Stripling Jeffrey S, Galupo M Paz
Department of Psychology, 216 Memorial Hall, University of Arkansas, Fayetteville, AR 72701, USA.
Brain Res. 2008 Dec 30;1246:70-9. doi: 10.1016/j.brainres.2008.10.003. Epub 2008 Oct 17.
The present study examined in detail the development and decay of potentiation induced in vivo by repeated high-frequency stimulation of cortical association fibers (AF) in piriform cortex (PC). Male Long-Evans rats with chronically-implanted stimulating and recording electrodes were administered potentiating AF stimulation (thirty 10-pulse 100-Hz trains) on 8 consecutive days, followed by a ninth administration after an 8-day layoff. The time course of potentiation was monitored by local field potentials evoked in the PC and olfactory bulb (OB) by 0.1 Hz single-pulse AF test stimulation before, during, and following each potentiating treatment. AF test stimulation evoked two distinct components in the PC, an early component (EC) and a late component (LC). High-frequency AF stimulation produced potentiation of each component, but with very different characteristics. EC potentiation consisted of a brief augmentation during each bout of potentiating stimulation that persisted <2 min after the last high-frequency train and showed no cumulative effects following repeated induction across days. In contrast, LC potentiation developed gradually, requiring several daily potentiation treatments to reach maximum amplitude, and decayed more slowly each time it was induced. Furthermore, LC potentiation persisted in latent form for at least 8 days following its apparent decay and could be reinstated by repeated test stimulation that was without effect at the beginning of the experiment. Potentiation in the OB resembled LC potentiation in its characteristics, but with less latent potentiation. These results indicate that the potentiation reported here is distinctly different from the long-term potentiation previously demonstrated in vitro in the PC, and suggest that this potentiation represents an increase in excitability within the cortical association fiber system that can be stored in latent form and retrieved at a later time. These characteristics make this potentiation a suitable candidate for participation in long-term functional changes within olfactory cortex.
本研究详细考察了梨状皮层（PC）中反复高频刺激皮层联合纤维（AF）在体内诱导的增强作用的发展和衰退。对长期植入刺激和记录电极的雄性Long-Evans大鼠连续8天给予增强性AF刺激（30个10脉冲100赫兹串），在间隔8天后进行第九次给药。在每次增强性治疗之前、期间和之后，通过0.1赫兹单脉冲AF测试刺激在PC和嗅球（OB）中诱发的局部场电位来监测增强作用的时间进程。AF测试刺激在PC中诱发了两个不同的成分，一个早期成分（EC）和一个晚期成分（LC）。高频AF刺激使每个成分都产生了增强作用，但具有非常不同的特征。EC增强包括在每次增强性刺激期间的短暂增强，在最后一次高频串刺激后持续不到2分钟，并且在连续几天重复诱导后没有累积效应。相比之下，LC增强是逐渐发展的，需要每天进行几次增强性治疗才能达到最大幅度，并且每次诱导后衰减得更慢。此外，LC增强在其明显衰减后以潜伏形式持续至少8天，并且可以通过在实验开始时无效的重复测试刺激来恢复。OB中的增强在特征上类似于LC增强，但潜伏性增强较少。这些结果表明，这里报道的增强作用与先前在PC体外实验中证明的长期增强作用明显不同，并表明这种增强作用代表了皮层联合纤维系统内兴奋性的增加，这种增加可以以潜伏形式储存并在以后恢复。这些特征使这种增强作用成为参与嗅觉皮层长期功能变化的合适候选者。
