Psilocybin sex-dependently reduces alcohol consumption in C57BL/6J mice

The classical psychedelic psilocybin is of interest as a treatment for alcohol use disorder (AUD). This study investigated the effects of psilocybin on voluntary ethanol consumption in adult male and female C57BL/6J mice administered saline or psilocybin intraperitoneally as a single dose of 0.1, 0.5, 1.0 or 2.0 mg/kg and provided 20% ethanol utilizing a two-bottle choice alcohol drinking paradigm. Ethanol was provided continuously for 3 days immediately following the administration of psilocybin, then withheld for 2 days, and then provided continuously for two subsequent additional days. A multilevel model (MLM) for repeated measures was used to compare ethanol consumption and preference in psilocybin-treated groups versus controls. Ethanol consumption and preference were reduced in male mice during the 3-day interval that immediately followed psilocybin administration. The effect of psilocybin on ethanol consumption was dose-related and was consistent across the 3-day interval at dosages of 0.5 mg/kg or greater. Psilocybin had no effect on consumption or preference when ethanol was subsequently reintroduced after 2 days of withdrawal. In contrast to males, psilocybin had no significant effect on ethanol consumption or preference in female mice at any dosage or time point. The lack of an effect of psilocybin on quinine preference, and its limited interaction with locomotor activity indicated that the observed reduction in voluntary ethanol consumption was not attributable to altered taste perception or motor effects. Total fluid consumption was increased in males at some time points and psilocybin dosages and unchanged in females, and the absence of any decrease in either group at any time point indicated that the observed reduction in ethanol consumption was not mediated by nonspecific effects on consummatory behavior. The finding of a sex-dependent effect of psilocybin on ethanol consumption suggests that the C57BL/6J mouse may provide a useful experimental approach to modeling sex differences in vulnerability to AUD in addition to investigation of the neurobiological basis of the effect of classical psychedelics on alcohol drinking behavior.

Cocaine perturbs mitovesicle biology in the brain

Cocaine, an addictive psychostimulant, has a broad mechanism of action, including the induction of a wide range of alterations in brain metabolism and mitochondrial homeostasis. Our group recently identified a subpopulation of non-microvesicular, non-exosomal extracellular vesicles of mitochondrial origin (mitovesicles) and developed a method to isolate mitovesicles from brain parenchyma. We hypothesised that the generation and secretion of mitovesicles is affected by mitochondrial abnormalities induced by chronic cocaine exposure. Mitovesicles from the brain extracellular space of cocaine-administered mice were enlarged and more numerous when compared to controls, supporting a model in which mitovesicle biogenesis is enhanced in the presence of mitochondrial alterations. This interrelationship was confirmed in vitro. Moreover, cocaine affected mitovesicle protein composition, causing a functional alteration in mitovesicle ATP production capacity. These data suggest that mitovesicles are previously unidentified players in the biology of cocaine addiction and that target therapies to fine-tune brain mitovesicle functionality may be beneficial to mitigate the effects of chronic cocaine exposure.

Deficits in odor discrimination versus odor identification in patients with schizophrenia and negative correlations with GABAergic and DNA methyltransferase mRNAs in lymphocytes

Introduction

People with schizophrenia have been reported to show deficits in tests of olfactory function. DNA methylation and GABAergic input have been implicated in biochemical processes controlling odor in animal studies, but this has not been investigated in human studies.

Methods

In a study of measures of DNA methylation and GABAergic mRNAs in lymphocytes, we also measured odor identification and discrimination with the Sniffin' Sticks battery in 58 patients with chronic schizophrenia (CSZ) and 48 controls. mRNAs in lymphocytes were assessed by qPCR using TaqManTM probes. Cognition was assessed by the MATRICS battery (Measurement and Treatment Research to Improve Cognition in Schizophrenia) in CSZ and controls, and symptoms in CSZ were assessed by PANSS scale (Positive and Negative Symptom Scale). The relationships of odor deficits with mRNA, cognition, and symptoms were explored by correlation analysis. Variables which significantly differentiated CSZ from controls were explored by logistic regression.

Results

Overall, CSZ showed significantly (P≤.001) lower scores on odor discrimination compared to controls, with a moderate effect size, but no difference in odor identification. Deficits in odor discrimination, which has not been standardly assessed in many prior studies, strongly differentiated CSZ from controls. In logistic regression analysis, odor discrimination, but not odor identification, was a significant variable predicting schizophrenia versus control class membership. This is the first study to report relationship between odor deficits and DNA methylation and GABAergic mRNAs in blood cells of human subjects. There were negative correlations of odor identification with DNA methylation enzymes mRNAs and significant negative correlations with odor discrimination and GABAergic mRNAs. Lower odor scores were significantly associated with lower cognitive scores on the MATRICS battery in CSZ but not control subjects. In CSZ, lower odor scores were significantly associated with negative symptom scores, while higher odor identification scores were associated with PANNS Excitement factor.

Discussion

Odor discrimination was a more powerful variable than odor identification in discriminating CSZ from controls and should be used more regularly as an odor measure in studies of schizophrenia. The substantive meaning of the negative correlations of odor discrimination and GABAergic mRNA variables in peripheral lymphocytes of CSZ needs more investigation and comparison with results in neural tissue.

Changes in Expression of DNA-Methyltransferase and Cannabinoid Receptor mRNAs in Blood Lymphocytes After Acute Cannabis Smoking

BACKGROUND

Cannabis use is a component risk factor for the manifestation of schizophrenia. The biological effects of cannabis include effects on epigenetic systems, immunological parameters, in addition to changes in cannabinoid receptors 1 and 2, that may be associated with this risk. However, there has been limited study of the effects of smoked cannabis on these biological effects in human peripheral blood cells. We analyzed the effects of two concentrations of tetrahydrocannabinol (THC) vs. placebo in lymphocytes of a subset of participants who enrolled in a double-blind study of the effects of cannabis on driving performance (outcome not the focus of this study).

METHODS

Twenty four participants who regularly use cannabis participated in an experiment in which they smoked cannabis cigarettes (5.9 or 13.4% THC) or placebo (0.02%) ad libitum. Blood samples were drawn at baseline and several times after smoking. Lymphocytes were separated and stored at -80^°C for further analysis. Samples were analyzed for mRNA content for cannabinoid receptors 1 (CB1) and 2 (CB2), methylation and demethylating enzymes (DNMT, TET), glucocorticoid receptor (NRC3) and immunological markers (IL1B, TNFα) by qPCR using TaqMan probes. The results were correlated with THC whole blood levels during the course of the day, as well as THCCOOH baseline levels. Statistical analyses used analysis of variance and covariance and t-tests, or non-parametric equivalents for those values which were not normally distributed.

RESULTS

There were no differences in background baseline characteristics of the participants except that the higher concentration THC group was older than the low concentration and placebo groups, and the low concentration THC group had higher baseline CB2 mRNA levels. Both the 5.9 and 13.4% THC groups showed increased THC blood levels that then decreased toward baseline within the first hour. However, there were no significant differences between THC blood levels between the 5.9 and 13.4% groups at any time point. At the 4-h time point after drug administration the 13.4% THC group had higher CB2 (P = 0.021) and DNMT3A (P = 0.027) mRNA levels than the placebo group. DNMT1 mRNA levels showed a trend in the same direction (P = 0.056). The higher 13.4% THC group had significantly increased CB2 mRNA levels than the 5.9% concentration group at several post drug administration time points and showed trends for difference in effects for between 5.9 and 13.4% THC groups for other mRNAs. TET3 mRNA levels were higher in the 13.4% THC group at 55 min post-cannabis ingestion. When the high and lower concentration THC groups were combined, none of the differences in mRNA levels from placebo remained statistically significant. Changes in THC blood levels were not related to changes in mRNA levels.

CONCLUSION

Over the time course of this study, CB2 mRNA increased in blood lymphocytes in the high concentration THC group but were not accompanied by changes in immunological markers. The changes in DNMT and TET mRNAs suggest potential epigenetic effects of THC in human lymphocytes. Increases in DNMT methylating enzymes have been linked to some of the pathophysiological processes in schizophrenia and, therefore, should be further explored in a larger sample population, as one of the potential mechanisms linking cannabis use as a trigger for schizophrenia in vulnerable individuals. Since the two THC groups did not differ in post-smoking blood THC concentrations, the relationship between lymphocytic changes and the THC content of the cigarettes remains to be determined.

Cocaine Induces Sex-Associated Changes in Lipid Profiles of Brain Extracellular Vesicles

Cocaine is a highly addictive stimulant with diverse effects on physiology. Recent studies indicate the involvement of extracellular vesicles (EVs) secreted by neural cells in the cocaine addiction process. It is hypothesized that cocaine affects secretion levels of EVs and their cargos, resulting in modulation of synaptic transmission and plasticity related to addiction physiology and pathology. Lipids present in EVs are important for EV formation and for intercellular lipid exchange that may trigger physiological and pathological responses, including neuroplasticity, neurotoxicity, and neuroinflammation. Specific lipids are highly enriched in EVs compared to parent cells, and recent studies suggest the involvement of various lipids in drug-induced synaptic plasticity during the development and maintenance of addiction processes. Therefore, we examined interstitial small EVs isolated from the brain of mice treated with either saline or cocaine, focusing on the effects of cocaine on the lipid composition of EVs. We demonstrate that 12 days of noncontingent repeated cocaine (10 mg/kg) injections to mice, which induce locomotor sensitization, cause lipid composition changes in brain EVs of male mice as compared with saline-injected controls. The most prominent change is the elevation of GD1a ganglioside in brain EVs of males. However, cocaine does not affect the EV lipid profiles of the brain in female mice. Understanding the relationship between lipid composition in EVs and vulnerability to cocaine addiction may provide insight into novel targets for therapies for addiction.

