Věra Bubeníková-Valešová

Models of schizophrenia in humans and animals based on inhibition of NMDA receptors.

The research of the glutamatergic system in schizophrenia has advanced with the use of non-competitive antagonists of glutamate NMDA receptors (phencyclidine, ketamine, and dizocilpine), which change both human and animal behaviour and induce schizophrenia-like manifestations. Models based on both acute and chronic administration of these substances in humans and rats show phenomenological validity and are suitable for searching for new substances with antipsychotic effects. Nevertheless, pathophysiology of schizophrenia remains unexplained. In the light of the neurodevelopmental model of schizophrenia based on early administration of NMDA receptor antagonists it seems that increased cellular destruction by apoptosis or changes in function of glutamatergic NMDA receptors in the early development of central nervous system are decisive for subsequent development of psychosis, which often does not manifest itself until adulthood. Chronic administration of antagonists initializes a number of adaptation mechanisms, which correlate with findings obtained in patients with schizophrenia; therefore, this model is also suitable for research into pathophysiology of this disease.

Monitoring of dopamine and its metabolites in brain microdialysates: Method combining freeze-drying with liquid chromatography–tandem mass spectrometry

A sensitive assay method was developed for a parallel, rapid and precise determination of dopamine and its metabolites, homovanillic acid, 3-methoxytyramine and 3,4-dihydroxyphenylacetic acid, from brain microdialysates. The method consisted of a pre-treatment step, freeze-drying (lyophilization), to concentrate dopamine and its metabolites from the microdialysates, and a detection step using liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In particular, the reaction monitoring mode was selected for its extremely high degree of selectivity and the stable-isotope-dilution assay for its high precision of quantification. The developed method was characterized by the following parameters: the precision of the developed method was determined as ≥88.6% for dopamine, ≥89.9% for homovanillic acid, ≥86.1% for 3-methoxytyramine and ≥88.1% for 3,4-dihydroxyphenylacetic acid; the mean accuracy was determined as ≥88.2% for dopamine, ≥88.3% for homovanillic acid, ≥85.9% for 3-methoxytyramine and ≥88.6% for 3,4-dihydroxyphenylacetic acid. The developed method was compared to (1) other combinations of pre-treatment methods (solid phase extraction and nitrogen stripping) with LC-MS and (2) another detection method, liquid chromatography, with electrochemical detection. The novel developed method using combination of lyophilization with LC-ESI-MS/MS was tested on real samples obtained from the nucleus accumbens of rat pups after an acute methamphetamine administration. It was proven that the developed assay could be applied to both a simultaneous analysis of all four substrates (dopamine, homovanillic acid, 3-methoxytyramine and 3,4-dihydroxyphenylacetic acid) in microdialysis samples acquired from the rat brain and the monitoring of their slight concentration changes on a picogram level over time following methamphetamine stimulus.

Electroencephalographic Spectral and Coherence Analysis of Ketamine in Rats: Correlation with Behavioral Effects and Pharmacokinetics

Aims: This study was designed to evaluate the changes in EEG power spectra and EEG coherence in a ketamine model of psychosis in rats. Analyses of behavioral measurements – locomotion and sensorimotor gating – and the pharmacokinetics of ketamine and norketamine were also conducted. Methods: Ketamine and norketamine levels in rat sera and brains were analyzed by gas chromatography-mass spectrometry after ketamine 30 mg/kg (i.p.). Ketamine 9 and 30 mg/kg (i.p.) were used in the behavioral and EEG experiments. Locomotor effects in an open field test and deficits in prepulse inhibition of acoustic startle reaction (PPI ASR) were evaluated in the behavioral experiments. EEG signals were simultaneously recorded from 12 implanted active electrodes; subsequently, an EEG power spectral and coherence analysis was performed. Results: Ketamine had a rapid penetration into the brain; the peak concentrations of the drug were reached within 15 min after administration. Ketamine induced marked hyperlocomotion and deficits in the PPI ASR. EEG spectral analysis mainly showed increases in EEG power as well as coherence. These were most robust at 10–15 min after the administration and influenced all parts of the spectrum with ketamine 30 mg/kg. Conclusions: Ketamine at behaviorally active doses induces a robust increase in EEG power spectra and coherence. The maximum levels of change correlated with the kinetics of ketamine.

