Rapid anti-depressant-like effects of ketamine and other candidates: Molecular and cellular mechanisms

The mechanistic basis for the rapid antidepressant-like effects of ketamine: From neural circuits to molecular pathways

Conventional antidepressants that target monoaminergic receptors require several weeks to be efficacious. This lag represents a significant problem in the currently available treatments for serious depression. Ketamine, acting as an N-methyl-d-aspartate receptor antagonist, was shown to have rapid antidepressant-like effects, marking a significant advancement in the study of mood disorders. However, serious side effects and adverse reactions limit its clinical use. Considering the limitations of ketamine, it is crucial to further define the network targets of ketamine. The rapid action of ketamine an as antidepressant is thought to be mediated by the glutamate system. It is believed that synaptic plasticity is essential for the rapid effects of ketamine as an antidepressant. Other mechanisms include the involvement of the γ-aminobutyric acidergic (GABAergic), 5-HTergic systems, and recent studies have linked astrocytes to ketamine's rapid antidepressant-like effects. The interactions between these systems exert a synergistic rapid antidepressant effect through neural circuits and molecular mechanisms. Here, we discuss the neural circuits and molecular mechanisms underlying the action of ketamine. This work will help explain how molecular and neural targets are responsible for the effects of rapidly acting antidepressants and will aid in the discovery of new therapeutic approaches for major depressive disorder.

The Efficacy and Safety of Intranasal Formulations of Ketamine and Esketamine for the Treatment of Major Depressive Disorder: A Systematic Review

Ketamine and its enantiomers represent an innovative glutamatergic agent as a treatment for individuals with treatment-resistant depression (TRD) and major depressive disorder (MDD) with suicidal ideation and behavior. Intranasal (IN) formulations could allow for quick onset of action on depressive symptoms as well as a reduction in side effects by bypassing the blood-brain barrier compared with administration via the intravenous route. The aim of this review was to provide an up-to-date analysis of the data on the efficacy and safety of IN ketamine and IN esketamine for the treatment of MDD. A systematic review following PRISMA guidelines was conducted. Databases (PubMed, Embase, MEDLINE, PsycINFO, and Google Scholar) were searched to capture articles about IN ketamine or IN esketamine for MDD. This systematic review highlighted the interest in IN routes of ketamine and esketamine for MDD patients with TRD or active suicidal ideation. They provide a rapid onset of antidepressant action within the first hours after administration. Nevertheless, the evidence of efficacy is stronger for IN esketamine than for IN ketamine in MDD patients. The safety profile appears to be acceptable for IN esketamine but requires further studies, and a more accurate IN delivery device is required for ketamine.

Sleep deprivation alleviates depression-like behaviors in mice via inhibiting immune and inflammatory pathways and improving neuroplasticity

BACKGROUND

Sleep deprivation (SD) has been suggested to have a rapid antidepressant effect. There is substantial evidence that neuroinflammation and neuroplasticity play critical roles in the pathophysiology and treatment of depression. Here, we investigated the mechanisms of SD to alleviate depression-like behaviors of mice, and the role of neuroinflammation and neuroplasticity in it.

METHODS

Adult male C57BL/6 J mice were subjected to chronic restraint stress (CRS) for 6 weeks, and 6 h of SD were administrated. Behavioral tests were performed to measure depression-like behaviors. RNA-sequencing and bioinformatic analysis were performed in the anterior cingulate cortex (ACC). The differentially expressed genes were confirmed by quantitative real-time polymerase chain reaction (RT-qPCR). Neuroinflammation and neuroplasticity were measured by western blotting and immunofluorescence staining.

RESULTS

Behavioral tests demonstrated that SD swiftly attenuated the depression-like behaviors induced by CRS. RNA-sequencing identified the upregulated immune and inflammatory pathways after CRS exposure were downregulated by SD. Furthermore, SD reversed the levels of immune and inflammation-related mRNA, pro-inflammatory factors and microglia activation in ACC. Additionally, the impaired neuroplasticity elicited by CRS in the prefrontal cortex (PFC) and ACC were improved by SD.

LIMITATIONS

More in-depth studies are required to determine the role of different SD protocols in depressive symptoms and their underlying mechanisms.

CONCLUSIONS

Our study revealed the rapid antidepressant effect of SD on CRS mice through the reduction of the neuroinflammatory response in ACC and the improvement of neuroplasticity in PFC and ACC, providing a theoretical basis for the clinical application of SD as a rapid antidepressant treatment.

Effects of recurrent ketamine exposure on brain histopathology in juvenile rats

BACKGROUND

Ketamine (KET) is a commonly used anesthetic agent. However, several previous studies reported that KET leads to neuronal damage in neurodevelopmental stages and has neuroprotective effects. The present experimental study aimed to determine the undesirable histopathological effects of KET in the cerebral cortex, striatum, and hippocampus after recurrent KET administration in juvenile rats.

