G proteins mediate signal transductions generated by neurotransmitters and hormones. Among G proteins, Go is found in a large quantity in brain, but its precise role in the nervous tissue is not fully understood. In addition, Go is one of the major proteins in growth cone membranes, which implies an important role of Go in the regulation of axon outgrowth. In this study, we attempted to determine the role of Go in axon outgrowth. We overexpressed the a subunit of Go (ao) in F11 neuroblatoma cells and examined the effect of ao on the neurite outgrowth. In F11 cells, dibutyryl cAMP increased neurite outgrowth remarkably upto 0.1 mM in a concentration dependent manner, but in a less degree at higher concentration. In the presence of 0.5 mM dibutyryl cAMP, the differentiation of F11 cells was almost saturated and the cells exhibited a typical neuronal morphology. Overexpression of ao caused a reduction of neurite outgrowth by 77.4% in length while increasing the number of neurites by 2.2 fold. The average neurite length was 38.9+/-12.5 mm in the ao-overexpressing F11 cells but 172.3+/-25.9 mm in the untransfected cells The total number of nurites per cell was 5.6+/-0.4 in the ao-overexpressing cells but 2.5 0.2 in the untransfected cells. This result suggests that Go may play an important role in growth cone collapse during neuronal cell differentiation.
Axons ; Brain ; Cell Differentiation ; Growth Cones ; GTP-Binding Proteins ; Membranes ; Neurites* ; Neurons ; Neurotransmitter Agents ; Signal Transduction

Injured primary sensory axons fail to regenerate into the spinal cord, leading to chronic pain and permanent sensory loss. Re-entry is prevented at the dorsal root entry zone (DREZ), the CNS-PNS interface. Why axons stop or turn around at the DREZ has generally been attributed to growth-repellent molecules associated with astrocytes and oligodendrocytes/myelin. The available evidence challenges the contention that these inhibitory molecules are the critical determinant of regeneration failure. Recent imaging studies that directly monitored axons arriving at the DREZ in living animals raise the intriguing possibility that axons stop primarily because they are stabilized by forming presynaptic terminals on non-neuronal cells that are neither astrocytes nor oligodendrocytes. These observations revitalized the idea raised many years ago but virtually forgotten, that axons stop by forming synapses at the DREZ.
Animals ; Astrocytes ; Axons ; Chronic Pain ; Oligodendroglia ; Presynaptic Terminals ; Regeneration ; Spinal Cord ; Spinal Nerve Roots ; Synapses

The presence of the zinc ion pump antibody ZnT-3 in zinc enriched (ZEN) cerebellar axonal terminals was detected in immunohistochemical sections of mouse cerebellum. All the ZnT-3-immunoreactive structures appeared punctate in the cerebellar cortex, while the white matter including intrinsic nuclei were void. The staining intensity varied in the different phylogenetic divisions of cerebellum. Archicortex was stained most intensively while paleo and in particular neocortex was stained only faintly. The ZnT-3 fraction was detected mainly in the upper half of the granule cell layer (GCL), although where they appeared ultrastructurally in small folded varicosities located corresponding to axon terminals of the Golgi cells. In the molecular layer (ML), the ZnT-3 staining was found to be distributed diffusely but in perpendicular radiating pattern through the layer but with the most intense staining in the upper half of the layer. Ultrastructurally the coarse patches of staining found in the granule cell layers were corresponded to presynaptic axon terminals contacting with granule cells. No ZnT-3 staining was observed in the Purkinje cell layer. The present results suggest that the Golgi cells in the mouse cerebellum are one of the ZEN neurons in the mammalian brain. In conclusion, we first showed putative ZEN terminals in the mouse cerebellum. These results will provide a valuable aid for investigation of further localization of the ZEN neurons in the mammalian cerebellum. More work is needed to further characterize the ZEN terminals, and so autometallographical studies are currently being investigated in this laboratory.
Animals ; Axons ; Brain ; Cerebellar Cortex ; Cerebellum* ; Ion Pumps ; Mice* ; Neocortex ; Neurons ; Presynaptic Terminals ; Zinc*

