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Lee YH, Tsai MC, Li TL, Dai YWE, Huang SC, Hwang LL. Spontaneously hypertensive rats have more orexin neurons in the hypothalamus and enhanced orexinergic input and orexin 2 receptor-associated nitric oxide signalling in the rostral ventrolateral medulla. Exp Physiol 2015; 100:993-1007. [PMID: 26096870 DOI: 10.1113/ep085016] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 06/17/2015] [Indexed: 01/24/2023]
Abstract
NEW FINDINGS What is the central question of this study? Our previous study demonstrates that elevated orexin 2 receptor (OX2R) activity within the rostral ventrolateral medulla (RVLM) contributes to hypertension in spontaneously hypertensive rats (SHRs), and a lower OX2R protein level was detected in their RVLM. The present study aims to explore the mechanisms underlying elevated orexinergic activity in the RVLM of SHRs, compared with their normotensive counterparts, Wistar-Kyoto rats. What is the main finding and its importance? Increased orexinergic input into the RVLM and enhanced OX2R responsiveness in the RVLM, which was mainly mediated by augmented OX2R-neuronal nitric oxide synthase signalling, may underlie the elevated OX2R activity within the RVLM of SHRs. Our previous study showed that elevated orexin 2 receptor (OX2R) activity within the rostral ventrolateral medulla (RVLM) contributes to hypertension in spontaneously hypertensive rats (SHRs). Herein, we investigated the mechanism(s) underlying the elevated OX2R activity. The following results were found. (i) More hypothalamic orexin A-immunoreactive (OXA-IR) cells existed in SHRs than in Wistar-Kyoto (WKY) rats at either 4 (2217 ± 43 versus 1809 ± 69) or 16 weeks of age (1829 ± 59 versus 1230 ± 84). The number of OXA-IR cells that project to the RVLM was higher in 16-week-old SHRs than in WKY rats (91 ± 11 versus 52 ± 11). (ii) Higher numbers of OXA-IR and RVLM-projecting OXA-IR cells were found in the dorsomedial and perifornical hypothalamus of 16-week-old SHRs. (iii) Spontaneously hypertensive rats had higher levels of orexin A and B in the hypothalamus and higher levels of orexin A in the RVLM than did WKY rats. (iv) Unilateral intra-RVLM application of OX2R agonist, orexin A or [Ala(11), d-Leu(15)]-orexin B (50 pmol) induced a larger pressor response in SHRs than in WKY rats. (v) Intra-RVLM pretreatment with a neuronal nitric oxide synthase (NOS) inhibitor, 7-nitro-indazole (2.5 pmol), or a soluble guanylate cyclase inhibitor, methylene blue (250 pmol), reduced the intra-RVLM [Ala(11), d-Leu(15) ]-orexin B-induced pressor response in both WKY rats and SHRs. In contrast, an inducible NOS inhibitor, aminoguanidine (100 pmol), was ineffective. (vi) Neuronal NOS was co-expressed with OX2R in RVLM neurons. In conclusion, increased orexinergic input and enhanced OX2R-neuronal NOS signalling may underlie elevated OX2R activity in the RVLM and contribute to the pathophysiology of hypertension in SHRs.
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Affiliation(s)
- Yen-Hsien Lee
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Min-Chien Tsai
- Department of Physiology and Biophysics, Graduate Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | - Tzu-Ling Li
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Yu-Wen E Dai
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Shang-Cheng Huang
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Ling-Ling Hwang
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.,Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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Zhang-James Y, DasBanerjee T, Sagvolden T, Middleton FA, Faraone SV. SLC9A9 mutations, gene expression, and protein-protein interactions in rat models of attention-deficit/hyperactivity disorder. Am J Med Genet B Neuropsychiatr Genet 2011; 156B:835-43. [PMID: 21858920 PMCID: PMC3168688 DOI: 10.1002/ajmg.b.31229] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Accepted: 07/22/2011] [Indexed: 01/07/2023]
Abstract
SLC9A9 (solute carrier family 9, member 9, also known as Na+/H+ exchanger member (NHE9)) is a membrane protein that regulates the luminal pH of the recycling endosome, an essential organelle for synaptic transmission and plasticity. SLC9A9 has been implicated in human attention deficit hyperactivity disorder (ADHD) and in rat studies of hyperactivity. We examined the SLC9A9 gene sequence and expression profile in prefrontal cortex, dorsal striatum and hippocampus in two genetic rat models of ADHD. We report two mutations in a rat model of inattentive ADHD, the WKY/NCrl rat, which affect the interaction of SLC9A9 with calcineurin homologous protein (CHP). We observed an age-dependent abnormal expression of SLC9A9 in brains of this inattentive model and in the Spontaneous Hypertensive Rat (SHR) model of ADHD. Our data suggest a novel mechanism whereby SLC9A9 sequence variants and abnormalities in gene expression could contribute to the ADHD-like symptoms of rat models and possibly the pathophysiology of ADHD in humans.
