Male Spontaneously Hypertensive Rats Research Articles

Effects of Donepezil on Nonlinear Arterial Pressure and Pulse Interval Dynamics in Spontaneously Hypertensive Rats (SHR)

Objectives: This study aimed to evaluate the effects of donepezil, an anticholinesterase agent that potentiates parasympathetic function, in the nonlinear dynamics of blood pressure (BP) and pulse interval (PI) from spontaneously hypertensive rats (SHR). Entropy-based approaches which quantify the irregularity or unpredictability of time series were employed. Additionally, detrended fluctuation analysis (DFA) was applied to estimate the degree of self-similarity in the time series. We hypothesized that donepezil improves both entropy and DFA indices of BP and PI. Methods: Male SHR or Wistar-Kyoto (WKY) rats (5 weeks old) were implanted with subcutaneous osmotic mini-pumps for donepezil (DON) administration (1.4 mg/kg/day) or vehicle. At the end of the treatment (16 weeks), conscious WKY (N=12) and SHR treated with donepezil (N=8), or vehicle (N=9), had their BP directly recorded during 1h. Time series (15 min) from systolic BP and PI were generated and used to calculate sample (SampEn), fuzzy (FuzzyEn), and dispersion (DispEn) entropy, as well as DFA scale exponents in short (α1; 5≤n≤15), mid (α2; 20≤n≤100) and long (α3; 100≤n≤500) windows. The results are shown as mean ± SD. One-Way ANOVA, followed by Tukey’s post-test, evaluated differences between the WKY, SHR, and SHR+DON groups. Results: The data are displayed in the table. Lower PI DispEn was observed in SHR treated with DON compared to WKY. Entropy values of BP series were found smaller in SHR and SHR+DON compared to WKY rats. For DFA of the PI series, SHR+DON showed higher α1 compared to the WKY. Moreover, SHR displayed higher α3 when compared to the WKY. In the series of BP values, the results showed higher α2 and α3 in SHR compared to WKY. [Formula: see text] Conclusion: These findings showed that SHR exhibited lower BP entropy and higher DFA of BP and IP compared with WKY. However, donepezil did not prevent these changes of non-linear indices from BP and PI variability in SHR. Funding Sources: FAPESP, Process 2020/06043-7. CNPq, Process 306994/2021-6 and 423999/2021-4. FAEPA. CAPES. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mechanisms Involved in the Antihypertensive Effects of Arbequina Table Olives

The Mediterranean Diet is associated with antihypertensive properties and prevention of cardiovascular disease. This dietary pattern includes the intake of Olea europaea L. derivatives such as extra virgin olive oil and table olives, characterized by a high content of bioactive compounds. Recently, it has been demonstrated that the supplementation of Arbequina table olives (AO) reduces blood pressure (BP) in spontaneously hypertensive rats (SHR). The aim of the present study was to elucidate the possible mechanisms involved in the antihypertensive effects of AO. Consequently, we have studied different plasmatic biomarkers (angiotensin II, Ang II; malondialdehyde, MDA; interleukin 6, IL6; tumor necrosis factor α, TNFα) and the fecal microbiota composition. Experiments were performed using male SHR from 14 to 21 weeks of age. SHR strain was divided into a control (SHR-c) and a treated group (SHR-o) that received water or AO (3.85 g/kg) by gavage, respectively. At the end of the experiment, BP was measured using a non-invasive automatic analyzer; Ang II, IL6, and TNFα were determined by Elisa, and MDA by spectrophotometric analysis. Fecal microbiota was analyzed by sequencing 16S rRNA gene using the Illumina MiSeq platform. Data were analyzed by t-Student or the Mann–Whitney U test, and statistical significance was considered when p<0.05. AO supplementation decreased systolic and diastolic BP by approximately 19 mmHg in SHR-o with respect to SHR-c. The decrement in BP was accompanied by a decrease in MDA (39%) and Ang II (32%) in SHR-o without changes in the concentrations of the proinflammatory cytokines IL6 and TNFα. Moreover, regular AO intake induced changes in the microbiota associated with the normalization of BP. Our results showed variations in relative abundance in genera such as Akkermansia, Sutterella, and Peptoniphilus, that were well correlated with the decrease in BP, MDA, and Ang II. In conclusion, OA supplementation reduced oxidative stress and Ang II associated with changes in the fecal microbiota that may explain the antihypertensive effect elicited by consumption of the fruit of Olea europaea L. Supported by grants AGL2013-41188 & 2021SGR300. INSA Maria de Maeztu Unit of Excellence grant CEX2021-001234-M. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Increases of renal sodium transporters before and after the occurrence of the hypertension in spontaneously hypertensive rats