An attempt has been made to discriminate synaptic diversity in the neostriatum of the cat with emphasis on the characteristic structures of axon terminals and postsynaptic profiles. The differentiation of the axon terminals was based on the size and shape of synaptic vesicles in the axoplasm. Three types of axon terminals could be differentiated: Type I, the terminals contained small round (45 nm in diameter) vesicles; type II, the terminals with large pleomorphic (50 nm) vesicles; and type III, the terminals contained flattened (45 x 25 nm) vesicles. The type I terminals were making asymmetrical or symmetrical synapses in contact with the somata, dendrites and dendritic spines of neurons in the neostriatum, and a few type I terminals making asymmetrical or symmetrical contact with axons were also observed. The type II and III terminals were making symmetrical contact with the somata and dendrites of neostriatal neurons. A few type II terminals formed at the node of Ranvier of myelinated nerve fibers were making symmetrical contact with large dendrites. Additionally, dendro-dendritic and serial syanpses were rarely found in the neostriatum. In the serial synapses composed of axo-dendritic and dendro-dendritic synapses, the type I terminals making asymmetrical contact and the type II making symmetrical contact were identified.
Animals ; Axons ; Cats* ; Dendrites ; Dendritic Spines ; Neostriatum* ; Nerve Fibers, Myelinated ; Neurons ; Presynaptic Terminals ; Synapses ; Synaptic Vesicles

Recent studies have revealed that mossy fiber(MF) axons of dentate granule cells undergo synaptic reorganization in both electrical kindling models of temporal lobe epilepsy (TLE) and human TLE. This synaptic reorganization has been demonstrated by Timm histochemistry which selectively labels synaptic terminals of MF because of unusually high zinc content. Of MF. In electrical kindling model and human TLE Timm granules were distributed throughout the supragranular layer of dentate gyrus where they are not normally present. These supragranular Timm granules are regarded as MF synaptic reorganization. Kindling model of generalized epilepsy can be made by repeated intraperitoneal injections of subconvulsive dosage of pentylenetetrazol (PTZ). The present study is designed to test the hypothesis that MF synaptic reorganization might be developed in PTZ kindling model In this study, the supragranular Timm granules by Timm histochemistry were scored and depth EEG was recorded in dentate gyrus of various stages of PTZ kindling rats. The scores of supragranular Timm granules were 0. 33+0.17 in stage I seizure (n=9) ; 0. 38 + 0. 14 in stage II seizure (n=13) ; 0. 44 + 0. 18 in stage III seizure (n=9) ; 1. 40+0.16 in 3 consecutive or total 5-7 stage TV or V seizure (n=10) ; 1. 86+ 0.26 in 7-10 consecutive or total 10-15 stage IV or V seizure (n=7) ; 2.50+0.22 in 1215 consecutive or total 20-30 stage IV or V seizure (n=6) ; and 0. 30+0.15 in salinen controls (n=lo). Statistical analysis showed the supragranular Timm scorwere significantly higher in stage IV or V seizure than in control and in stage 1, I or, I seizure (p<0.05 ), and tended to increase with increasing numbers of stage IV or V seizure. Depth EEG recording from dentate gyrus showed 6-9Hz rhythmic waves in saline injected control, single or polyspikes or normal waves during stage I seizure, 4-6Hz slow waves or spike-waves complexes lasting 1-2 seconds during stage II seizure, 4-6Hz slow waves or spike-waves complexes lasting 3-6 seconds during stage III seizure, 8-15Hz spikes lasting over 10 seconds during stage IV seizure and 10-30HZ spikes lastmg over 20 seconds durmg stage V seizure The results demonstrate the development of MF synaptic reorganization and a sound correlation between MF synaptic reorganization and the progression of the kindlmg phenomenon in PTZ kindling models. These findings suggest that MF synaptic reorganization might be a critical event underlying the development and . Maintenance of kindling phenomenon and epileptic state.
Animals ; Axons ; Dentate Gyrus* ; Electroencephalography ; Epilepsy, Generalized ; Epilepsy, Temporal Lobe ; Humans ; Injections, Intraperitoneal ; Pentylenetetrazole* ; Presynaptic Terminals ; Rats* ; Seizures ; Zinc