Subanesthetic dose of ketamine decreases prefrontal theta cordance in healthy volunteers: implications for antidepressant effect

BACKGROUND Theta cordance is a novel quantitative electroencephalography (QEEG) measure that correlates with cerebral perfusion. A series of clinical studies has demonstrated that the prefrontal theta cordance value decreases after 1 week of treatment in responders to antidepressants and that this effect precedes clinical improvement. Ketamine, a non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors, has a unique rapid antidepressant effect but its influence on theta cordance is unknown. METHOD In a double-blind, cross-over, placebo-controlled experiment we studied the acute effect of ketamine (0.54 mg/kg within 30 min) on theta cordance in a group of 20 healthy volunteers. RESULTS Ketamine infusion induced a decrease in prefrontal theta cordance and an increase in the central region theta cordance after 10 and 30 min. The change in prefrontal theta cordance correlated with ketamine and norketamine blood levels after 10 min of ketamine infusion. CONCLUSIONS Our data indicate that ketamine infusion immediately induces changes similar to those that monoamineric-based antidepressants induce gradually. The reduction in theta cordance could be a marker and a predictor of the fast-acting antidepressant effect of ketamine, a hypothesis that could be tested in depressive patients treated with ketamine.

The opposite effect of a low and a high dose of serotonin-1A agonist on behavior induced by MK-801.

The purpose of the present study was to investigate the opposite effect of the pre- and postsynaptic serotonin-1A (5-HT(1A)) receptors on the psychotic-like behavior induced by a non-competitive antagonist of the NMDA receptor, dizocilpine (MK-801). Male Wistar rats received two doses (0.025mg/kg and 1mg/kg) of 5-HT(1A) receptor agonist 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin) and/or MK-801 in two different doses, 0.1mg/kg or 0.3mg/kg. We measured sensorimotor gating by testing prepulse inhibition of acoustic startle response (PPI) and locomotor activity of rats. We found an opposite effect of the low and high 5-HT(1A) receptor agonist doses on MK-801 induced deficit in PPI and hyperlocomotion in habituated rats. The low dose of 8-OH-DPAT, which preferentially acts on presynaptic 5-HT(1A) receptors, restored the deficit in PPI and hyperlocomotion in MK-801 (0.1mg/kg)-treated habituated rats. However, the high dose of 8-OH-DPAT, which activates both pre- and postsynaptic 5-HT(1A) receptors, decreased PPI and increased locomotor activity after administration of the low dose of MK-801. Administration of 8-OH-DPAT itself dose-dependently decreased PPI. However, only the high dose of 8-OH-DPAT increased spontaneous locomotor activity of rats. Our results indicate that there is an interaction between the NMDA and 5-HT(1A) receptors. In addition, these findings could indicate that activation of the 5-HT(1A) autoreceptor could be effective as a treatment in schizophrenia, but full potent agonism of the receptor could worsen the psychotic symptoms.

Sex differences in the effects of N,N-diethyllysergamide (LSD) on behavioural activity and prepulse inhibition

The aim of this study was to describe sex differences in the behavioural effects of N,N-diethyllysergamide (LSD) (locomotor activity and other behavioural repertoire in the open field) and its effects on sensorimotor gating in rats (prepulse inhibition (PPI) of the acoustic startle reaction). Three groups of animals were analysed: males, oestral and pro-oestral phase females (EP females), and metoestral and dioestral phase females (MD females). LSD (5, 50 and 200 microg/kg subcutaneously) attenuated locomotor activity and normal behavioural repertoire, and induced flat body posture, wet dog shakes and disrupted PPI. The most prominent behavioural findings of LSD were for LSD 200 microg/kg which suppressed almost all behavioural activity. LSD had mainly inhibitory locomotor effects in males and MD females, yet in EP female rats LSD increased locomotion during the second half of testing period. The main sex differences were observed in locomotor and exploratory behaviour. Both EP and MD females were less sensitive to hypolocomotor effects of LSD and had less pronounced thigmotaxis than males. Further EP females had increased rearing after LSD 5microg/kg. On the contrary although LSD disrupted PPI in males and MD female rats, EP females were protected from this disruptive effect. Thus, EP females seem to have a lower sensitivity to LSD behavioural actions.

The Effect of Prenatal Methamphetamine Exposure on Recognition Memory in Adult Rats

The use of methamphetamine (MA) among pregnant women is an increasing world-wide health problem. Prenatal MA exposure may cause changes in foetus but the exact effects have remained unclear. The aim of this study is to present the effect of prenatal MA exposure on recognition memory in adult rats. Adult female Wistar rats were injected daily with D-methamphetamine HCl (MA; 5 mg/kg, s.c.) during the entire gestation period. Control females were treated with saline in the same regime. Adult male offspring was administrated acutely by MA (1 mg/kg i.p.) or saline 30 minutes before beginning of an experiment. For testing recognition memory two tasks were chosen: Novel Object Recognition Test (NORT) and Object Location Test (OLT). Our results demonstrate that prenatally MA-exposed animals were worse in NORT independently on an acute administration of MA in adulthood. Prenatally MA-exposed rats did not deteriorate in OLT, but after acute administration of MA in adulthood, there was significant worsening compared to appropriate control. Prenatally saline-exposed offspring did not deteriorate in any test even after acute administration of MA. Our data suggest that prenatal MA exposure in rats cause impairment in recognition memory in adult offspring, but not in spatial memory. In addition, acute administration of MA to controls did not deteriorate either recognition or spatial memory.