Background: Adult spontaneously hypertensive rats (SHR) have increases of renal sodium transporters associated with hypertension. It remains to be determined whether the increases of renal sodium transporters are precede by occurrence of hypertension and reflected by urine exosomal sodium transporters that may serve as non-invasive biomarkers for the effcacy of anti-hypertensive drugs. Methods: 1. Male WKY rats and SHRs were aged of 4, 7 and 10 weeks respectively (n=5/group). 2. Additional 3 sets of 10-week-old rat (n=5/group) were administered by a 7-day intraperitoneal injections of furosemide (NKCC2 inhibitor, 5mg/kg), hydrochlorothiazide (NCC2 inhibitor, 30mg/kg) and amiloride (ENaC inhibitor, 10mg/kg) respectively. 3. The systolic blood pressure (SBP) was measured with a catheter in carotid artery of rats under anesthesia. Tail-cuff methods were used to monitor the drug responses. 4. All rats were rationally fed 0.4% NaCl agar-gelled diet for 7 days. 5. Exosomes were extracted with ultracentrifuge from the urines. Results: SHRs (4 weeks) exhibited similar SBP. The renal NKCC2, the major apical sodium transporters in thick ascending limb, was more than doubled in SHRs (215±14 % of WKY, student t-test, p<0.05, same as below) while the other sodium transporters were normal. However, SHRs had a higher SBP than WKY at ages of 7 (157±10 vs 125±14, mmHg) and 10 weeks (192±8 vs 128±12). There were no differences for the all age groups in heart rate, body weight, urine volume, urine Na+ and Cl− excretion, and serum Cr, K+, Na+, and Cl− concentration between rat strains. At 10-weeks old, renal (161±24) and urine exosomal (159±21, corrected by UCr, same as below) NKCC2 were higher in SHR than WKY. Frusemide normalized SBP on day 1 (day 0: 190±18 vs 138±13; day 1: 149±13 vs 128±16) in SHR; Renal (129±9) and urine-exosomal (137±12) NCC were higher in SHR than WKY. Hydrochlorothiazide normalized SBP in SHR on day 1 (day 0: 206±4 vs 140±9; day 1: 159±11 vs 144±11). Renal (α:134±16; β:137±25) and urine-exosomal (α:153±13; β:158±12) ENaCs were higher in SHR than WKY. Amiloride diminished the difference in SBP between rat strains on day 1 (day 0: 188±18 vs 138±11; day 1: 164±16 vs 147±7). Conclusions: The increase of renal NKCC2 precedes the elevation of SBP in SHRs. Urine exosomal NKCC2, NCC, ENaCs may reflect their renal levels and be indicative of the corresponding inhibitors on the hypertension model. Natural Science Foundation of China 81970605. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cholinergic Stimulation Exerts Cardioprotective Effects and Alleviates Renal Inflammatory Responses after Acute Myocardial Infarction in Spontaneous Hypertensive Rats (SHRs).

In this investigation, we explored the effects of pharmacological cholinergic stimulation on cardiac function and renal inflammation following acute myocardial infarction (AMI) in spontaneously hypertensive rats (SHRs). Adult male SHRs were randomized into three experimental groups: sham-operated; AMI + Veh (infarcted, treated with vehicle); and AMI + PY (infarcted, treated with the cholinesterase inhibitor, pyridostigmine bromide (PY)-40 mg/kg, once daily for seven days). Rats were euthanized 7 or 30 days post-surgery. The clinical parameters were assessed on the day before euthanasia. Subsequent to euthanasia, blood samples were collected and renal tissues were harvested for histological and gene expression analyses aimed to evaluate inflammation and injury. Seven days post-surgery, the AMI + PY group demonstrated improvements in left ventricular diastolic function and autonomic regulation, and a reduction in renal macrophage infiltration compared to the AMI + Veh group. Furthermore, there was a notable downregulation in pro-inflammatory gene expression and an upregulation in anti-inflammatory gene expression. Analysis 30 days post-surgery showed that PY treatment had a sustained positive effect on renal gene expression, correlated with a decrease in biomarkers, indicative of subclinical kidney injury. Short-term cholinergic stimulation with PY provides both cardiac and renal protection by mitigating the inflammatory response after AMI.

Exercise-induced cardiac mitochondrial reorganization and enhancement in spontaneously hypertensive rats.

The myocardium is a highly oxidative tissue in which mitochondria are essential to supply the energy required to maintain pump function. When pathological hypertrophy develops, energy consumption augments and jeopardizes mitochondrial capacity. We explored the cardiac consequences of chronic swimming training, focusing on the mitochondrial network, in spontaneously hypertensive rats (SHR). Male adult SHR were randomized to sedentary or trained (T: 8-week swimming protocol). Blood pressure and echocardiograms were recorded, and hearts were removed at the end of the training period to perform molecular, imaging, or isolated mitochondria studies. Swimming improved cardiac midventricular shortening and decreased the pathological hypertrophic marker atrial natriuretic peptide. Oxidative stress was reduced, and even more interesting, mitochondrial spatial distribution, dynamics, function, and ATP were significantly improved in the myocardium of T rats. In the signaling pathway triggered by training, we detected an increase in the phosphorylation level of both AKT and glycogen synthase kinase-3 β, key downstream targets of insulin-like growth factor 1 signaling that are crucially involved in mitochondria biogenesis and integrity. Aerobic exercise training emerges as an effective approach to improve pathological cardiac hypertrophy and bioenergetics in hypertension-induced cardiac hypertrophy.

