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N-methyl-D-aspartate receptors (NMDARs) containing different GluN2 subunits play distinct roles in synaptic plasticity. Such differences may not only be determined by the channel properties, but also by differential surface distribution and synaptic localization.In the present study, using a Cy3-conjugated Fab fragment of the GFP antibody to label surface-located GluN2 subunits tagged with GFP at the N-terminus,we observed the membrane distribution patterns of GluN2A- or GluN2B-containing NMDARs in cultured rat hippocampal neurons. We found that surface NMDARs containing GluN2A, but not those containing GluN2B,were inclined to cluster at DIV7. Swapping the carboxyl termini of the GluN2 subunits completely reversed these distribution patterns. In addition, surface NMDARs containing GluN2A were preferentially associated with PSD-95. Taken together, the results of our study suggest that the clustering distribution of GluN2A containing NMDARs is determined by the GluN2AC-terminus, and its interaction with PSD-95 plays animportant role in this process.

The neuropeptide cholecystokinin octapeptide (CCK) is involved in a variety of brain functions. In the hippocampus, most CCK is released from CCK-positive (CCK+) neurons, but the effects of CCK on CCK+ neurons are poorly understood. We employed primary hippocampal cultures to explore the modulatory effect of CCK on CCK+ neurons. CCK-8S (0.2 μM) was added to the culture medium from day in vitro 2 (DIV-2) to DIV-11. An adenovirus integrated with the CCK promoter was used to label CCK+ neurons. Whole-cell patch clamp recording was carried on to record the electrophysiology properties. The results show that: (1) CCK-8S significantly decreased membrane capacity but increased the membrane resistance (Rm) of CCK+ neurons, (2) CCK-8S increased action potential (AP) firing frequency of CCK+ neurons but did not affect the firing pattern, (3) CCK-8S facilitated CCK+ neuron excitatory synaptic transmission but attenuated inhibitory synaptic transmission, and (4) the expression of postsynaptic density-95 (PSD-95) in cultured hippocampal neurons was elevated by CCK-8S treatment. Our results demonstrate that CCK-8S significantly alters the membrane electrophysiological characteristics and synaptic activity of cultured hippocampal CCK+ neurons. These findings may enhance our understanding of the modulatory effect of CCK in the brain., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Cholecystokinin (CCK), a neuropeptide, is widely distributed in the brain. The function of CCK is involved in many brain functions including learning and memory, but the cellular mechanism is poorly understood. In the present study, we investigated the effect of CCK on dendritic filopodia and spines of cultured hippocampal neurons from wild-type and APP/PS1 mice. The cultured hippocampal neurons were infected with CMV-GFP (CMV promoter with green fluorescent protein) adenovirus 24h before image acquisition to display the subtle structure of dendrites. Cholecystokinin octapeptide sulfated (CCK-8S, 0.2μM) was added into the cultured solution from divided in vitro day 2 (DIV 2). A decrease of filopodia and spines density was observed in APP/PS1 mice compared with that of wild type mice. CCK-8S increased the density of filopodia and spines at DIV 7, DIV 14 and DIV 21 in hippocampal neurons of both wild-type and APP/PS1 mice. In addition, this effect was inhibited by CI988, an antagonist of CCK-2 receptor. Those results indicate that CCK-8S can influence the dendritic development and spine genesis of cultured hippocampal neurons derived from both wild-type and APP/PS1 mice. These data suggest that CCK may play an important role in learning and memory., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

