Synaptic plasticity dynamics in the hippocampal-prefrontal pathway in vivo

We examined the effect of long-term potentiation (LTP) on paired-pulse responses across varied stimulus intensities and interstimulus intervals (ISIs), at ascending synapses from the intermediate and ventral hippocampus to the medial prefrontal cortex in urethane-anesthetized rats. LTP significantly shifted the median effective stimulus towards lower intensities in the intermediate route, and increased at 25-ms ISI the paired-pulse response, which was inversely proportional to the stimulus intensity. In the ventral route, the paired-pulse response varied with ISI rather than intensity, and increased at 50-ms and 100-ms ISI after LTP. The intermediate synaptic plasticity significantly exhibited total amplifier dynamics with wide ranges of frequency at lower intensity and intensity at 100-ms ISI in contrast to the ventral one. NeuroReport 21:68-72 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.