Mitotic activity in the mouse brain after cortical and striatal lesions

Following a stab wound in the brain, mice were injected with 3H-thymidine intravenously 15 min before sacrifice. In a first series, the cells in the synthesis phase (S-cells) in the stab canal, in the adjacent areas and in the rest of the section were counted. The animals were sacrificed from 15 min to 3 days after the stab wound. An increased number of S-cells in all 3 regions was found after 2 days. 24 hr later the number of S-cells was back to normal. In another series, a guide cannula was fixed to the skull resulting in a small superficial lesion of the cortex. 2 days later a stab wound in the hemisphere was made through the guide cannula using the above-mentioned technique. The animals were injected with 3H-thymidine as above and sacrificed from 30 min to 6 days after the stab wound. In this series an increased number of S-cells was found in the whole brain 1/2 hr after the last lesion and an increased number of S-cells was found throughout the whole investigation period. The reason for this general induction is not known. In animals without a stab wound, no induction was found outside the cortical lesion.