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Collister JP, Fritcher N, Nahey D. Role of the median preoptic nucleus in the development of chronic deoxycorticosterone acetate (DOCA)-salt hypertension. Physiol Rep 2024; 12:e16046. [PMID: 38749925 PMCID: PMC11096131 DOI: 10.14814/phy2.16046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 04/18/2024] [Accepted: 04/28/2024] [Indexed: 05/18/2024] Open
Abstract
We have previously reported that the subfornical organ (SFO) does not contribute to the chronic hypertensive response to DOCA-salt in rats, and yet the organum vasculosum of the lamina terminalis (OVLT) plays a significant role in the development of deoxycorticosterone acetate (DOCA)-salt hypertension. Since efferent fibers of the OVLT project to and through the median preoptic nucleus (MnPO), the present study was designed to test the hypothesis that the MnPO is necessary for DOCA-salt hypertension in the rat. Male Sprague-Dawley rats underwent SHAM (MnPOsham; n = 5) or electrolytic lesion of the MnPO (MnPOx; n = 7) followed by subsequent unilateral nephrectomy and telemetry instrumentation. After recovery and during the experimental protocol, rats consumed a 0.1% NaCl diet and 0.9% NaCl drinking solution. Mean arterial pressure (MAP) was recorded telemetrically 5 days before and 21 days after DOCA implantation (100 mg/rat; SQ). The chronic pressor response to DOCA was attenuated in MnPOx rats by Day 11 of treatment and continued such that MAP increased 25 ± 3 mmHg in MnPOsham rats by Day 21 of DOCA compared to 14 ± 3 mmHg in MnPOx rats. These results support the hypothesis that the MnPO is an important brain site of action and necessary for the full development of DOCA-salt hypertension in the rat.
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Affiliation(s)
- John P. Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary MedicineUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Nora Fritcher
- Department of Veterinary and Biomedical Sciences, College of Veterinary MedicineUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - David Nahey
- Department of Veterinary and Biomedical Sciences, College of Veterinary MedicineUniversity of MinnesotaSt. PaulMinnesotaUSA
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Collister JP, Ployngam T, Ariza‐Guzman PA, Osborn JW. Neurons of the median preoptic nucleus contribute to chronic angiotensin II-salt induced hypertension in the rat. Physiol Rep 2022; 10:e15551. [PMID: 36564179 PMCID: PMC9788964 DOI: 10.14814/phy2.15551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 12/06/2022] [Accepted: 12/08/2022] [Indexed: 06/17/2023] Open
Abstract
Experiments were designed to test the hypothesis that median preoptic (MnPO) neurons are necessary for the full hypertensive response to chronic angiotensin II (AngII) in rats consuming a high salt diet. The MnPO is implicated in many of the physiologic actions of AngII, primarily acting as a downstream nucleus to AngII binding at circumventricular organs such as the organum vasculosum of the lamina terminalis (OVLT). We have previously shown a prominent effect of lesion of the OVLT on the chronic hypertensive effects of AngII in rats consuming high salt. Additionally, we have shown that lesion of the MnPO attenuated the hypertensive response to chronic intravenous infusion of AngII in rats. However, whether MnPO neurons or fibers of passage contribute to this response is not clear. Male Sprague Dawley rats were randomly assigned to either sham (SHAM; n = 8) or ibotenic acid lesion of the MnPO (MnPOx; n = 6). In the MnPOx group, 200 nl of ibotenic acid in phosphate buffer saline (5 μg/μl) was injected into each of 3 predetermined coordinates targeted at the entire MnPO. After a week of recovery, rats were instrumented with radiotelemetric pressure transducers, provided 2.0% NaCl diet and distilled water ad libitum and given another week to recover. After 3 days of baseline measurements, osmotic minipumps were implanted subcutaneously in all rats for administration of AngII at a rate of 150 ng/kg/min. Blood pressure measurements were made for 14 days after minipump implantation. By day 7 of AngII treatment, blood pressure responses appeared to plateau in both groups while the hypertensive response was markedly attenuated in MnPOx rats (MnPOx, 122 ± 6 mmHg; SHAM, 143 ± 8 mmHg). These results support the hypothesis that neurons of the MnPO are involved in the central pathway mediating the chronic hypertensive effects of AngII in rats consuming a high salt diet.
