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

BACKGROUND: Anterior thalamic nuclei (ATN) deep brain stimulation (DBS) is an effective method of controlling epilepsy, especially temporal lobe epilepsy. Mossy fiber sprouting (MFS) plays an indispensable role in the pathogenesis and progression of epilepsy, but the effect of ATN-DBS on MFS in the chronic stage of epilepsy and the potential underlying mechanisms are unknown. This study aimed to investigate the effect of ATN-DBS on MFS, as well as potential signaling pathways by a kainic acid (KA)-induced epileptic model. METHODS: Twenty-four rhesus monkeys were randomly assigned to control, epilepsy (EP), EP-sham-DBS, and EP-DBS groups. KA was injected to establish the chronic epileptic model. The left ATN was implanted with a DBS lead and stimulated for 8 weeks. Enzyme-linked immunosorbent assay, Western blotting, and immunofluorescence staining were used to evaluate MFS and levels of potential molecular mediators in the hippocampus. One-way analysis of variance, followed by the Tukey post hoc correction, was used to analyze the statistical significance of differences among multiple groups. RESULTS: ATN-DBS is found to significantly reduce seizure frequency in the chronic stage of epilepsy. The number of ectopic granule cells was reduced in monkeys that received ATN stimulation (P < 0.0001). Levels of 3',5'-cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in the hippocampus, together with Akt phosphorylation, were noticeably reduced in monkeys that received ATN stimulation (P = 0.0030 and P = 0.0001, respectively). ATN-DBS also significantly reduced MFS scores in the hippocampal dentate gyrus and CA3 sub-regions (all P < 0.0001). CONCLUSION ATN-DBS is shown to down-regulate the cAMP/PKA signaling pathway and Akt phosphorylation and to reduce the number of ectopic granule cells, which may be associated with the reduced MFS in chronic epilepsy. The study provides further insights into the mechanism by which ATN-DBS reduces epileptic seizures.
Adenosine Monophosphate ; Anterior Thalamic Nuclei ; Cyclic AMP-Dependent Protein Kinases ; Deep Brain Stimulation ; Epilepsy/therapy* ; Epilepsy, Temporal Lobe/therapy* ; Hippocampus ; Humans ; Mossy Fibers, Hippocampal ; Signal Transduction

Currently, compared to jaw-closing (JC) α-motoneurons, the information on the distribution and morphology of glutamatergic synapses on the jaw-closing (JC) γ-motoneurons, which may help elucidate the mechanism of isometric contraction of the JC muscle, is very limited. This study investigated the distribution and ultrastructural features of vesicular glutamate transporter 1 (VGLUT1)- and VGLUT2-immunopositive (+) axon terminals (boutons) on JC γ-motoneurons by retrograde tracing with horseradish peroxidase, electron microscopic immunocytochemistry, and quantitative analysis. About 35% of the boutons on identified JC γ-motoneurons were VGLUT+, and of those, 99% were VGLUT2+. The fraction of VGLUT1+ boutons of all boutons and the percentage of membrane of JC γ-motoneurons covered by these boutons were significantly lower than those for the JC α-motoneurons, revealed in our previous work. The bouton volume, mitochondrial volume, and active zone area of the VGLUT2+ boutons on the JC γ-motoneurons were uniformly small. These findings suggest that the JC γ-motoneurons, in contrast to the JC α-motoneurons, receive generally weak glutamatergic synaptic input almost exclusively from VGLUT2+ premotoneurons that form direct synapse with motoneurons.
Animals ; Horseradish Peroxidase ; Immunohistochemistry ; Isometric Contraction ; Membranes ; Microscopy, Electron ; Mitochondrial Size ; Motor Neurons ; Presynaptic Terminals ; Rats ; Synapses ; Vesicular Glutamate Transport Protein 1

µ-opioid receptor (MOR) is a class of opioid receptors with a high affinity for enkephalins and beta-endorphin. In hippocampus, activation of MOR is known to enhance the neuronal excitability of pyramidal neurons, which has been mainly attributed to a disinhibition of pyramidal neurons via activating Gαi subunit to suppress the presynaptic release of GABA in hippocampal interneurons. In contrast, the potential role of MOR in hippocampal astrocytes, the most abundant cell type in the brain, has remained unexplored. Here, we determine the cellular and subcellular distribution of MOR in different cell types of the hippocampus by utilizing MOR-mCherry mice and two different antibodies against MOR. Consistent with previous findings, we demonstrate that MOR expression in the CA1 pyramidal layer is co-localized with axon terminals from GABAergic inhibitory neurons but not with soma of pyramidal neurons. More importantly, we demonstrate that MOR is highly expressed in CA1 hippocampal astrocytes. The ultrastructural analysis further demonstrates that the astrocytic MOR is localized in soma and processes, but not in microdomains near synapses. Lastly, we demonstrate that astrocytes in ventral tegmental area and nucleus accumbens also express MOR. Our results provide the unprecedented evidence for the presence of MOR in astrocytes, implicating potential roles of astrocytic MOR in addictive behaviors.
Animals ; Antibodies ; Astrocytes* ; Behavior, Addictive ; beta-Endorphin ; Brain ; Carisoprodol ; Enkephalins ; gamma-Aminobutyric Acid ; Hippocampus ; Interneurons ; Mice ; Microscopy, Electron ; Neurons ; Nucleus Accumbens ; Presynaptic Terminals ; Pyramidal Cells ; Receptors, Opioid ; Synapses ; Ventral Tegmental Area