Characterization of Diclofenac-induced Renal Damage in Normotensive and Hypertensive Rats: A Comparative Analysis.

Diclofenac is the non-steroidal anti-inflammatory drug (NSAID) mostly prescribed worldwide, but it is highly associated with hypertension and acute kidney injury. Despite that, little information is available about the renal effects of diclofenac in hypertensive individuals, which led us to carry out this comparative study between the renal effects of this NSAID in normotensive (NTR) and spontaneously hypertensive rats (SHR). Male Wistar NTR and SHR were orally treated with vehicle (V: 10 mL/kg) or diclofenac sodium (D: 100 mg/kg) once a day for 3 days. Urine volume, electrolytes excretion (Na+, K+, Cl-, and Ca2+), urea, creatinine, pH, and osmolarity were evaluated. Furthermore, blood samples and renal tissue were collected to perform biochemical and histological analysis. Diclofenac increased the renal corpuscle and bowman's space in the SHR, while no microscopic changes were observed in the renal tissue of NTR. Regarding the urinary parameters, diclofenac reduced urine volume, pH, osmolarity, and all electrolytes excretion, followed by decreased urea and creatinine levels in both lineages. Moreover, it also induced hyponatremia, hypokalemia, and hypocalcemia in SHR, while reduced glutathione-S-transferase activity, lipid hydroperoxides, and nitrite levels in renal tissue. The data presented herein demonstrated that diclofenac induces renal damage and impaired renal function in both NTR and SHR, but those effects are exacerbated in SHR, as seen by the histological changes and electrolytes balance disturbance, therefore, reinforcing that diclofenac may increase the risks of cardiovascular events in hypertensive patients.

Effect of Saccharina japonica Intake on Blood Pressure and Gut Microbiota Composition in Spontaneously Hypertensive Rats.

It was reported that the consumption of Saccharina japonica (SJ) lowers blood pressure (BP) in hypertensive rats. Hypertension is related to gut microbiota, and hypertensive patients develop dysbiosis. It was reported that the intake of dietary fiber and polysaccharides contained in SJ changes gut microbiota and increases short-chain fatty acids (SCFAs). The present study examined the effect of BP lowering by SJ in spontaneously hypertensive rats (SHRs) and observed changes in gut microbiota composition and SCFAs concentration. Male SHRs and Wistar Kyoto rats (WKYs) were fed a diet containing 5% SJ or a control diet for six weeks. We measured systolic BP (SBP) weekly, as well as mean arterial BP (MAP), the 16S rRNA gene, and SCFAs in the cecal contents at the end of the period. As a result, the intake of SJ significantly decreased SBP and MAP in SHRs. As well, it significantly changed the microbial diversity by altering the gut microbiota composition. Particularly, it increased the abundance of Bacteroides acidifaciens, which may be associated with the antihypertensive effect of SJ. Thus, SJ intake suppressed the increase in BP and altered the gut microbiota composition, although it did not significantly change the SCFAs concentration in the cecal contents.

Mesenteric artery smooth muscle cells from hypertensive rats have increased microtubule acetylation.

The dynamic nature of the microtubule network is dependent in part by post-translational modifications (PTMs) - particularly through acetylation, which stabilizes the microtubule network. Whether PTMs of the microtubule network in vascular smooth muscle cells (VSMCs) contribute to the pathophysiology of hypertension is unknown. The aim of this study was to determine the acetylated state of the microtubule network in the mesenteric arteries of spontaneously hypertensive rats (SHR). Experiments were performed on male normotensive rats and SHR mesenteric arteries. Western blotting and mass spectrometry determined changes in tubulin acetylation. Wire myography was used to investigate the effect of tubacin on isoprenaline-mediated vasorelaxations. Isolated cells from normotensive rats were used for scanning ion conductance microscopy (SICM). Mass spectrometry and Western blotting showed that tubulin acetylation is increased in the mesenteric arteries of the SHR compared with normotensive rats. Tubacin enhanced the β-adrenoceptor-mediated vasodilatation by isoprenaline when the endothelium was intact, but attenuated relaxations when the endothelium was denuded or nitric oxide production was inhibited. By pre-treating vessels with colchicine to disrupt the microtubule network, we were able to confirm that the effects of tubacin were microtubule-dependent. Using SICM, we examined the cell surface Young's modulus of VSMCs, but found no difference in control, tubacin-treated, or taxol-treated cells. Acetylation of tubulin at Lys40 is elevated in mesenteric arteries from the SHR. Furthermore, this study shows that tubacin has an endothelial-dependent bimodal effect on isoprenaline-mediated vasorelaxation.

