Chronic high-sodium diet intake after weaning lead to neurogenic hypertension in adult Wistar rats

Exercise-induced neuroplasticity in autonomic nuclei restores the cardiac vagal tone and baroreflex dysfunction in aged hypertensive rats

Aging is accompanied by considerable deterioration of homeostatic systems, such as autonomic imbalance characterized by heightened sympathetic activity, lower parasympathetic tone, and depressed heart rate (HR) variability, which are aggravated by hypertension. Here, we hypothesized that these age-related deficits in aged hypertensive rats can be ameliorated by exercise training, with benefits to the cardiovascular system. Therefore, male 22-mo-old spontaneously hypertensive rats (SHRs) and age-matched Wistar Kyoto (WKY) submitted to moderate-intensity exercise training (T) or kept sedentary (S) for 8 wk were evaluated for hemodynamic/autonomic parameters, baroreflex sensitivity, cardiac sympathetic/parasympathetic tone and analysis of dopamine β-hydroxylase (DBH+) and oxytocin (OT+) pathways of autonomic brain nuclei. Aged SHR-S versus WKY-S exhibited elevated mean arterial pressure (MAP: +51%) and HR (+20%), augmented pressure/HR variability, no cardiac vagal tone, and depressed reflex control of the heart (HR range, -28%; gain, -49%). SHR-T exhibited a lower resting HR, a partial reduction in the MAP (-14%), in the pressure/HR variabilities, and restored parasympathetic modulation, with improvement of baroreceptor reflex control when compared with SHR-S. Exercise training increased the ascending DBH+ projections conveying peripheral information to the paraventricular nucleus of hypothalamus (PVN), augmented the expression of OT+ neurons, and reduced the density of DBH+ neurons in the rostral ventrolateral medulla (RVLM) of SHR-T. Data indicate that exercise training induces beneficial neuroplasticity in brain autonomic circuitry, and it is highly effective to restore the parasympathetic tone, and attenuation of age-related autonomic imbalance and baroreflex dysfunction, thus conferring long-term benefits for cardiovascular control in aged hypertensive individuals.NEW & NOTEWORTHY Exercise training reduces high blood pressure and cardiovascular autonomic modulation in aged hypertensive rats. The dysfunction in the baroreflex sensitivity and impaired parasympathetic tone to the heart of aged hypertensive rats are restored by exercise training. Exercise induces beneficial neuroplasticity in the brain nuclei involved with autonomic control of cardiovascular function of aged hypertensive rats.

Short exposure to high salt in drinking solution leads to a cardiovascular phenotype of hypertension without changes in the blood volume of rats

NEW FINDINGS

What is the central question of this study? Is the cardiovascular phenotype of high blood pressure observed in rats salt loaded with 2% NaCl in drinking solution a blood volume-dependent hypertension? What is the main finding and its importance? Animals exposed to 2% NaCl drinking solution develop hypertension, with dominance of sympathetic outflow and high [Na+ ] in the cerebrospinal fluid, but without changes in the blood volume. The phenotype of salt-dependent hypertension might be related to accumulation of [Na+ ] in the cerebrospinal fluid, which makes it an interesting animal model in which to study the neuronal pathways involved in control of the circulation in osmotic challenge conditions.

ABSTRACT

Evidence suggests that hypertension induced by high salt intake is correlated with an autonomic imbalance that favours sympathetic hyperactivity and an increase in vascular resistance, indicating a neurogenic component to this pathology. Although there are several animal models in which to study salt-induced hypertension with prolonged exposure to a high-sodium diet, here we sought to investigate whether the increase in arterial blood pressure of rats subjected to a short exposure to high salt, with 2% NaCl drinking solution instead of water, relies on changes in the circulating blood volume. Male Wistar rats were divided randomly into three groups: euhydrated (EU, n = 10), salt loaded (SL, n = 13) and water deprived (WD, n = 6). The SL rats exhibited a significant increase in mean arterial blood pressure, with a large low-frequency component of systolic arterial blood pressure variability, when compared with the EU group. Circulating blood volume did not differ between SL and EU rats, but it was lower in WD rats. Compared with EU rats, the [Na+ ] in cerebrospinal fluid was higher in SL rats and similar in magnitude to the WD rats. Plasma [Na+ ] did not differ between SL and EU rats, but it was higher in WD rats. Collectively, our data suggest that the hypertension induced by a short exposure to high salt intake closely resembles a neurogenic mechanism, but not a blood volume-dependent mechanism, with cumulative [Na+ ] in the cerebrospinal fluid that could be associated with changes in the neurochemistry of autonomic nuclei, which are highly susceptible to osmotic stress related to high salt consumption.

