Projections to the ventral surface of the cat brainstem demonstrated by horseradish peroxidase

Topical application of horseradish peroxidase (HRP) to the ventral surface of the medulla oblongata revealed various cells with axons terminating near this region. Fibers traced from the ventral surface originated in the nucleus of the tractus solitarius and the dorsal nucleus of the vagus, both near the dorsal surface of the medulla. Projections from the cochlear nucleus were also observed. Using short HRP contact time, fibers were shown which terminate at, or near, the ventral surface. The possible involvement of these projections in various responses mediated from the ventral surface is discussed.