Astrocytes in rapid ketamine antidepressant action

Ketamine, a general anaesthetic and psychotomimetic drug, exerts rapid, potent and long-lasting antidepressant effect, albeit the cellular and molecular mechanisms of this action are yet to be discovered. Besides targeting neuronal NMDARs fundamental for synaptic transmission, ketamine affects the function of astroglia the key homeostatic cells of the central nervous system that contribute to pathophysiology of psychiatric diseases including depression. Here we review studies revealing that (sub)anaesthetic doses of ketamine elevate intracellular cAMP concentration ([cAMP]_i) in astrocytes, attenuate stimulus-evoked astrocyte calcium signalling, which regulates exocytotic secretion of gliosignalling molecules, and stabilize the vesicle fusion pore in a narrow configuration possibly hindering cargo discharge or vesicle recycling. Next we discuss how ketamine affects astroglial capacity to control extracellular K⁺ by reducing cytoplasmic mobility of vesicles delivering the inward rectifying potassium channel (Kir4.1) to the plasmalemma. Modified astroglial K⁺ buffering impacts upon neuronal excitability as demonstrated in the lateral habenula rat model of depression. Finally, we highlight the recent discovery that ketamine rapidly redistributes cholesterol in the plasmalemma of astrocytes, but not in fibroblasts nor in neuronal cells. This alteration of membrane structure may modulate a host of processes that synergistically contribute to ketamine's rapid and prominent antidepressant action.

mGlu2/3 receptor as a novel target for rapid acting antidepressants

Given that ketamine, a noncompetitive N-methyl-d-aspartate receptor antagonist that exerts rapid antidepressant effects in patients with treatment-resistant depression, also has undesirable adverse effects, agents that can be used as alternatives to ketamine have been actively pursued. Group II metabotropic glutamate (mGlu) receptors, consisting of mGlu2 and mGlu3 receptors, have emerged as one of the most promising targets in the development of ketamine-like antidepressants. Indeed, mGlu2/3 receptor antagonists have been demonstrated to exert rapid antidepressant effects in animal models and to be efficacious in animal models refractory to conventional antidepressants. Moreover, there are striking similarities between mGlu2/3 receptor antagonists and ketamine in terms of not only their antidepressant profiles, but also the underlying mechanisms of their antidepressant effects. Nonetheless, studies in rodents have shown that mGlu2/3 receptor antagonists do not cause ketamine-like adverse events, such as psychotomimetic-like behavior, abuse potential or neurotoxicity, supporting the usefulness of mGlu2/3 receptor antagonists as alternatives to ketamine. In this chapter, the past and recent research on the antidepressant effects of mGlu2/3 receptor antagonists will be reviewed. In particular, the potential of mGlu2/3 receptor antagonists as novel ketamine-like antidepressants will be emphasized.

Anesthesia and Preconditioning Induced Changes in Mouse Brain [18F] FDG Uptake and Kinetics

PURPOSE

2-Deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) has been widely used for imaging brain metabolism. Tracer injection in anesthetized animals is a prerequisite for performing dynamic positron emission tomography (PET) scanning. Since preconditioning, as well as anesthesia, has been described to potentially influence brain [¹⁸F] FDG levels, this study evaluated how these variables globally and regionally affect both [¹⁸F] FDG uptake and kinetics in murine brain.

PROCEDURES

Sixty-minute dynamic [¹⁸F] FDG PET scans were performed in adult male C57BL/6 mice anesthetized with isoflurane [control (in 100 % O₂), in medical air, in 100 % O₂ + insulin pre-treatment, and in 100 % O₂ after 18 h fasting], ketamine/xylazine, sevoflurane, and chloral hydrate. An additional group was scanned after awake uptake. Blood glucose levels were determined, and data was analyzed by comparing percent injected dose per cc tissue (%ID/cc) and glucose influx rate and metabolic rate (MRGlu) calculated by Patlak plot.

RESULTS

Ketamine/xylazine and chloral hydrate anesthesia induced a lower whole-brain uptake of [¹⁸F] FDG (2.86 ± 0.67 %ID/cc, p < 0.001; 4.25 ± 0.28 %ID/cc, p = 0.0179, respectively) compared to isoflurane anesthesia (5.04 ± 0.19 %ID/cc). In addition, protocols affected differently distribution of [¹⁸F] FDG uptake in brain regions. Ketamine/xylazine reduced [¹⁸F] FDG influx rate in murine brain (0.0135 ± 0.0009 vs 0.0247 ± 0.0014 ml/g/min; p < 0.005) and chloral hydrate increased MRGlu (66.72 ± 3.75 vs 41.55 ± 3.06 μmol/min/100 ml; p < 0.01) compared to isoflurane. Insulin-pretreated animals showed a higher influx rate (0.0477 ± 0.0101 ml/min/g; p < 0.05) but a reduced MRGlu (21.92 ± 3.12 μmol/min/100 ml; p < 0.01). Blood glucose levels were negatively correlated to [¹⁸F] FDG uptake and influx rate, but positively correlated to MRGlu.

