Aged Male Rats Research Articles

Muscimol inactivation of dorsal striatum in young and aged male rats does not affect paired associates learning performance.

Improving cognitive health for older adults requires understanding the neurobiology of age-related cognitive decline and the mechanisms underlying preserved cognition in old age. During spatial learning tasks, aged humans and rodents shift navigation preferences in favor of a stimulus-response learning strategy. This has been hypothesized to result from competitive interactions of the caudate nucleus/dorsal striatum (DS) memory system with the hippocampus (HPC)-dependent spatial/allocentric memory system. In support of this hypothesis, a recent study reported that inactivation of the DS in aged rodents rescued HPC-dependent spatial learning on a T-maze (Gardner, Gold, & Korol, 2020). Currently, it is unclear whether a shift from HPC-dependent to DS-dependent behavior also contributes to age-related cognitive decline outside of spatial learning and memory. To test the hypothesis that inactivation of the DS can restore age-related cognitive function outside of spatial behavior, the present study bilaterally inactivated the DS of young (n = 8) and aged (n = 7) rats during visuospatial paired associates learning (PAL). This study found that inactivation of the DS did not alter PAL performance in young or aged rats, but did alter a positive control, DS-dependent spatial navigation task. This observation suggests that elevated DS activity does not play a role in the decline of HPC-dependent PAL performance in aged male rats. Given the persistent tendencies of aged rodents toward DS-dependent learning, it will be worthwhile to explore further the coordination dynamics between the HPC and DS that may contribute to age-related cognitive decline. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Chronic Exposure with 5‐Alpha Reductase Inhibitor Ameliorates Anxiety and Depression‐like Behaviors By Reducing Systemic Oxidative Stress in D‐galactose‐Induced Aging Male Rats

AbstractBackgroundThe most common geriatric psychiatric disorders are anxiety and depression. The 5‐alpha reductase inhibitor (5‐ARIs), finasteride (Fin), is a standard medication used to treat benign prostatic hyperplasia (BPH), that often occurs in the elderly. However, the effects of Fin on mental health in aged population are still unclear. D‐galactose (D‐gal)‐induced aging has been recognized worldwide, as a model to mimic natural aging in rodents. Therefore, we investigated the effect of Fin on anxiety and depression‐like behaviors in D‐gal‐induced aging male rats.MethodTwenty‐male Wistar rats (8‐week‐old) were randomly divided into two groups (n = 10/group) to receive either vehicle as control or D‐gal (150 mg/kg/day via subcutaneous injection) for 18 weeks. At week 13, rats in each group were divided into two subgroups (n = 5/subgroup) in order to receive either vehicle (drinking water) or Fin (5 mg/kg/day) via oral gavage. At the end of the treatment, elevated‐plus maze (EPM), and splash test (ST) were performed for quantifying anxiety and depression‐like behaviors, while open‐field test (OFT) to determine locomotor activity. In addition, blood in each rat was collected for determining the metabolic profiles.ResultD‐gal‐treated rat showed no effect on metabolic disturbance, but increased systemic oxidative stress (Figure 1A‐C). Anxiety and depression‐like behavior were observed in D‐gal‐treated rats, as indicated by a decrease % preference index in the open arm of EPM and grooming time in ST (Figure 1D‐E). Fin‐treated control rats demonstrated hypercholesterolemia (Figure 1A‐B), and depression‐like behavior was observed (Figure 1E). Anxiety and depression‐like behaviors were attenuated in Fin‐treated D‐gal rats (Figure 1D‐E). Regarding the locomotor activity, no significant difference was found among all groups. (Figure 1F).ConclusionFIN exposure induced metabolic disturbance, and depression‐like behaviors in male rats. In contrast, Fin ameliorated anxiety and depression‐like behaviors in D‐gal‐induced aging rat, which may due to a reducing systemic oxidative stress. The findings in this study provide information for future clinical applications such as the use of Fin for therapeutic approach for anxiety/depression‐like behaviors in the elderly. However, caution is advised when using Fin in young men since it may induce depressive‐like behaviors.

