CNS cholinergic innervation to the hippocampus in the rat using pseudorabies virus as a neurotracer

The hippocampus is a central area of the memory-related neural system. Comb ined immunohistochemistry against choline acetyl transferase and retrograde transneuronal labelling of the pseudorabies virus were used to identity ch olinergic neurons in the central nervous system projecting to the hippocamp al formation of the rat. Five to ten muL of Bartha strain of pseudorabies V irus were injected into the dentate gyrus, CA1 and CA3 of the hippocampus o f 20 Sprague Dawley rats using stereotaxic instrument. Forty eight to 96 hr after the injection, the brains were removed and the tissue sections were processed for double immunofluorescence procedure using polyclonal antibodi es against pseudorabies virus or choline acetyl transferase. The double lab elled neurons were distributed at several different nuclei and the labellin g patterns of three different areas of the hippocampus were similar. These data suggests that the cholinergic innervation to the hippocampus were dist ributed in a transsynaptic manner throughout the whole brain area.