title: Microglial responses to focal lesions of the rabbit retina: correlation with neural and macroglial reactions.
abstract: There is a very wide spread Müller glial response to focal laser photocoagulation lesions in the rabbit retina. In this study we have described the microglial response to similar lesions and compared this with the Müller and retinal ganglion cell responses. Microglia were labelled using nucleoside di-phosphatase histochemistry in adult rabbit retinal wholemounts and compared with axonal and Müller cell responses as shown respectively by neurofilament and GFAP immunohistochemistry. In the normal retina, microglia were located in the nerve fibre layer (NFL), inner plexiform layer (IPL), and sparsely in the outer plexiform layer (OPL). Following laser photocoagulation each layer reacted differently. The NFL reaction was exclusively associated with axonal degeneration, as shown by abnormal neurofilament label, and therefore only started several days after injury. In the IPL, neighbouring microglial cells directed their processes towards the lesion by 2 h and had migrated into the lesion by 6 h, but the reaction did not extend more than 2-3 cell diameters from the lesion and was over by 7 days. In the OPL the cell density increased by 1-2 days over a few millimeters from the lesion. The Müller cells expressed GFAP for several millimeters from the lesion starting at 24 h and persisting for over one month and therefore the correlation with the microglial reaction was poor. The different reaction in each retinal layer is evidence that microglial responses are modulated by local factors, probably mainly by contact with injured retinal elements as well as diffusable factors.
authors.affiliation: WARP Research Centre, Lions Eye Institute, University of Western Australia, Nedlands.
authors.forename: M F
authors.initials: MF
authors.lastname: Humphrey
authors.forename: S R
authors.initials: SR
authors.lastname: Moore
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism; D000818:Animals; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D007150:Immunohistochemistry; D007834:Lasers; D008028:Light Coagulation; D017628:Microglia / Q000502:physiology*; D009410:Nerve Degeneration / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D016900:Neurofilament Proteins / Q000378:metabolism; D009457:Neuroglia / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000378:metabolism / Q000473:pathology; D011817:Rabbits; D012160:Retina / Q000293:injuries / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000502:physiology
chemical_list: D005904:Glial Fibrillary Acidic Protein; D016900:Neurofilament Proteins; D017766:Acid Anhydride Hydrolases; C023837:nucleoside-diphosphatase