Influence of gap junctions upon Ca²⁺ propagation from stimulated keratinocytes to DRG neurons

Epidermal cells, such as keratinocytes, are regarded as the first sensory cells to transmit nociception and mechanoreception to free nerve endings extended from the dorsal root ganglion (DRG). Previous studies suggested that this transmission occurs as Ca²⁺ propagation via ATP receptors. Conversely, the influence of gap junctions on this Ca²⁺ propagation is largely unknown. Thus, we examined the localization and the role of connexin 43 among keratinocytes and DRG neurons. We co-cultured keratinocytes and DRG neurons and investigated the effect of pharmacological blockade of gap junctions on Ca²⁺ propagation upon stimulation of a single keratinocyte. Immunocytochemical experiments showed that connexin 43 is localized between keratinocytes and between keratinocytes and DRG neurons. Octanol, a gap junction inhibitor, significantly suppressed the concentrical Ca²⁺ propagation. Therefore, we conclude that the Ca²⁺ propagation mechanism via gap junctions from stimulated keratinocytes to free nerve endings should be taken into account.