OBJECTIVE: To explore the influence of electroacupuncture (EA) on the expression of AMPA receptor subunit GluR1 in the rats with acute spinal cord injury (SCI) and explore the potential effect mechanism of EA in treatment of acute SCI. METHODS: A total of 80 SD rats were randomly divided into five groups, i.e. a sham-operation group, a model group, an AMPA antagonist (DNQX) group, an EA group and a DNQX+EA group, 16 rats in each group. The modified Allen's impacting method was adopted to prepare the rat model of acute SCI at T RESULTS: Compared to the sham-operation group in 6 h, 24 h and 48 h after modeling, the BBB scores were all significantly decreased in the model group ( CONCLUSION The intervention with EA at "Dazhui" and "Mingmen" promotes the repair of the injured nerve in the spinal anterior horn probably through inhibiting GluR1 expression in the spinal injured area in the rats with acute SCI.
Animals ; Electroacupuncture ; Rats ; Rats, Sprague-Dawley ; Receptors, AMPA/genetics* ; Spinal Cord ; Spinal Cord Injuries/therapy*

OBJECTIVETo investigate the developmental profiles on surface expression and co-localization of NMDA receptor clusters and AMPA receptor clusters on dendrite in cultured hippocampal neurons of rats.

METHODSGreen fluorescent protein tagged GluR2 subunit (GFP-GluR2) and FLAG tagged NR2B subunit (FLAG-NR2B) were transfected into cultured hippocampal neurons at 5 days in vitro (DIV5). FLAG-NR2B containing NMDA receptor clusters and GFP-GluR2 containing AMPA receptor clusters expressed on membrane surface were then labeled in living neurons using anti FLAG mAb/Cy3-conjugated anti-mouse antibody and anti-GFP pAb/Alex488-conjugated anti-rabbit antibody.

RESULTThe numbers of receptor cluster per 100 microm dendrite in the neurons at DIV7 and DIV19 were 39.7+/-5.0 and 64.7+/-6.1 (P<0.01) for NR2B-NMDAR, 59.1+/-3.3 and 99.7+/-6.4 (P<0.01) for GluR2-AMPAR, and 29.9+/-4.5 and 37.5+/-2.5(P<0.05) for the co-localized, respectively. At DIV7 and DIV19, 75.4% and 57.9% NR2B-NMDAR clusters were co-localized with GluR2-AMPAR; and 50.6% and 37.6% GluR2-AMPAR clusters were co-localized with NR2B-NMDAR, respectively.

CONCLUSIONThe density of NR2B-NMDAR containing and GluR2-AMPAR containing receptor clusters increases during development of hippocampal neurons in culture. Although the co-localized clusters are increased as well in an unit length of dendrite, the extent to which the two receptor clusters are co-localized decreases. These data imply a possible change in the partnership of AMPA receptor subtype and NMDA receptor subtype at newly formed synapses during development.

Animals ; Cells, Cultured ; Dendrites ; chemistry ; Hippocampus ; chemistry ; Rats ; Rats, Sprague-Dawley ; Receptors, AMPA ; analysis ; Receptors, N-Methyl-D-Aspartate ; analysis

receptors. The specific AMPA receptor antagonist GYKI-52466(50 microM) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. Perfusion of the opioid orphan receptor(ORL1) agonist nociceptin(3 microM) reduced the freque ncy of sEPSCs and miniature EPSCs(mEPSCs). The effects of nociceptin were blocked by the selective ORL1 receptor antagonist (Nphe')nociceptin(1-13)NH2(3 microM) and were not affected by the non-specific opioid receptor antagonist naloxone(10 microM). To investigate the specificity of this synaptic inhibition, we selectively activated the nociceptive C fibers with capsaicin, which induced a strong increase in the frequency of sEPSCs. In the presence of nociceptin, the response to capsaicin was diminished. In conclusion, these results suggest that nociceptin inhibits excitatory synaptic transmission in the MDH by acting on presynaptic ORL1 receptors.]]>
Animals ; Brain Stem ; Capsaicin ; Child ; Child, Orphaned ; Humans ; Nerve Fibers, Unmyelinated ; Neurons ; Perfusion ; Rats ; Receptors, AMPA ; Receptors, N-Methyl-D-Aspartate ; Receptors, Opioid ; Sensitivity and Specificity ; Synaptic Transmission