CONCLUSIONS

Choice of anesthesia and pre-conditioning affect not only [¹⁸F] FDG uptake but also kinetics and regional distribution in the mouse brain. Both anesthesia and pre-conditioning should be carefully considered in the interpretation of [¹⁸F] FDG studies due to its great influence on the uptake and distribution of the tracer along the brain regions.

Chronic stress pathology and ketamine-induced alterations in functional connectivity in major depressive disorder: An abridged review of the clinical evidence

A paradigm shift in the conceptualization of the neurobiology of depression and the serendipitous discovery of ketamine's rapid-acting antidepressant (RAAD) effects has ushered in a new era of innovative research and novel drug development. Since the initial discovery of ketamine's RAAD effects, multiple studies have supported its short-term efficacy for fast-tracked improvements in treatment-resistant depression. Evidence from MRI studies have repeatedly demonstrated functional connectivity alterations in stress- and trauma-related disorders suggesting this may be a viable biomarker of chronic stress pathology (CSP). Human mechanistic studies further support this by coupling functional connectivity to ketamine's RAAD effects including connectivity to glutamate neurotransmission, ketamine to normalized connectivity, and these advantageous normalizations to symptom improvement/ketamine response. This review provides an abridged discussion of the suspected neurobiological underpinnings of ketamine's RAAD effects, highlighting ketamine-induced alterations in prefrontal, striatal, and anterior cingulate cortex functional connectivity in major depressive disorder. We present a model of CSP underscoring the role of synaptic loss and dysconnectivity and discuss how ketamine may be used both as (1) a treatment to restore and normalize these stress-induced neural alterations and (2) a tool to study potential biomarkers of CSP and treatment response. We conclude by noting challenges and future directions including heterogeneity, sex differences, the role of early life stress, and the need for proliferation of new methods, paradigms, and tools that will optimize signal and allow analyses at different levels of complexity, according to the needs of the question at hand, perhaps by thinking hierarchically about both clinical and biological phenotypes.

Ketamine and rapid acting antidepressants: Are we ready to cure, rather than treat depression?

Depression is a leading cause of disability, with often chronic course of illness and high treatment resistance in a large proportion of patients. In the current short perspective paper, we present evidence supporting the presence of synaptic-based chronic stress pathology (CSP) in depression and across a number of psychiatric disorders. We summarize the synaptic connectivity model of CSP, and briefly review related preclinical and clinical evidence, while providing appropriate references for more comprehensive reviews and alternative models. We then underscore some gaps in the literature and provide various tips for future directions.

Ketamine's dose related multiple mechanisms of actions: Dissociative anesthetic to rapid antidepressant

Ketamine induces safe and effective anesthesia and displays unusual cataleptic properties that gave rise to the term dissociative anesthesia. Since 1970, clinicians only utilized the drug as an anesthetic or analgesic for decades, but ketamine was found to have rapid acting antidepressant effects in 1990s. Accumulated evidence exhibits NMDAR antagonism may not be the only mechanism of ketamine. The contributions of AMPA receptor, mTor signal pathway, monoaminergic system, sigma-1 receptor, cholinergic, opioid and cannabinoid systems, as well as voltage-gated calcium channels and hyperpolarization cyclic nucleotide gated channels are discussed for the antidepressant effects. Also the effects of ketamine's enantiomers and metabolites are reviewed. Furthermore ketamine's anesthetic and analgesic mechanisms are briefly revisited. Overall, pharmacology of ketamine, its enantiomers and metabolites is very unique. Insight into multiple mechanisms of action will provide further development and desirable clinical effects of ketamine.

Propofol versus placebo (with rescue with ketamine) before less invasive surfactant administration: study protocol for a multicenter, double-blind, placebo controlled trial (PROLISA)

Background

One major limitation for less invasive surfactant administration (LISA) is the difficulty in providing sedation before this procedure and the competitive risk of respiratory depression versus avoidance of intubation for most sedative or analgesic drugs used in this context.

The objective of this study is to compare the need for mechanical ventilation within 72 h of life following premedication with propofol, versus placebo (rescue with ketamine), for the LISA procedure in preterm neonates born before 32 weeks gestational age (wGA).

Methods

ProLISA is a phase III, non-inferiority, multicenter, double blind, randomized, placebo controlled trial designed according to the SPIRIT Statement. Neonates born before 32 wGA in 12 geographically dispersed Neonatal Intensive Care Units in France needing surfactant will be included from September 2019 to September 2022. A sample of 542 patients is needed. The neonate is randomized to the intervention (propofol) or control placebo group. Open label rescue treatment with ketamine is possible in both groups if FANS (Faceless Acute Neonatal pain Scale) is ≥6. To guide drug administration, FANS is scored before attempting laryngoscopy. Once an adequate score has been obtained, LISA is performed according to a standardized protocol. The primary outcome is the need for mechanical ventilation within 72 h of life. Secondary outcomes are tolerance of the procedure, pain evaluation, hemodynamic and neurologic parameters after the intervention, morbidities before discharge and neurodevelopmental assessment at 2 years of age.

