Variations in trace metal levels in rat hippocampus during ontogenetic development

The variations in trace metal (zinc, iron, copper and manganese) levels in rat hippocampus were followed by atomic absorption spectrophotometry from the 17th embryonic day to the 100th postnatal day. In agreement with histochemical observations, it was found that the greatest relative increase in the hippocampal zinc level occurs during the 11th-20th postnatal days, simultaneously with the morphological maturation of the mossy fibre terminals. The iron level falls dramatically from the 17th embryonic day to the 3rd postnatal day. Beginning from the 11th postnatal day, the iron level, similarly to the copper level, continuously increases with age. The manganese level rises up to the 20th postnatal day, and subsequently progressively decreases. It is suggested that all of these elements are indispensable for the normal development and functioning of the hippocampus and the mossy fibre terminals.     

Gerbil angiotensin II AT1 receptors are highly expressed in the hippocampus and cerebral cortex during postnatal development

Increasing evidence suggests that Angiotensin II, classically known from its many effects regulating salt and water homeostasis, is also involved in brain development and cognitive functions through activation of AT1 Angiotensin II receptors. The recently cloned gerbil AT1 receptor is expressed in brain areas controlling hydro-mineral homeostasis, and particularly highly expressed in limbic areas such as the hippocampal formation. We quantified the gerbil AT1 receptor messenger RNA expression and receptor binding by quantitative in situ hybridization and receptor autoradiography, respectively, in the hippocampal formation and cerebral cortex of gerbils during postnatal development. The receptor messenger RNA and binding were present from birth and showed a gradual and sustained increase through postnatal maturation in the CA1 and CA2 regions of the hippocampus and in the dentate gyrus. Conversely, in the CA3 region, no binding was detected while receptor messenger RNA peaked at 15 days after birth and disappeared in the adult. The highest receptor messenger RNA expression and binding were found in the septomedial portions of the CA1 region and at septal levels of the CA2 region. We detected the highest receptor messenger RNA expression at postnatal day one in the frontolateral pole of the cerebral hemispheres. In these areas, and in the frontoparietal and insular cortex, receptor messenger RNA dramatically decreased during postnatal life. Similarly, we found receptor messenger RNA expression in the cingulate, retrosplenial, perirhinal and infralimbic cortex with higher values during the first two weeks of development and decreased expression in the adult. However, receptor binding in the cerebral cortex, did not decrease during postnatal life. The differential profile of receptor messenger RNA expression and binding in the gerbil cortex and hippocampus during postnatal maturation suggest a role for AT1 receptors in the development and function of the corticohippocampal system.     

Postnatal development of GABA-mediated synaptic inhibition in rat hippocampus

Developmental alterations in GABAergic synaptic transmission were examined physiologically and biochemically in hippocampus of rats from 3 days of age to adulthood. Neither antidromic nor orthodromic stimulation could elicit identifiable inhibitory postsynaptic potentials in CA1 neurons in slices from rats 5 or 6 days of age. In contrast, at this age these stimuli result in large inhibitory postsynaptic potentials in CA3 pyramidal cells. In the latter cells orthodromic stimulation produced a brief monosynaptic excitatory postsynaptic potential which was followed by a large prolonged biphasic hyperpolarization. These signals were strikingly similar to those recorded in 1-month-old rats. In addition, large recurrent inhibitory postsynaptic potentials were produced by antidromic stimulation. By postnatal day 9 similar inhibitory postsynaptic potentials could be elicited in a majority of neurons of the CA1 subfield. As in mature pyramidal cells, application of GABA antagonists, such as bicuculline, selectively eliminated the antidromic inhibitory postsynaptic potential and the first component of the biphasic inhibitory postsynaptic potential generated by stimulation of stratum radiatum. In the CA3 subfield, this blockade of GABA receptors resulted in prolonged afterdischarges in slices from immature but not month-old rats. Measurements of the equilibrium potential and the conductance of antidromic inhibitory postsynaptic potentials in CA3 neurons were very similar when made during the first postnatal week and at 1 month of age. While on days 10-11 the equilibrium potential was very similar to measurements made at these other ages, the conductance was 3-4 times greater. The activity of glutamate decarboxylase, the synthetic enzyme for GABA, was very low at 3 days in hippocampus, and increased until 30 days of age at which time adult values were obtained. By comparison, hippocampal GABA levels were high early in postnatal life. Glutamate decarboxylase activities in microdissected CA3 and CA1 subfields were similar in immature hippocampus. These results demonstrate dramatic differences in the ontogenesis of functional GABAergic inhibitory synaptic transmission in the CA1 and CA3 subfields of rat hippocampus. The late development of GABA-mediated synaptic inhibition in the CA1 subfield could play a role in the susceptibility of immature hippocampus to seizures. However, the large GABA-mediated inhibitory postsynaptic potentials present in the CA3 subfield at the same age have a critical role in dampening neuronal excitability.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of pitavastatin against expression of S100β protein in the gerbil hippocampus after transient cerebral ischaemia

