Effects of low level laser irradiation on properties of sodium channel in rat hippocampal neurons

Acutely isolated rat hippocampal CA3 pyramidal neurons were irradiated with a semiconductor laser for wavelength 670 nm and power 5 mW. And properties of voltage-gated Na+ channel were studied using the whole-cell patch clamp technique. The experiment revealed that activation voltage and peak voltage of Ne channel shifted towards more negative potentials in irradiating 5 min and the action of laser irradiation reached stabilization in 7 min. There was no effect on peak currents of Ne channel using laser irradiation. The peak current density of control group and irradiation group were (-383.51 +/- 26.93) pA/pF and (-368.36 +/- 33.14) pA/pF respectively (n=8, P > 0.05). -40 mV activated threshold potential and -30 mV peak potential for control group respectively dropped to -60 mV and -40 mV after irradiating 7 min. The half-activation voltage and the slope factor of the activation curves of Na+ channel were also changed by the laser's exposure. The former changed from (-42.091 +/- 1.537) mV to (54.971 +/- 1.846) mV (n = 8, P < 0.01) and the latter form (1.529 +/- 0.667) mV to (2.634 +/- 0.519) mV (n=8, P < 0.05). The results show that activation properties of Na+ channel are influenced by laser irradiating hippocampal neurons. Thus, depolarizing process of action potential is affected. And further physiological functions of neurons are altered as a result of low level laser irradiation.