In central nervous system only a limited number of vesicles exist in the presynaptic terminals. The size and fusion modes of the vesicles were particularly important because of their potential impact on neuronal communications. Efficient methods were needed to analyze the recycling kinetics of synaptic vesicle and the size of readily releasable pool (RRP). In this study, fluorescent dyes with different affinity for membranes (FM1-43 with high affinity and FM2-10 with low affinity) were used to stain the functional synaptic vesicles of cultured hippocampal neurons and the kinetics of vesicle recycling was measured. The results showed that the destaining proportion was larger for FM2-10 than that for FM1-43 during the first trial, while it was greater for FM1-43 than FM2-10 during the second and third trials (first round, 93.0%+/-5.9% versus 57.9%+/-3.5% for FM2-10 and FM1-43, respectively, P<0.0001; second round, 1.4%+/-3.8% versus 24.0%+/-2.3%, P<0.0001; third round, 2.3%+/-1.6% versus 8.6%+/-1.5%, P=0.005). The results indicated that rapid endocytosis existed not only in the first round but also occurred when the vesicles were reused. Moreover, Both high-frequency stimuli and hypertonic sucrose stimuli were used to estimate the RRP sizes in the mix cultured hippocampal inhibitory neurons at 13-14 days in vitro (DIV). We found that the RRP size estimated by hypertonic sucrose stimuli [(200+/-23.0) pC] was much larger than that estimated by high-frequency stimuli [(51.1+/-10.5) pC]. One possible reason for the discrepancies in RRP estimates is that in mix cultured conditions, one neuron may receive inputs from several neurons and hypertonic sucrose stimuli will cause RRP of all those neurons release, while using dual patch recording, only the connection between two neurons was analyzed. Thus, to exclude out the impacts of inputs numbers on RRP sizes, it is more reasonable to use high-frequency stimuli to estimate the RRP size in mix cultured neurons.

Aim: To evaluate the effects of global system for mobile communications (GSM) 1800 MHz microwaves on dendritic filopodia, dendritic arborization, and spine maturation during development in cultured hippocampal neurons in rats., Methods: The cultured hippocampal neurons were exposed to GSM 1800 MHz microwaves with 2.4 and 0.8 W/kg, respectively, for 15 min each day from 6 days in vitro (DIV6) to DIV14. The subtle structures of dendrites were displayed by transfection with farnesylated enhanced green fluorescent protein (F-GFP) and GFP-actin on DIV5 into the hippocampal neurons., Results: There was a significant decrease in the density and mobility of dendritic filopodia at DIV8 and in the density of mature spines at DIV14 in the neurons exposed to GSM 1800 MHz microwaves with 2.4 W/kg. In addition, the average length of dendrites per neuron at DIV10 and DIV14 was decreased, while the dendritic arborization was unaltered in these neurons. However, there were no significant changes found in the neurons exposed to the GSM 1800 MHz microwaves with 0.8 W/kg., Conclusion: These data indicate that the chronic exposure to 2.4 W/kg GSM 1800 MHz microwaves during the early developmental stage may affect dendritic development and the formation of excitatory synapses of hippocampal neurons in culture.

Objective: To measure mobility of dendritic filopodia, complexity of dendritic arborization using method of live imaging in cultured rat hippocampal neurons and to analyze their morphological characters quantitatively., Methods: Vectors expressing Green Fluorescent Protein- Fibrous Actin (GFP-F-Actin) and F-GFP were co-transfected into cultured rat hippocampal neurons at 5 d in vitro (DIV 5). Neurons expressing GFP were photographed and analyzed with Metamorph software., Result: Dendritic filopodia was observed to move actively from DIV 7 to DIV 9. The mean density of filopodia was (10.78 +/-3.78)/100 microm, (10.68 +/-2.96)/100 microm and (9.99 +/-3.67)/100 microm (P >0.05), and there were (30.18 +/-14.03)% to (87.36 +/-20.88)% filopodia were mobile (P <0.001). During DIV 7-DIV 14, the total length of dendritic branches grew from (410.74 +/-185.98) microm to (1238.21 +/-418.32)microm (P <0.001) and the number of dendritic branches increased from 18.93 +/-7.23 to 33.60 +/-10.46 (P<0.001). The density of spine was (37.17 +/-6.46)/100 microm at DIV 14., Conclusion: The combination of live imaging with quantitative analysis is a useful method to study dendritic morphological development in vitro, including indicators of dendritic filopodia, dendritic arborization and spines.