Kinetics of cell proliferation in the halved tectum of adult goldfish.

The time course of post-operative cell proliferation was studied in the halved optic tectum of adult goldfish using autoradiographic methods. At varying intervals after bilateral optic nerve crush and unilateral lesion of the caudal hemitectum, fish were injected with [3H]thymidine and allowed to survive for designated times before sacrifice. Comparisons of labeled cell numbers in different laminar regions on the intact and operated sides of the tecta were made. When short post-injection survival times were employed, there was a bimodal increase in proliferation on both tectal sides with increases occurring by 5 and between 20 and 35 days after surgery (dpo). More labeled cells were seen on the lesioned side in the outer tectal zone in fish injected at 25 and 35 dpo. Within their inner tectal zones these same fish showed more labeled cells in the periependymal layer on the lesioned side. With extended post-injection survival there was a general decline in numbers of labeled cells on both tectal sides. The only labeled cells which persisted in force were those of the periependymal layer; equal numbers were seen on both operated and intact sides. On the basis of these observations we conclude that the cell proliferation which occurs in this situation may be attributed primarily to the effects of optic nerve regeneration; the tectal surgery per se does not induce massive cell proliferation which might numerically reconstitute the halved tectum.