The possible role of thrombin in the elimination of transient ipsilateral retinotectal projections in the chick

During development, chick ipsilateral retinotectal synapses appear at ages E10/E11, peak at E12, and are nearly obliterated by E16. These ipsilateral connection changes are part of normal nervous system developmental refinement processes. Thrombin appears active during in vitro neuromuscular refinement. Using techniques to culture embryonic chickens, protease inhibitors were administered to inhibit thrombin action and potentially "maintain" ipsilateral connections. Leupeptin (1 $\mu$M), a serine and cysteine protease inhibitor, caused no statistically significant change in E16 ipsilateral counts. The problems encountered during experimentation were fungal chick infection, chick death, and dye-labelling artefacts on slides. Protocol changes increased data output and experimental productivity. Antithrombin experiment results were inconclusive; questions involving blood brain barrier permeability are unanswered. Further work on thrombin action in chick ipsilateral elimination may prove fruitful since it is uncertain as to whether or not the blood brain barrier has hindered protease inhibitor effects in these experiments.