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D.M. Wu, S. Yamanishi, M. Minami, D.G. Puro; Physiology of Developing Retinal Microvessels . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3253.
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Purpose: Despite keen interest in retina angiogenesis, little is known about microvascular physiology in the developing retina. Thus, the goal of this project was to establish an experimental preparation to facilitate physiological studies of immature retinal microvessels. Methods: We studied the rat microvasculature because it is immature at birth, with extensive vascular remodeling occuring during the postnatal time period. We found that complexes of postnatal (P2–P12) rat retinal microvessels can be isolated after digestion of a retina with plasmin and papain, followed by gentle pressing of the retina between two glass coverslips; complexes of microvessels adhere to the glass. To assess physiological parameters, we performed perforated patch–clamp recordings. Simultaneously, time–lapse photography of freshly isolated microvessels permitted correlation of electrophysiological changes with vasomotor activity. Results: Suggestive of microvascular health, the membrane potential of cells in microvascular complexes from P2–P12 rats was –38 ± 3 mV (n=30), which was not significantly (p=0.2) different than in adult rat retinal microvessels (Wu et al, 2001). Because we have extensively studied the actions of P2X7 purinoreceptor activation in the adult microvasculature, we tested the effect on immature vessels of the P2X7 agonist, benzoylbenzoyl–ATP (BzATP). Similar to the adult, exposure of postnatal microvascular complexes to this agonist induced a transient increase in inward current and vigorous contractions. However, unlike the adult, BzATP could subsequently activate an outward current that caused immature microvascular cells to hyperpolarize by 19 ± 6 mV. Conclusions: We found that there are functional P2X7 purinoreceptors in the retinal microvasculature of the postnatal rat and that there appear to be significant physiological differences in the responses of developing and mature microvessels. Our model system should permit detemrination of the mechanisms by which extracellular molecules regulate the physiology of immature retinal microvessels.
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