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Affiliation(s)
- John P. Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary MedicineUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Trasida Ployngam
- Department of Veterinary and Biomedical Sciences, College of Veterinary MedicineUniversity of MinnesotaSt. PaulMinnesotaUSA
| | - Pilar A. Ariza‐Guzman
- Department of Integrative Biology and PhysiologyUniversity of MinnesotaMinneapolisMinnesotaUSA
| | - John W. Osborn
- Department of SurgeryUniversity of MinnesotaMinneapolisMinnesotaUSA
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An Angiotensin-Responsive Connection from the Lamina Terminalis to the Paraventricular Nucleus of the Hypothalamus Evokes Vasopressin Secretion to Increase Blood Pressure in Mice. J Neurosci 2020; 41:1429-1442. [PMID: 33328294 DOI: 10.1523/jneurosci.1600-20.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/29/2020] [Accepted: 12/03/2020] [Indexed: 12/22/2022] Open
Abstract
Blood pressure is controlled by endocrine, autonomic, and behavioral responses that maintain blood volume and perfusion pressure at levels optimal for survival. Although it is clear that central angiotensin type 1a receptors (AT1aR; encoded by the Agtr1a gene) influence these processes, the neuronal circuits mediating these effects are incompletely understood. The present studies characterize the structure and function of AT1aR neurons in the lamina terminalis (containing the median preoptic nucleus and organum vasculosum of the lamina terminalis), thereby evaluating their roles in blood pressure control. Using male Agtr1a-Cre mice, neuroanatomical studies reveal that AT1aR neurons in the area are largely glutamatergic and send projections to the paraventricular nucleus of the hypothalamus (PVN) that appear to synapse onto vasopressin-synthesizing neurons. To evaluate the functionality of these lamina terminalis AT1aR neurons, we virally delivered light-sensitive opsins and then optogenetically excited or inhibited the neurons while evaluating cardiovascular parameters or fluid intake. Optogenetic excitation robustly elevated blood pressure, water intake, and sodium intake, while optogenetic inhibition produced the opposite effects. Intriguingly, optogenetic excitation of these AT1aR neurons of the lamina terminalis also resulted in Fos induction in vasopressin neurons within the PVN and supraoptic nucleus. Further, within the PVN, selective optogenetic stimulation of afferents that arise from these lamina terminalis AT1aR neurons induced glutamate release onto magnocellular neurons and was sufficient to increase blood pressure. These cardiovascular effects were attenuated by systemic pretreatment with a vasopressin-1a-receptor antagonist. Collectively, these data indicate that excitation of lamina terminalis AT1aR neurons induces neuroendocrine and behavioral responses that increase blood pressure.SIGNIFICANCE STATEMENT Hypertension is a widespread health problem and risk factor for cardiovascular disease. Although treatments exist, a substantial percentage of patients suffer from "drug-resistant" hypertension, a condition associated with increased activation of brain angiotensin receptors, enhanced sympathetic nervous system activity, and elevated vasopressin levels. The present study highlights a role for angiotensin Type 1a receptor expressing neurons located within the lamina terminalis in regulating endocrine and behavioral responses that are involved in maintaining cardiovascular homeostasis. More specifically, data presented here reveal functional excitatory connections between angiotensin-sensitive neurons in the lamina terminals and vasopressin neurons in the paraventricular nucleus of the hypothalamus, and further indicate that activation of this circuit raises blood pressure. These neurons may be a promising target for antihypertensive therapeutics.
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Marciante AB, Wang LA, Little JT, Cunningham JT. Caspase lesions of PVN-projecting MnPO neurons block the sustained component of CIH-induced hypertension in adult male rats. Am J Physiol Heart Circ Physiol 2020; 318:H34-H48. [PMID: 31675258 PMCID: PMC6985804 DOI: 10.1152/ajpheart.00350.2019] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 10/31/2019] [Accepted: 10/31/2019] [Indexed: 02/07/2023]
Abstract
Obstructive sleep apnea is characterized by interrupted breathing that leads to cardiovascular sequelae including chronic hypertension that can persist into the waking hours. Chronic intermittent hypoxia (CIH), which models the hypoxemia associated with sleep apnea, is sufficient to cause a sustained increase in blood pressure that involves the central nervous system. The median preoptic nucleus (MnPO) is an integrative forebrain region that contributes to blood pressure regulation and neurogenic hypertension. The MnPO projects to the paraventricular nucleus (PVN), a preautonomic region. We hypothesized that pathway-specific lesions of the projection from the MnPO to the PVN would attenuate the sustained component of chronic intermittent hypoxia-induced hypertension. Adult male Sprague-Dawley rats (250-300 g) were anesthetized with isoflurane and stereotaxically injected bilaterally in the PVN with a retrograde Cre-containing adeno-associated virus (AAV; AAV9.CMV.HI.eGFP-Cre.WPRE.SV40) and injected in the MnPO with caspase-3 (AAV5-flex-taCasp3-TEVp) or control virus (AAV5-hSyn-DIO-mCherry). Three weeks after the injections the rats were exposed to a 7-day intermittent hypoxia protocol. During chronic intermittent hypoxia, controls developed a diurnal hypertension that was blunted in rats with caspase lesions. Brain tissue processed for FosB immunohistochemistry showed decreased staining with caspase-induced lesions of MnPO and downstream autonomic-regulating nuclei. Chronic intermittent hypoxia significantly increased plasma levels of advanced oxidative protein products in controls, but this increase was blocked in caspase-lesioned rats. The results indicate that PVN-projecting MnPO neurons play a significant role in blood pressure regulation in the development of persistent chronic intermittent hypoxia hypertension.NEW & NOTEWORTHY Chronic intermittent hypoxia associated with obstructive sleep apnea increases oxidative stress and leads to chronic hypertension. Sustained hypertension may be mediated by angiotensin II-induced neural plasticity of excitatory median preoptic neurons in the forebrain that project to the paraventricular nucleus of the hypothalamus. Selective caspase lesions of these neurons interrupt the drive for sustained hypertension and cause a reduction in circulating oxidative protein products. This indicates that a functional connection between the forebrain and hypothalamus is necessary to drive diurnal hypertension associated with intermittent hypoxia. These results provide new information about central mechanisms that may contribute to neurogenic hypertension.
