碩士 / 中國醫藥大學 / 醫學研究所 / 92 / The purpose of this study to investigate the effect of somatic q-burst stimulation on expression of early phase long-term potentiation ( LTP ) induced by 1 train of tetanus stimulation comprising 100 pulses at 100 Hz, at CA1 synapses in rat hippocampus, and the underlying cellular mechanisms.
Standard electrophysiological technique for field-potential recording in hippocampal slices was employed. A glass recording electrode ( filled with 3M NaCl, 3-5 MW ) was positioned in stratum rediatum, and two bipolar stainless stimulating electrodes were positioned in stratum radiatum for stimulation of Schaffer collateral branch fibers ( S1 ) and in alveus for eliciting of antidromic spike of pyramidal cells ( S2 ).
We first confirmed that, while single train of tetanus stimulation ( TS ) at 100 Hz ( 100 pulses ) delivering via S1 only induced early phase LTP that started decaying to baseline level 60 minutes after high frequency stimulation ( E-LTP = 125.2 ± 5.40 % ,n=10, p < 0.05, paired t-test ) , 5 and 9 trains of TS at 100 Hz induced late phase LTP that could last for at least 270 minutes ( respectively, 126.3 ± 9.44 %, n=8, p < 0.05；151.9 ± 17.45 %, n=8, p < 0.05, paired t-test ). Early phase-LTP induced by single train of TS via S1 was consolidated to late phase-LTP if somatic spiking was antidromically elicited 20 mins after TS using theta-burst stimulation ( TBS ) paradigm delivered through S2. L-LTP was also induced by single train of TS via S1 when somatic spiking elicited using TBS via S2 was given 60 mins after TS. Only E-LTP was induced if interval between TBS-TS was increased to 120 mins. Similar results were obtained when the temporal order of TS and TBS was reversed.
Application D,L-APV ( 50 μM ), an NMDA receptor antagonist, has no effect on the consolidation of early phase-LTP to late phase-LTP by somatic θ-burst stimulation, suggesting a NMDA receptors independent mechanism is involved. The effect of somatic TBS was blocked upon bath application of Nimodipine, the antagonist of L-type voltage-gated calcium channels ( VGCC ), and blocker of protein kinase C ( PKC ) pathway, suggesting influx of calcium into cytoplasm via VGCC during somatic TBS which in turn activate PKC are crucial factors for consolidation of early phase LTP induced by single strain of TS into late phase LTP.
Taken together, the results of this study provide information on temporal profile of signal molecules generated in soma by somatic spiking which trigger further synthesis of new signal molecules and consolidate E-LTP at tagged synapses to L-LTP. The above process require influx of calcium into soma of pyramidal cells via L-type VGCC, and activation of PKC.
| Identifer | oai:union.ndltd.org:TW/092CMCH0534017 |
| Date | January 2004 |
| Creators | 鄭信忠 |
| Contributors | , 閔 明 源, 楊 琇 雯 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 88 |
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