Neurons In Old Rats Research Articles

INFLUENCE OF DIFFERENT LIGHTING REGIMEN ON THE MORPHOMETRIC CHARACTERISTICS OF NEURONS IN THE PARAVENTRICULAR NUCLEI OF THE RAT HYPOTHALAMUS

Paraventricular nuclei (PVN) of the hypothalamus are the autonomic center forcoordination of functions and consists of a number of neuronal populations - sub-nuclei,which differ in structural and functional features and the nature of nerve connectionswith various parts of the nervous and neuroendocrine systems. When studying stressreactions and actions of the stress-limiting factors, it is important to study subpopulationsof PVN neurons of the hypothalamus, synthesizing stress-releasing hormones, whichinitiate stress reactions of the body. One of the main factors that show a pronouncedeffect in the regulation of ACTH secretion is corticotropin-releasing factor (CRF). TheCRF-immunoreactive tracer was found mainly in the medial small-cell subnucleus of theparaventricular nuclei of the rat hypothalamus. Despite deep and comprehensive studiesof the hypothalamus, until now there are no unifed ideas about its individual reactivityand the degree of involvement of these structures into the stress reaction caused by theprolonged change in the lighting regime.Purpose - to fnd out the effect of different illumination regimes on the morphometriccharacteristics of the medial small-cell subnuclei of the paraventricular nuclei of thehypothalamus of mature and old rats.Material and methods. The experiments were conducted on 72 nonlinear white malerats, divided into 6 series of studies, in each of which the biomaterial sampling wascarried out at 14.00 and 02.00 h using morphometric and statistical research methods.Results. Morphometric assessment of the medial small-cell sub-nuclei of theparaventricular nuclei (msPVN) of the hypothalamus of rats revealed the diurnaldynamics of indices. It has been established that in both old and mature rats, theiraverage volume (p <0.05) signifcantly decreases at 2.00 compared to 14.00 undernormal lighting. The nuclear-cytoplasmatic ratio at 02.00 increases in comparison with14.00 respectively.When the animals were kept under constant illumination, more pronounced changesin the structures under study were established. In particular, the volume of neurons inthe msPVN of the hypothalamus decreases both mature and old rats compared withrats under standard illumination and even more in comparison with rats under lightdeprivation. In accordance with this, the NCR also changes. The average number ofneurons on the standard plane of the histological section also decreases in comparisonwith other illumination regimes. It is also necessary to point out that under conditionsof light stimulation in mature rats in msPVN, the average volume of neurons (p <0.05)noticeably decreases at 02:00 in comparison with 14:00, when the volume of theirnuclei does not change on average during the indicated study periods. This is reflected,respectively, in the NCR change, which increases at 02.00 in comparison with 14.00.As to the old rats, the average neuron volume does not decrease at 2.00 in comparisonwith 14.00 in msPVN neurons at light stimulation, as well as the volume of their neucleichanges, on average, is barely noticeable ,and according to it, NCR at 02.00 remainsstable in comparison with 14.00, and the average quantity of neurocytes in msPVN doesnot change on a standard plane of the histological section during various periods ofthe twenty four hours. At the same time, with various modifcations of the light regime,cytometric parameters of neurons under study in old rats, on average, are signifcantlylower (p <0.001) than those in mature rats.Conclusions. 1. The duration of the photoperiod signifcantly affects the 24 hoursactivity of msPVN in the hypothalamus of mature and old rats. In particular, in bothinvestigated groups of rats, the average volume of neurons (p <0.05) reliably decreasesat 2.00 under normal illumination in comparison with 14.00, and, accordingly, the NCR at 02.00 increases compared to 14.00. All cytometric parameters of their neurons in oldrats are, on average, signifcantly lower (p <0.001) than in mature rats.2. Constant illumination causes more pronounced changes in the morphometricparameters of the msPVN of the hypothalamus than light deprivation. Thus, in maturerats in the msPVN, the average volume of neurons (p <0.05) decreases noticeably at02:00 in comparison with 14:00, which is reflected, respectively, in the change in NCR,which increases at 02:00 compared to 14:00. For old rats, under light stimulation, allthe studied cytometric parameters of their neurons, on average, are signifcantly lower(p <0.001) than those in mature rats.

Glibenclamide Ameliorates the Expression of Neurotrophic Factors in Sevoflurane Anaesthesia-induced Oxidative Stress and Cognitive Impairment in Hippocampal Neurons of Old Rats.

