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Saunders SL, Hutchinson DS, Britton FC, Liu L, Markus I, Sandow SL, Murphy TV. Effect of β 1 /β 2 -adrenoceptor blockade on β 3 -adrenoceptor activity in the rat cremaster muscle artery. Br J Pharmacol 2021; 178:1789-1804. [PMID: 33506492 DOI: 10.1111/bph.15398] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/19/2021] [Accepted: 01/19/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The physiological role of vascular β3 -adrenoceptors is not fully understood. Recent evidence suggests cardiac β3 -adrenoceptors are functionally effective after down-regulation of β1 /β2 -adrenoceptors. The functional interaction between the β3 -adrenoceptor and other β-adrenoceptor subtypes in rat striated muscle arteries was investigated. EXPERIMENTAL APPROACH Studies were performed in cremaster muscle arteries isolated from male Sprague-Dawley rats. β-adrenoceptor expression was assessed through RT-PCR and immunofluorescence. Functional effects of β3 -adrenoceptor agonists and antagonists and other β-adrenoceptor ligands were measured using pressure myography. KEY RESULTS All three β-adrenoceptor subtypes were present in the endothelium of the cremaster muscle artery. The β3 -adrenoceptor agonists mirabegron and CL 316,243 had no effect on the diameter of pressurized (70 mmHg) cremaster muscle arterioles with myogenic tone, while the β3 -adrenoceptor agonist SR 58611A and the nonselective β-adrenoceptor agonist isoprenaline caused concentration-dependent dilation. In the presence of β1/2 -adrenoceptor antagonists nadolol (10 μM), atenolol (1 μM) and ICI 118,551 (0.1 μM) both mirabegron and CL 316,243 were effective in causing vasodilation and the potency of SR 58611A was enhanced, while responses to isoprenaline were inhibited. The β3 -adrenoceptor antagonist L 748,337 (1 μM) inhibited vasodilation caused by β3 -adrenoceptor agonists (in the presence of β1/2 -adrenoceptor blockade), but L 748,337 had no effect on isoprenaline-induced vasodilation. CONCLUSION AND IMPLICATIONS All three β-adrenoceptor subtypes were present in the endothelium of the rat cremaster muscle artery, but β3 -adrenoceptor mediated vasodilation was only evident after blockade of β1/2 -adrenoceptors. This suggests constitutive β1/2 -adrenoceptor activity inhibits β3 -adrenoceptor function in the endothelium of skeletal muscle resistance arteries.
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Affiliation(s)
- Samantha L Saunders
- Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Dana S Hutchinson
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Fiona C Britton
- Department of Biomedical Sciences, School of Dental Medicine, University of Nevada, Las Vegas, Las Vegas, Nevada, USA
| | - Lu Liu
- Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Irit Markus
- Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Shaun L Sandow
- Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.,Biomedical Science, School of Health and Sports Science, University of the Sunshine Coast, Maroochydore, Queensland, Australia
| | - Timothy V Murphy
- Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
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Borghi F, Silva C, da Silva PC, Ferrucci DL, Morais CL, Conceição-Vertamatti AG, Carvalho HF, Fonseca MDC, Vieira AS, Grassi-Kassisse DM. The influence of hypertensive environment on adipose tissue remodeling measured by fluorescence lifetime imaging in spontaneously hypertensive rats. Mol Cell Endocrinol 2020; 506:110758. [PMID: 32057944 DOI: 10.1016/j.mce.2020.110758] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/10/2020] [Accepted: 02/10/2020] [Indexed: 12/20/2022]
Abstract
There is a lack of information correlating low adiposity with hypertension experienced by Spontaneous Hypertensive Rats (SHR) or overweight and normotension in Wistar-Kyoto (WKY). We aimed to investigate this lipodystrophy phenomenon by measuring fluorescence lifetime (FLIM), optical redox ratio (ORR), serum levels of hypothalamic-pituitary-adrenal (HPA) and/or hypothalamic-pituitary-thyroid (HPT) hormones axes between Wistar, WKY and SHR before and after establishment of hypertension. Under high blood pressure, we evaluated serum adipokines. Brown adipose tissue was characterized as lower ORR and shorter FLIM compared to white adipose tissue. HPT axis showed a crucial role in the SHR adipose tissue configuration by attenuating whitening. The increased adiposity in WKY may act as a preventive agent for hypertension, since SHR, with low adiposity, establishes the disease. The hypertensive environment can highlight key adipokines that may result in new therapeutic approaches to the treatment of adiposity dysfunctions and hypertension.
