OBJECTIVETo investigate the effect of subanaesthetic dose of ketamine on mechanical stimulus on brain regions.

METHODSTotally 13 healthy male volunteers were enrolled in this study, in whom 0 and 100 ng/ml ketamine were administrated by target controlled infusion system in pilot study. After von Frey filaments (vFFs) 300 g were used as mechanical stimuli, Visual Analogue Scale scores were evaluated. Functional magnetic resonance imaging (fMRI)was taken 1 week after pilot study at the following sequences: structure imaging + functional imaging (stimulus sequence with 300 g vFFs, ketamine sequence); stimulus sequence = 6×(20s on + 20s off), with target concentration of ketamine at 0,100 ng/ml.fMRI result was processed by SPM2 and Metlab 7.01 software package.

RESULTSPosterior cerebellum lobe and corpus callosum were inhibited at 100 ng/ml under vFFs stimulus, whereas cingulate gyrus, middle frontal gyrus, inferior parietal lobule, occipital lobe, and posterior cerebellum lobe were activated at 100 ng/ml under vFFs stimulus.

CONCLUSIONSKetamine 100 ng/ml exerts its effect on pain related brain regions. It can both activate and inhibit these brain regions, with the activating effect being the primary effect.