BACKGROUNDReplacement of spiral ganglion neurons would be one prioritized step in an attempt to restore sensory neuronal hearing loss. However, the possibility that transplanted neurons could regenerate new synaptic connections to hair cells has not been explored. The objective of this study was to test whether neural stem cell (NSC)-derived neurons can form synaptic connections with hair cells in vitro.

METHODSNSCs were mechanically separated from the hippocampus in SD rat embryos (E12-E14) and cultured in a serum-free medium containing basic fibroblast growth factor and epidermal growth factor. Rat NSCs were co-cultured with explants of cochlea sensory epithelia obtained from postnatal Day 3 rats under transway filter membrane.

RESULTSAt Day 3, the NSCs began to show chemotactic differentiation and grew toward cochlea sensory epithelia. After 9-day co-culture, neurites of NSC-derived neurons predominantly elongated toward hair cells. Immunohistochemical analyses revealed the fibers overlapped with synapsin and hair cells, indicating the formation of new synaptic connections. After 14-day culture, triple staining revealed the fibers overlapped with PSD95 (postsynaptic density) which is juxtaposed with CtBP2 (presynaptic vesicle), indicating the formation of new ribbon synapse.

CONCLUSIONSNSC-derived neurons can make synaptic connections with hair cells and provide a model for studying synaptic plasticity and regeneration. Whether the newly forming synapse is functional merits further electrophysiological study.

Animals ; Cell Differentiation ; drug effects ; Cells, Cultured ; Coculture Techniques ; Epidermal Growth Factor ; pharmacology ; Fibroblast Growth Factor 2 ; pharmacology ; Hair Cells, Auditory ; cytology ; drug effects ; ultrastructure ; Neural Stem Cells ; cytology ; drug effects ; ultrastructure ; Neurons ; cytology ; drug effects ; ultrastructure ; Rats ; Rats, Sprague-Dawley ; Synapses ; drug effects ; metabolism

The prenatal ethanol exposure induced the alterations of dendritic spine and synapse in visual cortex and their long-term effect would be investigated in mice from P0 to P30. Pregnant mice were intubated ethanol daily from E5 through the pup's birth to establish mode of prenatal alcohol abuse. The dendritic spines of pyramidal cells in visual cortex of pups were labeled with DiI diolistic assay, and the synaptic ultrastructure was observed under transmission electron microscope. Prenatal alcohol exposure was associated with a significant decrease in the number of dendritic spines of pyramidal neurons in the visual cortex and an increase in their mean length; ultrastructural changes were also observed, with decreased numbers of synaptic vesicles, narrowing of the synaptic cleft and thickening of the postsynaptic density compared to controls. Prenatal alcohol exposure is associated with long-term changes in dendritic spines and synaptic ultrastructure. The changes were dose-dependent with long term effect even at postnatal 30.
Animals ; Dendritic Spines ; ultrastructure ; Ethanol ; toxicity ; Female ; Fetal Alcohol Spectrum Disorders ; etiology ; pathology ; Male ; Mice ; Mice, Inbred C57BL ; Microscopy, Confocal ; Microscopy, Electron, Transmission ; Pregnancy ; Prenatal Exposure Delayed Effects ; pathology ; Pyramidal Cells ; ultrastructure ; Synapses ; ultrastructure ; Visual Cortex ; ultrastructure

OBJECTIVETo observe the effects of hyperbaric oxygen (HBO) on synaptic ultrastructure and the synaptophysin expression (p38) in hippocampal CA3 after hypoxia-ischemic brain damage (HIBD) in neonatal rats.

METHODSThe rat model of HIBD was made by the method of Bjelke and divided randomly into two groups (n = 10)--HIBD group and HBO-treated HIBD group. Another 20 rats underwent sham-operation and were also divided randomly into HBO-treated control group and the control group. After 24 h of the operation, the rats of the HBO-treated groups received HBO (2ATA, 1 h/d) for 14 days. When rats were 4 weeks old, the learning-memory ability of rats in every group was evaluated through water-maze test. Their hippocampal ultrastructure was observed with electron microscope and the p38 expression was detected immunohistochemically.

RESULTSCompared with the control group [(10.6 +/- 3.4) times], the water-maze learning ability of the rats in HIBD group [(15.5 +/- 4.9) times] was significantly decreased (P < 0.01), while the learning-memory ability of the HBO-treated HIBD group [(11.3 +/- 2.6) times] was significantly improved. There was no significant difference in the water-maze test between the HBO-treated HIBD group and the control group (P > 0.05). Compared with the control group, the ultrastructure of pyramidal neuron of hippocampal CA3 was distorted in HIBD group under the electron microscope. Compared with that in HBO-treated HIBD group (0.77 +/- 0.17, 0.67 +/- 0.16, 0.46 +/- 0.13, 0.86 +/- 0.14) and the control group (0.82 +/- 0.16, 0.70 +/- 0.16, 0.53 +/- 0.15, 0.91 +/- 0.17), the corrected optical densities (COD) of immunoreactive products of the hippocampal CA3 p38 were significantly decreased in HIBD group (0.41 +/- 0.19, 0.21 +/- 0.11, 0.08 +/- 0.03, 0.38 +/- 0.16) (P < 0.01). There was no significant difference in either ultrastructure or immunohistochemically reactive COD of p38 between the HBO-treated HIBD group and the control group (P > 0.05).