Gene Expression Of Methylation Cycle And Related Genes In Lymphocytes And Brain Of Patients With Schizophrenia And Non-Psychotic Controls

Some of the biochemical abnormalities underlying schizophrenia, involve differences in methylation and methylating enzymes, as well as other related target genes. We present results of a study of differences in mRNA expression in peripheral blood lymphocytes (PBLs) and post-mortem brains of chronic schizophrenics (CSZ) and non-psychotic controls (NPC), emphasizing the differential effects of sex and antipsychotic drug treatment on mRNA findings. We studied mRNA expression in lymphocytes of 61 CSZ and 49 NPC subjects using qPCR assays with TaqMan probes to assess levels of DNMT, TET, GABAergic, NR3C1, BDNF mRNAs, and several additional targets identified in a recent RNA sequence analysis. In parallel we studied DNMT1 and GAD67 in samples of brain tissues from 19 CSZ, 26 NPC. In PBLs DNMT1 and DNMT3A mRNA levels were significantly higher in male CSZ vs NPC. No significant differences were detected in females. The GAD1, NR3C1 and CNTNAP2 mRNA levels were significantly higher in CSZ than NPC. In CSZ patients treated with clozapine, GAD-1 related, CNTNAP2, and IMPA2 mRNAs were significantly higher than in CSZ subjects not treated with clozapine. Differences between CSZ vs NPC in these mRNAs was primarily attributable to the clozapine treatment. In the brain samples, DNMT1 was significantly higher and GAD67 was significantly lower in CSZ than in NPC, but there were no significant sex differences in diagnostic effects. These findings highlight the importance of considering sex and drug treatment effects in assessing the substantive significance of differences in mRNAs between CSZ and NPC.

Concordance of Immune-Related Markers in Lymphocytes and Prefrontal Cortex in Schizophrenia

Schizophrenia is a severe neuropsychiatric disorder associated with a wide array of transcriptomic and neurobiochemical changes. Genome-wide transcriptomic profiling conducted in postmortem brain have provided novel insights into the pathophysiology of this disorder, and identified biological processes including immune/inflammatory-related responses, metabolic, endocrine, and synaptic function. However, few studies have investigated whether similar changes are present in peripheral tissue. Here, we used RNA-sequencing to characterize transcriptomic profiles of lymphocytes in 18 nonpsychotic controls and 19 individuals with schizophrenia. We identified 2819 differentially expressed transcripts (P nominal < .05) in the schizophrenia group when compared to controls. Bioinformatic analyses conducted on a subset of 293 genes (P nominal < .01 and |log2 FC| > 0.5) highlighted immune/inflammatory responses as key biological processes in our dataset. Differentially expressed genes in lymphocytes were highly enriched in gene expression profiles associated with cortex layer 5a and immune cells. Thus, we investigated whether the changes in transcripts levels observed in lymphocytes could also be detected in the prefrontal cortex (PFC, BA10) in a second replication cohort of schizophrenia subjects. Remarkably, mRNA levels detected in the PFC and lymphocytes were in strong agreement, and measurements obtained using RNA-sequencing positively correlated with data obtained by reverse transcriptase-quantitative polymerase chain reaction analysis. Collectively, our work supports a role for immune dysfunction in the pathogenesis of schizophrenia and suggests that peripheral markers can be used as accessible surrogates to investigate putative central nervous system disruptions.

LSD Administered as a Single Dose Reduces Alcohol Consumption in C57BL/6J Mice

There is a substantive clinical literature on classical hallucinogens, most commonly lysergic acid diethylamide (LSD) for the treatment of alcohol use disorder. However, there has been no published research on the effect of LSD on alcohol consumption in animals. This study evaluated the effect of LSD in mice using a two-bottle choice alcohol drinking paradigm. Adult male C57BL/6J mice were exposed to ethanol to develop preference and divided into three groups of equal ethanol consumption, and then treated with single intraperitoneal injection of saline or 25 or 50 μg/kg LSD and offered water and 20% ethanol. The respective LSD-treated groups were compared to the control group utilizing a multilevel model for repeated measures. In mice treated with 50 μg/kg LSD ethanol consumption was reduced relative to controls (p = 0.0035), as was ethanol preference (p = 0.0024), with a group mean reduction of ethanol consumption of 17.9% sustained over an interval of 46 days following LSD administration. No significant effects on ethanol consumption or preference were observed in mice treated with 25 μg/kg LSD. Neither total fluid intake nor locomotor activity in the LSD-treated groups differed significantly from controls. These results suggest that classical hallucinogens in the animal model merit further study as a potential approach to the identification of targets for drug discovery and investigation of the neurobiology of addiction.

Neurofilament light interaction with GluN1 modulates neurotransmission and schizophrenia-associated behaviors

Neurofilament (NFL) proteins have recently been found to play unique roles in synapses. NFL is known to interact with the GluN1 subunit of N-methyl-D-aspartic acid (NMDAR) and be reduced in schizophrenia though functional consequences are unknown. Here we investigated whether the interaction of NFL with GluN1 modulates synaptic transmission and schizophrenia-associated behaviors. The interaction of NFL with GluN1 was assessed by means of molecular, pharmacological, electrophysiological, magnetic resonance spectroscopy (MRS), and schizophrenia-associated behavior analyses. NFL deficits cause an NMDAR hypofunction phenotype including abnormal hippocampal function, as seen in schizophrenia. NFL-/- deletion in mice reduces dendritic spines and GluN1 protein levels, elevates ubiquitin-dependent turnover of GluN1 and hippocampal glutamate measured by MRS, and depresses hippocampal long-term potentiation. NMDAR-related behaviors are also impaired, including pup retrieval, spatial and social memory, prepulse inhibition, night-time activity, and response to NMDAR antagonist, whereas motor deficits are minimal. Importantly, partially lowering NFL in NFL+/- mice to levels seen regionally in schizophrenia, induced similar but milder NMDAR-related synaptic and behavioral deficits. Our findings support an emerging view that central nervous system neurofilament subunits including NFL in the present report, serve distinctive, critical roles in synapses relevant to neuropsychiatric diseases.

Rodent Mismatch Negativity/theta Neuro-Oscillatory Response as a Translational Neurophysiological Biomarker for N-Methyl-D-Aspartate Receptor-Based New Treatment Development in Schizophrenia

Deficits in the generation of auditory mismatch negativity (MMN) generation are among the most widely replicated neurophysiological abnormalities in schizophrenia and are linked to underlying dysfunction of N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission. Here, we evaluate physiological properties of rodent MMN, along with sensitivity to NMDAR agonist and antagonist treatments, relative to known patterns of dysfunction in schizophrenia. Epidural neurophysiological responses to frequency and duration deviants, along with responses to standard stimuli, were obtained at baseline and following 2 and 4 weeks' treatment in rats treated with saline, phencyclidine (PCP, 15 mg/kg/d by osmotic minipump), or PCP+glycine (16% by weight diet) interventions. Responses were analyzed using both event-related potential (ERP) and neuro-oscillatory (evoked power) approaches. At baseline, rodent duration MMN was associated with increased theta (θ)-frequency response similar to that observed in humans. PCP significantly reduced rodent duration MMN (p<0.001) and θ-band (p<0.01) response. PCP effects were prevented by concurrent glycine treatment (p<0.01 vs PCP alone). Effects related to stimulus-specific adaptation (SSA) were observed primarily in the alpha (α) and beta (β) frequency ranges. PCP treatment also significantly reduced α-frequency response to standard stimuli while increasing θ-band response, reproducing the pattern of deficit observed in schizophrenia. Overall, we demonstrate that rodent duration MMN shows neuro-oscillatory signature similar to human MMN, along with sensitivity to the NMDAR antagonist and agonist administration. These findings reinforce recent human studies linking MMN deficits to θ-band neuro-oscillatory dysfunction and support utility of rodent duration MMN as a translational biomarker for investigation of mechanisms underlying impaired local circuit function in schizophrenia.

Cannabinoid-1 receptor neutral antagonist reduces binge-like alcohol consumption and alcohol-induced accumbal dopaminergic signaling

Binge alcohol (ethanol) drinking is associated with profound adverse effects on our health and society. Rimonabant (SR141716A), a CB1 receptor inverse agonist, was previously shown to be effective for nicotine cessation and obesity. However, studies using rimonabant were discontinued as it was associated with an increased risk of depression and anxiety. In the present study, we examined the pharmacokinetics and effects of AM4113, a novel CB1 receptor neutral antagonist on binge-like ethanol drinking in C57BL/6J mice using a two-bottle choice drinking-in-dark (DID) paradigm. The results indicated a slower elimination of AM4113 in the brain than in plasma. AM4113 suppressed ethanol consumption and preference without having significant effects on body weight, ambulatory activity, preference for tastants (saccharin and quinine) and ethanol metabolism. AM4113 pretreatment reduced ethanol-induced increase in dopamine release in nucleus accumbens. Collectively, these data suggest an important role of CB1 receptor-mediated regulation of binge-like ethanol consumption and mesolimbic dopaminergic signaling, and further points to the potential utility of CB1 neutral antagonists for the treatment of binge ethanol drinking.

