Distribution and synaptic organization of substance P-like immunoreactive neurons in the mouse retina

AbstractSubstance P (SP), a neuroprotective peptidergic neurotransmitter, is known to have immunoreactivity (IR) localized to amacrine and/or ganglion cells in a variety of species ’ retinas, but it has not yet been studied in the mouse retina. Thus, we investigated the distribution and synaptic organization of SP-IR by confocal and electron microscopy immunocytochemistry in the mouse retina. SP-IR was distributed in the inner nuclear layer (INL), inner plexiform layer (IPL) , and ganglion cell layer (GCL). Most of the SP-IR somas belonged to amacrine cells (2.5% of all) in the INL and their processes stratified into the S1, S3, and S5 layers of the IPL, with the most intense band in the S5 layer. Some SP-IR somas can also be observed in the GCL, which were identified a s displaced amacrine cells (82%, 1269/1550) and ganglion cells (18%, 281/1550) by antibodies against AP2α and RBPMS, respectively. Such SP-IR ganglion cells (1.2% of all RGCs) can be further divided into 3 subgroups expressing SP/α-Synuclein (α-Syn), SP/GAD67, and/or SP/GAD67/α-Syn. Possible phy siological and pathological roles of these ganglion cells are discussed. Further, electron microscopy evidence demonstrates that SP-IR amacrine cells receive major inputs from other SP-IR amacrine cell processes (146/242 inputs) and output mostly to SP-negative amacrine cell processes (291/673 outpu ts), suggesting series inhibition among amacrine cells. These results reveal for the first time an explicit distrib...
Source: Anatomy and Embryology - Category: Anatomy Source Type: research