Abstract 293: Brain Gai2 Proteins Mediate Acute Neural Blood Pressure Responses to Centrally and Peripherally Administered NaCl

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Casey Y Carmichael ◽  
Sarah Mahne ◽  
Richard D Wainford
Keyword(s):  
Blood Pressure ◽  
Neural Control ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
High Salt Diet ◽  
Pharmacological Challenge ◽  
Sprague Dawley Rats ◽  
Blood Pressures ◽  
Blood Pressure Responses

Aim: We have demonstrated hypertension mediated by failure to upregulate PVN Gαi 2 proteins in rats fed a chronic high salt diet, but the role of this mechanism is unknown in acute settings. We examined the effect of central Gαi 2 proteins in the neural control of blood pressure in response to an acute physiological (IV and ICV) and pharmacological challenge. Methods: Twenty-four hour (24-h) ICV Gαi 2 or SCR oligodeoxynucleotide (ODN; 25μg/5μl)-pretreated conscious Sprague-Dawley rats were continuously monitored for changes in HR and MAP in response to peripherally-administered NaCl (3M IV bolus; 0.14 ml/100g) or centrally-administered NaCl (1M ICV; 5μL)(N=4/gp). To determine the cardiac baroreflex MAP was slowly raised to ~175 mmHg using phenylephrine and lowered to ~50 mmHg using sodium nitroprusside in separate group of pre-treated rats (N=8/gp). Results: In response to IV sodium, peak changes in HR were significantly greater in SCR vs. Gαi 2 treated rats (IV 3M NaCl ΔHR [bpm]; SCR -79±15 vs . Gαi 2 -59±12, P<0.05), but no difference was observed in peak changes in MAP (IV 3M NaCl ΔMAP [mmHg] SCR 147±4 mmHg vs . Gαi 2 149±3). In SCR rats, MAP returned to baseline by 100 min whereas Gαi 2 rats remained significantly elevated for 120 min (P<0.05). In response to ICV sodium, we observed no difference between groups in peak HR changes (ICV 1M NaCl ΔHR [bpm] -23±8 bpm vs . Gαi 2 -22±8) or peak MAP changes (ICV 1M NaCl ΔMAP [mmHg] 16±3 mmHg vs . Gαi 2 9±3). In SCR rats, MAP returned to baseline by 50 min whereas Gαi 2 rats remained elevated for 90 min. The 24h Gαi 2 ODN pretreatment significantly altered the high-, but not low-pressure gain of the baroreflex in response to pharmacological challenge (MAP=180 mmHg, SCR HR=270 bpm, Gαi 2 HR=307 bpm, P<0.05). Conclusion: Downregulation of Gαi 2 proteins resulted in altered cardiac baroreflex function by impairing reflex decreases in HR and mediating significantly prolonged elevated MAP in response to peripherally administered sodium. This highlights a previously undiscovered role of brain Gαi 2 proteins in the baroreflex control of HR at elevated blood pressures—a factor that may contribute to elevated MAP in neurogenic models of hypertension.

Effect of a perinatal high-salt diet on blood pressure control mechanisms in young Sprague-Dawley rats

2004 ◽  
Vol 286 (4) ◽  
pp. R764-R770 ◽  
Author(s):  
Steven J. Swenson ◽  
Robert C. Speth ◽  
James P. Porter
Keyword(s):  
Blood Pressure ◽  
Nervous Activity ◽  
Receptor Activation ◽  
High Salt ◽  
Early Age ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
High Salt Diet ◽  
Salt Diet ◽  
Sprague Dawley Rats

