Figure 7. A facilitating connection onto a thorny oriens-lacunosum moleculare interneurone at the CA1/CA3 border exhibits only enhanced facilitation at short interspike intervals.

A, the postsynaptic thorny oriens-lacunosum moleculare (OLM) cell at the CA1/CA3 border is morphologically intermediate between OLM cells typical of CA1 and CA3 (Freund & Buzsáki, 1996), since its dendrites (red) extend horizontally in both subfields, but also extend into stratum radiatum in CA3. Its axons (blue) descend to stratum lacunosum moleculare (SLM) but were cut in this slice. Strong facilitation of second and subsequent EPSPs in trains is apparent following all first EPSPs (B) and following first spike failures (C). This facilitation is greatest at the shortest interspike intervals. Under these conditions, therefore, facilitation alone accounts for these data.