Figure 3. Pain-related chemosomatosensory-evoked potentials in a representative participant before (dotted lines) and after (bold lines) short-term intravenous administration of placebo, morphine, and M-6-G (recording position Cz). After administration of morphine, the amplitudes decreased and the latencies increased. In contrast, after administration of M-6-G (highest dosage C), pain-related potentials did not change compared with pretreatment potentials.