17 beta-Estradiol replacement in young, adult and middle-aged female ovariectomized rats promotes improvement of spatial reference memory and an antidepressant effect and alters monoamines and BDNF levels in memory- and depression-related brain areas

Clinical and experimental evidence suggest that estrogens have a major impact on cognition, presenting neurotrophic and neuroprotective actions in regions involved in such function. In opposite, some studies indicate that certain hormone therapy regimens may provoke detrimental effects over female cognitive and neurological function. Therefore, we decided to investigate how estrogen treatment would influence cognition and depression in different ages. For that matter, this study assessed the effects of chronic 17 beta-estradiol treatment over cognition and depressive-like behaviors of young (3 months old), adult (7 months old) and middle-aged (12 months old) reproductive female Wistar rats. These functions were also correlated with alterations in the serotonergic system, as well as hippocampal BDNF. 17 beta-Estradiol treatment did not influence animals' locomotor activity and exploratory behavior, but it was able to improve the performance of adult and middle-aged rats in the Morris water maze, the latter being more responsive to the treatment. Young and adult rats displayed decreased immobility time in the forced swimming test, suggesting an effect of 17 beta-estradiol also over such depressive-like behavior. This same test revealed increased swimming behavior, triggered by serotonergic pathway, in adult rats. Neurochemical evaluations indicated that 17 beta-estradiol treatment was able to increase serotonin turnover rate in the hippocampus of adult rats. Interestingly, estrogen treatment increased BDNF levels from animals of all ages. These findings support the notion that the beneficial effects of 17 beta-estradiol over spatial reference memory and depressive-like behavior are evident only when hormone therapy occurs at early ages and early stages of hormonal decline. (C) 2011 Elsevier B.V. All rights reserved.

Serotonin-2C receptors in the basolateral nucleus of the amygdala mediate the anxiogenic effect of acute imipramine and fluoxetine administration

A growing body of evidence indicates that facilitation of serotonin-2C receptor (5-HT2CR)-mediated neurotransmission in the basolateral nucleus of the amygdala (BLA) is involved in anxiety generation. We investigated here whether BLA 5-HT(2C)Rs exert a differential role in the regulation of defensive behaviours related to generalized anxiety (inhibitory avoidance) and panic (escape) disorders. We also evaluated whether activation of BLA 5-HT(2C)Rs accounts for the anxiogenic effect caused by acute systemic administration of the antidepressants imipramine and fluoxetine. Male Wistar rats were tested in the elevated T-maze after intra-BLA injection of the endogenous agonist 5-HT, the 5-HT2CR agonist MK-212 or the 5-HT2CR antagonist SB-242084. This test allows the measurement of inhibitory avoidance acquisition and escape expression. We also investigated whether intra-BLA administration of SB-242084 interferes with the acute anxiogenic effect caused by imipramine and fluoxetine in the Vogel conflict test, and imipramine in the elevated T-maze. While intra-BLA administration of 5-HT and MK-212 facilitated inhibitory avoidance acquisition, suggesting an anxiogenic effect, SB-242084 had the opposite effect. None of these drugs affected escape performance. Intra-BLA injection of a sub-effective dose of SB-242084 fully blocked the anxiogenic effect caused either by the local microinjection of 5-HT or the systemic administration of imipramine and fluoxetine. Our findings indicate that 5-HT(2C)Rs in BLA are selectively involved in the regulation of defensive behaviours associated with generalized anxiety, but not panic. The results also provide the first direct evidence that activation of BLA 5-HT(2C)Rs accounts for the short-term aversive effect of antidepressants.

Cannabidiol blocks long-lasting behavioral consequences of predator threat stress: Possible involvement of 5HT1A receptors

