Cerebellum Of Old Rats Research Articles

Dietary supplementation with acetyl-l-carnitine counteracts age-related alterations of mitochondrial biogenesis, dynamics and antioxidant defenses in brain of old rats

We previously reported the ability of dietary supplementation with acetyl-l-carnitine (ALCAR) to prevent age-related decreases of mitochondrial biogenesis in skeletal muscle and liver of old rats. Here, we investigate the effects of ALCAR supplementation in cerebral hemispheres and cerebellum of old rats by analyzing several parameters linked to mitochondrial biogenesis, mitochondrial dynamics and antioxidant defenses.We measured the level of the coactivators PGC-1α and PGC-1β and of the factors regulating mitochondrial biogenesis, finding an age-related decrease of PGC-1β, whereas PGC-1α level was unvaried. Twenty eight-month old rats supplemented with ALCAR for one and two months showed increased levels of both factors. Accordingly, the expression of the two transcription factors NRF-1 and TFAM followed the same trend of PGC-1β. The level of mtDNA, ND1 and the activity of citrate synthase, were decreased with aging and increased following ALCAR treatment. Furthermore, ALCAR counteracted the age-related increase of deleted mtDNA. We also analyzed the content of proteins involved in mitochondrial dynamics (Drp1, Fis1, OPA1 and MNF2) and found an age-dependent increase of MFN2 and of the long form of OPA1. ALCAR treatment restored the content of the two proteins to the level of the young rats. No changes with aging and ALCAR were observed for Drp1 and Fis1. ALCAR reduced total cellular levels of oxidized PRXs and counteracted the age-related decrease of PRX3 and SOD2.Overall, our findings indicate a systemic positive effect of ALCAR dietary treatment and a tissue specific regulation of mitochondrial homeostasis in brain of old rats. Moreover, it appears that ALCAR acts as a nutrient since in most cases its effects were almost completely abolished one month after treatment suspension. Dietary supplementation of old rats with this compound seems a valuable approach to prevent age-related mitochondrial dysfunction and might ultimately represent a strategy to delay age-associated negative consequences in mitochondrial homeostasis.

Effect of desynchronosis on oxidative stress biomarkers and the state of glial intermediate filaments in the brains of rats subject to aging

Desynchronosis may be the cause of many diseases. Oxidative stress plays an important role in the pathogenesis of various diseases. The present study investigates the effect of constant light on biomarkers of oxidative stress and content of glial intermediate filaments protein in the brains of old rats. We found that desynchronosis led to development of oxidative stress in the hippocampus, cerebral cortex and cerebellum of old rats. Prolonged continuous lighting led to an increase in the content of TBA-reactive products in all studied regions of the brains of old rats. This indicates an activation of lipid peroxidation and oxidative stress. Significant changes in the content of TBA-reactive products were found in the departments responsible for the functions of the higher nervous activity, particularly in the hippocampus and cerebral cortex. The level of restored glutathione in all three regions of the brain decreased in the group of rats kept under constant illumination in comparison with the control group. The results of the indicators of locomotor and orienting-investigative activity of the animals in the "open field" test revealled changes in the indices for desynchronosis. This showed a reduction in locomotor activity, inhibition of exploratory activity and development of emotional stress. In the brains of old rats kept under constant illumination a significant increase in the content of glial fibrillary protein (GFAP) was shown. There was a significant increase in the intensity of the polypeptide zone 49 kDa in the filamentous and soluble fraction of the cerebellum and hippocampus. This fact indicates that desynchronosis activates fibrillogenesis in glial cells. At the same time, there is degradation of polypeptides GFAP with Mr in the field of 46 kDa. Melatonin is a universal adaptogen that regulates the function of many body systems. The amount of melatonin which is synthesized depends on the illumination mode. Violation of the global mode reduces the amount of melatonin and leads to the development of desynchronosis, which may be the cause of many diseases. The administration of melatonin helped reverse the changes – raising the level of restored glutathione and preventing the growth of the content of peroxidation products and indices of "open field" test, and also decreasing the degradation of GFAP and the amount of protein. The results indicate the protective effect of melatonin, showing reductions in glial reactivity and in the level of oxidative stress in the brains of old rats subject to desynchronosis.