Forgotten Circulation: Reduced Mesenteric Venous Capacitance in Hypertensive Rats Is Improved by Decreasing Sympathetic Activity.

The mesenteric venous reservoir plays a vital role in mediating blood volume and pressure changes and is richly innervated by sympathetic nerves; however, the precise nature of venous sympathetic regulation and its role during hypertension remains unclear. We hypothesized that sympathetic drive to mesenteric veins in spontaneously hypertensive (SH) rats is raised, increasing mean circulatory filling pressure (MCFP), and impairing mesenteric capacitance. Arterial pressure, central venous pressure, mesenteric arterial, and venous blood flow were measured simultaneously in conscious male Wistar and SH rats. MCFP was assessed using an intraatrial balloon. Hemodynamic responses to volume changes (±20%) were measured before and after ganglionic blockade and carotid body denervation. Sympathetic venoconstrictor activity was measured in situ. MCFP in vivo (10.8±1.6 versus 8.0±2.1 mm Hg; P=0.0005) and sympathetic venoconstrictor drive in situ (18±1 versus 10±2 µV; P<0.0001) were higher in SH rats; MCFP decreased in SH rats after hexamethonium and carotid body denervation (7.6±1.4; P<0.0001 and 8.5±1.0 mm Hg; P=0.0045). During volume changes, arterial pressure remained stable. With blood loss, net efflux of blood from the mesenteric bed was measured in both strains. However, during volume infusion, we observed net influx in Wistar (+2.3±2.6 mL/min) but efflux in SH rats (-1.0±1.0 mL/min; P=0.0032); this counterintuitive efflux was abolished by hexamethonium and carotid body denervation (+0.3±1.7 and 0.5±1.6 mL/min, respectively). In SH rats, excessive sympathetic venoconstriction elevates MCFP and reduces capacitance, impairing volume buffering by mesenteric veins. We propose selective targeting of mesenteric veins through sympathetic drive reduction as a novel therapeutic opportunity for hypertension.

Aliskiren-Loaded Nanoparticles Downregulate (Pro)renin Receptor and ACE Gene Expression in the Heart of Spontaneously Hypertensive Rats: Effect on NADPH Oxidase.

We aimed to determine effects of aliskiren, a direct renin inhibitor, loaded onto polymeric nanoparticles on the (pro)renin receptor (Atp6ap2), angiotensin II type 1 receptor (Agtr1), and angiotensin-converting enzyme (ACE) gene expression in the heart of spontaneously hypertensive rats (SHR). Twelve-week-old male SHRs were divided into an untreated group and groups treated with powdered aliskiren or aliskiren-loaded nanoparticles (25 mg/kg/day). After three weeks, the accumulation of aliskiren, distribution of polymeric nanoparticles, gene expression of Atp6ap2 and Agtr1 receptors and ACE, and protein expression of NADPH oxidase along with the conjugated diene (CD) concentration were analyzed. The accumulation of aliskiren in the heart was higher in the aliskiren-loaded nanoparticle group than in the powdered group. The fluorescent signals of nanoparticles were visible in cardiomyocytes, vessel walls, and erythrocytes. Aliskiren-loaded nanoparticles decreased the gene expression of Atp6ap2 and ACE, while not affecting Agtr1. Both forms of aliskiren decreased the protein expression of NADPH oxidase, with a more pronounced effect observed in the aliskiren-loaded nanoparticle group. CD concentration was decreased only in the aliskiren-loaded nanoparticle group. We hypothesize that aliskiren-loaded nanoparticle-mediated downregulation of Atp6ap2 and ACE may contribute to a decrease in ROS generation with beneficial effects in the heart. Moreover, polymeric nanoparticles may represent a promising tool for targeted delivery of aliskiren.

Differential expression of alpha-synuclein in the hippocampus of SHR and SLA16 isogenic rat strains

Two inbred strains, Lewis (LEW) and Spontaneously Hypertensive Rats (SHR), are well-known for their contrasting behavior related to anxiety/emotionality. Studies with these two strains led to the discovery of the Quantitative Trait Loci (QTL) on chromosome 4 (Anxrr16). To better understand the influences of this genomic region, the congenic rat strain SLA16 (SHR.LEW-Anxrr16) was developed. SLA16 rats present higher hyperactivity/impulsivity, deficits in learning and memory, and lower basal blood pressure than the SHR strain, even though genetic differences between them are only in chromosome 4. Thus, the present study proposed the alpha-synuclein and the dopaminergic system as candidates to explain the differential behavior of SHR and SLA16 strains. To accomplish this, beyond the behavioral analysis, we performed (I) the Snca gene expression and (II) quantification of the alpha-synuclein protein in the hippocampus (HPC), prefrontal cortex (PFC), and striatum (STR) of SHR and SLA16 strains; (III) sequencing of the 3′UTR of the Snca gene; and (IV) evaluation of miRNA binding in the 3′UTR site. A Single Nucleotide Polymorphism (SNP) was identified in the 3′UTR of the Snca gene, which exhibited upregulation in the HPC of SHR compared to SLA16 females. Alpha-synuclein protein was higher in the HPC of SHR males compared to SLA16 males. The results of this work suggested that differences in alpha-synuclein HPC content could be influenced by miRNA regulation and associated with behavioral differences between SHR and SLA16 animals.

