Morphological evidence that CA1 hippocampal afferents monosynaptically innervate PV-containing neurons and NADPH-diaphorase reactive cells in the medial prefrontal cortex (Areas 25/32) of the rat.

Immunocytochemical and ultrastructural evidence is presented indicating that direct inputs from the hippocampal CA1 field to prelimbic (area 32) and infralimbic (area 25) cortices in the rat, innervate not only 'spiny' (presumed pyramidal) neurons but also monosynaptically contact NADPH-diaphorase reactive cells and parvalbumin-containing local circuit neurons-the latter cell type is shown to be GABA immunoreactive. Similar evidence of direct CA1 input to local circuit neurons containing either calbindin or calretinin was not found.