Altered expression of γ2L and γ2S GABAA receptor subunits in the aging rat brain

Aging-related alterations in both protein and mRNA expression of gamma 2S and gamma 2L subunits of the GABAA receptors have been observed in several brain areas of Sprague-Dawley and Fischer 344 rats. Subunit-specific antibodies to gamma 2S and gamma 2L as well as a riboprobe to the large intracellular loop of gamma 2, which recognizes both gamma 2S and gamma 2L mRNAs, in conjunction with computerized image analysis were used for quantitative immunocytochemistry and in situ hybridization. In addition, specific oligonucleotide probes to gamma 2S or gamma 2L mRNA were used for quantitative dot blot hybridization. A large increase in the number of heavily immunostained neurons with the anti-gamma 2L antibody was detected in the cerebral cortex (115%) of old rats. However, only a small (but significant) aging-related increase in the density of gamma 2L immunostaining (7%) was observed throughout the cerebral cortex whereas no significant aging-related change in gamma 2L mRNA was detected in this brain region. Contrary to gamma 2L, the gamma 2S immunostaining did not show aging-related increased number of heavily immunostained neurons in cerebral cortex. Moreover, the density of gamma 2S immunostaining and the expression of gamma 2S mRNA were significantly decreased in the cerebral cortex (9-24%). Important aging-related changes were also found in the cerebellum of old rats where the expression of both gamma 2S and gamma 2L peptides was significantly decreased (24% and 23% respectively). This decrease in gamma 2 protein expression was accompanied by decreased expression of gamma 2S (16-38%) and gamma 2L (24%) mRNAs. Nevertheless, the most important decrease of gamma 2S (48%) and gamma 2L protein (20%) was revealed in the molecular layer of the cerebellum. In addition, the expression of gamma 2S protein was increased (14%) whereas the expression of gamma 2L was decreased (13%) in the granule cell layer. Therefore, the relative expression of gamma 2S protein in both layers was reversed in old animals. The observed aging-related changes in the expression of GABAA receptor subunits might lead to altered GABAA receptor/benzodiazepine receptor subunit composition.

Aging related alterations in GABA A receptor subunit mRNA levels in Fischer rats

The influence of aging on the binding of ligands to picrotoxin binding sites as well as steady state levels of mRNA for various α subunits of γ-aminobutyric acid (GABA) receptor complex was investigated in male Fischer F-344 rats. In aged rats, the binding of [ 35 S]t- butyl-bicyclophosphorothionate (TBPS) was significantly reduced. This decrease in TBPS binding derived from a reduced density of binding sites, rather than from affinity changes, in both cerebral cortex and cerebellum. In aged rats, α 1 mRNA level decreased approximately 70% between age 6 months and 24 months in the cerebral cortex ( P < 0.005). In contrast, α 1 mRNA remained unchanged in the cerebellum of old rats. The association of a decrease in picrotoxin binding sites in the cerebral cortex with a decline in α 1 mRNA level in the cerebral cortex and in α 2 mRNA level in the cerebellum is indicated. α 6 mRNa level increased with age in the cerebellum. These findings indicate a selective age related modulation in the stoichiometry of GABA A receptor in aging.

Enzyme histochemistry of glutamate dehydrogenase in ageing rat cerebellar cortex

The influence of ageing on glutamate dehydrogenase activity was studied in the cerebellar cortex of 3-month-old (young), 12-month-old (adult) and 26-month-old (aged) male Sprague—Dawley rats by using an enzyme histochemical technique. In young rats the enzyme reactivity was observed in the neuropil of the molecular layer as well as in the perikarya of basket cells and of stellate cells; within the cytoplasm of Purkinje neurons and in synaptic glomeruli of the granular layer. Glutamate dehydrogenase activity was significantly increased in the cerebellar cortex of adult rats and decreased in old animals. The synaptic glomeruli of the granular layer were the structures of the cerebellar cortex more remarkably affected by age-related changes. The possibility that decreased glutamate catabolism occurring in the ageing cerebellar cortex may result in an excess of the amino acid and may contribute to the nerve cell loss occurring in the cerebellum of old rats is discussed.