Discussion

This paper describes the first multicenter, double-blind, randomized, placebo-controlled trial on this topic and will provide crucial information to support implementation of the LISA procedure.

Trial registration

ClinicalTrials.gov: NCT04016246. Registered 06 June 2019, N°EUDRACT: 2018–002876-41.

Protective effect of oleuropein on ketamine-induced cardiotoxicity in rats

The antioxidant and cardioprotective effects of oleuropein have been reported in several studies; however, its effect on ketamine cardiotoxicity has not been known yet. The aim of this study was to investigate the effects of oleuropein in ketamine-induced cardiotoxicity model in rats. A total of 28 male Wistar Albino rats were included in the study and they were randomly divided into four groups, each having seven rats. Group 1 (control): rats were given 1 mL of DMSO by oral gavage method for 7 days. Group 2 (ketamine): on the seventh day of the study, 60 mg/kg ketamine was administered intraperitoneally. Then, 60 mg/kg ketamine was administered intraperitoneally every 10 min for 3 h. Group 3 (oleuropein): rats were given 200 mg/kg/day oleuropein by oral gavage method for 7 days. Group 4 (oleuropein + ketamine): rats were given 1 × 200 mg/kg oleuropein by oral gavage method for 7 days. Furthermore, 60 mg/kg ketamine was administered intraperitoneally on the seventh day of the experiment. Then, 60 mg/kg ketamine was administered intraperitoneally every 10 min for 3 h. Serum cardiac marker (TnI, CK-MB and CK) levels were measured. Histopathological analysis was performed on a portion of the cardiac tissue. Cardiac tissue oxidative stress and antioxidant markers (MDA, GSH, GSH.Px and CAT), TNF-α, IL-6, NF-κB, COX-2 and Nrf-2 gene expressions, and protein conversion levels of related genes were determined. Data obtained showed that ketamine administration increased MDA (p < 0.001), TNF-α (p < 0.01), IL-6 (p < 0.01), COX-2 (p < 0.001) and NF-κB (p < 0.001) levels, as well as serum TnI (p < 0.001), CK-MB (p < 0.001) and CK (p < 0.01) levels whereas decreased GSH (p < 0.05) and Nrf-2 (p < 0.05) levels, as well as GSH-Px (p < 0.001) and CAT (p < 0.05) enzyme activities. Oleuropein administration was observed to decrease MDA, TNF-α, IL-6, COX-2, NF-κB, TnI, CK-MB and CK levels close to the control group and to increase GSH levels and GSH-Px and CAT enzyme activities close to the control group. This study showed that oleuropein administration reversed the increased oxidative stress and inflammation as a result of the use of ketamine and had protective effects on the heart.

Ketamine plus propofol-electroconvulsive therapy (ECT) transiently improves the antidepressant effects and the associated brain functional alterations in patients with propofol-ECT-resistant depression

New methods for using ketamine in patients with propofol-electroconvulsive therapy-resistant depression (ECT-RD) are needed in the clinic. This study aimed to investigate the therapeutic efficacy of ketamine plus ECT in ECT-RD patients, along with the treatment-induced brain alterations. A total of 28 ECT-RD patients were intravenously injected with ketamine six times and treated with propofol-ECT six times alternately within two weeks. The Hamilton Depression Scale was used to assess the treatment effect. Global functional connectivity density (gFCD) and functional connectivity strength (FCS) were used to evaluate functional brain alterations. As compared with the propofol-ECT treatment group, the addition of ketamine could improve the therapeutic outcomes in patients with ECT-RD. The treatment increased gFCD in the left temporal and subgenual anterior cingulated cortex. Simultaneously, the treatment decreased FCS within the default mode network. Although increased functional connectivity could be sustained for 10 days, the clinical effect was only sustained 7 days, indicating that the clinical effect and functional brain alterations were disjointed. Ketamine plus propofol-ECT can obviously improve the effects of propofol-ECT in ECT-RD patients. However, the effect is limited in 7 days, suggesting the benefit is short-term.

A revised excretion factor for estimating ketamine consumption by wastewater-based epidemiology - Utilising wastewater and seizure data

The rate of drug excretion (excretion factor) is a critical parameter for monitoring drug consumption in the population by wastewater-based epidemiology (WBE). Previous studies have refined excretion factors for common illicit drugs, such as cocaine, amphetamine, methamphetamine, heroin, to improve the accuracy and reduce uncertainty in back-calculating consumption. Nevertheless, for ketamine, one of the most prevalent psychoactive substances, a careful review of its excretion factors has not been performed due to limited pharmacokinetic data. Here we review WBE studies and seizure data to refine and validate the excretion factors for ketamine and norketamine. The average ketamine/norketamine ratio in wastewater (5.36) was much higher than that found in urine (0.64), which means that the excretion factors derived only from pharmacokinetics data are not appropriate. Based on the comparison of the ratio between estimated consumptions of ketamine and methamphetamine by WBE with their corresponding ratio in official seizure data, a revised WBE excretion factor of 20% was proposed for ketamine following this review and applied to estimate the ketamine consumption in China. The revised estimates of ketamine consumption corresponded well with drug statistics. This suggests that the revised ketamine excretion factor is appropriate for estimating ketamine consumption by WBE. Systematic review of WBE studies is a suitable approach to refine the excretion factors for substances with inadequate pharmacokinetic data.

