Brain region-specific changes in the expression of calcium sensor proteins after repeated applications of ketamine to rats

Methamphetamine-induced sensitization is associated with alterations to the proteome of the prefrontal cortex: implications for the maintenance of psychotic disorders

Repeat administration of psychostimulants, such as methamphetamine, produces a progressive increase in locomotor activity (behavioral sensitization) in rodents that is believed to represent the underlying neurochemical changes driving psychoses. Alterations to the prefrontal cortex (PFC) are suggested to mediate the etiology and maintenance of these behavioral changes. As such, the aim of the current study was to investigate changes to protein expression in the PFC in male rats sensitized to methamphetamine using quantitative label-free shotgun proteomics. A methamphetamine challenge resulted in a significant sensitized locomotor response in methamphetamine pretreated animals compared to saline controls. Proteomic analysis revealed 96 proteins that were differentially expressed in the PFC of methamphetamine treated rats, with 20% of these being previously implicated in the neurobiology of schizophrenia in the PFC. We identified multiple biological functions in the PFC that appear to be commonly altered across methamphetamine-induced sensitization and schizophrenia, and these include synaptic regulation, protein phosphatase signaling, mitochondrial function, and alterations to the inhibitory GABAergic network. These changes could inform how alterations to the PFC could underlie the cognitive and behavioral dysfunction commonly seen across psychoses and places such biological changes as potential mediators in the maintenance of psychosis vulnerability.

Dimerization of visinin-like protein 1 is regulated by oxidative stress and calcium and is a pathological hallmark of amyotrophic lateral sclerosis

Redox control of proteins that form disulfide bonds upon oxidative challenge is an emerging topic in the physiological and pathophysiological regulation of protein function. We have investigated the role of the neuronal calcium sensor protein visinin-like protein 1 (VILIP-1) as a novel redox sensor in a cellular system. We have found oxidative stress to trigger dimerization of VILIP-1 within a cellular environment and identified thioredoxin reductase as responsible for facilitating the remonomerization of the dimeric protein. Dimerization is modulated by calcium and not dependent on the myristoylation of VILIP-1. Furthermore, we show by site-directed mutagenesis that dimerization is exclusively mediated by Cys187. As a functional consequence, VILIP-1 dimerization modulates the sensitivity of cells to an oxidative challenge. We have investigated whether dimerization of VILIP-1 occurs in two different animal models of amyotrophic lateral sclerosis (ALS) and detected soluble VILIP-1 dimers to be significantly enriched in the spinal cord from phenotypic disease onset onwards. Moreover, VILIP-1 is part of the ALS-specific protein aggregates. We show for the first time that the C-terminus of VILIP-1, containing Cys187, might represent a novel redox-sensitive motif and that VILIP-1 dimerization and aggregation are hallmarks of ALS. This suggests that VILIP-1 dimers play a functional role in integrating the cytosolic calcium concentration and the oxidative status of the cell. Furthermore, a loss of VILIP-1 function owing to protein aggregation in ALS could be relevant in the pathophysiology of the disease.

A combined metabonomic and proteomic approach identifies frontal cortex changes in a chronic phencyclidine rat model in relation to human schizophrenia brain pathology

Current schizophrenia (SCZ) treatments fail to treat the broad range of manifestations associated with this devastating disorder. Thus, new translational models that reproduce the core pathological features are urgently needed to facilitate novel drug discovery efforts. Here, we report findings from the first comprehensive label-free liquid-mass spectrometry proteomic- and proton nuclear magnetic resonance-based metabonomic profiling of the rat frontal cortex after chronic phencyclidine (PCP) intervention, which induces SCZ-like symptoms. The findings were compared with results from a proteomic profiling of post-mortem prefrontal cortex from SCZ patients and with relevant findings in the literature. Through this approach, we identified proteomic alterations in glutamate-mediated Ca(2+) signaling (Ca(2+)/calmodulin-dependent protein kinase II, PPP3CA, and VISL1), mitochondrial function (GOT2 and PKLR), and cytoskeletal remodeling (ARP3). Metabonomic profiling revealed changes in the levels of glutamate, glutamine, glycine, pyruvate, and the Ca(2+) regulator taurine. Effects on similar pathways were also identified in the prefrontal cortex tissue from human SCZ subjects. The discovery of similar but not identical proteomic and metabonomic alterations in the chronic PCP rat model and human brain indicates that this model recapitulates only some of the molecular alterations of the disease. This knowledge may be helpful in understanding mechanisms underlying psychosis, which, in turn, can facilitate improved therapy and drug discovery for SCZ and other psychiatric diseases. Most importantly, these molecular findings suggest that the combined use of multiple models may be required for more effective translation to studies of human SCZ.

