Chemotherapy-induced anorexia is accompanied by activation of brain pathways signaling dehydration. Physiol Behav 2010; 101:639-48. [DOI: 10.1016/j.physbeh.2010.09.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 08/17/2010] [Accepted: 09/22/2010] [Indexed: 02/07/2023]
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12
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Ployngam T, Katz SS, Collister JP. Role of the median preoptic nucleus in the chronic hypotensive effect of losartan in sodium-replete normal rats. Clin Exp Pharmacol Physiol 2010; 37:e7-13. [PMID: 19793103 DOI: 10.1111/j.1440-1681.2009.05307.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. We have shown previously that the chronic hypotensive effect of the angiotensin II AT1 receptor antagonist losartan is mediated, in part, by the subfornical organ (SFO). However, the neural pathway(s) mediating this central effect of losartan downstream from the SFO has not been completely elucidated. 2. The present study was designed to test the hypothesis that the median preoptic nucleus (MnPO) is a crucial part of the neural pathway necessary for the chronic hypotensive effect of losartan. To test this hypothesis, male Sprague-Dawley rats were subjected to either Sham or electrolytic lesion of the MnPO (MnPOx). Rats were instrumented with radiotelemetric transducers and aortic flow probes for the continuous measurement of mean arterial pressure (MAP) and heart rate and cardiac output (CO), respectively. Total peripheral resistance (TPR) was calculated as MAP/CO. After 3 days of baseline measurements, rats were infused intraperitoneally with losartan (10 mg/kg per day) via an osmotic minipump at a rate of 5 microL/min. 3. The data revealed that, by Day 9 of losartan treatment, MAP had decreased 34 +/- 2 mmHg in MnPOx rats (n = 9), whereas the MAP of Sham-lesioned rats (n = 8) had only decreased 24 +/- 3 mmHg. These findings were accompanied by a greater decrease in TPR in MnPOx compared with Sham rats (-0.464 vs-0.237 mmHg/mL per min, respectively), whereas CO remained unchanged throughout the study protocol. 4. These results do not support the hypothesis that an intact MnPO is necessary to mediate the full chronic hypotensive effect of losartan in normal rats. Instead, they appear to suggest that the MnPO may play an important role in buffering the profound hypotension induced by losartan.
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Affiliation(s)
- Trasida Ployngam
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN, USA
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Prager-Khoutorsky M, Bourque CW. Osmosensation in vasopressin neurons: changing actin density to optimize function. Trends Neurosci 2009; 33:76-83. [PMID: 19963290 DOI: 10.1016/j.tins.2009.11.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 10/31/2009] [Accepted: 11/13/2009] [Indexed: 11/19/2022]
Abstract
The proportional relation between circulating vasopressin concentration and plasma osmolality is fundamental for body fluid homeostasis. Although changes in the sensitivity of this relation are associated with pathophysiological conditions, central mechanisms modulating osmoregulatory gain are unknown. Here, we review recent data that sheds important light on this process. The cell autonomous osmosensitivity of vasopressin neurons depends on cation channels comprising a variant of the transient receptor potential vanilloid 1 (TRPV1) channel. Hyperosmotic activation is mediated by a mechanical process where sensitivity increases in proportion with actin filament density. Moreover, angiotensin II amplifies osmotic activation by a rapid stimulation of actin polymerization, suggesting that neurotransmitter-induced changes in cytoskeletal organization in osmosensory neurons can mediate central changes in osmoregulatory gain.
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Affiliation(s)
- Masha Prager-Khoutorsky
- Center for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Canada
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14
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Benedetti M, Rorato R, Castro M, Machado BH, Antunes-Rodrigues J, Elias LLK. Water deprivation increases Fos expression in hypothalamic corticotropin-releasing factor neurons induced by right atrial distension in awake rats. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1706-12. [DOI: 10.1152/ajpregu.00022.2008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Atrial mechanoreceptors, sensitive to stretch, contribute in regulating heart rate and intravascular volume. The information from those receptors reaches the nucleus tractus solitarius and then the paraventricular nucleus (PVN), known to have a crucial role in the regulation of cardiovascular function. Neurons in the PVN synthesize CRF, AVP, and oxytocin (OT). Stimulation of atrial mechanoreceptors was performed in awake rats implanted with a balloon at the junction of the superior vena cava and right atrium. Plasma ACTH, AVP, and OT concentrations and Fos, CRF, AVP, and OT immunolabeling in the PVN were determined after balloon inflation in hydrated and water-deprived rats. The distension of the balloon increased the plasma ACTH concentrations, which were higher in water-deprived than in hydrated rats ( P < 0.05). In addition, the distension in the water-deprived group decreased plasma AVP concentrations ( P < 0.05), compared with the respective control group. The distension increased the number of Fos- and double-labeled Fos/CRF neurons in the parvocellular PVN, which was higher in the water-deprived than in the hydrated group ( P < 0.01). There was no difference in the Fos expression in magnocellular PVN neurons after distension in hydrated and water-deprived groups, compared with respective controls. In conclusion, parvocellular CRF neurons showed an increase of Fos expression induced by stimulation of right atrial mechanoreceptors, suggesting that CRF participates in the cardiovascular reflex adjustments elicited by volume loading. Activation of CRF neurons in the PVN by cardiovascular reflex is affected by osmotic stimulation.
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Amplification of transducer gain by angiotensin II-mediated enhancement of cortical actin density in osmosensory neurons. J Neurosci 2008; 28:9536-44. [PMID: 18799685 DOI: 10.1523/jneurosci.1495-08.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Osmosensory neurons transduce osmotic signals into a neural spike code that commands behavioral and endocrine responses that mediate body fluid homeostasis. Although changes in osmoregulatory reflex gain are known to occur under physiological and pathological conditions, the basis for this modulation is unknown. Here, we show that angiotensin II amplifies osmosensory transduction by enhancing the proportional relationship between osmolality, receptor potential, and action potential firing in rat supraoptic nucleus neurons. This effect is mediated by a phospholipase C- and protein kinase C-dependent increase in cellular mechanosensitivity that is associated with a rapid increase in cortical actin filament density. Preventing this increase with cytochalasin D eliminated the enhancement of mechanosensitivity, whereas enhancing actin filament density with jasplakinolide potentiated mechanosensitivity and occluded the effects of angiotensin II. These results indicate that a receptor-mediated increase in cortical actin density can enhance osmosensitivity in acutely isolated supraoptic neurons.
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Gaykema RPA, Park SM, McKibbin CR, Goehler LE. Lipopolysaccharide suppresses activation of the tuberomammillary histaminergic system concomitant with behavior: a novel target of immune-sensory pathways. Neuroscience 2008; 152:273-87. [PMID: 18082968 DOI: 10.1016/j.neuroscience.2007.10.042] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Revised: 10/25/2007] [Accepted: 10/26/2007] [Indexed: 11/18/2022]
Abstract
Infection and inflammation strongly inhibit a variety of behaviors, including exploration, social interaction, and food intake. The mechanisms that underlie sickness behavior remain elusive, but appear to involve fatigue and a state of hypo-arousal. Because histaminergic neurons in the ventral tuberomammillary nucleus of the hypothalamus (VTM) play a crucial role in the mediation of alertness and behavioral arousal, we investigated whether the histaminergic system represents a target for immune activation and, if so, whether modulation by ascending medullary immune-sensitive projections represents a possible mechanism. Rats were injected intraperitoneally with either the pro-inflammatory stimulus lipopolysaccharide (LPS) or saline, and exposed to one of various behavioral tests that would induce motivated behavior (exploration, play behavior, social interaction, sweetened milk consumption). Upon kill, brains were processed for c-Fos and histidine decarboxylase immunoreactivity. LPS treatment reduced behavioral activity and blocked behavioral test-associated c-Fos induction in histaminergic neurons of the VTM. These effects of LPS were prevented by prior inactivation of the caudal medullary dorsal vagal complex (DVC) with a local anesthetic. To determine whether LPS-responsive brainstem projection neurons might provide a link from the DVC to the VTM, the tracer Fluorogold was iontophoresed into the VTM a week prior to experiment. Retrogradely labeled neurons that expressed c-Fos in response to LPS treatment included catecholaminergic neurons within the nucleus of the solitary tract and ventrolateral medulla. These findings support the hypothesis that the histaminergic system represents an important component in the neurocircuitry relevant for sickness behavior that is linked to ascending pathways originating in the lower brainstem.