Performance and toxicity of different absorption enhancers used in the preparation of Poloxamer thermosensitive in situ gels for ketamine nasal administration

The purpose of this study was to investigate the nasal absorption rate and nasal mucosal toxicity of thermosensitive ketamine in situ gels containing various absorption enhancers. The optimal composition ratio for the gel matrix was determined to be 17.2% Poloxamer 407 and 2% Poloxamer 188, as this combination resulted in solutions with a gelation point within the range found in the nasal cavity. Ketamine gels containing the tested enhancers, namely, ethylenediaminetetraacetic acid disodium salt, hydroxypropyl-β-cyclodextrin, propylene glycol, or Tween-80, were compared with enhancer-free counterparts to determine the absorption of the drug, in vivo by measuring its plasma levels in rats and in vitro using a Franz diffusion cell. Moreover, the toxicity of each gel type was assessed by microscopic observation of the morphology of rat nasal mucosa as well as by determining the mobility of the mucosal cilia using an established toad model. The results showed that gels containing hydroxypropyl-β-cyclodextrin could promote the absorption of ketamine without added toxicity compared to enhancer-free gels. Thus, we consider hydroxypropyl-β-cyclodextrin as the most promising absorption enhancer for the nasal administration of ketamine using in situ gels.

Transient amnesia following prehospital low-dose ketamine administration

Low doses of ketamine have been shown to be safe and effective for pain relief. Adverse effects are generally mild and transient. A 69-year-old woman suffered a witnessed ground-level fall without report of head injury, loss of consciousness, or intoxication. She was in severe pain despite 10 mg of intravenous morphine and paramedics provided intravenous ketamine 16 mg (0.19 mg/kg). Upon arrival to the ED, she was alert and oriented. An X-ray demonstrated an acute comminuted nondisplaced right humeral head and neck fracture. Her pain improved after an additional 4 mg of morphine and placement of a sling. Prior to discharge, the patient developed confusion, difficulty finding words, amnesia to the event, and anterograde amnesia evidenced by repetitive questioning. A head CT and a CT angiogram of the patient's head and neck demonstrated no acute abnormalities and an EEG demonstrated no epileptiform activity. The patient was admitted for observation and her mental status gradually improved overnight. She was discharged the following morning. Low dose ketamine is an important therapeutic option. Delayed or prolonged neuropsychiatric effects may be possible following combined ketamine and opioid analgesia. Clinicians utilizing low dose ketamine should be aware of this potential complication as it could result in the need for additional diagnostic testing and prolonged length of stay.

Toxicological screening in the Amsterdam acute setting becomes more relevant if the standard panel of the drugs-of-abuse point-of-care test is expanded with GHB and ketamine

Objective

For diagnosis and treatment in the acute setting, it is crucial to know whether the clinical status of patients might be explained by the effects of drugs.The objective of this study was to determine how many drugs were detected by comprehensive toxicological screening, that could not be detected with a routine drugs-of-abuse point-of-care test (DOA-POCT) and which drugs of abuse (DOA) were relevant. A secondary objective was to determine in how many patients comprehensive toxicological screening provided additional clinically relevant information.

Methods

In this prospective study, patients were included in whom a DOA-POCT was performed and residual urine and serum samples were available.DOA-POCT were performed using the Triage® TOX Drug Screen. Comprehensive toxicological screening was performed using 1) the Toxtyper™ LC-MS^N method and 2) two GC-FID methods for alcohols and GHB respectively.The clinical relevance of the comprehensive toxicological screening results regarding diagnosis and patient management was quantified.

Results

A total of 100 patients were included. In 91 of these patients, comprehensive toxicological screening identified 234 drugs that were not identified by DOA-POCT. However, DOA-POCT identified 34 DOA that were not identified by comprehensive toxicological screening.Seven percent of comprehensive toxicological screening results were found to be clinically relevant, all with regard to diagnosis. GHB and ketamine were the drugs involved. Another 38 % strengthened confidence in diagnosis and patient care decisions.

Conclusion

GHB and ketamine should be added to the panel of drugs we screen at the point of care in the Amsterdam acute setting.