Effects of chronic ketamine use on frontal and medial temporal cognition

BACKGROUND

Recreational ketamine use has been on the rise worldwide. Previous studies have demonstrated that it disrupts various memory systems, but few studies have examined how it affects learning and frontal functioning. The present study investigates the effects of repeated ketamine self-administration on frontal fluency, attention, learning, and memory along the verbal/nonverbal axis.

METHODS

Twenty-five ketamine users and 30 healthy controls took a battery of neuropsychological tests. Frontal fluency was measured by the Verbal Fluency Test for semantic organization ability and the Figural Fluency Test for nonverbal executive functioning. Learning and memory were measured with the Chinese Auditory-Verbal Learning Test for acquisition and retention abilities of verbal information, as well as with the Continuous Visual Memory Test for nonverbal information. Participants also took several tests tapping subdomains of attention. To test for the potential effects of other drug use, 10 polydrug controls were included for comparison with the ketamine users and healthy controls.

RESULTS

Ketamine users had impaired verbal fluency, cognitive processing speed, and verbal learning. Verbal learning impairment was strongly correlated with estimated lifetime ketamine use. Ketamine users showed no impairments in figural fluency, sustained attention, selective attention, visual learning, or verbal/nonverbal memory. However, heavier lifetime ketamine use was significantly correlated with deficits in verbal memory (both immediate recall and delayed recall) and visual recognition memory. Deficits in cognitive processing speed and verbal learning persisted even after polydrug controls were included in the control group, but their inclusion did make the impairment in verbal fluency barely reach statistical significance.

CONCLUSIONS

This study suggests that repeated ketamine use causes differential impairment to multiple domains of frontal and medial temporal functioning, possibly specific to verbal information processing.

Increased cell proliferation in the rat anterior cingulate cortex following neonatal hypoxia: relevance to schizophrenia

As a consequence of obstetric complications, neonatal hypoxia has been discussed as an environmental factor in the pathophysiology of schizophrenia. However, the biological consequences of hypoxia are unclear. The neurodevelopmental hypothesis of schizophrenia suggests that the onset of abnormal brain development and neuropathology occurs perinatally, whereas symptoms of the disease appear in early adulthood. In our animal model of chronic neonatal hypoxia, we have detected behavioral alterations resembling those known from schizophrenia. Disturbances in cell proliferation possibly contribute to the pathophysiology of this disease. In the present study, we used postnatal rats to investigate cell proliferation in several brain areas following neonatal hypoxia. Rats were repeatedly exposed to hypoxia (89 % N₂, 11 % O₂) from postnatal day (PD) 4–8. We then evaluated cell proliferation on PD 13 and 39, respectively. These investigations were performed in the anterior cingulate cortex (ACC), caudate-putamen (CPU), dentate gyrus, and subventricular zone. Rats exposed to hypoxia exhibited increased cell proliferation in the ACC at PD 13, normalizing at PD 39. In other brain regions, no alterations have been detected. Additionally, hypoxia-treated rats showed decreased CPU volume at PD 13. The results of the present study on the one hand support the assumption of chronic hypoxia influencing transient cell proliferation in the ACC, and on the other hand reveal normalization during ageing.

