The back-propagating action potential (bpAP) is crucial for neuronal signal integration and synaptic plasticity in dendritic trees. Its properties (velocity and amplitude) can be affected by dendritic morphology. Due to limited spatial resolution, it has been difficult to explore the specific propagation process of bpAPs along dendrites and examine the influence of dendritic morphology, such as the dendrite diameter and branching pattern, using patch-clamp recording. By taking advantage of Optopatch, an all-optical electrophysiological method, we made detailed recordings of the real-time propagation of bpAPs in dendritic trees. We found that the velocity of bpAPs was not uniform in a single dendrite, and the bpAP velocity differed among distinct dendrites of the same neuron. The velocity of a bpAP was positively correlated with the diameter of the dendrite on which it propagated. In addition, when bpAPs passed through a dendritic branch point, their velocity decreased significantly. Similar to velocity, the amplitude of bpAPs was also positively correlated with dendritic diameter, and the attenuation patterns of bpAPs differed among different dendrites. Simulation results from neuron models with different dendritic morphology corresponded well with the experimental results. These findings indicate that the dendritic diameter and branching pattern significantly influence the properties of bpAPs. The diversity among the bpAPs recorded in different neurons was mainly due to differences in dendritic morphology. These results may inspire the construction of neuronal models to predict the propagation of bpAPs in dendrites with enormous variation in morphology, to further illuminate the role of bpAPs in neuronal communication.
Action Potentials/physiology* ; Dendrites/physiology* ; Neurons/physiology* ; Neuronal Plasticity ; Pyramidal Cells/physiology*

Temporal lobe epilepsy (TLE) is a common and severe neurological disorder which is often intractable. It can not only damage the normal structure and function of hippocampus, but also affect the neurogenesis in dentate gyrus (DG). It is well documented from researches on the animal models of TLE that after a latent period of several days, prolonged seizure activity leads to a dramatic increase in mitotic activity in the hippocampal DG. However, cell proliferation returns to baseline levels within 3-4 weeks after status epilepticus (SE). Meanwhile, there are two major abnormalities of DG neurogenesis, including the formation of hilar basal dendrites and the ectopic migration of newborn granule cells into the polymorphic cell layer, which may affect epileptogenesis and seizure onset. However, the specific contribution of these abnormalities to seizures is still unknown. In other words, whether they are anti-epileptic or pro-epileptic is still under heated discussion. This article systematically reviews current knowledge on neurogenesis and epilepsy based on the results of studies in recent years and discusses the possible roles of neurogenesis in epileptogenesis and pathologic mechanisms, so as to provide information for the potential application of neurogenesis as a new clinical therapeutic target for temporal lobe epilepsy.
Animals ; Brain ; Cell Movement ; physiology ; Cell Proliferation ; physiology ; Dendrites ; pathology ; Dentate Gyrus ; growth & development ; pathology ; Epilepsy, Temporal Lobe ; etiology ; pathology ; physiopathology ; Hippocampus ; growth & development ; pathology ; Humans ; Mitosis ; physiology ; Neurogenesis ; physiology ; Neurons ; pathology ; Seizures ; etiology ; physiopathology ; Status Epilepticus ; physiopathology

MicroRNAs (miRNAs) are critical for both development and function of the central nervous system. Significant evidence suggests that abnormal expression of miRNAs is associated with neurodevelopmental disorders. MeCP2 protein is an epigenetic regulator repressing or activating gene transcription by binding to methylated DNA. Both loss-of-function and gain-of-function mutations in the MECP2 gene lead to neurodevelopmental disorders such as Rett syndrome, autism and MECP2 duplication syndrome. In this study, we demonstrate that miR-130a inhibits neurite outgrowth and reduces dendritic spine density as well as dendritic complexity. Bioinformatics analyses, cell cultures and biochemical experiments indicate that miR-130a targets MECP2 and down-regulates MeCP2 protein expression. Furthermore, expression of the wild-type MeCP2, but not a loss-of-function mutant, rescues the miR-130a-induced phenotype. Our study uncovers the MECP2 gene as a previous unknown target for miR-130a, supporting that miR-130a may play a role in neurodevelopment by regulating MeCP2. Together with data from other groups, our work suggests that a feedback regulatory mechanism involving both miR-130a and MeCP2 may serve to ensure their appropriate expression and function in neural development.
Animals ; Dendrites ; genetics ; metabolism ; Dendritic Spines ; genetics ; metabolism ; Down-Regulation ; physiology ; Methyl-CpG-Binding Protein 2 ; biosynthesis ; genetics ; MicroRNAs ; genetics ; metabolism ; Rats