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Affiliation(s)
- Alexandria B Marciante
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - Lei A Wang
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - Joel T Little
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas
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Interaction of central angiotensin II and aldosterone on sodium intake and blood pressure. Brain Res 2019; 1720:146299. [DOI: 10.1016/j.brainres.2019.06.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 06/12/2019] [Accepted: 06/15/2019] [Indexed: 12/25/2022]
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Marciante AB, Wang LA, Farmer GE, Cunningham JT. Selectively Inhibiting the Median Preoptic Nucleus Attenuates Angiotensin II and Hyperosmotic-Induced Drinking Behavior and Vasopressin Release in Adult Male Rats. eNeuro 2019; 6:ENEURO.0473-18.2019. [PMID: 30923740 PMCID: PMC6437658 DOI: 10.1523/eneuro.0473-18.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/29/2019] [Accepted: 02/26/2019] [Indexed: 01/12/2023] Open
Abstract
The median preoptic nucleus (MnPO) is a putative integrative region that contributes to body fluid balance. Activation of the MnPO can influence thirst, but it is not clear how these responses are linked to body fluid homeostasis. We used designer receptors exclusively activated by designer drugs (DREADDs) to determine the role of the MnPO in drinking behavior and vasopressin release in response to peripheral angiotensin II (ANG II) or 3% hypertonic saline (3% HTN) in adult male Sprague Dawley rats (250-300 g). Rats were anesthetized with isoflurane and stereotaxically injected with an inhibitory DREADD (rAAV5-CaMKIIa-hM4D(Gi)-mCherry) or control (rAAV5-CaMKIIa-mCherry) virus in the MnPO. After two weeks' recovery, a subset of rats was used for extracellular recordings to verify functional effects of ANG II or hyperosmotic challenges in MnPO slice preparations. Remaining rats were used in drinking behavior studies. Each rat was administered either 10 mg/kg of exogenous clozapine-N-oxide (CNO) to inhibit DREADD-expressing cells or vehicle intraperitoneal followed by a test treatment with either 2-mg/kg ANG II or 3% HTN (1 ml/100-g bw, s.c.), twice per week for two separate treatment weeks. CNO-induced inhibition during either test treatment significantly attenuated drinking responses compared to vehicle treatments and controls. Brain tissue processed for cFos immunohistochemistry showed decreased expression with CNO-induced inhibition during either test treatment in the MnPO and downstream nuclei compared to controls. CNO-mediated inhibition significantly attenuated treatment-induced increases in plasma vasopressin compared to controls. The results indicate inhibition of CaMKIIa-expressing MnPO neurons significantly reduces drinking and vasopressin release in response to ANG II or hyperosmotic challenge.
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Affiliation(s)
- Alexandria B Marciante
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Lei A Wang
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - George E Farmer
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107
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Collister JP, Nahey DB, Hartson R, Wiedmeyer CE, Banek CT, Osborn JW. Lesion of the OVLT markedly attenuates chronic DOCA-salt hypertension in rats. Am J Physiol Regul Integr Comp Physiol 2018; 315:R568-R575. [PMID: 29897819 PMCID: PMC6172631 DOI: 10.1152/ajpregu.00433.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 06/12/2018] [Accepted: 06/12/2018] [Indexed: 11/22/2022]
Abstract
Lesions of the anteroventral third ventricle (AV3V region) are known to prevent many forms of experimental hypertension, including mineralocorticoid [deoxycorticosterone acetate (DOCA)-salt] hypertension in the rat. However, AV3V lesions include the organum vasculosum of the lamina terminalis (OVLT), portions of the median preoptic nucleus, and efferent fibers from the subfornical organ (SFO), thereby limiting the ability to define the individual contribution of these structures to the prevention of experimental hypertension. Having previously reported that the SFO does not play a significant role in the development of DOCA-salt hypertension, the present study was designed to test the hypothesis that the OVLT is necessary for DOCA-salt hypertension in the rat. In uninephrectomized OVLT-lesioned (OVLTx; n = 6) and sham-operated ( n = 4) Sprague-Dawley rats consuming a 0.1% NaCl diet and 0.9% NaCl drinking solution, 24-h mean arterial pressure (MAP) was recorded telemetrically 5 days before and 21 days after DOCA implantation (100 mg sc per rat). No differences in control MAP were observed between groups. The chronic pressor response to DOCA was attenuated in OVLTx rats such that MAP increased to 133 ± 3 mmHg in sham-operated rats by day 21 of DOCA compared with 120 ± 4 mmHg (means ± SE) in OVLTx rats. These results support the hypothesis that the OVLT is an important brain site of action for the pathogenesis of DOCA-salt hypertension in the rat.
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Affiliation(s)
- John P Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota , St. Paul, Minnesota
| | - David B Nahey
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota , St. Paul, Minnesota
| | - Rochelle Hartson
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota , St. Paul, Minnesota
| | - Charles E Wiedmeyer
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri , Columbia, Missouri
| | - Christopher T Banek
- Department of Integrative Biology and Physiology, University of Minnesota Medical School , Minneapolis, Minnesota
| | - John W Osborn
- Department of Integrative Biology and Physiology, University of Minnesota Medical School , Minneapolis, Minnesota
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Collister JP, Taylor-Smith H, Drebes D, Nahey D, Tian J, Zimmerman MC. Angiotensin II-Induced Hypertension Is Attenuated by Overexpressing Copper/Zinc Superoxide Dismutase in the Brain Organum Vasculosum of the Lamina Terminalis. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:3959087. [PMID: 26881025 PMCID: PMC4736576 DOI: 10.1155/2016/3959087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/30/2015] [Indexed: 11/23/2022]
Abstract
Angiotensin II (AngII) can access the brain via circumventricular organs (CVOs), including the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT), to modulate blood pressure. Previous studies have demonstrated a role for both the SFO and OVLT in the hypertensive response to chronic AngII, yet it is unclear which intracellular signaling pathways are involved in this response. Overexpression of copper/zinc superoxide dismutase (CuZnSOD) in the SFO has been shown to attenuate the chronic hypertensive effects of AngII. Presently, we tested the hypothesis that elevated levels of superoxide (O2 (∙-)) in the OVLT contribute to the hypertensive effects of AngII. To facilitate overexpression of superoxide dismutase, adenoviral vectors encoding human CuZnSOD or control adenovirus (AdEmpty) were injected directly into the OVLT of rats. Following 3 days of control saline infusion, rats were intravenously infused with AngII (10 ng/kg/min) for ten days. Blood pressure increased 33 ± 8 mmHg in AdEmpty rats (n = 6), while rats overexpressing CuZnSOD (n = 8) in the OVLT demonstrated a blood pressure increase of only 18 ± 5 mmHg after 10 days of AngII infusion. These results support the hypothesis that overproduction of O2 (∙-) in the OVLT plays an important role in the development of chronic AngII-dependent hypertension.