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Affiliation(s)
- R P A Gaykema
- Program in Sensory and Systems Neuroscience, Department of Psychology, P.O. Box 400400, University of Virginia, Charlottesville, VA 22904-4400, USA.
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17
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De Gobbi JIF, Menani JV, Beltz TG, Johnson RF, Thunhorst RL, Johnson AK. Right atrial stretch alters fore- and hind-brain expression of c-fos and inhibits the rapid onset of salt appetite. J Physiol 2008; 586:3719-29. [PMID: 18556369 DOI: 10.1113/jphysiol.2008.151282] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The inflation of an intravascular balloon positioned at the superior vena cava and right atrial junction (SVC-RAJ) reduces sodium or water intake induced by various experimental procedures (e.g. sodium depletion; hypovolaemia). In the present study we investigated if the stretch induced by a balloon at this site inhibits a rapid onset salt appetite, and if this procedure modifies the pattern of immunohistochemical labelling for Fos protein (Fos-ir) in the brain. Male Sprague-Dawley rats with SVC-RAJ balloons received a combined treatment of furosemide (Furo; 10 mg (kg bw)(-1)) plus a low dose of the angiotensin-converting enzyme inhibitor captopril (Cap; 5 mg (kg bw)(-1)). Balloon inflation greatly decreased the intake of 0.3 m NaCl for as long as the balloon was inflated. Balloon inflation over a 3 h period following Furo-Cap treatment decreased Fos-ir in the organum vasculosum of the lamina terminalis and the subfornical organ and increased Fos-ir in the lateral parabrachial nucleus and caudal ventrolateral medulla. The effect of balloon inflation was specific for sodium intake because it did not affect the drinking of diluted sweetened condensed milk. Balloon inflation and deflation also did not acutely change mean arterial pressure. These results suggest that activity in forebrain circumventricular organs and in hindbrain putative body fluid/cardiovascular regulatory regions is affected by loading low pressure mechanoreceptors at the SVC-RAJ, a manipulation that also attenuates salt appetite.
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McKinley MJ, Walker LL, Alexiou T, Allen AM, Campbell DJ, Di Nicolantonio R, Oldfield BJ, Denton DA. Osmoregulatory fluid intake but not hypovolemic thirst is intact in mice lacking angiotensin. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1533-43. [DOI: 10.1152/ajpregu.00848.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Water intakes in response to hypertonic, hypovolemic, and dehydrational stimuli were investigated in mice lacking angiotensin II as a result of deletion of the angiotensinogen gene (Agt−/− mice), and in C57BL6 wild-type (WT) mice. Baseline daily water intake in Agt−/− mice was approximately threefold that of WT mice because of a renal developmental disorder of the urinary concentrating mechanisms in Agt−/− mice. Intraperitoneal injection of hypertonic saline (0.4 and 0.8 mol/l NaCl) caused a similar dose-dependent increase in water intake in both Agt−/− and WT mice during the hour following injection. As well, Agt−/− mice drank appropriate volumes of water following water deprivation for 7 h. However, Agt−/− mice did not increase water or 0.3 mol/l NaCl intake in the 8 h following administration of a hypovolemic stimulus (30% polyethylene glycol sc), whereas WT mice increased intakes of both solutions during this time. Osmoregulatory regions of the brain [hypothalamic paraventricular and supraoptic nuclei, median preoptic nucleus, organum vasculosum of the lamina terminalis (OVLT), and subfornical organ] showed an increased number of neurons exhibiting Fos-immunoreactivity in response to intraperitoneal hypertonic NaCl in both Agt−/− mice and WT mice. Polyethylene glycol treatment increased Fos-immunoreactivity in the subfornical organ, OVLT, and supraoptic nuclei in WT mice but only increased Fos-immunoreactivity in the supraoptic nucleus in Agt−/− mice. These data show that brain angiotensin is not essential for the adequate functioning of neural pathways mediating osmoregulatory thirst. However, angiotensin II of either peripheral or central origin is probably necessary for thirst and salt appetite that results from hypovolemia.
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19
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Ruginsk SG, Oliveira FRT, Margatho LO, Vivas L, Elias LLK, Antunes-Rodrigues J. Glucocorticoid modulation of neuronal activity and hormone secretion induced by blood volume expansion. Exp Neurol 2007; 206:192-200. [PMID: 17553493 DOI: 10.1016/j.expneurol.2007.04.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2007] [Revised: 04/02/2007] [Accepted: 04/07/2007] [Indexed: 11/29/2022]
Abstract
The present study evaluated the involvement of glucocorticoid in the activation of vasopressinergic and oxytocinergic neurons of hypothalamic nuclei and plasma levels of vasopressin (AVP), oxytocin (OT), atrial natriuretic peptide (ANP) and corticosterone (CORT) in response to both isotonic and hypertonic blood volume expansion (BVE). Rats were subjected to isotonic (0.15 M NaCl, 2 ml/100 g b.w., i.v.) or hypertonic (0.30 M NaCl, 2 ml/100 g b.w., i.v.) BVE with or without pre-treatment with dexamethasone (1 mg/kg, i.p.). Results showed that isotonic BVE increased OT, ANP and CORT, and decreased AVP plasma levels. On the other hand, hypertonic BVE enhanced AVP, ANP, OT, and CORT plasma concentrations. Both hypertonic and isotonic BVE induced an increase in the number of Fos-OT double-labeled magnocellular neurons in the PVN and SON. Pre-treatment with dexamethasone reduced OT secretion, as well as Fos-OT immunoreactive neurons in response to both isotonic and hypertonic BVE. We also observed that dexamethasone pre-treatment had no effect on AVP secretion in response to hypertonic BVE, although this effect was associated with a blockade of Fos expression in the vasopressinergic magnocellular neurons in the PVN and SON. In conclusion, these data suggest that, not only the rapid OT release from storages, but also the oxytocinergic cellular activation induced by BVE are modulated by glucocorticoids. However, this pattern of response was not observed for AVP cells, suggesting that dexamethasone is not likely to influence rapid release of AVP but seems to modulate the activation of these neurons in response to hypertonic BVE.
