Cobalt destroys neurons without destroying fibers of passage in the lateral geniculate nucleus of the cat.

When several injections of 4 mM cobalt chloride are made into the lateral geniculate nucleus of the cat, cell somata are destroyed while fibers-of-passage are spared. Nissl and Wiel stains were used to assess the extent of cell and fiber damage, respectively, for cobalt lesions of layer A. Retrograde transport of horseradish peroxidase from the visual cortex to geniculate cells surrounding the lesions was used to demonstrate the integrity of fibers passing through the area depleted of cells. Cobalt provides a versatile and precise method of disrupting neural pathways. Depending upon the number and timing of the injections, the disruption can be temporary, resulting from a reversible inactivation of synaptic transmission, or permanent, caused by soma death.