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Affiliation(s)
- John P. Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
| | - Heather Taylor-Smith
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
| | - Donna Drebes
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
| | - David Nahey
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
| | - Jun Tian
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Matthew C. Zimmerman
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA
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Mittelman-Smith MA, Krajewski-Hall SJ, McMullen NT, Rance NE. Neurokinin 3 Receptor-Expressing Neurons in the Median Preoptic Nucleus Modulate Heat-Dissipation Effectors in the Female Rat. Endocrinology 2015; 156:2552-62. [PMID: 25825817 PMCID: PMC4475724 DOI: 10.1210/en.2014-1974] [Citation(s) in RCA: 30] [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: 12/31/2022]
Abstract
KNDy neurons facilitate tail skin vasodilation and modulate the effects of estradiol on thermoregulation. We hypothesize that KNDy neurons influence cutaneous vasodilation via projections to neurons in the median preoptic nucleus (MnPO) that express the neurokinin 3 receptor (NK3R). In support of this hypothesis, focal microinjections of senktide, an NK3R agonist, into the MnPO lowers core temperature (TCORE) in the female rat. To further study the role of MnPO NK3R neurons in thermoregulation, these neurons were specifically ablated using a conjugate of a selective NK3R agonist and saporin (NK3-SAP). NK3-SAP or blank-SAP (control) was injected into the MnPO/medial septum. Tail skin temperature (TSKIN) and TCORE were measured in ovariectomized rats exposed to 3 ambient temperatures (TAMBIENT) before and after estradiol-17β (E2) treatment. Before killing, we injected senktide (sc), monitored TCORE for 70 minutes, and harvested brains for Fos immunohistochemistry. Ablation of MnPO NK3R neurons lowered TSKIN at neutral and subneutral TAMBIENT regardless of E2 treatment. However, ablation did not prevent the effects of E2 on TCORE and TSKIN. In control rats, senktide injections induced hypothermia with numerous Fos-immunoreactive cells in the MnPO. In contrast, in NK3-SAP rats, senktide did not alter TCORE and minimal Fos-immunoreactive neurons were identified in the MnPO. These data show that NK3R neurons in the MnPO are required for the hypothermic effects of senktide but not for the E2 modulation of thermoregulation. The lower TSKIN in NK3-SAP-injected rats suggests that MnPO NK3R neurons, like KNDy neurons, facilitate cutaneous vasodilation, an important heat-dissipation effector.
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Affiliation(s)
- Melinda A Mittelman-Smith
- Departments of Pathology (M.A.M.-S., S.J.K.-H., N.E.R.), Cellular and Molecular Medicine (N.T.M., N.E.R.), and Neurology (N.E.R.), and the Evelyn F. McKnight Brain Institute (N.E.R.), University of Arizona College of Medicine, Tucson, Arizona 85724
| | - Sally J Krajewski-Hall
- Departments of Pathology (M.A.M.-S., S.J.K.-H., N.E.R.), Cellular and Molecular Medicine (N.T.M., N.E.R.), and Neurology (N.E.R.), and the Evelyn F. McKnight Brain Institute (N.E.R.), University of Arizona College of Medicine, Tucson, Arizona 85724
| | - Nathaniel T McMullen
- Departments of Pathology (M.A.M.-S., S.J.K.-H., N.E.R.), Cellular and Molecular Medicine (N.T.M., N.E.R.), and Neurology (N.E.R.), and the Evelyn F. McKnight Brain Institute (N.E.R.), University of Arizona College of Medicine, Tucson, Arizona 85724
| | - Naomi E Rance
- Departments of Pathology (M.A.M.-S., S.J.K.-H., N.E.R.), Cellular and Molecular Medicine (N.T.M., N.E.R.), and Neurology (N.E.R.), and the Evelyn F. McKnight Brain Institute (N.E.R.), University of Arizona College of Medicine, Tucson, Arizona 85724
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Over-expression of copper/zinc superoxide dismutase in the median preoptic nucleus attenuates chronic angiotensin II-induced hypertension in the rat. Int J Mol Sci 2014; 15:22203-13. [PMID: 25474089 PMCID: PMC4284703 DOI: 10.3390/ijms151222203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 11/17/2014] [Accepted: 11/26/2014] [Indexed: 11/28/2022] Open
Abstract
The brain senses circulating levels of angiotensin II (AngII) via circumventricular organs, such as the subfornical organ (SFO), and is thought to adjust sympathetic nervous system output accordingly via this neuro-hormonal communication. However, the cellular signaling mechanisms involved in these communications remain to be fully understood. Previous lesion studies of either the SFO, or the downstream median preoptic nucleus (MnPO) have shown a diminution of the hypertensive effects of chronic AngII, without providing a clear explanation as to the intracellular signaling pathway(s) involved. Additional studies have reported that over-expressing copper/zinc superoxide dismutase (CuZnSOD), an intracellular superoxide (O2·−) scavenging enzyme, in the SFO attenuates chronic AngII-induced hypertension. Herein, we tested the hypothesis that overproduction of O2·− in the MnPO is an underlying mechanism in the long-term hypertensive effects of chronic AngII. Adenoviral vectors encoding human CuZnSOD (AdCuZnSOD) or control vector (AdEmpty) were injected directly into the MnPO of rats implanted with aortic telemetric transmitters for recording of arterial pressure. After a 3 day control period of saline infusion, rats were intravenously infused with AngII (10 ng/kg/min) for ten days. Rats over-expressing CuZnSOD (n = 7) in the MnPO had a blood pressure increase of only 6 ± 2 mmHg after ten days of AngII infusion while blood pressure increased 21 ± 4 mmHg in AdEmpty-infected rats (n = 9). These results support the hypothesis that production of O2·− in the MnPO contributes to the development of chronic AngII-dependent hypertension.