IntroductionSeveral antidiabetic medications have been proposed as prospective treatments for cognitive impairments in type 2 diabetes patients, glibenclamide (GBC) among them. Our research aimed to evaluate the impact of GBC on hippocampal learning memory and inflammation due to enhanced neurotrophic signals induced by inhalation of sevoflurane.Material and MethodsRats (Sprague Dawley, both sexes) were assigned to four groups: a control (vehicle, p.o.), GBC (10 mg/kg b.w.; p.o.), low-dose sevoflurane and low-dose sevoflurane + GBC (10 mg/kg b.w.; p.o.) for 23 days. Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining was performed to analyse the count of apoptotic cells and ELISA was conducted to assess the protein signals. A Western blot, a Y-maze test, and a Morris maze test were performed, and the results analysed. Blood and tissues were collected, and isolation of RNA was performed with qRT-PCR.ResultsThe Morris maze test results revealed an improvement in the length of the escape latency on days 1 (P < 0.05), 2 (P < 0.01), 3, and 4 in the low-dose Sevo group. Time spent in the quadrant and crossing axis and the percentage of spontaneous alterations showed a substantial decrease in the low-dose Sevo group which received GBC at 10 mg/kg b.w. Significant increases were shown in IL-6 and TNF-α levels in the low-dose Sevo group, whereas a decrease was evident in the GBC group.ConclusionOur results indicate that glibenclamide may be a novel drug to prevent sevoflurane inhalation-induced impaired learning and reduce brain-derived neurotrophic factor release, which may be a vital target for the development of potential therapies for cognitive deficits and neurodegeneration.

The treatment of Goji berry (Lycium barbarum) improves the neuroplasticity of the prefrontal cortex and hippocampus in aged rats

The main characteristic of brain aging is an exacerbated inflammatory and oxidative response that affects dendritic morphology and the function of the neurons of the prefrontal cortex (PFC) and the hippocampus. This consequently causes memory loss. Recently, the use of the Goji berry (Lycium barbarum) as an antioxidant extract has provided neuroprotection and neuroplasticity, however, its therapeutic potential has not been demonstrated in aging conditions. The objective of this study was to evaluate the effect of Goji administration on memory recognition, as well as the changes in the dendritic morphology of the PFC and Hippocampus pyramidal neurons in old rats. Goji (3 g/kg) was administrated for 60 days in 18-month-old rats. After the treatment, recognition memory was evaluated using the new object recognition task (NORt). The changes in the neuron morphology of the PFC and hippocampus pyramidal neurons in old rats were evaluated by Golgi-cox stain and immunoreactivity for synaptophysin, glial fibrillary acidic protein (GFAP), caspase-3, 3-nitrotyrosine (3-NT) and nuclear factor erythroid 2-related factor 2 (Nrf2). The rats treated with Goji showed a significant increase in dendritic morphology in the PFC and hippocampus neurons, a greater immunoreactivity to synaptophysin and a decrease in reactive astrogliosis and also in caspase-3, in 3-NT and in Nrf2 in these brain regions was also observed. Goji administration promotes the plasticity processes in the PFC and in the hippocampus of old rats, critical structures in the brain aging process.

Sevoflurane anesthesia-mediated oxidative stress and cognitive impairment in hippocampal neurons of old rats can be ameliorated by expression of brain derived neurotrophic factor

Postoperative cognitive dysfunction in elderly patients has been related to neurodegenerative disorders and mortality. Sevoflurane anesthesia has been implicated in both postoperative cognitive dysfunction and neurotoxicity. Given the advantages of using inhaled anesthetics like sevoflurane, it is important to understand how their usage results in neurotoxicity and subsequently devise ways to circumvent or attenuate the anesthetic-mediated induction in neurotoxicity. We have used an aged rat model to investigate the molecular mechanisms by which sevoflurane inhalation results in neurotoxicity and whether modulation of these molecular mechanisms can inhibit or attenuate neurotoxicity and cognitive learning and memory impairment in these animals. Low- or high-dose of sevoflurane resulted in reactive oxygen species generation, increased NADPH oxidase protein expression, apoptosis and autophagy. Sevoflurane inhalation resulted in significant inhibition of brain derived neurotrophic factor (BDNF) and cognitive impairment. And the activation of PI3K/Akt/mTOR signaling pathways are attenuated in sevoflurane-mediated anesthesia. Adeno-associated virus (AAV)-mediated expression of Bdnf, but not controls EGFP, attenuated sevoflurane-induced oxidative stress and cognitive impairment in the rats. Our results highlight that AAV-mediated gene therapy might offer a potential therapeutic opportunity to treat post-operative cognitive impairment resulting from inhaled anesthetics.