Trans-generational neurochemical modulation of methamphetamine in the adult brain of the Wistar rat

Chronic methamphetamine (METH) abuse has been shown to elicit strong neurotoxic effects. Yet, with an increasing number of children born to METH abusing mothers maturing into adulthood, one important question is how far do the neurotoxic effects of METH alter various neurotransmitter systems in the adult METH-exposed offspring. The purpose of this study was to investigate long-term trans-generational neurochemical changes, following prenatal METH exposure, in the adult Wistar rat brain. METH or saline (SAL—control animals) was administered to pregnant dams throughout the entire gestation period (G0-G22). At postnatal day 90, dopamine, serotonin, glutamate and GABA were measured in the adult brain before (baseline) and after a METH re-administration using in vivo microdialysis and liquid chromatography/mass spectrometry. The results show that METH-exposure increased basal levels of monoamines and glutamate, but decreased GABA levels in all measured brain regions. Acute challenge with METH injection in the METH-exposed group induced a lower increase in the monoamine system relative to the increase in the GABAergic and glutamatergic system. The data show that prenatal METH exposure has strong effects on the monoaminergic, GABAergic and glutamatergic system even when exposure to METH was limited to the prenatal phase. Toxicological effects of METH have therefore longer lasting effects as currently considered and seem to affect the excitatory-inhibitory balance in the brain having strong implications for cognitive and behavioral functioning.

Chronic methamphetamine self-administration dysregulates 5-HT2A and mGlu2 receptor expression in the rat prefrontal and perirhinal cortex: Comparison to chronic phencyclidine and MK-801

ABSTRACT Chronic methamphetamine (meth) abuse often turns into a compulsive drug‐taking disorder accompanied by persistent cognitive deficits and re‐occurring psychosis. Possible common neurobiological substrates underlying meth‐induced deficits and schizophrenia remain poorly understood. Serotonin 2A (5‐HT2A) and metabotropic glutamate 2 (mGlu2) receptors co‐regulate psychosis‐like behaviors and cognitive function in animals. Therefore, in the present study we examined the effects of chronic exposure to three different drugs known to produce persistent deficits in sensorimotor gating and cognition [meth, phencyclidine (PCP) and MK‐801] on the expression of 5‐HT2A and mGlu2 within the rat medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC) and perirhinal cortex (PRh). Adult male rats underwent 14days of: (a) meth self‐administration (6h/day), (b) phencyclidine (PCP; 5mg/kg, twice/day) administration, or (c) MK‐801 (0.3mg/kg, twice/day) administration. Seven days after the discontinuation of drug administration, tissues of interest were collected for protein expression analysis. We found that despite different pharmacological mechanism of action, chronic meth, PCP, and MK‐801 similarly dysregulated 5‐HT2A and mGlu2, as indicated by an increase in the 5‐HT2A/mGlu2 expression ratio in the mPFC (all three tested drugs), PRh (meth and PCP), and dHPC (MK‐801 only). Complementary changes in G‐protein expression (increase in G&agr;q and decrease in G&agr;i) were also observed in the mPFC of meth animals. Finally, we found that 5‐HT2A/mGlu2 cooperation can be mediated in part by the formation of the receptor heteromer in some, but not all cortical regions. In summary, these data suggest that a shift towards increased availability (and G‐protein coupling) of cortical 5‐HT2A vs. mGlu2 receptors may represent a common neurobiological mechanism underlying the emergence of psychosis and cognitive deficits observed in subjects with meth use disorder and schizophrenia. HIGHLIGHTS5‐HT2A and mGlu2 receptors co‐immunoprecipitate in the rat cortical tissue.Chronic meth increased the 5‐HT2A/mGlu2 expression ratio in the mPFC and PRh.Chronic PCP and MK‐801 also increased the 5‐HT2A/mGlu2 expression ratio in the mPFC.Chronic meth increased 5‐HT2A partner G‐protein (G&agr;q) in the mPFC.

Contents Vol. 63, 2011

A. Drago, Naples G. Erdmann, Berlin A. Fischer, Göttingen J.M. Ford, San Francisco, Calif. S. Galderisi, Naples M. Hatzinger, Solothurn U. Hegerl, Leipzig K. Hirata, Mibu M. Kato, Osaka J. Kornhuber, Erlangen D. Lehmann, Zürich P. Monteleone, Naples G. Okugawa, Osaka G.N. Papadimitriou, Athens M. Popoli, Milano M. Reuter, Bonn F. Rösler, Marburg G. Ruigt, Oss J.K. Rybakowski, Poznan F. Schneider, Aachen R. Schwarting, Marburg M. Shigeta, Tokyo D. Souery, Brussels A. Steiger, Munich P. Willner, Swansea Associate Editors