Inflammatory and metabolic responses in the aging rat brain

AbstractBackgroundThe brain is an energetically demanding organ that mostly relies on glucose oxidation to sustain its sophisticated networks. Transcriptomic studies suggest metabolic‐related genes are downregulated in the aging brain but inflammation‐related genes are highly upregulated. Astrocytes are key mediators of brain inflammation and metabolism. Yet, the relationship between inflammatory signals and energy substrates consumption in the aging brain remains unclear. To address this question, we investigated the response of the young and aged rat brain metabolism to a nonsteroidal anti‐inflammatory (NSAID) drug.MethodFive young adults (4 mo), and five aged (24 mo) male Wistar rats were scanned using positron emission microtomography with 18F‐fluorodeoxyglucose ([18F]FDG‐PET). Scans were done under basal conditions or after three‐day treatment with 5mg/kg ketoprofen (i.p.), an NSAID known to cross the blood‐brain barrier. Standard uptake values ratios (SUVr, pons as reference) were calculated for the main brain regions. Synaptosome and total mitochondria preparations from the cortex had their oxygen consumption rates measured in an Oroboros Instrument, using a SUIT protocol. Results were analyzed by t‐test, with statistical significance P < 0.05.ResultUnder basal conditions, glucose uptake showed no differences between young and aged rats. After ketoprofen treatment, clusters of glucose hypermetabolism appeared in the cortex and hippocampus of the adult but not the aged brain. Synaptosomal and mitochondrial preparations did not present differences in ATP‐linked, maximal, or leak respiration between groups under basal conditions. However, aged synaptosomes (t = 3.417, p = 0.0112) and total mitochondria (t = 3.131, p = 0.0166) presented higher respiratory coupling ratios.ConclusionWe previously showed that [18F]FDG‐PET signal highly depends on astrocyte function. The lack of response to ketoprofen in aged rats may be related to astrocyte dysfunction in aging. As a counter‐response to the aging process, the brain mitochondria are highly coupled, keeping the system as efficient as necessary. Our findings indicate that brain metabolism might not be coupled to inflammation in the aged rat brain. Still, we identified a remarkable plasticity of the mitochondria, which can sustain physiological responses despite the aging process.

Effect of aqueous extract of Indigofera tinctoria (Linn) on aging-induced inflammation and its associated left ventricular hypertrophy and fibrosis in the rat.

The aim of the present study is to investigate the ameliorative potential of the aqueous extract of Indigofera tinctoria (IT) in aging-induced inflammation and its associated cardiac hypertrophy and fibrosis. Young (3-month-old) and aged (24-26-month-old) male Wistar albino rats were grouped into young control, aged control, aged + IT, and young + IT. The animals in the supplementary groups received 200mg/kg BWT of aqueous extract of IT orally once a day for 21days. Aged animals showed prolonged QT interval and increased weight and volume of the heart with a thickening ventricular wall. Infiltration of leukocytes and increased cardiomyocyte diameter and decreased numerical density along with cardiomyocyte apoptosis and increased collagen accumulation were also seen in aged myocardium when compared to the young. The expression profile of various pro-inflammatory cytokines such as IL-6, IL-1β, TNF-α, NFκB, and iNOS was increased with a concomitant reduction in IL-10 expression in the aged compared to the young. In addition, a marked increase in ROS generation, TGF-β, and α-SMA levels is evident in the aged myocardium. These pathological changes were greatly reversed in aged animals supplemented with IT. Furthermore, the aged + IT group showed repression of pro-inflammatory markers with a subsequent increase in IL-10 expression. Contrarily, no marked changes were observed between young and young + IT groups. Taken together, it is concluded that the aqueous extract of Indigofera tinctoria suppresses cardiac fibrosis and hypertrophy by repressing the inflammation and its associated activation of TGFβ and myofibroblast conversion.

Colonic L-cell impairment in aged subjects with type 2 diabetes leads to diminished GLP-1 production

