We used in vivo microdialysis to determine if infusion of depolarizing concentrations of potassium stimulated striatal excitatory amino acid (EAA) efflux in post-natal day (PND) 7 rats. Dialysis probes were perfused with 100 mM KCl for 60 min (n = 6); EAA efflux was unaffected until 40-60 min after onset of the infusion, when a trend towards increased EAA efflux was observed (glutamate 284 +/- 56% of baseline). In animals exposed to 8% oxygen (n = 7) before a more prolonged (100 min) KCl infusion, again over the first 40 min of KCl there were no changes in EAA efflux; subsequently, glutamate, aspartate and taurine efflux increased (peak values 682 +/- 187%, 228 +/- 32%, and 1208 +/- 437% of baseline). These data suggest that in PND 7 rats a substantial contribution to basal striatal EAA efflux may be derived from non-neurotransmitter pools.