Antihypertensive Effects of Aqueous Extract of Ricinodendron heudelotii (Baill.) Pierre (Euphorbiaceae) in Wistar Rat

Ricinodendron heudelotii stem bark is commonly used in Cameroonian traditional medicine to treat cardiovascular diseases such as hypertension. The present study was designed to investigate the antihypertensive and antioxidant properties of the aqueous extract of Ricinodendron heudelotii in salt-induced hypertensive rats. Analysis by HPLC-ESI-Q-TOF-MS was used to identify various chemical components of the extract. A total of thirty rats were used for each test. High-salt hypertension was induced in rats by oral administration of NaCl for 12 weeks. Mean blood pressure (MBP) and heart rate (HR) were monitored by noninvasive methods. Oral administration of Ricinodendron heudelotii significantly ( $p<0.01$ ) reduced the increase of mean blood pressure (23.12%, 26.14%, and 24.34%) and heart rate (31.19%, 31.09%, and 26.98%), respectively, at the doses of 40, 20, and 6 mg/kg, compared to the hypertensive group. All the doses tested significantly reduced or/and ameliorated biochemical and oxidative stress parameters. Histological analysis showed that Ricinodendron heudelotii restored renal disorders induced by the administration of salt. The aqueous extract of Ricinodendron heudelotii exerts a cardioprotective effect, and the antihypertensive activity seems associated with an improvement in antioxidant status. Overall, the results justify and support the traditional use of Ricinodendron heudelotii.

Post-Ganglionic Sympathetic Neurons can Directly Sense Raised Extracellular Na+ via SCN7a/Nax

The relationship between dietary NaCl intake and high blood pressure is well-established, and occurs primarily through activation of the sympathetic nervous system. Nax, a Na+-sensitive Na+ channel, plays a pivotal role in driving sympathetic excitability, which is thought to originate from central regions controlling neural outflow. We investigated whether post-ganglionic sympathetic neurons from different ganglia innervating cardiac and vasculature tissue can also directly sense extracellular Na+. Using whole-cell patch clamp recordings we demonstrate that sympathetic neurons from three sympathetic ganglia (superior cervical, stellate and superior mesenteric/coeliac) respond to elevated extracellular NaCl concentration. In sympathetic stellate ganglia neurons, we established that the effect of NaCl was dose-dependent and independent of osmolarity, Cl- and membrane Ca2+ flux, and critically dependent on extracellular Na+ concentration. We show that Nax is expressed in sympathetic stellate ganglia neurons at a transcript and protein level using single-cell RNA-sequencing and immunohistochemistry respectively. Additionally, the response to NaCl was prevented by siRNA-mediated knockdown of Nax, but not by inhibition of other membrane Na+ pathways. Together, these results demonstrate that post-ganglionic sympathetic neurons are direct sensors of extracellular Na+ via Nax, which could contribute to sympathetic driven hypertension.

Phyllanthus amarus attenuated derangement in renal-cardiac function, redox status, lipid profile and reduced TNF-α, interleukins-2, 6 and 8 in high salt diet fed rats

High salt diet (HSD) has been implicated in the etiopathogenesis of immune derangement, cardiovascular disorders and, metabolic syndromes. This study investigated the protective effect of ethanol extract of Phyllanthus amarus (EEPA) against high salt diet (HSD) induced biochemical and metabolic derangement in male Wistar rats. The rats were divided into 5 groups of 6 animals each as follows; control group fed with normal rat chow, negative control group, fed HSD only, animals on HSD treated orally with 75 mg/kg, 100 mg/kg, and, 150 mg/kg EEPA once daily. At the end of 8 weeks treatment, lipid profile (TG, TC, LDL, and VLDL), oxidative stress (catalase, reduced glutathione, and malondialdehyde), inflammatory (TNF-a, interleukins 2, 6, and 8), cardiac (lactate dehydrogenase, creatine kinase) and kidney function markers (urea, uric acid, creatinine) were assessed. Serum TG, TC, LDL, and VLDL content were significantly (p < 0.05) elevated in HSD-only fed rats, while HDL was significantly elevated in a concentration-dependent manner in EEPA treated animals. The extract produced a significant (p < 0.05) and dose-dependent increase in the antioxidant enzymes activities and a significant reduction in the malondialdehyde level. A significant (p < 0.05) dose-dependent reduction in serum TNF-alpha, IL-2, 6, and 8 of EEPA treated rats compared with HSD-fed rats was observed. More so, reduction in serum LDH, creatine kinase, creatinine, urea, and uric acid activity of extract-treated animals were noted. EEPA attenuated high salt diet-induced oxidative stress, inflammation, and dyslipidemia in rats.

