Direct Mechanical Stimulation Mediates Cell-to-Cell Interactions in Cultured Trigeminal Ganglion Cells

Trigeminal neuralgia occurs in the orofacial region, characteristically causing pain that feels like a transient electric shock. Some histopathological studies have reported that trigeminal neuralgia is caused by mechanical compression of the demyelinated trigeminal nerve; the pathophysiological mechanism behind this phenomenon remains to be clarified, however. Cell-cell interactions have also been reported to be involved in the development and modulation of some types of neuropathic pain. The purpose of this study was to investigate the potential contribution of cell-cell interactions to trigeminal neuralgia by measuring intracellular free Ca²⁺ concentrations ([Ca²⁺]_i) in primary cultured trigeminal ganglion (TG) cells. Direct mechanical stimulation of TG cells induced an increase in [Ca²⁺]_i in both neuronal and non-neuronal cells, such as glial cells. Moreover, this increase was stimulus intensity-dependent and non-desensitizing. Direct mechanical stimulation increased [Ca²⁺]_i in neighboring cells as well, and this increase was inhibited by application of carbamazepine. These results indicate that direct mechanical stimulation affects Ca²⁺ signaling. Trigeminal ganglion cells establish intercellular networks between themselves, suggesting that this is involved in the development and generation of trigeminal neuralgia.