title: Synaptic organization of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina.
abstract: Immunoelectron microscopy was used to investigate the ultrastructural features and synaptic relationships of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina. Serotonin-positive somas exhibited an evenly distributed peroxidase reaction product throughout their cytoplasm. Their nuclei were unstained and possessed indented nuclear membranes. Serotonin-immunoreactive processes were generally stained throughout with the exception of their mitochondria, whose morphology was often disrupted by the staining reaction. They were further characterized by an occasional dense-cored vesicle/s in addition to a generally homogeneous population of small, round, clear synaptic vesicles. Serotonin-immunoreactive amacrine cell processes formed conventional synapses that were characterized by symmetrical synaptic membrane densities. A total of 222 synaptic arrangements were observed that involved the immunostained processes of serotonin-amacrine cells. As presynaptic elements, they primarily contacted amacrine cells processes (37.8%). They also provided substantial synaptic input to processes that lacked synaptic vesicles (16.2%) and whose origin was unidentified. Serotonin-processes provided a far fewer number of synaptic contacts onto the processes of bipolar cells (1.4%) and the somas of cells in the amacrine cell layer (0.5%). As postsynaptic elements, they received synaptic inputs from amacrine cells (27.9%) and bipolar cells (16.2%). With the exception of their synapses onto bipolar cells and the somas of cells in the amacrine cell layer, each of the synaptic relationships of serotonin-amacrine cells was observed in each of sublayers 1-5 of the inner plexiform layer.
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: E A
authors.initials: EA
authors.lastname: Wilson
mesh_terms: D000557:Ambystoma; D000818:Animals; D007150:Immunohistochemistry; D007814:Larva; D008854:Microscopy, Electron; D012160:Retina / Q000166:cytology* / Q000648:ultrastructure; D012701:Serotonin / Q000032:analysis*; D013569:Synapses / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000648:ultrastructure
chemical_list: D012701:Serotonin