title: Synaptic organization of dopaminergic amacrine cells in the larval tiger salamander retina.
abstract: The ultrastructural features and synaptic interactions of tyrosine hydroxylase-like-immuno-reactive amacrine cells in the larval tiger salamander retina were examined using routine immunoelectron microscopy. The somas of tyrosine hydroxylase-like-immunoreactive amacrine cells were immunostained evenly throughout their cytoplasm. Their nuclei were generally unstained and possessed indented nuclear membranes. The processes of tyrosine hydroxylase-like-immunoreactive amacrine cells were homogeneously stained with the exception of their mitochondria, whose morphology was often disrupted by the staining procedure. Tyrosine hydroxylase-like-immunoreactive amacrine cell processes were characterized by an occasional dense-cored vesicle(s), in addition to a generally homogeneous population of small, round, agranular synaptic vesicles. They formed conventional synaptic junctions that were characterized by symmetrical synaptic membrane densities. A total of 168 synapses were observed that involved tyrosine hydroxylase-like-immunoreactive amacrine cell processes. A large percentage (79.8%) of these synaptic arrangements were found in sublayer 1 of the inner plexiform layer, while substantially lower percentages were observed in sublayers 3 (9.5%) and 5 (10.7%). They served as pre- and postsynaptic elements 63.1 and 36.9% of the time, respectively. Tyrosine hydroxylase-like-immunoreactive amacrine cell processes were presynaptic to amacrine cell processes (36.9% of total synaptic involvement) and processes that lack synaptic vesicles and whose origin remains uncertain (26.2%). They received synaptic input primarily from amacrine cell processes (31.0%). Tyrosine hydroxylase-like-immunoreactive amacrine cell processes also received a few ribbon synapses from bipolar cells (5.9%). Each of these synaptic relationships were observed in each of sublayers 1, 3 and 5 of the inner plexiform layer, with the majority of each arrangement being found in sublayer 1.
authors.affiliation: Alice R. McPherson Laboratory of Retina Research, Baylor College of Medicine, Woodlands, TX 77381.
authors.forename: C B
authors.initials: CB
authors.lastname: Watt
authors.forename: P A
authors.initials: PA
authors.lastname: Glazebrook
mesh_terms: D000557:Ambystoma; D000818:Animals; D002395:Catecholamines / Q000502:physiology; D004298:Dopamine / Q000502:physiology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D012160:Retina / Q000648:ultrastructure*; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000276:immunology / Q000378:metabolism; D014795:Visual Pathways / Q000502:physiology / Q000648:ultrastructure
chemical_list: D002395:Catecholamines; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine