Fig. 2.

Propagation of pain signal within the trigeminal ganglion (“cross-excitation”). Excitation potentials of neurons cause an increase in ATP release outside the cell. ATP activates P2X receptors on the postsynaptic cell membranes, as well as P2Y receptors on satellite glial cells (SGCs). ATP released from neurons and satellite glial cells causes the spread of Ca²⁺ waves in the neighboring cells, and the excitation spreads out