Nitrogen laser pulses (40μJ/pulse, 3Hz) were guided by optic fiber into left cerebral cortex of six rats. The laser evoked potentials(LEP) in right corresponding cortical area were averaged on line, then, the reduced nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), biopterin (BP) and pterin(PT) in six brain areas were simultaneously assayed by the reverse-phase high-performance liquid chromatography(HPLC). The results show that the increased amplitudes of N₂₀₀, P₃₀₀ could be related to the increased metabolism rate of brain energy and the decreased biosynthesis of bioactive substances.