Mechanosensitive whole-cell currents in cultured rat somatosensory neurons.

Mechanosensitive currents in cultured rat dorsal root ganglion (DRG) neurons were analyzed by whole-cell patch clamp experiments. A positive pressure applied through a patch electrode induced an inward current in neurons 20 microm or larger in diameter. Ca(2+)- and Na(+)-depletion experiments revealed two kinds of channels involved in the mechanotransduction. One type of cells (type A) displayed blockade of the inward current in the absence of external Ca(2+); namely, the positive pressure of 10 cmH(2)O induced an inward current of 0.45+/-0.14 nA (mean+/-S.D., n=6) in the normal medium, and 0.08+/-0.07 nA (n=6) in the Ca(2+)-free solution. The current was influenced only a little by the depletion of external Na(+) in type A; the positive pressure induced an inward current of 0.48+/-0.04 nA (n=6) in the normal medium, and 0.39+/-0.06 nA (n=6) in the Na(+)-free solution. In the other type of cells (type B), the current persisted in the absence of Ca(2+); 0.52+/-0.09 nA (n=6) in the normal medium, and 0.35+/-0.09 nA (n=6) in the Ca(2+)-free solution. This type displayed a significant decrease in the inward current in the absence of Na(+); 0.42+/-0.09 nA (n=6) in the normal medium, and 0.23+/-0.08 nA (n=6) in the Na(+)-free solution. We concluded that there are two types of mechanosensitive channels in cultured DRG neurons, a Ca(2+)-selective channel and a non-selective cation channel.