Association of VSNL1 with schizophrenia, frontal cortical function, and biological significance for its gene product as a modulator of cAMP levels and neuronal morphology

We report an association of single-nucleotide polymorphisms (SNPs) for the VSNL1 gene (visinin-like 1) with schizophrenia and frontal cortical function in a sample of patients with Diagnostic and Statistical Manual of Mental Disorder-IV (DSM-IV) diagnoses of schizophrenia, compared with healthy controls. Moreover, VSNL1 SNPs were associated with performance in the Wisconsin Card Sorting Test, a measure for the assessment of frontal cortical function. The VSNL1 gene product, Visinin-like-protein-1 (VILIP-1), is a member of the neuronal EF-hand Ca(2+)-sensor protein family. Previously, VILIP-1 mRNA and protein expression were shown to be altered in animal models and in schizophrenia patients. VILIP-1 influences cytosolic cyclic adenosine mono phosphate (cAMP) levels, cell migration, exocytotic processes and differentiation in the periphery. This raises the question, whether, similar to other potential schizophrenia susceptibility genes such as Disc1, PDE4B and Akt, VSNL1 may affect cAMP signaling and neurite outgrowth in neurons. In dissociated rat hippocampal neurons, VILIP-1 small interfering RNA knockdown decreased cAMP levels and reduced dendrite branching, compared with control-transfected cells. In contrast, VILIP-1 overexpression had the opposite effect. Similar results have been obtained in the human dopaminergic neuronal cell line SH-SY5Y, where the effect on neurite branching and length was attenuated by the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine and the protein kinase A inhibitor KT5720. These results show that the association of VSNL1 SNPs with the disease and cognitive impairments, together with previously observed pathological changes in VILIP-1 protein expression, possibly occurring during brain development, may contribute to the morphological and functional deficits observed in schizophrenia.

Gene regulation in the rat prefrontal cortex after learning with or without cholinergic insult

The prefrontal cortex is essential for a wide variety of higher functions, including attention and memory. Cholinergic neurons are thought to be of prime importance in the modulation of these processes. Degeneration of forebrain cholinergic neurons has been linked to several neurological disorders. The present study was designed to identify genes and networks in rat prefrontal cortex that are associated with learning and cholinergic-loss-memory deficit. Affymetrix microarray technology was used to screen gene expression changes in rats submitted or not to 192 IgG-saporin immunolesion of cholinergic basal forebrain and trained in spatial/object novelty tasks. Results showed learning processes were associated with significant expression of genes, which were organized in several clusters of highly correlated genes and would be involved in biological processes such as intracellular signaling process, transcription regulation, and filament organization and axon guidance. Memory loss following cortical cholinergic deafferentation was associated with significant expression of genes belonging to only one clearly delineated cluster and would be involved in biological processes related to cytoskeleton organization and proliferation, and glial and vascular remodeling, i.e., in processes associated with brain repair after injury.

Alteration in the plasma concentration of a DAAO inhibitor, 3-methylpyrazole-5-carboxylic acid, in the ketamine-treated rats and the influence on the pharmacokinetics of plasma D-tryptophan

A determination method for 3-methylpyrazole-5-carboxylic acid (MPC), an inhibitor of D-amino acid oxidase (DAAO), in rat plasma was developed by using high-performance liquid chromatography-mass spectrometry (LC-MS). The structural isomer of MPC, 3-methylpyrazole-4-carboxylic acid, was used as an internal standard, and the intra- and inter-day accuracies and precisions were satisfactory for the determination of plasma MPC.Next, the LC-MS method was applied to determine the plasma MPC concentration in ketamine (Ket)-treated rats after intraperitoneal administration of MPC (5.0 or 50 mg·kg(-1)). The C(max) value of plasma MPC concentration in the Ket-treated rats was significantly higher than that in the control group when a high dose of MPC (50 mg·kg(-1)) was administered. In addition, it was found that plasma D-tryptophan (D-Trp) concentration in Ket-treated rats administered D-Trp was not significantly increased by MPC, suggesting that the DAAO-inhibitory effect of MPC is attenuated in Ket-treated rats.

Structural analysis of Mg2+ and Ca2+ binding, myristoylation, and dimerization of the neuronal calcium sensor and visinin-like protein 1 (VILIP-1)