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de Lima Silveira L, da Silva EF, de Andrade AM, Xavier CH, Freiria-Oliveira AH, Colugnati DB, de Castro CH, Colombari E, Pedrino GR. Involvement of the median preoptic nucleus in blood pressure control. Neurosci Lett 2014; 558:91-6. [DOI: 10.1016/j.neulet.2013.11.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/22/2013] [Accepted: 11/01/2013] [Indexed: 02/07/2023]
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Pedrino GR, Calderon AS, Andrade MA, Cravo SL, Toney GM. Discharge of RVLM vasomotor neurons is not increased in anesthetized angiotensin II-salt hypertensive rats. Am J Physiol Heart Circ Physiol 2013; 305:H1781-9. [PMID: 24124187 DOI: 10.1152/ajpheart.00657.2013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurons of the rostral ventrolateral medulla (RVLM) are critical for generating and regulating sympathetic nerve activity (SNA). Systemic administration of ANG II combined with a high-salt diet induces hypertension that is postulated to involve elevated SNA. However, a functional role for RVLM vasomotor neurons in ANG II-salt hypertension has not been established. Here we tested the hypothesis that RVLM vasomotor neurons have exaggerated resting discharge in rats with ANG II-salt hypertension. Rats in the hypertensive (HT) group consumed a high-salt (2% NaCl) diet and received an infusion of ANG II (150 ng·kg(-1)·min(-1) sc) for 14 days. Rats in the normotensive (NT) group consumed a normal salt (0.4% NaCl) diet and were infused with normal saline. Telemetric recordings in conscious rats revealed that mean arterial pressure (MAP) was significantly increased in HT compared with NT rats (P < 0.001). Under anesthesia (urethane/chloralose), MAP remained elevated in HT compared with NT rats (P < 0.01). Extracellular single unit recordings in HT (n = 28) and NT (n = 22) rats revealed that barosensitive RVLM neurons in both groups (HT, 23 cells; NT, 34 cells) had similar cardiac rhythmicity and resting discharge. However, a greater (P < 0.01) increase of MAP was needed to silence discharge of neurons in HT (17 cells, 44 ± 5 mmHg) than in NT (28 cells, 29 ± 3 mmHg) rats. Maximum firing rates during arterial baroreceptor unloading were similar across groups. We conclude that heightened resting discharge of sympathoexcitatory RVLM neurons is not required for maintenance of neurogenic ANG II-salt hypertension.
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Affiliation(s)
- Gustavo R Pedrino
- Department of Physiological Science, Universidade Federal de Goiás, Goiânia, Brazil
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Collister JP, Olson MK, Nahey DB, Vieira AA, Osborn JW. OVLT lesion decreases basal arterial pressure and the chronic hypertensive response to AngII in rats on a high-salt diet. Physiol Rep 2013; 1:e00128. [PMID: 24303192 PMCID: PMC3841056 DOI: 10.1002/phy2.128] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 09/20/2013] [Accepted: 09/25/2013] [Indexed: 01/06/2023] Open
Abstract
We have reported that lesion of the organum vasculosum of the lamina terminalis (OVLT) has no effect on basal levels of mean arterial pressure (MAP) but abolishes the hypertensive effects of angiotensin II (AngII) in rats consuming a normal-salt diet. These results suggest that the OVLT does not contribute to regulation of MAP under conditions of normal salt intake, but it is an important brain site for the hypertensive actions of AngII. The OVLT has been proposed as a major sodium sensor in the brain and the hypertensive effects of AngII are exacerbated by high-salt intake. Therefore, the objective of this study was to investigate the role of the OVLT during AngII-induced hypertension in rats fed a high-salt diet. Male Sprague-Dawley rats underwent sham (Sham; n = 9) or OVLT lesion (OVLTx; n = 8) surgery and were placed on a high-salt (2% NaCl) diet. MAP was measured by radio telemetry during three control days, 10 days of AngII infusion (10 ng/kg/min, i.v.), and a 3-day recovery period. MAP was significantly lower in OVLTx (97 ± 2 mmHg) compared to Sham (106 ± 1 mmHg) rats during the control period (P < 0.05). Moreover, the chronic pressor response to AngII was markedly attenuated in OVLTx rats. MAP increased 58 ± 3 mmHg in Sham rats by Day 10 of AngII compared to a 40 ± 7 mmHg increase in OVLTx rats (P < 0.05). We conclude that (1) the OVLT regulates the basal levels of MAP in rats consuming a high-salt and (2) the OVLT is an important brain site of action for the pathogenesis of AngII-salt hypertension in the rat. Supported by HL076312.
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Affiliation(s)
- John P Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota St. Paul, MN
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Role of the Median Preoptic Nucleus in Arterial Pressure Regulation and Sodium and Water Homeostasis during High Dietary Salt Intake. NEUROPHYSIOLOGY+ 2012; 44:363-375. [PMID: 32724266 DOI: 10.1007/s11062-012-9307-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Changes in the osmolality and level of angiotensin II (ANG II) are important peripheral signals modulating appropriate central sympathetic output and maintaining a normal arterial pressure during high salt intake. The median preoptic nucleus (MnPO) receives reciprocal inputs from the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT), the circumventricular organs that have been shown to be necessary in multiple central effects of changes in the osmolality and circulating ANG II directed toward the maintenance of sodium and water homeostasis. We, therefore, hypothesized that the MnPO is a crucial part of the central neuronal mechanisms mediating the blood pressure control by altered osmolality and/or ANG II signaling during chronic high dietary salt intake. Male Sprague-Dawley rats were randomly assigned to either sham (operation), or electrolytic lesion of the MnPO. After a 7-day recovery, rats were instrumented with radiotelemetric transducers and aortic flow probes for the measurement of the mean arterial pressure + heart rate (HR) and cardiac output (CO), respectively. Femoral venous catheters were also implanted to collect blood for the measurements of plasma osmolality and sodium concentration, as well as plasma renin activity. Rats were given another 10 days to recover and then were subjected to a 28-day-long study protocol that included a 7-day control period (1.0% NaCl diet), followed by 14 days of high salt (4.0% NaCl), and a 7-day recovery period (1.0% NaCl). The data showed, that despite a slight increase in the MAP observed in both MnPO- (n = 12) and sham-lesioned (n = 8) rats during the high-salt period, there were no significant differences between the MAP, HR, and CO in the two groups throughout the study protocol. These findings do not support the hypothesis that the MnPO is necessary to maintain normal blood pressure during high dietary salt intake. However, MnPO-lesioned rats showed less sodium balance than sham-lesioned rats during the first 4 days of high salt intake. Although, these results may be explained partly by the plasma hyperosmolarity and hypernatremia observed in MnPO-lesioned rats; they also shed light on the role of the MnPO in central neuronal control of renal sodium handling during chronic high dietary salt intake.