In the present investigation we sought to determine if a perinatal high-salt treatment affects blood pressure at an early age (30 days), and if so, to determine the mechanisms responsible for the hypertension. Pregnant dams were given an 8% NaCl diet [high-salt (HS) rats] during the final one-third of gestation and throughout the suckling period. After weaning, the pups continued to receive the high-salt diet until testing at age 30 days. Control groups received a normal-salt diet (NS rats). In HS rats, mean arterial pressure (MAP) was significantly increased (110 ± 5 vs. 96 ± 3 mmHg) compared with NS rats. Blockade of brain AT1 receptors with intracerebroventricular losartan decreased MAP in HS but not NS rats. Blockade of α-adrenergic receptors with intravenous phentolamine or ganglionic transmission with intravenous chlorisondamine produced a greater decrease in MAP in HS rats. Baroreflex control of heart rate was assessed using a four-parameter logistics function. The mid-range MAP (p3) was significantly increased in the HS rats. No other baroreflex parameters were affected. Specific binding of 125I-[Sar1,Ile8]ANG II to AT1 receptors was increased in the subfornical organ (SFO) of the HS rats. Expression of AT1a receptor mRNA was greater in both SFO and PVN of the HS rats. These data suggest that even at an early age, Sprague-Dawley rats treated with a perinatal high-salt diet are hypertensive. The elevated blood pressure appears to be caused by increased sympathetic nervous activity, resulting, in part, from increased brain AT1 receptor activation.

Role of Autonomic Nervous System in Maintenance of Cerebral and Renal Hypertension

1957 ◽  
Vol 188 (2) ◽  
pp. 371-374 ◽  
Author(s):  
Sol Rothman ◽  
Douglas R. Drury
Keyword(s):  
Blood Pressure ◽  
Nervous System ◽  
Autonomic Nervous System ◽  
Renal Hypertension ◽  
The Other ◽  
Peripheral Vasculature ◽  
Blood Pressures ◽  
Sympathetic Nervous ◽  
Blood Pressure Responses

The blood pressure responses to various drugs were investigated in renal hypertensive, cerebral hypertensive and normotensive rabbits. Hexamethonium bromide and Dibenamine reduced the blood pressures of renal and cerebral hypertensives. Effects in the normal were insignificant. The cerebral hypertensive's blood pressure was slightly affected by benzodioxane. Blood pressure was not reduced at all in the other groups. Blood pressure of the renal hypertensive rabbit was greatly reduced by Veriloid and dihydroergocornine. Blood pressures of cerebral and normal animals were affected to a lesser degree. The results suggest that maintenance of hypertension in the cerebral hypertensive rabbit depends on an overactive sympathetic nervous system, possibly due to the release of medullary pressor centers from inhibitory impulses originating in higher centers; whereas, the maintenance of hypertension in the renal hypertensive rabbit may be attributed to an increased reactivity of the peripheral vasculature to a normal sympathetic tone.

Abstract 15839: Effect of Serotonin Neuron Depletion on Arterial Blood Pressure Regulation in Young Rats

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Jennifer Magnusson ◽  
Kevin Cummings
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Recovery Period ◽  
Sudden Infant Death ◽  
Sudden Infant ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
Hypoxic Conditions ◽  
Arterial Blood

