Oral NAC inhibits nociceptive transmission in healthy volunteers. A: Laser-evoked potential (LEP) recordings during placebo and N-acetyl-cysteine (NAC) sessions in a representative subject. Black: pre-drug recordings. Grey: post-drug recordings. Each trace is the mean of 20 trials. Horizontal calibration: 100 ms; vertical calibration: 20 μV. B: Mean pre-drug (black) and post-drug (grey) values for N1, N2-P2 amplitude LEP components and laser pain ratings during placebo and NAC sessions. Whereas placebo was ineffective, NAC significantly reduced all LEP components and laser pain ratings. Values are means + S.E.M. of 10 determinations. *p < 0.02; **p < 0.01.