Simultaneous EEG/fMRI recorded during ketamine infusion in patients with major depressive disorder

A single subanaesthetic dose of ketamine rapidly alleviates the symptoms of major depressive disorder (MDD). However, few studies have investigated the acute effects of ketamine on the BOLD pharmacological magnetic resonance imaging (phMRI) response and EEG spectra. In a randomised, double-blind, active placebo-controlled crossover trial, resting-state simultaneous EEG/fMRI was collected during infusion of ketamine or active placebo (remifentanil) in 30 participants with MDD. Montgomery-Asberg depression rating scale scores showed a significant antidepressant effect of ketamine compared to placebo (69% response rate). phMRI analyses showed BOLD signal increases in the anterior cingulate and medial prefrontal cortices and sensitivity of the decrease in subgenual anterior cingulate cortex (sgACC) BOLD signal to noise correction. EEG spectral analysis showed increased theta, high beta, low and high gamma power, and decreased delta, alpha, and low beta power with differing time-courses. Low beta and high gamma power time courses explained significant variance in the BOLD signal. Interestingly, the variance explained by high gamma power was significantly associated with non-response to ketamine, but significant associations were not found for other neurophysiological markers when noise correction was implemented. The results suggest that the decrease in sgACC BOLD signal is potentially noise and unrelated to ketamine's antidepressant effect, highlighting the importance of noise correction and multiple temporal regressors for phMRI analyses. The lack of effects significantly associated with antidepressant response suggests the phMRI methodology employed was unable to detect such effects, the effect sizes are relatively small, or that other processes, e.g. neural plasticity, underlie ketamine's antidepressant effect.

Effect of ketamine on the NeuroSENSE WAVCNS during propofol anesthesia; a randomized feasibility trial

Dose-dependent effects of ketamine on processed electroencephalographic depth-of-hypnosis indices have been reported. Limited data are available for the NeuroSENSE WAV_CNS index. Our aim was to establish the feasibility of closed-loop propofol-remifentanil anesthesia guided by the WAV_CNS index in the presence of an analgesic dose of ketamine. Thirty ASA I-II adults, 18-54 years, requiring general anesthesia for anterior cruciate ligament surgery were randomized to receive: full-dose [ketamine, 0.5 mg kg^-1 initial bolus, 10 mcg kg^-1 min^-1 infusion] (recommended dose for postoperative pain management); half-dose [ketamine, 0.25 mg kg^-1 bolus, 5 mcg kg^-1 min^-1 infusion]; or control [no ketamine]. After the ketamine bolus, patients received 1.0 mcg kg^-1 remifentanil over 30 s, then 1.5 mg kg^-1 propofol over 30 s, followed by manually-adjusted propofol-remifentanil anesthesia. The WAV_CNS was > 60 for 7/9 patients in the full-dose group at 7 min after starting the propofol infusion. This was inconsistent with clinical observations of depth-of-hypnosis and significantly higher than control (median difference [MD] 17.0, 95% confidence interval [CI] 11.4-26.8). WAV_CNS was median [interquartile range] 49.3 [42.2-62.6] in the half-dose group, and not different to control (MD 5.1, 95% CI - 4.9 to 17.9). During maintenance of anesthesia, the WAV_CNS was higher in the full-dose group compared to control (MD 14.7, 95% CI 10.2-19.2) and in the half-dose group compared to control (MD 11.4, 95% CI 4.7-20.4). The full-dose of ketamine recommended for postoperative pain management had a significant effect on the WAV_CNS. This effect should be considered when using the WAV_CNS to guide propofol-remifentanil dosing.Trial Registration ClinicalTrails.gov No. NCT02908945.

Efficacy of single and repeated administration of ketamine in unipolar and bipolar depression: a meta-analysis of randomized clinical trials

BACKGROUND

Due to unmet clinical needs for efficient drugs with a rapid onset of antidepressant effects, we aimed to evaluate the efficacy of single-dose ketamine in different subgroups of patients with major depression and establish whether repeated ketamine administration could be a viable strategy to maintain treatment gains.

METHODS

Electronic databases (Medline via PubMed, Embase, Cochrane Library, Trip Database) were systematically searched until February 22, 2019, for published peer-reviewed randomized controlled trials (RCTs) concerning a single and repeated administration of ketamine in patients with major depression. All relevant RCTs were selected and critically appraised, and a meta-analysis of eligible studies was performed.

RESULTS

A total of 20 studies were included in the meta-analysis. The largest effect of ketamine vs. controls in reducing depressive symptoms was observed at 24 h (SMD = - 0.89; 95% CI - 1.24; - 0.53; p < 0.00001); however, a significant difference was shown for up to 7 days after a single dose. Significant differences compared with controls were observed for up to 7 days in treatment-resistant patients and when ketamine was added to ongoing antidepressant treatment, while there were no significant differences at 7 days when ketamine was used as monotherapy. In patients with major depression, initial antidepressant effects of ketamine were maintained during repeated dosing. At 2-3 weeks of repeated ketamine treatment, significant reduction of depression severity scores was observed: SMD = - 0.70; 95% CI - 1.15; - 0.25 or SMD = - 0.81; 95% CI - 1.41; - 0.20 (depending on the dosing regimen used); p ≤ 0.009 vs placebo.

