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Yasushi Fujita, Donald G Puro; Bioelectric profile of the developing retinal vasculature. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4539.
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© ARVO (1962-2015); The Authors (2016-present)
Despite intensive study of retinal vascular development, the bioelectric features of blood vessels in the immature retina are unknown even though voltage is well-established to play a critical role in regulating blood flow. Here, we performed the first electrophysiological characterization of the vasculature in the developing retina.
Voltages and currents were measured via perforated-patch pipettes sealed onto vessels in intact ex vivo retinas of postnatal day 3 (P3) to adult Long-Evans rats. To help correlate electrophysiological findings with anatomical features, retinas were stained with the endothelial cell marker, isolectin GS-IB4.
Current-clamp recordings revealed that at ≤P14 the resting membrane potential of retinal blood vesselsis significantly higher than in adults; namely, -72 ± 2 mV (n=21) versus -51 ± 1 mV (n=22; P<0.0001). Between P14 and P21, the retinal vascular voltage decreases to the adult level. Voltage-clamp experiments indicated that the greater hyperpolarization at ≤P14 is due to the activity of KATP channels, the Na+/Ca2+ exchanger’s very negative equilibrium potential and the relatively small non-specific cation conductance. Since immature retinas have a high oxidant level, we assessed the role of oxidation in causing vascular hyperpolarization. Indicative of the importance of oxidants, exposure of P11 to P14 ex vivo retinas to the antioxidant, n-acetyl cysteine, resulted in a vascular bioelectric profile similar to that observed in ≥P21 retinas. Although we speculated that increased hyperpolarization is unique to growing vessels, we found that vascular voltages remain highly hyperpolarized at P14 even though lectin staining revealed that superficial and deep vascular layers reach the retinal periphery at P13. On the other hand, the decline in vascular voltage observed during the third postnatal week did correlate temporally with a period of extensive pruning within the retinal vasculature.
This first bioelectric analysis of blood vessels in the developing retina indicates that oxidation drives hyperpolarization of the immature vasculature. This hyperpolarization may account for the prominent vasodilation observed in the perinatal retina.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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