Aim and methods: We investigated the immunohistochemical alterations of S100β‐, S100‐, glial fibrillary acidic protein (GFAP)‐ and isolectin B₄‐positive cells in the hippocampus after 5 min of transient cerebral ischaemia in gerbils. We also examined the effect of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A (HMG‐CoA) reductase inhibitor pitavastatin against neuronal damage in the hippocampal CA1 sector after ischaemia. Results: Severe neuronal damage was observed in the hippocampal CA1 pyramidal neurons from 5 days after ischaemia. GFAP‐positive cells increased gradually in the hippocampus from 5 days after ischaemia. Five and 14 days after ischaemia, significant increases in the number of GFAP‐positive cells and isolectin B₄‐positive cells were observed in the hippocampal CA1 and CA3 sector. Mild increases in the number of S100 and S100β‐positive cells were observed in the hippocampal CA1 sector from 1 h to 2 days after ischaemia. Thereafter, S100β‐positive cells increased in the hippocampal CA1 sector after ischaemia, whereas S100‐positive cells decreased in this region. In our double‐labelled immunostainings, S100 and S100β immunoreactivity was found in GFAP‐positive astrocytes, but not in isolectin B₄‐positive microglia. Pharmacological study showed that HMG‐CoA reductase inhibitor, pitavastatin, can protect against the hippocampal CA1 neuronal damage after ischaemia. This drug also prevented increases in the number of GFAP‐positive astrocytes, isolectin B₄‐positive microglia, S100‐positive astrocytes and S100β‐positive astrocytes after ischaemia. Conclusion: The present study demonstrates that pitavastatin can decrease the neuronal damage of hippocampal CA1 sector after ischaemia. This beneficial effect may be, at least in part, mediated by inhibiting the expression of astrocytic activation in the hippocampus at the acute phase after ischaemia. Thus the modulation of astrocytic activation may offer a novel therapeutic strategy of ischaemic brain damage.     

Rats exposed to cocaine during late gestation and early postnatal life show deficits in hippocampal pyramidal and granule cells in later life

In humans, the offspring of maternal cocaine misusers are known to have subtle cognitive and motor impairments in later life. It was therefore hypothesized that such exposure in animals would also affect the morphological structure of the brain. This possibility was investigated by exposing rats to cocaine between embryonic day 15 and postnatal day 6. Samples of the cocaine-exposed and control rats were killed for examination at 22 and 150 postnatal days of age. Stereological procedures (the Cavalieri principle together with the physical disector method) were utilized to estimate the total number of pyramidal and granule cells in defined regions of the hippocampal formation. At 22 days of age, the control offspring had about 373 000 pyramidal cells whereas the cocaine-treated animals only had about 310,000 cells in the CA1 + CA2 + CA3 region. By 150 days of age the values were about 396,000 and 348,000, respectively. The differences between age-matched groups were statistically significant. There were about 626,000 and 687,000 dentate gyrus granule cells in the 22-day-old control and cocaine-treated groups, respectively. By postnatal day 150 the control rats had about 832,000 granule cells whilst the cocaine-treated rats had about 693,000. There was a significant main effect of age as well as group-age interaction in this measure. These results show that even moderate exposure to cocaine during the late gestation and early postnatal period in rats is a potent teratogen and can markedly influence the development of neurons in the hippocampal formation.     