Infants dying of Sudden Infant Death Syndrome (SIDS) have reduced brainstem serotonin (5-hydroxytryptamine, 5-HT) where some cases die following episodes of severe bradycardia and hypoxemia. The specific role of central 5-HT in resting arterial blood pressure (BP) and on baroreflex sensitivity during neonatal life has not been studied. In adult animals, systemic depletion of 5-HT increases BP with no effect on heart rate (HR) and reduces the sensitivity of the baroreflex. Other studies have also shown that a loss of central 5-HT beginning in embryogenesis reduces resting BP and HR in adulthood. Based on these reports, we hypothesized that loss of brainstem 5-HT neurons in the neonatal period would reduce baseline BP and HR as well as reduce baroreflex gain. To test this, we utilized 3-week old Sprague Dawley rats treated centrally with 5,7-dihydroxytryptamine (5,7-DHT, n=4; ~120 ug in saline, i.c.v.), a chemical that is toxic to serotonergic neurons. Littermate controls were injected with saline (CTRL, n=5, ~3ul, i.c.v.). We measured BP with a femoral artery catheter. HR was derived from BP. Following a recovery period, we measured resting variables for 15 minutes and then injected phenylephrine (PE; 3mg/kg s.c.) followed by sodium nitroprusside (SNP; 2.5mg/kg s.c.), separated by 15 minutes, to induce pressor or depressor responses, respectively. For both responses, baroreflex gain was calculated as the [[Unable to Display Character: &#8710;]]HR at the maximum [[Unable to Display Character: &#8710;]]BP following drug injection. We found that a loss of 5-HT neurons did not alter baseline BP (p>0.05) but did reduce baseline HR when compared to control littermates (p<0.02). 5-HT neuron deficiency tended to reduce baroreflex gain in response to PE (CTRL: -2.756 ± 0.483 beats/mmHg; 5,7-DHT: -1.499 ± 0.348 beats/mmHg; p=0.058), but not SNP (CTRL: -2.408 ± 0.351 beats/mmHg; 5,7-DHT: -3.316 ± 1.214 beats/mmHg; p>0.05). Our data indicate that brainstem 5-HT maintains resting HR, and is involved in baroreflex control of HR in response to hypertensive stimuli. Reduced brainstem 5-HT may predispose an infant to SIDS via altered autonomic control of BP and HR. The role of 5-HT in BP regulation during hypoxic conditions remains to be elucidated.

Abstract 035: Differential Sodium-evoked Activation of Pvn Magnocellular vs. Parvocellular Neurons in Rats Lacking Central GαI

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Casey Y Carmichael ◽  
Richard D Wainford
Keyword(s):  
Blood Pressure ◽  
Pressure Control ◽  
Blood Pressure Regulation ◽  
Pressure Regulation ◽  
Sprague Dawley ◽  
Significant Component ◽  
Sprague Dawley Rats ◽  
Parvocellular Neurons ◽  
Circulating Levels

Aim: To determine the role of brain Gαi 2 proteins in mediating sodium-evoked PVN neuronal activation and blood pressure regulation in conscious rats. Methods: 24-h intracerebroventricular scrambled (SCR) or Gαi 2 oligodeoxynucleotide (ODN; 25μg/5μl)-pretreated conscious Sprague-Dawley rats were monitored for changes in MAP in response to HS (IV 3M NaCl; 0.14 ml/100g). Rats were sacrificed at control (C), 10, 40, or 100-min post-HS for PVN cFos IHC and analysis of plasma AVP and NE. Separate groups received a V 1a receptor antagonist (IV; 10 μg/ml/kg) 5-min prior to HS. Results: No difference was observed in sodium-evoked peak change in MAP and MAP remained elevated at 100-min in Gαi 2 but not SCR ODN rats (MAP 100-min post-HS [mmHg] SCR 134±2 vs Gαi 2 146±3, P<0.05). Significant increases in the number of Fos + PVN magnocellular neurons were observed post-HS in SCR and Gαi 2 ODN groups ([Fos + cells] SCR C 3±1 vs 100-min 31±5; Gαi 2 C 2±0 vs 100-min 26±4, P <0.05). A rapid increase in circulating AVP was observed at 10-min in both SCR (plasma AVP [pg/mL] C 12.2±1.6 vs 10-min 62.8±6.9, P <0.05) and Gαi 2 ODN (plasma AVP [pg/mL] C 12.1±1.5 vs 10-min 67.7±7.7 P <0.05) groups and returned to control levels at 40- and 100-min. SCR ODN rats exhibited significant increases in the number of Fos + PVN parvocellular neurons ([Fos+ cells] C 15±1 vs 100-min 67±4, P <0.05) and a significant suppression in circulating NE post-HS (plasma NE [nmol/L] C 44.1±4.9 vs 10-min 17.4±3.9, P <0.05). Gαi 2 ODN rats exhibited significantly less Fos + parvocellular neurons compared to SCR ODN rats (100-min [Fos+ cells] SCR 67±4 vs Gαi 2 30±2, P <0.05) and failed to suppress circulating NE ( P >0.05). V 1a receptor blockade prevented a HS-evoked increase in MAP in SCR ODN rats while Gαi 2 ODN rats exhibited elevated MAP (MAP 100-min [mmHg] SCR 125±2 vs Gαi 2 135±0, P <0.05). Conclusion: Brain Gαi 2 proteins are required to mediate sodium-evoked parvocellular sympathetic, but not magnocellular vasopressinergic, responses to maintain physiological blood pressure regulation. A significant component of blood pressure control in this setting is regulated by the sympathetic nervous system, as supported by the attenuated activation of PVN parvocellular neurons and a failure to suppress circulating levels of NE in Gαi 2 ODN rats.