AimsGlucagon-like peptide 1 (GLP-1) is produced by the L subtype of enteroendocrine cells (EECs). Patients with type 2 diabetes (T2D) exhibit reduced incretin effect, but the pathophysiology and functional change of the L-cells remain unclear. Deciphering the mechanisms of the biological changes in L-cells under T2D conditions may assist in the research of gut-based strategies for T2D therapy. MethodsWe investigated the fasting serum GLP-1 levels and the distribution of colonic L-cells in young and aged participants with and without T2D. Additionally, we established an aged male T2D Wistar rat model subjected to a long-term high-fat and high-fructose (HFHF) diet. Histological investigations and single-cell RNA sequencing (scRNA-seq) analyses were performed to explore the mechanisms underlying functional changes in the colonic EECs. ResultsWe observed a decline in circulating GLP-1 levels and a reduced number of colonic L-cells in elderly patients with T2D. The mechanisms underlying impaired L-cell formation and disturbed GLP-1 production were revealed using aged T2D rats induced by a long-term HFHF diet. The scRNA-seq results showed that the transcription factors that regulate L-cell commitment, such as Foxa1, were downregulated, and the expression of genes that participate in encoding GLP-1, GLP-1 posttranslational processing, hormone secretion, and nutrient sensing was disturbed. ConclusionsTaken together, the reduced L-cell lineage commitment and disturbed L-cell functions might be the major cause of the reduced GLP-1 production in aged populations with T2D. Our study provides new insights for identifying novel targets in colonic L-cells for improving endogenous GLP-1 production.

Finasteride effectively attenuates the impairments of left ventricular function and cardiac sympathovagal balance in both aging and obese male rats via reducing systemic oxidative stress

Abstract Background Cardiovascular diseases are commonly found in the elderly and obese population manifested by left ventricular (LV) dysfunction and impaired cardiac sympathovagal balance. Finasteride (FIN), a 5-alpha reductase inhibitor (5-ARI), is a universal prescription for patients with benign prostatic hyperplasia (BPH). Since BPH is commonly found in obesity and aging, it is essential to investigate whether FIN could have an impact on the LV function and cardiac sympathovagal balance in either elderly or obese conditions. Purpose We tested the hypothesis that impaired LV function and cardiac sympathovagal balance are observed in aging and obese conditions, and FIN improves these parameters through a reduction of systemic oxidative stress in both aging and obese male rats. Methods Twenty-four male Wistar rats (aged 8 weeks old) were randomly divided into 3 groups (n=8/group) to receive one of the followings: 1) normal diet (ND) feeding, 2) ND feeding with D-galactose injection (150 mg/kg/day, subcutaneous injection, 18 weeks) for creating an aging model, and 3) HFD feeding for 18 weeks for creating an obesity model. At week 13, rats in each group were divided into 2 subgroups (n=4/subgroup) and received either a vehicle (drinking water) or FIN (5 mg/kg/day) via oral gavage. At the end of treatment, echocardiography was performed to assess LV function, and the heart rate variability (HRV) was determined to quantify cardiac sympathovagal balance. The blood was collected, and serum was used to determine serum malondialdehyde (MDA) levels as a marker of systemic oxidative stress. Results At week 13, D-galactose injection successfully induced aging as indicated by increasing cardiac p53 protein expression. HFD also caused obesity in those rats as indicated by increased body weight and visceral fat weight. LV dysfunction (as indicated by reduced %LVEF and %LVFS) and cardiac sympathovalgal imbalance (as indicated by an increased LF/HF ratio) were observed in both models (Figure 1A-C). This functional impairment was associated with an increased MDA levels (Figure 1D). Treatment with FIN successfully reduced cardiac sympathovagal imbalance in both models (Figure 1C); however, an improvement of LV function was found only in aging rats-treated with FIN (Figure 1A, B). Consistent with a reduction of cardiac sympathovagal imbalance, FIN decreased systemic oxidative stress in both models (Figure 1D). Conclusions FIN effectively improved cardiac sympathovagal balance in rats under both aging and obese conditions. However, FIN reduced LV dysfunction only in aging rats. Interestingly, FIN did not affect these cardiac parameters in normal healthy rats. These findings suggest the cardioprotective potential of FIN in both aging and obese populations.

The effect of brain serotonin deficit (TPH2-KO) on the expression and activity of liver cytochrome P450 enzymes in aging male Dark Agouti rats