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Affiliation(s)
- S G Ruginsk
- Departamento de Fisiologia, Faculdade de Medicina de Ribeirao Preto, Universidade de São Paulo, Brazil
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20
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Margatho LO, Giusti-Paiva A, Menani JV, Elias LLK, Vivas LM, Antunes-Rodrigues J. Serotonergic mechanisms of the lateral parabrachial nucleus in renal and hormonal responses to isotonic blood volume expansion. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1190-7. [PMID: 17138727 DOI: 10.1152/ajpregu.00351.2006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigated the involvement of serotonergic mechanisms of the lateral parabrachial nucleus (LPBN) in the control of sodium (Na+) excretion, potassium (K+) excretion, and urinary volume in unanesthetized rats subjected to acute isotonic blood volume expansion (0.15 M NaCl, 2 ml/100 g of body wt over 1 min) or control rats. Plasma oxytocin (OT), vasopressin (VP), and atrial natriuretic peptide (ANP) levels were also determined in the same protocol. Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used. In rats treated with vehicle in the LPBN, blood volume expansion increased urinary volume, Na+ and K+ excretion, and also plasma ANP and OT. Bilateral injections of serotonergic receptor antagonist methysergide (1 or 4 μg/200 ηl) into the LPBN reduced the effects of blood volume expansion on increased Na+ and K+ excretion and urinary volume, while LPBN injections of serotonergic 5-HT2a/HT2c receptor agonist, 2.5-dimetoxi-4-iodoamphetamine hydrobromide (DOI; 1 or 5 μg/200 ηl) enhanced the effects of blood volume expansion on Na+ and K+ excretion and urinary volume. Methysergide (4 μg) into the LPBN decreased the effects of blood volume expansion on plasma ANP and OT, while DOI (5 μg) increased them. The present results suggest the involvement of LPBN serotonergic mechanisms in the regulation of urinary sodium, potassium and water excretion, and hormonal responses to acute isotonic blood volume expansion.
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Affiliation(s)
- Lisandra Oliveira Margatho
- Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Avenida Bandeirantes 3900, 14049-900 Ribeirao Preto-Sao Paulo, Brazil
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21
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Stocker SD, Toney GM. Vagal afferent input alters the discharge of osmotic and ANG II-responsive median preoptic neurons projecting to the hypothalamic paraventricular nucleus. Brain Res 2006; 1131:118-28. [PMID: 17161831 PMCID: PMC1847371 DOI: 10.1016/j.brainres.2006.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Revised: 09/27/2006] [Accepted: 11/01/2006] [Indexed: 01/01/2023]
Abstract
The goal of the present study was to determine the effect of activating vagal afferent fibers on the discharge of median preoptic (MnPO) neurons responsive to peripheral angiotensin II (ANG II) and osmotic inputs. Vagal afferents were activated by electrical stimulation of the proximal end of the transected cervical vagus nerve (3 pulses, 100 Hz, 1 ms, 100-500 muA). Of 21 MnPO neurons, 19 were antidromically activated from the hypothalamic paraventricular nucleus (PVH) (latency: 10.3+/-1.3 ms, threshold: 278+/-25 muA). MnPO-PVH cells had an average spontaneous discharge of 2.1+/-0.4 Hz. Injection of ANG II (150 ng) and/or hypertonic NaCl (1.5 Osm/L, 100 mul) through the internal carotid artery significantly (P<0.01) increased the firing rate of most MnPO-PVH neurons (16/19, 84%). Vagus nerve stimulation significantly (P<0.01) decreased discharge (-73+/-9%) in 10 of 16 (63%) neurons with an average onset latency of 108+/-19 ms. Among the remaining 6 MnPO-PVH neurons vagal activation either increased discharge (177+/-100%) with a latency of 115+/-15 ms (n=2) or had no effect (n=4). Pharmacological activation of chemosensitive vagal afferents with phenyl biguanide produced an increase (n=3), decrease (n=2), or no change (n=6) in discharge. These observations indicate that a significant proportion of ANG II- and/or osmo-sensitive MnPO neurons receive convergent vagal input. Although the sensory modalities transmitted by the vagal afferents to MnPO-PVH neurons are not presently known, the presence of inhibitory and excitatory vagal-evoked responses indicates that synaptic processing by these cells integrates humoral and visceral information to subserve potentially important cardiovascular and body fluid homeostatic functions.
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Affiliation(s)
- Sean D Stocker
- Department of Physiology, University of Kentucky College of Medicine, 800 Rose St. MS-508, Lexington, KY 40536-0298, USA.
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22
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Glass MJ, Huang J, Oselkin M, Tarsitano MJ, Wang G, Iadecola C, Pickel VM. Subcellular localization of nicotinamide adenine dinucleotide phosphate oxidase subunits in neurons and astroglia of the rat medial nucleus tractus solitarius: relationship with tyrosine hydroxylase immunoreactive neurons. Neuroscience 2006; 143:547-64. [PMID: 17027166 PMCID: PMC1808229 DOI: 10.1016/j.neuroscience.2006.08.051] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 07/06/2006] [Accepted: 08/04/2006] [Indexed: 02/07/2023]
Abstract
Superoxide produced by the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediates crucial intracellular signaling cascades in the medial nucleus of the solitary tract (mNTS), a brain region populated by catecholaminergic neurons, as well as astroglia that play an important role in autonomic function. The mechanisms mediating NADPH oxidase (phagocyte oxidase) activity in the neural regulation of cardiovascular processes are incompletely understood, however the subcellular localization of superoxide produced by the enzyme is likely to be an important regulatory factor. We used immunogold electron microscopy to determine the phenotypic and subcellular localization of the NADPH oxidase subunits p47(phox), gp91(phox,) and p22(phox) in the mNTS in rats. The mNTS contains a large population of neurons that synthesize catecholamines. Significantly, catecholaminergic signaling can be modulated by redox reactions. Therefore, the relationship of NADPH oxidase subunit labeled neurons or glia with respect to catecholaminergic neurons was also determined by dual labeling for the superoxide producing enzyme and tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. In the mNTS, NADPH oxidase subunits were present primarily in somatodendritic processes and astrocytes, some of which also contained TH, or were contacted by TH-labeled axons, respectively. Immunogold quantification of NADPH oxidase subunit localization showed that p47(phox) and gp91(phox) were present on the surface membrane, as well as vesicular organelles characteristic of calcium storing smooth endoplasmic reticula in dendritic and astroglial processes. These results indicate that NADPH oxidase assembly and consequent superoxide formation are likely to occur near the plasmalemma, as well as on vesicular organelles associated with intracellular calcium storage within mNTS neurons and glia. Thus, NADPH oxidase-derived superoxide may participate in intracellular signaling pathways linked to calcium regulation in diverse mNTS cell types. Moreover, NADPH oxidase-derived superoxide in neurons and glia may directly or indirectly modulate catecholaminergic neuron activity in the mNTS.
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Affiliation(s)
- M J Glass
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA.