Sustained activation of 12/15 lipoxygenase (12/15 LOX) contributes to impaired renal recovery post ischemic injury in male SHR compared to females

BackgroundAcute kidney injury (AKI) due to ischemia-reperfusion (IR) is a serious and frequent complication in clinical settings, and mortality rates remain high. There are well established sex differences in renal IR, with males exhibiting greater injury following an ischemic insult compared to females. We recently reported that males have impaired renal recovery from ischemic injury vs. females. However, the mechanisms mediating sex differences in renal recovery from IR injury remain poorly understood. Elevated 12/15 lipoxygenase (LOX) activity has been reported to contribute to the progression of numerous kidney diseases. The goal of the current study was to test the hypothesis that enhanced activation of 12/15 LOX contributes to impaired recovery post-IR in males vs. females.Methods13-week-old male and female spontaneously hypertensive rats (SHR) were randomized to sham or 30-minute warm bilateral IR surgery. Additional male and female SHR were randomized to treatment with vehicle or the specific 12/15 LOX inhibitor ML355 1 h prior to sham/IR surgery, and every other day following up to 7-days post-IR. Blood was collected from all rats 1-and 7-days post-IR. Kidneys were harvested 7-days post-IR and processed for biochemical, histological, and Western blot analysis. 12/15 LOX metabolites 12 and 15 HETE were measured in kidney samples by liquid chromatography–mass spectrometry (LC/MS).ResultsMale SHR exhibited delayed recovery of renal function post-IR vs. male sham and female IR rats. Delayed recovery in males was associated with activation of renal 12/15 LOX, increased renal 12-HETE, enhanced endoplasmic reticulum (ER) stress, lipid peroxidation, renal cell death and inflammation compared to females 7-days post-IR. Treatment of male SHR with ML355 lowered levels of 12-HETE and resulted in reduced renal lipid peroxidation, ER stress, tubular cell death and inflammation 7-days post-IR with enhanced recovery of renal function compared to vehicle-treated IR male rats. ML355 treatment did not alter IR-induced increases in plasma creatinine in females, however, tubular injury and cell death were attenuated in ML355 treated females compared to vehicle-treated rats 7 days post-IR.ConclusionOur data demonstrate that sustained activation 12/15 LOX contributes to impaired renal recovery post ischemic injury in male and female SHR, although males are more susceptible on this mechanism than females.

Subdiaphragmatic Vagal Nerve Stimulation Attenuates the Development of Hypertension and Alters NTS Transcriptional Networks in the SHR.

Augmented vagal signaling may be therapeutic in hypertension. Most studies to date employed stimulation of the cervical vagal branches. Here, we investigated the effects of chronic intermittent electric stimulation of the ventral subdiaphragmatic vagal nerve branch (sdVNS) on long term blood pressure (BP), immune markers, and gut microbiota in the spontaneously hypertensive rat (SHR), a rodent model of hypertension characterized by vagal dysfunction, gut dysbiosis and low-grade inflammation. We evaluated the effects of sdVNS on transcriptional networks in the nucleus of the solitary tract (NTS), a major cardioregulatory brain region with direct gut vagal projections. Male juvenile SHR were implanted with radiotelemetry transmitters and vagal nerve cuffs for chronic intermittent electric sdVNS, applied three times per day for seven consecutive weeks followed by one week of no stimulation. BP was measured once a week using telemetry in the sdVNS group as well as the age-matched Sham-stimulated SHR controls. At endpoint, colonic and circulating inflammatory markers and corticosterone, and circulating catecholamines were investigated. Bacterial 16s sequencing measured gut bacterial abundance and composition. RNAseq evaluated the effects of sdVNS on transcriptional networks in the NTS. SHRs that received sdVNS exhibited attenuated development of hypertension compared to the Sham. No changes in peripheral inflammatory markers, corticosterone or catecholamines, and no major differences in gut bacterial diversity and composition were observed following sdVNS, apart from decreased abundance of Defluviitaleaceale bacterium detected in the sdVNS SHR compared to the Sham. RNAseq revealed significant sdVNS-dependent modulation of select NTS transcriptional networks, including catecholaminergic and corticosteroid networks.