Sodium activates human monocytes via the NADPH oxidase and isolevuglandin formation

AIMS

Prior studies have focused on the role of the kidney and vasculature in salt-induced modulation of blood pressure; however, recent data indicate that sodium accumulates in tissues and can activate immune cells. We sought to examine mechanisms by which salt causes activation of human monocytes both in vivo and in vitro.

METHODS AND RESULTS

To study the effect of salt in human monocytes, monocytes were isolated from volunteers to perform several in vitro experiments. Exposure of human monocytes to elevated Na+ex vivo caused a co-ordinated response involving isolevuglandin (IsoLG)-adduct formation, acquisition of a dendritic cell (DC)-like morphology, expression of activation markers CD83 and CD16, and increased production of pro-inflammatory cytokines tumour necrosis factor-α, interleukin (IL)-6, and IL-1β. High salt also caused a marked change in monocyte gene expression as detected by RNA sequencing and enhanced monocyte migration to the chemokine CC motif chemokine ligand 5. NADPH-oxidase inhibition attenuated monocyte activation and IsoLG-adduct formation. The increase in IsoLG-adducts correlated with risk factors including body mass index, pulse pressure. Monocytes exposed to high salt stimulated IL-17A production from autologous CD4+ and CD8+ T cells. In addition, to evaluate the effect of salt in vivo, monocytes and T cells isolated from humans were adoptively transferred to immunodeficient NSG mice. Salt feeding of humanized mice caused monocyte-dependent activation of human T cells reflected by proliferation and accumulation of T cells in the bone marrow. Moreover, we performed a cross-sectional study in 70 prehypertensive subjects. Blood was collected for flow cytometric analysis and 23Na magnetic resonance imaging was performed for tissue sodium measurements. Monocytes from humans with high skin Na+ exhibited increased IsoLG-adduct accumulation and CD83 expression.

CONCLUSION

Human monocytes exhibit co-ordinated increases in parameters of activation, conversion to a DC-like phenotype and ability to activate T cells upon both in vitro and in vivo sodium exposure. The ability of monocytes to be activated by sodium is related to in vivo cardiovascular disease risk factors. We therefore propose that in addition to the kidney and vasculature, immune cells like monocytes convey salt-induced cardiovascular risk in humans.

Cardioprotective potential of indol-3-carbinol against high salt induced myocardial stress and hypertrophy in Sprague dawley rats besides molecular docking on muscarinic receptor-2

The vegetative chemical constituent, indol-3-carbinol (I-3-C) studied for its cardioprotective potential in male Sprague dawley rats. The I-3-C at 20 mg/Kg b.w, p.o significantly (p < 0.001) attenuated the high salt induced hypertrophy and produced antihypertensive effect (p < 0.001) as similar to losartan. Further, it significantly reduced the levels of C-reactive protein (p < 0.05), creatinine kinases isoenzyme (p < 0.01), serum lactate dehydrogenase (p < 0.05), myeloperoxidase (p < 0.01) and hydroxyproline (p < 0.01), subsequently increased the nitric oxide level (p < 0.05). The carotid ligation for vascular reactivity against vasopressors revealed a lesser magnitude of change (p < 0.05) in invasive blood pressure for I-3-C, compared to high salt treated animals (p < 0.001). In histology of heart tissue also supported the cardioprotective effect of I-3-C. In silico molecular docking of I-3-C on muscarinic receptor-2 showed the amino acid interaction as similar to acetylcholine.