Gerbil Angiotensin II AT1 receptors are highly expressed in the hippocampus and cerebral cortex during postnatal development

Increasing evidence suggests that Angiotensin II, classically known from its many effects regulating salt and water homeostasis, is also involved in brain development and cognitive functions through activation of AT₁ Angiotensin II receptors. The recently cloned gerbil AT₁ receptor is expressed in brain areas controlling hydro-mineral homeostasis, and particularly highly expressed in limbic areas such as the hippocampal formation. We quantified the gerbil AT₁ receptor messenger RNA expression and receptor binding by quantitative in situ hybridization and receptor autoradiography, respectively, in the hippocampal formation and cerebral cortex of gerbils during postnatal development. The receptor messenger RNA and binding were present from birth and showed a gradual and sustained increase through postnatal maturation in the CA1 and CA2 regions of the hippocampus and in the dentate gyrus. Conversely, in the CA3 region, no binding was detected while receptor messenger RNA peaked at 15 days after birth and disappeared in the adult. The highest receptor messenger RNA expression and binding were found in the septomedial portions of the CA1 region and at septal levels of the CA2 region.We detected the highest receptor messenger RNA expression at postnatal day one in the frontolateral pole of the cerebral hemispheres. In these areas, and in the frontoparietal and insular cortex, receptor messenger RNA dramatically decreased during postnatal life. Similarly, we found receptor messenger RNA expression in the cingulate, retrosplenial, perirhinal and infralimbic cortex with higher values during the first two weeks of development and decreased expression in the adult. However, receptor binding in the cerebral cortex, did not decrease during postnatal life.The differential profile of receptor messenger RNA expression and binding in the gerbil cortex and hippocampus during postnatal maturation suggest a role for AT₁ receptors in the development and function of the corticohippocampal system.     

Structural characteristics of astrocytes from the rat hippocampus in postischemia

The aim of this investigation was to study the distribution and structural organization of rat hippocampal astrocytes containing immunoreactive glial fibrillary acidic protein (GFAP) after ischemic damage of the brain in the animals treated with intraventricular infusion of creatine as a neuroprotective drug, and in those which received no treatment. Using the methods of light microscopy and immunocytochemistry, the brain of 26 mature Sprague-Dawley (Koltushi) rats was studied. Some animals were narcotized and subjected to general brain ischemia (lasting for 12 min) followed by a reperfusion (for 7 days). Creatine was infused intraventricularly to 11 animals using an automatic Alzet osmotic minipump. It was found that GFAP-immunoreactive hippocampal astrocytes were concentrated within two major areas (stratum lacunosum-moleculare CA1 and fascia dentata stratum polymorphae). As a result of neuroprotective effect of creatine, moderate ischemic damage of the hippocampus was not followed by the changes in the zones of activated astrocyte localization. Redistribution of GFAP-positive astrocytes in postischemic period was caused by the loss of pyramidal neurons in cytoarchitectonic field CA1. Complete loss of pyramidal neurons in this hippocampal area resulted in a qualitatively new level of astrocyte activation--their proliferation.     

局灶性脑缺血大鼠脑组织皮质运动区和海马星形胶质细胞的动态变化

目的 观察大鼠局灶性脑缺血后皮质运动区和海马星形胶质细胞的变化。方法 雄性SD大鼠144只,按随机数字法分成正常组、假手术组和手术组,每组48只。手术组用大脑中动脉电凝术(MCAO)建立局灶性脑缺血模型;假手术组的操作步骤和手术组相同,只是不将暴露的大脑中动脉凝闭;正常组不做任何处理。应用免疫组化检测正常组、假手术组以及手术组术后1、2、3、5、7、14、28、56 d皮质运动区和海马星形胶质细胞神经胶质酸性蛋白(GFAP)表达的变化。结果与正常组和假手术组比较,手术组大鼠缺血侧和健侧MCAO术后皮质运动区GFAP阳性细胞计数术后第1天明显降低,第3天开始升高,缺血侧和健侧分别于术后第7天、第5天升至最高(85.6±3.3、75.3±2.9),随后逐渐下降并均在术后第14天出现第2个低谷,其后又开始逐渐上升接近正常。与正常组和假手术组比较,手术组海马CA1区GFAP阳性细胞计数缺血侧和健侧自术后第1天即开始升高,术后第7天升至最高( 106.5±3.6、108.4±3.0),其后进入平台期;CA2区、CA3区缺血侧和健侧术后第3天开始明显升高,CA2区缺血及健侧最高值则分别出现在术后第5天(106.9±4.4)、第7天(107.5±3.8);CA3区为第5天(130.9±3.7)、第5天(129.2±4.0),术后第14天开始下降,但仍然高于正常组和假手术组。结论 大鼠局灶性脑缺血后,不同脑区星形胶质细胞的表达随时间变化的模式不同,在皮质运动区存在两谷一峰的现象,在海马表达逐渐增强,并维持在一个较高的水平,这种差别可能与不同脑区神经的可塑性有关。     