Visinin-like protein 1 (VILIP-1) belongs to the neuronal calcium sensor family of Ca(2+)-myristoyl switch proteins that regulate signal transduction in the brain and retina. Here we analyze Ca(2+) and Mg(2+) binding, characterize metal-induced conformational changes, and determine structural effects of myristoylation and dimerization. Mg(2+) binds functionally to VILIP-1 at EF3 (ΔH = +1.8 kcal/mol and K(D) = 20 μM). Unmyristoylated VILIP-1 binds two Ca(2+) sequentially at EF2 and EF3 (K(EF3) = 0.1 μM and K(EF2) = 1-4 μM), whereas myristoylated VILIP-1 binds two Ca(2+) with lower affinity (K(D) = 1.2 μM) and positive cooperativity (Hill slope = 1.5). NMR assignments and structural analysis indicate that Ca(2+)-free VILIP-1 contains a sequestered myristoyl group like that of recoverin. NMR resonances of the attached myristate exhibit Ca(2+)-dependent chemical shifts and NOE patterns consistent with Ca(2+)-induced extrusion of the myristate. VILIP-1 forms a dimer in solution independent of Ca(2+) and myristoylation. The dimerization site is composed of residues in EF4 and the loop region between EF3 and EF4, confirmed by mutagenesis. We present the structure of the VILIP-1 dimer and a Ca(2+)-myristoyl switch to provide structural insights into Ca(2+)-induced trafficking of nicotinic acetylcholine receptors.

Proteome analysis of brain in murine experimental autoimmune encephalomyelitis

Multiple sclerosis is considered a prototype inflammatory autoimmune disorder of the CNS. Experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein is one of the best-characterized animal models of multiple sclerosis. Comprehensive understanding of gene expression in EAE can help identify genes that are important in drug response and pathogenesis. We applied a 2-DE-based proteomics approach to analyze the protein expression pattern of the brain in healthy and EAE samples. Of more than 1000 protein spots we analyzed, 70 showed reproducible and significant changes in EAE compared to controls. Of these, 42 protein spots could be identified using MALDI TOF-TOF-MS. They included mitochondrial and structural proteins as well as proteins involved in ionic and neurotransmitter release, blood barriers, apoptosis, and signal transduction. The possible role of these proteins in the responses of mice to animal models of multiple sclerosis is discussed.

Hyperpolarization-activated and cyclic nucleotide-gated channels are differentially expressed in juxtaglomerular cells in the olfactory bulb of mice

In the olfactory bulb, input from olfactory receptor neurons is processed by neuronal networks before it is relayed to higher brain regions. In many neurons, hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels generate and control oscillations of the membrane potential. Oscillations also appear crucial for information processing in the olfactory bulb. Four channel isoforms exist (HCN1-HCN4) that can form homo- or heteromers. Here, we describe the expression pattern of HCN isoforms in the olfactory bulb of mice by using a novel and comprehensive set of antibodies against all four isoforms. HCN isoforms are abundantly expressed in the olfactory bulb. HCN channels can be detected in most cell populations identified by commonly used marker antibodies. The combination of staining with marker and HCN antibodies has revealed at least 17 different staining patterns in juxtaglomerular cells. Furthermore, HCN isoforms give rise to an unexpected wealth of co-expression patterns but are rarely expressed in the same combination and at the same level in two given cell populations. Therefore, heteromeric HCN channels may exist in several cell populations in vivo. Our results suggest that HCN channels play an important role in olfactory information processing. The staining patterns are consistent with the possibility that both homomeric and heteromeric HCN channels are involved in oscillations of the membrane potential of juxtaglomerular cells.

Neuronal Ca2+ sensor VILIP-1 leads to the upregulation of functional alpha4beta2 nicotinic acetylcholine receptors in hippocampal neurons

The neuronal Ca2+-sensor protein VILIP-1, known to affect clathrin-dependent receptor trafficking, has been shown to interact with the cytoplasmic loop of the alpha4-subunit of the alpha4beta2 nicotinic acetylcholine receptor (nAChR), which is the most abundant nAChR subtype with high-affinity for nicotine in the brain. The alpha4beta2 nAChR is crucial for nicotine addiction and the beneficial effects of nicotine on cognition. Its dysfunction has been implicated in frontal lobe epilepsy, Alzheimer's disease and schizophrenia. Here we report that overexpression of VILIP-1 enhances ACh responsiveness, whereas siRNA against VILIP-1 reduces alpha4beta2 nAChR currents of hippocampal neurons. The underlying molecular mechanism likely involves enhanced constitutive exocytosis of alpha4beta2 nAChRs mediated by VILIP-1. The two interaction partners co-localize in a Ca2+-dependent manner with syntaxin-6, a Golgi-SNARE protein involved in trans-Golgi membrane trafficking. Thus, we speculate that regulation of VILIP-1-expression might modulate surface expression of ligand-gated ion channels, such as the alpha4beta2 nAChRs, possibly comprising a novel form of physiological up-regulation of ligand-gated ion channels.

