Humans ; Epilepsy, Temporal Lobe/surgery* ; Mossy Fibers, Hippocampal ; Brain-Derived Neurotrophic Factor ; Dentate Gyrus

OBJECTIVEData accumulated over the past years have led to widespread recognition that neurogenesis, the emergence of new neurons, persists in the hippocampal dentate gyrus of the adult mammalian brain, and can be increased by seizures in multiple models. Also, aberrant reorganization of dentate granule cell axons, the mossy fiber sprouting, occurs in human temporal lobe epilepsy and rodent epilepsy models. However a number of studies suggest that the immature brain is less vulnerable to the morphologic alteration of hippocampus after seizures. The goal of this study was to determine whether the seizures can induce dentate granule cell neurogenesis and mossy fiber sprouting in the immature rat.

METHODSSeizures was elicited by unilateral microinfusion of kainic acid (KA, 1 micro g) into the amygdula at postnatal day 15 (P15). Rat pups were given bromodeoxyuridine (BrdU) intraperitoneally on day 5 after KA administration and killed 7 d or 21 d later. The brains were processed for BrdU mitotic labeling combined with double-label immunohistochemistry using neuron-specific, early differentiation marker TuJ1 (betaIII tubulin) or granule-specific marker CaBP (calcium-binding protein calbindin D28k) as well as glia-specific marker GFAP (glial fibrillary acidic protein). Mossy fiber sprouting in intermolecular layer and CA3 subfield was assessed in Timm-stained sections both 1 month and 3 months after KA administration by using a rating scale and density measurement.

RESULTSThe dentate BrdU-immunoreactive cells of the KA-treated rats increased significantly compared with those of control rats on day 7 and 21 after BrdU administration (7 d: 244 +/- 15 vs. 190 +/- 10; 21 d: 218 +/- 19 vs. 133 +/- 12, P < 0.05). Approximately 80.2% and 78.7% of BrdU-labeled cells coexpressed TuJ1 in KA-treated rats and control rats on day 7 after BrdU respectively (P > 0.05). On 21 d after BrdU, 60.2% and 58.2% of dentate BrdU-labeled cells coexpressed GaBP in KA-treated rats and control rats respectively (P > 0.05). GFAP colocalized with 3%-5% dentate BrdU-labeled cells in the rats of both groups on day 7 and 21 after BrdU. It was also demonstrated that status epilepticus at P15 did not result in any detectable mossy fiber sprouting within the hippocampus both 1 month and 3 months after KA administration.

CONCLUSIONSKA induced seizures can increase granule cell neurogenesis in the immature rat. Most of newly appeared cells migrate from subgranular proliferation zone (SGZ) into granule cell layer, the hilus as well as the molecular layer, and there they can differentiate into granule neurons. These observations also indicate that there is an early developmental resistance to seizure-induced mossy fiber sprouting in the immature brain.

Animals ; Cell Differentiation ; Cell Proliferation ; Dentate Gyrus ; cytology ; physiopathology ; Disease Models, Animal ; Excitatory Amino Acid Agonists ; adverse effects ; Kainic Acid ; adverse effects ; Mossy Fibers, Hippocampal ; physiopathology ; Neurogenesis ; physiology ; Rats ; Seizures ; chemically induced ; physiopathology

No abstract available.
Brain Injuries* ; Brain* ; Dentate Gyrus*

PURPOSE: The expression of c-Fos protein has been shown to be a useful marker for elevated levels of neuronal activity generated in the brain following different stimuli, including seizures. This study was conducted to investigate distribution and numbers of neurons where dentate and cingulate gyrus become activated following pentylenetetrazol-induced seizures by means of expression patterns of c-Fos protein. METHODS: Rats were sacrificed at increasing times(1 hour, 2 hours, 8 hours, 1 day, 4 days and 7 days) after pentylenetetrazol-induced seizure. Rat brains were removed and sliced in rat brain matrix. Brain slices were coronal sectioned at interaural 5.70-6.70mm. Serial sections were immunohistochemically reacted with polyclonal c-Fos antibody. The distribution and numbers of c-Fos protein immunoreactive neurons in dentate gyrus and cingulate gyrus were examined and analyzed statistically with Mann-Whitney U test. RESULTS: The numbers of c-Fos protein immunoreactive neurons in dentate gyrus peaked at 1 hours and reached almost normal conditions at 7 days after seizure. Also, same patterns were occurred in cingulate gyrus. Concentration value that pentylenetetrazol can induce was different from each animals and c-Fos immunoreactive cells were various kinds of neurons. CONCLUSION: Higher numbers of c-Fos protein immunoreactive neurons were found in dentate and cingulate gyrus at the same times after seizure. These findings suggest that neurons of dentate and cingulate gyrus play a crucial role in seizure onset following pentylenetetrazol-induced seizure.
Animals ; Brain* ; Dentate Gyrus ; Gyrus Cinguli ; Neurons ; Pentylenetetrazole ; Rats* ; Seizures*

