Neuron excitability changes induced by low-power laser irradiation

The change in excitability induced by low-power laser was investigated for freshly dissociated rat hippocampal CA3 pyramidal neuron using the whole-cell patch clamp technique. The experimental results indicate that the activation potential of Na+ channel shifted towards a more negative potential, the peak amplitude of I-Na increased in a voltage-dependent and reversible manner, the steady-state activation curve and inactivation curve of I-Na were significantly shifted, the half-activation voltage and the half-inactivation voltage respectively changed from (- 44.14 +/- 5.28)mV to (- 56.55 +/- 6.14)mV(n = 8, P < 0.01) and from(- 69.02 +/- 10.31) mV to (- 56.60 +/- 8.97)mV(n = 8, P < 0.01) when the neuron was irradiated by low-power laser. Moreover, the irradiation reversibly lowered the resting potential and threshold potential, increased the amplitude of action potential, widened the repolarization duration, and slowed the firing frequency. The results suggest that low-power laser irradiation can change the characteristics of Na+ channel, further affect the depolarizing and firing of action potential, and finally be involved in adjusting the excitability of neurons.