A comparison of the synaptic proteome in human chronic schizophrenia and rat ketamine psychosis suggest that prohibitin is involved in the synaptic pathology of schizophrenia

Many studies in recent years suggest that schizophrenia is a synaptic disease that crucially involves a hypofunction of N-methyl-D-aspartate receptor-mediated signaling. However, at present it is unclear how these pathological processes are reflected in the protein content of the synapse. We have employed two-dimensional gel electrophoresis in conjunction with mass spectrometry to characterize and compare the synaptic proteomes of the human left dorsolateral prefrontal cortex in chronic schizophrenia and of the cerebral cortex of rats treated subchronically with ketamine. We found consistent changes in the synaptic proteomes of human schizophrenics and in rats with induced ketamine psychosis compared to controls. However, commonly regulated proteins between both groups were very limited and only prohibitin was found upregulated in both chronic schizophrenia and the rat ketamine model. Prohibitin, however, could be a new potential marker for the synaptic pathology of schizophrenia and might be causally involved in the disease process.

Implication of neuronal Ca2+ -sensor protein VILIP-1 in the glutamate hypothesis of schizophrenia

Post mortem studies in the hippocampus of schizophrenia patients revealed increased expression of neuronal Ca(2+)-sensor VILIP-1 (visinin-like protein) and enhanced co-localization with alpha4beta2 nAChR in interneurons. To study the pathological role of VILIP-1, particularly in interneurons, in the context of the glutamate hypothesis of schizophrenia, we have used ketamine-treated rats, a NMDA receptor hypofunction model, and hippocampal cultures as model systems for schizophrenia. Treatment with ketamine leads to enhanced VILIP-1 expression in interneurons in rat hippocampal CA1 region. In cultures glutamate treatment led to an increase in VILIP-1-positive interneurons, which is not dependent on NMDA receptor but metabotropic glutamate receptor activation. VILIP-1 mainly co-localizes with the interneuron marker calretinin, mGluR1alpha and the VILIP-1 interaction partner alpha4beta2 nAChR in hippocampal slices. Overexpression of VILIP-1 leads to enhanced nAChR-dependent inhibitory postsynaptic current (IPSC) generation by interneurons. This novel molecular link between the pathological role of mGluRs, VILIP-1 and its interaction partner alpha4beta2 nAChR by converging pathological glutamatergic and nicotinergic transmission may underlie cognitive impairments in schizophrenia.

Expression of the neuronal calcium sensor visinin-like protein-1 in the rat hippocampus

Visinin-like protein-1 (VILIP-1) belongs to the neuronal calcium sensor (NCS) family of EF-hand Ca(2+)-binding proteins which are involved in a variety of Ca(2+)-dependent signal transduction processes in neurons. VILIP-1 has been implicated in the pathology of CNS disorders including Alzheimer's disease and schizophrenia, but its expression has also been found to be regulated following induction of hippocampal synaptic plasticity underlying learning and memory processes. VILIP-1 is strongly expressed in different populations of principal and non-principal neurons in the rat hippocampus. VILIP-1-containing interneurons are morphologically and neurochemically heterogeneous. On the basis of co-localizing markers, VILIP-1 is rarely present in perisomatic inhibitory parvalbumin containing cells. However, VILIP-1 is frequently expressed in mid-proximal dendritic inhibitory cells characterized by calbindin immunoreactivity, and most strongly co-expressed in calretinin-positive disinhibitory interneurons. Partial co-localization of the metabotropic glutamate receptor mGluR1alpha with VILIP-1 was often found in interneurons located in the stratum oriens of the hippocampal CA1 region and in hilar interneurons. Partial co-localization of alpha4beta2 nicotinic acetylcholine receptor with VILIP-1 was seen in stratum oriens interneurons and particularly at the border of the hilus in the dentate gyrus, where VILIP-1 also strongly co-localized with calretinin. We speculate that depending on the regulation of the expression of VILIP-1 in hippocampal pyramidal cells or defined types of interneurons, it may have different effects on hippocampal synaptic plasticity and network activity in health and disease.