OBJECTIVEKetogenic diet (KD) is a high fat, low protein, low carbohydrate diet. Its antiepileptic effect is certain but the underlying mechanism is unknown. The aim of the study was to reveal the possible mechanism from the view points of synaptic reorganization and GluR(5) expression in hippocampus.

METHODSEpilepsy was induced in Sprague-Dawley rats by kainic acid at postnatal day 28, all control animals were fed with normal rodent chow, whereas experimental rats were fed with ketogenic feed for 8 weeks. Spontaneous recurrent seizures were recorded. Mossy fiber sprouting and neuron damage in hippocampus were investigated by Timm staining and Nissl staining. Western blot and RT-PCR methods were applied to detect the expression of GluR(5) and GluR(5) mRNA in hippocampus.

RESULTSKD-fed rats (1.40 +/- 1.03) had significantly fewer spontaneous recurrent seizures than control diet-fed rats (7.36 +/- 3.75). The mean A of mossy fiber sprouting in the inner molecular layer of dentate gyrus was markedly higher in KA induced animals than that in saline control animals but it was similar in different diet fed groups. No significant differences were found in the mean A of Timm staining in CA(3) area and Nissl staining of neuron in hilus, CA(3) and CA(1) area. After KA kindling, KD-fed animals [(189.38 +/- 40.03)/mg pro] had significantly higher GluR(5) expression in hippocampus than control diet-fed animals [(128.79 +/- 46.51)/mg pro] although their GluR(5) mRNA was the same.

CONCLUSIONMossy fiber sprouting may be responsible for epileptogenesis in KA induced model and KD can suppress seizures in these animals. KD may upregulate young rat GluR(5) in inhibitory interneurons of CA(1) thus lead to an increased inhibition to prevent the propagation of seizure.

Animals ; Blotting, Western ; CA1 Region, Hippocampal ; metabolism ; pathology ; CA3 Region, Hippocampal ; metabolism ; pathology ; Chromosome Pairing ; drug effects ; Dentate Gyrus ; metabolism ; pathology ; Diet, Ketogenic ; methods ; Disease Models, Animal ; Epilepsy ; chemically induced ; diet therapy ; genetics ; metabolism ; pathology ; Excitatory Amino Acid Agonists ; Hippocampus ; drug effects ; metabolism ; pathology ; Kainic Acid ; Male ; Mossy Fibers, Hippocampal ; metabolism ; pathology ; Pyramidal Cells ; metabolism ; pathology ; RNA, Messenger ; metabolism ; Rats ; Receptors, Kainic Acid ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction

Amnesic patients who have damage in the hippocampus and in associated areas in the medial temporal lobe suffer from remembering specific events that may or may not share similar objects and locations. Computational models, behavioral studies, and physiological findings all suggest that neural circuits in the hippocampus are suitable for representing seemingly similar events as distinctively different individual event memories. This article offers a selective review on this particular function of the hippocampus and its associates areas such as the perirhinal cortex, mostly centering upon lesion studies and physiological studies using animals. We also present recent experimental results showing that the dentate gyrus subfield of the hippocampus and perirhinal cortex are particularly important for discriminating similar paired associates between same objects and different locations, or vice versa.
Animals ; Brain ; Dentate Gyrus ; Hippocampus ; Humans ; Temporal Lobe

Stress induces degeneration of brain structures and functions. Particularly, hippocampus is sensitive to stressful stimulations. In the present study, the change of synaptic related molecules in the mouse dentate gyrus was examined with immunohistochemistry after restraint stress. We subjected mice to restraint stress for 6 h per day for 4 days. As a result, the number of Ki-67, a marker for proliferation, and doublecortin (DCX), a marker for neurogenesis, immunoreactive cells was decreased in the stress group. On the other hand, the intensity of calbindinD-28k, a marker of pre-existing granule cells, immunoreactivity was increased in the granule cell layer after 4 days restraint stress. As well as, the immunoreactivity of synaptic related molecules, postsynaptic density-95 (PSD-95), growth association protein-43 (GAP-43) and beta-NADPH-d reactivity were increased in the inner molecular layer of dentate gyrus after 4 days restraint stress. In conclusion, this study shows that repeated restraint stress suppresses neurogenesis in dentate gyrus and strengthens synaptic plasticity of existing granule cells.
Animals ; Brain ; Dentate Gyrus* ; Hand ; Hippocampus ; Immunohistochemistry ; Mice* ; Neurogenesis ; Plastics*

