Journal of Neuroscience, Vol 7, 3317-3324, Copyright © 1987 by Society for Neuroscience
Cell-specific regulation of neuronal production in the larval frog retina
TA Reh
Department of Medical Physiology, University of Calgary, Alberta, Canada.
We have previously postulated the existence of a feedback mechanism from
differentiated neurons that regulates the production of new neurons.
Evidence for such regulatory feedback comes from experiments in which
dopamine-containing amacrine cells, ablated in the developing retina by
6-hydroxydopamine (6-OHDA), were up-regulated in their production. To
determine whether this is a general phenomenon of the developing retina,
the neurotoxin kainic acid (KA) was injected intraocularly in
midlarval-stage Rana pipiens tadpoles to produce selective lesions of
certain retinal cell types. After periods of 1-21 d, the animals received
intraperitoneal injections of 3H-thymidine. Animals were then allowed to
survive for periods of up to 3 weeks and were then fixed, the eyes embedded
in plastic, sectioned at 3 micron, and processed for autoradiography by
standard methods. At the dosage used, the KA produced a 52% decline in the
cell density of the inner nuclear layer (INL), a 37% decline in the retinal
ganglion cell layer (RGC), and no significant change in the density of
cells in the outer nuclear layer (ONL). The 3H-thymidine allowed us to
detect any changes in the number of new cells added to the retina after the
KA lesion. Within the first week after the KA injection, there was a
decrease in the number of 3H-thymidine (3H-Thy)-labeled cells in the
lesioned eye as compared to in the control retina; however, KA treatment of
slice cultures demonstrated that the toxin does not affect proliferating
neuroblasts directly.(ABSTRACT TRUNCATED AT 250 WORDS)