Effect of pitavastatin against expression of S100beta protein in the gerbil hippocampus after transient cerebral ischaemia

AIM AND METHODS: We investigated the immunohistochemical alterations of S100beta-, S100-, glial fibrillary acidic protein (GFAP)- and isolectin B4-positive cells in the hippocampus after 5 min of transient cerebral ischaemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor pitavastatin against neuronal damage in the hippocampal CA1 sector after ischaemia. RESULTS: Severe neuronal damage was observed in the hippocampal CA1 pyramidal neurons from 5 days after ischaemia. GFAP-positive cells increased gradually in the hippocampus from 5 days after ischaemia. Five and 14 days after ischaemia, significant increases in the number of GFAP-positive cells and isolectin B4-positive cells were observed in the hippocampal CA1 and CA3 sector. Mild increases in the number of S100 and S100beta-positive cells were observed in the hippocampal CA1 sector from 1 h to 2 days after ischaemia. Thereafter, S100beta-positive cells increased in the hippocampal CA1 sector after ischaemia, whereas S100-positive cells decreased in this region. In our double-labelled immunostainings, S100 and S100beta immunoreactivity was found in GFAP-positive astrocytes, but not in isolectin B4-positive microglia. Pharmacological study showed that HMG-CoA reductase inhibitor, pitavastatin, can protect against the hippocampal CA1 neuronal damage after ischaemia. This drug also prevented increases in the number of GFAP-positive astrocytes, isolectin B4-positive microglia, S100-positive astrocytes and S100beta-positive astrocytes after ischaemia. CONCLUSION: The present study demonstrates that pitavastatin can decrease the neuronal damage of hippocampal CA1 sector after ischaemia. This beneficial effect may be, at least in part, mediated by inhibiting the expression of astrocytic activation in the hippocampus at the acute phase after ischaemia. Thus the modulation of astrocytic activation may offer a novel therapeutic strategy of ischaemic brain damage.     

Effects of maternal thiamine deficiencies on the pyramidal and granule cells of the hippocampus of rat pups

To understand the implication of thiamine deficiency in the neuronal atrophy and cell death we undertook to induce thiamine (B1 vitamine) deficiency during three essential periods of the ontogenesis of rat central nervous system (CNS). Female rats were fed with a thiamine deprived diet during the gestation and lactation, and the fetuses and pups were alternately exposed to prenatal, perinatal or postnatal thiamine deficiencies. On the 45th postnatal day, histological studies were done on the brains of the pups and the structure of the hippocampus was analyzed. The effects of each treatment were assessed by measuring the size and the density of cell nuclei throughout the dentate gyrus and fields CA4, CA3 and CA1 of the hippocampal formation. The hippocampus showed a regional vulnerability in the pups exposed to maternal thiamine deficiencies. It appears that the thiamine deficiency decreased nuclear density (27.20%) more severely than nuclear size (10.56%) in the fetal hippocampus. Consequently, the major part of the teratogenic effects of thiamine deficiency was cellular death, rather than cellular atrophy.     

