A neurotensin-immunoreactive pathway from the subiculum to the mammillary body in the rat.

The existence of a neurotensin-like immunoreactive (NT-IR) pathway from the subiculum to the mammillary body was demonstrated in very young rats using immunocytochemistry, knife cut, electric lesion and retrograde tracer techniques. Unilateral hemitransection of the dorsal fornix caused a marked reduction of NT-IR fibers in the ipsilateral mammillary body. Unilateral electric lesion of the subiculum also resulted in ipsilateral reduction of NT-IR fibers in the mammillary body. Biotin-wheat germ agglutinin (B-WGA), injected into the mammillary body, labeled neurons in the ipsilateral subiculum which were shown by double staining to have NT-IR cytoplasm. These findings demonstrate the presence of a major NT-IR fiber pathway from the subiculum to the mammillary body via the fornix.