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Affiliation(s)
- Filipy Borghi
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Carolina Silva
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Priscila Cristina da Silva
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Danilo Lopes Ferrucci
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Camila Lidiane Morais
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Ana Gabriela Conceição-Vertamatti
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Hernandes Faustino Carvalho
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Matheus de Castro Fonseca
- Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970, Campinas, Sao Paulo, Brazil
| | - André Schwambach Vieira
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil
| | - Dora Maria Grassi-Kassisse
- LABEEST, Laboratory of Stress Study, Department of Structural and Functional Biology, Institute of Biology, University of Campinas, UNICAMP, 13083-862, Campinas, SP, Brazil.
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Berg T. Kv7(KCNQ)-K +-Channels Influence Total Peripheral Resistance in Female but Not Male Rats, and Hamper Catecholamine Release in Hypertensive Rats of Both Sexes. Front Physiol 2018. [PMID: 29515459 PMCID: PMC5826282 DOI: 10.3389/fphys.2018.00117] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
K+-channels of the Kv7/KCNQ-family hyperpolarize and stabilize excitable cells such as autonomic neurons and vascular smooth muscle cells (VSMC). Kv7 may therefore play a role in blood pressure (BP) homeostasis, and prevent a high total peripheral vascular resistance (TPR), a hallmark of hypertensive disease. The present study analyzed if Kv7 channels influence catecholamine release and TPR in normotensive (WKY) and spontaneously hypertensive rats (SHR), and if they may contribute to the antihypertensive protection seen in young, female SHR. Tyramine-stimulated norepinephrine release evokes an adrenergic cardiovascular response, and also allows modulation of release to be reflected in the overflow to plasma. The experiment itself activated some secretion of epinephrine. The results show: (1) XE-991 (Kv7.1-7.4-inhibitor), but not chromanol 293B (Kv7.1-inhibitor), increased tyramine-stimulated norepinephrine overflow and epinephrine secretion in both sexes in SHR, but not WKY. (2) Surprisingly, the Kv7-openers retigabine (Kv7.2-7.5) and ICA-27243 (Kv7.2-7.3-preferring) increased catecholamine release in female SHR. (3) The rise in TPR following tyramine-stimulated norepinephrine release was increased by XE-991 but not chromanol in the female WKY only. (4) Retigabine and ICA-27243 reduced the TPR-response to tyramine in the female SHR only. These results suggested: (1) Up-regulation of Kv7.2-7.3 function in sympathetic neurons and chromaffin cells hampered catecholamine release in SHR of both sexes. (2) The increase catecholamine release observed after channel openers in the female SHR may possibly involve reduced transmission in cholinergic neurons which hamper catecholamine release. These two mechanisms may serve to counter-act the hyperadrenergic state in SHR. (3) Kv7.4, most likely in the vasculature, opposed the tension-response to norepinephrine in the female WKY. (4) Vascular Kv7.4-7.5 could be stimulated and then opposed norepinephrine-induced vasoconstriction in the female SHR. (5) Vascular Kv7 channels did not counter-act norepinephrine induced vasoconstriction in male rats, possibly due to different Kv7 channel regulation. Kv7 channels may represent a novel target for antihypertensive therapy.
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Affiliation(s)
- Torill Berg
- Division of Physiology, Department of Molecular Medicine, Institute for Basic Medical Sciences, University of Oslo, Oslo, Norway
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Berg T. β- and α 2-Adrenoceptor Control of Vascular Tension and Catecholamine Release in Female Normotensive and Spontaneously Hypertensive Rats. Front Neurol 2017; 8:130. [PMID: 28424658 PMCID: PMC5380753 DOI: 10.3389/fneur.2017.00130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 03/20/2017] [Indexed: 11/26/2022] Open
Abstract
As in humans, young, female, spontaneously hypertensive rats (SHR) have a lower blood pressure than male SHR. In male, normotensive rats (WKY), α2- and β1+2-adrenoceptors (AR) reciprocally controlled catecholamine release and vascular smooth muscle tension. This interaction was malfunctioning in male SHR. The present study analyzed if a favorable shift in the α2/β1+2AR interaction may represent an antihypertensive protection in females. Female SHR (early hypertension, 12–14 weeks) and age-matched WKY were infused with tyramine (15 min) to stimulate norepinephrine (NE) release through the reuptake transporter, consequently preventing reuptake. Presynaptic control of vesicular release was therefore reflected as differences in overflow to plasma. The released NE increased total peripheral vascular resistance (TPR). The results showed that β1>2AR facilitated tyramine-stimulated NE release in both strains, also in the presence of α2AR-antagonist (L-659,066). βAR-antagonist (atenolol-β1, ICI-118551-β2, nadolol-β1+2) had no effect on the increased secretion of epinephrine after L-659,066 in WKY, but β1>2AR-antagonist augmented the L-659,066-induced increase in the secretion of epinephrine in SHR. Nadolol increased the TPR response to tyramine with a greater effect in WKY than SHR, whereas β1or2-selective antagonists did not. One βAR-subtype may therefore substitute for the other. When both β1+2AR were blocked, α2AR-antagonist still reduced the TPR response in WKY but not SHR. Thus, α2/β1+2AR reciprocally controlled catecholamine release, with a particular negative β1AR-influence on α2AR-auto-inhibition of epinephrine secretion in SHR. Moreover, in these female rats, β1/2AR-independent α2AR-mediated vasoconstriction was seen in WKY but not SHR, but β1/2AR-mediated vasodilation downregulated adrenergic vasoconstriction, not only in WKY but also in SHR.
