Differences between ketamine's short-term and long-term effects on brain circuitry in depression

Area of Science:

• Neuroscience
• Pharmacology
• Psychiatry

Background:

• Ketamine exhibits rapid antidepressant effects, but dissociative and therapeutic actions are difficult to distinguish.
• Understanding ketamine's distinct short-term and long-term effects is crucial for identifying imaging biomarkers.
• A genetic rat model with distinct cognitive states (NC and PC) was used to study depression and ketamine response.

Purpose of the Study:

• To differentiate between short-term and long-term responses to ketamine.
• To identify potential neuroimaging biomarkers for ketamine's antidepressant effects.
• To investigate ketamine's impact on brain network properties in a genetic model of depression.

Main Methods:

• Utilized a genetic rat model of depression (NC and PC strains).
• Administered S-ketamine or saline and acquired resting-state functional magnetic resonance imaging (rs-fMRI) data.
• Applied graph analysis to brain network properties at baseline, 30 minutes, and 48 hours post-injection.

Main Results:

• Acute S-ketamine administration induced rapid, strain-independent changes in brain networks related to cognition, emotion, and reward.
• These acute changes correlated with depressive behaviors and may explain dissociative and antidepressant properties.
• At 48 hours, S-ketamine showed strain-specific effects, normalizing connectivity in the habenula, thalamus, and hippocampus in depressed rats.

Conclusions:

• Ketamine's rapid antidepressant action involves widespread, acute brain network alterations.
• Long-term, strain-specific effects in depressed rats suggest normalization of circuits critical for cognitive flexibility.
• These findings provide insights into ketamine's distinct temporal actions and potential procognitive effects in depression, offering translational imaging correlates for preclinical research.