Synaptic circuitry of neuropeptide-containing amacrine cells in the retina of the cane toad, Bufo marinus.
Synaptic connections of amacrine cells with substance P-like or neuropeptide Y-like immunoreactivity (SP-LI or NPY-LI) in the retina of the cane toad, Bufo marinus, were investigated using ultrastructural immunocytochemistry. The perikarya of SP-LI or NPY-LI amacrine cells were located in the innermost row of the inner nuclear layer. The synapses associated with SP-LI amacrine cells were distributed mainly in sublaminae 3 and 4 with about 10% in sublamina 1 of the inner plexiform layer. The synapses formed by NPY-LI amacrine cells were found in sublaminae 1, 2, and 4 with approximately equal frequency. Of a total of 175 SP-LI profiles, 56% were in presynaptic positions and 44% in postsynaptic positions. The synaptic inputs to SP-LI profiles predominantly derived from other unlabeled amacrine cell dendrites, and to a lesser extent, from bipolar cell terminals. The majority of synaptic outputs from SP-LI amacrine cell dendrites were directed onto unlabeled amacrine cell processes. The SP-LI profiles also made synapses onto bipolar cell terminals and formed synapses onto presumed ganglion cell dendrites. Of a total of 200 NPY-LI profiles, 48% were in presynaptic positions and 52% in postsynaptic positions. The profiles of NPY-LI amacrine cells mainly received their synaptic inputs from other unlabeled amacrine cell processes, and to a lesser extent, from bipolar cell terminals. The majority of NPY-LI amacrine cell profiles gave their synaptic outputs onto unlabeled amacrine cell dendrites, and others formed synapses onto presumed ganglion cell processes. These results suggest that these two populations of neuropeptide-containing amacrine cells in the Bufo retina are involved in different synaptic circuits.
Zhu
B S
BS
Department of Anatomy and Histology, School of Medicine, Flinders University of South Australia, Adelaide, Australia.
Gibbins
I
I
D000818:Animals; D002024:Bufo marinus / Q000502:physiology*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000502:physiology; D009478:Neuropeptide Y / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D013373:Substance P / Q000378:metabolism; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
D009478:Neuropeptide Y; D009479:Neuropeptides; D013373:Substance P