Parkinson disease (PD) is the second most prevalent neurodegenerative disorder after Alzheimer disease. The loss of specific brain area, the substantia nigra pars compacta is known as a major etiology, however it is not fully understood how this neurodegeneration is initiated and what precisely causes this disease. As one aspect of pathophysiology for PD, synaptic dysfunction (synaptopathy) is thought to be an earlier appearance for neurodegeneration. In addition, some of the familial factors cumulatively exhibit that these factors such as α-synuclein, leucine-rich repeat kinase 2, parkin, PTEN-induced kinase 1, and DJ-1 are involved in the regulation of synaptic function and missense mutants of familial factors found in PD-patient show dysregulation of synaptic functions. In this review, we have discussed the physiological function of these genetic factors in presynaptic terminal and how dysregulation of presynaptic function by genetic factors might be related to the pathogenesis of Parkinson disease.
Alzheimer Disease ; Brain ; Neurodegenerative Diseases ; Parkinson Disease* ; Pars Compacta ; Phosphotransferases ; Presynaptic Terminals ; Synapses ; Synaptic Transmission ; Synaptic Vesicles

Translationally controlled tumor protein (TCTP) is a cytosolic protein with microtubule stabilization and calcium-binding activities. TCTP is expressed in most organs including the nervous system. However, detailed distribution and functional significance of TCTP in the brain remain unexplored. In this study, we investigated the global and subcellular distributions of TCTP in the mouse brain. Immunohistochemical analyses with anti-TCTP revealed that TCTP was widely distributed in almost all regions of the brain including the cerebral cortex, thalamus, hypothalamus, hippocampus, and amygdala, wherein it was localized in axon tracts and axon terminals. In the hippocampus, TCTP was prominently localized to axon terminals of the perforant path in the dentate gyrus, the mossy fibers in the cornu ammonis (CA)3 region, and the Schaffer collaterals in the CA1 field, but not in cell bodies of granule cells and pyramidal neurons, and in their dendritic processes. Widespread distribution of TCTP in axon tracts and axon terminals throughout the brain suggests that TCTP is likely involved in neurotransmitter release and/or maintaining synaptic structures in the brain, and that it might have a role in maintaining synaptic functions and synaptic configurations important for normal cognitive, stress and emotional functions.
Amygdala ; Animals ; Axons* ; Brain ; Cell Body ; Cerebral Cortex ; Cognition ; Cytosol ; Dentate Gyrus ; Hippocampus ; Hypothalamus ; Immunohistochemistry ; Mice* ; Microtubules ; Nervous System ; Neurons* ; Neurotransmitter Agents ; Perforant Pathway ; Presynaptic Terminals* ; Pyramidal Cells ; Thalamus

OBJECTIVETo explore the effects of embryonic lead exposure on motor function and balance ability in offspring rats and the possible mechanisms.

METHODSAn animal model of embryonic lead exposure was prepared with the use of pregnant Sprague-Dawley rats freely drinking 0.1% (low-dose group, LG) or 0.2% (high-dose group, HG) lead acetate solution. A normal control group (NG) was also set. The male offspring rats of these pregnant rats were included in the study, consisting of 12 rats in the NG group, 10 rats in the LG group, and 9 rats in the HG group. The offspring rats' motor function and balance ability were evaluated using body turning test and coat hanger test. Eight rats were randomly selected from each group, and immunohistochemistry and Timm's staining were employed to measure the expression of c-Fos and mossy fiber sprouting (MFS) in the hippocampus.

RESULTSThe HG group had a significantly longer body turning time than the NG and LG groups (P<0.05), and the LG group had a significantly longer body turning time than the NG group (P<0.05). The HG group had a significantly lower score of balance ability than the NG and LG groups (P<0.05), and the LG group had a significantly lower score of balance ability than the NG group (P<0.05). The area percentage of c-Fos-positive neurons in the hippocampal CA1 region was significantly higher in the HG group than in the other two groups (P<0.05), and it was significantly higher in the LG group than in the NG group (P<0.05). The semi-quantitative scores of MFS in the hippocampal CA3 region and dentate gyrus were significantly higher in the HG group than in the other two groups (P<0.05), and they were significantly higher in the LG group than in the NG group (P<0.05).