Modulating NMDA Receptor Function with D-Amino Acid Oxidase Inhibitors: Understanding Functional Activity in PCP-Treated Mouse Model

Deficits in N-methyl-D-aspartate receptor (NMDAR) function are increasingly linked to persistent negative symptoms and cognitive deficits in schizophrenia. Accordingly, clinical studies have been targeting the modulatory site of the NMDA receptor, based on the decreased function of NMDA receptor, to see whether increasing NMDA function can potentially help treat the negative and cognitive deficits seen in the disease. Glycine and D-serine are endogenous ligands to the NMDA modulatory site, but since high doses are needed to affect brain levels, related compounds are being developed, for example glycine transport (GlyT) inhibitors to potentially elevate brain glycine or targeting enzymes, such as D-amino acid oxidase (DAAO) to slow the breakdown and increase the brain level of D-serine. In the present study we further evaluated the effect of DAAO inhibitors 5-chloro-benzo[d]isoxazol-3-ol (CBIO) and sodium benzoate (NaB) in a phencyclidine (PCP) rodent mouse model to see if the inhibitors affect PCP-induced locomotor activity, alter brain D-serine level, and thereby potentially enhance D-serine responses. D-Serine dose-dependently reduced the PCP-induced locomotor activity at doses above 1000 mg/kg. Acute CBIO (30 mg/kg) did not affect PCP-induced locomotor activity, but appeared to reduce locomotor activity when given with D-serine (600 mg/kg); a dose that by itself did not have an effect. However, the effect was also present when the vehicle (Trappsol(®)) was tested with D-serine, suggesting that the reduction in locomotor activity was not related to DAAO inhibition, but possibly reflected enhanced bioavailability of D-serine across the blood brain barrier related to the vehicle. With this acute dose of CBIO, D-serine level in brain and plasma were not increased. Another weaker DAAO inhibitor NaB (400 mg/kg), and NaB plus D-serine also significantly reduced PCP-induced locomotor activity, but without affecting plasma or brain D-serine level, arguing against a DAAO-mediated effect. However, NaB reduced plasma L-serine and based on reports that NaB also elevates various plasma metabolites, for example aminoisobutyric acid (AIB), a potential effect via the System A amino acid carrier may be involved in the regulation of synaptic glycine level to modulate NMDAR function needs to be investigated. Acute ascorbic acid (300 mg/kg) also inhibited PCP-induced locomotor activity, which was further attenuated in the presence of D-serine (600 mg/kg). Ascorbic acid may have an action at the dopamine membrane carrier and/or altering redox mechanisms that modulate NMDARs, but this needs to be further investigated. The findings support an effect of D-serine on PCP-induced hyperactivity. They also offer suggestions on an interaction of NaB via an unknown mechanism, other than DAAO inhibition, perhaps through metabolomic changes, and find unexpected synergy between D-serine and ascorbic acid that supports combined NMDA glycine- and redox-site intervention. Although mechanisms of these specific agents need to be determined, overall it supports continued glutamatergic drug development.

Varenicline Effects on Smoking, Cognition, and Psychiatric Symptoms in Schizophrenia: A Double-Blind Randomized Trial

Schizophrenic patients have a high rate of smoking and cognitive deficits which may be related to a decreased number or responsiveness of nicotinic receptors in their brains. Varenicline is a partial nicotinic agonist which is effective as an antismoking drug in cigarette smokers, although concerns have been raised about potential psychiatric side-effects. We conducted a double-blind placebo controlled study in 87 schizophrenic smokers to evaluate the effects of varenicline (2 mg/day) on measures of smoking, cognition, psychiatric symptoms, and side-effects in schizophrenic patients who were cigarette smokers. Varenicline significantly decreased cotinine levels (P<0.001), and other objective and subjective measures of smoking (P < .01), and responses on a smoking urges scale (P = .02), more than placebo. Varenicline did not improve scores on a cognitive battery designed to test the effect of drugs on cognitive performance in schizophrenia (the MATRICS battery), either in overall MATRICS battery Composite or individual Domain scores, more than placebo. There were no significant differences between varenicline vs. placebo effects on total symptom scores on psychiatric rating scales, PANSS, SANS, or Calgary Depression scales, and there were no significant drug effects in any of these scales sub-scores when we used Benjamin-Hochberg corrected significance levels (α = .05). Varenicline patients did not show greater side-effects than placebo treated patients at any time point when controlled for baseline side-effect scores. Our study supports the use of varenicline as a safe drug for smoking reduction in schizophrenia but not as a cognitive enhancer.

TRIAL REGISTRATION

ClinicalTrials.gov 00802919.

Effects of transcranial direct current stimulation (tDCS) on cognition, symptoms, and smoking in schizophrenia: A randomized controlled study

Schizophrenia is characterized by cognitive deficits which persist after acute symptoms have been treated or resolved. Transcranial direct current stimulation (tDCS) has been reported to improve cognition and reduce smoking craving in healthy subjects but has not been as carefully evaluated in a randomized controlled study for these effects in schizophrenia. We conducted a randomized double-blind, sham-controlled study of the effects of 5 sessions of tDCS (2 milliamps for 20minutes) on cognition, psychiatric symptoms, and smoking and cigarette craving in 37 outpatients with schizophrenia or schizoaffective disorder who were current smokers. Thirty subjects provided evaluable data on the MATRICS Consensus Cognitive Battery (MCCB), with the primary outcome measure, the MCCB Composite score. Active compared to sham tDCS subjects showed significant improvements after the fifth tDCS session in MCCB Composite score (p=0.008) and on the MCCB Working Memory (p=0.002) and Attention-Vigilance (p=0.027) domain scores, with large effect sizes. MCCB Composite and Working Memory domain scores remained significant at Benjamini-Hochberg corrected significance levels (α=0.05). There were no statistically significant effects on secondary outcome measures of psychiatric symptoms (PANSS scores), hallucinations, cigarette craving, or cigarettes smoked. The positive effects of tDCS on cognitive performance suggest a potential efficacious treatment for cognitive deficits in partially recovered chronic schizophrenia outpatients that should be further investigated.

Neurofilament subunits are integral components of synapses and modulate neurotransmission and behavior in vivo

Synaptic roles for neurofilament (NF) proteins have rarely been considered. Here, we establish all four NF subunits as integral resident proteins of synapses. Compared with the population in axons, NF subunits isolated from synapses have distinctive stoichiometry and phosphorylation state, and respond differently to perturbations in vivo. Completely eliminating NF proteins from brain by genetically deleting three subunits (α-internexin, NFH and NFL) markedly depresses hippocampal long-term potentiation induction without detectably altering synapse morphology. Deletion of NFM in mice, but not the deletion of any other NF subunit, amplifies dopamine D1-receptor-mediated motor responses to cocaine while redistributing postsynaptic D1-receptors from endosomes to plasma membrane, consistent with a specific modulatory role of NFM in D1-receptor recycling. These results identify a distinct pool of synaptic NF subunits and establish their key role in neurotransmission in vivo, suggesting potential novel influences of NF proteins in psychiatric as well as neurological states.

DNA-methylation gene network dysregulation in peripheral blood lymphocytes of schizophrenia patients

The epigenetic dysregulation of the brain genome associated with the clinical manifestations of schizophrenia (SZ) includes altered DNA promoter methylation of several candidate genes. We and others have reported that two enzymes that belong to the DNA-methylation/demethylation network pathways-DNMT1 (DNA-methyltransferase) and ten-eleven translocator-1(TET1) methylcytosine deoxygenase are abnormally increased in corticolimbic structures of SZ postmortem brain. The objective of this study was to investigate whether the expression of these components of the DNA-methylation-demethylation pathways known to be altered in the brain of SZ patients are also altered in peripheral blood lymphocytes (PBL). The data show that increases in DNMT1 and TET1 and in glucocorticoid receptor (GCortR) and brain derived neurotrophic factor (BDNF) mRNAs in PBL of SZ patients are comparable to those reported in the brain of SZ patients. The finding that the expressions of DNMT1 and TET1 are increased and SZ candidate genes such as BDNF and GCortR are altered in the same direction in both the brain and PBL together with recent studies showing highly correlated patterns of DNA methylation across the brain and blood, support the hypothesis that a common epigenetic dysregulation may be operative in the brain and peripheral tissues of SZ patients.

