Examples of ionic currents in peritoneal macrophages. ACh (1 mM) and ATP-Na⁺ (1 mM) agonists were applied in 0.5 s (A and B) or 1 s (C and D) pulses, as indicated by the horizontal bars. A and B represent current traced obtained in sequence in the same cell, which did not respond to ACh, but responded to ATP-Na⁺ with a fast current with clear desensitization in the presence of the agonist. C and D represent another cell, which presented a different response to ATP, without desensitization. Cells were maintained at a potential of - 60 mV; representative records of 47 cells from 7 culture plates of 6 animals.