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23
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Pedrino GR, Maurino I, de Almeida Colombari DS, Cravo SL. Role of catecholaminergic neurones of the caudal ventrolateral medulla in cardiovascular responses induced by acute changes in circulating volume in rats. Exp Physiol 2006; 91:995-1005. [PMID: 16916893 DOI: 10.1113/expphysiol.2006.034611] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Several findings suggest that catecholaminergic neurones in the caudal ventrolateral medulla (CVLM) contribute to body fluid homeostasis and cardiovascular regulation. The present study sought to determine the effects of lesions of these neurones on the cardiovascular responses induced by changes in circulating volume. All experiments were performed in male Wistar rats (320-360 g). Medullary catecholaminergic neurones were lesioned by microinjection of anti-dopamine beta-hydroxylase-saporin (6.3 ng in 60 nl; SAP rats, n = 14) into the CVLM, whereas sham rats received microinjections of free saporin (1.3 ng in 60 nl, n = 15). Two weeks later, rats were anaesthetized (urethane, 1.2 g kg(-1), i.v.), instrumented for measurement of mean arterial pressure (MAP), renal blood flow (RBF) and renal vascular conductance (RVC), and infused with hypertonic saline (HS; 3 m NaCl, 0.18 ml (100 g body weight)(-1), i.v.) or an isotonic solution (volume expansion, VE; 4% Ficoll, 1% of body weight, i.v.). In sham rats, HS induced sustained increases in RBF and RVC (155 +/- 7 and 145 +/- 6% of baseline, at 20 min after HS). In SAP rats, RBF responses to HS were blunted (125 +/- 6%) and RVC increases were abolished (108 +/- 5%) 20 min after HS. Isotonic solution increased RBF and RVC in sham rats (149 +/- 10 and 145 +/- 12% of baseline, respectively, at 20 min). These responses were reduced in SAP rats (131 +/- 6 and 126 +/- 5%, respectively, at 20 min). Pressor responses to HS were larger in SAP rats than in sham rats (17 +/- 5 versus 9 +/- 2 mmHg, at 20 min), whereas during VE these responses were similar in both groups (6 +/- 3 versus 4 +/- 6 mmHg, at 20 min). Immunohistochemical analysis indicates that microinjections of anti-DbetaH-saporin produced extensive destruction within the A1/C1 cell groups in the CVLM. These results suggest that catecholaminergic neurones mediate the cardiovascular responses to VE or increases in plasma sodium levels.
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Affiliation(s)
- Gustavo Rodrigues Pedrino
- Department of Physiology, Universidade Federal de São Paulo - Escola Paulista de Medicina, São Paulo, SP, Brazil
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24
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Ji LL, Gottlieb HB, Penny ML, Fleming T, Toney GM, Cunningham JT. Differential effects of water deprivation and rehydration on Fos and FosB/DeltaFosB staining in the rat brainstem. Exp Neurol 2006; 203:445-56. [PMID: 17027755 DOI: 10.1016/j.expneurol.2006.08.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 08/24/2006] [Accepted: 08/28/2006] [Indexed: 11/27/2022]
Abstract
This study examined the effects of dehydration and rehydration with water on Fos and FosB staining in the brainstem of rats. Male rats were water deprived for 48 h (Dehyd, n=7) or 46 h followed by 2 h access to water (Rehyd, n=7). Controls had ad libitum access to water (Con, n=9). Brainstems were stained for Fos and FosB/DeltaFosB using commercially available antibodies. In the nucleus of the solitary tract (NTS), the number of Fos stained neurons was significantly increased by dehydration and increased further following rehydration (Con 5+/-1; Dehyd 22+/-1; Rehyd 48+/-5). The average number of Fos-positive cells in the parabrachial nucleus (PBN) was significantly increased only by rehydration (Con 12+/-2; Dehyd 6+/-2; Rehyd 51+/-4). The area postrema (AP) showed significant increases in Fos staining after dehydration and rehydration (Fos: Con 4+/-1; Dehyd 28+/-3; Rehyd 24+/-3). In the rostral ventrolateral medulla (RVL), Fos staining significantly increased after dehydration and this effect was reduced by rehydration (Con 3+/-1; Dehyd 21+/-2; Rehyd 12+/-1). In contrast, Fos staining in the caudal ventrolateral medulla (CVL) was not significantly influenced following either dehydration or rehydration with water (Con 4+/-1; Dehyd 4+/-1; Rehyd 5+/-1). FosB/DeltaFosB staining in the NTS, AP, and RVL was comparably increased by dehydration and rehydration. In the PBN and CVL, FosB/DeltaFosB staining was not affected by the treatments. Dehydration and rehydration have regionally specific effects on Fos and FosB/DeltaFosB staining in the brainstem.
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Affiliation(s)
- Lisa L Ji
- Department of Pharmacology, and the Center for Biomedical Neuroscience, UTHSCSA, USA
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25
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Yang Z, Coote JH. The role of supraspinal vasopressin and glutamate neurones in an increase in renal sympathetic activity in response to mild haemorrhage in the rat. Exp Physiol 2006; 91:791-7. [PMID: 16698894 DOI: 10.1113/expphysiol.2006.034082] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study investigated the importance of supraspinal vasopressin and glutamate neurones in regulating renal sympathetic activity as part of the response to an acute reduction in blood volume. Wistar rats anaesthetized with chloralose and urethane were instrumented to record arterial blood pressure, heart rate and left renal sympathetic nerve activity. Pharmacological agonists and antagonists to glutamate and vasopressin were applied to the renal outflow of the spinal cord via an intrathecal catheter inserted at the foramen magnum and with the tip at the level of T10. Both glutamate and vasopressin increased renal sympathetic activity, and these actions were shown to be selectively blocked by their respective antagonists. Removing 1 ml of venous blood from a femoral venous catheter elicited an increase of 26 +/- 2% in renal sympathetic activity. This response to mild haemorrhage was halved to 13 +/- 4% by prior intrathecal application of a selective V1a antagonist. Similarly, prior intrathecal application of kynurenic acid reduced the response to the mild haemorrhage from 28 +/- 2 to 12.6 +/- 2.8%. Intrathecal application of both antagonists together reduced the haemorrhage response even further to 8 +/- 3%. All the changes were statistically significant at P < 0.01. It is concluded that a small reduction in blood volume induces an increase in renal sympathetic activity dependent on vasopressin and glutamate release from terminals of supraspinal neurones. It is suggested that the vasopressin neurones most probably originate from the paraventricular nucleus of the hypothalamus.
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Affiliation(s)
- Zhou Yang
- Medical College, University of Nankai, Tianjin, PR China
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26
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Kantzides A, Badoer E. Activation of NADPH-diaphorase-positive projections to the rostral ventrolateral medulla following cardiac mechanoreceptor stimulation in the conscious rat. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1626-38. [PMID: 16682470 DOI: 10.1152/ajpregu.00532.2005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Stimulation of cardiac mechanoreceptors during volume expansion elicits reflex compensatory changes in sympathetic nerve activity (SNA). The hypothalamic paraventricular nucleus (PVN) and nucleus of the tractus solitarius (NTS) are autonomic regions known to contribute to this reflex. Both of these nuclei project to the rostral ventrolateral medulla (RVLM), critical in the tonic generation of SNA. Recent reports from our laboratory show that these pathways 1) are activated following cardiac mechanoreceptor stimulation, and 2) produce nitric oxide, known to influence SNA. The aims of the present study were to determine whether 1) the activated neurons within the PVN and NTS were nitrergic and 2) these neurons projected to the RVLM. Animals were prepared, under general anesthesia, by microinjection of a retrogradely transported tracer into the pressor region of the RVLM and the placement of a balloon at the right venoatrial junction. In conscious rats, the balloon was inflated to stimulate the cardiac mechanoreceptors or was left uninflated. Balloon inflation elicited a significant increase in Fos-positive neurons in the parvocellular PVN (sevenfold) and NTS (fivefold). In the PVN, 51% of nitrergic neurons and 61% of RVLM-projecting nitrergic neurons were activated. In the NTS, these proportions were 8 and 18%, respectively. The data suggest that nitrergic neurons within the PVN and, to a lesser extent, in the NTS, some of which project to the RVLM, may contribute to the central pathways influencing SNA elicited by cardiac mechanoreceptor stimulation.
