Temperature-dependent Activation of Neurons by Continuous Near-infrared Laser

Abstract

Optical control of neuronal activity has a number of advantages over electrical methods and can be conveniently applied to intact individual neurons in vivo. In this study, we demonstrated an experimental approach in which a focused continuous near-infrared (CNI) laser beam was used to activate single rat hippocampal neurons by transiently elevating the local temperature. Reversible changes in the amplitude and kinetics of neuronal voltage-gated Na and K channel currents were recorded following irradiation with a single-mode 980 nm CNI-laser. Using single-channel recordings under controlled temperatures as a means of calibration, it was estimated that temperature at the neuron rose by 14°C in 500 ms. Computer simulation confirmed that small temperature changes of about 5°C were sufficient to produce significant changes in neuronal excitability. The method should be broadly applicable to studies of neuronal activity under physiological conditions, in particular studies of temperature-sensing neurons expressing thermoTRP channels.

Thermosensitive TRP channel pore turret is part of the temperature activation pathway

“…S3). Although the rate of temperature increase with this approach was much slower than that seen in infrared laser-based heating approaches (44,45) or the rapid solution-switching approach (46), it was sufficient to reach activation temperature in 1-2 seconds.…”

Heteromeric Heat-sensitive Transient Receptor Potential Channels Exhibit Distinct Temperature and Chemical Response

“…To characterize heat-induced activation kinetics, a rapid laser heating approach was used (25). Briefly, a 1443-nm laser diode (Fitel) with controllers (Thorlabs) was used to generate a continuous narrow laser beam.…”

“…We characterized the activation kinetics of the heteromeric channels. To ensure that the rate of temperature change was much faster than the rate of channel activation, we employed a laser heating method (25) to heat the patch pipette tip above 45°C in less than 30 ms. Recording from inside-out patches held at ϩ80 mV, we observed that the heteromeric channels and the homomers exhibit marked differences in the activation rate in response to heating (Fig. 7A).…”

Near-infrared stimulation on globus pallidus and subthalamus

“…The linearity found in both temperature increases and changes in firing rate by optical stimulation in our study supports the findings that neuronal modulations are due to the transient temperature increase and increased temperature in thermodynamic equilibrium induced by optical stimulation. 3,28 We were able to induce significant neuronal excitations and inhibitions in the subcortical structures using NIS at power of >20 mW. In addition, it was found that optical stimulation at a power of 20 mW led to a temperature increase of about 2°C.…”

“…Regarding the mechanism of neuronal activation changes by optical stimulation, Liang et al 28 reported the elevated local tissue temperature as a cause of changes in the activity of a single hippocampal The asterisks (*, **, and ****) indicate statistical significance at different levels (p < 0.05, p < 0.005, and p < 0.0001, respectively) comparing beforeduring, during-after, and before-after. Fig.…”