CHANGES IN ULTRASTRUCTURE AND ELECTRORETINOGRAM OF BULLFROG RETINA DURING DEVELOPMENT

A study has been made with the purpose of attempting to correlate the ultrastructural and electroretinographic changes in the retina of the bullfrog during embryonic growth. On day 8 after fertilization, when we first examined the eyes for electrical responses to light, we obtained slow, cornea-negative waves. These persisted for the following 2 days and on day 11 a rapid negative deflection was added to the ERG. Cornea-positivity appeared on day 12 and remained thereafter. Electron microscopy revealed that during the period of negative responses the visual cells were well developed except for the synaptic apparatus, which reached maturity later than did the outer segments, the inner segments, and the visual cell nuclei. On day 12, when positivity was first recorded, the synaptic terminals of the receptors completed development, showing many synaptic ribbons and numerous synaptic vesicles within the synaptic body The meaning of the sequential development of the visual cells, in relation to the retinal origins of the a- and b-waves of the ERG is discussed. © 1969 Academic Press, Inc.