Immunocytochemical localization of calbindin-D28K, calretinin, and parvalbumin in the Mongolian gerbil (Meriones unguiculatus) visual cortex.

INTRODUCTION: While most animals of the Muridae family are nocturnal, the gerbil displays diurnal activity and provides a useful model for visual system research. The purpose of this study was to investigate the localization of calcium-binding proteins (CBPs) in the visual cortex of the Mongolian gerbil (Meriones unguiculatus). We also compared the labeling of CBPs to those of gamma-aminobutyric acid (GABA)- and nitric oxide synthase (NOS)-containing neurons. MATERIAL AND METHODS: The study was conducted on twelve adult Mongolian gerbils (3-4 months old). We used horseradish peroxidase immunocytochemistry and two-color fluorescence immunocytochemistry with conventional and confocal microscopy to assess CBPs localization in the visual cortex. RESULTS: The highest density of calbindin-D28K (CB)- (34.18%) and parvalbumin (PV)-IR (37.51%) neurons was found in layer V, while the highest density of calretinin (CR)-IR (33.85%) neurons was found in layer II. The CB- (46.99%), CR- (44.88%), and PV-IR (50.17%) neurons mainly displayed a multipolar round/oval morphology. Two-color immunofluorescence revealed that only 16.67%, 14.16%, and 39.91% of the CB-, CR-, and PV-IR neurons, respectively, contained GABA. In addition, none of the CB-, CR-, and PV-IR neurons contained NOS. CONCLUSIONS: Our findings indicate that CB-, CR-, and PV-containing neurons in the Mongolian gerbil visual cortex are distributed abundantly and distinctively in specific layers and in a small population of GABAergic neurons but are limited to subpopulations that do not express NOS. These data provide a basis for the potential roles of CBP-containing neurons in the gerbil visual cortex.

Changes in Starburst Amacrine Cells in Mice with Diabetic Retinopathy.

BACKGROUND: Neurodegenerative diseases, such as diabetic retinopathy (DR) and glaucoma, induce retinal neuron loss. Acetylcholine-containing cholinergic neurons, known as starburst amacrine cells (SACs), play critical roles in the generation of precise neuronal activity in the retina and are located in the inner nuclear layer (INL, conventional) and ganglion cell layer (GCL, displaced). METHODS: This study investigated the loss of and morphological changes in SACs in the retinas of streptozotocin (STZ)-induced diabetic and insulin-deficient C57BL/6-Tg(pH1-siRNAinsulin/CMV-hIDE)/Korl (IDCK) mice. SACs were immunocytochemically localized with anti-choline acetyltransferase (ChAT) antibody, and ChAT-labeled cells in the INL and GCL in the control and experimental groups were counted along the central vertical meridian in the whole-mounted retina using conventional fluorescent or confocal microscopes. RESULTS: ChAT-immunoreactive (IR) neurons in STZ-induced diabetic mouse retina decreased by 8.34% at 4-6 weeks and by 14.89% at 42 weeks compared with the control group. Localized ChAT-IR neuron counts in the retinas of 20-week-old IDCK mice were 16.80% lower than those of age-matched control mice. Cell body deformation and aggregation were detected in the retinas of mice with DR. Single-cell injection experiments revealed the loss and deformation of dendritic branches in ChAT-IR neurons in DR. All ChAT-IR neurons expressed the calcium-binding protein calretinin, whereas no ChAT-IR neuron colocalized with calbindin-D28K or parvalbumin. CONCLUSIONS: Our results revealed that the neurodegenerative effects of the loss and deformation of ChAT-IR neurons can provide a reference for future study of this disease.