Astrocyte origin of activity-dependent release of ATP and glutamate in hippocampal slices: real-time measurement utilizing microelectrode biosensors

It is well known that astrocytic and neuronal transmitter release processes are important for signalling, and that activity-dependent release of adenosine nucleotides and transmitters occurs after stimulation. Neurons and astrocytes can account for the source of ATP efflux. In this issue of the BJP, Heinrich et al. characterized K(+) depolarization-evoked release of ATP, adenosine and glutamate in hippocampal slices, utilizing microelectrode biosensors for simultaneous real-time recordings of multiple transmitter effluxes. They demonstrated efflux of ATP, adenosine and glutamate from hippocampus slices, in response to K(+) -depolarization, with distinct kinetics and mechanisms, suggesting a coordinated pattern of transmitter release. Surprisingly, it turned out that a considerable amount of the transmitter efflux measured under these conditions had a glial origin. For a long time, it was believed that the glial cell did not play a major role in neurotransmission, but the latter results somewhat change this view. The release of ATP and glutamate from glial cells under these conditions involved P2X7 receptors, and a source of adenosine accumulation independent of the metabolism of extracellular ATP was identified. This study also highlighted a novel use of multi-enzymatic microelectrode biosensors, which enabled a better characterization of transmitter release processes with higher temporal and spatial resolution than obtained previously. This technique was originally developed and used for the detection of purine release. In the present study, it was modified to identify the interplay between different transmitters, measured simultaneously in hippocampal slices.

Functional connectivity fMRI in mouse brain at 7T using isoflurane

Although many resting state fMRI human studies have been published, the number of such rodent studies is considerably less. The reason for this is the severe technical challenge of high magnetic field small rodent imaging. Local magnetic field susceptibility changes at air tissue boundaries cause image distortion and signal losses. The current study reports measures of functional connectivity in mice using only isoflurane for the anesthetic. Because all anesthetic agents will alter cerebral blood flow and cerebral metabolism, the impact these changes have on neuronal connectivity has yet to be fully understood, however this work reports for the first time that reliable functional connectivity measures in mouse brain can be obtained with isoflurane.

Effects of novel, high affinity glycine transport inhibitors on frontostriatal dopamine release in a rodent model of schizophrenia

Dopaminergic hyperactivity within frontostriatal brain systems is a key feature of schizophrenia, and an objective neural correlate of positive schizophrenia symptoms. N-methyl-d-aspartate (NMDA) receptors are known to play a prominent role in regulation of frontostriatal dopamine release. Furthermore, disturbances in glutamatergic function are increasingly being linked to pathophysiology of both positive and negative symptoms of schizophrenia. Prior studies have demonstrated that subchronic continuous administration of the NMDA antagonist phencyclidine (PCP) induces schizophrenia-like hyper-reactivity of frontostriatal dopamine release to amphetamine (AMPH) in rodents, and that effects were reversed by glycine and the prototypic glycine transport inhibitor (GTI) NFPS. The present study investigates effectiveness of the novel, high affinity and well tolerated GTIs, R231857, R231860 and Org29335, to reverse schizophrenia-like enhancement of AMPH-induced DA release, along with effects of the partial glycine-site agonist d-cycloserine. As previously, PCP had no significant effect on basal DA levels, but significantly enhanced AMPH-induced DA release in prefrontal cortex. All GTIs tested, as well as d-cycloserine, significantly reduced PCP-induced enhancement of DA release in prefrontal cortex. Neither PCP nor GTIs significantly affected striatal DA release. Overall, these findings suggest that treatments which target the glycine modulatory site of the NMDA receptor may significantly reverse NMDA receptor antagonist-induced dysregulation of frontal DA systems, consistent with potential beneficial effects on positive-, in addition to negative-, symptoms of schizophrenia.

Novel C-1 substituted cocaine analogs unlike cocaine or benztropine

Despite a wealth of information on cocaine-like compounds, there is no information on cocaine analogs with substitutions at C-1. Here, we report on (R)-(-)-cocaine analogs with various C-1 substituents: methyl (2), ethyl (3), n-propyl (4), n-pentyl (5), and phenyl (6). Analog 2 was equipotent to cocaine as an inhibitor of the dopamine transporter (DAT), whereas 3 and 6 were 3- and 10-fold more potent, respectively. None of the analogs, however, stimulated mouse locomotor activity, in contrast to cocaine. Pharmacokinetic assays showed compound 2 occupied mouse brain rapidly, as cocaine itself; moreover, 2 and 6 were behaviorally active in mice in the forced-swim test model of depression and the conditioned place preference test. Analog 2 was a weaker inhibitor of voltage-dependent Na+ channels than cocaine, although 6 was more potent than cocaine, highlighting the need to assay future C-1 analogs for this activity. Receptorome screening indicated few significant binding targets other than the monoamine transporters. Benztropine-like "atypical" DAT inhibitors are known to display reduced cocaine-like locomotor stimulation, presumably by their propensity to interact with an inward-facing transporter conformation. However, 2 and 6, like cocaine, but unlike benztropine, exhibited preferential interaction with an outward-facing conformation upon docking in our DAT homology model. In summary, C-1 cocaine analogs are not cocaine-like in that they are not stimulatory in vivo. However, they are not benztropine-like in binding mechanism and seem to interact with the DAT similarly to cocaine. The present data warrant further consideration of these novel cocaine analogs for antidepressant or cocaine substitution potential.

Ibogaine and the inhibition of acetylcholinesterase

ETHNOPHARMACOLOGICAL RELEVANCE

Ibogaine is a psychoactive monoterpine indole alkaloid extracted from the root bark of Tabernanthe iboga Baill. that is used globally in medical and nonmedical settings to treat drug and alcohol addiction, and is of interest as an ethnopharmacological prototype for experimental investigation and pharmaceutical development. The question of whether ibogaine inhibits acetylcholinesterase (AChE) is of pharmacological and toxicological significance.

MATERIALS AND METHODS

AChE activity was evaluated utilizing reaction with Ellman's reagent with physostigmine as a control.

RESULTS

Ibogaine inhibited AChE with an IC(50) of 520±40 μM.

CONCLUSIONS

Ibogaine's inhibition of AChE is physiologically negligible, and does not appear to account for observations of functional effects in animals and humans that might otherwise suggest the possible involvement of pathways linked to muscarinic acetylcholine transmission.

Nicotine: alcohol reward interactions

It is well established that the continued intake of drugs of abuse is reinforcing-that is repeated consumption increases preference. This has been shown in some studies to extend to other drugs of abuse; use of one increases preference for another. In particular, the present review deals with the interaction of nicotine and alcohol as it has been shown that smoking is a risk factor for alcoholism and alcohol use is a risk factor to become a smoker. The review discusses changes in the brain caused by chronic nicotine and chronic alcohol intake to approach the possible mechanisms by which one drug increases the preference for another. Chronic nicotine administration was shown to affect nicotine receptors in the brain, affecting not only receptor levels and distribution, but also receptor subunit composition, thus affecting affinity to nicotine. Other receptor systems are also affected among others catecholamine, glutamate, GABA levels and opiate and cannabinoid receptors. In addition to receptor systems and transmitters, there are endocrine, metabolic and neuropeptide changes as well induced by nicotine. Similarly chronic alcohol intake results in changes in the brain, in multiple receptors, transmitters and peptides as discussed in this overview and also illustrated in the tables. The changes are sex and age-dependent-some changes in males are different from those in females and in general adolescents are more sensitive to drug effects than adults. Although nicotine and alcohol interact-not all the changes induced by the combined intake of both are additive-some are opposing. These opposing effects include those on locomotion, acetylcholine metabolism, nicotine binding, opiate peptides, glutamate transporters and endocannabinoid content among others. The two compounds lower the negative withdrawal symptoms of each other which may contribute to the increase in preference, but the mechanism by which preference increases-most likely consists of multiple components that are not clear at the present time. As the details of induced changes of nicotine and alcohol differ, it is likely that the mechanisms of increasing nicotine preference may not be identical to that of increasing alcohol preference. Stimulation of preference of yet other drugs may again be different -representing one aspect of drug specificity of reward mechanisms.

Differences between nicotine and cocaine-induced conditioned place preferences

In previous studies, we found differences between nicotine and cocaine-induced changes in the levels of neurotransmitters in various brain areas, which suggested differences in their reward - preference mechanisms. The present study was based on the idea that drug preference is modulated by a number of different factors, among them several neurotransmitters and their receptors, and antagonists of specific receptors will influence preference. We also assumed that the factors (components of reward mechanisms) involved are different in the case of different drugs. We compared the inhibition of nicotine preference with cocaine preference. We assayed preference as conditioned place preference (CPP) and measured CPP inhibition by receptor subtype antagonists using mice. In general, induced CPP of cocaine was stronger than of nicotine as shown by more time spent in the nonpreferred area after conditioning with cocaine. We measured inhibition by four antagonists: mecamylamine, atropine, SCH23390, and phentolamine: antagonists respectively of nicotinic, and muscarinic acetylcholine, dopamine D1, and alpha noradrenergic receptors. The inhibition by the antagonists of cocaine CPP was lower in most instances than that of nicotine CPP. Atropine and SCH23390 inhibited nicotine and cocaine CPP approximately to the same degree, while the inhibition by mecamylamine and phentolamine of nicotine CPP was 100%; that of cocaine was 20% and 0, respectively. We conclude that several receptor systems and transmitters play a role in drug preference, some represent essential elements or circuits, some may be only required partially or their role can be partially substituted. The composition of such systems is different for different drugs - in the present study, some of the components influencing CPP are different for nicotine as opposed to cocaine.