METHODS

After ethical approval was obtained, 32 juvenile male Wistar Albino rats were randomized into four groups: 1 mg/kg serum saline intraperitoneally (i.p.), 5 mg/kg KET i.p., 20 mg/kg KET i.p., and 50 mg/kg KET i.p. KET was administered for three consecutive days at three-h intervals in three doses. Ten days after the last KET dose, the rats were sacrificed. Cerebral hemispheres were fixed. Hematoxylin and eosin stain was used for morphometric analysis. Hippocampi were evaluated by immunohistochemistry with anticleaved caspase-3 antibodies. Statistical analysis was conducted with SPSS 21 software using the ANOVA test and Bonferroni post hoc analysis method.

RESULTS

The experimental study findings revealed no difference between the groups' cell counts or sizes in cortical morphometry. No degenerative changes were observed in pyramidal and granular cells in the striatum. Mild gliosis was observed in the 20 mg/kg and 50 mg/kg KET administration groups. Immuno-histo-chemical analysis was conducted to determine apoptosis in the CA1 region of the hippocampus and revealed that caspase-3 positivity increased with the KET dose. However, there was no statistical difference between the groups. While it was lower than the control group in the 5 mg/kg KET group, it was similar to the control group in the 20 mg/kg KET group and higher in the 50 mg/kg KET group (p > 0.05).

DISCUSSION

: Repetitive KET exposure did not significantly affect juvenile cerebral morphology and apoptosis in hippocampal cells.

Antipanic-like effect of esketamine and buprenorphine in rats exposed to acute hypoxia

The antidepressant effect of ketamine has been widely acknowledged and the use of one of its enantiomers, S-ketamine (esketamine), has recently been approved for the clinical management of treatment-resistant depression. As with ketamine, the non-selective opioid receptor-interacting drug buprenorphine is reported to have antidepressant and anxiolytic properties in humans and rodents. Given the fact that antidepressant drugs are also first line treatment for panic disorder, it is surprising that the potential panicolytic effect of these compounds has been scarcely (ketamine), or not yet (buprenorphine) investigated. We here evaluated the effects of ketamine (the racemic mixture), esketamine, and buprenorphine in male Wistar rats submitted to a panicogenic challenge: acute exposure to hypoxia (7% O₂). We observed that esketamine (20 mg/kg), but not ketamine, decreased the number of escape attempts made during hypoxia, and this effect could be observed even 7 days after the drug administration. A panicolytic-like effect was also observed with MK801, which like esketamine, antagonizes NMDA glutamate receptors. Buprenorphine (0.3 mg/kg) also impaired hypoxia-induced escape, an effect blocked by the non-selective opioid receptor antagonist naloxone, indicating an interaction with classical ligand sites, such as µ and kappa receptors, but not with nociception/orphanin FQ receptors. Altogether, the results suggest that esketamine and buprenorphine cause rapid-onset panicolytic-like effects, and may be alternatives for treating panic disorder, particularly in patients who are refractory to standard pharmacological treatment.

Major Depression: One Brain, One Disease, One Set of Intertwined Processes

Major depressive disorder (MDD) is a heterogeneous disease affecting one out of five individuals and is the leading cause of disability worldwide. Presently, MDD is considered a multifactorial disease with various causes such as genetic susceptibility, stress, and other pathological processes. Multiple studies allowed the formulation of several theories attempting to describe the development of MDD. However, none of these hypotheses are comprehensive because none of them can explain all cases, mechanisms, and symptoms of MDD. Nevertheless, all of these theories share some common pathways, which lead us to believe that these hypotheses depict several pieces of the same big puzzle. Therefore, in this review, we provide a brief description of these theories and their strengths and weaknesses in an attempt to highlight the common mechanisms and relationships of all major theories of depression and combine them together to present the current overall picture. The analysis of all hypotheses suggests that there is interdependence between all the brain structures and various substances involved in the pathogenesis of MDD, which could be not entirely universal, but can affect all of the brain regions, to one degree or another, depending on the triggering factor, which, in turn, could explain the different subtypes of MDD.

Rapid anti-depressant-like effects of ketamine and other candidates: Molecular and cellular mechanisms

Major depressive disorder takes at least 3 weeks for clinical anti‐depressants, such as serotonin selective reuptake inhibitors, to take effect, and only one‐third of patients remit. Ketamine, a kind of anaesthetic, can alleviate symptoms of major depressive disorder patients in a short time and is reported to be effective to treatment‐resistant depression patients. The rapid and strong anti‐depressant‐like effects of ketamine cause wide concern. In addition to ketamine, caloric restriction and sleep deprivation also elicit similar rapid anti‐depressant‐like effects. However, mechanisms about the rapid anti‐depressant‐like effects remain unclear. Elucidating the mechanisms of rapid anti‐depressant effects is the key to finding new therapeutic targets and developing therapeutic patterns. Therefore, in this review we summarize potential molecular and cellular mechanisms of rapid anti‐depressant‐like effects based on the pre‐clinical and clinical evidence, trying to provide new insight into future therapy.