Castro-Alamancos M A, Connors B W
Department of Neuroscience, Brown University, Providence, RI 02912, USA.
Proc Natl Acad Sci U S A. 1996 Feb 6;93(3):1335-9. doi: 10.1073/pnas.93.3.1335.
Repetitive stimuli reliably induce long-term potentiation (LTP) of synapses in the upper layers of the granular somatosensory cortex but not the agranular motor cortex of rats. Herein we examine, in these same cortical areas, short-term changes in synaptic strength that occur during the LTP induction period. theta-Burst stimulation produced a strong short-term enhancement of synapses in the granular area but only weak enhancement in the agranular area. The magnitude of enhancement during stimulation was strongly correlated with the magnitude of LTP subsequently expressed. Short-term enhancement was abolished by an antagonist of N-methyl-D-aspartate (NMDA) receptors but remained in the presence of a non-NMDA receptor antagonist. Inhibitory postsynaptic potentials of the granular and agranular areas displayed similar frequency sensitivity, but the frequency sensitivity of NMDA receptor-dependent excitatory postsynaptic potentials differed significantly between areas. We propose that pathway-specific differences in short-term enhancement are due to variations in the frequency dependence of NMDA currents; different capacities for short-term enhancement may explain why repetitive stimulation more readily induces LTP in the somatosensory cortex than in the motor cortex.
重复性刺激能可靠地诱导大鼠颗粒状躯体感觉皮层上层突触的长期增强（LTP），但不能诱导无颗粒运动皮层突触的长期增强。在此，我们研究了在相同的皮层区域中，LTP诱导期内突触强度的短期变化。θ波爆发刺激在颗粒状区域产生了强烈的突触短期增强，但在无颗粒区域仅产生了微弱的增强。刺激期间增强的幅度与随后表达的LTP幅度密切相关。N-甲基-D-天冬氨酸（NMDA）受体拮抗剂可消除短期增强，但在非NMDA受体拮抗剂存在的情况下仍存在。颗粒状和无颗粒区域的抑制性突触后电位表现出相似的频率敏感性，但NMDA受体依赖性兴奋性突触后电位的频率敏感性在不同区域之间存在显著差异。我们认为，短期增强的通路特异性差异是由于NMDA电流频率依赖性的变化；不同的短期增强能力可能解释了为什么重复性刺激在躯体感觉皮层比在运动皮层更容易诱导LTP。
