Linking Hypothermia and Altered Metabolism with TrkB Activation.

Many mechanisms have been proposed to explain acute antidepressant drug-induced activation of TrkB neurotrophin receptors, but several questions remain. In a series of pharmacological experiments, we observed that TrkB activation induced by antidepressants and several other drugs correlated with sedation, and most importantly, coinciding hypothermia. Untargeted metabolomics of pharmacologically dissimilar TrkB activating treatments revealed effects on shared bioenergetic targets involved in adenosine triphosphate (ATP) breakdown and synthesis, demonstrating a common perturbation in metabolic activity.

A wake-up call: Sleep physiology and related translational discrepancies in studies of rapid-acting antidepressants.

Depression is frequently associated with sleep problems, and clinical improvement often coincides with the normalization of sleep architecture and realignment of circadian rhythm. The effectiveness of treatments targeting sleep in depressed patients, such as sleep deprivation, further demonstrates the confluence of sleep and mood. Moreover, recent studies showing that the rapid-acting antidepressant ketamine influences processes related to sleep-wake neurobiology have led to novel hypotheses explaining rapid and sustained antidepressant effects.

Rapid-acting antidepressants and the regulation of TrkB neurotrophic signalling-Insights from ketamine, nitrous oxide, seizures and anaesthesia.

Increased glutamatergic neurotransmission and synaptic plasticity in the prefrontal cortex have been associated with the rapid antidepressant effects of ketamine. Activation of BDNF (brain-derived neurotrophic factor) receptor TrkB is considered a key molecular event for antidepressant-induced functional and structural synaptic plasticity. Several mechanisms have been proposed to underlie ketamine's effects on TrkB, but much remains unclear.

Encoding, Consolidation, and Renormalization in Depression: Synaptic Homeostasis, Plasticity, and Sleep Integrate Rapid Antidepressant Effects.

Recent studies have strived to find an association between rapid antidepressant effects and a specific subset of pharmacological targets and molecular pathways. Here, we propose a broader hypothesis of encoding, consolidation, and renormalization in depression (ENCORE-D), which suggests that, fundamentally, rapid and sustained antidepressant effects rely on intrinsic homeostatic mechanisms evoked as a response to the acute pharmacological or physiologic effects triggered by the treatment. We review evidence that supports the notion that various treatments with a rapid onset of action, such as ketamine, electroconvulsive therapy, and sleep deprivation, share the ability to acutely excite cortical networks, which increases synaptic potentiation, alters patterns of functional connectivity, and ameliorates depressive symptoms.

Ketamine-induced regulation of TrkB-GSK3β signaling is accompanied by slow EEG oscillations and sedation but is independent of hydroxynorketamine metabolites.

Subanesthetic rather than anesthetic doses are thought to bring the rapid antidepressant effects of the NMDAR (N-methyl-d-aspartate receptor) antagonist ketamine. Among molecular mechanisms, activation of BDNF receptor TrkB along with the inhibition of GSK3β (glycogen synthase kinase 3β) are considered as critical molecular level determinants for ketamine's antidepressant effects. Hydroxynorketamines (2R,6R)-HNK and (2S,6S)-HNK), non-anesthetic metabolites of ketamine, have been proposed to govern the therapeutic effects of ketamine through a mechanism not involving NMDARs.

Dyskinesia and brain-derived neurotrophic factor levels after long-term levodopa and nicotinic receptor agonist treatments in female mice with near-total unilateral dopaminergic denervation.

Background: The treatment of Parkinson's disease is often complicated by levodopa-induced dyskinesia (LID). Nicotinic acetylcholine receptor agonists can alleviate LID in animal models but may be less effective in conditions of severe dopaminergic denervation. While the mechanisms of LID remain incompletely understood, elevated corticostriatal levels of the brain-derived neurotrophic factor (BDNF) have been suggested to play a role.

Cortical Excitability and Activation of TrkB Signaling During Rebound Slow Oscillations Are Critical for Rapid Antidepressant Responses.

Rapid antidepressant effects of ketamine become most evident when its psychotomimetic effects subside, but the neurobiological basis of this "lag" remains unclear. Laughing gas (NO), another NMDA-R (N-methyl-D-aspartate receptor) blocker, has been reported to bring antidepressant effects rapidly upon drug discontinuation. We took advantage of the exceptional pharmacokinetic properties of NO to investigate EEG (electroencephalogram) alterations and molecular determinants of antidepressant actions during and immediately after NMDA-R blockade.

Isoflurane produces antidepressant effects and induces TrkB signaling in rodents.

A brief burst-suppressing isoflurane anesthesia has been shown to rapidly alleviate symptoms of depression in a subset of patients, but the neurobiological basis of these observations remains obscure. We show that a single isoflurane anesthesia produces antidepressant-like behavioural effects in the learned helplessness paradigm and regulates molecular events implicated in the mechanism of action of rapid-acting antidepressant ketamine: activation of brain-derived neurotrophic factor (BDNF) receptor TrkB, facilitation of mammalian target of rapamycin (mTOR) signaling pathway and inhibition of glycogen synthase kinase 3β (GSK3β). Moreover, isoflurane affected neuronal plasticity by facilitating long-term potentiation in the hippocampus.

Brief isoflurane anesthesia regulates striatal AKT-GSK3β signaling and ameliorates motor deficits in a rat model of early-stage Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder primarily affecting the nigrostriatal dopaminergic system. The link between heightened activity of glycogen synthase kinase 3β (GSK3β) and neurodegene-rative processes has encouraged investigation into the potential disease-modifying effects of novel GSK3β inhibitors in experimental models of PD. Therefore, the intriguing ability of several anesthetics to readily inhibit GSK3β within the cortex and hippocampus led us to investigate the effects of brief isoflurane anesthesia on striatal GSK3β signaling in naïve rats and in a rat model of early-stage PD.

Brief Isoflurane Anesthesia Produces Prominent Phosphoproteomic Changes in the Adult Mouse Hippocampus.

Anesthetics are widely used in medical practice and experimental research, yet the neurobiological basis governing their effects remains obscure. We have here used quantitative phosphoproteomics to investigate the protein phosphorylation changes produced by a 30 min isoflurane anesthesia in the adult mouse hippocampus. Altogether 318 phosphorylation alterations in total of 237 proteins between sham and isoflurane anesthesia were identified.