Sevoflurane Anesthesia-Mediated Oxidative Stress and Cognitive Impairment in Hippocampal Neurons of Old Rats Can Be Ameliorated by Expression of Brain Derived Neurotrophic Factor

Sevoflurane Anesthesia-Mediated Oxidative Stress and Cognitive Impairment in Hippocampal Neurons of Old Rats Can Be Ameliorated by Expression of Brain Derived Neurotrophic Factor

Changes in GABAergic markers accompany degradation of neuronal function in the primary visual cortex of senescent rats

Numerous studies have reported age-dependent degradation of neuronal function in the visual cortex and have attributed this functional decline to weakened intracortical inhibition, especially GABAergic inhibition. However, whether this type of functional decline is linked to compromised GABAergic inhibition has not been fully confirmed. Here, we compared the neuronal response properties and markers of GABAergic inhibition in the primary visual cortex (V1) of young adult and senescent rats. Compared with those of young adult rats, old rats’ V1 neurons exhibited significantly increased visually evoked responses and spontaneous activity, a decreased signal-to-noise ratio and reduced response selectivity for the stimulus orientation and motion direction. Additionally, the ratio of GABA-positive neurons to total cortical neurons in old rats was significantly decreased compared with that in young rats. Expression of the key GABA-synthesizing enzyme GAD67 was significantly lower in old rats than in young rats, although GAD65 expression showed a marginal difference between the two age groups. Further, expression of an important GABAA receptor subunit, GABAAR α1, was significantly attenuated in old rats relative to young ones. These results demonstrate that ageing may result in decreased GABAergic inhibition in the visual cortex and that this decrease in GABAergic inhibition accompanies neuronal function degradation.

Aging-related alterations in the expression and distribution of GluR2 and PICK1 in the rat hippocampus

Deficit in synaptic plasticity in the hippocampus frequently occurs during normal aging. Although the protein level and calcium permeability of AMPARs alter with aging, the alteration of AMPARs and their regulatory proteins during aging are far from understanding. Dynamics of GluR2 subunit are dependent on the function of protein interacting with Cα kinase 1 (PICK1), PKCα and calcineurin (CaN). Here, we firstly show that the expression of PICK1 and CaN B decreased significantly in the hippocampus of old rats compared to that of young and adult rats. The decrease was accompanied by a reduction of GluR2 and PKCα and an increase in CaN A. Next, we found that in young and adult rats, the distribution of PICK1 and GluR2 diffused in the cytoplasm of hippocampal neurons, but closely around perinuclear in the hippocampal neurons of old rats. These results suggest that the expression of GluR2, PICK1, PKCα and CaN B significant decreased in the hippocampus and these alterations may lead to altered distribution of GluR2 and PICK1 during aging.

Topographic morphology and age-related analysis of the neuronal number of the rat intracardiac nerve plexus

The study was designed to determine the three-dimensional organization of the rat intrinsic cardiac neural plexus (ICNP) and to ascertain whether the rat heart undergoes a decrease in neuronal number with aging as has been reported for other mammalian species, including human. Juvenile (3-4 weeks of age, n = 14) and adult (more than 2 months of age, n = 23) animals were examined using enzyme histochemistry for acetylcholinesterase in order to visualize the ICNP in total hearts. The number of intrinsic cardiac neurons was estimated by counting nerve cells in serial sections of the atrial pieces stained with cresyl fast violet. The total number of intrinsic cardiac neurons in old rats was 6576 +/- 317. The juvenile animals contained significantly fewer such neurons, only 5009 +/- 332. Approximately 70% of all intracardiac neurons were amassed within the heart hilum, while 30% of the neurons were distributed epicardially. Within the interatrial septum, only 11 +/- 11 neurons were identified in the juvenile and 6 +/- 4 neurons in old rats. Extrinsic nerves entered the rat heart in both the arterial and venous parts of the cardiac hilum. The nerves from the arterial part of the cardiac hilum extended directly to the ventricles but the nerves from the venous part of the hilum formed a particular nerve plexus of the cardiac hilum on the heart base. Within the rat epicardium, intrinsic nerves clustered into six routes by which they selectively projected to different atrial and/or ventricular regions. In conclusion, this study provides a detailed description of the three-dimensional organization of the rat ICNP and contradicts the decrease in neuronal number with aging in the rat heart.

Sleep-related increase in activity of mesopontine neurons in old rats.

