Centrifugal innervation of goldfish retina from ganglion cells of the nervus terminalis

Abstract

Cobaltous‐lysine was applied to one optic nerve of normal goldfish in order to determine the source of the centrifugal innervation of the retina. Cobalt‐filled cells were not observed in the optic tectum, pretectum, thal‐amus, or hypothalamus. However, filled cells were observed outside the central nervous system either interspersed between the olfactory nerve fibers orrostrally along the ventromedial aspect of the olfactory bulbs. These cells appear to correspond to the ganglion cells of the nervus terminalis. The cells were located bilaterally and had dendrites that branched in close proximity to the cell body and axons that coursed caudally through the medial olfactory tract. The axons traveled in the ventral forebrain and entered the optic tracts. The axons also gave off fine branches that appeared to terminate in the vicinity of the anterior commissure and in the preoptic region. Application of cobaltous‐lysine to a cut olfactory tract resulted in cobalt‐filled fibers in the optic tracts, retinal optic fiber layer, and retinal ganglion cell layer. However, the precise terminations of these fibers within the retina could not be readily established. The results are discussed with respect to the plethora of sources of retinopetal cells observed by others in fish and with respect to the innervation of the retina by luteinizing hormone‐releasing hormone axons.