S-Space College of Medicine/School of Medicine (의과대학/대학원) Dept. of Biomedical Sciences (대학원 의과학과) Theses (Master's Degree_의과학과)
Activity-dependent metaplasticity of direct cortical inputs in the rat hippocampal CA3 pyramidal neuron
백서 해마 CA3 영역 추체세포에서의 자극에 의한 신경가소성의 변조 현상에 대한 연구
- Kisang Eom
- 의과대학 의과학과
- Issue Date
- 서울대학교 대학원
- 학위논문 (석사)-- 서울대학교 대학원 : 의과학과, 2014. 2. 이석호.
- The intrinsic excitability of neurons plays an important role in the encoding of memory and in the coupling of synaptic inputs to spike generation. Recently, we report that repetitive somatic firing with physiologically relevant frequency induces internalization of Kv1.2 from distal dendrites of hippocampal CA3 pyramidal cells (CA3-PCs), resulting in long-term potentiation of intrinsic excitability (LTP-IE). We posed a question whether LTP-IE has any differential influences on the synaptic modulation at distal and intermediate dendritic intputs, which are carried by perforant path (PP) and associational/commissural (A/C) fiber, respectively.
I monitored the excitatory postsynaptic potentials (EPSPs) every 8 s at PP-CA3 synapses and AC-CA3 synapses before and after conditioning (a train of 20 somatic action potentials at 10 Hz) in CA3 PC. This conditioning induced a potentiation of EPSPs but not EPSCs at PP-CA3 synapses, whereas the same priming signal altered neither EPSCs nor EPSPs at AC-CA3 synapses.
To study the effect of LTP-IE on metaplsticity at PP-CA3 synapses, I first determined the threshold in the strength of PP stimulation for induction of long-term potentiation (LTP) at PP-CA3 synapses. I found that minimal stimulation of PP-CA3 synapses at high frequency (weak HFS) by itself was below the threshold of LTP induction. The weak HFS of PP induced neither EPSP-to-spike (E-S) potentiation nor LTP under control conditions. After the induction of LTP-IE, however, weak HFS readily induced E-S potentiation and LTP at the PP-CA3 synapses.
These results indicate that LTP-IE in the CA3-PCs enhances E-S coupling specifically at the PP synapses, which in turn facilitates memory formation at the same synapse under Hebbian rule.