scholarly journals Sodium, potassium and chloride utilization by rats given various inorganic anions

1991 ◽  
Vol 66 (3) ◽  
pp. 523-532 ◽  
Author(s):  
Susan M. Kaup ◽  
Alison R. Behling ◽  
J. L. Greger
Keyword(s):  
Blood Pressure ◽  
Plasma Renin Activity ◽  
Plasma Renin ◽  
Basal Diet ◽  
Renin Activity ◽  
Sprague Dawley ◽  
Sodium Potassium ◽  
Sprague Dawley Rats ◽  
Blood Pressures ◽  
Sodium And Potassium

The purpose of the present studies was to examine the effect of ingestion of sodium and potassium salts of various fixed anions on blood pressure, and to assess interactions among electrolytes. In the first study, Sprague-Dawley rats fed on purified diets supplemented with Na salts of chloride, sulphate, bisulphate, carbonate and bicarbonate for 7 weeks developed higher blood pressures than rats fed on the basal diet. In a second study, rats fed on Na or K salts of HSO4, HCO3 or Cl had higher blood pressures than rats fed on the basal diet. Blood pressure measurements were not correlated with plasma volume, plasma renin activity, or plasma atrial natriuretic peptide concentrations at 7 weeks. Plasma renin activity was depressed in rats fed on supplemental Na and even more in rats fed on supplemental K salts rather than the basal diet. Generally, rats fed on supplemental Na excreted Na in urine and absorbed Na in the gut more efficiently than rats fed on the basal diet or diets supplemented with K, but the anions fed also altered Na absorption and excretion. In a third study, rats fed on diets supplemented with any Cl salt, but especially KCI, absorbed K more efficiently than those fed on the basal diet. In studies 1 and 2, the efficiency of urinary excretion of K was greatest when HCO3 and CO3 salts were fed and least when HSO4 salts were fed. Despite large variations in the efficiency of absorption and excretion of Na and K, tissue levels of the electrolytes remained constant.

scholarly journals Kidney dopamine D1-like receptors and angiotensin 1–7 interaction inhibits renal Na+ transporters

2019 ◽  
Vol 317 (4) ◽  
pp. F949-F956 ◽  
Author(s):  
Anees A. Banday ◽  
Andrea Diaz Diaz ◽  
Mustafa Lokhandwala
Keyword(s):  
Blood Pressure ◽  
Tyrosine Hydroxylase ◽  
Cumulative Effect ◽  
Sprague Dawley ◽  
Hydroxylase Activity ◽  
Tyrosine Hydroxylase Activity ◽  
Sprague Dawley Rats ◽  
Renal Dopamine ◽  
G Protein Coupled