Acute and chronic effects of ketamine upon human memory: a review

INTRODUCTION

Ketamine is attracting increasing research interest not only because of its powerful amnestic effects but also as a putative model of schizophrenia and as a substance with an expanding following of recreational users.

OBJECTIVE

This article reviews the existing literature on the effects of acute ketamine on the memory of healthy volunteers and of repeated doses of ketamine in recreational users.

CURRENT TRENDS

Although there have been relatively few, often methodologically diverse, studies to date of the mnemonic effects of ketamine, there is an emerging consensus that an acute dose of the drug impairs the manipulation of information in working memory and produces decrements in the encoding of information into episodic memory. Preliminary evidence suggests that ketamine may differ from other classic amnestic drugs in impairing aspects of semantic memory. Acute-on-chronic effects in ketamine users generally mimic the pattern seen in controlled studies with healthy volunteers. However, chronic ketamine use may be associated with a more specific pattern of memory decrements and with episodic memory impairment, which might not abate following cessation of use.

FUTURE TRENDS

An important aim of future research should be to detail the specificity of ketamine's amnestic effects on both a neuropharmacological and a cognitive level.

Modulation of CaV2.1 channels by the neuronal calcium-binding protein visinin-like protein-2

CaV2.1 channels conduct P/Q-type Ca2+ currents that are modulated by calmodulin (CaM) and the structurally related Ca2+-binding protein 1 (CaBP1). Visinin-like protein-2 (VILIP-2) is a CaM-related Ca2+-binding protein expressed in the neocortex and hippocampus. Coexpression of CaV2.1 and VILIP-2 in tsA-201 cells resulted in Ca2+ channel modulation distinct from CaM and CaBP1. CaV2.1 channels with beta2a subunits undergo Ca2+-dependent facilitation and inactivation attributable to association of endogenous Ca2+/CaM. VILIP-2 coexpression does not alter facilitation measured in paired-pulse experiments but slows the rate of inactivation to that seen without Ca2+/CaM binding and reduces inactivation of Ca2+ currents during trains of repetitive depolarizations. CaV2.1 channels with beta1b subunits have rapid voltage-dependent inactivation, and VILIP-2 has no effect on the rate of inactivation or facilitation of the Ca2+ current. In contrast, when Ba2+ replaces Ca2+ as the charge carrier, VILIP-2 slows inactivation. The effects of VILIP-2 are prevented by deletion of the CaM-binding domain (CBD) in the C terminus of CaV2.1 channels. However, both the CBD and an upstream IQ-like domain must be deleted to prevent VILIP-2 binding. Our results indicate that VILIP-2 binds to the CBD and IQ-like domains of CaV2.1 channels like CaM but slows inactivation, which enhances facilitation of CaV2.1 channels during extended trains of stimuli. Comparison of VILIP-2 effects with those of CaBP1 indicates striking differences in modulation of both facilitation and inactivation. Differential regulation of CaV2.1 channels by CaM, VILIP-2, CaBP1, and other neurospecific Ca2+-binding proteins is a potentially important determinant of Ca2+ entry in neurotransmission.

Neuronal Ca2+ sensor protein VILIP-1 affects cGMP signalling of guanylyl cyclase B by regulating clathrin-dependent receptor recycling in hippocampal neurons

The family of neuronal Ca2+ sensor (NCS) proteins is known to influence a variety of physiological and pathological processes by affecting signalling of different receptors and ion channels. Recently, it has been shown that the NCS protein VILIP-1 influences the activity of the receptor guanylyl cyclase GC-B. In transfected cell lines, VILIP-1 performs a Ca2+-dependent membrane association, the reversible Ca2+-myristoyl switch of VILIP-1, which leads to an increase in natriuretic peptide-stimulated cGMP levels. In this study, we have investigated the effect of VILIP-1 on cGMP signalling in C6 cells and in primary hippocampal neurons, where VILIP-1 and GC-B are co-expressed in many but not all neurons and partially co-localize in the soma and in dendrites. Our data indicate that VILIP-1 modulates GC-B activity by influencing clathrin-dependent receptor recycling. These data support a general physiological role for VILIP-1 in membrane trafficking in the intact hippocampus, where the NCS protein may affect processes, such as neuronal differentiation and synaptic plasticity e.g. by influencing cGMP-signalling.

