In vitro, extracellular electrophysiological recording was used to test granule cell responses in P60 rats after neonatal PCA and 5,7-DHT. Granule cell population EPSP and spike responses were in the normal range for both PCA and 5,7-DHT groups. However, the degree of paired pulse facilitation was reduced in both of these groups relative to control, reflecting a diminished synaptic drive. Synaptic potentiation in the 5,7-DHT group was not different from control, but was significantly reduced in slices from PCA-treated rats. (C) 1999 Elsevier Science B.V. All rights reserved.