Some aspects of brain morphology of the chronic cat and kitten preparations with brain stem transected at the pretrigeminal level.

In two adult cats and in three kittens aged from 8 to 11 days the brain stem was transected at the pretrigeminal level. The preparations were maintained from 7 to 79 days and processed histologically together with nonoperated controls. In kitten preparations brain was underdeveloped as shown by less numerous secondary sulci on the surface of the cortex. However, both cat and kitten preparations showed similar retrograde and anterograde neuronal degeneration. They also showed a similar transneuronal degeneration apparent in an increased density of neurons and their shrinkage in several structures investigated in the isolated cerebrum and the lower brain stem. Thus in kitten preparations a direct effect of transection predominated that of brain development. In the adult preparations at the level of transection a great accumulation of macrophages was found and the scar was built with connective tissue. In contrast, in kittens the transection scar was well delineated and built by astrocyte processes.