BackgroundLiver cytochrome P450 (CYP) greatly contributes to the metabolism of endogenous substances and drugs. Recent studies have demonstrated that CYP expression in the liver is controlled by the central nervous system via hormonal pathways. In particular, the expression of hepatic CYPs is negatively regulated by the brain serotoninergic system. The present study aimed to investigate changes in the function of the main liver drug-metabolizing CYP enzymes as a result of serotonin depletion in the brain of aging rats, caused by knockout of brain tryptophan hydroxylase gene (TPH2-KO).MethodsThe hepatic CYP mRNA (qRT-PCR), protein level (Western blotting) and activity (HPLC), and serum hormone levels (ELISA) were measured in Dark Agouti wild-type (WT) male rats (mature 3.5-month-old and senescent 21-month-old) and in TPH2-KO senescent animals.ResultsThe expression/activity of the studied CYPs decreased with age in the liver of wild-type rats. The deprivation of serotonin in the brain of aging males decreased the mRNA level of most of the studied CYPs (CYP1A/2A/2B/3A), and lowered the protein level of CYP2C11 and CYP3A. In contrast, the activities of CYP2C11, CYP3A and CYP2C6 were increased. The expression of cytochrome b5 decreased in aging rats, but increased in TPH2-deficient senescent animals. The serum concentration of growth hormone declined in the aged and further dropped down in TPH2-deficient senescent rats.ConclusionsRat liver cytochrome P450 functions deteriorate with age, which may impair drug metabolism. The TPH2 knockout, which deprives brain serotonin, affects cytochrome P450 expression and activity differently in mature and senescent male rats.

Treatment of stroke in aged male and female rats with Vepoloxamer and tPA reduces neurovascular damage.

Male and female Wistar rats at 18 months of age were subjected to embolic middle cerebral artery occlusion and treated either with monotherapy of tPA or Vepoloxamer, a combination of these two agents, or saline at 4 h after stroke onset. Neurological outcomes were evaluated with a battery of behavioral tests including adhesive removal, foot-fault, and modified neurological severity score tests at 1 and 7 days after stroke onset, followed by histopathological analysis of infarct volume. Residual clot size and vascular patency and integrity were analyzed. The combination treatment with Vepoloxamer and tPA significantly reduced infarct volume and neurological deficits in male and female rats compared to rats treated with saline and the monotherapies of tPA and Vepoloxamer. While Vepoloxamer monotherapy moderately reduced neurological deficits, monotherapies with tPA and Vepoloxamer failed to reduce infarct volume compared to saline treatment. Furthermore, the combination treatment with tPA and Vepoloxamer accelerated thrombolysis, reduced ischemia and tPA-potentiated microvascular disruption, and concomitantly improved cerebrovascular integrity and perfusion in the male ischemic rats. Combination treatment with tPA and Vepoloxamer at 4 h after stroke onset effectively reduces ischemic neurovascular damage by accelerating thrombolysis and reducing ischemia and tPA potentiated side effects in the aged rats. This funding suggests that the combination treatment with tPA and Vepoloxamer represents a promising strategy to potentially apply to the general population of stroke patients.

A-060 Thyroid Laboratory Database Assessment Shows that Total Triiodothyronine Significantly Decreases with Age

Abstract Introduction The effects of aging on human thyroid function are well studied in relationship to thyroid stimulating hormone (TSH) and free tiroxine (FT4); TSH increases, while FT4 decreases with age. Although animal studies show that total triiodotironine (TT3) is lower in aged male rats, these changes are still not clear enough in humans. The National Academy of Clinical Biochemistry (NACB) suggests that TT3 levels would be lower in subjects over 60 years (y.), but the number of elderly assessed was too small for a robust statistical analysis. In search on PubMed, crosschecking the terms elderly/age/aging, with triiodothyronine/T3/total T3, there are a few studies available using current assays with a significant number of patients. Therefore, the demonstration of how the TT3 performs with age is still an opened question. Objective The aim of this study was to observe if TT3 changes significantly with age. Methods We, retrospectively, analyzed blood samples requesting serum TT3 of unique patients, who had TSH measured on the same day; and thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TGAb), anti TSH receptor antibodies (TRAb) or TSH receptor-stimulating immunoglobulin (TSI) at any time since patient admission. Subjects were adults ≥20 y., admitted to a private reference clinical laboratory in Brazil, from January 01, 2014 to December 31, 2022, using anonymized data. Serum TT3 was measured in Cobas Roche, by electrochemiluminescence assay, reference interval 70–210 ng/dL. Exclusion criteria were (and/or): tests performed in hospitals, use of drugs that could interfere on TT3 or TSH, TSH ≤ 0.1 mIU/L or ≥10.0 mIU/L, and any positive antibody at any time. The level of statistical significance was P < 0.05. Results Initially, 959 297 records from the database were surveyed. After applying the exclusion criteria, 141 819 subjects were eligible: mean age = 45 y.; median = 42 y., 62% female (F). Statistically significant differences - P < 0.05 for all comparisons between groups - were found by age and gender in TT3 mean values (in ng/dL). Regarding age: from 20 to 59 y. = 120 ± 26.6; 60 to 79 y. = 109 ± 20.7; and 80 y. and over = 97.2 ± 20.0. By gender: F = 120 ± 28.9; male = 114 ± 20.4. It was also observed that, in elderly, while TT3 decreases, TSH increases (results not shown). Comparing TT3 means by age groups, it is 9% lower in subjects aged 60–79 y. and 19% lower in those aged 80 y. and older, compared to younger (20–59 y.) subjects. Conclusion TT3 results is influenced by several factors, including age, gender and laboratory assay. As far as we know, searching in PubMed, this is the largest collection of data on the relationship between TT3 and age. The data obtained showed a statistically significant decrease in TT3 in elderly, and mainly in very elderly, and higher levels in women than in men. This finding draws call attention to the fact that these parameters should taken into account when evaluating TT3 levels.

