[The morphology of substance P in the human brain as determined by an immuno-histo-fluorescence study]

The application of Coon's indirect method, using antisubstance P antibodies, has permitted the immuno-histo-fluorescence study of the distribution of SP positive structures in 6 human brains. Several areas of the hemispheres and of the brainstem have shown axons of various sizes and densities exhibiting SP positive varicosities. Their topographic distribution was established for the human brain and compared with the distribution observed in the brain of the rat. Both distributions appeared very similar in the somato-sensorial systems of the spinal cord, medulla and pons, in the structures of the midbrain tectum and tegmentum as well as in those of the thalamus and hypothalamus. Substantia nigra and globus pallidus showed a large amount of substance P, in human brain as well as in the rat, but in human brain, substance P positive axons were arranged in a longitudinal peridendritic "pipe" shaped manner, particularly in the antero-external and superior part of the substantia nigra as well as in the internal segment of the globus pallidus; such "pipes" were rarely seen in the rat. Moreover, in man, the pallidal substance P was almost exclusively seen in the internal segment while it spreads to the external segment in the rat. Substance P was found to be scarce in the rhinencephalic and limbic structures, the amygdala and the olfactory bulb of man, contrary to their abundance in the rat, but this peculiarity could be due more to some pathological changes associated with the advanced age of the patients whose brains were studied than to an interspecific difference.