Rat hippocampus—prefrontal multiple units and synaptic efficacy in vivo

Abstract

We recorded multiple unit activities of the CA1 region of the intermediate hippocampus and prelimbic area of the prefrontal cortex, and evoked responses in the prefrontal cortex by hippocampal stimulation in urethane-anesthetized rats. The multiple unit activities between these regions showed significant peaks of cross-correlograms, which indicated that firing initiated mainly from either the hippocampus (type HP) or the prefrontal cortex (type PH). In type HP, the slopes of evoked responses showed a significant inverse correlation with peak heights of cross-correlograms and number of bursts of multiple unit activities. These results suggest that multiple unit activity-based cross-correlograms (a measurement to test functional connectivity) are influenced by both evoked response (synaptic connectivity) and effects of local circuits.