Dorsal-ventral differentiation of short-term synaptic plasticity in rat CA1 hippocampal region

Two forms of short-term synaptic plasticity (STP), paired-pulse facilitatio n (PPF) and frequency potentiation (FP) of CA1 field excitatory postsynapti c potentials (EPSP) to afferent stimulation were compared in slices taken f rom the dorsal and ventral parts of rat hippocampus. While dorsal slices sh owed significant PPF at all interpulse intervals (20-1400 ms, 80% at 40 ms) , PPF in ventral slices was substantially weaker at intervals shorter than 100 ms (19% at 40 ms) and nit at longer intervals. While dorsal slices show ed substantial FP at frequencies 1-40 Hz and frequency depression at 50-100 Hz, ventral slices showed only a much smaller potentiation at 1 Hz and sub stantial depression at 20-100 Hz, Decreasing [Ca2+](o) from 2 to 1 and 0.5 mM substantially reduced the baseline EPSPs in both groups of slices but it s effect on PPF was greater in ventral slices. On the contrary when [Ca2+]( o) was increased to 5 mM only dorsal slices showed an enhancement of baseli ne EPSP. It is concluded that ventral hippocampus CA1 area has a specific d eficit in STP, which is related to the important presynaptic role of calciu m and is consistent with a relatively higher transmitter release probabilit y. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.