Neonatal exposure of ketamine inhibited the induction of hippocampal long-term potentiation without impairing the spatial memory of adult rats

Versatile, reusable and highly sensitive SERS-based point-of-care testing microplatform for reliable ATP detection

The advancement in miniaturized Raman spectrometers, coupled with the single-molecule-level sensitivity and unique fingerprint identification capability of surface-enhanced Raman scattering (SERS), offers great potential for point-of-care testing (POCT). Despite this, accurately quantifying analyte molecules, particularly in complex samples with limited sample volumes, remains difficult. Herein, we present a versatile and reusable SERS microplatform for highly sensitive and reliable quantitative detection of adenosine triphosphate (ATP) in biological fluids. The platform utilizes gold-Prussian blue core-shell nanoparticles modified with polyethyleneimine (Au@PB@PEI NPs), embedded within gold nanoparticle-immobilized capillary-based silica monolithic materials. PB acts as an internal standard, while PEI enhances molecular capture. The periodic, bimodal porous structure of the silica monolithic materials provides uniform and abundant sites for nanoparticle attachment, facilitating rapid liquid permeation, intense SERS enhancement, and efficient enrichment. The platform regulates ATP capture and release through magnesium ions in the liquid phase, eliminating matrix interferences and enabling platform reuse. Integrating efficient molecular enrichment, separation, an interference-free internal standard, a liquid flow channel, and a detection chamber, our platform offers simplicity in operation, exceptional sensitivity and accuracy, and rapid analysis (∼10 min). Employing PB as an internal calibration standard, ratiometric Raman signals (I732/I2123) facilitate precise ATP quantification, achieving a remarkable limit of detection down to 0.62 pM. Furthermore, this platform has been proven to be highly reproducible and validated for ATP quantification in both mouse cerebrospinal fluid and human serum, underscoring its immense potential for POCT applications.

Age, Dose, and Locomotion: Decoding Vulnerability to Ketamine in C57BL/6J and BALB/c Mice

Ketamine has been abused as a psychedelic agent and causes diverse neurobehavioral changes. Adolescence is a critical developmental stage but vulnerable to substances and environmental stimuli. Growing evidence shows that ketamine affects glutamatergic neurotransmission, which is important for memory storage, addiction, and psychosis. To explore diverse biological responses, this study was designed to assess ketamine sensitivity in mice of different ages and strains. Male C57BL/6J and BALB/c mice were studied in adolescence and adulthood separately. An open field test assessed motor behavioral changes. After a 30-min baseline habituation, mice were injected with ketamine (0, 25, and 50 mg/kg), and their locomotion was measured for 60 min. Following ketamine injection, the travelled distance and speed significantly increased in C57BL/6J mice between both age groups (p < 0.01), but not in BALB/c mice. The pattern of hyperlocomotion showed that mice were delayed at the higher dose (50 mg/kg) compared to the lower dose (25 mg/kg) of ketamine treatment. Ketamine accentuated locomotor activation in adolescent C57BL/6J mice compared to adults, but not in the BALB/c strain. Here, we show that ketamine-induced locomotor behavior is modulated by dose and age. The discrepancy of neurobehaviors in the two strains of mice indicates that sensitivity to ketamine is biologically determined. This study suggests that individual vulnerability to ketamine's pharmacological responses varies biologically.

Neonatal exposures to sevoflurane in rhesus monkeys alter synaptic ultrastructure in later life

Repeated or prolonged early life exposure to anesthesia is neurotoxic in animals and associated with neurocognitive impairment in later life in humans. We used electron microscopy with unbiased stereological sampling to assess synaptic ultrastructure in dorsolateral prefrontal cortex (dlPFC) and hippocampal CA1 of female and male rhesus monkeys, four years after three 4-h exposures to sevoflurane during the first five postnatal weeks. This allowed us to ascertain long-term consequences of anesthesia exposure without confounding effects of surgery or illness. Synapse areas were reduced in the largest synapses in CA1 and dlPFC, predominantly in perforated spinous synapses in CA1 and nonperforated spinous synapses in dlPFC. Mitochondrial morphology and localization changed subtly in both areas. Synapse areas in CA1 correlated with response to a mild social stressor. Thus, exposure to anesthesia in infancy can cause long-term ultrastructural changes in primates, which may be substrates for long-term alterations in synaptic transmission and behavioral deficits.