The cAMP-responsive element binding protein (CREB)-regulated transcription coactivator, CRTC (also known as transducer of regulated CREB, TORC), is identified as a potent modulator of cAMP response element (CRE)-driven gene transcription. The CRTC family consists of three members (CRTC1-3), among which the CRTC1 shows the highest expression in the brain. Several studies have demonstrated that the CRTC1 plays critical roles in neuronal dendritic growth, long-term synaptic plasticity, memory consolidation and reconsolidation etc., whereas dysfunction of CRTC1 is mainly involved in neurodegenerative disorders. In light of these findings, we aim to review recent research reports that indicate the CRTC1 dysfunction and its underlying mechanisms in the neurodegenerative disorders.
Brain ; physiology ; Dendrites ; physiology ; Humans ; Neurodegenerative Diseases ; physiopathology ; Neuronal Plasticity ; Transcription Factors ; physiology

The electrical excitability of the dendrites of the cortical neurons was first studied on the apical dendrites of the pyramidal neurons. Professor ZHANG Xiang-Tong (H-T Chang) made important contributions in the fifties of last century on this topic. Through numerous studies later on, it has been established that the electrical excitability of dendrites of different types of neurons, even different dendrites in the same neuron is different. For the apical dendrites of the cortical pyramidal neurons, neither a single nor a train of repetitive action potentials with constant frequency can reach its terminal portion. However, some of the burst repetitive responses with non-constant frequency of the apical dendrite elicited by direct current injected into the soma may reach the terminal portion. This may be due to: (1) the calcium ion concentration in the apical dendrite is increased by the burst activities, which, in turn, increases the electrical excitability of the apical dendrite and /or (2) some retrograde collaterals of axon of the activated soma reach the apical dendrite and release neurotransmitter glutamate, which changes the properties of the voltage-gated ion channels in the apical dendrite. Low electrical excitability of the apical dendrites seems to be essential for the processing of numerous income signals to the terminal portion of the apical dendrites.
Action Potentials ; Animals ; Dendrites ; physiology ; Electrophysiological Phenomena ; Ion Channels ; physiology ; Pyramidal Cells ; physiology ; Synaptic Transmission

Sixty years elapsed since Chang (Hsiang-Tung Chang, Xiang-Tong Zhang) presented his seminal report "Cortical neurons with particular reference to the apical dendrite" at the Cold Spring Harbor Symposium. Thanks to the development of elaborated techniques through the 6 decades, our understanding of the dendrite has been pushed forward greatly: the backward and forward conductions during excitation, sodium and calcium conductances, chemical excitation by uncaging glutamate at a dimension of micrometer, and the quantitative study of chemical organization of postsynaptic density (PSD), etc. Though the progression is great, there are still tough problems in dendritic research, especially the integration through dendritic spine.
Calcium Signaling ; Dendrites ; physiology ; Glutamic Acid ; metabolism

BACKGROUNDWallerian degeneration is a self-destructive process of axonal degeneration that occurs after an axonal injury or during neurodegenerative disorders such as Parkinson's or Alzheimer's disease. Recent studies have found that the activity of the nicotinamide adenine dinucleotide (NAD) synthase enzyme, nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) can affect the rate of Wallerian degeneration in mice and drosophila. NMNAT1 protects neurons and axons from degeneration. However, the role of NMNAT1 in neurons of central nervous system is still not well understood.

METHODSWe set up the culture of primary mouse neurons in vitro and manipulated the expression level of NMNAT1 by RNA interference and gene overexpression methods. Using electroporation transfection we can up-regulate or down-regulate NMNAT1 in cultured mouse dendrites and axons and study the neuronal morphogenesis by immunocytochemistry. In all functional assays, FK-866 (CAS 658084-64-1), a highly specific non-competitive inhibitor of nicotinamide phosphoribosyltransferase was used as a pharmacological and positive control.

