Morphologic preservation and variability of human donor retina.

Purpose: To facilitate studies of human retina and utilization of human retinal tissue for treatment of retinal diseases, we studied morphologic preservation in postmortem human retina.

Methods: Morphology of retinas from thirty-one human eyes was examined using light and electron microscopy. The inner and outer retina, rod and cone photoreceptor cells, and central and peripheral retina were compared with regard to morphologic preservation.

Survival of cone responses in postmortem human retina.

A cone-mediated electroretinogram was recordable from human retinas 17-18 hours postmortem, after regeneration of visual pigments by application of 11-cis and 9-cis retinal. The cone was separated from the rod component by stimulation with flickering red light. In addition to these neuronal responses, a P2 and a slow P3 were present.

Species differences in the response of mammalian photoreceptor cyclic GMP and PIII to a reduction in calcium.

Changes in the content of cyclic GMP (cGMP), induced by exposure of isolated, dark-adapted mouse, cat and dog retinas to media depleted of calcium, have been compared with the amplitude of the trans-retinal PIII. Major differences exist in the time-course and magnitude of effects between the species and, in the cat and dog, changes in PIII (potentially a reflection of free cGMP in photoreceptor outer segments) do not correlate with those occurring in total cGMP. The observations imply species variation, not only in the enzymes maintaining cGMP homeostasis in photoreceptors, but also in phototransduction and allied processes.

Cyclic GMP, calcium and photoreceptor sensitivity in mice heterozygous for the rod dysplasia gene designated "rd".

The rise in photoreceptor cGMP, induced by less than 1.0 nM extracellular calcium, is delayed in retinas of mice heterozygous for the rod dysplasia gene (+/rd). The calcium ionophore A23187 reduces the delay, suggesting that +/rd outer segments contain more calcium than normal.

Non-competitive NMDA-receptor antagonists and anoxic degeneration of the ERG B-wave in vitro.

Studies have been undertaken to see if the non-competitive NMDA antagonists, ketamine, MK-801 and dextromethorphan would preserve the b-wave of the electroretinogram (ERG) in vitro. The drugs had no effect on the ERG b-wave, nor prolonged its survival postmortem. The present results support previous evidence suggesting that NMDA-receptors are not involved directly in synaptic transmission between photoreceptors and ON-bipolar cells.