Prophylactic Effects of Sub-anesthesia Ketamine on Cognitive Decline, Neuroinflammation, and Oxidative Stress in Elderly Mice

Cognitive dysfunction is a very common postoperative complication. The study aimed at investigating the effects of ketamine on the cognition of elderly mice after anesthesia and surgery (AS). We reported that AS impaired the cognition of elderly mice, while ketamine helped to maintain the cognitive function. Ketamine decreased the levels of TNF-α, IL-6, IL-1β and the expression of p-TAU, S100B in hippocampal induced by AS. In addition, AS triggered severe oxidative stress in hippocampal, while ketamine inhibited it. Oxidative stress induced autophagy of hippocampal neurons via inhibiting PI3K/AKT/mTOR pathway. Ketamine could activate PI3K pathway and inhibit autophagy in hippocampal, thus maintain the loss of hippocampal neurons. The study suggested that ketamine inhibited the neuroinflammation and oxidative stress, reduced the autophagy of hippocampal neurons via PI3K/AKT/mTOR pathway. It may provide novel methods for the protection of cognitive function in elderly during perioperative period.

Betaine prevents and reverses the behavioral deficits and synaptic dysfunction induced by repeated ketamine exposure in mice

As an N-methyl-D-aspartate (NMDA) receptor inhibitor, ketamine has become a popular recreational substance and currently is used to address treatment-resistant depression. Since heavy ketamine use is associated with persisting psychosis, cognitive impairments, and neuronal damage, the safety of ketamine treatment for depression should be concerned. The nutrient supplement betaine has been shown to counteract the acute ketamine-induced psychotomimetic effects and cognitive dysfunction through modulating NMDA receptors. This study aimed to determine whether the adjunctive or subsequent betaine treatment would improve the enduring behavioral disturbances and hippocampal synaptic abnormality induced by repeated ketamine exposure. Mice received ketamine twice daily for 14 days, either combined with betaine co-treatment or subsequent betaine post-treatment for 7 days. Thereafter, three-chamber social approach test, reciprocal social interaction, novel location/object recognition test, forced swimming test, and head-twitch response induced by serotonergic hallucinogen were monitored. Data showed that the enduring behavioral abnormalities after repeated ketamine exposure, including disrupted social behaviors, recognition memory impairments, and increased depression-like and hallucinogen-induced head-twitch responses, were remarkably improved by betaine co-treatment or post-treatment. Consistently, betaine protected and reversed the reduced hippocampal synaptic activity, such as decreases in field excitatory post-synaptic potentiation (fEPSP), long-term potentiation (LTP), and PSD-95 levels, after repeated ketamine treatment. These results demonstrated that both co-treatment and post-treatment with betaine could effectively prevent and reverse the adverse behavioral manifestations and hippocampal synaptic plasticity after repeated ketamine use, suggesting that betaine can be used as a novel adjunct therapy with ketamine for treatment-resistant depression and provide benefits for ketamine use disorders.

Effects of general anesthetics on synaptic transmission and plasticity

General anesthetics depress excitatory and/or enhance inhibitory synaptic transmission principally by modulating the function of glutamatergic or GABAergic synapses, respectively, with relative anesthetic agent-specific mechanisms. Synaptic signaling proteins, including ligand- and voltage-gated ion channels, are targeted by general anesthetics to modulate various synaptic mechanisms, including presynaptic neurotransmitter release, postsynaptic receptor signaling, and dendritic spine dynamics to produce their characteristic acute neurophysiological effects. As synaptic structure and plasticity mediate higher-order functions such as learning and memory, long-term synaptic dysfunction following anesthesia may lead to undesirable neurocognitive consequences depending on the specific anesthetic agent and the vulnerability of the population. Here we review the cellular and molecular mechanisms of transient and persistent general anesthetic alterations of synaptic transmission and plasticity.

