Priming stimulation facilitates Hebb-type plasticity in the Schaffer collateral-commissural pathways of the mouse hippocampus.

Hebb-type plastic changes of synaptic transmission were analyzed in the Schäffer collateral-commissural pathways (SC) of the mouse hippocampal slice. Low frequency (0.05-0.1 Hz) SC stimulation (S2) was paired with intracellular depolarization (100-200 ms; 2-3 nA) of CA1 pyramidal. Postpairing facilitation of synaptic responses in picrotoxin-free medium occurred only when S2 was "primed" with neurons the preceding shock (S1) administered through the same electrode 200 ms before S2. Priming-determined disinhibition in local circuitry is supposed to be responsible for this phenomenon.