Memory deficits and hippocampal cytokine expression in a rat model of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder characterized by hyperactivity, impulsivity, inattention, and deficits in working memory and time perception. While animal models have advanced our neurobiological understanding of this condition, there are limited and inconsistent data on working and elapsed time memory function. Inflammatory signaling has been identified as a key factor in memory and cognitive impairments, but its role in ADHD remains unclear. Additionally, the disproportionate investigation of male subjects in ADHD research has contributed to a poor understanding of the disorder in females. This study sought to investigate the potential connections between memory, neuroimmunology, and ADHD in both male and female animals. Specifically, we utilized the spontaneously hypertensive rat (SHR), one of the most extensively studied animal models of ADHD. Compared to their control, the Wistar-Kyoto (WKY) rat, male SHR are reported to exhibit several behavioral phenotypes associated with ADHD, including hyperactivity, impulsivity, and poor sustained attention, along with impairments in learning and memory. As the hippocampus is a key brain region for learning and memory, we examined the behavior of male and female SHR and WKY rats in two hippocampal-dependent memory tasks. Our findings revealed that SHR have delay-dependent working memory deficits that were similar to, albeit less severe than, those seen in hippocampal-lesioned rats. We also observed impairments in elapsed time processing in female SHR, particularly in the discrimination of longer time durations. To investigate the impact of inflammatory signaling on memory in these rats, we analyzed the levels of several cytokines in the dorsal and ventral hippocampus of SHR and WKY. Although we found some sex and genotype differences, concentrations were generally similar between groups. Taken together, our results indicate that SHR exhibit deficits in spatial working memory and memory for elapsed time, as well as some differences in hippocampal cytokine concentrations. These findings contribute to a better understanding of the neurobiological basis of ADHD in both sexes and may inform future research aimed at developing effective treatments for the disorder. Nonetheless, the potential mediating role of neuroinflammation in the memory symptomatology of SHR requires further investigation.

Acupuncture Alleviates Chronic Ischemic White Matter Injury in SHR Rats via JNK-NMDAR Circuit.

To study the protective mechanism of acupuncture at "Jiangya Recipe" on chronic ischemic white matter injury in spontaneously hypertensive rats (SHR) and the regulation of Jun N-terminal kinase-N-methyl-D-aspartate receptor (JNK-NMDAR) loop. A hypertensive white matter injury model was established in 46 male SHR rats aged 11 weeks by bilateral common carotid artery tapering (SHR-2VGO). In the SHR sham operation group, only bilateral common carotid arteries were isolated and in the SHR-2VGO modeling group, 36 rats were used for microcoil spring clip implantation to narrow the common carotid arteries and then, after 2 weeks of modeling, rats with impaired motor function were removed, and SHR-2VGO rats with successful final models were randomly divided into the model group, JNK blocking group, and acupuncture group. The sham operation group, model group, and JNK blocking group underwent the same grasping fixation, and the acupuncture group received acupuncture at acupoints "Jiangya Fang" once daily. In the JNK blocker group, an injection cannula was implanted into the lateral ventricle and sp600125 was injected into the lateral ventricle at 4.5 ul/day for 4 weeks. One week after the end of the intervention, white matter lesions were detected by MRI DWI and T2 imaging, and the learning and memory ability of rats was tested by Y-Maze and Passive Avoidance. Myelin density was detected by luxol fast blue (LFB) staining, also axon arrangement, myelin integrity, and thickness of neurons were detected by electron microscopy; neuronal morphology and the number of Nissl bodies in the hippocampus were detected by Nissl staining, dendritic spine density changes were detected by Golgi staining, and JNK, NMDAR1, and N-methyl-D-receptor 2B (NMDAR2B) in DG, CA3 region of hippocampus were detected by immunohistochemistry, protein expression of p-JNK/JNK, p-NMDAR1/NMDAR1, NMDAR2B, GSK3β protein expression in the fimbria of hippocampus was detected by Western blot. The Y maze test of SHR-2VGO+Acu and SHR-2VGO+ sp600125 group showed that the spontaneous alternating reaction rate increased significantly. At the same time, the incubation period increased significantly and the number of errors decreased significantly in Passive Avoidance. MRI T2WI showed that the white matter high signal of the corpus callosum, internal capsule and hippocampal fimbria in the SHR-2VGO+ sp600125 and SHR-2VGO+Acu groups was significantly lower than that in the SHR-2VGO model group, and the striatum and anterior commissure were not obvious. DWI showed that the SHR-2VGO model group had scattered high signal and limited diffusion movement in both the internal capsule and striatum, but the difference between groups was not obvious. Compared with SHR-2VGO rats, LFB staining of SHR-2VGO + sp600125 and SHR-2VGO +Acu groups showed significant relaxation of myelin porosity in corpus callosum, striatum, inner capsule, anterior commissure and hippocampal fimbria, and electron microscopy showed improved axonal myelin integrity and thickness in corpus callosum region. Also, the number of blue patchy Nissl bodies increased, and the number and complexity of dendritic spines increased significantly in Golgi staining. Immunohistochemical detection showed that JNK levels in DG and CA3 region were increased and NMDAR1 and NMDAR2B levels were decreased in SHR-2VGO+Acu and SHR-2VGO+ sp600125 groups. Meanwhile, protein expressions of GSK3β, NMDAR1/p-NMDAR1 and NMDAR2B in fimbria of hippocampus were increased, and JNK/P-JNK protein expression decreased. Acupuncture can increase the density and thickness of myelin sheath in white matter areas of corpus callosum, anterior commissure and hippocampal fimbria, increase the number and length of hippocampal neuronal dendrites, and improve hypertensive white matter injury and cognitive decline through JNK-NMDAR pathway.

