Direct connections of the hippocampus with the retrosplenial cortex in rats

Abstract

Connections of the retrosplenial cortex with the hippocampus in rats were investigated by the method of retrograde axonal transport of horseradish peroxidase (HRP). If a crystal of HRP was introduced into the dorsocaudal part of the retrosplenial cortex, HRP-labeled cells were found in the rostral pole of hippocampal area CA3 and in the presubiculum. After iontophoretic injection of HRP into the rostral pole of the hippocampus, HRP-labeled cells were found in layers V and VI of the retrosplenial cortex and in the presubiculum. The results are evidence of reciprocity of direct connections between the rostral pole of the hippocampus and the retrosplenial cortex, and also of the existence of direct efferents of the dorsal subiculum to the rostral pole of the hippocampus.