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Affiliation(s)
- Yanli Zhang-James
- Department of Psychiatry, SUNY Upstate Medical University, Syracuse, NY, 13210
| | - Tania DasBanerjee
- Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY, 13210
| | - Terje Sagvolden
- Department of Physiology, University of Oslo, NO-0317 Oslo, Norway
| | - Frank A. Middleton
- Department of Psychiatry, SUNY Upstate Medical University, Syracuse, NY, 13210,Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY, 13210
| | - Stephen V Faraone
- Department of Psychiatry, SUNY Upstate Medical University, Syracuse, NY, 13210,Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY, 13210
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Spary EJ, Maqbool A, Saha S, Batten TFC. Increased GABA B receptor subtype expression in the nucleus of the solitary tract of the spontaneously hypertensive rat. J Mol Neurosci 2008; 35:211-24. [PMID: 18338268 DOI: 10.1007/s12031-008-9055-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 02/14/2008] [Indexed: 02/07/2023]
Abstract
Expression of GABA(B) receptor messenger RNA (mRNA) in the central nervous system was compared between the spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rat. Polymerase chain reaction (PCR) revealed all the isoforms except B1e in cortex, hypothalamus, and medulla oblongata. In the nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM), the B1a-c and 1 g isoforms were present as well as B2. Real-time PCR detected significantly higher levels of B1a (p < 0.01) and B2 (p < 0.05) mRNA in the NTS of SHR compared to WKY. A significant increase in B1a expression (p < 0.05) was detected in VLM. Immunolabeling suggested presynaptic and postsynaptic expression of B1a, B1b, and B2 subtypes throughout the NTS, with significant differences in distribution patterns and labeling between subtypes and between SHR and WKY. These findings suggest that GABA(B) receptors expressed by neurones in NTS may be involved in cardiovascular regulation and that changes in GABA(B) mRNA expression levels may contribute to the hypertensive state in SHR.
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Affiliation(s)
- Emma J Spary
- Division of Cardiovascular and Neuronal Remodelling, LIGHT Institute, Faculty of Medicine & Health, University of Leeds, Worsley Building, Leeds, LS2 9JT, UK.
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Corbett EKA, Mary DASG, McWilliam PN, Batten TFC. Age-related loss of cardiac vagal preganglionic neurones in spontaneously hypertensive rats. Exp Physiol 2007; 92:1005-13. [PMID: 17644704 DOI: 10.1113/expphysiol.2007.038216] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Despite the findings that impaired vagal control of the heart rate occurs in human hypertension, leading to greater cardiovascular risk, the mechanism of this impairment is as yet unknown. Observations in humans and experiments in the spontaneously hypertensive rat (SHR) suggested that such impairment may be related to an anomaly in central vagal neurones. We therefore set out to determine whether the numbers and distribution of cardiac-projecting vagal preganglionic neurones in the medulla of adult (12 week) hypertensive SHR are different from those in young (4 week) prehypertensive SHR and in age-matched Wistar-Kyoto (WKY) rats of two age groups. The number of vagal neurones, identified by labelling with the fluorescent tracer DiI applied to the heart, was essentially similar in the three areas of the medulla analysed (dorsal vagal nucleus, nucleus ambiguus and intermediate reticular zone) in young SHR and young or adult WKY rats. In contrast, fewer vagal neurones were labelled in adult SHR compared with young SHR or WKY rats. This difference was due to highly significant reductions in vagal neurones in the dorsal vagal nucleus and nucleus ambiguus on the right side of the medulla. These observations suggest that a loss of parasympathetic preganglionic neurones supplying the heart with axons in the right vagus nerve, or a remodelling of their cardiac projections, may explain the known impairment of the baroreceptor reflex gain controlling heart rate in hypertension.
