Neurotransmitter candidates in the retina of the mudpuppy, Necturus maculosus

Abstract

Neurons accumulating (3H)-glycine and (3H) GABA were demonstrated with the use of autoradiography. Both were accumulated by different types of amacrine cells, similar those of goldfish. (3H)-GABA was also accumulated by horizontal cells, again similar to the goldfish. These results and physiological studies from other laboratories suggest that GABA and glycine are neurotransmitter candidates in amacrine cells of the mudpuppy. Immunoreactive neuropeptide Y (NPY), glucagon, vasoactive intestinal peptide (VIP), somatostatin, substance P, and neurotensin were found in different types of stratified amacrine cells. Weakly immunoreactive enkephalin and bombesin processes were also seen in the inner plexiform layer. Gastrin-immunoreactive neurons were not detectable. Endogenous 5-hydroxytryptamine was visualized immunohistochemically in a population of diffuse amacrine cells and some cells in the ganglion cell layer. This suggests that 5-hydroxytryptamine may be a neurotransmitter in the retina of the mudpuppy.