Revising a Dogma: Ketamine for Patients with Neurological Injury?

We evaluated reports of randomized clinical trials in the perioperative and intensive care setting concerning ketamine's effects on the brain in patients with, or at risk for, neurological injury. We also reviewed other studies in humans on the drug's effects on the brain, and reports that examined ketamine in experimental brain injury. In the clinical setting, level II evidence indicates that ketamine does not increase intracranial pressure when used under conditions of controlled ventilation, coadministration of a gamma-aminobutyric acid (GABA) receptor agonist, and without nitrous oxide. Ketamine may thus safely be used in neurologically impaired patients. Compared with other anesthetics or sedatives, level II and III evidence indicates that hemodynamic stimulation induced by ketamine may improve cerebral perfusion; this could make the drug a preferred choice in sedative regimes after brain injury. In the laboratory, ketamine has neuroprotective, and S(+)-ketamine additional neuroregenerative effects, even when administered after onset of a cerebral insult. However, improved outcomes were only reported in studies with brief recovery observation intervals. In developing animals, and in certain brain areas of adult rats without cerebral injury, neurotoxic effects were noted after large-dose ketamine. These were prevented by coadministration of GABA receptor agonists.

IMPLICATIONS

Ketamine can be used safely in neurologically impaired patients under conditions of controlled ventilation, coadministration of a {gamma}-aminobutyric acid receptor agonist, and avoidance of nitrous oxide. Its beneficial circulatory effects and preclinical data demonstrating neuroprotection merit further animal and patient investigation.

Beyond the K-hole: a 3-year longitudinal investigation of the cognitive and subjective effects of ketamine in recreational users who have substantially reduced their use of the drug

RATIONALE

Ketamine is a dissociative anaesthetic that is also a drug of abuse. Previous studies have demonstrated persisting episodic and semantic memory impairments in recreational ketamine users 3 days after taking ketamine. However, the degree to which these deficits might be reversible upon reduction or cessation of ketamine use was not known.

OBJECTIVE

To follow-up a population of ketamine users tested 3 years previously and examine whether impairments observed 3 days after drug use are enduring or reversible.

METHODS

Eighteen ketamine users and 10 polydrug controls from studies conducted between 3 and 4 years earlier were re-tested on the same battery of cognitive tasks and subjective measures. These tapped episodic, semantic and working memory and executive and attentional functioning. Subjective schizotypal, dissociative, mood and bodily symptoms were also examined and a drug use history recorded.

RESULTS

The ketamine users had reduced their frequency of use of ketamine by an average of 88.3%. Performance of ketamine users on tasks tapping semantic memory had improved and this improvement was correlated with their reduction in ketamine use. On tasks tapping episodic memory and attentional functioning, ketamine users still showed deficits compared to polydrug controls. Higher levels of schizotypal symptoms and perceptual distortions were exhibited by the ketamine group, although dissociative symptoms were similar to controls.

CONCLUSIONS

These findings indicate that semantic memory impairments associated with recreational ketamine are reversible upon marked reduction of use; however, impairments to episodic memory and possibly attentional functioning appear long-lasting. In addition, schizotypal symptoms and perceptual distortions may persist after cessation of ketamine use. Ketamine users, or potential users, should be aware of the enduring effects of this drug on aspects of memory and subjective experience.

Expression analysis of members of the neuronal calcium sensor protein family: combining bioinformatics and Western blot analysis

We have used in silico mining of public databases (NCBI UniGene and NCI SAGE Anatomic Viewer) as a tool to obtain the tissue distribution pattern of three members of the neuronal calcium sensor protein family, namely VILIP-1, hippocalcin, and NCS-1 in humans. The theoretical human mRNA expression profile of the calcium sensor proteins derived from expressed sequence tag (EST) and serial analysis of gene expression (SAGE) data was compared with expression data from human tissues obtained by Western blot analysis. Since the EST databank searches do not yet give comparable results for rat which is often used as model animal, we have also analyzed the protein expression in rat tissues. Similar to the human expression profile in rat tissues calcium sensor proteins are mainly detected in the nervous system, but the data consistently implicated the additional expression in peripheral tissues with remarkable differences between the calcium sensor proteins.

