| Autor: |
Marshak DW; Department of Neurobiology and Anatomy,University of Texas Medical School,Houston,Texas., Chuang AZ; Department of Ophthalmology and Visual Science,University of Texas Medical School,Houston,Texas., Dolino DM; Department of Neurobiology and Anatomy,University of Texas Medical School,Houston,Texas., Jacoby RA; Department of Ophthalmology,Baylor College of Medicine,Houston,Texas., Liu WS; Department of Neurobiology and Anatomy,University of Texas Medical School,Houston,Texas., Long YE; Department of Neurobiology and Anatomy,University of Texas Medical School,Houston,Texas., Sherman MB; Department of Biochemistry & Molecular Biology,University of Texas Medical Branch,Galveston,Texas., Suh JM; Department of Neurobiology and Anatomy,University of Texas Medical School,Houston,Texas., Vila A; Department of Ophthalmology and Visual Science,University of Texas Medical School,Houston,Texas., Mills SL; Department of Ophthalmology and Visual Science,University of Texas Medical School,Houston,Texas. |
| Abstrakt: |
The goals of these experiments were to describe the morphology and synaptic connections of amacrine cells in the baboon retina that contain immunoreactive vesicular glutamate transporter 3 (vGluT3). These amacrine cells had the morphology characteristic of knotty bistratified type 1 cells, and their dendrites formed two plexuses on either side of the center of the inner plexiform layer. The primary dendrites received large synapses from amacrine cells, and the higher-order dendrites were both pre- and postsynaptic to other amacrine cells. Based on light microscopic immunolabeling results, these include AII cells and starburst cells, but not the polyaxonal amacrine cells tracer-coupled to ON parasol ganglion cells. The vGluT3 cells received input from ON bipolar cells at ribbon synapses and made synapses onto OFF bipolar cells, including the diffuse DB3a type. Many synapses from vGluT3 cells onto retinal ganglion cells were observed in both plexuses. At synapses where vGluT3 cells were presynaptic, two types of postsynaptic densities were observed; there were relatively thin ones characteristic of inhibitory synapses and relatively thick ones characteristic of excitatory synapses. In the light microscopic experiments with Neurobiotin-injected ganglion cells, vGluT3 cells made contacts with midget and parasol ganglion cells, including both ON and OFF types. Puncta containing immunoreactive gephyrin, an inhibitory synapse marker, were found at appositions between vGluT3 cells and each of the four types of labeled ganglion cells. The vGluT3 cells did not have detectable levels of immunoreactive γ-aminobutyric acid (GABA) or immunoreactive glycine transporter 1. Thus, the vGluT3 cells would be expected to have ON responses to light and make synapses onto neurons in both the ON and the OFF pathways. Taken with previous results, these findings suggest that vGluT3 cells release glycine at some of their output synapses and glutamate at others. |