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Affiliation(s)
- A Kantzides
- School of Medical Sciences, RMIT University, PO Box 71, Bundoora 3083, Melbourne, Victoria, Australia
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27
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Göktalay G, Cavun S, Levendusky MC, Resch GE, Veno PA, Millington WR. Hemorrhage activates proopiomelanocortin neurons in the rat hypothalamus. Brain Res 2006; 1070:45-55. [PMID: 16403465 DOI: 10.1016/j.brainres.2005.11.076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Revised: 11/11/2005] [Accepted: 11/12/2005] [Indexed: 11/29/2022]
Abstract
Severe blood loss lowers arterial pressure through a central mechanism that is thought to include opioid neurons. In this study, we investigated whether hemorrhage activates proopiomelanocortin (POMC) neurons by measuring Fos immunoreactivity and POMC mRNA levels in the medial basal hypothalamus. Hemorrhage (2.2 ml/100 g body weight over 20 min) increased the number of Fos immunoreactive neurons throughout the rostral-caudal extent of the arcuate nucleus, the retrochiasmatic area and the peri-arcuate region lateral to the arcuate nucleus where POMC neurons are located. Double label immunohistochemistry revealed that hemorrhage increased Fos expression by beta-endorphin immunoreactive neurons significantly. The proportion of beta-endorphin immunoreactive neurons that expressed Fos immunoreactivity increased approximately four-fold, from 11.7+/-1.4% in sham-operated control animals to 42.0+/-5.2% in hemorrhaged animals. Hemorrhage also increased POMC mRNA levels in the medial basal hypothalamus significantly, consistent with the hypothesis that blood loss activates POMC neurons. To test whether activation of arcuate neurons contributes to the fall in arterial pressure evoked by hemorrhage, we inhibited neuronal activity in the caudal arcuate nucleus by microinjecting the local anesthetic lidocaine (2%; 0.1 or 0.3 microl) bilaterally 2 min before hemorrhage was initiated. Lidocaine injection inhibited hemorrhagic hypotension and bradycardia significantly although it did not influence arterial pressure or heart rate in non-hemorrhaged rats. These results demonstrate that hemorrhage activates POMC neurons and provide evidence that activation of neurons in the arcuate nucleus plays an important role in the hemodynamic response to hemorrhage.
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Affiliation(s)
- Gökhan Göktalay
- Department of Basic and Pharmaceutical Sciences, Albany College of Pharmacy, Union University, 106 New Scotland Avenue, Albany, NY 12208-3492, USA
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28
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Benarroch EE. Paraventricular nucleus, stress response, and cardiovascular disease. Clin Auton Res 2005; 15:254-63. [PMID: 16032381 DOI: 10.1007/s10286-005-0290-7] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Accepted: 04/21/2005] [Indexed: 02/07/2023]
Abstract
The paraventricular nucleus of the hypothalamus (PVN) is a complex effector structure that initiates endocrine and autonomic responses to stress. It receives inputs from visceral receptors, circulating hormones such as angiotensin II, and limbic circuits and contains neurons that release vasopressin, activate the adrenocortical axis, and activate preganglionic sympathetic or parasympathetic outflows. The neurochemical control of the different subgroups of PVN neurons is complex. The PVN has been implicated in the pathophysiology of congestive heart failure and the metabolic syndrome.
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Affiliation(s)
- Eduardo E Benarroch
- Mayo Clinic, Dept. of Neurology, 811 Guggenheim Building, 200 First Street SW, Rochester, MN 55905, USA.
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29
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Kantzides A, Owens NC, De Matteo R, Badoer E. Right atrial stretch activates neurons in autonomic brain regions that project to the rostral ventrolateral medulla in the rat. Neuroscience 2005; 133:775-86. [PMID: 15896916 DOI: 10.1016/j.neuroscience.2005.02.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 02/17/2005] [Accepted: 02/18/2005] [Indexed: 11/30/2022]
Abstract
Activation of the cardiac mechanoreceptors results in changes in sympathetic nerve activity and plays an important role in the responses elicited by elevated blood volume. Stimulation of the reflex influences several key autonomic regions, namely the paraventricular nucleus (PVN), the nucleus of the tractus solitarius (NTS) and the caudal ventrolateral medulla (CVLM). Neurons in these regions project directly to the rostral ventrolateral medulla (RVLM), a critical region in the generation of sympathetic vasomotor tone. The aim of the present experiments was to determine whether neurons in the PVN, NTS and CVLM that are activated by cardiac mechanoreceptor stimulation also project to the RVLM. Animals were prepared, under general anesthesia, by microinjection of a retrogradely transported tracer into the pressor region of the RVLM, and the placement of a balloon-tipped cannula at the junction of the right atrium and the superior vena cava. On the experimental day, in conscious rats, the balloon was inflated to stimulate cardiac mechanoreceptors (n = 9), or left uninflated (control, n = 8). Compared with controls, there was a significantly increased number of Fos-immunoreactive neurons (a marker of activation) in both the PVN (2.5-fold) and NTS (two-fold), but this was not seen in the CVLM. Compared with controls, a significant number of the neurons in the PVN (8%) and NTS (4.0%) that projected to the RVLM were activated. The data suggest that subgroups of RVLM-projecting neurons located in the PVN and NTS are involved in the central reflex pathway activated by cardiac mechanoreceptor stimulation.
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Affiliation(s)
- A Kantzides
- School of Medical Sciences, Division of Biosciences, RMIT University, PO Box 71, Bundoora 3083, Melbourne, Victoria, Australia
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Godino A, Giusti-Paiva A, Antunes-Rodrigues J, Vivas L. Neurochemical brain groups activated after an isotonic blood volume expansion in rats. Neuroscience 2005; 133:493-505. [PMID: 15885915 DOI: 10.1016/j.neuroscience.2005.02.035] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Revised: 02/03/2005] [Accepted: 02/06/2005] [Indexed: 11/23/2022]
Abstract
In order to establish the involvement of particular neurochemical brain groups in the response to blood volume expansion, we analyzed Fos-labeling in combination with immunolabeling for serotonin, tyrosine hydroxylase, vasopressin and oxytocin, 90 min after a sham or i.v. isotonic blood volume expansion (BVE) in unanesthetized, unrestrained rats. We also examined the changes in concentration of oxytocin, atrial natriuretic peptide and vasopressin plasma, induced by blood volume load, to confirm our previous studies. The results demonstrate the participation of specific paraventricular and supraoptic nucleus groups of cells (oxytocinergic-vasopressinergic), serotoninergic dorsal raphe nucleus cells and catecholaminergic A1/A2/A6 groups (in the caudal ventrolateral medulla, nucleus of the solitary tract and locus coeruleus respectively), in the regulatory response to BVE. They provide detailed neuroanatomical evidence to support previous observations showing the contribution of these neurochemical systems in the neural, behavioral and endocrine response to isotonic BVE.
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Affiliation(s)
- A Godino
- Instituto de Investigación Médica M. y M. Ferreyra (INIMEC-CONICET), Casilla de Correo 389-5000, Córdoba, Argentina
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Stocker SD, Cunningham JT, Toney GM. Water deprivation increases Fos immunoreactivity in PVN autonomic neurons with projections to the spinal cord and rostral ventrolateral medulla. Am J Physiol Regul Integr Comp Physiol 2004; 287:R1172-83. [PMID: 15271657 DOI: 10.1152/ajpregu.00394.2004] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study sought to determine whether water deprivation increases Fos immunoreactivity, a neuronal marker related to synaptic activation, in sympathetic-regulatory neurons of the hypothalamic paraventricular nucleus (PVN). Fluorogold (4%, 50 nl) and cholera toxin subunit B (0.25%, 20-30 nl) were microinjected into the spinal cord (T1-T3) and rostral ventrolateral medulla (RVLM), respectively. Rats were then deprived of water but not food for 48 h. Water deprivation significantly increased the number of Fos-positive nuclei throughout the dorsal, ventrolateral, and lateral parvocellular divisions of the PVN (water deprived, 215 +/- 23 cells; control, 45 +/- 7 cells, P < 0.01). Moreover, a significantly greater number of Fos-positive nuclei were localized in spinally projecting (11 +/- 3 vs. 2 +/- 1 cells, P < 0.025) and RVLM-projecting (45 +/- 7 vs. 7 +/- 1 cells, P < 0.025) neurons of the PVN in water-deprived vs. control rats, respectively. The majority of these double-labeled neurons was found in the ventrolateral and lateral parvocellular divisions of the ipsilateral PVN. Interestingly, a significantly greater percentage of RVLM-projecting PVN neurons were Fos positive compared with spinally projecting PVN neurons in the ventrolateral (25.8 +/- 0.7 vs. 8.0 +/- 1.5%, respectively, P < 0.01) and lateral (23.4 +/- 2.1 vs. 5.0 +/- 0.9%, respectively, P > 0.01) parvocellular divisions. In addition, we analyzed spinally projecting neurons of the RVLM and found a significantly greater percentage were Fos positive in water-deprived rats than in control rats (26 +/- 3 vs. 3 +/- 1%, respectively; P < 0.001). Collectively, the present findings indicate that water deprivation evokes a distinct cellular response in sympathetic-regulatory neurons of the PVN and RVLM.
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Affiliation(s)
- Sean D Stocker
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
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Howe BM, Bruno SB, Higgs KAN, Stigers RL, Cunningham JT. FosB expression in the central nervous system following isotonic volume expansion in unanesthetized rats. Exp Neurol 2004; 187:190-8. [PMID: 15081600 DOI: 10.1016/j.expneurol.2004.01.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Revised: 01/20/2004] [Accepted: 01/22/2004] [Indexed: 11/17/2022]
Abstract
We examined c-Fos and FosB staining in the central nervous system 8 and 24 h following acute volume expansion in unanesthetized rats. Male rats were instrumented with a femoral artery catheter for measurement of blood pressure and heart rate (HR), a jugular venous catheter for measurement of central venous pressure (CVP), and a femoral vein catheter for i.v. infusion. After 48 h, rats were volume expanded with isotonic saline (10% of body weight for 10 min i.v.) or given a control infusion (0.01 ml/min for 10 min i.v.). After a period of 8 or 24 h, the rats were deeply anesthetized and perfused transcardially with 4% paraformaldehyde. Separate sets of serial sections of the hypothalamus were processed for either FosB (Santa Cruz) or c-Fos (Oncogene AB-5) immunocytochemistry. The volume expansion protocol significantly increased central venous pressure but did not affect blood pressure or heart rate. Volume expansion produced a significant increase in FosB-positive cells in the paraventricular nucleus (PVN) of the hypothalamus, the supraoptic nucleus (SON), the perinuclear zone (PNZ) of the supraoptic nucleus, the nucleus of the solitary tract (NST), and the caudal ventrolateral medulla (CVL) in both the 8- and 24-h groups. In the area postrema (AP), the number of FosB-positive cells was significantly increased only at 8 h post-infusion. However, c-Fos was not significantly increased above control levels at either time point. The results demonstrate that FosB activation is maintained for at least 24 h following an acute increase in central venous pressure.
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Affiliation(s)
- B Matthew Howe
- Department of Medical Pharmacology and Physiology and the Dalton Cardiovascular Research Center, University of Missouri-Columbia, USA
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Dampney RAL, Horiuchi J. Functional organisation of central cardiovascular pathways: studies using c-fos gene expression. Prog Neurobiol 2003; 71:359-84. [PMID: 14757116 DOI: 10.1016/j.pneurobio.2003.11.001] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Until about 10 years ago, knowledge of the functional organisation of the central pathways that subserve cardiovascular responses to homeostatic challenges and other stressors was based almost entirely on studies in anaesthetised animals. More recently, however, many studies have used the method of the expression of immediate early genes, particularly the c-fos gene, to identify populations of central neurons that are activated by such challenges in conscious animals. In this review we first consider the advantages and limitations of this method. Then, we discuss how the application of the method of immediate early gene expression, when used alone or in combination with other methods, has contributed to our understanding of the central mechanisms that regulate the autonomic and neuroendocrine response to various cardiovascular challenges (e.g., hypotension, hypoxia, hypovolemia, and other stressors) as they operate in the conscious state. In general, the results of studies of central cardiovascular pathways using immediate early gene expression are consistent with previous studies in anaesthetised animals, but in addition have revealed other previously unrecognised pathways that also contribute to cardiovascular regulation. Finally, we briefly consider recent evidence indicating that immediate early gene expression can modify the functional properties of central cardiovascular neurons, and the possible significance of this in producing long-term changes in the regulation of the cardiovascular system both in normal and pathological conditions.
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Affiliation(s)
- R A L Dampney
- Department of Physiology and Institute for Biomedical Research, University of Sydney, Sydney, NSW 2006, Australia.
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Abstract
Medullary catecholamine and hypothalamic neurosecretory oxytocin cells are activated by hypotension, but previous studies have provided uncertain outcomes concerning their ability to respond to a purely hypovolaemic stimulus. In the present study, injections of PEG/water and pentolinium were used to elicit non-hypotensive, isosmotic hypovolaemia and isovolaemic, isosmotic hypotension, respectively, in conscious rats. Animals were sacrificed 2 h after treatment. Immunolabelling for Fos, tyrosine hydroxylase and oxytocin established that these two stimuli activate almost identical populations of catecholamine neurons in the ventrolateral and dorsomedial medulla, and very similar populations of oxytocin cells in the supraoptic and paraventricular nuclei of the hypothalamus.
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Affiliation(s)
- Doug W Smith
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
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Boudaba C, Di S, Tasker JG. Presynaptic noradrenergic regulation of glutamate inputs to hypothalamic magnocellular neurones. J Neuroendocrinol 2003; 15:803-10. [PMID: 12834442 DOI: 10.1046/j.1365-2826.2003.01063.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutamate and norepinephrine transmitter systems play critical roles in the synaptic control of hypothalamic magnocellular neurones. We recently reported on a norepinephrine-sensitive glutamate circuit within the paraventricular nucleus (PVN) that projects to magnocellular neurones. Here, we present evidence for norepinephrine regulation of glutamate release in the PVN and supraoptic nucleus (SON) via actions on presynaptic terminals. Whole-cell synaptic currents were recorded in magnocellular neurones of the SON and PVN in an acute slice preparation. Bath application of norepinephrine (100 microm) caused a robust, reversible increase in the frequency of spontaneous glutamatergic excitatory postsynaptic currents in 100% of SON neurones (246%) and in 88% of PVN magnocellular neurones (259%). The norepinephrine-induced increase in glutamate release was mediated by activation of both presynaptic alpha1 receptors and alpha2 receptors, but the alpha1-receptor component was the predominant component of the response. The presynaptic actions of norepinephrine were predominantly, although not completely, resistant to blockade of Na-dependent spikes, implicating a presynaptic terminal locus of action. Interestingly, the spike-dependent component of the response was greater in PVN than in SON magnocellular neurones. This robust presynaptic facilitation of glutamate release by norepinephrine, combined with the known excitatory postsynaptic actions of norepinephrine, activational effects on local glutamate circuits, and inhibitory effects on gamma-aminobutyric acid release, indicate a strong excitatory role of norepinephrine in the regulation of oxytocin and vasopressin release during physiological stimulation.