An upregulation of DNA-methyltransferase 1 and 3a expressed in telencephalic GABAergic neurons of schizophrenia patients is also detected in peripheral blood lymphocytes

Several lines of schizophrenia (SZ) research suggest that a functional downregulation of the prefrontal cortex GABAergic neuronal system is mediated by a promoter hypermethylation, presumably catalyzed by an increase in DNA-methyltransferase-1 (DNMT-1) expression. This promoter hypermethylation may be mediated not only by DNMT-1 but also by an entire family of de novo DNA-methyltransferases, such as DNA-methyltransferase-3a (DNMT-3a) and -3b (DNMT-3b). To verify the existence of an overexpression of DNMT-3a and DNMT-3b in the brain of schizophrenia patients (SZP), we compared their mRNA expression in Brodmann's area 10 (BA10) and in the caudate nucleus and putamen obtained from the Harvard Brain Tissue Resource Center (Belmont, MA) from both nonpsychiatric subjects (NPS) and SZP. Our results demonstrate that DNMT-3a and DNMT-1 are expressed and co-localize in distinct GABAergic neuron populations whereas DNMT-3b mRNA is virtually undetectable. We also found that unlike DNMT-1, which is frequently overexpressed in telencephalic GABAergic neurons of SZP, DNMT-3a mRNA is overexpressed only in layer I and II GABAergic interneurons of BA10. To ascertain whether these DNMT expression differences observed in brain tissue could also be detected in peripheral tissues, we studied whether DNMT-1 and DNMT-3a mRNAs were overexpressed in peripheral blood lymphocytes (PBL) of SZP. Both DNMT-1 and DNMT-3a mRNAs are expressed in the PBL and although DNMT-3a mRNA levels in the PBL are approximately 1/10 of those of DNMT-1, the comparison of the PBL content in NPS and SZP showed a highly significant 2-fold increase of both DNMT-1 and DNMT-3a mRNA in SZP. These changes were unaffected by the dose, the duration, or the type of antipsychotic treatment. The upregulation of DNMT-1 and to a lesser extent that of DNMT-3a mRNA in PBL of SZP supports the concept that this readily available peripheral cell type can express an epigenetic variation of specific biomarkers relevant to SZ morbidity. Hence, PBL studies may become useful to investigate a diagnostic epigenetic marker of SZ morbidity.

Cognitive and antismoking effects of varenicline in patients with schizophrenia or schizoaffective disorder

OBJECTIVE

Varenicline has been shown to be an effective anti-smoking treatment in smokers without identified psychiatric illness, and the drug's pharmacology suggests possibilities of pro-cognitive effects. However, recent reports suggest varenicline may have the potential for important psychiatric side-effects in some people. We present the first prospective quantitative data on the effects of varenicline on cognitive function, cigarette smoking, and psychopathology in a small sample of schizophrenic patients.

METHOD

Fourteen schizophrenic smokers were enrolled in an open-label study of varenicline with a pre-post design. Measures of cognitive function (RBANS, Virtual Water-Maze Task), cigarette smoking (cotinine levels, CO levels, self-reported smoking and smoking urges), and psychopathology (PANSS) were evaluated prior to and during treatment with varenicline. Data on psychopathology changes among schizophrenic smokers in another drug study, in which patients were not receiving varenicline, were used for comparison.

RESULTS

12 patients completed the study, and 2 patients terminated in the first two weeks of active varenicline because of complaints of nausea or shaking. Varenicline produced significant improvements in some cognitive test scores, primarily associated with verbal learning and memory, but not in scores on visual-spatial learning or memory, or attention. Varenicline significantly decreased all indices of smoking, but did not produce complete smoking abstinence in most patients. During treatment with varenicline there were no significant increases in psychopathology scores and no patient developed signs of clinical depression or suicidal ideation.

CONCLUSIONS

Our small prospective study suggests that treatment with varenicline appears to have some beneficial cognitive effects which need to be confirmed in larger studies with additional neuropsychological tests. Varenicline appears to have some anti-smoking efficacy in schizophrenia but longer studies are needed to determine whether it will produce rates of smoking abstinence similar to those found in control smokers. Treatment with varenicline may not increase psychopathology or depression in most patients with schizophrenia, but we cannot accurately estimate the absolute risk of a potentially rare side-effect from this small sample.

GABAB/NMDA receptor interaction in the regulation of extracellular dopamine levels in rodent prefrontal cortex and striatum

Deficits in N-methyl-D-aspartate receptor (NMDAR)-mediated neurotransmission may underlie dopaminergic hyperactivity in schizophrenia. Dysregulation of the GABAergic system has also been implicated. In this study we investigated a role for GABA(B) receptors as an intermediate step in the pathway leading from NMDAR stimulation to DA regulation. Since glycine (GLY) has been found to ameliorate treatment resistant negative symptoms in schizophrenia, we treated a group of rats with 16% GLY food for 2 weeks. DA levels in prefrontal cortex (PFC) and striatum (STR) were assessed by dual-probe microdialysis and HPLC-EC in freely moving rats. Infusion of the GABA(B) receptor agonists SKF97541 and baclofen into PFC and STR significantly reduced basal DA, an effect that was reversed by the antagonist, CGP52432. In PFC, GABA(B) agonists also reduced AMPH-induced DA release following treatment with either 1 or 5 mg/kg AMPH. Similar effects were seen following subchronic glycine treatment in the absence, but not presence of CGP52432 during 5 mg/kg AMPH treatment. In STR SKF97541 decreased only the 1 mg/kg AMPH-induced DA release. Subchronic GLY treatment in STR leads to a significant reduction in basal DA levels, but did not affect AMPH (5 mg/kg)-induced release. Our findings support a model in which NMDA/glycine-site agonists modulate DA release in part through presynaptic GABA(B) receptors on DA terminals, with both GABA(B) ligands and GLY significantly modulating AMPH-induced DA release. Both sites, therefore, may represent appropriate targets for drug development in schizophrenia and substance abuse disorders.

Characterization of interactions between phencyclidine and amphetamine in rodent prefrontal cortex and striatum: Implications in NMDA/glycine-site-mediated dopaminergic dysregulation and dopamine transporter function

N-Methyl-D-aspartate (NMDA) antagonists induced behavioral and neurochemical changes in rodents that serve as animal models of schizophrenia. Chronic phencyclidine (PCP, 15 mg/(kg day) for 3 weeks via Alzet osmotic pump) administration enhances the amphetamine (AMPH)-induced dopamine (DA) efflux in prefrontal cortex (PFC), similar to that observed in schizophrenia. NMDA/glycine-site agonists, such as glycine (GLY), administered via dietary supplementation, reverse the enhanced effect. The present study investigated mechanisms of glycine-induced reversal of PCP-induced stimulation of AMPH-induced DA release, using simultaneous measurement of DA and AMPH in brain microdialysate, as well as peripheral and tissue AMPH levels. PCP treatment, by itself, increased peripheral and central AMPH levels, presumably via interaction with hepatic enzymes (e.g. cytochrome P450 CYP2C11). GLY (16% diet) had no effect on peripheral AMPH levels in the presence of PCP. Nevertheless, GLY significantly reduced extracellular/tissue AMPH ratios in both PFC and striatum (STR), especially following PCP administration, suggesting a feedback mediated effect on the dopamine transporter. GLY also inhibited acute AMPH (5 mg/kg)-induced DA release in PFC, but not STR. These findings suggest that GLY may modulate DA release in brain by producing feedback regulation of dopamine transporter function, possibly via potentiation of NMDA-stimulated GABA release and presynaptic GABAB receptor activation. The present studies also demonstrate pharmacokinetic interaction between AMPH and PCP, which may be of both clinical and research relevance.

Increased dopaminergic neuron sensitivity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in transgenic mice expressing mutant A53T alpha-synuclein

Familial Parkinson's disease (PD) has been linked to point mutations and duplication of the alpha-synuclein gene and mutant alpha-synuclein expression increases the vulnerability of neurons to exogenous insults. In this study, we analyzed the levels of dopamine and its metabolites in the olfactory bulb (OB), and nigrostriatal regions of transgenic mice expressing human, mutant A53T alpha-synuclein (alpha-syn tg) and their non-transgenic (ntg) littermates using a sub-toxic, moderate dose of MPTP to determine if mutant human alpha-synuclein sensitizes the central dopaminergic systems to oxidative stress. We observed that after a single, sub-lethal MPTP injection, dopamine levels were reduced in striatum and SN in both the alpha-syn tg and ntg mice. In the olfactory bulb, a region usually resistant to MPTP toxicity, levels were reduced only in the alpha-syn tg mice. In addition, we identified a significant increase in dopamine metabolism in the alpha-syn transgenic, but not ntg mice. Finally, MPTP treatment of alpha-syn tg mice was associated with a marked elevation in the oxidative product, 3-nitrotyrosine that co-migrated with alpha-synuclein. Cumulatively, the data support the hypothesis that mutant alpha-synuclein sensitizes dopaminergic neurons to neurotoxic insults and is associated with greater oxidative stress. The alpha-syn tg line is therefore useful to study the genetic and environmental inter-relationship in PD.