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Affiliation(s)
- Eric K A Corbett
- Institute for Cardiovascular Research (CRISTAL), Worsley Building, Clarendon Way, University of Leeds, Leeds LS2 9JT, UK
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Saha S, Spary EJ, Maqbool A, Asipu A, Corbett EKA, Batten TFC. Increased expression of AMPA receptor subunits in the nucleus of the solitary tract in the spontaneously hypertensive rat. ACTA ACUST UNITED AC 2004; 121:37-49. [PMID: 14969735 DOI: 10.1016/j.molbrainres.2003.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2003] [Indexed: 01/21/2023]
Abstract
The expression of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunits GluR1-4 in the nucleus of the solitary tract (NTS) of adult Wistar rats was examined by polymerase chain reaction (PCR), and the neuronal localisation of these receptor subunits in the NTS were confirmed by immunohistochemistry using subunit-specific antibodies. Semi-quantitative PCR was used to investigate differences in AMPA receptor subunit expression between spontaneously hypertensive rats (SH) and age-matched normotensive Wistar Kyoto rats (WKY). All four receptor subunits were expressed in both strains, but compared to WKY, total AMPA receptor and the GluR3 mRNA expressions were significantly higher in SH. No differences were detected in cDNA form the cerebral cortex or cerebellum. Immunolabelling for GluRs 1, 2 and 2/3 in the neuropil relative to neuronal somata in the cardioregulatory areas of the NTS appeared to be increased in SH, with an overall increase in the density of GluR2/3 labelling in the medial and commissural NTS of SH. These results indicate a possible role for changes in AMPA receptor subunit expression in NTS neurones, involving an increase in GluR3 associated with development of hypertension in SH.
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Affiliation(s)
- Sikha Saha
- School of Medicine, University of Leeds, Leeds LS2 9JT, UK
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McLean KJ, Jarrott B, Lawrence AJ. Neuropeptide Y gene expression and receptor autoradiography in hypertensive and normotensive rat brain. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1996; 35:249-59. [PMID: 8717361 DOI: 10.1016/0169-328x(95)00219-i] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Neurones containing neuropeptide Y (NPY) may participate in central cardiovascular control by tonically influencing barosensitive neurones within the nucleus tractus solitarius. The present study has employed both in situ hybridisation histochemistry and receptor autoradiography, to visualise the expression of prepro-NPY mRNA in the forebrain and to determine the NPY receptor subtype(s) in the brainstem, respectively. Prepro-NPY gene expression was visualised in the hypothalamus, cortex, dentate gyrus and lateral reticular thalamus from age-matched spontaneously hypertensive rats (SHR) and normotensive Don Ryu rats (DRY) and Wistar Kyoto rats (WKY). Quantitative densitometry revealed an increase in the NPY transcript in the arcuate nucleus of SHR rats compared to their normotensive counterparts. Autoradiography using [125I]Bolton-Hunter-NPY (BH-NPY, 15 pM) demonstrated NPY binding sites in the area postrema, the commissural nucleus tractus solitarius (cNTS) and the inferior olivary complex. NPY (1 microM) and peptide YY (1 microM), but not [Leu31,Pro34]NPY (10-100 nM), fully inhibited the binding of [125I]BH-NPY. These results indicate that NPY receptors of the Y2 subtype predominate in the dorsal vagal complex. Unilateral nodose ganglionectomy resulted in a partial loss of NPY binding sites in the commissural NTS, but not the area postrema, suggesting that a proportion of binding sites (Y2 subtype) are present on central vagal terminals. While all three rat strains appear to have the same relative proportions of NPY receptor subtypes in the brainstem, the relevance of the differential NPY gene expression in the arcuate nucleus regarding central cardiovascular control mechanisms and/or the pathogenesis of hypertension remains to be elucidated.
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Affiliation(s)
- K J McLean
- Department of Pharmacology, Monash University, Clayton, Vic., Australia
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