Relationships between age-related changes in sleep patterns and neuronal activity have received scant attention. In the present study, reticularis pontis oralis (RPO) and ventral tegmental nucleus of Gudden (VTN) neurons were recorded in unanesthetized restrained young (3 months) and old (23 months) Sprague-Dawley rats during wakefulness (W), slow wave sleep (SWS) and rapid eye movement (REM) sleep. All RPO neurons displayed a tonic activity. Firing rates were similar during W in young and old rats. In contrast, firing rates were higher during SWS in old rats (P < 0.001). In both young and old rats, firing rates increased significantly during REM sleep as compared to W and SWS but this increase was markedly greater in old rats. Neurons recorded from VTN displayed bursting activity at theta frequencies during W and REM sleep. The frequency of VTN bursting neurons was higher during REM sleep as compared to W in both groups of age. This difference was significantly more pronounced in old as compared to young rats (P < 0.001). Sleep-related hyperactivity of pontine neurons is discussed in terms of a possible deficit in inhibitory processes in old rats.

Effects of Senescence and Citral on Neuronal Vacuolar Degeneration in Rat Pelvic Ganglia

A significant part of the morbidity in elderly men involves pelvic organs and their autonomic neural regulation. Environmental stimuli also impair the structure and function of pelvic organs. One of these factors is citral, a widely-used cosmetic fragrance constituent, which causes severe prostatic hyperplasia in rats. In this study, we assessed the effect of topical administration of citral (30 days) on the morphology of pelvic ganglia (PG) in young adult and old Wistar rats. Neuronal vacuolar degeneration with preserved nuclei of PG neurons was observed in untreated senescent, but not young rats. Citral significantly increased the rate of vacuolated neurons in old rats (from 3 to 14%), but only slightly in young ones (from 0 to 0.5–0.3%). Similar lesions were not found in inferior cervical or celiac ganglia, in either group. This shows that environmental stimuli enhance age-related processes of vacuolar neuronal degeneration in PG, and may contribute to the dysfunction of pelvic organs in the elderly.

Lumbar motor neuron size and number is affected by age in male F344 rats

Motor neurons in the spinal cord of old rats appear similar in size but less numerous compared with those in mature rats; they also contain a large amount of lipofuscin, the lipid peroxidation by-product whose function is largely unknown. The object of this study was to morphometrically characterize motor neurons found in the L4/L5 lumbar spinal cord of mature (6-month) and old (22-month) rats. Paraformaldehyde-fixed, lumbar spinal cords from six rats at each age were embedded in paraffin, sectioned at 6 μm and stained with 0.1% toluidine blue. The nucleolar diameter and area from a minimum of 34 motor neurons per spinal cord were measured. Motor neuron number was calculated using Abercrombie's ( Abercrombie, 1946) formula after correcting for tissue shrinkage. Motor neuron number was decreased with age while the neuronal area increased with age. Nucleolar diameter also increased in old rats. Frequency distributions of motor neuron area revealed unimodal distributions of motor neurons rats of both ages. We suggest that larger nucleolar diameter reflects more metabolically active neurons in old rats while larger neuron area is a reflection of the presence of lipofuscin in old motor neurons.

Calbindin D-28k immunoreactivity in the rat cerebellar cortex: age-related changes

The present study was designed to analyze age-dependent changes in the expression of calbindin D-28k immunoreactivity in the cerebellar cortex of male Wistar rats aged 3 months (young), 12 months (adult) and 24 months (old). Calbindin D-28k immunoreactivity was localized primarily in the cytoplasm of Purkinje neurons and in the basal portion of their dendritic processes entering in the molecular layer. The expression of calbindin D-28k immunoreactivity was highest in Purkinje neurons of adult rats and lowest in Purkinje neurons of old rats. Moreover, the number of Purkinje neurons displaying calbindin D-28k immunoreactivity was decreased in aged rats. These results demonstrate the occurrence of age-related-changes in the expression of immunoreactivity of the Ca 2+ binding protein calbindin D-28k in the rat cerebellar cortex. The possibility that impairment in the expression of Ca 2+ binding proteins may be involved in changes of intracellular Ca 2+ homeostasis reported in aging and in some neuro-degenerative disorders is discussed.

Influence of treatment with l-deprenyl on the structure of the cerebellar cortex of aged rats

