Effect of low power 655 nm diode laser irradiation on the neuromuscular junctions of the mouse diaphragm.

BACKGROUND AND OBJECTIVES Low level laser therapy (LLLT) in specific wavelengths and fluence maintains the electrophysiological activity of injured peripheral nerve in rats, preventing scar formation (at injury site) as well as degenerative changes in the corresponding motor neurons of the spinal cord, thus accelerating regeneration of the injured nerve. We studied the effect of LLLT on the neurotransmitter release in neuromuscular junctions of the mouse diaphragm. STUDY DESIGN/MATERIALS AND METHODS Thirty-nine diaphragm muscles were studied. LLLT with GaAlAs 655 nm (1-12 J/cm(2)) was used. Neurotransmitter release was studied by conventional intracellular recording techniques on curarised or high magnesium media. Quantal content, amplitude, latency and rise time were analysed for end-plate potentials (EPPs). Frequency and amplitude were evaluated for the miniature end-plate potentials (MEPPs). Short-term plasticity of the neurotransmitter release (fast facilitation) was also evaluated by paired pulse stimulation. RESULTS AND CONCLUSIONS This study showed that LLLT (655 nm) in these doses has no detectable physiological effect on the motor end-plate neurotransmitter release in mice.