Decreased ability of rat temporal hippocampal CA1 region to produce long-term potentiation.

Tetanic stimulation of Schaffer collaterals in the CA1 region of transverse slices, taken from the septal (dorsal) part of young rat hippocampus, produced N-Methyl-D-aspartate-dependent long-term potentiation (LTP) of the rising slope of excitatory postsynaptic potential (mean 38%). Under identical conditions of stimulation (100 Hz, 1 s) slices taken from the temporal (ventral) third of hippocampus presented a substantially reduced ability for LTP (mean 5%). The defect appeared to lie with the induction rather than the maintenance phase of LTP. These results suggest that a significant functional differentiation at the local synaptic plasticity level occurs between the two poles of hippocampus, which together with the substantial differences in their extrinsic connections, may help explain the reported differential participation of neurons in these parts of hippocampus during animal memory tests.