Fig. 4.
Furosemide affected the reversal potential of dendritic IGABA more strongly than of somatic IGABA. A, Pressure ejection of GABA (▴) (distance to the soma is given inparentheses) induced an inward current when applied close to the soma (A1) but an outward current in dendrites (A2). Under control recording conditions (15 mm [A−]pip; 2 mm [K+]o; VH −66 mV), sIPSCs were recorded at aVH at which outward sIPSCs predominated. In the presence of tetrodotoxin (TTX) to eliminate sIPSCs, furosemide reversed the current direction of dendriticIGABA (A2), whereas the amplitude of somatic IGABA was increased only slightly (A1). Both effects were completely reversible. To obtain a clear signal in presence of sIPSCs, slightly larger ejection pressure was used than was needed in TTX.B, Chart recording of the time course of the furosemide-induced shift of EGABA. In the same cell as in A, dendriticIGABA measured in TTX reversed current direction on application of furosemide. This effect readily reversed on washout.