Ionic channel blockage in stochastic Hodgkin-Huxley neuronal model driven by multiple oscillatory signals

Ionic channel blockage and multiple oscillatory signals play an important role in the dynamical response of pulse sequences. The effects of ionic channel blockage and ionic channel noise on the discharge behaviors are studied in Hodgkin-Huxley neuronal model with multiple oscillatory signals. It is found that bifurcation points of spontaneous discharge are altered through tuning the amplitude of multiple oscillatory signals, and the discharge cycle is changed by increasing the frequency of multiple oscillatory signals. The effects of ionic channel blockage on neural discharge behaviors indicate that the neural excitability can be suppressed by the sodium channel blockage, however, the neural excitability can be reversed by the potassium channel blockage. There is an optimal blockage ratio of potassium channel at which the electrical activity is the most regular, while the order of neural spike is disrupted by the sodium channel blockage. In addition, the frequency of spike discharge is accelerated by increasing the ionic channel noise, the firing of neuron becomes more stable if the ionic channel noise is appropriately reduced. Our results might provide new insights into the effects of ionic channel blockages, multiple oscillatory signals, and ionic channel noises on neural discharge behaviors.

Neonatal ketamine exposure-induced hippocampal neuroapoptosis in the developing brain impairs adult spatial learning ability

Ketamine exposure can lead to selective neuroapoptosis in the developing brain. p66ShcA, the cellular adapter protein expressed selectively in immature neurons, is a known pro-apoptotic molecule that triggers neuroapoptosis when activated. Sprague-Dawley rats at postnatal day 7 were subcutaneously injected in the neck with ketamine 20 mg/kg, six times at 2-hour intervals. At 0, 1, 3, and 6 hours after final injection, western blot assay was used to detect the expression of cleaved caspase-3, p66ShcA, and phosphorylated p66ShcA. We found that the expression of activated p66ShcA and caspase-3 increased after ketamine exposure and peaked at 3 hours. The same procedure was performed on a different group of rats. At the age of 4 weeks, spatial learning and memory abilities were tested with the Morris water maze. Latency to find the hidden platform for these rats was longer than it was for control rats, although the residence time in the target quadrant was similar. These findings indicate that ketamine exposure resulted in p66ShcA being activated in the course of an apoptotic cascade during the neonatal period. This may have contributed to the deficit in spatial learning and memory that persisted into adulthood. The experimental protocol was approved by the Institutional Animal Care and Use Committee at the University of Texas at Arlington, USA (approval No. A13.008) on January 22, 2013.

Intranasal insulin administration may be highly effective in improving cognitive function in mice with cognitive dysfunction by reversing brain insulin resistance

It is well known in clinical practice that Alzheimer's disease (AD) is closely associated with brain insulin resistance, and the cerebral insulin pathway has been proven to play a critical role in the pathogenesis of AD. However, finding the most efficient way to improve brain insulin resistance remains challenging. Peripheral administration of insulin does not have the desired therapeutic effect and may induce adverse reactions, such as hyperinsulinemia, but intranasal administration may be an efficient way. In the present study, we established a brain insulin resistance model through an intraventricular injection of streptozotocin, accompanied by cognitive impairment. Following intranasal insulin treatment, the learning and memory functions of mice were significantly restored, the neurogenesis in the hippocampus was improved, the level of insulin in the brain increased, and the activation of the IRS-1-PI3K-Akt-GSK3β insulin signal pathway, but not the Ras-Raf-MEK-MAPK pathway, was markedly increased. The olfactory bulb-subventricular zone-subgranular zone (OB-SVZ-SGZ) axis might be the mechanism through which intranasal insulin regulates cognition in brain-insulin-resistant mice. Thus, intranasal insulin administration may be a highly efficient way to improve cognitive function by increasing cerebral insulin levels and reversing insulin resistance.

Effects of Exercise on Long-Term Potentiation in Neuropsychiatric Disorders

Various neuropsychiatric conditions, such as depression, Alzheimer's disease, and Parkinson's disease, demonstrate evidence of impaired long-term potentiation, a cellular correlate of episodic memory function. This chapter discusses the mechanistic effects of these neuropsychiatric conditions on long-term potentiation and how exercise may help to attenuate these detrimental effects.