Repeated application of ketamine to rats induces changes in the hippocampal expression of parvalbumin, neuronal nitric oxide synthase and cFOS similar to those found in human schizophrenia

Treatment with the phencyclidine derivative ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist and a well known anesthetic, has recently been introduced to mimic schizophrenia in animals. Using rats repeatedly treated with sub-anesthetic doses we demonstrate in the hippocampal formation the cellular distribution patterns of proteins being relevant to the pathogenesis of schizophrenia. Compared with controls an increase in the density of reduced nicotinamide adenine dinucleotide phosphate diaphorase-, neuronal nitric oxide synthase- and cFOS-positive hippocampal interneurons was found, whereas the density of parvalbumin expressing cells was decreased. Our experiments show that repeated injections of sub-anesthetic doses of ketamine induce significant changes in the nitrergic and GABAergic system which, in part, resemble those described in postmortem brains of human schizophrenics indicating that sub-chronic treatment with sub-anesthetic doses of ketamine might be a useful animal model to study schizophrenia.

Increased neurogenesis in a rat ketamine model of schizophrenia

BACKGROUND

Growing evidence implicates abnormal neurodevelopment in schizophrenia, which manifests itself, for example, in reduced volume and cellular disarray of the hippocampus. This prompted us to investigate if there are indications of an altered neurodevelopment in this brain region. While neuron birth is largely completed by the end of gestation, granule neurons of the dentate gyrus are generated throughout life, thus offering an opportunity to investigate neurogenesis postnatally.

METHODS

We investigated whether repeated application of subanesthetic doses of the noncompetitive N-methyl-D-aspartate receptor antagonist ketamine, which has been shown to mimic model aspects of schizophrenia in animals, affects the hippocampal neurogenesis detected by bromodeoxyuridine incorporation. Cells were identified by immunocytochemistry.

RESULTS

Subanesthetic doses of ketamine applied subchronically enhance neurogenesis in the hippocampal subgranular zone.

CONCLUSIONS

In our animal model of schizophrenia, ketamine may evoke its stimulating effect on neurogenesis via a block of the N-methyl-D-aspartate receptor directly by reducing the c-Fos/c-Jun expression, resulting in a depression of the AP1 transcription factor complex and/or by a reduced nitric oxide production or an enhanced serotonergic activity. The newly formed neurons are not able to overcome the schizophrenia-related loss of parvalbumin expressing neurons and the behavioral abnormalities indicating that their functional integration is crucial.

Ketamine-induced changes in rat behaviour: A possible animal model of schizophrenia

It was investigated whether subchronic application of 30 mg/kg ketamine (Ket) induces reliable changes in behaviour and parameters of dopaminergic, glutamatergic, and serotonergic neurotransmissions, which might be the basis of an animal model in schizophrenia research. To test this, rats were injected with 30 mg/kg ip Ket daily for five consecutive days. In response to the first Ket injection, there was a decrease in activity time representing an acute Ket effect. Following the fifth injection, there were no differences between Ket- and saline (sal)-injected control rats in activity time, which might be a tolerance reaction. The following experiments were performed 2 or 4 weeks after Ket treatment. There were no effects on anxiety in either vehicle or Ket-treated rats using either low or high illumination levels in the elevated plus-maze. In the social interaction test, both groups of rats spent comparable times in social contact. The percentage of nonaggressive behaviour was decreased in Ket-treated rats. Two weeks after completion of the treatment, there was no effect on prepulse inhibition (PPI). Four weeks after the final Ket injection, latent inhibition (LI) was disrupted. There was no difference in the animals' activity in reaction to apomorphine (Apo) administration. Ket-treated rats injected with 0.1 mg/kg MK-801 showed an enhancement in locomotor activity. Ket treatment leads to an increase in D2 receptor binding in the hippocampus and a decrease in glutamate receptor binding in the frontal cortex. The authors did not find any changes in D1 receptor binding. The density of dopamine transporters was increased in the striatum. The density of 5-HT transporters was increased in the striatum, the hippocampus, and the frontal cortex. The results suggest that subchronic treatment with subanaesthetic doses of Ket induce schizophrenia-related alterations, which might be a useful animal model in the study of this disease.