Background adaptation in a rat model of retinopathy of prematurity.

Low dark-adapted, scotopic retinal and visual sensitivity in retinopathy of prematurity (ROP) could be due to disease of the inner retina, or the recently described rod photoreceptor abnormalities. Receptoral disease decreases catch of quanta from both test flashes and steady background lights; increment threshold functions are shifted up and right. In diseases with normal receptors but low retinal sensitivity due to abnormal post receptoral processing, the increment threshold functions are shifted up with no horizontal translation.

Rod photoreceptors in infant rats with a history of oxygen exposure.

Purpose: To study in an infant rat model of retinopathy of prematurity, the rod photoreceptors, which are known to have attenuated photoresponses.

Methods: Rhodopsin was extracted from whole retinas, the thickness of the rod outer segment (ROS) layer was measured, large phagosomes were counted, and the ROS ultrastructure was examined in the retinas of oxygen-exposed and control rats, ages 13 and 18 days. Rhodopsin absorbances in the ROS were measured by microspectrophotometry at age 20 days.

Correlation of vascular permeability factor/vascular endothelial growth factor with extraretinal neovascularization in the rat.

Objective: To determine whether neovascularization was spatially correlated with the distribution of messenger RNA for vascular permeability factor/vascular endothelial growth factor (VPF/VEGF).

Methods: Neonatal rats were raised 8 days in 80% oxygen with daily intervals of relative hypoxia in room air, then transferred to room air for 5, 7, or 10 additional days. In situ hybridization for VPF/VEGF expression and avascular area were examined in retinas from oxygen-exposed animals and room-air controls.

Effect of prior oxygen exposure on the electroretinographic responses of infant rats.

Purpose: To study electroretinographic responses of infant rats with a history of exposure to high-ambient oxygen.

Methods: Electroretinographic responses to a range of full-field stimuli were recorded from 13-day-old (n = 8) and 18-day-old (n = 10) rats with a history of intermittent exposure to 80% oxygen and age-matched controls. The a-waves were fitted with a model of rod cell sensitivity and saturated response amplitude.

Extraretinal neovascularization induced by hypoxic episodes in the neonatal rat.

Purpose: To test the hypothesis that hypoxia induces retinal neovascularization.

Methods: To produce relative hypoxia in the avascular retina, newborn rats were exposed for 11 days to 80% oxygen interrupted daily by short episodes in room air. Episodes in room air lasted 1/2 hour or 1 hour followed by abrupt reintroduction, or 1/2 hour followed by progressive reintroduction to 80% oxygen lasting 3 hours to prolong the period of hypoxia.