PURPOSE: To investigate the effect of low dose radiation on neuronal cell proliferation in diabetic rats. MATERIALS AND METHODS: A group of rats (first group) were divided into three subgroups (nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy groups) to determine the effect of radiation on normal hippocampal neuronal cell proliferation. A further group of rats (second group) were divided into six subgroups (nondiabetic control, diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy groups) to determine the effect of radiation on hippocampal neuronal cell proliferation under diabetic conditions. Using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), the number of neuronal cells in the dentate gyrus of all the groups was counted. RESULTS: The number of BrdU-positive cells in the dentate Gyrus of the nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy subgroups of the first group were 45.96+/-3.42, 59.34+/-5.20 and 19.26+/-2.98/mm2, respectively. The number of BrdU-positive cells in the dentate gyrus of the diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy subgroups of the second group were 55.44+/-8.57, 33.33+/-6.46, 67.75+/-10.54, 66.63+/-10.05, 23.59+/-6.37 and 14.34+/-7.22/mm2, respectively. CONCLUSION: Low dose radiation enhances cell proliferation in the dentate gyrus of STZ-induced diabetic rats.
Animals ; Bromodeoxyuridine ; Cell Proliferation* ; Dentate Gyrus ; Hippocampus ; Immunohistochemistry ; Neurons* ; Rats*

PURPOSE: To investigate the effect of low dose radiation on neuronal cell proliferation in diabetic rats. MATERIALS AND METHODS: A group of rats (first group) were divided into three subgroups (nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy groups) to determine the effect of radiation on normal hippocampal neuronal cell proliferation. A further group of rats (second group) were divided into six subgroups (nondiabetic control, diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy groups) to determine the effect of radiation on hippocampal neuronal cell proliferation under diabetic conditions. Using immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU), the number of neuronal cells in the dentate gyrus of all the groups was counted. RESULTS: The number of BrdU-positive cells in the dentate Gyrus of the nondiabetic control, nondiabetic 0.1 Gy and nondiabetic 10 Gy subgroups of the first group were 45.96+/-3.42, 59.34+/-5.20 and 19.26+/-2.98/mm2, respectively. The number of BrdU-positive cells in the dentate gyrus of the diabetic control, diabetic 0.01 Gy, diabetic 0.1 Gy, diabetic 1 Gy and diabetic 10 Gy subgroups of the second group were 55.44+/-8.57, 33.33+/-6.46, 67.75+/-10.54, 66.63+/-10.05, 23.59+/-6.37 and 14.34+/-7.22/mm2, respectively. CONCLUSION: Low dose radiation enhances cell proliferation in the dentate gyrus of STZ-induced diabetic rats.
Animals ; Bromodeoxyuridine ; Cell Proliferation* ; Dentate Gyrus ; Hippocampus ; Immunohistochemistry ; Neurons* ; Rats*

PURPOSE: This study evaluated the extent of damage due to hypothermia in the mature and immature brain. METHODS: Hippocampal tissue cultures at 7 and 14 days in vitro (DIV) were used to represent the immature and mature brain, respectively. The cultures were exposed at 25degrees C for 0, 10, 30, and 60 minutes (n=30 in each subgroup). Propidium iodide fluorescent images were captured 24 and 48 hours after hypothermic injury. Damaged areas of the cornu ammonis 1 (CA1), CA3, and dentate gyrus (DG) were measured using image analysis. RESULTS: At 7 DIV, the tissues exposed to cold injury for 60 minutes showed increased damage in CA1 (P<0.001) and CA3 (P=0.005) compared to the control group at 48 hours. Increased damage to DG was observed at 24 (P=0.008) and 48 hours (P=0.011). The 14 DIV tissues did not demonstrate any significant differences compared with the control group, except for the tissues exposed for 30 minutes in which DG showed less damage at 48 hours than the control group (P=0.048). In tissues at 7 DIV, CA1 (P=0.040) and DG (P=0.013) showed differences in the duration of cold exposure. CONCLUSION: The immature brain is more vulnerable to hypothermic injury than the mature brain.
Animals ; Brain ; Dentate Gyrus ; Hippocampus ; Hypothermia, Induced* ; Neurons* ; Propidium ; Rats*