A single mechanism driving both inactivation and adaptation in rapidly adapting currents of DRG neurons?

Rapidly adapting (RA) currents expressed in dorsal root ganglia somatosensory neurons reduce their amplitude in response to prolonged and/or repeated mechanical stimulation. Both inactivation of mechanotransducer channels and adaptation of the force acting on the channels have been suggested to independently decrease RA currents. However, these two mechanisms have similar kinetics and dependence on calcium and voltage. These experimental findings suggest that a single mechanism might underlie both. We constructed a simple Hodgkin-Huxley-type model with a single gating variable driving both inactivation and adaptation to test this hypothesis. Predictions of the model successfully describe key features of mechanical activation as well as inactivation, adaptation, and recovery. The model thus supports the possibility of a single mechanism driving inactivation and adaptation in RA currents. On its own, the model can be integrated into higher-order models of touch receptors because of its accurate simulation of RA currents.