Mechanical stimuli induce intracellular calcium response in a subpopulation of cultured rat sensory neurons.

Cultured dorsal root ganglion neurons from newborn rats were mechanically deformed with a fine-tipped glass capillary, and the change in the intracellular Ca2+ concentration ([Ca2+]i) was recorded by Fura-2-based microfluorimetry. The deformation evoked elevation in [Ca2+]i from 18.7 +/- 5.4 nM (mean +/- S.E.M., n = 35) to 137.1 +/- 15.2 nM in some subpopulations of cells, especially those larger than 20 microm in diameter. The largest mechanosensitive cell group was that of cells 20-25 microm in diameter; 56% of the mechanosensitive cells were of this cell size. All of the cells larger than 25 microm in diameter displayed the Ca2+ increase when prodded. The depletion of extracellular Ca2+ diminished the Ca2+ elevation. Verapamil and nickel, blockers of voltage-dependent Ca2+ channels, did not influence the Ca2+ response, whereas gadolinium, a relatively selective blocker of mechanosensitive channels, diminished the response. Na+-free conditions did not influence the response. We concluded that the mechanical stimulation induced a Ca2+ influx in large dorsal root ganglion neurons through mechanosensitive Ca2+-permeable channels.