CONCLUSIONUnderlying the induction of synaptic plasticity and reducing the ultrastructural damage may be involved in the mechanism of HBO in the brain rehabilitation in perinatal brain damage with hypoxia-ischemia.

Animals ; Animals, Newborn ; Female ; Hippocampus ; metabolism ; pathology ; Hyperbaric Oxygenation ; Hypoxia-Ischemia, Brain ; metabolism ; pathology ; therapy ; Pregnancy ; Rats ; Rats, Sprague-Dawley ; Synapses ; metabolism ; ultrastructure ; Synaptophysin ; metabolism

Hair Cells, Auditory, Inner ; cytology ; Synapses ; physiology ; ultrastructure

BACKGROUNDThe effect of chronic stress on cognitive functions has been one of the hot topic in neuroscience. But there has been much controversy over its mechanism. Such single stressor applied in the past could not simulate complicated living circumstances that people confronted with. The aim of this study was to investigate the effects of chronic multiple-stress on learning and memory as well as on the levels of calcium/calmodulin-dependent protein kinase II (CaMKII), calmodulin (CaM) mRNA, and cAMP-response element binding protein (CREB) mRNA in the hippocampus of rats.

METHODSThe rats were divided randomly into stressed and control groups. The stressed group was given chronic multiple-stress for 6 weeks to set up a chronic multiple-stressed model. The rats' performance of spatial learning and memory was tested using Morris Water Maze (MWM) and Y-maze. Meanwhile, the expressions of CaMKII, CaM mRNA and CREB mRNA of rats' hippocampus were detected by immunohistochemistry, Western blot and reverse transcription-polymerase chain reaction (RT-PCR), respectively. In addition, the width of synaptic cleft and the thickness of post-synaptic densities (PSD) were observed in the hippocampal CA3 region of rats by electron microscopy.

RESULTSAfter exposure to chronic multiple-stress for 6 weeks, the ability of learning and memory of the stressed group was higher than that of the control group (P < 0.05, P < 0.01). The width of synaptic cleft was smaller and the thickness of PSD was larger in the hippocampal CA3 region of the stressed group than in that of the control group (P < 0.01). The CaMK II immunostaining of the stressed group was stronger than that of the control group in the stratum radiatum and oriens of the hippocampal CA1 and CA3, especially in the stratum oriens. Quantitative analysis indicated that the expression of CaMK II, CaM mRNA, and CREB mRNA in the hippocampus of the stressed group was higher than that of the control group (P < 0.05, P < 0.01).

CONCLUSIONSThe capacity of learning and memory can be enhanced after chronic multiple-stress. The increased levels of CaMK II, CaM mRNA, and CREB mRNA may contribute to the enhancing effect of chronic multiple-stress on learning and memory.

Animals ; Calcium-Calmodulin-Dependent Protein Kinase Type 2 ; Calcium-Calmodulin-Dependent Protein Kinases ; genetics ; Calmodulin ; genetics ; Chronic Disease ; Cyclic AMP Response Element-Binding Protein ; genetics ; Hippocampus ; metabolism ; ultrastructure ; Learning ; Male ; Memory ; Microscopy, Electron ; RNA, Messenger ; analysis ; Rats ; Rats, Wistar ; Stress, Physiological ; metabolism ; psychology ; Synapses ; ultrastructure

OBJECTIVETo investigate the synergistic effect of Schwann cells (SCs) and retinoic acid (RA) on differentiation and synaptogenesis of neural stem cells (NSCs) derived from hippocampus of neonatal rats.

METHODSThe classical method for 2x2 factorial analysis experiment was used to assess synergistic action of SCs and RA. NSCs were treated with RA, SCs, and SCs + RA in DMEM/F12 with 0.5% fetal bovine serum for six days, respectively. Double immunofluorescent staining was used to detect the differentiation of NSCs including nestin, glial fibrillary acidic protein (GFAP) and Map2. The expression of PSD95 was used to demonstrate synaptogenesis.

RESULTSAfter NSCs were treated with RA or SCs, the expression of nestin and GFAP was significantly decreased while the expression of Map2 and PSD95 was significantly increased in comparison with the control. Factorial ANOVA showed that interactions between SCs and RA could induce the expression of Map2 and PSD95.

CONCLUSIONSCs and RA could promote synergistically the neuronal differentiation and synaptogenesis of hippocampal neural stem cells in vitro while they decreased the astrocytes and nestin positive NSCs.