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Affiliation(s)
- Torill Berg
- Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Chang N, Li Y, Zhou M, Gao J, Hou Y, Jiang M, Bai G. The hemostatic effect study of Cirsium setosum on regulating α1-ARs via mediating norepinephrine synthesis by enzyme catalysis. Biomed Pharmacother 2017; 87:698-704. [PMID: 28088737 DOI: 10.1016/j.biopha.2017.01.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/29/2016] [Accepted: 01/03/2017] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Cirsium setosum (CS) is the aboveground part of Cephalanoplos segetum Kitam. Although it has been used as a hemostatic treatment for thousands of years and is still in use today, the mechanism of CS on regulating ARs is still not clear. PURPOSE In this study, we aimed to clarify the mechanism of CS on regulating ARs. METHODS We developed a simple method based on UPLC/Q-TOF MS combined adrenergic receptor dual-luciferase reporter assay systems for the rapid determination of active constituents in CS. The mechanism of tyramine, the main active component for regulating ARs, was further investigated by an in vitro norepinephrine biotransformation test and in vivo vaso activity tests. RESULTS Two phenethylamine ARs regulators (tyramine and N-methyltyramine) in CS were characterized, and it was found that tyramine could induce vasoconstriction via regulation of α1-ARs by mediating norepinephrine synthesis. CONCLUSION The hemostatic effect of CS is associated with tyramine and N-methyltyramine, via regulation of α1-ARs, and the mechanism of tyramine is related to mediating norepinephrine synthesis by enzyme catalysis.
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Affiliation(s)
- Nianwei Chang
- Tianjin University of Traditional Chinese Medicine, Tianjin 300193, People's Republic of China
| | - Yanmei Li
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China
| | - Mengge Zhou
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China
| | - Jie Gao
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China
| | - Yuanyuan Hou
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China
| | - Min Jiang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China.
| | - Gang Bai
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, People's Republic of China.
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Montaudon E, Dubreil L, Lalanne V, Jagu B, Toumaniantz G, Thorin C, Henrion D, Desfontis JC, Martignat L, Mallem MY. Effects of long-term active immunization with the second extracellular loop of human β 1- or β 3-adrenoceptors in thoracic aorta and mesenteric arteries in Lewis rats. Vascul Pharmacol 2016; 87:129-138. [PMID: 27620808 DOI: 10.1016/j.vph.2016.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Revised: 08/18/2016] [Accepted: 09/05/2016] [Indexed: 10/21/2022]
Abstract
OBJECTIVE To evaluate whether active immunization producing β1- or β3-antibodies (β1-ABs and β3-ABs) detected in sera of patients with dilated cardiomyopathies has deleterious effects on vascular reactivity in Lewis rat thoracic aorta (TA) and small mesenteric arteries (SMA). DESIGN AND METHOD Lewis rats were immunized for 6months with peptidic sequences corresponding to the second extracellular loop of β1- and β3-adrenoceptors (ARs). During the immunization, systolic blood pressure (SBP) was monitored using the tail cuff method. The vascular reactivity of immunized rats was assessed by ex vivo studies on SMA and TA using various β-AR agonists, phenylephrine and KCl. RESULTS The immunizations producing functional β1-ABs and β3-ABs did not affect the SBP. However, in TA from β1-AR-immunized rats, the relaxations mediated by dobutamine and salbutamol were significantly impaired in comparison with adjuvant rats whereas nebivolol-induced relaxation was not modified. Moreover, phenylephrine and KCl-mediated contractions were enhanced in these rats. In contrast, immunization with β3-AR peptide led to the increase of relaxations induced by dobutamine in TA but did not change those induced by salbutamol and nebivolol. Surprisingly, in SMA from both rats immunized with β1- or β3-peptides, relaxations induced by the various β-agonists were not changed whereas phenylephrine and KCl-mediated contractions were impaired. CONCLUSIONS Our study shows that β1- and β3-ABs can affect vascular reactivity. β1-ABs would have a pathogenic action whereas β3-ABs would have a beneficial effect on aorta reactivity.