PAQR8 and PAQR9 expression is altered in the ventral tegmental area of aged rats infected with varicella zoster virus.

Infection with varicella zoster virus (VZV) results in chicken pox and reactivation of VZV results in herpes zoster (HZ) or what is often referred to as shingles. Patients with HZ experience decreased motivation and increased emotional distress consistent with functions of the ventral tegmental area (VTA) of the brain. In addition, activity within the ventral tegmental area is altered in patients with HZ. HZ primarily affects individuals that are older and the VTA changes with age. To begin to determine if the VTA has a role in HZ symptoms, a screen of 10,000 genes within the VTA in young and old male rats was completed after injecting the whisker pad with VZV. The two genes that had maximal change were membrane progesterone receptors PAQR8 (mPRβ) and PAQR9 (mPRε). Neurons and non-neuronal cells expressed both PAQR8 and PAQR9. PAQR8 and PAQR9 protein expression was significantly reduced after VZV injection of young males. In old rats PAQR9 protein expression was significantly increased after VZV injection and PAQR9 protein expression was reduced in aged male rats versus young rats. Consistent with previous results, pain significantly increased after VZV injection of the whisker pad and aged animals showed significantly more pain than young animals. Our data suggests that PAQR8 and PAQR9 expression is altered by VZV injection and that these changes are affected by age.

Sex differences in microglia function in aged rats underlie vulnerability to cognitive decline

Aging is associated with a significant shift in immune system reactivity (“inflammaging”), as basal inflammation increases but protective responses to infection are compromised. The immune system exhibits considerable sex differences, which may influence the process of inflammaging, including immune cell activation and behavioral consequences of immune signaling (i.e., impaired memory). Here, we test the hypothesis that sex differences in immune aging may mediate sex differences in cognitive decline. Aged male and female rats received peripheral immune stimulation using lipopolysaccharide (LPS), then molecular, cellular, and behavioral outcomes were assessed. We observed that LPS-treated aged male rats showed cognitive impairment and increased neuroinflammatory responses relative to adult males. In contrast, aged female rats did not display these aging-related deficits. Using transcriptomic and flow cytometry analyses, we further observed significant age- and sex- dependent changes in immune cell populations in the brain parenchyma and meninges, indicating a broad shift in the neuroinflammatory environment that may potentiate these behavioral effects. Ovariectomized aged female rats were also resistant to inflammation-induced memory deficits, indicating that ovarian hormones are not required for the attenuated neuroinflammation in aged females. Overall, our results indicate that males have amplified inflammatory priming with age, which contributes to age-associated cognitive decline. Our findings highlight sexual dimorphism in mechanisms of aging, and suggest that sex is a crucial consideration for identifying therapies for aging and neuroinflammation.