Neurotransmission begins with neurotransmitter being released from synaptic vesicles. To achieve this function, synaptic vesicles endure the dynamic "release-recycle" process to maintain the function and structure of presynaptic terminal. Synaptic transmission starts with a single action potential that depolarizes axonal bouton, followed by an increase in the cytosolic calcium concentration that triggers the synaptic vesicle membrane fusion with presynaptic membrane to release neurotransmitter; then the vesicle membrane can be endocytosed for reusing afterwards. This process requires delicate regulation, intermediate steps and dynamic balances. Accumulating evidence showed that the release ability and mobility of synapses varies under different stimulations. Synaptic vesicle heterogeneity has been studied at molecular and cellular levels, hopefully leading to the identification of the relationships between structure and function and understanding how vesicle regulation affects synaptic transmission and plasticity. People are beginning to realize that different types of synapses show diverse presynaptic activities. The steady advances of technology studying synaptic vesicle recycling promote people's understanding of this field. In this review, we discuss the following three aspects of the research progresses on synaptic vesicle recycling: 1) presynaptic vesicle pools and recycling; 2) research progresses on the differences of glutamatergic and GABAergic presynaptic vesicle recycling mechanism and 3) comparison of the technologies used in studying presyanptic vesicle recycling and the latest progress in the technology development in this field.
Action Potentials ; Axons ; physiology ; Calcium ; physiology ; Endocytosis ; Humans ; Presynaptic Terminals ; physiology ; Synapses ; physiology ; Synaptic Transmission ; Synaptic Vesicles ; physiology

The ultrastructure of the excitotoxic lesion similar to that occurring in the degenerative neuronal disease was produceby stereotaxic injections of 1 nmol and 10 mnol of kainic acid nto the corpus striatum of adult rat brain There were rnarked swellings in the neuronal dendrites at injected sites. Neurotubules and neurofilarnents were disrupted as and amorphous materials and scattered throughout the interior of distended dendrites. Internal cristae and membranes of mitochondria were destroyed with the loss of integrity of intracellular organelles. Disruption of cellular and nuclear membranes occurered in severe cases. But there was no apparent pathologic change in the other structure, ie, synapses, presynaptic and postsynaptic parts, axons and glial cells. The synapses between dendrites and axon terminals were not destroyed despite of marked distension of dendrites. The local administration of excitatory amino acid into the brain caused the destruction of dendrites and neuronal cell bodies, but axons and axon terminals were intact With the lapse of time, axons and axon terminals from the destroyed neuron degenerate Therelore stereotaxic injection of excitatory amino acid into the brain may provldes a method of investigating neuronal connectivity.
Adult ; Animals ; Axons* ; Brain ; Corpus Striatum* ; Dendrites ; Excitatory Amino Acids ; Humans ; Kainic Acid* ; Membranes ; Mitochondria ; Neuroglia ; Neurons* ; Nuclear Envelope ; Organelles ; Presynaptic Terminals ; Rats ; Synapses

Some retinal neurons, including intrinsically photosensitive retinal ganglion cells have their dendrites stratified in sublamina a of the inner plexiform (IPL), the OFF sublayer, but paradoxically show light-driven ON electrophysiological responses. In order to understand the mechanism on this paradoxical response, by using immunoelectron microscopy with a specific antibody against calbindin, we examined the synaptic connections of the calbindin-immunoreactive ON cone bipolar cell of the rabbit retina, which is thought to make the ribbon synapse in sublamina a of the IPL. The ribbon synapses in sublamina a by calbindin-immunoreactive ON cone bipolar cells were mainly found at the border between the inner nuclear layer and the IPL. Interestingly, the output targets at these ribbon synapses turned out as monads, and multiple synaptic ribbons were engaged in each synapse. These findings were different from those at the conventional ribbon synapse formed by calbindin-immunoreactive ON cone bipolar axon terminals. Thus, these findings may be the characteristics of the calbindin-immunoreactive ON cone bipolar ribbon synapse in sublamina a and can be used to classify the synapse in the retinal circuit research.
Axons ; Calcium-Binding Protein, Vitamin D-Dependent ; Dendrites ; Microscopy, Electron ; Microscopy, Immunoelectron ; Presynaptic Terminals ; Retina ; Retinal Ganglion Cells ; Retinal Neurons ; Retinaldehyde ; Synapses