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Cunningham JT, Knight WD, Mifflin SW, Nestler EJ. An Essential role for DeltaFosB in the median preoptic nucleus in the sustained hypertensive effects of chronic intermittent hypoxia. Hypertension 2012; 60:179-87. [PMID: 22689746 PMCID: PMC3415378 DOI: 10.1161/hypertensionaha.112.193789] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
One of the main clinical features of obstructive sleep apnea is sustained hypertension and elevated sympathetic activity during waking hours. Chronic intermittent hypoxia (CIH), animal model of the hypoxemia associated with obstructive sleep apnea, produces a similar sustained increase in blood pressure. This study determined the role of ΔFosB in the median preoptic nucleus (MnPO) in the sustained increase in mean arterial pressure associated with CIH. Rats were injected in the MnPO with viral vectors that expressed green fluorescent protein alone or green fluorescent protein plus a dominant-negative construct that inhibits the transcriptional effects of ΔFosB. In green fluorescent protein-injected rats and uninjected controls, 7-day exposure to CIH increased mean arterial pressure by 7 to 10 mm Hg during both intermittent hypoxia exposure and normoxia. Dominant-negative inhibition of MnPO ΔFosB did not affect changes in mean arterial pressure during intermittent hypoxia exposure but significantly reduced the sustained component of the blood pressure response to CIH during the normoxic dark phase. Inhibition of MnPO ΔFosB reduced the FosB/ΔFosB staining in the paraventricular nucleus and rostral ventrolateral medulla but not the nucleus of the solitary tract. PCR array analysis identified 6 activator protein 1-regulated genes expressed in the MnPO that were increased by CIH exposure, ace, ace2, nos1, nos3, prdx2, and map3k3. Dominant-negative inhibition of ΔFosB in the MnPO blocked increased expression of each of these genes in rats exposed to CIH except for Prdx2. ΔFosB may mediate transcriptional activity in MnPO necessary for sustained CIH hypertension, suggesting that neural adaptations may contribute to diurnal hypertension in obstructive sleep apnea.
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Affiliation(s)
- J Thomas Cunningham
- Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA.
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16
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Osborn JW, Hendel MD, Collister JP, Ariza-Guzman PA, Fink GD. The role of the subfornical organ in angiotensin II-salt hypertension in the rat. Exp Physiol 2012; 97:80-8. [PMID: 21967900 PMCID: PMC3253211 DOI: 10.1113/expphysiol.2011.060491] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hypertension caused by chronic infusion of angiotensin II (Ang II) in experimental animals is dependent, in part, on increased activity of the sympathetic nervous system. This chronic sympathoexcitatory response is amplified by a high-salt diet, suggesting an interaction of circulating Ang II and dietary salt on sympathetic regulatory pathways in the brain. The present study tested the hypothesis that the subfornical organ (SFO), a forebrain circumventricular organ known to be activated by circulating Ang II, is crucial to the pathogenesis of hypertension induced by chronic Ang II administration in rats on a high-salt diet (Ang II-salt model). Rats were randomly selected to undergo either subfornical organ lesion (SFOx) or sham surgery (Sham) and then placed on a high-salt (2% NaCl) diet. One week later, rats were instrumented for radiotelemetric measurement of mean arterial pressure (MAP) and heart rate (HR) and placed in metabolic cages to measure sodium and water balance. Baseline MAP was slightly (but not statistically) lower in SFOx compared with Sham rats during the 5 day control period. During the subsequent 10 days of Ang II administration, MAP was statistically lower in SFOx rats. However, when MAP responses to Ang II were analysed by comparing the change from the 5 day baseline period, only on the fifth day of Ang II was MAP significantly different between groups. There were no differences between groups for water or sodium balance throughout the protocol. We conclude that, although the SFO is required for the complete expression of Ang II-salt hypertension in the rat, other brain sites are also involved.
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Affiliation(s)
- John W Osborn
- Department of Integrative Biology and Physiology, University of Minnesota, Room 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
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Meehan J, Collister JP. Lesion of the Subfornical Organ attenuates Neuronal Activation of the Paraventricular Nucleus in response to Angiotensin II in normal rats. OPEN JOURNAL OF NEUROSCIENCE 2011; 1:1. [PMID: 24795816 PMCID: PMC4008144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
INTRODUCTION/HYPOTHESIS The subfornical organ, one of the central circumventricular organs, has been shown to mediate many of the effects of circulating angiotensin II (AngII). Where these signals are processed downstream is not fully understood. The SFO does indeed project to prominent cardiovascular regulatory centers such as the paraventricular nucleus (PVN), of whose neurons are activated by central AngII. We reasoned that AngII sensed at the SFO would cause neuronal activation at downstream hypothalamic areas such as the median preoptic nucleus and paraventricular nucleus, and as such would be diminished in animals with lesions of the SFO. MATERIALS AND METHODS To test this hypothesis, groups of rats underwent either SFO lesion (SFOx) or sham operation. Five days later rats were instrumented with radiotelemetry transducers for monitoring of mean arterial pressure (MAP) and venous catheters for infusions. MAP and heart rate were measured continuously. After a 4 day control period, infusion of AngII (0.575 µg/kg/min) was begun for a period of 2 hours. Rats were then sacrificed and brains were processed for neuronal Fos expression. RESULTS AngII produced Fos expression in the SFO, MnPO and PVN of sham rats. Fos expression was greatly attenuated in the PVN of SFOx rats. CONCLUSION These results support our hypothesis, suggesting that AngII sensitive neurons of the SFO can mediate neuronal activation in the PVN.