CONCLUSIONS

Our meta-analysis revealed rapid and robust antidepressant effects of single-dose ketamine in patients with treatment-resistant depression (TRD). By pooling data from RCTs, we showed for the first time that repeated ketamine administration is effective in sustaining initial antidepressant effects observed after single dosing.

The Thalamocortical Circuit of Auditory Mismatch Negativity

BACKGROUND

Mismatch negativity (MMN) is an extensively validated biomarker of cognitive function across both normative and clinical populations and has previously been localized to supratemporal auditory cortex. MMN is thought to represent a comparison of the features of the present stimulus versus a mnemonic template formed by the prior stimuli.

METHODS

We used concurrent thalamic and primary auditory cortical (A1) laminar recordings in 7 macaques to evaluate the relative contributions of core (lemniscal) and matrix (nonlemniscal) thalamic afferents to MMN generation.

RESULTS

We demonstrated that deviance-related activity is observed mainly in matrix regions of auditory thalamus, MMN generators are most prominent in layer 1 of cortex as opposed to sensory responses that activate layer 4 first and sequentially all cortical layers, and MMN is elicited independent of the frequency tuning of A1 neuronal ensembles. Consistent with prior reports, MMN-related thalamocortical activity was strongly inhibited by ketamine.

CONCLUSIONS

Taken together, our results demonstrate distinct matrix versus core thalamocortical circuitry underlying the generation of a higher-order brain response (MMN) versus sensory responses.

Comparison of the Ketamine-Lidocaine and Fentanyl-Lidocaine in Postoperative Analgesia in Axillary Block in Upper Limb Fractures By Ultrasound Guidance

Background

Regional anesthesia provides safe anesthesia for upper extremity surgery. Axillary plexus block approach for hand and forearm surgery is commonly used. The use of adjuvants in combination with local anesthetics for peripheral nerve blocks enhances the quality and duration of anesthesia and postoperative analgesia.

Methods

This double-blind clinical trial was performed on 60 patients who were candidates for the surgery of upper extremity fractures with ASA I and II classes. The patients were randomly divided into two equal groups (n = 30). The intervention group 1 received 4 mg/kg lidocaine 1% and 50 µg fentanyl and the intervention group 2 received 4 mg/kg lidocaine 1% and 30 mg ketamine during the axillary block. After the necessary monitoring, a pinprick test was performed to evaluate sensory block, and a three-point scale test for the motor block was performed for median, ulnar, radial and musculocutaneous nerves. The duration of postoperative analgesia, the time of the first request for a painkiller, and the amount of opioid received were compared in the two groups.

Results

Onset of sensory and motor block was shorter in the fentanyl group but did not differ significantly. The sensory and motor block length was slightly higher in the fentanyl group, but no significant difference was observed. The severity of pain (VAS) and the mean of received opioid (pethidine) were significantly lower in the fentanyl group 24 hours after the surgery (P < 0.0001). The duration of postoperative analgesia and the time of the first request for painkiller were longer in the fentanyl group, but there was no significant difference.

Conclusions

The severity of pain and analgesic intake in the fentanyl group decreased significantly. Therefore, fentanyl is a better drug than ketamine for using as an adjuvant in the axillary block.

Postnatal functional inactivation of the ventral subiculum enhances dopaminergic responses in the core part of the nucleus accumbens following ketamine injection in adult rats

For almost two decades schizophrenia has been considered to be a functional disconnection disorder. This functional disconnectivity between several brain regions could have a neurodevelopmental origin. Various approaches suggest the ventral subiculum (SUB) is a particular target region for neurodevelopemental disturbances in schizophrenia. It is also commonly acknowledged that there is a striatal dopaminergic (DA) dysregulation in schizophrenia which may depend on a subiculo-striatal disconnection involving glutamatergic NMDA receptors. The present study was designed to investigate, in adult rats, the effects of the non-competitive NMDA receptor antagonist ketamine on DA responses in the ventral striatum, or, more specifically, the core part of the nucleus accumbens (Nacc), following postnatal functional inactivation of the SUB. Functional inactivation of the left SUB was carried out by local tetrodotoxin (TTX) microinjection at postnatal day 8 (PND8), i.e. at a critical point in the neurodevelopmental period. DA variations were recorded using in vivo voltammetry in freely moving adult rats (11 weeks). Locomotor activity was recorded simultaneously with the extracellular levels of DA in the core part of the Nacc. Data obtained during the present study showed that after administration of ketamine, the two indexes were higher in TTX animals than PBS animals, the suggestion being that animals microinjected with TTX in the left SUB at PND8 present greater reactivity to ketamine than animals microinjected with PBS. These findings could provide new information regarding the involvement of NMDA glutamatergic receptors in the core part of the Nacc in the pathophysiology of schizophrenia.