Carvacrol improved learning and memory and attenuated the brain tissue oxidative damage in aged male rats

Introduction: Aging is an unavoidable process in the body that is accompanied by impaired tissue homeostasis and various changes. Carvacrol has attracted considerable attention for its wide range of pharmacological activities. Therefore, this study attempted to explore the protective effect of carvacrol in aged rats.Materiel and methods: The aged rats were given carvacrol (15 or 30 mg/kg/day) for 4 weeks. Morris water maze and passive avoidance tests were used to determine the learning and memory abilities of the rats. The hippocampus and cortex samples were taken for biochemical analysis.Results: In comparison to young control rats, aged control rats showed learning and memory deficits. There was improvement in the Morris water navigation test and passive avoidance test performance in the treatment groups versus the aged control group. An increment in malondialdehyde (MDA) and a decrease in total thiol groups in the hippocampus and cortex samples of aged control rats in comparison to the young control group were observed. Carvacrol decreased MDA levels and increased total thiol groups in the hippocampus and cortex samples of aged rats.Conclusion: Carvacrol improved learning and memory in aged rats, probably through its anti-oxidation effects.

Minocycline attenuates hydrocephalus and inhibits iron accumulation, ependymal damage and epiplexus cell activation after intraventricular hemorrhage in aged rats

Intracerebral hemorrhage is primarily a disease of the elderly and it is frequently accompanied by intraventricular hemorrhage (IVH) which can lead to posthemorrhagic hydrocephalus and poor prognosis. Red blood cell iron has been implicated in brain injury after cerebral hemorrhage. The current study examined using T2* magnetic resonance imaging (MRI) to detect periventricular iron deposition after IVH and investigated the effects of minocycline on hydrocephalus in an aged rat IVH model. It had three parts. In part 1, male aged rats received a 200 μl injection of saline or autologous blood into the lateral ventricle and were euthanized at day 14. In parts 2 and 3, aged IVH rats were treated with vehicle or minocycline and euthanized at day 7 or 14. Rats underwent MRI to quantify hydrocephalus and iron deposition followed by brain histology and immunohistochemistry. Periventricular iron overload was found after IVH using T2* MRI and confirmed by histology. IVH also caused ventricular wall damage and increased the number of CD68(+) choroid plexus epiplexus cells. Minocycline administration reduced iron deposition and ventricular volume at days 7 and 14 after IVH, as well as ventricle wall damage and epiplexus cell activation. In summary, IVH-induced hydrocephalus is associated with periventricular iron deposition, ependymal damage and choroid plexus epiplexus cell activation in aged rats. Minocycline attenuated those effects and might be a potential treatment for posthemorrhagic hydrocephalus in the elderly.

Aging impairs recovery from stress-induced depression in male rats possibly by alteration of microRNA-101 expression and Rac1/RhoA pathway in the prefrontal cortex.

Along with altering brain responses to stress, aging may also impair recovery from depression symptoms. In the present study, we investigated depressive-like behaviors in young and aged rats and assayed the levels of microRNA-101 (miR-101), Rac1/RhoA, PSD-95, and GluR1 in the prefrontal cortex (PFC) after stress cessation and after a recovery period. Young (3 months old) and aged (22 months old) male Wistar rats were divided into six groups; Young control (YNG), young rats received chronic stress for four weeks (YNG + CS), young rats received chronic stress for four weeks followed by a 6-week recovery period (YNG + CS + REC), Aged control (AGED), aged rats received chronic stress for four weeks (AGED + CS), and aged rats received chronic stress for four weeks followed by a 6-week recovery period (AGED + CS + REC). Stress-induced depression, evaluated by the sucrose preference test (SPT) and forced swimming test (FST), was yet observed after the recovery period in aged but not in young rats, which were accompanied by unchanged levels of miR-101, Rac1/RhoA, GluR1, and PSD-95 in the PFC of aged rats. These data suggested that impaired synaptic plasticity of glutamatergic synapses via the miR-101/Rac1/RhoA pathway may contribute to the delayed behavioral recovery after stress exposure observed in aging animals.

The rejuvenating influence of young plasma on aged intestine.

This study aims to investigate the effects of plasma exchange on the biomolecular profiles and histology of ileum and colon tissues in young and aged Sprague-Dawley male rats. Fourier transform infrared (FTIR) spectroscopy, linear discriminant analysisand support vector machine (SVM) techniques were employed to analyse the lipid, protein, and nucleic acid indices in young and aged rats. Following the application of young plasma, aged rats demonstrated biomolecular profiles similar to those of their younger counterparts. Histopathological and immunohistochemical assessments showed that young plasma had a protective effect on the intestinal tissues of aged rats, increasing cell density and reducing inflammation. Additionally, the expression levels of key inflammatory mediators tumour necrosis factor-alpha and cyclooxygenase-2 significantly decreased after young plasma administration. These findings underscore the therapeutic potential of young plasma for mitigating age-related changes and inflammation in the intestinal tract. They highlight the critical role of plasma composition in the ageing process and suggest the need for further research to explore how different regions of the intestines respond to plasma exchange. Such understanding could facilitate the development of innovative therapies targeting the gastrointestinal system, enhancing overall health during ageing.