Treatment with l-deprenyl increases mean and maximum life span in the rat and reverses memory and learning deficits associated with old age. Since only sparse information is available concerning the influence of l-deprenyl administration on the aging brain microanatomy, we have investigated the effect of long-term treatment with l-deprenyl on the structure of the cerebellar cortex in the aged rat. The cerebellar cortex was used since it represents a useful model for assessing age-related changes in nervous system anatomy and function. Male Sprague-Dawley rats were treated from the 19th to the 24th month of age with a daily oral dose of 1.25 mg/kg or 5 mg/kg l-deprenyl. Age-matched rats were left untreated and used as a control group. Eleven-month-old untreated rats were used as an adult reference group. The density of Purkinje and granule neuron profiles as well as the intensity of Nissl's staining within the cytoplasm of Purkinje neurons were reduced in 24-month in comparison with 11-month rats. Moreover, an increased accumulation of lipofuscin was noticeable in the cytoplasm of Purkinje neurons of old rats as well as an increase in MAO-B activity in the molecular layer of the cerebellar cortex. The two doses of l-deprenyl increased the density of both Purkinje and granule neuron profiles and the intensity of Nissl's staining in the cytoplasm of Purkinje neurons and reduced lipofuscin deposition within Purkinje neurons. The lower dose of l-deprenyl caused only a slight decrease in MAO-B activity, whereas the 5-mg/kg/day dose remarkably reduced it. These results suggest that long-term treatment with l-deprenyl counters the expression of some age-related microanatomical changes in the rat cerebellar cortex. The possible independence of the effects of the compound on age-related microanatomical changes of the cerebellar cortex and on MAO-B inhibitory activity is discussed.

Comparison of brain dopamine depletion induced by low-dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in young and aged rats

Effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on dopamine levels in the striatum (ST), substantia nigra (SN), olfactory tubercle (OT), ventral tegmental area (VTA) and nucleus accumbens (NA) were studied in young (1 month) and old (21 months) male Long-Evans rats. Following repeated treatment with MPTP at low dose (3 mg/kg i.p. daily for 8 days) both young and old rats showed a marked depletion of dopamine (DA) concentrations in the ST compared to those of age-matched saline-treated controls. However, a significant reduction in DA levels was observed in the OT and NA of old but not young rats treated with MPTP. In contrast, no changes in 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels in these three regions were seen in either young or old MPTP-treated rats. However, the ratio of DOPAC/DA and HVA/DA in the ST and NA were significantly higher in old MPTP-treated rats than those in old controls. The concentrations of DA, DOPAC and HVA remained unchanged in the SN and VTA of both young and old rats after MPTP treatment. These results indicate that multiple treatment of low-dose MPTP selectively causes more widespread damage to dopaminergic neurons in old rats than in young ones, and further support the view that effects of MPTP on the dopaminergic system in rats may depend on age.

Reduction of the amount of neurotensin retrogradely transported in dopaminergic neurons of senescent rats

It is now clearly established that fast anterograde axonal transport can be altered during ageing, both in the central and the peripheral nervous systems, but no information is yet available concerning the modifications of fast retrograde axonal transport during senescence. In the present paper, we report the changes occurring in the retrograde axonal transport of neurotensin in dopaminergic neurons of old rats. When iodinated neurotensin was injected into the striatum, a diminution of approximately 50% in the amount of the labelling measured in the ipsilateral substantia nigra was observed in senescent rats by comparison with young adult rats. Nevertheless, the rate of neurotensin transport was not modified. Our results clearly indicate that less neurotensin is transported from the nerve terminals towards the cell bodies in senescent rats which may have possible consequences for dopaminergic neurons.

Recovery of function after mesotelencephalic dopaminergic injury in senescence

After intracerebral 6-hydroxydopamine injections that extensively damage the ascending mesotelencephalic dopaminergic projection, young adult rats develop severe sensorimotor deficits, including an inability to orient toward somatosensory stimuli. Many rats with such damage recover their localization of touch, and this recovery depends on the survival of a small proportion of the neostriatal dopaminergic terminals. Behavioral recovery appears to be mediated by an increased dopamine synthesis and release within surviving terminals and an increased responsiveness to dopamine of neostriatal neurons. The ability of aged rodents to increase activity at neostriatal dopaminergic synapses following partial injury to these neurons is remarkably intact, despite the reduced basal level of transmission at these synapses in senescence. First, 27–28-month-old rats recovered somatosensory localization after injury as readily as did 4–5-month-old animals that had equivalent neostriatal dopamine depletions. Second, old and young rats developed a similar degree of behavioral supersensitivity to apomorphine (0.25 mg/kg, i.p.) after unilateral 6-hydroxydopamine injections, as measured by contralateral turning. Third, injury to these neurons produced an equivalent increase in [ 3H]spiroperidol binding in the neostriatum of old and young rats at 5–7 weeks. Old rats suffered more extensive neostriatal dopamine depletions after intracerebral 6-hydroxydopamine injections than did young adult animals, particularly when small quantities (2 μg) of the neurotoxin were injected. This enhanced susceptibility to 6-hydroxydopamine of dopaminergic neurons in old rats could not be attributed to age differences in the placement of the injection cannula or the extent of the non-specific damage at the injection site. The implications of this enhanced susceptibility to the neurotoxin are discussed.