Physostigmine analgesia and somatosensory evoked responses in man

14 normal volunteers were given 0.5 mg physostigmine or saline placebo i.v. in a randomized double blind trial. Subjects were pretreated with 0.5 mg methscopolamine i.m. on both days. Pain ratings and average evoked responses were obtained to brief electrical stimuli administered to the forearm. Pain response criterion was significantly higher on physostigmine than on placebo. Average evoked response component P100 was significantly smaller on physostigmine than placebo, especially for higher intensity stimuli. These results are consistent with central cholinergic modulation of pain and arousal systems in man.