Characteristics of Light-evoked Retinal Ganglion Cell Activity with Postnatal Maturation in SD Rat / 의학물리

As part of Korean retinal prosthesis project, we have provided preliminary experimental results regarding voltage parameters for the stimulation of chemically degenerated rabbit retina. Since our APB-treated chemically degenerated retina is only ON-pathway blocked, now we switch our experiments to more appropriate retinal degeneration model, genetically degenerated retina model (RD mouse: rd/rd (C3H/HeJ)). Before studying with RD mouse, we started control experiments with normal SD rat to understand characteristics of retinal ganglion cell activity with postnatal maturation in rodents. Ganglion cell activities were recorded with 8x8 multi-electrode array. Moving spontaneous bursts appeared until postnatal day of 15. During pre-eye opening period, no light evoked response appeared. After postnatal day of 2 weeks (post-eye opening period), ON-, OFF- and ON/OFF response appeared. The fractional distributions of ON, OFF, and ON/OFF ganglion cell is about 40%, 50%, and 5%. The percentage (%) of light evoked response in each dorso-temporal, ventral, and dorso-nasal area of eye is about 50%, 37.5% and 12.5%, respectively. We concluded that the optimal period for experiment in rodent is about postnatal day of 2~3 weeks.

Area-Specific Postnatal Maturation of the Calcium-Binding Proteins Parvalbumin- and Calbindin-Immunoreactive Neurons in the Rat Hippocampus

The present study was attempted to obtain the regional differences of development of the parvalbumin- and calbindin-ir neurons in the maturing rat hippocampus. Sprague-Dawley rats at 3, 7 days, 2, 3, 4, 5, 6, and 9 weeks of age were transcardially perfused with 4% paraformaldehyde fixative. The hippocampus was cut into 30 or 40(m sections with a cryostat. Immunohistochemical staining was performed for the parvalbumin and the calbindin using ABC method. The parvalbumin-ir neurons and their axon plexuses achieved the adult patterns as following sequences;CA2 and CA3 at ghe second postnatal week, CA1 at the third week, and dentate granule cell layer by fifth postnatal week. In addition, the calbindin-ir neurons showed the adult patterns by second postnatal week in CA2, CA3, mossy fibers, and the molecular layer of the dentate gyrus, the CA1 at the third week, and finally the dentate granular cell layer by fifth week. These results revealed that time course of the maturation of the parvalbumin- and calbindin-ir neurons in the rat hippocampus showed an area-specificity. The delayed maturation of CA1 and the latest maturation of the dentage granular cell layer suggested that the neurons in these locations seemed to exhibit differential responses to the conditions of increased intracellular calcium, when compared with other areas or with the adult hippocampus.