Differences in paired‐pulse facilitation and long‐term potentiation between dorsal and ventral CA1 regions in anesthetized rats

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Abstract
To clarify hippocampal regional differences in synaptic plasticity, paired‐pulse facilitation (PPF, a form of short‐term plasticity), long‐term potentiation (LTP, a form of long‐term plasticity), and their interactions were studied in the dorsal and ventral hippocampal CA1 regions of anesthetized rats. Baseline PPF and post‐LTP PPF experiments were conducted at interstimulus intervals (ISIs) of 20–320 ms. A general protocol (100 Hz, 1 s) and a stronger protocol (250‐Hz pulse series) were applied for LTP induction. PPF were observed in both regions; however, the degree was lower and the range of ISIs was narrower in the ventral region compared with the dorsal region. The degree of ventral LTP was lower than that of the dorsal LTP. The interaction between PPF and LTP was observed in both regions (PPF change correlated inversely with degree of baseline PPF). However, this was also different in each region. Dorsal PPF increased or decreased; in contrast, ventral PPF of short ISIs after LTP only decreased. These regional differences in short‐term and long‐term synaptic plasticity may explain a consequence of different afferent inputs and information processing. Hippocampus 2001;11:655–661.