Food reward-induced neurotransmitter changes in cognitive brain regions

Recent evidence indicates that mechanisms involved in reward and mechanisms involved in learning interact, in that reward includes learning processes and learning includes reward processes. In spite of such interactions, reward and learning represent distinct functions. In the present study, as part of an examination of the differences in learning and reward mechanisms, it was assumed that food principally affects reward mechanisms. After a brief period of fasting, we assayed the release of three neurotransmitters and their associated metabolites in eight brain areas associated with learning and memory as a response to feeding. Using microdialysis for the assay, we found changes in the hippocampus, cortex, amygdala, and the thalamic nucleus, (considered cognitive areas), in addition to those in the nucleus accumbens and ventral tegmental area (considered reward areas). Extracellular dopamine levels increased in the nucleus accumbens, ventral tegmental area, amygdala, and thalamic nucleus, while they decreased in the hippocampus and prefrontal cortex. Dopamine metabolites increased in all areas tested (except the dorsal hippocampus); changes in norepinephrine varied with decreases in the accumbens, dorsal hippocampus, amygdala, and thalamic nucleus, and increases in the prefrontal cortex; serotonin levels decreased in all the areas tested; although its metabolite 5HIAA increased in two regions (the medial temporal cortex, and thalamic nucleus). Our assays indicate that in reward activities such as feeding, in addition to areas usually associated with reward such as the mesolimbic dopamine system, other areas associated with cognition also participate. Results also indicate that several transmitter systems play a part, with several neurotransmitters and several receptors involved in the response to food in a number of brain structures, and the changes in transmitter levels may be affected by metabolism and transport in addition to changes in release in a regionally heterogeneous manner. Food reward represents a complex pattern of changes in the brain that involve cognitive processes. Although food reward elements overlap with other reward systems sharing some neurotransmitter compounds, it significantly differs indicating a specific reward to process for food consumption. Like in other rewards, both learning and cognitive areas play a significant part in food reward.

The Effects of Glutamate and GABA Receptor Antagonists on Nicotine-induced Neurotransmitter Changes in Cognitive Areas*

In the present study, we tested the effects of glutamate and GABA receptor antagonists on nicotine-induced neurotransmitter changes in the hippocampal (dorsal and ventral) and cortical (medial temporal and prefrontal) brain areas of conscious freely moving rats via microdialysis. Both the antagonists and nicotine were administered intracerebrally. The antagonists tested were NMDA, AMPA-kainate, and metabotropic glutamate receptor subtype antagonists (MK801, CNQX, and LY 341495, respectively) and GABA(A) and GABA(B) receptor subtype antagonists (bicuculline and hydroxysaclofen, respectively). We assayed nicotine-induced changes in dopamine (DA), norepinephrine (NE), serotonin (5-HT), and their metabolites. We found with the antagonists, both decreases and increases in nicotine-induced neurotransmitter responses. In the presence of nicotine all the antagonists (except LY 341495) caused a decrease in DA levels in the regions tested. NE levels were decreased in the cortex by all antagonists. In the hippocampus, GABA antagonists decreased NE levels, as did the metabotropic glutamate antagonist, LY 341495, while the other glutamate antagonists increased NE levels. The results of the 5-HT assay were more variable and dependent on the region and antagonist examined; increases were found slightly more often than decreases. The changes in metabolites were not often parallel with changes in their associated neurotransmitters, indicating that the antagonists also affect the metabolism of the neurotransmitters. The effect of the antagonists in the absence of nicotine was mostly to decrease the level of neurotransmitters, although increases were seen in a few cases. The results suggest that the excitatory glutamatergic- and inhibitory GABAergic-amino acid receptors are both involved in mediating nicotine-induced neurotransmitter responses, and their inhibitory or stimulatory effects are receptor subtype and brain region dependent.

Changes in cerebral neurotransmitters and metabolites induced by acute donepezil and memantine administrations: A microdialysis study

Cholinesterase inhibitors including donepezil, rivastigmine, and galantamine and the N-methyl-D-aspartate (NMDA) antagonist, memantine are the medications currently approved for the treatment of Alzheimer's disease (AD). In addition to their beneficial effects on cognitive and functional domains typically disrupted in AD, these agents have also been shown to slow down the emergence of behavioral and psychotic symptoms associated with this disease. However, the underlying mechanisms for these therapeutic effects remain poorly understood and could involve effects of these medications on non-cholinergic or non-glutamatergic neurotransmitter systems respectively. These considerations prompted us to initiate a series of investigations to examine the acute and chronic effects of donepezil (Aricept (+/-)-2,3-dihydro-5,6-dimethoxy-2-[[1-(phenylmethyl)-4-piperidinyl]methyl]-1H-inden-1-1 hydrochloride and memantine (1-amino-3,5-dimethyladamantane hydrochloride C12H21N.HCl)). The present study focuses on the acute effects of donepezil and memantine on brain extracellular levels of acetylcholine, dopamine, serotonin, norepinephrine and their metabolites. We assayed changes in the ventral and dorsal hippocampus and the prefrontal and medial temporal cortex by microdialysis. Memantine resulted in significant increases in extracellular dopamine (DA), norepinephrine (NE), and their metabolites, in the cortical regions, and in a reduction of DA in the hippocampus. Donepezil produced an increase in extracellular DA in the cortex and in the dorsal hippocampus. Norepinephrine increased in the cortex; with donepezil it increased in the dorsal hippocampus and the medial temporal cortex, and decreased in the ventral hippocampus. Interestingly both compounds decreased extracellular serotonin (5HT) levels. The metabolites of the neurotransmitters were increased in most areas. We also found an increase in extracellular acetylcholine (ACh) by memantine in the nucleus accumbens and the ventral tegmental area. Our results suggest both region and drug specific neurotransmitter effects of these agents as well as some similarities. We conclude that drugs influencing cognitive mechanisms induce changes in a number of neurotransmitters with the changes being both region and drug specific. Release and metabolism are altered and extracellular neurotransmitter levels can be increased or decreased by the drugs. Other studies are in progress to determine the pharmacological effects associated with chronic treatment with these compounds, which may be more pertinent to the clinical situation in which patients take these medications for months or years.

The effects of cholinergic and dopaminergic antagonists on nicotine-induced cerebral neurotransmitter changes

In a continuing study of nicotine-induced mechanisms in brain areas associated with cognitive processes, the effects of cholinergic and dopaminergic antagonists on nicotine-induced changes in dopamine, norepinephrine, and serotonin were examined. These effects were measured via in vivo microdialysis in the dorsal and ventral hippocampus and in the prefrontal and medial temporal cortex of conscious, freely moving, adult male rats. Nicotine (0.3 mg/kg, free base) was administered subcutaneously and the antagonists were infused locally via the microdialysis probe. Nicotine alone induced an increase of dopamine and its metabolites in all areas, an increase of norepinephrine in the cortex, and an increase of the norepinephrine metabolite 4-hydroxy-3-methoxy-phenylglycol in all areas. Serotonin was decreased in the hippocampus and increased in the cortex. Nicotine-induced dopamine increases were inhibited by nicotinic (mecamylamine 100 microM, methyllycaconitine 500 microM), muscarinic (atropine 100 microM), and dopaminergic D1 (SCH23390 100 microM) and D2 (eticlopride 100 microM) antagonists, in the hippocampal and cortical areas. In the hippocampal areas, these antagonists had less significant effect on norepinephrine and serotonin. However, in the cortical areas, all antagonists inhibited the nicotine-induced increase of serotonin to varying degrees; and some, primarily nicotinic and dopamine D1 antagonists, inhibited the induced increase of norepinephrine. In the hippocampal and cortical areas, the mechanisms of nicotine-induced dopamine increase seem to be similar, but the mechanisms seem to be different for noradrenergic and serotonergic systems, as shown by the fact that nicotine induces no change in norepinephrine and a decrease in serotonin in the hippocampus, while it induces an increase in both in the cortex. Nicotine-induced dopamine release seems to be mediated, in part locally, by nicotinic and muscarinic receptors on dopaminergic cells. In contrast, nicotine's effect on norepinephrine and serotonin is at least partially mediated by initial changes at other than local sites, and through different receptors. Thus, the effects of nicotine and the mechanisms involved differ for different neurotransmitters and in different brain areas.