CONCLUSIONSEmbryonic lead exposure could impair the offspring rats' motor function and balance ability. These changes may be related to increased c-Fos expression in the hippocampal CA3 region and abnormal MFS in the hippocampal CA3 region and dentate gyrus.

Animals ; Female ; Fetus ; drug effects ; Hippocampus ; chemistry ; drug effects ; Lead ; toxicity ; Male ; Mossy Fibers, Hippocampal ; drug effects ; Motor Activity ; drug effects ; Postural Balance ; drug effects ; Pregnancy ; Proto-Oncogene Proteins c-fos ; analysis ; Rats ; Rats, Sprague-Dawley

The vertebrate neuromuscular junction (NMJ) is considered as a “tripartite synapse” consisting of a motor axon terminal, a muscle endplate, and terminal Schwann cells that envelope the motor axon terminal. The neuregulin 1 (NRG1)-ErbB2 signaling pathway plays an important role in the development of the NMJ. We previously showed that Grb2-associated binder 1 (Gab1), a scaffolding mediator of receptor tyrosine kinase signaling, is required for NRG1-induced peripheral nerve myelination. Here, we determined the role of Gab1 in the development of the NMJ using muscle-specific conditional Gab1 knockout mice. The mutant mice showed delayed postnatal maturation of the NMJ. Furthermore, the selective loss of the gab1 gene in terminal Schwann cells produced delayed synaptic elimination with abnormal morphology of the motor endplate, suggesting that Gab1 in both muscles and terminal Schwann cells is required for proper NMJ development. Gab1 in terminal Schwann cells appeared to regulate the number and process elongation of terminal Schwann cells during synaptic elimination. However, Gab2 knockout mice did not show any defects in the development of the NMJ. Considering the role of Gab1 in postnatal peripheral nerve myelination, our findings suggest that Gab1 is a pleiotropic and important component of NRG1 signals during postnatal development of the peripheral neuromuscular system.
Animals ; Mice ; Mice, Knockout ; Motor Endplate ; Muscle, Skeletal* ; Muscles ; Myelin Sheath ; Neuregulin-1 ; Neuromuscular Junction ; Peripheral Nerves ; Presynaptic Terminals ; Protein-Tyrosine Kinases ; Schwann Cells* ; Synapses* ; Vertebrates

OBJECTIVETo investigate the effect of licorice flavonoid (LF) on kainic acid (KA)-induced seizure in mice and its mechanism.

METHODSMale adult ICR mice were injected with 25 mg/kg KA to induce temporal lobe seizure. LF was administrated 7 d before seizure induction (pre-treatment) or 24 h after seizure induction (post-treatment) for 7 d. Acute seizure latency, seizure stage and duration were observed and compared between LF- and vehicle-treated mice. From d2 on, mice with status epilepticus were video-monitored for spontaneous seizures, 10 h/d for 6 w. Immunohistochemical analysis of BrdU and Timm staining was conducted to detect the neurogenesis and mossy fiber sprouting, respectively.

RESULTSNo significant difference was observed in acute seizure latency, seizure stage and duration between LF-and vehicle-treated mice. KA-induced acute seizure resulted in spontaneous seizure in mice, and the seizure frequency was increased with time. Pre- and post-treatment with LF decreased seizure frequency from w3 after modeling [(0.58±0.15)/d, (0.38±0.38)/d vs (1.23±0.23)/d, P <0.05]. Furthermore, KA-induced seizure resulted in robust neurogenesis and mossy fiber sprouting, while treatment with LF both pre- and post- KA injection significantly inhibited neurogenesis (15.6±2.6, 17.1±3.1 vs 28.9±3.5, P <0.05) and mossy fiber sprouting (1.33±0.31, 1.56±0.42 vs 3.0±0.37, P <0.05).

CONCLUSIONLF has no significant anti-seizure effect. However, it can decrease epileptogenesis through inhibition of neurogenesis and mossy fiber sprouting.

Animals ; Disease Models, Animal ; Flavonoids ; pharmacology ; Glycyrrhiza ; chemistry ; Kainic Acid ; adverse effects ; Male ; Mice ; Mice, Inbred ICR ; Mossy Fibers, Hippocampal ; drug effects ; Neurogenesis ; drug effects ; Seizures ; chemically induced ; drug therapy ; Status Epilepticus ; drug therapy

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