It has been previously reported that parvalbumin expression was downregulated in AII amacrine cells, while upregulated in a subset of cone bipolar cells electrically synapse with AII amacrine cell in the streptozotocin-induced diabetic rat retina. In the present study, we aimed to trace biochemical changes of pre-synaptic neurons to AII amacrine cells in rat retina following diabetic injury. Diabetic condition was induced by streptozotocin injection into Sprague-Dawley rats aged of 8 weeks. The experimental term of induced diabetes was set at 1, 4, 12 and 24 weeks. Changes of pre-synaptic neurons were evaluated by immunohistochemistry and Western blot analysis with anti-protein kinase C (PKC)-alpha and anti-tyrosine hydroxylase (TH) antibodies. Rod bipolar cells immunolocalized with PKC-alpha antibody extended their enlarged axon terminals into stratum 5 of the inner plexiform layer. In later diabetes, the axon was shorten and its terminals of rod bipolar cell are slightly enlarged. The protein levels of PKC-alpha were slightly increased along with the duration of diabetes. TH immunoreactive neurons are morphologically classified into two subtypes of amacrine cells in the inner nuclear layer: one (type 1) has large soma with long and primary dendrites, classified with dopaminergic, and the other (type 2) has small soma with dendritic arborization. In the outermost inner plexiform layer, ring-like structures being composed of type 1 cell processes were densely distributed. In diabetic retina, the intensity of TH immunoreactivity in type 1 neurons was reduced. In accordance with morphological changes, the protein levels of TH were reduced during diabetes. These results demonstrate that TH immunoreactive dopaminergic amacrine cells are more susceptible to diabetic injury than the rod bipolar cells in the rat retina and may suggest that downregulation of parvalbumin expression in AII amacrine cells of diabetic retina is mainly due to dysfunction of pre-synaptic dopaminergic amacrine cells.
Amacrine Cells* ; Animals ; Antibodies ; Axons ; Blotting, Western ; Carisoprodol ; Dendrites ; Down-Regulation ; Immunohistochemistry ; Neurons* ; Phosphotransferases ; Presynaptic Terminals ; Rats* ; Rats, Sprague-Dawley ; Retina* ; Streptozocin ; Synapses

The purpose of this study was to investigate the distribution of neuropeptide Y (NPY) in the cat spinal trigeminal subnucleus caudalis following pulpectomy of mandibular premolars and molar by means of an immunohistochemical and immunoelectron microscopic study. The animals were divided into normal and experimental group which were sacrificed at 14 days after pulpectomy. The results were as follows; 1. On the light microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-immunoreactivity (IR) was weak within lamina I and lamina II outer. In pulpectomy group, NPY-IR was strong and appeared to extend into lamina I and lamina II inner at 14 days. 2. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-IR was revealed in axon terminals, dendrites, myelinated axons and unmyelinated axons. NPY-IR was associated with membrane structures within microtubules, synaptic vesicles, outer membrane of mitochondria and inner surface of the axolemma. In NPY-immunoreactive structure, there was a small amount of DAB precipita-tions. 3. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis at 14 days in pulpectomy group, the number of NPY-immunoreactive axon terminals, dendrites, myelinated axons and unmyelinated axons was increased than normal group. DAB precipitations in NPY-immunoreactive structure was increased than normal group. Some NPY-immunoreactive axon terminal formed synaptic glomerulus and axoaxonic synapse. 4. The results indicate that NPY-IR was increased in the spinal trigeminal subnucleus caudalis after pulpectomy, and it is speculated that the increased NPY by injury of peripheral nerve may participate in the processing of nociception.
Animals ; Axons ; Bicuspid ; Cats* ; Dendrites ; Immunohistochemistry ; Membranes ; Microtubules ; Mitochondria ; Molar ; Myelin Sheath ; Neuropeptide Y* ; Neuropeptides* ; Nociception ; Peripheral Nerves ; Presynaptic Terminals ; Pulpectomy* ; Synapses ; Synaptic Vesicles