Cordycepin improves behavioral-LTP and dendritic structure in hippocampal CA1 area of rats

Cordycepin, an adenosine analog, has been reported to improve cognitive function, but which seems to be inconsistent with the reports showing that cordycepin inhibited long-term potentiation (LTP). Behavioral-LTP is usually used to study long-term synaptic plasticity induced by learning tasks in freely moving animals. In order to investigate simultaneously the effects of cordycepin on LTP and behavior in rats, we applied the model of behavioral-LTP induced by Y-maze learning task through recording population spikes in hippocampal CA1 region. Golgi staining and Sholl analysis were employed to assess the morphological structure of dendrites in pyramidal cells of hippocampal CA1 area, and western blotting was used to examine the level of adenosine A1 receptors and A2A receptors (A2AR). We found that cordycepin significantly improved behavioral-LTP magnitude, accompanied by increases in the total length of dendrites, the number of intersections and spine density but did not affect Y-maze learning task. Furthermore, cordycepin obviously reduced A2AR level without altering adenosine A1 receptors level; and the agonist of A2AR (CGS 21680) rather than antagonist (SCH 58261) could reverse the potentiation of behavioral-LTP induced by cordycepin. These results suggested that cordycepin improved behavioral-LTP and morphological structure of dendrite in hippocampal CA1 but did not contribute to the improvement of learning and memory. And cordycepin improved behavioral-LTP may be through reducing the level of A2AR in hippocampus. Collectively, the effects of cordycepin on cognitive function and LTP were complex and involved multiple mechanisms.

Temperature effect on memristive ion channels

Neuron shows distinct dependence of electrical activities on membrane patch temperature, and the mode transition of electrical activity is induced by the patch temperature through modulating the opening and closing rates of ion channels. In this paper, inspired by the physical effect of memristor, the potassium and sodium ion channels embedded in the membrane patch are updated by using memristor-based voltage gate variables, and an external stimulus is applied to detect the variety of mode selection in electrical activities under different patch temperatures. It is found that each ion channel can be regarded as a physical memristor, and the shape of pinched hysteresis loop of memristor is dependent on both input voltage and patch temperature. The pinched hysteresis loops of two ion-channel memristors are dramatically enlarged by increasing patch temperature, and the hysteresis lobe areas are monotonously reduced with the increasing of excitation frequency if the frequency of external stimulus exceeds certain threshold. However, for the memristive potassium channel, the AREA1 corresponding to the threshold frequency is increased with the increasing of patch temperature. The amplitude of conductance for two ion-channel memristors depends on the variation of patch temperature. The results of this paper might provide insights to modulate the neural activities in appropriate temperature condition completely, and involvement of external stimulus enhance the effect of patch temperature.

L-menthol exhibits antidepressive-like effects mediated by the modification of 5-HTergic, GABAergic and DAergic systems

Major depression disorder, also known as depression, with a significant and persistent low mood as the main clinical features, is the main type of mood disorders. L-menthol (LM), the main active ingredient of mint, has been considered as safe and healthy natural ingredient by the Food and Drug Administration in the USA. In this study, LM (40 mg/kg, i.g.) produced antidepressant-like effect in the forced swimming test (FST) in mice. The sub-effective dose (5 mg/kg, i.g.) of LM combined with the sub-effective dose of fluoxetine (5 mg/kg, i.p.) or reboxetine (2.5 mg/kg, i.p.) could significantly shorten the immobility time in the FST. Pretreatment with ondansetron (a highly selective 5-HT₃ receptor antagonist, 8 mg/kg, i.p.), bicuculline [a competitive γ-aminobutyric acid (GABA) antagonist, 4 mg/kg, i.p.] and haloperidol (a non-selective D₂ receptor antagonist, 0.2 mg/kg, i.p.) significantly reversed the antidepressant-like effect of LM (40 mg/kg, i.g.). In contrast, prazosin (a α1-adrenoceptor antagonist, 1 mg/kg, i.p.) and N-methyl-d-aspartic acid (an agonist at the glutamate site, 75 mg/kg, i.p.) did not eliminate the antidepressant-like effect of LM. All of these above indicated that LM is able to induce an antidepressant-like effect mediated by the modification of 5-HTergic, GABAergic and DAergic systems in the FST. LM might be used as combination therapy in depressed patients and is a potential antidepressant.