Reorganization in granuloprival cerebellar cultures after transplantation of granule cells and glia. I. Light microscopic and electrophysiological studies.

Granuloprival cerebellar cultures were transplanted after 9 or 16 days in vitro with cerebellar explants that had been exposed to kainic acid. The latter contained granule cells and differentiated glia, elements lacking in granuloprival cultures. Changes induced by transplantation observed by light microscopy included interposition of granule cells among the large cortical neurons of host explants; a reduction of the excess neurites of the Purkinje cell axon collateral system that is characteristic of granuloprival explants; and the appearance of myelinated fibers in previously unmyelinated cultures. The most notable electrophysiologic consequence of transplantation was the disappearance of inhibition of cortical spontaneous activity in response to antidromic stimulation of Purkinje cell axons, correlating with the disappearance of excess neurites, and suggesting that Purkinje cell recurrent collateral inhibition was no longer the dominant mode of cortical inhibition. Restoration of missing elements in granuloprival cultures incited development of structural and functional characteristics resembling those of normal cerebellar explants.