Selective lesions of granule cells by fluid injections into the dentate gyrus

Granule cells were selectively lesioned by injections of fluid into the infragranular cleavage plane in the dentate gyrus. The granule cells were axotomized by the cavity created by the fluid and 6 days after the injection there were no granule cells at the injection site. The size of the granule cell loss could be altered by varying the volume and rate of the injection. The loss of granule cells led to a shrinkage of the molecular layer and to a reactive gliosis. The lesion also caused an increase in the density of AChE and Timm staining in the molecular layer above the lesion. Although the increased density of AChE and Timm staining may have been due in part to the shrinkage of the molecular layer, part was due to the growth of inputs in response to the loss of granule cells and/or to the axotomy of the input terminals. The changes seen in the molecular layer above the lesion site ended abruptly at the margins of the lesion and the adjacent molecular and granule cell layers appeared normal.