receptors on excitatory synaptic transmission. In the presence of strychnine (1 microM) and bicuculline (20 microM), spontaneous inward currents at -70 mV were observed. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI 52466 (50 microM) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. Group I, II metabotropic glutamate receptor (mGluR) agonist ACPD (20 microM) significantly decreased the average sEPSCs frequency. No significant effect on sEPSCs amplitude was observed. Frequency of miniature excitatory postsynaptic currents (mEPSCs) was significantly decreased by 20 microM ACPD, but amplitude of mEPSCs was not changed. The specific mGluR 2, 3 agonist DCG-IV (3 microM) reduced mEPSCs frequency, but did not change mEPSCs amplitude. There were no significant changes in the average sEPSCs frequency and amplitude. The mGluR 1, 5 agonist DHPG (100 microM) decreased sEPSCs and mEPSCs frequency, but had no effects on sEPSCs and mEPSCs amplitude. These data suggest that the activation of metabotropic glutamate receptors, via its presynaptic inhibition, can influence the excitatory synaptic transmission of MDH neurons.]]>
Animals ; Bicuculline ; Brain Stem ; Excitatory Postsynaptic Potentials ; Horns ; Neurons ; Rats ; Receptors, AMPA ; Receptors, Metabotropic Glutamate ; Receptors, N-Methyl-D-Aspartate ; Strychnine ; Synaptic Transmission ; Trigeminal Nucleus, Spinal

Serotonin [5-hydroxytryptamine (5-HT)] regulates synaptic plasticity in the visual cortex. Although the effects of 5-HT on plasticity showed huge diversity depending on the ages of animals and species, it has been unclear how 5-HT can show such diverse effects. In the rat visual cortex, 5-HT suppressed long-term potentiation (LTP) at 5 weeks but enhanced LTP at 8 weeks. We speculated that this difference may originate from differential regulation of neurotransmission by 5-HT between the age groups. Thus, we investigated the effects of 5-HT on apha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-, gamma-aminobutyric acid receptor type A (GABA(A)R)-, and N-methyl-D-aspartic acid receptor (NMDAR)-mediated neurotransmissions and their involvement in the differential regulation of plasticity between 5 and 8 weeks. AMPAR-mediated currents were not affected by 5-HT at both 5 and 8 weeks. GABA(A)R-mediated currents were enhanced by 5-HT at both age groups. However, 5-HT enhanced NMDAR-mediated currents only at 8 weeks. The enhancement of NMDAR-mediated currents appeared to be mediated by the enhanced function of GluN2B subunit-containing NMDAR. The enhanced GABA(A)R- and NMDAR-mediated neurotransmissions were responsible for the suppression of LTP at 5 weeks and the facilitation of LTP at 8 weeks, respectively. These results indicate that the effects of 5-HT on neurotransmission change with development, and the changes may underlie the differential regulation of synaptic plasticity between different age groups. Thus, the developmental changes in 5-HT function should be carefully considered while investigating the 5-HT-mediated metaplastic control of the cortical network.
Animals ; Critical Period (Psychology)* ; Humans ; Long-Term Potentiation* ; N-Methylaspartate* ; Plastics ; Rats* ; Receptors, AMPA ; Receptors, GABA ; Receptors, GABA-A ; Serotonin ; Synaptic Transmission ; Visual Cortex*

Conventional views of synaptic transmission generally overlook the possibility of "postfusional- control" the regulation of the speed or completeness of transmitter release upon vesicular fusion. However, such regulation often occurs in non-neuronal cells where the dynamics of fusion-pore opening is critical for the speed of transmitter release. In case of synapses, the slower the transmitter release, the smaller the size and rate-of-rise of postsynaptic responses would be expected if postsynaptic neurotransmitter receptors were not saturated. This prediction was tested at hippocampal synapses where postsynaptic AMPA-type glutamate receptors (AMPAR) were not generally saturated. Here, we found that the small miniature excitatory postsynaptic currents (mEPSCs) showed significantly slower rise times than the large mEPSCs when the sucrose-induced mEPSCs recorded in cyclothiazide (CTZ), a blocker for AMPAR desensitization, were sorted by size. The slow rise time of the small mEPSCs might result from slow release through a non-expanding fusion pore, consistent with postfusional control of neurotransmitter release at central synapses.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid* ; Excitatory Postsynaptic Potentials ; Neurotransmitter Agents ; Receptors, AMPA* ; Receptors, Glutamate ; Receptors, Neurotransmitter ; Synapses* ; Synaptic Transmission

In the present study, we investigated the role of peripheral ionotropic receptors in artemin-induced thermal hyperalgesia in the orofacial area. Male Sprague-Dawley rats weighting 230 to 280 g were used in the study. Under anesthesia, a polyethylene tube was implanted in the subcutaneous area of the vibrissa pad, which enabled drug-injection. After subcutaneous injection of artemin, changes in air-puff thresholds and head withdrawal latency time were evaluated. Subcutaneous injection of artemin (0.5 or 1 µg) produced significant thermal hyperalgesia in a dose-dependent manner. However, subcutaneous injection of artemin showed no effect on air-puff thresholds. IRTX (4 µg), a TRPV1 receptor antagonist, D-AP5 (40 or 80 µg), an NMDA receptor antagonist, or NBQX (20 or 40 µg), an AMPA receptor antagonist, was injected subcutaneously 10 min prior to the artemin injection. Pretreatment with IRTX and D-AP5 significantly inhibited the artemin-induced thermal hyperalgesia. In contrast, pretreatment with both doses of NBQX showed no effect on artemin-induced thermal hyperalgesia. Moreover, pretreatment with H-89, a PKA inhibitor, and chelerythrine, a PKC inhibitor, decreased the artemin-induced thermal hyperalgesia. These results suggested that artemin-induced thermal hyperalgesia is mediated by the sensitized peripheral TRPV1 and NMDA receptor via activation of protein kinases.
Anesthesia ; Animals ; Head ; Humans ; Hyperalgesia* ; Injections, Subcutaneous ; Male ; N-Methylaspartate ; Polyethylene ; Protein Kinases ; Rats* ; Rats, Sprague-Dawley ; Receptors, AMPA