Transient increase of tenascin-C in immature hippocampus: astroglial and neuronal expression

Summary In the present report we describe the anatomical localization of cells expressing tenascin-C, an extracellular matrix glycoprotein, in the hippocampal complex of developing rats. We report a development-dependent down regulation of both tenascin-C protein and mRNA. The highest levels of expression of tenascin-C was observed in rat pups from embryonic day 18 to postnatal day 7. Double labelling experiments performed with a tenascin-C antibody or tenascin-C probes combined with specific markers of astrocytes (GFAP) or neurons (MAP2 and Tau) allowed us to demonstrate that tenascin-C is expressed by both immature astrocytes and neurons in immature hippocampus. The temporal and topographic distribution of cells expressing of post-mitotic cells. In view of these data we discuss the hypothesis that tenascin-C, as a mediator of neuron-glia interaction, may contribute to the development of hippocampal cells.     

Spatiotemporal Expression of HDAC2 during the Postnatal Development of the Rat Hippocampus

Background: Histone acetylation, which is a chromatin modification of histone tails, can dynamically regulate the expression of various genes in normal development. HDAC2 is a negative regulatory factor of acetylation and closely related to learning and memory. NSE is a nerve marker and vital for maintaining physiological functions in nervous system. Currently, few studies associated with the expression pattern of HDAC2 in postnatal rat hippocampus have been reported. This study aimed to explore the temporal and spatial expression pattern of HDAC2, helping to reveal the expression characteristics of HDAC2 during postnatal neuronal maturation. Materials and Methods: With NSE as a biomarker of neuronal maturation at postnatal days 1, 3, 7 and weeks 2, 4, and 8 (P1D, P3D, P7D, P2W, P4W, P8W), the expression patterns of HDAC2 in rat hippocampus were examined using real-time PCR and western blotting. Additionally, the subcellular distribution of HDAC2 was analysed by immunofluorescence. Results: We found that HDAC2 was highly expressed in the neonatal period and decreased gradually. HDAC2 expression was widely distributed in neurons of hippocampal CA1, CA3 and DG regions and gradually shifted from the nucleus to the cytoplasm during postnatal development. Altogether, the expression of HDAC2 decreased gradually with different subcellular localizations throughout development. Conclusions: The observed results indicate that the expression levels of HDAC2 become lower and with different subcellular localizations in neurons during hippocampal neuronal maturation, suggesting the specific expression characteristics of HDAC2 might play an important role during postnatal learning-memory function and development.     

Increase in GFAP‐positive astrocytes in histone demethylase GASC1/KDM4C/JMJD2C hypomorphic mutant mice

GASC1, also known as KDM4C/JMJD2C, is a histone demethylase for histone H3 lysine 9 (H3K9) and H3K36. In this study, we observed an increase of GFAP‐positive astrocytes in the brain of Gasc1 hypomorphic mutant mice at 2–3 months of age, but not at postnatal day 14 and day 30 by immunohistochemistry. Increases of GFAP‐positive astrocytes were widely observed in the forebrain and prominent in such regions as cerebral cortex, caudate putamen, amygdala and diencephalon, but not obvious in hippocampus. Taken together with our observations to be published elsewhere that Gasc1 hypomorphic mutant mice exhibit abnormal behaviors including hyperactivity, persistence and many types of learning and memory deficits and abnormal synaptic functions such as prolonged long‐term potentiation, the increase in GFAP‐positive astrocytes may help understand their phenotypes, because astrocytes are known to affect synaptic plasticity.     

Long-term changes in calbindin D(28K) immunoreactivity in the rat hippocampus after cardiac arrest

Calbindin D(28K) (CB) expression was analyzed in the rat hippocampus following 10-min-cardiac arrest-induced ischemia within a year after reperfusion. In rats examined 3 days after ischemia, CB immunoreactivity disappeared completely from CA1 pyramidal neurons and from most CA2 pyramids. In the stratum granulosum of the dentate gyrus, mossy fibers, and hippocampal interneurons, CB immunoreactivity was preserved, although staining was somewhat paler than that in control rats. A similar pattern of CB immunoreactivity was found in rats sacrificed 14 days and 1 month after cardiac arrest. From the 14th postischemic day, neuronal loss in the stratum pyramidale of CA1 but not in that of CA2 became apparent. The reappearance of CB immunoreactivity in CA1 and CA2 pyramidal neurons was noticed 6 months after ischemia, and the pattern was identical to that observed in animals sacrificed 12 months after the ictus. The prolonged loss and delayed reappearance of CB immunoreactivity in the hippocampus demonstrate that ischemia may induce long-term disturbances of protein expression, which may in turn result in impairment of hippocampal functioning.     