Sex-Specific Responses to Tacrolimus and Mycophenolate Mofetil in Spontaneously Hypertensive Rats

In recent decades, the roles of tacrolimus and mycophenolate mofetil (MMF) in hypertension have been under discussion. However, the question of whether there are sex-specific responses to these agents has not received enough attention. Aim: To evaluate sex-specific differences in the responses to tacrolimus and mycophenolate mofetil in female (F) and male (M) spontaneously hypertensive rats (SHRs) and evaluate whether T cells contribute to mean arterial pressure (MAP) changes. Methods: Male and female SHRs received either tacrolimus or MMF for 14 days. The rats were implanted with radiotelemeters. MAP was measured chronically; then, circulating and renal infiltrated CD4+, CD8+, T helper 17 (Th17), and T regulatory (Treg) cells were quantified using flow cytometry. Key Findings: Tacrolimus increased MAP only in males, and it decreased CD4+ and CD8+ T cells in both males and females (p &lt; 0.05). The tacrolimus-induced reduction of renal CD4+ and Treg cells was more profound in males. MMF reduced MAP and circulating and renal CD4+ and CD8+ T cells in the male and female rats. MMF also decreased Th17 and Treg cells in both sexes, but the decrease in Th17 was higher in males (p &lt; 0.05) and the reduction in Treg cells was higher in females (p &lt; 0.05). Our findings indicate that the effects of tacrolimus and MMF on renal T cell subsets are sex-specific. Significance: Targeting T cells in hypertension using therapeutic agents may have different effects on men and women; so, the management of hypertension and post-transplant hypertension using these agents should be specified by gender.

Additional effects of combination therapy of antihypertensive medication on aortic elastic properties beyond blood pressure lowering effect in spontaneously hypertensive rats

Abstract Background Combination therapy in the treatment of hypertension provides better therapeutic efficacy, improved tolerability by lowering the dose and reduced potential for side effects than monotherapy. Especially, combinations of calcium channel blocker (CCB), angiotensin receptor blocker (ARB) or diuretics (thiazide) are generally effective and well tolerated regimen in antihypertensive treatment. However, we have focused more on the antihypertensive power of the combination therapy rather than the effect on the vessel itself. Purpose The purpose of this study is to determine the efficacy of antihypertensive medications as ARB and CCB and its combination with or without thiazide on the aortic structural and functional properties beyond the effect of blood pressure (BP) lowering. Methods Fourteen-week-old male spontaneous hypertensive rats were randomly divided into 5 groups, and treated with 1) vehicle (V), 2) amlodipine besylate (A), 3) olmesartan (O), 4) combined amlodipine and olmesartan (AO) or 5) combined amlodipine, olmesartan and thiazide (AOD), respectively. After 8 weeks of treatment, hemodynamic parameters and structural and functional properties of aorta as intima-media thickness (IMT) and velocity vector imaging (VVI) parameters of aorta including fractional area change (FAC), circumferential strain (CS) and strain rate (CSR) were assessed in each group and collagen contents of aorta were quantified as well. Results During the study period, systolic and diastolic BP were serially decreased in all treatment groups. Especially, AOD group showed lowest systolic and diastolic BP levels and also showed smallest IMT and vessel area and highest elasticity (FAC and CS) among the other groups (p&amp;lt;0.01) at 8 weeks (Table 1). In histologic analysis, collagen contents of aorta in all treatment groups showed significant associations with BP, IMT and VVI parameters (FAC, CS, CSR) (p&amp;lt;0.05), respectively. Particularly, aorta of AO and AOD groups showed significantly lower levels of collagen contents than that of control group. (p&amp;lt; 0.05) (Figure 1) Conclusion(s) Beyond the BP lowering effect, combination of amlodipine and olmesartan with or without thiazide minimize structural changes and shows better protection for the progression of arteriosclerosis than individual monotherapy in treatment of hypertension.Table 1Figure 1

Effects of adolescent methylphenidate administration on methamphetamine conditioned place preference in an animal model of attention-deficit/hyperactivity disorder: Examination of potential sex differences