Locally Administered Low Nicotine-Induced Neurotransmitter Changes in Areas of Cognitive Function

The present study examined the effect of a low-dose of nicotine; below that one expects to be achieved from a single cigarette, on brain regional heterogeneity and sensitivity of catecholaminergic responses. 1 microM nicotine was infused into six brain areas via a microdialysis probe: the dorsal and ventral hippocampus, the medial temporal and prefrontal cortex, the basolateral amygdala, and the ventral tegmental area (VTA). The nicotine concentration in the brain tissue near the probe site was approximately 0.1 microM. Nicotine-induced increases and decreases could be noted in dopamine (DA), norepinephrine (NE), and serotonin (5HT) levels. In particular, DA and 5HT decreased in both hippocampal areas, while NE increased in the dorsal and decreased in the ventral hippocampus. In the cortical areas, DA and NE increased and 5HT was not significantly altered. In the amygdala all three neurotransmitters increased and in the VTA, all three decreased. Many of the nicotine-induced changes in neurotransmitter concentrations were reversed in the presence of atropine. Where nicotine induced decreases in DA and 5HT in the VTA, increases were observed in the presence of atropine. A similar reversal was seen with NE in the VTA and ventral hippocampus. In contrast, the increases in DA observed in the cortex and amygdala and the increases in NE observed in the cortex, amygdala and dorsal hippocampus were inhibited by the presence of atropine. 5HT was also significantly decreased in the amygdala and both cortical areas in the presence of atropine, where nicotine alone had no significant effect. We conclude, that at low doses, nicotine significantly alters the release of DA, NE, and 5HT--in some areas increasing, in others decreasing endogenous neurotransmitter levels. This data, in conjunction with previous experiments, indicates that the effects of nicotine are regionally heterogeneous and arise from both direct and indirect actions on various receptors and neurotransmitter systems and nicotine's effects at low doses differ from that at higher doses. The changes in effects in the presence of atropine suggest that muscarinic acetylcholine receptors play a major role in nicotine's actions on neurotransmitter systems.

Modulation of striatal dopamine release by glycine transport inhibitors

Traditional models of schizophrenia have focused primarily upon dopaminergic (DA) dysregulation. In contrast, more recent models focus on dysfunction of glutamatergic systems, acting particularly through N-methyl-D-aspartate (NMDA) receptors. NMDA receptors in brain are regulated by glycine, acting via a strychnine-insensitive regulatory site, and by glycine (GlyT1) transporters that maintain low glycine levels in the immediate vicinity of the NMDA receptor complex. The present study investigates the role of NMDA receptors in the modulation of striatal dopamine release in vitro, and of glycine transport inhibitors (GTIs) as potential psychotherapeutic agents in schizophrenia. In striatum, NMDA receptors exert dual excitatory/inhibitory effects, with inhibition reflecting activity of local GABAergic feedback regulation. We have previously demonstrated effectiveness of glycine in regulating [3H]DA release both in vivo and in vitro, consistent with its beneficial clinical effects. In the present study, similar effects were observed for the high-affinity GTI (+)N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy-)propyl]sarcosine (NFPS), and for a range of high-affinity GTIs with appropriate rank order of potency. In addition, (+)NFPS significantly stimulated NMDA-induced [3H]GABA release. Effects, of GTIs, were blocked by the glycine-site antagonists L689,560 and HA-966, and the GABA(B) antagonists phaclofen and CGP 52432, confirming the roles of both the NMDA-associated glycine-site and presynaptic GABA(B) receptors in NMDA receptor-mediated regulation of striatal DA release in vitro. Endogenous DA hyperactivity is associated with prominent positive symptoms in schizophrenia. The present results are consistent with recent clinical studies showing significant effectiveness of glycine-site agonists and GTIs in reduction of persistent positive, as well as negative, symptoms in schizophrenia.

Inhibition of system A-mediated glycine transport in cortical synaptosomes by therapeutic concentrations of clozapine: implications for mechanisms of action

Clozapine is an atypical antipsychotic with particular efficacy in schizophrenia, possibly related to potentiation of brain N-methyl-D-aspartate receptor (NMDAR) -mediated neurotransmission. NMDARs are regulated in vivo by glycine, which is regulated in turn by glycine transporters. The present study investigates transport processes regulating glycine uptake into rat brain synaptosomes, along with effects of clozapine on synaptosomal glycine transport. Amino-acid uptake of amino acids was assessed in rat brain P2 synaptosomal preparations using a radiotransport assay. Synaptosomal glycine transport was inhibited by a series of amino acids and by the selective System A antagonist MeAIB (2-methyl-aminoisobutyric acid). Clozapine inhibited transport of both glycine and MeAIB, but not other amino acids, at concentrations associated with preferential clinical response (0.5-1 microg/ml). By contrast, other antipsychotics studied were ineffective. The novel glycine transport inhibitor N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS) produced biphasic inhibition of [(3)H]glycine transport, with IC(50) values of approximately 25 nM and 25 microM, respectively. NFPS inhibition of [(3)H]MeAIB was monophasic with a single IC(50) value of 31 microM. Clozapine significantly inhibited [(3)H]glycine binding even in the presence of 100 nM NFPS. In conclusion, this study suggests first that System A transporters, or a subset thereof, may play a critical role in regulation of synaptic glycine levels and by extension of NMDA receptor regulation, and second that System A antagonism may contribute to the differential clinical efficacy of clozapine compared with other typical or atypical antipsychotics.

Regional Heterogeneity of Nicotine Effects on Neurotransmitters in Rat Brains in vivo at Low Doses

In our recent studies on nicotine-induced changes in neurotransmitters in brain areas associated with cognitive function using a nicotine dose of 0.5 mg/kg administered subcutaneously to conscious freely moving rats, we found changes in dopamine, norepinephrine, and serotonin, and their metabolites, in the areas examined. For the present report we examined changes in these neurotransmitters following administration of lower nicotine doses, to test regional differences in nicotine response and possible threshold levels for some effects of nicotine. The doses used were 0.15 mg/kg and 0.03 mg/kg nicotine administered subcutaneously. Nicotine levels in the brain reached peak values in less than 10 min and decreased with a half-life of about 60 min (0.15 mg/kg) or 30 min (0.03 mg/kg) to values below detection limits (1 ng/g), by the later time points of the 0.03 mg/kg experiments. Nicotine-induced dopamine (DA) increase (and increase in DA metabolites) and decrease in 5-HT levels at 0.15 mg/kg were significant in the cortex, less so in the hippocampus. Norepinephrine (NE) increase at 0.15 mg/ kg was much less significant than found previously at 0.5 mg/kg. At a low nicotine dose (0.03 mg/kg), the significant changes observed were a decrease in 5-HT in the hippocampus and small increases of DA and NE in the prefrontal cortex and of NE in the medial temporal cortex. In the nucleus accumbens DA, NE, and 5-HT and their metabolites in the ventral tegmental area, mostly DA and metabolites were increased. We conclude that in areas of cognitive function nicotine-induced DA changes are more concentration dependent than changes in NE or 5-HT, and that there are regional differences in neurotransmitter changes induced by nicotine, with NE changes detectable only in the cortex and 5-HT changes only in the hippocampus at a low nicotine dose, indicating significant regional variation in sensitivity to nicotine-induced neurotransmitter changes in brain areas associated with cognitive function. The decrease in 5-HT shows that nicotine also has indirect effects caused by neurotransmitters released by nicotine. The effects of a low nicotine dose are more significant in areas of reward function, indicating differences in sensitivity between cognitive and reward functions.

Nicotine-induced changes in neurotransmitter levels in brain areas associated with cognitive function

Nicotine, one of the most widespread drugs of abuse, has long been shown to impact areas of the brain involved in addiction and reward. Recent research, however, has begun to explore the positive effects that nicotine may have on learning and memory. The mechanisms by which nicotine interacts with areas of cognitive function are relatively unknown. Therefore, this paper is part of an ongoing study to evaluate regional effects of nicotine enhancement of cognitive function. Nicotine-induced changes in the levels of three neurotransmitters, dopamine (DA), serotonin (5-HT), norepinepherine (NE), their metabolites, homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), and their precursor, L-DOPA, were evaluated in the ventral and dorsal hippocampus (VH and DH), prefrontal and medial temporal cortex (PFC and MTC), and the ventral tegmental area (VTA) using in vivo microdialysis in awake, freely moving, male Sprague-Dawley rats. The animals were treated with acute nicotine (0.5 mg/kg, s.c.) halfway through the 300-min experimental period. The reuptake blockers, desipramine (100 microM) and fluoxetine (30 microM), were given to increase the levels of NE and 5-HT so that they could be detected. Overall, a nicotine-induced DA increase was found in some areas, and this increase was potentiated by desipramine and fluoxetine. The two DA metabolites, HVA and DOPAC, increased in all the areas throughout the experiments, both with and without the inhibitors, indicating a rapid metabolism of the released DA. The increase in these metabolites was greater than the increase in DA. 5-HT was increased in the DH, MTC, and VTA in the presence of fluoxetine; its metabolite, 5-HIAA, was increased in the presence and absence of fluoxetine. Except in the VTA, NE levels increased to a similar extent with desipramine and fluoxetine. Overall, nicotine appeared to increase the release and turnover of these three neurotransmitters, which was indicated by significant increases in their metabolites. Furthermore, DA, and especially HVA and DOPAC, increased for the 150 min following nicotine administration; 5-HT and NE changes were shorter in duration. As gas chromatography experiments showed that nicotine levels in the brain decreased by 75% after 150 min, this may indicate that DA is more susceptible to lower levels of nicotine than 5-HT or NE. In conclusion, acute nicotine administration caused alterations in the levels of DA, 5-HT, and NE, and in the metabolism of DA and 5-HT, in brain areas that are involved in cognitive processes.