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Affiliation(s)
- E Montaudon
- LUNAM University, Oniris, UPSP 5304 of Animal Pathophysiology and Functional Pharmacology, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France
| | - L Dubreil
- LUNAM University, Oniris, INRA UMR U703, PanTHER, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France
| | - V Lalanne
- LUNAM University, Oniris, UPSP 5304 of Animal Pathophysiology and Functional Pharmacology, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France
| | - B Jagu
- LUNAM University, INSERM, UMR 1087/CNRS 6291 Institut du Thorax, F44007 Nantes, France
| | - G Toumaniantz
- LUNAM University, INSERM, UMR 1087/CNRS 6291 Institut du Thorax, F44007 Nantes, France
| | - C Thorin
- LUNAM University, Oniris, UPSP 5304 of Animal Pathophysiology and Functional Pharmacology, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France
| | - D Henrion
- LUNAM University, CNRS UMR 6214, INSERM U1083, F-49000 Angers, France
| | - J-C Desfontis
- LUNAM University, Oniris, UPSP 5304 of Animal Pathophysiology and Functional Pharmacology, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France
| | - L Martignat
- LUNAM Univsersity, Oniris, UPSP, Sanitary Safety in Biotechnologies of the Reproduction, La Chantrerie, BP 40706, 44307 Nantes, France
| | - M Y Mallem
- LUNAM University, Oniris, UPSP 5304 of Animal Pathophysiology and Functional Pharmacology, Atlanpôle La Chantrerie, BP 40706, 44307 Nantes, France.
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Berg T. α2-Adrenoreceptor Constraint of Catecholamine Release and Blood Pressure Is Enhanced in Female Spontaneously Hypertensive Rats. Front Neurosci 2016; 10:130. [PMID: 27065790 PMCID: PMC4812064 DOI: 10.3389/fnins.2016.00130] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Accepted: 03/15/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED α2-adrenoceptors (α2AR) lower central sympathetic output and peripheral catecholamine release, and may therefore prevent sympathetic hyperactivity and hypertension. The α2AR are dysfunctional in male spontaneously hypertensive rats (SHR). Premenopausal females are less hypertensive than males. The purpose of this study was to test if this difference could be explained by functional α2AR in the female SHR. A 15-min tyramine-infusion was used to stimulate norepinephrine release through the re-uptake transporter, consequently preventing re-uptake. Presynaptic control of vesicular release will therefore be reflected as differences in overflow to plasma. The surgical trauma activates secretion of epinephrine, also subjected to α2AR auto-inhibition. Blood pressure was monitored through a femoral artery catheter and cardiac output by ascending aorta flow in 12-14 weeks-old (early hypertension) SHR and normotensive rats (WKY). Total peripheral vascular resistance (TPR) was calculated. Female SHR, unlike male, were close to normotensive. Pre-treatment with none-selective (clonidine) or non-A-selective (ST-91) α2AR agonist reduced, and none-selective α2AR antagonist (L-659,066) increased tyramine-induced norepinephrine overflow in female WKY and SHR. L-659,066 also increased secretion of epinephrine. The L-659,066-induced increase in catecholamine release was further enhanced by additional pre-treatment with ST-91 or angiotensin AT1 receptor antagonist (losartan) in SHR only. L-659,066 eliminated the tyramine-induced rise in TPR in both strains in female rats. CONCLUSION α2AR-mediated control of catecholamine release and vascular tension was therefore functional in female SHR, unlike that previously observed in male SHR. Functional α2AR is likely to have a protective function and may explain the lack of hypertension in the young female SHR.