Swimming training improves cardiovascular autonomic dysfunctions and prevents renal damage in rats fed a high-sodium diet from weaning

NEW FINDINGS

What is the central question of this study? How does swimming exercise training impact hydro-electrolytic balance, renal function, sympathetic contribution to resting blood pressure and cerebrospinal fluid (CSF) [Na⁺ ] in rats fed a high-sodium diet from weaning? What is the main finding and its importance? An exercise-dependent reduction in blood pressure was associated with decreased CSF [Na⁺ ], sympathetically driven vasomotor tonus and renal fibrosis indicating that the anti-hypertensive effects of swimming training in rats fed a high-sodium diet might involve neurogenic mechanisms regulated by sodium levels in the CSF rather than changes in blood volume.

ABSTRACT

High sodium intake is an important factor associated with hypertension. High-sodium intake with exercise training can modify homeostatic hydro-electrolytic balance, but the effects of this association are mostly unknown. In this study, we sought to investigate the effects of swimming training (ST) on cerebrospinal fluid (CSF) Na⁺ concentration, sympathetic drive, blood pressure (BP) and renal function of rats fed a 0.9% Na⁺ (equivalent to 2% NaCl) diet with free access to water for 22 weeks after weaning. Male Wistar rats were assigned to two cohorts: (1) fed standard diet (SD) and (2) fed high-sodium (HS) diet. Each cohort was further divided into trained and sedentary groups. ST normalised BP levels of HS rats as well as the higher sympathetically related pressor activity assessed by pharmacological blockade of ganglionic transmission (hexamethonium). ST preserved the renal function and attenuated the glomerular shrinkage elicited by HS. No change in blood volume was found among the groups. CSF [Na⁺ ] levels were higher in sedentary HS rats but were reduced by ST. Our findings showed that ST effectively normalised BP of HS rats, independent of its effects on hydro-electrolytic balance, which might involve neurogenic mechanisms regulated by Na⁺ levels in the CSF as well as renal protection.

Salt-dependent hypertension and inflammation: targeting the gut-brain axis and the immune system with Brazilian green propolis

Systemic arterial hypertension (SAH) is a major health problem around the world and its development has been associated with exceeding salt consumption by the modern society. The mechanisms by which salt consumption increase blood pressure (BP) involve several homeostatic systems but many details have not yet been fully elucidated. Evidences accumulated over the last 60 decades raised the involvement of the immune system in the hypertension development and opened a range of possibilities for new therapeutic targets. Green propolis is a promising natural product with potent anti-inflammatory properties acting on specific targets, most of them participating in the gut-brain axis of the sodium-dependent hypertension. New anti-hypertensive products reinforce the therapeutic arsenal improving the corollary of choices, especially in those cases where patients are resistant or refractory to conventional therapy. This review sought to bring the newest advances in the field articulating evidences that show a cross-talking between inflammation and the central mechanisms involved with the sodium-dependent hypertension as well as the stablished actions of green propolis and some of its biologically active compounds on the immune cells and cytokines that would be involved with its anti-hypertensive properties.

Adipose Mesenchymal Cells-Derived EVs Alleviate DOCA-Salt-Induced Hypertension by Promoting Cardio-Renal Protection

Hypertension is a long-term condition that can increase organ susceptibility to insults and lead to severe complications such as chronic kidney disease (CKD). Extracellular vesicles (EVs) are cell-derived membrane structures that participate in cell-cell communication by exporting encapsulated molecules to target cells, regulating physiological and pathological processes. We here demonstrate that multiple administration of EVs from adipose-derived mesenchymal stromal cells (ASC-EVs) in deoxycorticosterone acetate (DOCA)-salt hypertensive model can protect renal tissue by maintaining its filtration capacity. Indeed, ASC-EVs downregulated the pro-inflammatory molecules monocyte chemoattracting protein-1 (MCP-1) and plasminogen activating inhibitor-1 (PAI1) and reduced recruitment of macrophages in the kidney. Moreover, ASC-EVs prevented cardiac tissue fibrosis and maintained blood pressure within normal levels, thus demonstrating their multiple favorable effects in different organs. By applying microRNA (miRNA) microarray profile of the kidney of DOCA-salt rats, we identified a selective miRNA signature associated with epithelial-mesenchymal transition (EMT). One of the key pathways found was the axis miR-200-TGF-β, that was significantly altered by EV administration, thereby affecting the EMT signaling and preventing renal inflammatory response and fibrosis development. Our results indicate that EVs can be a potent therapeutic tool for the treatment of hypertension-induced CKD in cardio-renal syndrome.