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Affiliation(s)
- C Boudaba
- Neurobiology Division, Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
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Mueller PJ, Hasser EM. Enhanced sympathoinhibitory response to volume expansion in conscious hindlimb-unloaded rats. J Appl Physiol (1985) 2003; 94:1806-12. [PMID: 12533501 DOI: 10.1152/japplphysiol.00979.2002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prolonged exposure to microgravity or bed rest produces cardiovascular deconditioning, which is characterized by reductions in plasma volume, alterations in autonomic function, and a predisposition toward orthostatic intolerance. Although the precise mechanisms have not been fully elucidated, it is possible that augmented cardiopulmonary reflexes contribute to some of these effects. The purpose of the present study was to test the hypothesis that sympathoinhibitory responses to volume expansion are enhanced in the hindlimb-unloaded (HU) rat, a model of cardiovascular deconditioning. Mean arterial blood pressure, heart rate, and renal sympathetic nerve activity (RSNA) responses to isotonic volume expansion (0.9% saline iv, 15% of plasma volume over 5 min) were examined in conscious HU (14 days) and control animals. Volume expansion produced decreases in RSNA in both groups; however, this effect was significantly greater in HU rats (-46 +/- 7 vs. -25 +/- 4% in controls). Animals instrumented for central venous pressure (CVP) did not exhibit differences in CVP responses to volume expansion. These data suggest that enhanced cardiopulmonary reflexes may be involved in the maintenance of reduced plasma volume and contribute to attenuated baroreflex-mediated sympathoexcitation after spaceflight or bed rest.
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Affiliation(s)
- Patrick J Mueller
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri 65211, USA.
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Charron G, Laforest S, Gagnon C, Drolet G, Mouginot D. Acute sodium deficit triggers plasticity of the brain angiotensin type 1 receptors. FASEB J 2002; 16:610-2. [PMID: 11919170 DOI: 10.1096/fj.01-0531fje] [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: 11/11/2022]
Abstract
The brain renin-angiotensin system (bRAS) is involved in the control of hydromineral balance. However, little information is available on the functional regulation of the bRAS as a consequence of sodium deficit in the extracellular fluid compartments. We used a pharmacological model of acute Na+ depletion (furosemide injections) to investigate changes of a major component of the bRAS, the hypothalamic angiotensin type 1A (AT(1A)) receptors. Furosemide induced a rapid and long-lasting expression of the AT(1A) mRNA in the subfornical organ, the median preoptic nucleus (MnPO), and the parvocellular division of the paraventricular nucleus (pPVN). Na+ depletion increased the number of cells expressing AT(1A) mRNA in the pPVN, but not in the MnPO. The enhancement of AT(1A) mRNA expression was associated with an increase in AT(1) binding sites in all the regions studied. It is of interest that in the paraventricular nucleus, the majority of the neurons expressing AT(1A) mRNA also showed an increase in metabolic activity (Fos-related antigen immunoreactivity [FRA-ir]). By contrast, in the MnPO, we observe two distinct cell populations. Our data demonstrated that an acute Na+ deficit induced a functional regulation of the hypothalamic AT(1A) receptors, indicating that these receptors are subject to plasticity in response to hydromineral perturbations.
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Affiliation(s)
- Geneviève Charron
- Centre de Recherche du CHUL, Unité de Neuroscience, Université Laval, Québec, G1V 4G2, Canada
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Cunningham JT, Bruno SB, Higgs KAN, Sullivan MJ. Intrapericardial procaine affects volume expansion-induced fos immunoreactivity in unanesthetized rats. Exp Neurol 2002; 174:181-92. [PMID: 11922660 DOI: 10.1006/exnr.2002.7863] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Acute volume expansion is associated with a specific pattern of Fos expression and the goal of the present study was to evaluate the contribution of cardiac receptors to this response. Adult male rats were instrumented with pericardial catheters introduced at the level of the thymus. Rats were also catheterized for measuring blood pressure, heart rate, central venous pressure, and intravenous infusion. Each rat received a 200-microl intrapericardial (i.p.c) injection of 2% procaine or 0.9% NaCl. Rats were then volume expanded with isotonic saline (10% body weight in 10 min) or given a control infusion (0.01 ml/min for 10 min). Ninety minutes after the start of the infusion, the rats were anesthetized and perfused transcardially. Their brains were sectioned and processed for Fos, dopamine-beta-hydroxylase, and oxytocin immunocytochemistry. Volume expansion plus i.p.c. saline produced a significant increase in Fos expression in the nucleus of the solitary tract, the ventrolateral medulla, the area postrema, the locus coeruleus, the paraventricular nucleus of the hypothalamus, the perinuclear zone of the supraoptic nucleus, and oxytocin neurons in the supraoptic nucleus. The i.p.c. procaine significantly blocked Fos expression produced by the volume expansion in the all of the regions examined except for the area postrema and the SON oxytocin neurons.
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Affiliation(s)
- J Thomas Cunningham
- Department of Physiology & the Dalton Cardiovascular Research Center, Research Park, Columbia, Missouri 65211, USA
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Cunningham JT, Grindstaff RJ, Grindstaff RR, Sullivan MJ. Fos immunoreactivity in the diagonal band and the perinuclear zone of the supraoptic nucleus after hypertension and hypervolaemia in unanaesthetized rats. J Neuroendocrinol 2002; 14:219-27. [PMID: 11999722 DOI: 10.1046/j.0007-1331.2001.00765.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We used Fos immunocytochemistry to study the effects of hypertension and hypervolaemia on neurones in the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus, two nuclei that are both involved in the baroreceptor regulation of vasopressin neurones in the supraoptic nucleus. In addition, we used sino-aortic denervation to examine the role of arterial baroreceptors in the response to these haemodynamic changes. Sham-operated and sino-aortic denervated rats were infused with phenylephrine sufficient to increase blood pressure for 2 h. Control rats were infused with the same volume of isontonic saline. Only Sham sino-aortic denervated rats showed reflex bradycardia in response to the increased blood pressure. Volume expansion was produced by infusing the rats with isotonic saline equal to 10% of their body weight for 10 min, which significantly increased central venous pressure. In the diagonal band of Broca and the perinuclear zone, the number of Fos-positive neurones was significantly increased after phenylephrine infusion. Sino-aortic denervation blocked the significant increase in both regions. After volume expansion, a significant increase in Fos staining was observed only in the perinuclear zone of the supraoptic nucleus. This increase was not blocked by sino-aortic denervation. Our results indicate that both the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus are activated by stimulating arterial baroreceptors; however, the perinuclear zone of the supraoptic nucleus is stimulated during volume expansion. Furthermore, the activation of perinuclear zone of the supraoptic nucleus after volume expansion is not dependent on intact arterial baroreceptors.
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Affiliation(s)
- J T Cunningham
- Department of Physiology and the Dalton Cardiovascular Research Center, University of Missouri-Columbia, 65211, USA.
