Morphology of embryonic hippocampus transplants and generation of long-distance extrinsic graft fiber connections to the lateral septum and the entorhinal cortex in the mature rat brain

Abstract

Pyramidal neurons inside transplants of embryonic nervous tissue are capable of generating axonal extrinsic hippocampal fiber connections over considerable distances to appropriate target areas in the mature brain. The establishment of long-distance graft efferents to the lateral septum and to the entorhinal cortex was shown by retrograde transport of the tracers HRP and bisbenzimide which were injected into these areas after bilateral neurotoxic lesions of the hippocampus. Additional AChE-staining demonstrated the presence of an afferent cholinergic graft input mainly from the medial septum via the fornix. Morphological analysis of the transplants grafted as cell suspensions showed typical details of the original hippocampus cytoarchitecture with bands of pyramidal and granule cells.