Capsaicin-evoked Ca++ influx was recorded before and 10 minutes after perfusion of growth factors on isolated DRG neurons. Each growth factor concentration (0.1, 1, 10, 100ng/ml) was tested on individual coverslips, cells were allowed to recover for 30 minutes and maximal doses of each growth factor were given to identify all potential responders in the field and to determine maximal potentiation magnitude for each responsive cell. Representative traces are shown in A. Note that the magnitude of potentiation increases with increasing growth factor concentration (A and C), as does the number of cells potentiated (B). Although all four factors potentiated capsaicin-evoked responses, all GDNF family members were substantially more potent than NGF.