Changes of synapsin I messenger RNA expression during rat brain development

Synapsin I is a synaptic phosphoprotein that is involved in the short-term regulation of neurotransmitter release. In this report we present the first extensive study of the developmental expression of its corresponding messenger ribonucleic acid (mRNA) by in situ hybridization and northern blot analysis in rat brain. Synapsin I mRNA showed pronounced differences in expression in different brain regions during postnatal development. The early expression of synapsin I mRNA in ontogenetically older regions such as the thalamus, the piriform cortex and the hippocampus coincides with the earlier maturation of these regions, in contrast to its later expression in ontogenetically younger areas such as the cerebellum and the neocortex. An intriguing expression pattern was found in the hippocampus. In all hippocampal subregions synapsin I mRNA expression increased from postnatal day (PND) 1 to 17. After PND 17, however, there was a marked dissociation between persisting high expression levels in CA3 and the dentate gyrus and a strong decline in synapsin I mRNA expression in CA1. The persistence of synapsin I in some adult rat brain regions indicates that it plays a part in synapse formation during plastic adaption in neuronal connectivities.     

大鼠生后中枢神经系统S100B和胶质纤维酸性蛋白表达的变化

目的 探讨SD大鼠生后中枢神经系统发育过程中S100B和胶质纤维酸性蛋白(GFAP)的表达变化.方法 24只雄性SD大鼠分为生后7d、14d、21d和成年4组,用免疫组织化学方法对脑、脊髓切片进行S100B、GFAP抗体染色,观察不同时间点不同部位中两种阳性细胞平均数.结果 生后7d到成年,前额皮质、海马、纹状体、黑质和脊髓S100B阳性标记的密度和数量逐渐减少,生后2～3周时渐趋于稳定;脑内GFAP阳性星形胶质细胞(AST)随年龄增大逐渐增多,突起增粗增长,生后21d GFAP阳性细胞数量已接近成年;相反,脊髓GFAP阳性标记数则随年龄增长呈现由多到少的趋势;海马CAl区生后各年龄段GFAP和S100B免疫荧光双标显示,生后1周至成年S100B阳性细胞的数量明显减少,尤以分子层明显;随年龄增长,双标阳性细胞的比例逐渐增高,多集中分布于锥体细胞层和多形层.结论 大鼠中枢神经系统中S100B和GFAP两种星形胶质细胞蛋白存在不同的表达模式;同时S100B和GFAP蛋白的表达在发育过程中可能受不同机制的调节,并可能代表星形胶质细胞的不同亚型.     

Pregnenolone and dehydroepiandrosterone administration in neonatal rats alters the immunoreactivity of hippocampal synapsin I, neuropeptide Y and glial fibrillary acidic protein at post-puberty

It is well documented that neurosteroids administered during the neonatal period influence the development of several brain systems. In our previous study, pregnenolone administered to rats during the neonatal period altered adenosinergic and dopaminergic functions in the striatum and cerebral cortex. The present study examined the effects of the treatment with pregnenolone and dehydroepiandrosterone (DHEA) from the postnatal day (P) 3-P7 on synapsin I (a marker for presynaptic terminals) and glial fibrillary acidic protein (GFAP: a marker for astroglia) levels in the hippocampus of Sprague-Dawley rats at 3 and 7 weeks of age. In addition, neuropeptide Y and dynorphin A immunoreactivity was measured. The administration of pregnenolone and DHEA to neonatal rats significantly altered the expression of synapsin I in the dentate gyrus and CA3 region at post-puberty but not at pre-puberty. A significantly greater expression of GFAP-immunoreactive astrocytes or processes was demonstrated in the pregnenolone- and DHEA-treated groups at both pre-puberty and post-puberty. A significant increase in the number and size of GFAP-immunoreactive astrocytes and in the extension of arborization was seen in the overall hippocampus. The number of neuropeptide Y-positive cells in the hilus region was also significantly increased in the neurosteroid-treated group at post-puberty. No differences were detected in dynorphin A immunoreactivity among the experimental groups. These results of this study suggest that pregnenolone and DHEA play an important role in the development of hippocampus.     

