Sensing mechanisms of the low-power infrared radiation

Abstract

Mechanisms of interaction between low-power CO2-laser infrared (IR) radiation and sensory neuron were investigated. The primary event of this interaction is energy absorption by Na+,K+-ηTPase- bound ATP molecules. The subsequent transfer of vibrational energy from excited ATP molecules to Na+,K+-ηTPase activates the enzyme converting it to a signal transducer, which results in a decrease in Na v1.8 channels voltage sensitivity. The mechanism of interaction between non-Â-thermal, low-power IR radiation and nociceptive neuron membrane is suggested. It is governed by an extremely sensitive transducer-coupled decrease in effective charge transfer in the activation gating machinery of Nav1.8 channels. The Almers' method of effective charge transfer evaluation was shown to be adequate only for slow sodium channels, which have inactivation kinetics that are sufficiently slow. Another temperature-dependent mechanism of IR radiation interaction with sensory membrane is proposed due to an investigation of the behavior of Na v1.8 channels inactivation. The thermal effects were clearly detected, as the duration of the sodium current trace decreased after irradiation. This phenomenon is caused by acceleration of the inactivation process. Both fast and slow inactivation time constants significantly decreased after irradiation. The activation gating system of Nav1.8 channel can serve as a sensor of non-thermal radiation. This channel is also demonstrated to sense higher thermal energy by its inactivation gating machinery. The range between non-thermal and thermal thresholds is very narrow (the energies of ~200 to ~2,000 photons emitted by CO2-laser within our patch-clamp experimental setup). A fundamental existence of this range makes it possible to predict the analgesic effect of IR radiation in humans, since the excitability of nociceptive cutaneous afferents is decreased exclusively within these energy thresholds. Therefore, a novel medical device, a low-power CO2-laser for physiotherapy, was constructed. © 2013 Springer Science+Business Media Dordrecht.