Nishikawa Y, Shibata S, Watanabe S
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Brain Res. 1995 Oct 16;695(2):158-62. doi: 10.1016/0006-8993(95)00717-5.
Optic nerve stimulation caused a postsynaptic field potential in the rat suprachiasmatic nucleus (SCN) of hypothalamic slices. In the present experiment, we demonstrated whether tetanic stimulation of optic nerve can produce a long-term potentiation (LTP) in the SCN postsynaptic field potential. The amplitude of SCN field potential was higher in the subjective day animals than that in the subjective night animals. Tetanic stimulation of optic nerve (100 Hz, 1 s) at subjective daytime (projected zeitgeber time: ZT 0-8) produced a LTP in this field potential, although the onset of LTP was slow. When tetanic stimulation was applied at ZT4, the percent increase of amplitude was 116.6% immediately after, 159.8% 30 min after and 215.4% 120 min after tetanic stimulation, whereas tetanic stimulation of optic nerve at subjective night-time caused a weak LTP in the SCN. Although tetanic stimulation of Schaffer collaterals induced a LTP formation in the CA1 region of rat hippocampal slices, there were no obvious circadian changes in this LTP formation. The present results demonstrated that excitatory influence on the SCN caused a synaptic plasticity such as LTP. Although the physiological meaning of this LTP is uncertain at present, LTP may be related to adaptation mechanism to photic stimulation.
视神经刺激可在下丘脑切片的大鼠视交叉上核（SCN）中引起突触后场电位。在本实验中，我们证明了对视神经的强直刺激是否能在SCN突触后场电位中产生长时程增强（LTP）。主观日动物的SCN场电位幅度高于主观夜动物。在主观白天（投射的时间geber时间：ZT 0 - 8）对视神经进行强直刺激（100 Hz，1 s）可在该场电位中产生LTP，尽管LTP的起始较慢。当在ZT4施加强直刺激时，强直刺激后立即、30分钟后和120分钟后幅度增加的百分比分别为116.6%、159.8%和215.4%，而在主观夜间对视神经进行强直刺激在SCN中引起的LTP较弱。尽管对Schaffer侧支的强直刺激可在大鼠海马切片的CA1区诱导LTP形成，但这种LTP形成没有明显的昼夜变化。目前的结果表明，对SCN的兴奋性影响可引起如LTP这样的突触可塑性。尽管目前这种LTP的生理意义尚不确定，但LTP可能与对光刺激的适应机制有关。