Age-Dependent Influence of Cholecystokinin on the Impulse Activity of Neurons in the Dorsomedial and Venromedial Nuclei of the Hypothalamus in Rats

The aim of the work was to analyze the background and induced by the intravenous administration of the cholecystokinin sulfated octapeptide (CCK), as well as the cholecystokinin antagonist proglumide impulse neuronal electrical activity in the dorsomedial (DMN) and ventromedial (VMN) nuclei of the hypothalamus in young (2–3 months), adults (12 months) and aged (24 months) male rats under urethane anesthesia. The mean frequency of background discharges after the injection of CCK in young rats in the DMN significantly decreased from 1.5 ± 0.4 to 0.2 ± 0.1 impulse/s, in the VMN from 2.0 ± 0.4 to 0.9 ± 0.2 impulse/s. Simultaneous administration of CCK and proglumide did not lead to change of frequencies of neuronal activity in this age group. In adult and aged rats, the mean of the background frequency of discharges of neurons in the DMN and VMN was lower than in young rats and did not change significantly under the influence of CCK and proglumide. In DMN and VMN, the most of the neurons were inhibited by CCK, while in DMN the percentage of neurons inhibited by CCK was higher compared to VMN. The DMN of young animals lacked the CCK-activated neurons that appeared in adult and old animals. Thus, this study confirms the elevation theory of aging, which consists in a decrease in the sensitivity of the hypothalamus to homeostatic signals, in particular, hormones that regulate eating behavior.

Alterations in expression of α1-adrenergic receptors possibly are involved in prevention of age-associated apoptosis in rat hippocampus by treadmill exercise.

Exercise is assumed to attenuate age-related neuronal apoptosis, but the detailed mechanism(s) is not fully understood. α1-adrenergic receptors (ARs) can either trigger or suppress apoptosis, therefore, here we determined the impact of treadmill exercise on the expression of the apoptosis regulatory proteins as well as α1-AR subtypes α1A- and α1B-ARs, in order to elucidate a possible association between apoptosis and the hippocampal expression of α1-ARs in aged male rats. Twenty-one male Wistar rats were divided into 3groups (n=7): young control, aged sedentary, and aged+exercise. Western blot for α1A- and α1B-ARs as well as pro-(Bax and p53) and anti-apoptotic (Bcl2) proteins wasconducted. An 8-week regular moderate-intensity treadmill exercise intervention was carried out in exercise group. In aged rats, α1A-AR expression in the hippocampus was significantly increased, and exercise markedly prevented this event. While α1B-AR expression was no altered with aging, a marked reduction in α1B-AR level was detected in exercise group when compared to aged group. Furthermore, pro-apoptotic protein levels of Bax and p53 were upregulated and anti-apoptotic protein Bcl2 was downregulated in the aging hippocampus, but could be reversed by treadmill exercise. In the present research, exercise-induced reduction in α1A- and α1B-ARs was associated with an obvious downregulation of Bax/Bcl2 ratio in aged rats, suggesting that exercise may inhibit apoptosis through regulating α1-ARs, particularly α1A-AR. Our study suggests that manipulations attenuating α1-AR activity, including nonselective α1-adrenergic antagonists, may protect against hippocampal neurodegeneration in aging brains.

It is all About the Chase: Neurosteroidogenesis in Male Rats is Driven by Control of Mating Pace.