The role of dopamine D1-like receptors (DR) in the regulation of renal Na+ transporters, natriuresis, and blood pressure is well established. However, the involvement of the angiotensin 1–7 (ANG 1−7)-Mas receptor in the regulation of Na+ balance and blood pressure is not clear. The present study aimed to investigate the hypothesis that ANG 1–7 can regulate Na+ homeostasis by modulating the renal dopamine system. Sprague-Dawley rats were infused with saline alone (vehicle) or saline with ANG 1–7, ANG 1–7 antagonist A-779, DR agonist SKF38393, and antagonist SCH23390. Infusion of ANG 1–7 caused significant natriuresis and diuresis compared with saline alone. Both natriuresis and diuresis were blocked by A-779 and SCH23390. SKF38393 caused a significant, SCH23390-sensitive natriuresis and diuresis, and A-779 had no effect on the SKF38393 response. Concomitant infusion of ANG 1–7 and SKF38393 did not show a cumulative effect compared with either agonist alone. Treatment of renal proximal tubules with ANG 1–7 or SKF38393 caused a significant decrease in Na+-K+-ATPase and Na+/H+ exchanger isoform 3 activity. While SCH23390 blocked both ANG 1–7- and SKF38393-induced inhibition, the DR response was not sensitive to A-779. Additionally, ANG 1–7 activated PKG, enhanced tyrosine hydroxylase activity via Ser40 phosphorylation, and increased renal dopamine production. These data suggest that ANG 1–7, via PKG, enhances tyrosine hydroxylase activity, which increases renal dopamine production and activation of DR and subsequent natriuresis. This study provides evidence for a unidirectional functional interaction between two G protein-coupled receptors to regulate renal Na+ transporters and induce natriuresis.

Orchidectomy attenuates impaired endothelial effects of a high-salt diet in Sprague–Dawley rats

2011 ◽  
Vol 89 (4) ◽  
pp. 295-304 ◽  
Author(s):  
A.K. Oloyo ◽  
O.A. Sofola ◽  
C.N. Anigbogu
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
High Salt ◽  
Sprague Dawley ◽  
High Salt Diet ◽  
Salt Diet ◽  
Arterial Blood ◽  
Sprague Dawley Rats ◽  
Induced Hypertension

The effect of sex hormones on vascular reactivity is considered one of the underlying factors contributing to gender differences in cardiovascular functions and diseases. Experiments were designed to investigate the role of androgens in salt-induced hypertension by assessing the relaxation response of isolated aortic rings to acetylcholine and sodium nitroprusside in the presence or absence of l-nitroarginine methyl ester in Sprague–Dawley rats. The rats were either orchidectomized or sham-operated, with or without testosterone replacement, and were placed on a normal or high-salt diet for 6 weeks. The results indicate a significant increase (p < 0.001) in the mean arterial blood pressure of rats on the high-salt diet, when compared with control or orchidectomized rats. Orchidectomy elicited a reduction in mean arterial blood pressure (p < 0.01), while testosterone replacement normalized mean arterial blood pressure to values seen in intact rats on the high-salt diet. The high-salt diet reduced the relaxation response to acetylcholine both in the presence and absence of inhibition of endothelial nitric oxide synthase with l-nitroarginine methyl ester. Bilateral orchidectomy attenuated the impaired endothelial function induced by the high-salt diet in rats, but this was reversed by concomitant administration of testosterone, suggesting a role for androgens in enhancing long-term vascular smooth muscle tone and hence maintenance of high blood pressure in salt-induced hypertension.

scholarly journals 20-HETE and CYP4A2 ω-hydroxylase contribute to the elevated blood pressure in hyperandrogenemic female rats

2016 ◽  
Vol 311 (1) ◽  
pp. F71-F77 ◽  
Author(s):  
Carolina Dalmasso ◽  
Rodrigo Maranon ◽  
Chetan Patil ◽  
Mohadetheh Moulana ◽  
Damian G. Romero ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Polycystic Ovary ◽  
Female Rats ◽  
Male Rats ◽  
Sprague Dawley ◽  
Hydroxylase Activity ◽  
Sprague Dawley Rats ◽  
Low Salt ◽  
Cytochrome P 450