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Abstract
Most forms of hypertension are associated with a wide variety of functional changes in the hypothalamus. Alterations in the following substances are discussed: catecholamines, acetylcholine, angiotensin II, natriuretic peptides, vasopressin, nitric oxide, serotonin, GABA, ouabain, neuropeptide Y, opioids, bradykinin, thyrotropin-releasing factor, vasoactive intestinal polypeptide, tachykinins, histamine, and corticotropin-releasing factor. Functional changes in these substances occur throughout the hypothalamus but are particularly prominent rostrally; most lead to an increase in sympathetic nervous activity which is responsible for the rise in arterial pressure. A few appear to be depressor compensatory changes. The majority of the hypothalamic changes begin as the pressure rises and are particularly prominent in the young rat; subsequently they tend to fluctuate and overall to diminish with age. It is proposed that, with the possible exception of the Dahl salt-sensitive rat, the hypothalamic changes associated with hypertension are caused by renal and intrathoracic cardiopulmonary afferent stimulation. Renal afferent stimulation occurs as a result of renal ischemia and trauma as in the reduced renal mass rat. It is suggested that afferents from the chest arise, at least in part, from the observed increase in left auricular pressure which, it is submitted, is due to the associated documented impaired ability to excrete sodium. It is proposed, therefore, that the hypothalamic changes in hypertension are a link in an integrated compensatory natriuretic response to the kidney's impaired ability to excrete sodium.
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Affiliation(s)
- H E de Wardener
- Department of Clinical Chemistry, Imperial College School of Medicine, Charing Cross Campus, London, United Kingdom.
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Grindstaff RR, Cunningham JT. Cardiovascular regulation of vasopressin neurons in the supraoptic nucleus. Exp Neurol 2001; 171:219-26. [PMID: 11573974 DOI: 10.1006/exnr.2001.7745] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This paper reviews the regulation of hypothalamic vasopressin and oxytocin neurosecretory cells in the neural response to plasma volume expansion. Many questions remain unanswered regarding how an increase in volume affects neurohypophysial hormone secretion, what receptors are important in mediating this response, and which neural pathways are responsible for conveying the signal from those receptors to the hypothalamus. Plasma volume expansion activates regions of the central nervous system associated with inhibition of vasopressin release, oxytocin secretion, and inhibition of sympathetic nerve activity. Cardiac receptors, not arterial baroreceptors, are primarily responsible for activation of the regions associated with regulation of vasopressin secretion and sympathetic outflow. Other stimuli that as yet are undefined account for activation of oxytocin-secreting neurons. Electrophysiology experiments have measured the inhibition of vasopressin-secreting magnocellular neurons in the supraoptic nucleus by select stimulation of cardiac receptors in the caval-atrial junction. Further experiments suggest that the perinuclear zone, a population of neurons surrounding the supraoptic nucleus, is a necessary part of the pathway by which caval-atrial stretch decreases the excitability of vasopressin neurons. The perinuclear zone is also a necessary synapse for arterial baroreceptor-mediated inhibition of vasopressin neurons. This suggests that the neural pathways that inhibit vasopressin release in response to an increase in blood pressure and an increase in blood volume may overlap at the perinuclear zone of the supraoptic nucleus. Finally, the integration of various neural pathways activated by multiple receptors to ultimately determine the activity of magnocellular neurons and vasopressin secretion is discussed.
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Affiliation(s)
- R R Grindstaff
- Department of Physiology and the Dalton Cardiovascular Research Center, University of Missouri-Columbia, Columbia, Missouri 65211, USA
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Luoh SH, Chan SH. Inhibition of baroreflex by angiotensin II via Fos expression in nucleus tractus solitarii of the rat. Hypertension 2001; 38:130-5. [PMID: 11463773 DOI: 10.1161/01.hyp.38.1.130] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We evaluated the modulatory action of angiotensin II at the nucleus tractus solitarii on spontaneous baroreceptor reflex response, the angiotensin subtype receptors involved, and the role of Fos protein in this process, using Sprague-Dawley rats anesthetized with pentobarbital sodium. Microinjection bilaterally of angiotensin (Ang ) II (5, 10, 20, or 40 pmol) into the nucleus tractus solitarii significantly suppressed the spontaneous baroreceptor reflex, as represented by the magnitude of transfer function between systemic arterial pressure and heart rate signals. There also was a concomitant increase in Fos-like immunoreactivity in the nucleus tractus solitarii. Both the suppression of spontaneous baroreceptor reflex and Fos expression in nucleus tractus solitarii neurons elicited by Ang II were discernibly attenuated by pretreatment with or comicroinjection into the bilateral nucleus tractus solitarii of a 15-mer antisense c-fos oligonucleotide that targets against the initiation codon of c-fos mRNA. In addition, those 2 actions of Ang II were reversed by the coadministration of the nonpeptide Ang II type 1 (AT(1)) receptor antagonist losartan (1.6 nmol) but not by the nonpeptide AT(2) receptor antagonist PD 123,319 (1.6 nmol). Control treatments with artificial cerebrospinal fluid, sense cDNA, or antisense oligonucleotide with a scrambled sequence were ineffective. We conclude that under minimal cardiovascular perturbation, Fos expression mediated via activation of AT(1) subtype receptors may underlie the inhibitory modulation of beat-to-beat baroreflex control of blood pressure by Ang II at the nucleus tractus solitarii.
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Affiliation(s)
- S H Luoh
- Kuang Wu Institute of Technology, Taipei, Republic of China
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Evans RG, Ventura S, Dampney RA, Ludbrook J. Neural mechanisms in the cardiovascular responses to acute central hypovolaemia. Clin Exp Pharmacol Physiol 2001; 28:479-87. [PMID: 11428384 DOI: 10.1046/j.1440-1681.2001.03473.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The haemodynamic response to acute central hypovolaemia consists of two phases. During phase I, arterial pressure is well maintained in the face of falling cardiac output (CO) by baroreceptor-mediated reflex vasoconstriction and cardio-acceleration. Phase II commences once CO has fallen to a critical level of 50-60% of its resting value, equivalent to loss of approximately 30% of blood volume. 2. During phase II, sympathetic vasoconstrictor and cardiac drive fall abruptly and cardiac vagal drive increases. In humans, this response is invariably associated with fainting and has been termed vasovagal syncope. 3. In both experimental animals and in humans, the responses to acute central hypovolaemia are greatly affected by anaesthetic agents, in that the compensatory responses during phase I (e.g. halothane) or their failure during phase II (e.g. alfentanil) are blunted or abolished. 4. Therefore, our present knowledge of the neurochemical basis of the response to hypovolaemia depends chiefly on the results of experiments in conscious animals. Use of techniques for simulating haemorrhage has greatly enhanced this research effort, by allowing the effects of multiple treatments on the response to acute central hypovolaemia to be tested in the same animal. 5. The results of such experiments indicate that phase II of the response to hypovolaemia is triggered, at least in part, by a signal from cardiac vagal afferents. There is also strong evidence that phase II depends on brainstem delta-opioid receptor and nitrergic mechanisms and can potentially be modulated by circulating or neuronally released adrenocorticotropic hormone, brainstem serotonergic pathways operating through 5-HT1A receptors and opioids acting through mu- and kappa-opioid receptors in the brainstem. 6. Phase II also appears to require input from supramedullary brain centres. Future studies should determine how these neurotransmitter systems interact and their precise neuroanatomical arrangements.
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Affiliation(s)
- R G Evans
- Department of Physiology, Monash University, Clayton, Victoria, Australia.
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