Extracellular recordings of field excitatory postsynaptic potential (fEPSP) is one of the most common ways for studies of synaptic plasticity, such as long-term potentiation (LTP) and paired-pulse plasticity (PPP). The measurement of the changes in the different components of fEPSP waveform, such as the initial slope, initial area, peak amplitude and whole area, were commonly used as criteria for the judgement of potentiation or depression of synaptic plasticity. However, the differences in the conclusions drawn from measuring different components of fEPSP waveform at the same recording have still been largely ignored. Here we compared high-frequency stimulation (HFS)-evoked synaptic plasticity, both LTP and PPP, by measuring different components of fEPSP waveform, including the initial slope, initial area, peak amplitude, whole area and time course. The results not only indicated the acceleration of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor kinetics underlies LTP in hippocampal CA1 region of mice, but also showed that different measurements of fEPSP waveform at the same recording result in different magnitudes of LTP and different forms of PPP in hippocampal CA1 region of mice. After HFS, the paired-pulse ratio was slightly decreased by measurement of the initial area, but obviously increased by measurement of the initial slope of the pair fEPSPs. These results might draw apparently contradictory conclusions. Therefore, careful and complete analysis of the data from different parts of fEPSP waveforms is important for reflection of the faithful changes in synaptic plasticity.
Animals ; CA1 Region, Hippocampal ; physiology ; Excitatory Postsynaptic Potentials ; Long-Term Potentiation ; Mice ; Neuronal Plasticity ; Receptors, AMPA ; metabolism

To explore novel antifatigue agents targeting with AMPA receptor, 10 compounds were synthesized and their structures were confirmed by 1H NMR, ESI-MS and elemental analysis. 1-BCP was treated as the leading compound. The antifatigue activities were evaluated by weight-loaded forced swimming test, and the AMPA receptor binding affinities were tested with radioligand receptor binding assays. The results unveiled that 5b appeared to possess potent antifatigue activities and high affinity with AMPA receptor, which deserved further studies.
Animals ; Benzamides ; chemistry ; pharmacology ; Dioxoles ; chemistry ; pharmacology ; Fatigue ; prevention & control ; Piperidines ; chemistry ; pharmacology ; Radioligand Assay ; Receptors, AMPA ; metabolism ; Swimming

In the present research, patch-clamp whole-cell recording was used to study the developmental changes of the internal horizontal synaptic plasticity in layer II/III of rats' primary visual cortices. Pairing stimulation was used to induce long term potentiation (LTP) of neurons in layer II/III from layer II/III and layer IV. The data indicate that: (1) Responses of layer II/III neurons can be evoked independently at II/III-II/III and IV-II/III synapses by horizontal and vertical stimulations; (2) LTP can be induced from neurons in the layer II/III by horizontal tetanic stimulation at II/III-II/III synapses till postnatal day12 (P12, before eyes open); (3) Meanwhile, only short term potentiation (STP) at IV-II/III synapses can be induced by horizontal tetanic stimulation before eyes open; (4) After P12, a robust LTP at IV-II/III synapses can be induced by horizontal tetanic stimulation; (5) At P14, when vertical and horizontal tetanic stimulations were given to the same neuron, the LTP at IV-II/III synapses was weaker than that induced by vertical stimulation alone, suggesting that vertical synaptic modification was negatively regulated by horizontal inputs when two-direction synaptic inputs were presented at the same time; (6) Spontaneous responses of AMPA receptors (AMPARs) in the layer II/III neuron of rats' primary visual cortices are regulated by the development. The frequency of AMPARs-mediated postsynaptic currents was at a low level before eyes open, increased sharply at P12-P14, and slightly decreased after P18. And the amplitude of spontaneous AMPARs currents slowly decreased after P12. The results demonstrated that both the strength of horizontal synaptic modification and the effects of horizontal inputs on the vertical synaptic connection are regulated by the development. II/III-II/III synaptic communication has dual effects on the IV-II/III synapses, which may be involved in a competitive machinery of neural circuitry maturation and the formation of visual function columns.
Animals ; Long-Term Potentiation ; Neuronal Plasticity ; Neurons ; physiology ; Patch-Clamp Techniques ; Rats ; Receptors, AMPA ; physiology ; Synapses ; physiology ; Visual Cortex ; physiology