Ketamine: The final frontier or another depressing end?

Two decades ago, the observation of a rapid and sustained antidepressant response after ketamine administration provided an exciting new avenue in the search for more effective therapeutics for the treatment of clinical depression. Research elucidating the mechanism(s) underlying ketamine's antidepressant properties has led to the development of several hypotheses, including that of disinhibition of excitatory glutamate neurons via blockade of N-methyl-d-aspartate (NMDA) receptors. Although the prominent understanding has been that ketamine's mode of action is mediated solely via the NMDA receptor, this view has been challenged by reports implicating other glutamate receptors such as AMPA, and other neurotransmitter systems such as serotonin and opioids in the antidepressant response. The recent approval of esketamine (Spravato™) for the treatment of depression has sparked a resurgence of interest for a deeper understanding of the mechanism(s) underlying ketamine's actions and safe therapeutic use. This review aims to present our current knowledge on both NMDA and non-NMDA mechanisms implicated in ketamine's response, and addresses the controversy surrounding the antidepressant role and potency of its stereoisomers and metabolites. There is much that remains to be known about our understanding of ketamine's antidepressant properties; and although the arrival of esketamine has been received with great enthusiasm, it is now more important than ever that its mechanisms of action be fully delineated, and both the short- and long-term neurobiological/functional consequences of its treatment be thoroughly characterized.

[Effectiveness of ketamine in the treatment of refractory and super-refractory status epilepticus in children]

Objective: To investigate the effectiveness of ketamine in the treatment of refractory status epilepticus (RSE) and super refractory status epilepticus (SRSE) in children. Methods: A retrospective study was conducted to collect and analyze the medical data of 18 children with RSE or SRSE who received ketamine in intensive care unit of Beijing Children's Hospital from January 2016 to December 2018. According to the different regimen of ketamine, all children were divided into the loading-maintenance group (7 cases) and the maintenance group (11 cases). According to the control of status epilepticus, the patients were divided into controlled group (11 cases) and non-responsive group (7 cases).Wilcoxon's rank sum test or Fisher's exact test were used to compare the effectiveness between groups. Results: There were 9 males and 9 females in the study group, aged 6.7 (4.5, 9.0) years. Seven cases had RSE and the remaining had SRSE. Four cases died during hospitalization. After the initiation of ketamine treatment, RSE and SRSE were controlled in 11 children. The duration of ketamine administration was 4 (2, 11) days. The dose was 2.2 (1.2, 5.3) mg/(kg·h) in all patients, and 2.4 (1.3, 6.0) mg/(kg·h), 2.0 (1.0, 4.0) mg/(kg · h) in the controlled and non-responsive group, respectively (Z=-0.272, P=0.791). The RSE or SRSE were terminated in all the 7 patients who received loading dose of ketamine, with the dose of 1.5 (0.3,1.6) mg/kg. In the 11 patients who only received maintenance treatment, 4 had the RSE and SRSE terminated, which showed a significantly lower effectiveness than in loading-maintenance group (7/7 vs. 4/11, P=0.01). Regarding the adverse reactions, saliva secretion increased in 8 children during the ketamine administration, otherwise unremarkable. Conclusion: Loading dose followed by maintenance of ketamine can control children's RSE and SRSE well, without significant adverse reactions.

Comprehensive mapping of cytochrome c oxidase activity in the rat brain after sub-chronic ketamine administration

Ketamine is a noncompetitive antagonist of glutamatergic N-methyl-d-aspartate receptors. Its acute effects on healthy volunteers and schizophrenia patients mimic some acute psychotic, but also cognitive and negative symptoms of schizophrenia, and subchronic treatment with ketamine has been used as an animal model of psychotic disorders. Glutamatergic neurotransmission is tightly coupled to oxidative metabolism in the brain. Quantitative histochemical mapping of cytochrome c oxidase (COX) activity, which reflect long-term energy metabolism, was carried out in rats that received a daily subanaesthetic dose (30 mg/kg) of ketamine for 10 days. In total, COX activity was measured in 190 brain regions to map out metabolic adaptations to the subchronic administration of ketamine. Ketamine treatment was associated with elevated COX activity in nine brain sub-regions in sensory thalamus, basal ganglia, cortical areas, hippocampus and superior colliculi. Changes in pairwise correlations between brain regions were studied with differential correlation analysis. Ketamine treatment was associated with the reduction of positive association between brain regions in 66 % of the significant comparisons. Different layers of the superior colliculi showed the strongest effects. Changes in other visual and auditory brain centres were also of note. The locus coeruleus showed opposite pattern of increased coupling to mainly limbic brain regions in ketamine-treated rats. Our study replicated commonly observed activating effects of ketamine in the hippocampus, cingulate cortex, and basal ganglia. The current study is the first to extensively map the oxidative metabolism in the CNS in the ketamine model of schizophrenia. It shows that ketamine treatment leads to the re-organization of activity in sensory and memory-related brain circuits.