Regulation of CSF and Brain Tissue Sodium Levels by the Blood-CSF and Blood-Brain Barriers During Migraine

Cerebrospinal fluid (CSF) and brain tissue sodium levels increase during migraine. However, little is known regarding the underlying mechanisms of sodium homeostasis disturbance in the brain during the onset and propagation of migraine. Exploring the cause of sodium dysregulation in the brain is important, since correction of the altered sodium homeostasis could potentially treat migraine. Under the hypothesis that disturbances in sodium transport mechanisms at the blood-CSF barrier (BCSFB) and/or the blood-brain barrier (BBB) are the underlying cause of the elevated CSF and brain tissue sodium levels during migraines, we developed a mechanistic, differential equation model of a rat's brain to compare the significance of the BCSFB and the BBB in controlling CSF and brain tissue sodium levels. The model includes the ventricular system, subarachnoid space, brain tissue and blood. Sodium transport from blood to CSF across the BCSFB, and from blood to brain tissue across the BBB were modeled by influx permeability coefficients P_BCSFB and P_BBB, respectively, while sodium movement from CSF into blood across the BCSFB, and from brain tissue to blood across the BBB were modeled by efflux permeability coefficients PBCSFB′ and PBBB′, respectively. We then performed a global sensitivity analysis to investigate the sensitivity of the ventricular CSF, subarachnoid CSF and brain tissue sodium concentrations to pathophysiological variations in P_BCSFB, P_BBB, PBCSFB′ and PBBB′. Our results show that the ventricular CSF sodium concentration is highly influenced by perturbations of P_BCSFB, and to a much lesser extent by perturbations of PBCSFB′. Brain tissue and subarachnoid CSF sodium concentrations are more sensitive to pathophysiological variations of P_BBB and PBBB′ than variations of P_BCSFB and PBCSFB′ within 30 min of the onset of the perturbations. However, P_BCSFB is the most sensitive model parameter, followed by P_BBB and PBBB′, in controlling brain tissue and subarachnoid CSF sodium levels within 3 h of the perturbation onset.

Maternal high-fat diet triggers metabolic syndrome disorders that are transferred to first and second offspring generations

A high-fat (H) diet increases metabolic disorders in offspring. However, there is great variability in the literature regarding the time of exposure, composition of the H diets offered to the genitors and/or offspring and parameters evaluated. Here, we investigated the effect of a H diet subjected to the genitors on different cardio-metabolic parameters on first (F1)- and second (F2)-generation offspring. Female Fischer rats, during mating, gestation and breast-feeding, were subjected to the H diet (G0HF) or control (G0CF) diets. Part of F1 offspring becomes G1 genitors for generating the F2 offspring. After weaning, F1 and F2 rats consumed only the C diet. Nutritional, biometric, biochemical and haemodynamic parameters were evaluated. G0HF genitors had a reduction in food intake but energy intake was similar to the control group. Compared with the control group, the F1H and F2H offspring presented increased plasma leptin, insulin and fasting glucose levels, dietary intake, energy intake, adiposity index, mean arterial pressure, sympathetic drive evidenced by the hexamethonium and insulin resistance. Our data showed that only during mating, gestation and breast-feeding, maternal H diet induced cardio-metabolic disorders characteristic of human metabolic syndrome that were transferred to both females and males of F1 and F2 offspring, even if they were fed control diet after weaning. This process probably occurs due to the disturbance in mechanisms related to leptin that increases energy intake in F1H and F2H offspring. The present data reinforce the importance of balanced diet during pregnancy and breast-feeding for the health of the F1 and F2 offspring.

Measurement of cations, anions, and acetate in serum, urine, cerebrospinal fluid, and tissue by ion chromatography