RESULTSOur results showed that knocking down NMNAT1 by RNA interference led to a marked decrease in dendrite outgrowth and branching and a significant decrease in axon growth and branching in developing cortical neurons in vitro.

CONCLUSIONSThese findings reveal a novel role for NMNAT1 in the morphogenesis of developing cortical neurons, which indicate that the loss of function of NMNAT1 may contribute to different neurodegenerative disorders in central nervous system.

Animals ; Axons ; metabolism ; Blotting, Western ; Cells, Cultured ; Dendrites ; metabolism ; Immunohistochemistry ; Mice ; Morphogenesis ; genetics ; physiology ; Neurons ; cytology ; metabolism ; Nicotinamide-Nucleotide Adenylyltransferase ; genetics ; metabolism

Dendrites ; physiology ; History, 20th Century ; Neurophysiology ; history

Activity-dependent dendritic translation in CNS neurons is important for the synapse-specific provision of proteins that may be necessary for strengthening of synaptic connections. A major rate-limiting factor during protein synthesis is the availability of eukaryotic translation initiation factor 4E (eIF4E), an mRNA 5'-cap-binding protein. In this study we show by fluorescence in situ hybridization (FISH) that the mRNA for eIF4E is present in the dendrites of cultured rat hippocampal neurons. Under basal culture conditions, 58.7 +/- 11.6% of the eIF4E mRNA clusters localize with or immediately adjacent to PSD-95 clusters. Neuronal activation with KCl (60 mM, 10 min) very significantly increases the number of eIF4E mRNA clusters in dendrites by 50.1 and 74.5% at 2 and 6 h after treatment, respectively. In addition, the proportion of eIF4E mRNA clusters that localize with PSD-95 increases to 74.4 +/- 7.7% and 77.8 +/- 7.6% of the eIF4E clusters at 2 and 6 h after KCl treatment, respectively. Our results demonstrate the presence of eIF4E mRNA in dendrites and an activity-dependent increase of these clusters at synaptic sites. This provides a potential mechanism by which protein translation at synapses may be enhanced in response to synaptic stimulation.
Animals ; Cells, Cultured ; Dendrites/*metabolism ; Eukaryotic Initiation Factor-4E/genetics/*metabolism ; Hippocampus/*cytology ; Immunohistochemistry ; In Situ Hybridization, Fluorescence ; Microscopy, Confocal ; Neurons/cytology/*physiology ; Potassium Chloride/pharmacology ; Protein Biosynthesis ; RNA, Messenger/genetics/*metabolism ; Rats ; Rats, Sprague-Dawley ; Synapses ; *Up-Regulation

OBJECTIVETo investigate the effects of mobile phone 1800 MHz electromagnetic fields (EMF) on the surface markers and the functions of human dendritic cells (DC).

METHODSHuman DCs were exposed to intermittent 5 min on/10 min off EMF with specific absorption rates (SAR) 4 W/kg for 0 h, 1 h, 12 h or 24 h, respectively. FACS analysis was used to detect the positive percentage of DC surface markers including HLA-DR and co-stimulatory molecules such as CD80, CD86, CD40 and CD11c. CCK-8 kit was adopted to examine the function of allo-mixed lymphocyte reaction (allo-MLR) of DC, and enzyme linked immunosorbent assay (ELISA) to identify the levels of IL-12p70 and TNF-alpha secreted by DC.

RESULTCompared with the sham radiation group, after exposure to the electromagnetic fields for 1 h, 12 h, or 24 h, HLA-DR, CD80,CD86 and CD40 were all declined except CD11c. The ability of DC allo-MLR in each exposure group was decreased significantly (P<0.05), especially in the 24 h exposure group. However, the secreted levels of IL-12p70 and TNF-alpha of DC in each exposure group remained no changed.

CONCLUSIONThe study showed that EMF exposure could down-regulate the surface molecules and stimulation ability of human DC.

B7-1 Antigen ; B7-2 Antigen ; immunology ; Biomarkers ; analysis ; CD11c Antigen ; immunology ; Cell Phone ; Cells, Cultured ; Dendrites ; pathology ; Dendritic Cells ; metabolism ; physiology ; radiation effects ; Electromagnetic Fields ; HLA-DR Antigens ; analysis ; Humans ; Interleukin-12 ; immunology