Physiological evidence for a possible projection from dorsal subiculum to hippocampal area CA1

The substantial forward projection from hippocampal area CA1 to the subiculum has been comprehensively described, both anatomically and neurophysiologically. There are few data, however, regarding the existence of a backward projection from the subiculum to area CA1. We present here new electrophysiological evidence for the existence of this projection. We demonstrate a positive-going deflection in the evoked synaptic response in area CA1 following stimulation in dorsal subiculum. We also found a small, but significant, paired-pulse facilitatory effect at a 100-ms interstimulus interval. We were unable to induce long-term potentiation following high-frequency stimulation, but were able to induce short-term potentiation.