Effect of Helium-Neon Laser on Fast Excitatory Postsynaptic Potential (f-EPSP) of Neurous in the Isolated Rat Superior Cervical Ganglia

摘要

Single electrical stimulation of the cervical sympathetic trunk elicits in the ganglion cells an excitatory postsynaptic potential (EPSP) or multiple EPSPs of varying latencies. Among of which a fast excitatory postsynaptic potential (f-EPSP) is the main type of ganglionic transmission in the sympathetic neurons, In previous work,we studied the effects of Helium-Neon laser with wavelength 632.8 nm on membrane conductance of neurons with stable f-EPSP in isolated rat superior cervical ganglia. The aim of this study is to further measure the effect of Helium-Neon Laser with wavelength 632.8 nm on fast excitatory postsynaptic potential of postganglionic neurons in the isolated rat superior cervical ganglia by means of intracellular recording techniques. The neurons with fast excitatory postsynaptic potential were irradiated by different power densities (1 and 5 mW/cm~2 ), pulse frequency of 1Hz laser. Irradiated by the 2 mW/cm~2 laser, the amplitude of the f-EPSP could augment (P<0.05) and even caused action potential (AP) at the end of the first 1～2 minute, the f-EPSP could descend and lasted for 3 ～8 minutes later. But the amplitude of the f-EPSP of neurons irradiated by the 5 mW/cm~2 laser could depress for the irradiating periods. That results appear to exist the second-order phases in the interaction of the Helium-Neon laser with neurons: first, the initial, short-time promotive effect; second, the late, long-time effect of inhibition.The mechanism of the effect of Helium-Neon laser on f-EPSP of postganglionic neurons may be the photobiology effects of low power laser.