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Affiliation(s)
- Jessica Meehan
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108
| | - John P Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108
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Knight WD, Little JT, Carreno FR, Toney GM, Mifflin SW, Cunningham JT. Chronic intermittent hypoxia increases blood pressure and expression of FosB/DeltaFosB in central autonomic regions. Am J Physiol Regul Integr Comp Physiol 2011; 301:R131-9. [PMID: 21543638 PMCID: PMC3129875 DOI: 10.1152/ajpregu.00830.2010] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 04/26/2011] [Indexed: 11/22/2022]
Abstract
Chronic intermittent hypoxia (CIH) models repetitive bouts of arterial hypoxemia that occur in humans suffering from obstructive sleep apnea. CIH has been linked to persistent activation of arterial chemoreceptors and the renin-angiotensin system, which have been linked to chronic elevations of sympathetic nerve activity (SNA) and mean arterial pressure (MAP). Because Fos and FosB are transcription factors involved in activator protein (AP)-1 driven central nervous system neuronal adaptations, this study determined if CIH causes increased Fos or FosB staining in brain regions that regulate SNA and autonomic function. Male Sprague Dawley rats were instrumented with telemetry transmitters for continuous recording of MAP and heart rate (HR). Rats were exposed to continuous normoxia (CON) or to CIH for 8 h/day for 7 days. CIH increased MAP by 7-10 mmHg without persistently affecting HR. A separate group of rats was killed 1 day after 7 days of CIH for immunohistochemistry. CIH did not increase Fos staining in any brain region examined. Staining for FosB/ΔFosB was increased in the organum vasculosum of the lamina terminalis (CON: 9 ± 1; CIH: 34 ± 3 cells/section), subfornical organ (CON: 7 ± 2; CIH: 31 ± 3), median preoptic nucleus (CON 15 ± 1; CIH: 38 ± 3), nucleus of the solitary tract (CON: 9 ± 2; CIH: 28 ± 4), A5 (CON: 3 ± 1; CIH: 10 ± 1), and rostral ventrolateral medulla (CON: 5 ± 1; CIH: 17 ± 2). In the paraventricular nucleus, FosB/ΔFosB staining was located mainly in the dorsal and medial parvocellular subnuclei. CIH did not increase FosB/ΔFosB staining in caudal ventrolateral medulla or supraoptic nucleus. These data indicate that CIH induces an increase in FosB/ΔFosB in autonomic nuclei and suggest that AP-1 transcriptional regulation may contribute to stable adaptive changes that support chronically elevated SNA.
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Affiliation(s)
- W David Knight
- Department of Integrative Physiology and the Cardiovascular Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107, USA
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Vieira AA, Nahey DB, Collister JP. Role of the organum vasculosum of the lamina terminalis for the chronic cardiovascular effects produced by endogenous and exogenous ANG II in conscious rats. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1564-71. [DOI: 10.1152/ajpregu.00034.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endogenous and exogenous circulating ANG II acts at one of the central circumventricular organs (CVOs), the subfornical organ (SFO), to modulate chronic blood pressure regulation. However, at the forebrain, another important CVO is the organum vasculosum of the lamina terminalis (OVLT). In the present study, we tested the hypothesis that the OVLT mediates the hypertension or the hypotension produced by chronic infusion of ANG II or losartan (AT1 antagonist), respectively. Six days after sham or OVLT electrolytic lesion, male Sprague-Dawley rats (280–320 g, n = 6 per group) were instrumented with intravenous catheters and radiotelemetric blood pressure transducers. Following another week of recovery, rats were given 3 days of saline control infusion (7 ml/day) and were then infused with ANG II (10 ng·kg−1·min−1) or losartan (10 mg·kg−1·day−1) for 10 days, followed by 3 recovery days. Twenty-four hour average measurements of mean arterial pressure (MAP) and heart rate (HR) were made during this protocol. Hydromineral balance (HB) responses were measured during the experimental protocol. By day 9 of ANG II treatment, MAP had increased 16 ± 4 mmHg in sham rats but only 4 ± 1 mmHg in OVLT lesioned rats without changes in HR or HB. However, the hypotension produced by 10 days of losartan infusion was not modified in OVLT lesioned rats. These results suggest that the OVLT might play an important role during elevation of plasma ANG II, facilitating increases of blood pressure but is not involved with baseline effects of endogenous ANG II.
