Use of cobalt impregnation as a method of identifying mammalian neural pathways

Abstract

Cobalt impregnation has been effectively used to identify invertebrate neural pathways. In the present report, several variations of the cobalt chloride, cut-axon technique were used to adapt this procedure to the mammalian trigeminal afferent system. The pulp of a canine tooth or the maxillary nerve was exposed to cobalt chloride. Subsequently, the maxillary nerve, trigeminal ganglion, and trigeminal root were excised and immersed in ammonium sulfide in order to form a cobalt sulfide precipitate. After routine histological processing, the precipitate was observed in the maxillary nerve, in cells of the trigeminal ganglion, and in the trigeminal root. The results of this study indicate that the cobalt chloride, cut-axon technique can be utilized to help clarify the trajectories of peripheral nerves in mammalian preparations.