Figure 6. Neither ADP nor UTP activated a membrane conductance while suramin inhibited the conductance activated by ATP.

A, continuous whole-cell current trace recorded at a holding potential of −40 mV during exposure to either ATP, ADP or UTP, all at a concentration of 100 μM. The times of exposure to each of the nucleotides are indicated by bars above the current trace. Standard intracellular and extracellular solutions. Digitized at 100 Hz, filtered at 50 Hz. Cell capacitance, 12.5 pF; series resistance, 9 MΩ. B, continuous whole-cell current trace recorded at a holding potential of −40 mV during exposure to either 0.03 mM ATP or 1 mM ADP. The times of exposure are indicated by bars above the current trace. The extracellular solution contained (mM): 151 CsCl, 0.1 BaCl₂, 5 Tes, 10 D-glucose, 1 DAP, adjusted to pH 7.4 with CsOH. Standard intracellular solution. Digitized at 100 Hz, filtered at 50 Hz. Cell capacitance, 14 pF; series resistance, 15 MΩ. C, continuous whole-cell current trace recorded at a holding potential of −40 mV, from a cell exposed to extracellular ATP (200 μM) for the duration indicated by the topmost bar. Suramin (100 μM) was included in the extracellular solution during the time indicated by the lower bar. Standard intracellular and extracellular solutions. Digitized at 100 Hz, filtered at 50 Hz. Cell capacitance, 12.5 pF; series resistance, 15 MΩ.