Effects of acute lorazepam administration on aminergic activity in normal elderly subjects: relationship to performance effects and apolipoprotein genotype

The effects of acute lorazepam challenges on plasma (p) HVA, MHPG, and 5-HIAA, and their relationship to drug-induced cognitive and motor deficits and the apolipoprotein (APOE)-epsilon4 allele were examined. Eighteen healthy elderly (8 epsilon4 carriers) received placebo or acute oral lorazepam doses (0.5 mg or 1 mg) in random sequence, 1-week apart. Cognitive assessment and plasma levels of pHVA, pMHPG, and p5-HIAA were determined at baseline and at 1, 2.5, and 5 h postchallenge. There was no drug-to-placebo difference in monoamine levels and no consistent relationship between changes in monoamine levels and cognitive performance, regardless of epsilon4 status. However, the 1.0 mg dose increased p5-HIAA in epsilon4 carriers, whereas it caused a reduction in noncarriers. Higher baseline pMHPG and p5-HIAA levels were associated with better baseline memory. The epsilon4 allele may modulate the effect of lorazepam on p5-HIAA, but further studies are needed to confirm this finding and elucidate its possible significance.

Sensitive and simple gas chromatographic–mass spectrometric determination for amphetamine in microdialysate and ultrafiltrate samples

A gas chromatographic-mass spectrometric (GC-MS) method is described for the measurement of amphetamine (AMP) using negative chemical ionization (NCI) mode. Without prior extraction AMP was derivatized with 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) and simultaneously extracted into toluene. The toluene extract was injected directly into GC-MS equipped with a HP-1 capillary column. The method is simple and more sensitive than most of the previously published methods. The limit of quantification of amphetamine is 25pg (1.4pg on column) with a very limited sample volume (25microl). The within-day precision was from 1.7 to 5.1% and between-day precision was from 2.2 to 7.3%. The method has been used for the measurement of several thousand microdialysate and ultrafiltrate samples and proven reliable.

Reversal of phencyclidine-induced dopaminergic dysregulation by N-methyl-D-aspartate receptor/glycine-site agonists

N-methyl-D-aspartate (NMDA) receptors may play a critical role in the pathophysiology of schizophrenia. In rodents, NMDA receptor antagonists, such as phencyclidine (PCP), induce dopaminergic dysregulation that resembles the pattern observed in schizophrenia. The present study investigates the degree to which concurrent treatment with NMDA modulators, such as glycine and the recently developed glycine transport antagonist N[3-(4"-fluorophenyl)-3-(4"-phenylphenoxy)propyl]sarcosine (NFPS) prevents dopaminergic dysregulation observed following chronic (3 months) or subchronic (2 weeks) PCP administration. Both chronic and subchronic treatment with PCP in the absence of glycine or NFPS led to significant potentiation of amphetamine-induced dopamine release in the prefrontal cortex and striatum, similar to that observed in schizophrenia. Treatment with either high-dose glycine or NFPS along with PCP prevented PCP effects. These findings demonstrate effective doses of glycine for use in animal models of schizophrenia, and support recent clinical studies showing the effectiveness of NMDA agonists in the treatment of persistent symptoms of schizophrenia.

Subchronic continuous phencyclidine administration potentiates amphetamine-induced frontal cortex dopamine release

Functional dopaminergic hyperactivity is a key feature of schizophrenia. Etiology of this dopaminergic hyperactivity, however, is unknown. We have recently demonstrated that subchronic phencyclidine (PCP) treatment in rodents induces striatal dopaminergic hyperactivity similar to that observed in schizophrenia. The present study investigates the ability of PCP to potentiate amphetamine-induced dopamine release in prefrontal cortex (PFC) and nucleus accumbens (NAc) shell. Prefrontal dopaminergic hyperactivity is postulated to underlie cognitive dysfunction in schizophrenia. In contrast, the degree of NAc involvement is unknown and recent studies have suggested that PCP-induced hyperactivity in rodents may correlate with PFC, rather than NAc, dopamine levels. Rats were treated with 5-20 mg/kg/day PCP for 3-14 days by osmotic minipump. PFC and NAc dopamine release to amphetamine challenge (1 mg/kg) was monitored by in vivo microdialysis and HPLC-EC. Doses of 10 mg/kg/day and above produced serum PCP concentrations (50-150 ng/ml) most associated with PCP psychosis in humans. PCP-treated rats showed significant, dose-dependent enhancement in amphetamine-induced dopamine release in PFC but not NAc, along with significantly enhanced locomotor activity. Enhanced response was observed following 3-day, as well as 14-day, treatment and resolved within 4 days of PCP treatment withdrawal. These findings support the concept that endogenous NMDA receptor dysfunction could account for the pattern of dopaminergic dysfunction observed in schizophrenia, and suggest that even short duration abuse of PCP-like agents may greatly potentiate behavioral effects of psychostimulants in drug abuse situations. Finally, these studies provide a model system in which to evaluate effects of potential psychotherapeutic agents.

Strain and sex differences in repeated ethanol treatment-induced motor activity in quasi-congenic mice

The B6.C quasi-congenic Recombinant QTL Introgression (RQI) strains of the b4i5 series have similar genetic background, but differ in about 5% of their genome from the C57BL/6ByJ (B6) background strain because they carry short chromosome segments introgressed from the BALB/cJ (C) donor strain. These RQI strains were derived from mouse lines selectively bred for high activity of mesencephalic tyrosine hydroxylase (TH/MES), therefore genetic variation in dopamine system-related behaviours, such as ethanol-induced motor activity, can be expected. Males and females of 17 RQI and two progenitor strains were tested for initial motor activity for 15 min after a habituating injection of saline, which was followed by an i.p. injection of saline or ethanol (2 g/kg) and an additional test of motor activity for 30 min. This procedure was repeated during 4 subsequent days. In all strains, the first-day ethanol treatment showed an inhibitory effect. With repetition of the treatment the inhibitory effect decreased, and a stimulatory effect could be observed with significant strain- and sex-dependent variation. Females exhibited higher activity in the saline group than males, and reached an equilibrium of inhibition and stimulation sooner than males with repetition of the ethanol treatment. The highest (> 25-fold) difference in activity after repeated ethanol treatment was detected between females of the two strains B6.Cb4i5-Alpha4/Vad and B6.Cb4i5-Beta13/Vad. These results firstly suggest that females are more sensitive to repeated ethanol exposure than males, secondly they support the observations that ethanol has both inhibitory and stimulatory effects on motor activity, which are affected by sex, genotype, and repetition of treatment, and thirdly offer new quasi-congenic animal models with highly different responses to ethanol allowing one to more quickly move to gene detection.

A novel alanine-insensitive D-serine transporter in rat brain synaptosomal membranes

D-Serine is an endogenous modulator of brain N-methyl-D-aspartate receptors. This study investigates serine transport in brain synaptosomal fractions. Saturable, temperature-dependent uptake of both D- and L-[3H]serine was observed. Alanine was only partially effective in blocking transport, arguing against involvement of system ASC. Inhibitors of the systems A, L and GLY were also ineffective. Saturation studies suggested a submillimolar K(m) for both D- and L-serine. These data suggest the presence of a novel serine transport system in rodent synaptosomes.

Receptors in the ventral tegmental area mediating nicotine-induced dopamine release in the nucleus accumbens

Nicotine or cocaine, when administered intravenously, induces an increase of extracellular dopamine in the nucleus accumbens. The nicotine-mediated increase was shown to occur at least in part through increase of the activity of dopamine neurons in the ventral tegmental area. As part of our continuing studies of the mechanisms of nicotine effects in the brain, in particular, effects on reward and cognitive mechanisms, in the present study we examined the role of various receptors in the ventral tegmental area in nicotine and cocaine reward. We assayed inhibition of the increase of dopamine in the nucleus accumbens induced by intravenous nicotine or cocaine administration by antagonists administered into the ventral tegmental area. Nicotine-induced increase of accumbal dopamine release was inhibited by intrategmental nicotinic (mecamylamine), muscarinic (atropine), dopaminergic (D1: SCH 23390, D2: eticlopride), and NMDA glutamatergic (MK 801) and GABAB (saclofen) antagonists, but not by AMPA-kainate (CNQX, GYKI52466) antagonists under our experimental circumstances. The intravenous cocaine-induced increase of dopamine in the nucleus accumbens was inhibited by muscarinic (atropine), dopamine 2 (eticlopride), and GABAB (saclofen) antagonists but not by antagonists to nicotinic (mecamylamine), dopamine D1 (SCH 23390), glutamate (MK 801), or AMPA-kainate (CNQX, GYKI52466) receptors. Antagonists administered in the ventral tegmental area in the present study had somewhat different effects when they were previously administered intravenously. When administered intravenously atropine did not inhibit cocaine effects. The inhibition by atropine may be indirect, since this compound, when administered intrategmentally, decreased basal dopamine levels in the accumbens. The findings indicate that a number of receptors in the ventral tegmental area mediate nicotine-induced dopamine changes in the nucleus accumbens, a major component of the nicotine reward mechanism. Some, but not all, of these receptors in the ventral tegmental area also seem to participate in the reward mechanism of cocaine. The importance of local receptors in the ventral tegmental area was further indicated by the increase in accumbal dopamine levels after intrategmental administration of nicotine or also cocaine.