BackgroundIndividuals with attention-deficit/hyperactivity disorder (ADHD) are more likely to be diagnosed with a substance use disorder; however, the effects of long-term psychostimulant treatment on addiction are mixed. Preclinical studies are useful for further elucidating the relationship between ADHD and addiction-like behaviors, but these studies have focused on male subjects only. The goal of the current study was to determine if early-life administration of methylphenidate (MPH) augments methamphetamine (METH) conditioned place preference (CPP) and/or potentiates reinstatement of CPP in both male and female rats. MethodsMale and female spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) received either MPH (1.5mg/kg; p.o.) or vehicle (1.0ml/kg) during adolescence (postnatal day [PND] ~29–57). Two weeks after cessation of MPH treatment, rats were tested for METH CPP (1.0mg/kg or 2.0mg/kg; s.c.). Rats were then given extinction sessions. Once rats met extinction criteria, they were tested for reinstatement of CPP following a priming injection of METH (0.25mg/kg; s.c.). ResultsAll groups developed METH CPP, except vehicle-treated SHR males and vehicle-treated WKY females conditioned with the higher dose of METH (2.0mg/kg). Female SHRs treated with MPH showed greater reinstatement of METH CPP compared to female SHRs treated with vehicle. Adolescent MPH treatment did not augment the locomotor-stimulant effects of METH in adulthood. ConclusionsThese results demonstrate the importance of considering biological sex when prescribing psychostimulant medications for ADHD as long-term MPH administration may increase the risk of continued drug use in females with ADHD following a period of abstinence.

Abstract 096: Effects Of Chronic Hypertension And Sex On Spatial Reference And Working Memory

Chronic hypertension is a primary risk factor of vascular dementia. The hippocampus is a brain region critical to learning and memory and is highly susceptible to hypoxia/ischemia. Here, we investigated how chronic hypertension affects two different types of memory function, and whether one sex is more susceptible to hypertension-induced memory impairment. Memory function in adult male and female SHR (spontaneously hypertensive rats) and normotensive Wistar rats was tested using two behavioral tasks (n=6/group). The radial arm maze (RAM) tested reference memory that is largely hippocampal-dependent by measuring the time it took to retrieve rewards from three baited arms during daily 10 min sessions. A continuous y maze task was used to calculate alternation index and determine working memory that is cortico-hippocampal-dependent. Data are mean±SEM and comparisons made via a two-way ANOVA with a post-hoc Tukey test. In the RAM task, female rats had steeper learning curves than males as they completed the task in less time with each session (Fig 1). There was a significant interaction between sex and hypertension in the y maze task (F (1,20) =13.26, p=0.002). Working memory was impaired in female SHR, with a lower alternation index (index=0.60±0.03) than Wistar rats (index=0.74±0.03). However, male SHR that had a higher alternation index of 0.75±0.02 compared to 0.58±0.6 in male Wistar rats. Overall, females had stronger reference memory than males regardless of hypertension. Working memory was differentially affected in male and female SHR, suggesting sex differences in the susceptibility of different brain regions and types of memory to hypertension-induced dysfunction.

Abstract P139: Gender Affirming Hormone Therapy In The Hypertensive Male Rat Has Associated Effects On Cardiovascular Health

Transgender females ( TGF ) are born biologically male, but identify as female. TGFs undergo Gender-Affirming Hormone Therapy ( GAHT ) to match their physical and sex characteristics with their perceived gender. Several studies indicate that GAHT is associated with increased cardiovascular ( CV ) risk. Previously, we reported that GAHT, 17β-Estradiol ( E2 ) supplementation with androgen suppression, in the normotensive male Sprague Dawley ( SD ) rat is associated with loss of lean mass and increased markers of CV risk. Yet, the effect of GAHT in the presence of preexisting hypertension and renal injury is unknown. Thus, this study tested the hypothesis that GAHT in the male spontaneous hypertensive rat ( SHR ) is associated with increased CV and renal risk. Methods: Male SHRs were randomly assigned to 2 groups: Control (n=4) and E2 [5 mg/day, pellet sc, replaced every 3 weeks, n=6]. E2 was initiated at 19 weeks of age at a dose to suppress endogenous testosterone coupled to elevated E2. Results: ( Table ) At 49 weeks of age (equivalent to a 40 year old man), body weight and total lean mass (EchoMRI) were significantly decreased in E2 SHR; as previously observed in E2 SD. Yet, total fat mass (EchoMRI) was significantly decreased in E2 SHR; moreover, 24 hour urinary proteinuria and cystatin C (ELISA) were also significantly decreased. Hypertension and renal injury are androgen-dependent in male SHR. Thus, despite the increase in E2 in the male SHR, androgen suppression induced by GAHT was renoprotective. Further studies will determine relevance of the SHR as a model of GAHT and explore long-term effects of E2.