Zn2+ and ATP are normally present in serum at low levels and are released from some neurons during synaptic activity. In whole-cell recordings, 10 microM Zn2+ potentiated steady-state currents in rat nodose ganglion nerve cells by 18% in 0.5 microM ATP and 120% in 2 microM ATP. Fluctuation analysis of whole-cell suggested the mechanism was increased burst duration. In single-channel recordings, 10 microM Zn2+ did not increase the ATP-activated channel conductance but did increase the mean burst duration of the 35 pS primary open conductance state. These observations indicate that Zn2+ potentiates the steady-state response to extracellular ATP by increasing the burst duration of the channels.