Image analysis of GFA-positive astrocytes from adolescence to senescence

Summary Smears of fresh rat brain tissue combined with immunohistochemistry using antiserum to glial fibrillary acidic protein (GFA) were used to visualize individual astrocytes in different cortical regions of rats ranging in age from 1 to 30 months. By computerized image analysis, the cell area and the cell perimeter were determined. Using 4-month-old male Sprague-Dawley rats, it was found that GFA-positive astrocytes from cerebellum and hippocampus were significantly larger, both in terms of cell area and cell perimeter, than similar cells from cortex cerebri. The temporal development was carefully followed in smears of the hippocampal formation where a continuous increase in cell size was observed from 1 to 30 months of age. During the first few postnatal months a rapid increase in both cell area and cell perimeter was observed using Sprague-Dawley rats. For studies of senescent animals, Fisher 344 rats specifically bred for aging studies were obtained. Using such animals, a second, highly significant slower growth phase which continued until the longest time points studied was observed. A separate experiment using Sprague-Dawley rats also showed large differences in both cell area and cell perimeter of GFA-positive cerebellum and cortical astrocytes taken from 6-week- and 18-month-old animals. In conclusion, the present study shows that maturation of GFA-positive astrocytes is a process which continues for several months postnatally. This relatively rapid growth phase is followed by a slower increase in cell size, probably continuing throughout life.     

Complex and region-specific changes in astroglial markers in the aging brain

Morphological aging of astrocytes was investigated in entorhinal cortex (EC), dentate gyrus (DG), and cornu ammonis 1 (CA1) regions of hippocampus of male SV129/C57BL6 mice of different age groups (3, 9, 18, and 24 months). Astroglial profiles were visualized by immunohistochemistry by using glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), and s100β staining; these profiles were imaged using confocal or light microscopy for subsequent morphometric analysis. GFAP-positive profiles in the DG and the CA1 of the hippocampus showed progressive age-dependent hypertrophy, as indicated by an increase in surface, volume, and somata volume at 24 months of age compared with 3-month-old mice. In contrast with the hippocampal regions, aging induced a decrease in GFAP-positive astroglial profiles in the EC: the surface, volume, and cell body volume of astroglial cells at 24 months of age were decreased significantly compared with the 3-month group. The GS-positive astrocytes displayed smaller cellular surface areas at 24 months compared with 3-month-old animals in both areas of hippocampus, whereas GS-positive profiles remained unchanged in the EC of old mice. The morphometry of s100β-immunoreactive profiles revealed substantial increase in the EC, more moderate increase in the DG, and no changes in the CA1 area. Based on the morphological analysis of 3 astroglial markers, we conclude that astrocytes undergo a complex age-dependent remodeling in a brain region–specific manner.     

Structural organization of astrocytes in the rat hippocampus in the post-ischemic period

The aim of the present work was to study the location and structural organization of astrocytes in the rat hippocampus, which contain immunoreactive glial fibrillary acid protein (GFAP) after ischemic damage to the brain after intracerebroventricular administration of the neuroprotective agent creatine and without treatment. Light microscopy and immunocytochemical methods were used to study the brains of 26 adult male Sprague-Dawley (Koltushi) rats, some of which were subjected to total cerebral ischemia (12 min) under anesthesia with subsequent reperfusion (seven days). Creatine was given to 11 animals intracerebroventricularly using an osmotic pump (Alzet Osmotic Mini-Pump). The results showed that GFAP-immunoreactive hippocampal astrocytes were concentrated in two main zones (the stratum lacunosummoleculare of field CA1 and the stratum polymorphae of the dentate fascia). The neuroprotective effect of creatine had the result that moderate ischemic damage to the hippocampus did not lead to changes in the zones containing activated astrocytes. The redistribution of GFAP-positive astrocytes in the post-ischemic period was associated with loss of pyramidal neurons in cytoarchitectonic field CA1. Complete loss of pyramidal neurons in this area of the hippocampus leads to a qualitatively new level of astrocyte activation - proliferation.Translated from Morfologiya, Vol. 125, No. 2, pp. 19–21, March–April, 2004.