Demonstration of spinocerebellar projections in cat using anterograde transport of WGA-HRP, with some observations on spinomesencephalic and spinothalamic projections.

Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) conjugate was injected into the lumbar or cervical spinal cord of adult cats in order to examine its usefulness as an anterograde tracer of long ascending spinal tracts. Heavily labeled fibers and terminal-like structures were found in restricted regions of the granular layer of the cerebellar cortex in all animals. The terminal-like structures showed features characteristic of mossy fiber rosettes. Many labeled terminals were found in regions anatomically and physiologically defined as cerebellar hind limb regions after lumbar cord injections. Relatively few labeled terminals were found in both hind limb and in forelimb regions after cervical cord injections. Although the cervical spinal cord is known to project to both hind limb and forelimb regions, it cannot be entirely excluded that some of the labeling in the hind limb regions was derived from uptake by fibers of passage. In addition to labeling in the cerebellar cortex, labeled fibers and terminals were also observed in the cerebellar medial and interposed nuclei, regardless of whether the injections had been made into the lumbar or the cervical spinal cord. Several midbrain and thalamic regions were found to contain labeled fibers and terminal-like profiles in all cases. In the midbrain the periaqueductal gray, the nucleus of Darkschewitsch and the posterior pretectal nucleus contained fairly dense labeling. Labeling was more scattered in the cuneiform nucleus, the mesencephalic reticular formation, the superior colliculus and in the magnocellular part of the medial geniculate body.(ABSTRACT TRUNCATED AT 250 WORDS)