title: Substance P-immunoreactive neurons in hamster retinas.
abstract: Light-microscopic immunocytochemistry was utilized to localize the different populations of substance P-immunoreactive (SP-IR) neurons in the hamster retina. Based on observation of 2505 SP-IR neurons in transverse sections, 34% were amacrine cells whose pear-shaped or round cell bodies (7-8 microm) were situated in the inner half of the inner nuclear layer (INL) or in the inner plexiform layer (IPL), while 66% of SP-IR somata (6-20 microm) were located in the ganglion cell layer (GCL) which were interpreted to be displaced amacrine cells and retinal ganglion cells (RGCs). At least three types of SP-IR amacrine cells were identified. The SP-IR processes were distributed in strata 1, 3, and 5 with the densest plexus in stratum 5 of the inner plexiform layer. In the wholemounted retina, the SP-IR cells were found to be distributed throughout the entire retina and their mean number was estimated to be 4224 +/- 76. Two experiments were performed to clarify whether any of the SP-IR neurons in the GCL were RGCs. The first experiment demonstrated the presence of SP-IR RGCs by retrogradely labeling the RGCs and subsequently staining the SP-IR cells in the retina using immunocytochemistry. The second experiment identified SP-IR central projections of RGCs to the contralateral dorsal lateral geniculate nucleus. This projection disappeared following removal of the contralateral eye. The number of SP-IR RGCs was estimated following optic nerve section. At 2 months after sectioning the optic nerve, the total number of SP-IR neurons in the GCL reduced from 4224 +/- 76 to a mean of 1192 +/- 139. Assuming that all SP-IR neurons in the GCL which disappeared after nerve section were RGCs, the number of SP-IR RGCs was estimated to be 3032, representing 3-4% of the total RGCs. In summary, findings of the present study provide evidence for the existence of SP-IR RGCs in the hamster retina.
authors.affiliation: Department of Histology and Embryology, Sun Yat-Sen University of Medical Sciences, Guangzhou, China.
authors.forename: H B
authors.initials: HB
authors.lastname: Li
authors.forename: K F
authors.initials: KF
authors.lastname: So
authors.forename: W
authors.initials: W
authors.lastname: Cheuk
mesh_terms: D000818:Animals; D006224:Cricetinae; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000737:chemistry*; D012160:Retina / Q000737:chemistry* / Q000166:cytology; D012165:Retinal Ganglion Cells / Q000737:chemistry*; D013373:Substance P / Q000032:analysis*
chemical_list: D013373:Substance P