Neuronal response to polyP. Both CNS and PNS neurons responded to the application of polyP with a vehement burst of activity. A) Representative response of a hippocampal neuron to direct application of polyP (n = 16 of 24), in which rapid, persistent firing is observed. B) Representative response of a DRG neuron to polyP. Small nociceptive DRG neurons (<35 microns) responded with rapid firing (n = 24). C) Some neurons responded to polyP with a multiphasic response: rapid firing followed by protracted depolarization, during which time firing did not occur, that was restored upon recovery of the membrane potential (8 of 24).