Trends in drug use among electronic dance music party attendees in New York City, 2016-2019

OBJECTIVE

Electronic dance music (EDM) party attendees are a high-risk population for drug use and associated adverse effects. We examined trends in past-year drug use within this population to better inform prevention and harm reduction efforts.

METHODS

Each summer from 2016 through 2019, we used time-space sampling to survey a cross-section of adults entering EDM parties at randomly selected nightclubs and at dance festivals in New York City. Ns ranged from 504 (2019) to 1,087 (2016). We estimated log-linear trends in past-year use of 16 different synthetic drugs or drug classes.

RESULTS

Between 2016 and 2019, estimated past-year prevalence of use of ketamine increased from 5.9% to 15.3% (a 157.6% relative increase; P = .007), LSD use increased from 9.9% to 16.6% (a 67.7% relative increase, P < .001), powder cocaine use increased from 17.3% to 35.2% (a 103.5% relative increase, P < .001), and GHB use increased from 1.0% to 4.2% (a 311.8% relative increase; P = .002). Past-year use of >3 drugs increased from 12.7% to 20.5% (a 61.4% relative increase; P = .013); however, estimated past-year use of unknown powders decreased from 2.0% to 1.1% (a relative 44.7% decrease; P = .038) and ecstasy/MDMA/Molly use was stable across years (at 25.0 to 28.5 %; P = .687).

CONCLUSIONS

Reports of powder cocaine, LSD, ketamine, and GHB are becoming more prevalent among EDM party attendees. Prevention and harm reduction efforts are needed to address increasing use. Research is also needed to examine whether increasing media coverage of medical use of ketamine and other psychedelics affects prevalence of recreational use.

Antidepressant and neurocognitive effects of serial ketamine administration versus ECT in depressed patients

BACKGROUND

While electroconvulsive therapy (ECT) is considered the gold standard for acute treatment of patients with otherwise treatment-resistant depression, ketamine has recently emerged as a fast-acting treatment alternative for these patients. Efficacy and onset of action are currently among the main factors that influence clinical decision making, however, the effect of these treatments on cognitive functions should also be a crucial point, given that cognitive impairment in depression is strongly related to disease burden and functional recovery. ECT is known to induce transient cognitive impairment, while little is known about ketamine's impact on cognition. This study therefore aims to compare ECT and serial ketamine administration not only with regard to their antidepressant efficacy but also to acute neurocognitive effects.

METHODS

Fifty patients suffering from depression were treated with either serial ketamine infusions or ECT. Depression severity and cognitive functions were assessed before, during, and after treatment.

RESULTS

ECT and ketamine administration were equally effective, however, the antidepressant effects of ketamine occurred faster. Ketamine improved neurocognitive functioning, especially attention and executive functions, whereas ECT was related to a small overall decrease in cognitive performance.

CONCLUSIONS

Due to its pro-cognitive effects and faster antidepressant effect, serial ketamine administration might be a more favorable short-term treatment option than ECT.

LIMITATIONS

As this research employed a naturalistic study design, patients were not systematically randomized, there was no control group and patients received concurrent and partially changing medications during treatment.

CLINICAL TRIALS REGISTRATION

Functional and Metabolic Changes in the Course of Antidepressive Treatment, https://clinicaltrials.gov/ct2/show/NCT02099630, NCT02099630.

NLRP1-Mediated Antidepressant Effect of Ketamine in Chronic Unpredictable Mild Stress Model in Rats

OBJECTIVE

NOD-like receptor protein 1 (NLRP1) inflammasome complex has been recently associated with chronic unpredictable mild stress (CUMS) model of depression. Our aim was to investigate whether ketamine-induced antidepressant effect is associated with suppression of NLRP1.

METHODS

Wistar albino rats were divided into control, CUMS, CUMS+acute ketamine (a single 10 mg/kg dose) and CUMS+chronic ketamine (daily 10 mg/kg injections for 3 weeks) groups (n=10 for each group). Sucrose preference test and forced swimming test were performed to assess anhedonia and immobility time respectively for the severety of depression symptoms. Brain tissues were dissected and prefrontal cortex and hippocampus regions were used for real-time polymerase chain reaction (PCR) and immunohistochemical analysis.

RESULTS

CUMS procedure significantly induced depressive-like symptoms whereas both acute and chronic ketamine treatment ameliorated them. mRNA expression levels of NLRP1, caspase 1, apoptosis-associated speck-like protein containing a CARD (ASC), NF-κB, endothelial nitric oxide synthase, IL-1β, IL-6, toll-like receptor 4 (TLR-4) and purinergic 2×7 receptor (P2X7R) and numbers of Iba- 1+and GFAP+glial cells were reduced by acute and/or chronic ketamine treatment.

CONCLUSION

In the present study for the first time upstream and downstream elements of the NLRP1 inflammasome complex are shown to be suppressed by ketamine thus reinforcing the involvement of NLRP1 in the physiopathology of depression.