Imaging pain modulation by subanesthetic S-(+)-ketamine.

Area of Science:

• Neuroscience
• Anesthesiology
• Pain Management

Background:

• The cerebral processing of pain and the effects of low-dose ketamine remain incompletely understood.
• Subanesthetic doses of ketamine are increasingly explored for various therapeutic applications.

Purpose of the Study:

• To investigate the impact of subanesthetic intravenous S-(+)-ketamine doses on the perception and cerebral processing of experimental heat pain.
• To determine the dose-dependent effects of S-(+)-ketamine on pain perception and associated brain activity.

Main Methods:

• Healthy volunteers received experimental painful heat stimuli during placebo and increasing doses (0.05, 0.1, 0.15 mg x kg(-1) x h(-1)) of S-(+)-ketamine infusion.
• Functional magnetic resonance imaging (fMRI) was used to monitor brain activity.
• Pain intensity and unpleasantness were rated using a numerical rating scale; consciousness was assessed via questionnaire.

Main Results:

• Pain unpleasantness decreased significantly with increasing S-(+)-ketamine dosage (55.1% reduction at 0.15 mg x kg(-1) x h(-1) vs. placebo).
• Pain intensity also decreased (23.1% reduction) but to a lesser extent.
• Ketamine administration led to a dose-dependent reduction in pain-induced cerebral activation in areas including the thalamus, insula, cingulate cortex, and prefrontal cortex, notably the midcingulate cortex.

Conclusions:

• Subanesthetic S-(+)-ketamine effectively modulates the perception of pain, particularly its affective component, by reducing activity in key pain-processing brain regions.
• The findings highlight the potential of low-dose S-(+)-ketamine in managing pain through targeted modulation of neural pathways.