Long-term potentiation and depression in hippocampal slices.

Antidromic stimulation of hippocampal CA 1 cells, in the presence of Mg2+ to eliminate synaptic transmission and with a pattern of impulses which when applied via a synaptic pathway produced long-term potentiation, was found to decrease the response of the CA 1 cells to subsequent synaptic activation. It was found that stimulation via synapses with the same pattern of stimuli caused long-term potentiation in normal conditions but not in the presence of 25 mM Mg2+.