Komatsu Y
Department of Physiology, Kyoto Prefectural University of Medicine, Japan.
J Neurosci. 1994 Nov;14(11 Pt 1):6488-99. doi: 10.1523/JNEUROSCI.14-11-06488.1994.
Long-term potentiation (LTP) of inhibitory synaptic transmission in rat visual cortex was investigated using intracellular recording in slice preparations. The inhibitory postsynaptic potential (IPSP) of layer V cells evoked monosynaptically by layer IV stimulation was recorded while excitatory postsynaptic potentials (EPSPs) were blocked by adding NMDA and non-NMDA receptor antagonists to the perfusate. Separate presynaptic fiber groups were activated by two stimulating electrodes placed in layer IV. One electrode was used to test the effect of conditioning stimulation; the other served as a control. Trains of high-frequency stimulation (50 Hz, 1 sec) were applied at an interval of 10 sec as a conditioning stimulation. The LTP of IPSP induced by the conditioning stimulation had properties similar to those known for LTP of EPSP in hippocampal CA1: (1) it was specific to the conditioned pathway; (2) repetitive application of the conditioning stimulation saturated the LTP; (3) LTP was induced by conditioning stimulation at intensities higher than a threshold; (4) weak conditioning stimulation to one pathway, which alone failed to induce LTP, induced associative LTP when strong conditioning stimulation was simultaneously applied to the other pathway; (5) weak conditioning stimulation sometimes induced short-term potentiation. In contrast to these similarities, LTP of IPSP was induced by a wider range of stimulus frequencies than that capable of generating LTP of EPSPs in CA1. It was induced not only by a brief high-frequency stimulation but also by an intermediate-frequency (2 Hz) stimulation continued for 5 min. In addition, the LTP induction was not dependent on postsynaptic membrane potential. Finally, the LTP of IPSP was more easily induced in developing than in mature rats. This age dependence suggests that LTP of IPSPs may contribute to the improvement of response selectivity of visual cortical cells through visual experience during postnatal development.
采用脑片膜片钳细胞内记录技术，研究大鼠视皮层抑制性突触传递的长时程增强（LTP）。在灌流液中加入N-甲基-D-天冬氨酸（NMDA）和非NMDA受体拮抗剂以阻断兴奋性突触后电位（EPSP），同时记录由第IV层刺激单突触诱发的第V层细胞的抑制性突触后电位（IPSP）。两个刺激电极置于第IV层，分别激活不同的突触前纤维群。一个电极用于测试条件刺激的效应，另一个作为对照。以10秒的间隔施加高频刺激（50Hz，1秒）的串刺激作为条件刺激。条件刺激诱导的IPSP的LTP具有与海马CA1区EPSP的LTP相似的特性：（1）它对条件化通路具有特异性；（2）重复施加条件刺激使LTP达到饱和；（3）LTP由高于阈值强度的条件刺激诱导产生；（4）对一条通路的弱条件刺激单独不能诱导LTP，但当同时对另一条通路施加强条件刺激时可诱导联合LTP；（5）弱条件刺激有时可诱导短时程增强。与这些相似性相反，IPSP的LTP比在CA1区能够产生EPSP的LTP的刺激频率范围更广。它不仅可由短暂的高频刺激诱导产生，也可由持续5分钟的中频（2Hz）刺激诱导产生。此外，LTP的诱导不依赖于突触后膜电位。最后，与成年大鼠相比，发育中的大鼠更容易诱导IPSP的LTP。这种年龄依赖性表明，IPSP的LTP可能在出生后发育过程中通过视觉经验有助于改善视皮层细胞的反应选择性。