Animals ; Animals, Newborn ; Astrocytes ; cytology ; metabolism ; Cell Differentiation ; drug effects ; physiology ; Cells, Cultured ; Drug Synergism ; Fluorescent Antibody Technique ; Glial Fibrillary Acidic Protein ; metabolism ; Hippocampus ; cytology ; drug effects ; ultrastructure ; Intermediate Filament Proteins ; metabolism ; Nerve Tissue Proteins ; metabolism ; Nestin ; Neurons ; cytology ; drug effects ; ultrastructure ; Rats ; Rats, Sprague-Dawley ; Schwann Cells ; metabolism ; Stem Cells ; cytology ; drug effects ; ultrastructure ; Synapses ; drug effects ; physiology ; Tretinoin ; pharmacology

AIMTo observe the effect of fimbria-fornix (FF) transection on rat's hippocampal synaptic configuration.

METHODSAnimal models were produced by transecting rat's bilateral fimbria-fornix (FF). Y-type maze test were carried out respectively before and after the models were built, and emphasis was laid on the quantitative analyses of the parameters of synapses in the hippocampal CA3 areas.

RESULTSThe thickness of postsynaptic density material, the curvature of synaptic interface and the occurrence of perforated synapses decreased, while the width of synaptic cleft increased.

CONCLUSIONFimbria-fornix transection resulted in evident changes of the synaptic configuration in the hippocampal CA3 areas and we presume that the normal Ach level in the hippocampus plays a key role in maintaining the normal synaptic interface ultrastructure of the hippocampus CA3 area.

Animals ; CA3 Region, Hippocampal ; metabolism ; ultrastructure ; Fornix, Brain ; surgery ; Male ; Neurons ; Rats ; Rats, Sprague-Dawley ; Synapses ; ultrastructure

OBJECTIVETo observe the effect of Kangxin Capsule (KXC) on the expression of nerve growth factor (NGF) as well as the morphology and amount of nerve synapse in the cortical parietal lobe and hippocampus CA, area of vascular dementia ( VD) model rats.

METHODSThe model rats of VD made by photochemical reaction technique were randomly divided into five groups: the model group (MG), the high-dose, middle-dose and low-dose KXC groups (HDG, MDG and LDG), and the Western medicine hydergin control group (WMG). They were treated respectively with distilled water, high, middle and low dosage of KXC suspended liquid, and hydergin for a month. Besides, a blank group consisting of normal (non-model) rats was set up for control (CG). The ultrastructure of nerve synapse in the cortical parietal lobe and hippocampus CA1 area of the rats were observed and its density estimated. The condition of NGF positive neurons in the above-mentioned two regions were also observed by immunohistochemical stain.

RESULTSAll the KXC or hydergin treated groups demonstrated a normal amount of nerve synapse with integral structure in the cortical parietal lobe and hippocampus CA, area, which approached that in the CG and was superior to that in the MG. Also, the NGF positive neuron in all the treated groups was much more than that in MG with significant difference ( P<0.01), approaching to that in the CG.

CONCLUSIONKXC could elevate the expression of NGF in the cortical parietal lobe and hippocampus CA, area, preserve the number and morphology of synapse, thus to protect the function of nerve system from ischemic injury.

Animals ; Capsules ; Dementia, Vascular ; drug therapy ; metabolism ; pathology ; Disease Models, Animal ; Female ; Hippocampus ; chemistry ; Immunohistochemistry ; Male ; Medicine, Chinese Traditional ; Microscopy, Electron ; Nerve Growth Factors ; analysis ; Neurons ; ultrastructure ; Parietal Lobe ; chemistry ; Rats ; Rats, Wistar ; Synapses ; ultrastructure

Amino Acids ; metabolism ; Animals ; Dose-Response Relationship, Radiation ; Hippocampus ; metabolism ; radiation effects ; Male ; Microwaves ; adverse effects ; Neurons ; radiation effects ; ultrastructure ; Rats ; Rats, Wistar ; Synapses ; radiation effects ; ultrastructure

Synaptic ultrastructural changes after long-lasting long-term potentiation (L-LTP) induced by 2 and 100 Hz tetanus were investigated by electron microscopic and stereological approach in slices of the developing rat visual cortex (postnatal days 15~21). Both 2 and 100 Hz tetanus-induced L-LTP groups showed significant increases in synaptic interface curvature, synaptic numeric density and postsynaptic density thickness, as well as significant decreases in the cleft width, as compared with the control groups. In addition, the volume density of the active zone (AZ) was increased significantly in the 100 Hz tetanus-induced L-LTP group, but not in the 2 Hz group. The mean lateral area of individual AZ in the 100 Hz group was relatively higher than that in the 2 Hz group. These data suggest that newly formed synapses in the 100 Hz tetanus-induced L-LTP group are larger than those in the 2 Hz group and that 100 Hz tetanus might trigger reorganization or synthesis of postsynaptic cytoskeleton.
Animals ; Animals, Newborn ; Electric Stimulation ; methods ; Long-Term Potentiation ; physiology ; Male ; Rats ; Rats, Sprague-Dawley ; Synapses ; ultrastructure ; Synaptic Transmission ; physiology ; Visual Cortex ; physiology ; ultrastructure