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Affiliation(s)
- Alexandre A. Vieira
- Department of Veterinary and Biomedical Science, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota
| | - David B. Nahey
- Department of Veterinary and Biomedical Science, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota
| | - John P. Collister
- Department of Veterinary and Biomedical Science, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota
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Northcott CA, Watts S, Chen Y, Morris M, Chen A, Haywood JR. Adenoviral inhibition of AT1a receptors in the paraventricular nucleus inhibits acute increases in mean arterial blood pressure in the rat. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1202-11. [DOI: 10.1152/ajpregu.00764.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Brain and peripheral renin-angiotensin systems are important in blood pressure maintenance. Circulating ANG II stimulates brain RAS to contribute to the increase mean arterial pressure (MAP). This mechanism has not been fully clarified, so it was hypothesized that reducing angiotensin type 1a (AT1a) receptors (AT1aRs) in the paraventricular nucleus (PVN) would diminish intravenous ANG II-induced increases in MAP. Adenoviruses (Ad) encoding AT1a small hairpin RNA (shRNA) or Ad-LacZ (marker gene) were injected into the PVN [1 × 109 plaque-forming units/ml, bilateral (200 nl/site)] of male Sprague-Dawley rats instrumented with radiotelemetry transmitters for MAP and heart rate measurements and with venous catheters for drug administration. No differences in weight gain or basal MAP were observed. ANG II (30 ng·kg−1·min−1 iv, 15 μl/min for 60 min) was administered 3, 7, 10, and 14 days after PVN Ad injection to increase blood pressure. ANG II-induced elevations in MAP were significantly reduced in PVN Ad-AT1a shRNA rats compared with Ad-LacZ rats (32 ± 6 vs. 8 ± 9 mmHg at 7 days, 35 ± 6 vs. 10 ± 6 mmHg at 10 days, and 32 ± 2 vs. 1 ± 5 mmHg at 14 days; P < 0.05). These observations were confirmed by acute administration of losartan (20 nmol/l, 100 nl/site) in the PVN prior to short-term infusion of ANG II; the ANG II-pressor response was attenuated by 69%. In contrast, PVN Ad-AT1a shRNA treatment did not influence phenylephrine-induced increases in blood pressure (30 μg·kg−1·min−1 iv, 15 μl/min for 30 min). Importantly, PVN Ad-AT1a shRNA did not alter superior mesenteric arterial contractility to ANG II or norepinephrine; ACh-induced arterial relaxation was also unaltered. β-Galactosidase staining revealed PVN Ad transduction, and Western blot analyses revealed significant reductions of PVN AT1 protein. In conclusion, PVN-localized AT1Rs are critical for short-term circulating ANG II-mediated elevations of blood pressure. A sustained suppression of AT1aR expression by single administration of shRNA can interfere with short-term actions of ANG II.
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Affiliation(s)
- Carrie A. Northcott
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Stephanie Watts
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Yanfang Chen
- Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio; and
| | - Mariana Morris
- Department of Pharmacology and Toxicology, Wright State University Boonshoft School of Medicine, Dayton, Ohio; and
| | - Alex Chen
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Joseph R. Haywood
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
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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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Collister JP, Nahey DB. Simultaneous administration of Ang(1-7) or A-779 does not affect the chronic hypertensive effects of angiotensin II in normal rats. J Renin Angiotensin Aldosterone Syst 2010; 11:99-102. [DOI: 10.1177/1470320309359928] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hypothesis. The following studies were designed to test the hypothesis that simultaneous administration of either Ang(1-7) or its antagonist A-779 would affect the chronic hypertensive effects of angiotensin II (Ang II). Introduction. Despite the well-described actions of Ang(1-7) and its role possessing opposite actions to Ang II, there have been few studies examining the role of Ang(1-7) in a chronic setting. It is well established that Ang(1-7) plays a protective role in preventing deleterious effects of Ang II in the heart, but little is known of its role in modulating the chronic hypertensive effects of Ang II. Materials and methods. Rats were instrumented with venous catheters and telemetric pressure transducers. Arterial pressure responses were measured in rats treated with Ang II (10 ng/kg/ min) (n=9) and compared with those treated with Ang II and Ang(1-7) (24 µg/kg/h) (n=8), or the Ang(1-7) antagonist A-779 (24 µg/kg/h) (n=7) for 8 days. Results. Mean arterial pressure rose significantly and similarly in all three groups of rats, such that by day 8 of Ang II infusion, pressures had risen 25—30 mmHg in all rats. Conclusions. These results do not support the hypothesis that the chronic hypertensive effects of Ang II in normal rats are altered by co-administration of either Ang(1-7) or A-779.
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Affiliation(s)
- John P Collister
- Department of Veterinary & Biomedical Sciences, University of Minnesota, St. Paul, MN 55108, USA,
| | - David B Nahey
- Department of Veterinary & Biomedical Sciences, University of Minnesota, St. Paul, MN 55108, USA
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Daniels D, Mietlicki EG, Nowak EL, Fluharty SJ. Angiotensin II stimulates water and NaCl intake through separate cell signalling pathways in rats. Exp Physiol 2009; 94:130-7. [PMID: 18723579 PMCID: PMC2855186 DOI: 10.1113/expphysiol.2008.044446] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Angiotensin II (AngII) stimulation of water and NaCl intake is a classic model of the behavioural effects of hormones. In vitro studies indicate that the AngII type 1 (AT(1)) receptor stimulates intracellular pathways that include protein kinase C (PKC) and mitogen-activated protein (MAP) kinase activation. Previous studies support the hypotheses that PKC is involved in AngII-induced water, but not NaCl intake and that MAP kinase plays a role in NaCl consumption, but not water intake, after injection of AngII. The present experiments test these hypotheses in rats using central injections of AngII in the presence or absence of a PKC inhibitor or a MAP kinase inhibitor. Pretreatment with the PKC inhibitor chelerythrine attenuated AngII-induced water intake, but NaCl intake was unaffected. In contrast, pretreatment with U0126, a MAP kinase inhibitor, had no effect on AngII-induced water intake, but attenuated NaCl intake. These data support the working hypotheses and significantly extend our earlier findings and those of others. Perhaps more importantly, these experiments demonstrate the remarkable diversity of peptide receptor systems and add support for the surprising finding that intracellular signalling pathways can have divergent behavioural relevance.
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Affiliation(s)
- Derek Daniels
- Behavioral Neuroscience Program, Department of Psychology, University at Buffalo, SUNY, Buffalo, NY 14260, USA.
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Ployngam T, Collister JP. Role of the median preoptic nucleus in chronic angiotensin II-induced hypertension. Brain Res 2008; 1238:75-84. [DOI: 10.1016/j.brainres.2008.08.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 07/28/2008] [Accepted: 08/04/2008] [Indexed: 02/05/2023]
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