Anatolian ground squirrel (Spermophilus xanthoprymnus) retina: Comparative expression of synaptophysin, NeuN, calbindin-D28k, parvalbumin, glial fibrillary acidic protein, and Iba-1 during pre-hibernation and hibernation.

Hibernation induces significant molecular and cellular adaptations in the retina to maintain function under reduced metabolic conditions. This study aimed to investigate the expression of neuronal, synaptic, and glial markers in the retina of Spermophilus xanthoprymnus during pre-hibernation and hibernation periods using immunohistochemical staining. Synaptophysin expression, restricted to the inner plexiform layer (IPL) and outer plexiform layer (OPL) during pre-hibernation, significantly increased in both layers during hibernation, with additional expression observed in the outer nuclear layer. NeuN immunoreactivity remained unchanged in the ganglion cell layer (GCL) but increased notably in the INL during hibernation. Calbindin-D28k expression, prominent in the INL and plexiform layers during pre-hibernation, decreased markedly in hibernation. In contrast, parvalbumin expression increased across all retinal layers, except the photoreceptor layer, during hibernation. Glial fibrillary acidic protein (GFAP) expression, observed in the NFL and GCL, was significantly reduced during hibernation. Iba-1 immunoreactivity, sparse in the IPL and OPL during pre-hibernation, showed a pronounced increase in the IPL, OPL, and INL during hibernation periods. In conclusion, the expression of synaptophysin, NeuN, calbindin-D28k, parvalbumin, GFAP, and Iba-1 was investigated for the first time in the retina of the Anatolian ground squirrel during pre-hibernation and hibernation. This study reveals region-specific shifts in retinal marker expression during pre-hibernation and hibernation, providing a basis for future research into visual system adaptations and retinal plasticity under metabolic suppression.