In male rats, androgen supplements increase 20-hydroxyeicosatetraenoic acid (20-HETE) via cytochrome P-450 (CYP)4A ω-hydroxylase and cause an increase in blood pressure (BP). In the present study, we determined the roles of 20-HETE and CYP4A2 on the elevated BP in hyperandrogenemic female rats. Chronic dihydrotestosterone (DHT) increased mean arterial pressure (MAP) in female Sprague-Dawley rats (96 ± 2 vs. 108 ± 2 mmHg, P < 0.05) and was associated with increased renal microvascular CYP4A2 mRNA expression (15-fold), endogenous renal 20-HETE (5-fold), and ω-hydroxylase activity (3-fold). Chronic DHT also increased MAP in low salt-fed Dahl salt-resistant female rats (81 ± 4 vs. 95 ± 1 mmHg, P < 0.05) but had no effect on MAP in Dahl salt-sensitive female rats (154 ± 3 vs. 153 ± 3 mmHg), which are known to be 20-HETE deficient. To test the role of CYP4A2, female CYP4A2−/− and SS.5Bn (wild type) rats were treated with DHT. DHT increased MAP in SS.5Bn female rats (104 ± 1 vs. 128 ± 1 mmHg, P < 0.05) but had no effect in CYP4A2−/− female rats (118 ± 1 vs. 120 ± 1 mmHg). Renal microvascular 20-HETE was reduced in control CYP4A2−/− female rats and was increased with DHT in SS.5Bn female rats (6-fold) but not CYP4A2−/− female rats. ω-Hydroxylase activity was 40% lower in control CYP4A2−/− female rats than in SS.5Bn female rats, and DHT decreased ω-hydroxylase activity in SS.5Bn female rats (by 50%) but significantly increased ω-hydroxylase activity in CYP4A2−/− female rats (3-fold). These data suggest that 20-HETE via CYP4A2 contributes to the elevation in BP in hyperandrogenemic female rats. The data also suggest that 20-HETE synthesis inhibition may be effective in treating the elevated BP in women with hyperandrogenemia, such as women with polycystic ovary syndrome.

Increased blood pressure responses in neuropeptide Y transgenic rats

2001 ◽  
Vol 281 (2) ◽  
pp. R417-R426 ◽  
Author(s):  
Mieczyslaw Michalkiewicz ◽  
Teresa Michalkiewicz ◽  
David L. Kreulen ◽  
Stuart J. McDougall
Keyword(s):  
Blood Pressure ◽  
Arterial Pressure ◽  
Neuropeptide Y ◽  
Sympathetic Nerves ◽  
Sprague Dawley ◽  
Transgenic Rats ◽  
Resting Blood Pressure ◽  
Blood Pressure Responses

Considering the coexistence of neuropeptide Y (NPY) and norepinephrine in perivascular sympathetic nerves and the known vasoconstrictor cooperation of NPY with norepinephrine, we investigated the involvement of NPY in long-term control of cardiovascular functions using NPY transgenic (NPY-tg) rats. These rats were developed by injection of the rat (Sprague-Dawley) pronuclei with a 14.5-kb clone of the rat structural NPY gene. When compared with nontransgenic littermates, NPY concentrations were significantly increased in a number of cardiovascular tissues of NPY-tg hemizygotes. Direct basal mean arterial pressure and heart rate were not changed, but calculated total vascular resistance was significantly increased in NPY-tg subjects. Arterial pressure increases, in response to norepinephrine injection, were greater in the NPY-tg rats. Also, the hypotension and bradycardia in response to hemorrhage were significantly reduced in NPY-tg subjects. These results indicate that NPY, when expressed in increased amounts, potentiates the pressor effects of norepinephrine and contributes to maintaining blood pressure during hemorrhage, but it does not alter resting blood pressure. These transgenic rats will facilitate studies of the role of NPY signaling in cardiovascular regulation, particularly regarding its functional cooperation with norepinephrine.

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