Kolta A, Larson J, Lynch G
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717, USA.
Neuroscience. 1995 May;66(2):277-89. doi: 10.1016/0306-4522(94)00565-m.
Recent studies indicate that long-term potentiation is accompanied by changes in the waveform of field excitatory postsynaptic potentials in the CA1 field of disinhibited hippocampal slices, suggesting that long-term potentiation alters the kinetics of the glutamate receptor channels that mediate excitatory synaptic responses. The present study examined the effects of stimulating and recording location within stratum radiatum on the magnitude of long-term potentiation and the associated waveform changes. Stimulation of stratum radiatum proximal to the cell body layer evoked field excitatory postsynaptic potentials in proximal stratum radiatum that had decay phases well-fit by single exponentials; long-term potentiation reduced the decay time constant of these potentials, as reported previously. Stimulation of distal stratum radiatum evoked field excitatory postsynaptic potentials in distal stratum radiatum that were contaminated by positive after-potentials; meaningful estimates of decay time constants for these responses could not be obtained. Long-term potentiation of distal responses tended to be smaller than that obtained proximally. Comparisons were also made between responses recorded distally and proximally for either distal or proximal stimulation. For both stimulation loci, the distally-recorded responses had positive after-potentials and the proximally-recorded responses did not. The decay time constants for proximally-recorded responses to distal stimulation decreased significantly after long-term potentiation. Proximal and distal stimulation both produced greater long-term potentiation recorded proximally than distally and the difference was significantly greater for proximal stimulation. When long-term potentiation was induced by stimulation of proximal and distal sites simultaneously, the difference between proximally- and distally-recorded long-term potentiation was significantly reduced. Paired-pulse facilitation was greater when recorded proximally but the variation in facilitation with stimulation and recording position was different from that obtained for long-term potentiation. Paired-pulse facilitation of response amplitude was slightly reduced after long-term potentiation, but the change did not depend on the stimulation-recording arrangement; facilitation of response slope was not reliably affected by long-term potentiation. These results indicate that the shape of the dendritic field excitatory postsynaptic potential is influenced by the relative position of recording electrodes in stratum radiatum; when the position is such that after-potentials are minimized, long-term potentiation produces a decrease in the decay time constant of the synaptic field potential.(ABSTRACT TRUNCATED AT 400 WORDS)
近期研究表明，在去抑制海马切片的CA1区，长时程增强伴随着场兴奋性突触后电位波形的变化，这表明长时程增强改变了介导兴奋性突触反应的谷氨酸受体通道的动力学。本研究考察了放射层内刺激和记录位置对长时程增强幅度及相关波形变化的影响。刺激靠近细胞体层的放射层会在近端放射层诱发场兴奋性突触后电位，其衰减相能很好地用单指数函数拟合；如先前报道，长时程增强降低了这些电位的衰减时间常数。刺激远端放射层会在远端放射层诱发被正后电位污染的场兴奋性突触后电位；无法获得这些反应衰减时间常数的有意义估计值。远端反应的长时程增强往往比近端获得的要小。还对远端或近端刺激时远端和近端记录的反应进行了比较。对于两个刺激位点，远端记录的反应都有正后电位，而近端记录的反应没有。长时程增强后，近端记录的对远端刺激反应的衰减时间常数显著降低。近端和远端刺激在近端记录时都比在远端记录时产生更大的长时程增强，且近端刺激时这种差异显著更大。当通过同时刺激近端和远端位点诱导长时程增强时，近端和远端记录的长时程增强之间的差异显著减小。近端记录时双脉冲易化作用更大，但易化作用随刺激和记录位置的变化与长时程增强的情况不同。长时程增强后反应幅度的双脉冲易化作用略有降低，但这种变化不依赖于刺激 - 记录安排；长时程增强对反应斜率的易化作用没有可靠影响。这些结果表明，树突场兴奋性突触后电位的形状受放射层中记录电极相对位置的影响；当位置使后电位最小化时，长时程增强会使突触场电位的衰减时间常数减小。（摘要截取自400字）
