Distribution and organization of spino-reticular afferents in the brain stem of rat.

The spino-reticular projection was studied, using the silver impregnation method according to NAUTA in 15 rats with various lesions in the spinal cord. The brains were cut in frontal, sagittal or horizontal sections. Two bundles were found projecting from the spinal cord into the reticular formation: The dorso-medial bundle contains independent spino-reticular fibres which terminate in the nucleus reticularis lateralis and in the medial nuclei of the reticular formation of the rhombencephalon (this bundle is topographically organized). The spino-reticular projection to the mesencephalon runs separately in the ventro-lateral bundle, which is a complex of spino-cerebellar, spino-tectal and spino-thalamic pathways. The spino-reticular projection to the mesencephalon is is diffuse and has no sign of organization as opposed to the dorso-medial spino-reticular tract.