Masculine sexual behaviors are dependent on androstane-derived steroids; however, the modulatory effects of mating, and of mating control, on androstane neurosteroidogenesis remain largely unknown. Herein, we investigated the effects of mating control, prior sexual experience, and age on brain region specific neurosteroidogenic responses in male rats. Effects of acute sexual experience were tested in naïve male rats that either remained sexually- naïve, were exposed to a standard mating chamber, or were either given control of the mating pace in a standard mating chamber (male control) or mated wherein the female stimulus rat controlled the mating pace in a paced-mating chamber (female control). Aged (10-12 months) sexually responsive male rats were similarly euthanized from the homecage or engaged in male controlled or female controlled mating. All rats were euthanized immediately following exposure conditions for radioimmunoassay of steroids in midbrain, hypothalamus, hippocampus and cortex. Consummatory sexual behavior in male vs. female-controlled mating paradigms was altered by age and prior sexual experience. Male-controlled mating increased androstane neurosteroid metabolism, such that complementary increases in the testosterone (T) metabolite 5α-androstane-3α-17β- diol (3α-diol) in the midbrain and hypothalamus of male rats corresponded to decreases in the prohormone, T. 3α-diol were increased in the hippocampus in response to the context alone, and to a lesser degree in response to mating. Mating diminished neurosteroidogenesis in the cortex. Neurosteroidogenesis was overall reduced in aged male rats compared to naïve controls, however, these effects were more prominent in sexually non-responsive aged male rats. Extending previous findings, these results indicate differential production of androstane neurosteroids in a mating exposure, age and brain region dependent manner.

Prolonged stress-induced depression-like behaviors in aged rats are mediated by endoplasmic reticulum stress and apoptosis in the hippocampus

Structural and functional recovery from stress-induced depression is impaired in the context of aging brain. Since investigating the molecular substrates that facilitate behavioral recovery may have important implications for understanding brain plasticity and resilience of individuals, we studied depressive-like behaviors in young and aged rats 6 weeks after chronic stress exposure as a recovery period and examined the levels of TNF-α and IL-6 inflammatory cytokines, NADH oxidase activity, NADPH oxidase, endoplasmic reticulum (ER) stress markers, and apoptosis in the hippocampus. Young (3 months old) and aged (22 months old) male Wistar rats were divided into four groups; young control (Young), depression model of young rats that received chronic stress procedure followed by a 6-week recovery period (Young+S), aged control (Aged), and depression model of aged rats that received chronic stress procedure followed by a 6-week recovery period (Aged+S). After the recovery period, aged but not young rats showed depression-like behaviors, evaluated by the sucrose preference test (SPT) and forced swimming test (FST), coincided with the altered levels of TNF-α, IL-6, NADH oxidase activity, NADPH oxidase, GRP78, CHOP, and cleaved caspase-12 in the hippocampus of these animals. These data suggested that oxidative and ER stress-induced apoptosis in the aging hippocampus may affect the recovery-related outcomes after the stress paradigm.

Sprague-Dawley rats differ in responses to medial perforant path paired pulse and tetanic activation as a function of sex and age.

Network plasticity in the medial perforant path (MPP) of adult (5-9 mo) and aged (18-20 mo) urethane-anesthetized male and female Sprague-Dawley rats was characterized. Paired pulses probed recurrent networks before and after a moderate tetanic protocol. Adult females exhibited greater EPSP-spike coupling suggesting greater intrinsic excitability than adult males. Aged rats did not differ in EPSP-spike coupling but aged females had larger spikes at high currents than males. Paired pulses suggested lower GABA-B inhibition in females. Absolute population spike measures were larger post-tetani in female rats than male rats. Relative population spike increases were greatest in adult males relative to females and to aged males. EPSP slope potentiation was detected with normalization in some post-tetanic intervals for all groups except aged males. Tetani shortened spike latency across groups. Tetani-associated NMDA-mediated burst depolarizations were larger for the first two trains in each tetanus in adult males than other groups. EPSP slopes over 30 min post-tetani predicted spike size in female rats, but not in males. Replicating newer evidence MPP plasticity in adult males was mediated by increased intrinsic excitability. Female MPP plasticity was related to synaptic drive increases, not excitability increases. Aged male rats were deficient in MPP plasticity.SIGNIFICANCE STATEMENTThe medial perforant path (MPP)-dentate gyrus (DG) granule cell synapse was the site of discovery of long-term potentiation in the mammalian nervous system but considering the current interest in sex and aging, surprisingly few studies have directly examined these variables in relation to tetanus-induced long-term and short-term (paired pulse) plasticity. Using an interleaved current-paired pulse interval protocol and moderate tetanic protocol young (5-9mo) and old (18-20mo) male and female urethane anesthetized rats were found to differ in levels of granule cell intrinsic excitability, E-S coupling, GABA-B inhibition, and tetanic NMDA current contributions to post-tetanic population spike potentiation. This study provides a platform or future examination of sex- and age-related changes in MPP-DG function.