Ketamine's Antidepressant Mechanisms and Inflammatory Modulation
Summary
Ketamine has transformed the treatment landscape for depression through its rapid amelioration of symptoms, particularly in treatment-resistant cases. Beyond its well characterised antagonism of N-methyl-D-aspartate (NMDA) receptors and subsequent enhancement of glutamatergic neurotransmission, emerging evidence implicates modulation of immune and inflammatory pathways as integral to its antidepressant action. Ketamine exerts anti-inflammatory effects both centrally and peripherally, dampening pro-inflammatory cytokines such as interleukin-6 and tumour necrosis factor-α while upregulating anti-inflammatory mediators. These changes are accompanied by shifts in the kynurenine pathway of tryptophan metabolism, favouring neuroprotective over neurotoxic metabolites, and by alterations in microglial activation states. Concomitantly, ketamine boosts synaptic plasticity via increased brain-derived neurotrophic factor (BDNF) expression and related signalling cascades, restoring connectivity in mood-regulating circuits. Together, these intertwined processes underpin ketamine’s rapid onset of effect, durable clinical responses and potential for biomarker-guided treatment optimisation.
Research from Nature Portfolio
Studies in rodent models of neuropathic pain–induced depression have revealed that individuals displaying depression-like behaviours exhibit heightened pro-inflammatory cytokines in both serum and prefrontal cortex alongside reduced BDNF levels. A single sub-anaesthetic ketamine dose normalised the imbalance of pro- and anti-inflammatory cytokines and restored BDNF expression, correlating with rapid behavioural improvement. These findings highlight inflammation-driven neuroplastic deficits in comorbid pain and depression and position cytokines and BDNF as mechanistic mediators of ketamine’s antidepressant and analgesic actions.
Ketamine's Antidepressant Mechanisms and Inflammatory Modulation publication trend
The graph below shows the total number of articles in ketamine's antidepressant mechanisms and inflammatory modulation across all publications each year (not limited to Nature Index journals).
Technical terms
NMDA receptor: A subtype of glutamate receptor whose antagonism by ketamine enhances synaptic excitation and plasticity.
Cytokine: A signalling protein released by immune cells that modulates inflammation; includes interleukins and tumour necrosis factors.
Brain-derived neurotrophic factor (BDNF): A neurotrophin that supports neuronal survival, growth and synaptic plasticity, essential for mood regulation.
Kynurenine pathway: A metabolic cascade converting tryptophan into bioactive compounds, with certain metabolites promoting neurotoxicity or neuroprotection.
Microglia: Resident immune cells of the central nervous system that regulate inflammation and synaptic remodelling.
References
- Alterations in the inflammatory cytokines and brain-derived neurotrophic factor contribute to depression-like phenotype after spared nerve injury: improvement by ketamine. Scientific Reports (2017).
- Ketamine’s effect on inflammation and kynurenine pathway in depression: A systematic review. Journal of Psychopharmacology (2021).
- Plasma inflammatory cytokines and treatment-resistant depression with comorbid pain: improvement by ketamine. Journal of Neuroinflammation (2021).
- Depression treatment response to ketamine: sex-specific role of interleukin-8, but not other inflammatory markers. Translational Psychiatry (2021).
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