Accurate quantification of cations and anions remains a major diagnostic tool in understanding diseased states. The current technologies used for these analyses are either unable to quantify all ions due to sample size/volume, instrument setup/method, or are only able to measure ion concentrations from one physiological sample (liquid or solid). Herein, we adapted a common analytical chemistry technique, ion chromatography and applied it to measure the concentration of cations; sodium, potassium, calcium, and magnesium (Na⁺, K⁺, Ca²⁺, and Mg²⁺) and anions; chloride, and acetate (Cl⁻, ⁻OAc) from physiological samples. Specifically, cations and anions were measured in liquid samples: serum, urine, and cerebrospinal fluid, as well as tissue samples: liver, cortex, hypothalamus, and amygdala. Serum concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, and ⁻OAc (mmol/L): 138.8 ± 4.56, 4.05 ± 0.21, 4.07 ± 0.26, 0.98 ± 0.05, 97.7 ± 3.42, and 0.23 ± 0.04, respectively. Cerebrospinal fluid concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, and ⁻OAc (mmol/L): 145.1 ± 2.81, 2.41 ± 0.26, 2.18 ± 0.38, 1.04 ± 0.11, 120.2 ± 3.75, 0.21 ± 0.05, respectively. Tissue Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, and ⁻OAc were also measured. Validation of the ion chromatography method was established by comparing chloride concentration between ion chromatography with a known method using an ion selective chloride electrode. These results indicate that ion chromatography is a suitable method for the measurement of cations and anions, including acetate from various physiological samples.

Assessment of Cholesterol, Glycemia Control and Short- and Long-Term Antihypertensive Effects of Smooth Hound Viscera Peptides in High-Salt and Fructose Diet-Fed Wistar Rats

In this study, the antihypertensive activity of Purafect®-smooth hound viscera protein hydrolysate (VPH) and its peptide fraction with molecular weight (MW) below 1 kDa (VPH-I) was investigated. In addition, the lipase inhibitory activity, as well the anticoagulant potential, in vitro, were assessed. The antihypertensive effects of VPH and VPH-I were studied during 24 h (short-term effect) and 30 days (long-term effect) using high-salt (18% NaCl) and -fructose (10%) diet (HSFD)-induced hypertension. Data showed that, 4 h post-administration of VPH and VPH-I (200 mg/kg BW), the systolic blood pressure of rats was reduced by about 6 and 9 mmHg, respectively. These effects were similar to that obtained with Captopril (~9 mmHg at t = 4 h). On the other hand, exposing the rats to daily to HSFD, coupled to the administration of viscera peptides, was found to attenuate hypertension. In addition, the proteins' treatments were able to correct lipid and glycemic disorders, by reducing the total cholesterol and triglyceride contents and resorting to the plasma glucose level, compared to the HSFD group. Overall, the present findings demonstrated the preventive effect of VPH-peptides from hypertension complications, as a result of their biological properties.

[Na+] Increases in Body Fluids Sensed by Central Nax Induce Sympathetically Mediated Blood Pressure Elevations via H+-Dependent Activation of ASIC1a

Increases in sodium concentrations ([Na⁺]) in body fluids elevate blood pressure (BP) by enhancing sympathetic nerve activity (SNA). However, the mechanisms by which information on increased [Na⁺] is translated to SNA have not yet been elucidated. We herein reveal that sympathetic activation leading to BP increases is not induced by mandatory high salt intakes or the intraperitoneal/intracerebroventricular infusions of hypertonic NaCl solutions in Na_x-knockout mice in contrast to wild-type mice. We identify Na_x channels expressed in specific glial cells in the organum vasculosum lamina terminalis (OVLT) as the sensors detecting increases in [Na⁺] in body fluids and show that OVLT neurons projecting to the paraventricular nucleus (PVN) are activated via acid-sensing ion channel 1a (ASIC1a) by H⁺ ions exported from Na_x-positive glial cells. The present results provide an insight into the neurogenic mechanisms responsible for salt-induced BP elevations.

High salt induced hypertension leads to cognitive defect

Although increasing evidences suggest a relationship between hypertension and brain function for years, it is still unclear whether hypertension constitutes a risk factor for cognitive decline and its underlying mechanism. In the present study, an experimental animal model of hypertension simply by feeding rats with high salt diet was employed. We found that long-term high salt intake caused a marked increase of systolic blood pressure linked to a declined regional cerebral blood flow. Fear conditioning and morris water maze behavioral test revealed that high salt diet induced hippocampal dependent spatial reference memory deficits, while a decreased synaptogenesis without neuronal loss in hippocampus was observed in high salt treated rats. Furthermore, we found that high salt induced a decrease of intracellular calcium, which inactivated CaMK II and resulted in dephosphorylation of CREB at Ser133. These findings suggest a novel etiopathogenic mechanism of cognitive deficit induced by hypertension, which is initiated by high salt diet.