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Affiliation(s)
- Torill Berg
- Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo Oslo, Norway
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Berg T. Voltage-Sensitive K(+) Channels Inhibit Parasympathetic Ganglion Transmission and Vagal Control of Heart Rate in Hypertensive Rats. Front Neurol 2015; 6:260. [PMID: 26696959 PMCID: PMC4672051 DOI: 10.3389/fneur.2015.00260] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Accepted: 11/25/2015] [Indexed: 01/19/2023] Open
Abstract
Parasympathetic withdrawal plays an important role in the autonomic dysfunctions in hypertension. Since hyperpolarizing, voltage-sensitive K+ channels (KV) hamper transmitter release, elevated KV-activity may explain the disturbed vagal control of heart rate (HR) in hypertension. Here, the KV inhibitor 3,4-diaminopyridine was used to demonstrate the impact of KV on autonomic HR control. Cardiac output and HR were recorded by a flow probe on the ascending aorta in anesthetized, normotensive (WKY), and spontaneously hypertensive rats (SHR), and blood pressure by a femoral artery catheter. 3,4-diaminopyridine induced an initial bradycardia, which was greater in SHR than in WKY, followed by sustained tachycardia in both strains. The initial bradycardia was eliminated by acetylcholine synthesis inhibitor (hemicholinium-3) and nicotinic receptor antagonist/ganglion blocker (hexamethonium), and reversed to tachycardia by muscarinic receptor (mAchR) antagonist (atropine). The latter was abolished by sympatho-inhibition (reserpine). Reserpine also eliminated the late, 3,4-diaminopyridine-induced tachycardia in WKY, but induced a sustained atropine-sensitive bradycardia in SHR. Inhibition of the parasympathetic component with hemicholinium-3, hexamethonium, or atropine enhanced the late tachycardia in SHR, whereas hexamethonium reduced the tachycardia in WKY. In conclusion, 3,4-diaminopyridine-induced acetylcholine release, and thus enhanced parasympathetic ganglion transmission, with subsequent mAchR activation and bradycardia. 3,4-diaminopyridine also activated tachycardia, initially by enhancing sympathetic ganglion transmission, subsequently by activation of norepinephrine release from sympathetic nerve terminals. The 3,4-diaminopyridine-induced parasympathetic activation was stronger and more sustained in SHR, demonstrating an enhanced inhibitory control of KV on parasympathetic ganglion transmission. This enhanced KV activity may explain the dysfunctional vagal HR control in SHR.
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Affiliation(s)
- Torill Berg
- Division of Physiology, Department of Molecular Medicine, Institute for Basic Medical Sciences, University of Oslo , Oslo , Norway
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Berg T. Altered β1-3-adrenoceptor influence on α2-adrenoceptor-mediated control of catecholamine release and vascular tension in hypertensive rats. Front Physiol 2015; 6:120. [PMID: 25941491 PMCID: PMC4403294 DOI: 10.3389/fphys.2015.00120] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/31/2015] [Indexed: 11/29/2022] Open
Abstract
α2- and β-adrenoceptors (AR) reciprocally control catecholamine release and vascular tension. Disorders in these functions are present in spontaneously hypertensive rats (SHR). The present study tested if α2AR dysfunctions resulted from altered α2AR/βAR interaction. Blood pressure (BP) was recorded through a femoral artery catheter and cardiac output by an ascending aorta flow probe. Total peripheral vascular resistance (TPR) was calculated. Norepinephrine release was stimulated by a 15-min tyramine-infusion, which allows presynaptic release-control to be reflected as differences in overflow to plasma. Surgical stress activated some secretion of epinephrine. L-659,066 (α2AR-antagonist) enhanced norepinephrine overflow in normotensive controls (WKY) but not SHR. Nadolol (β1+2) and ICI-118551 (β2), but not atenolol (β1) or SR59230A [β(3)/1L] prevented this increase. All βAR antagonists allowed L-659,066 to augment tyramine-induced norepinephrine overflow in SHR and epinephrine secretion in both strains. Inhibition of cAMP-degradation with milrinone and β3AR agonist (BRL37344) enhanced the effect of L-659,066 on release of both catecholamines in SHR and epinephrine in WKY. β1/2AR antagonists and BRL37344 opposed the L-659,066-dependent elimination of the TPR-response to tyramine in WKY. α2AR/βAR antagonists had little influence on the TPR-response in SHR. Milrinone potentiated the L-659,066-dependent reduction of the TPR-response to tyramine. Conclusions: β2AR activity was a required substrate for α2AR auto inhibition of norepinephrine release in WKY. β1+2AR opposed α2AR inhibition of norepinephrine release in SHR and epinephrine secretion in both strains. βAR-α2AR reciprocal control of vascular tension was absent in SHR. Selective agonist provoked β3AR-Gi signaling and influenced the tyramine-induced TPR-response in WKY and catecholamine release in SHR.
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Affiliation(s)
- Torill Berg
- Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo Oslo, Norway
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