Substance P-like immunoreactive projection to the hippocampal formation from the posterior hypothalamus in the cat

Following the injection of the fluorescent tracer, 4',6-diamidino-2-phenylindol-2HCl (DAPI) or Fluoro-Gold (FG), into the hippocampal formation of the cat, retrogradely-labeled cells were seen mainly in the supramammillary nucleus and the posterior hypothalamic area. Some of these labeled cells contain substance P-like immunoreactivity (SP-LI). When wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) was injected into the supramammillary nucleus and its adjacent regions, anterogradely-labeled terminals were detected, for the most part, in the granular layer and the supragranular molecular layer of the dentate gyrus as well as in the pyramidal layers of the hippocampus and subiculum. All of these layers were included within the terminal areas containing the SP-like immunoreactivity.