Objectives: Low power diode Iaser (830 nm) irradiation is a useful analgesic tool in superficial pain. Pulse laser irradiation allows us to increase the laser power because the non-irradiation time reduces heating effects and/or direct tissue damage at the irradiation area. This new irradiation device using pulse laser was applied to the dorsal skin to investigate the effects on the micturition reflex in the rat by targeting underlying sacral spinal roots.
Methods: Vesical pressure measurement during the continuous infusion of the urinary bladder with saline, acetic acid (AA, 0.1%) or prostaglandin E2 (PGE2, 10−5 M) were performed in un-anesthetized rats. Multi-unit recording from bladder afferent nerves preformed under urethane anesthesia. Laser irradiation, either continuously at 1 W or in 10 W-pulse mode, was delivered at 830 nm from 1.5 cm above the skin at the lumbosacral joint.
Results: During continuous saline infusion to the urinary bladder, neither continuous (1 W) nor pulse (10 W) laser irradiation altered the intercontraction interval and nerve firing during distention of the bladder. Pulse laser, but not continuous laser irradiation, increased the intercontraction interval with AA or PGE2 infusion and diminished nerve firing during distention of the bladder with AA or PGE2 infusion.
Conclusion: These data indicate that pulse laser could diminish inflammation related nerve firing from the bladder. Since this laser irradiation did not affect the normal bladder distention elicited nerve firing, it appears capable of reducing urgency sensation without loss of the basic micturition reflex.