title: Colocalization of glycine in substance P-amacrine cells of the larval tiger salamander retina.
abstract: The present study was performed as part of a systematic examination of glycine's coexistence with other classical transmitters and neuropeptides in neuronal populations of the larval tiger salamander retina. Substance P immunocytochemistry was combined with either glycine immunocytochemistry or autoradiography of glycine high-affinity uptake to examine whether tiger salamander substance P-amacrine cells express these glycine markers. Double-label analyses revealed two populations of substance P-amacrine cells that express glycine immunoreactivity and glycine high-affinity uptake. The large majority of double-labeled cells were situated in the innermost cell row of the inner nuclear layer, while a smaller number were located in the inner nuclear layer in the second cell row distal to the inner plexiform layer. Double-label immunocytochemistry revealed that these double-labeled cells accounted for 91.7% of substance P-immunoreactive amacrine cells. A slightly lower percentage (90.1%) of substance P-amacrine cells were found to exhibit a glycine high-affinity uptake mechanism. Substance P-amacrine cells that did not co-label for markers of glycine activity were situated in the innermost cell row of the inner nuclear layer. Substance P-immunoreactive displaced amacrine cells were not observed to co-label for either glycine immunoreactivity or glycine high-affinity uptake. The present study reveals that the large majority of substance P-amacrine cells in the larval tiger salamander retina co-express markers of glycine activity. This finding suggests a functional diversity in the population of tiger salamander substance P-amacrine cells relative to their coexisting relationship with a major inhibitory neurotransmitter.
authors.affiliation: Alice R. McPherson Laboratory of Retina Research, Baylor College of Medicine, The Woodlands, TX 77381.
authors.forename: C B
authors.initials: CB
authors.lastname: Watt
authors.forename: V J
authors.initials: VJ
authors.lastname: Florack
mesh_terms: D000557:Ambystoma; D000818:Animals; D001345:Autoradiography; D002452:Cell Count; D005455:Fluorescent Antibody Technique; D005998:Glycine / Q000032:analysis*; D009474:Neurons / Q000737:chemistry*; D012160:Retina / Q000737:chemistry*; D013373:Substance P / Q000032:analysis*
chemical_list: D013373:Substance P; D005998:Glycine