Ketamine's Effect Changes the Cortical Electrophysiological Activity Related to Semantic Affective Dimension of Pain

Ketamine is a unique anesthetic with neural effects that are distinct from more commonly-used γ-aminobutyric acid agonists. Evidence suggest that analgesic effect of ketamine is primarily related to the affective than the sensorial aspects of pain interpretation. The investigators investigated whether ketamine, a noncompetitive NMDA antagonist, would modify the perceived emotional valence of pain-related words when compared to non-pain-related ones in healthy volunteers. Using a single session double-blind parallel placebo-controlled design, 24 healthy volunteers were randomized to receive intravenous S-ketamine (n=12) or placebo (n=12). During infusion (plasmatic target of 60 ng/ml), the effects of ketamine were recorded using EEG and oddball behavioral data was monitored. Evoked potentials (N200 and P300 components) were recorded during performance of a semantic written word oddball task containing pain-related (targets) and non-pain-related words (standards). Expected results: The findings of this study can help in the understanding of neurophysiologic mechanisms involved in ketamine's effects both in psychiatric diseases as in the treatment of postoperative acute and chronic pain.

Inclusion criteria

• male healthy subjects with higher education level

Exclusion criteria

• do not understand Portuguese language
• obese patients (BMI > 27 kg/m2)
• use of NSAID, steroids, analgesics, anticonvulsant drugs, as well as alpha and beta-blockers
• score ≥ 13 on Beck II Questionnaire
• sleep deprivation in the night before evaluation