Posttraumatic stress disorder (PTSD) is an incapacitating syndrome that follows a traumatic experience. Predator exposure promotes long-lasting anxiogenic effect in rodents, an effect related to symptoms found in PTSD patients. Cannabidiol (CBD) is a non-psychotomimetic component of Cannabis sativa with anxiolytic effects. The present study investigated the anti-anxiety actions of CBD administration in a model of PTSD. Male Wistar rats exposed to a predator (cat) received, 1 h later, singled or repeated i.p. administration of vehicle or CBD. Seven days after the stress animals were submitted to the elevated plus maze. To investigate the involvement of 5HT1A receptors in CBD effects animals were pre-treated with WAY100635, a 5HT1A receptor antagonist. To explore possible neurobiological mechanisms involved in these effects, 5HT1A receptor mRNA and BDNF protein expression were measured in the hippocampus, frontal cortex, amygdaloid complex and dorsal periaqueductal gray. Repeated administration of CBD prevented long-lasting anxiogenic effects promoted by a single predator exposure. Pretreatment with WAY100635 attenuated CBD effects. Seven days after predator exposure 5HT1A mRNA expression was up regulated in the frontal cortex and hippocampus. CBD and paroxetine failed to prevent this effect. No change in BDNF expression was found. In conclusion, predator exposure promotes long-lasting up-regulation of 5HT1A receptor gene expression in the hippocampus and frontal cortex. Repeated CBD administration prevents the long-lasting anxiogenic effects observed after predator exposure probably by facilitating 5HT1A receptors neurotransmission. Our results suggest that CBD has beneficial potential for PTSD treatment and that 5HT1A receptors could be a therapeutic target in this disorder. (C) 2012 Elsevier Ltd. All rights reserved.

Cannabidiol, a Cannabis sativa constituent, as an anxiolytic drug

Objectives: To review and describe studies of the non-psychotomimetic constituent of Cannabis sativa, cannabidiol (CBD), as an anxiolytic drug and discuss its possible mechanisms of action. Method: The articles selected for the review were identified through searches in English,articles, and book chapters were handsearched for additional references. Experimental animal and human studies were included, with no time restraints. Results: Studies using animal models of anxiety and involving healthy volunteers clearly suggest an anxiolytic-like effect of CBD. like", and "cannabidiol and anxiety". The reference lists of the publications included, review Portuguese, and Spanish in the electronic databases ISI Web of Knowledge, SciELO, PubMed, and PsycINFO, combining the search terms "cannabidiol and anxiolytic", "cannabidiol and anxiolytic-articles, and book chapters were handsearched for additional references. Experimental animal and human studies were included, with no time restraints. Results: Studies using animal models of anxiety and involving healthy volunteers clearly suggest an anxiolytic-like effect of CBD. Moreover, CBD was shown to reduce anxiety in patients with social anxiety disorder. Conclusion: like", and "cannabidiol and anxiety". The reference lists of the publications included, review Future clinical trials involving patients with different anxiety disorders are warranted, especially of panic disorder, obsessive-compulsive disorder, social anxiety disorder, and post-traumatic stress disorders. The adequate therapeutic window of CBD and the precise mechanisms involved in its anxiolytic action remain to be determined.

Differential role of CB1 and TRPV1 receptors on anandamide modulation of defensive responses induced by nitric oxide in the dorsolateral periaqueductal gray

CB1, TRPV1 and NO can regulate glutamate release and modify defensive behaviors in regions related to defensive behavior such as the dorsolateral periaqueductal gray (dIPAG). A possible interaction between the endocannabinoid and nitrergic systems in this area, however, has not been investigated yet. The objective of the present work was to verify if activation of CB1 or TRPV1 receptors could interfere in the flight responses induced in rats by the injection of SIN-1, an NO donor, into the dIPAG. The results showed that local administration of a low dose (5 pmol) of anandamide (AEA) attenuated the flight responses, measured by the total distance moved and maximum speed in an open arena, induced by intra-dIPAG microinjection of SIN-1 (150 nmol). URB597 (0.1 nmol), an inhibitor of anandamide metabolism, produced similar effects. When animals were locally treated with the CB1 receptor antagonist AM251 the effective AEA dose (5 pmol) increased, rather than decreased, the flight reactions induced by SIN1-1. Higher (50-200 nmol) doses of AEA were ineffective and even tended to potentiate the SIN-1 effect. The TRPV1 antagonist capsazepine (CPZ, 30 nmol) prevented SIN-1 effects and attenuated the potentiation of its effect by the higher (200 nmol) AEA dose. The results indicate that AEA can modulate in a dual way the pro-aversive effects of NO in the dIPAG by activating CB1 or TRPV1 receptors. (C) 2012 Elsevier Ltd. All rights reserved.

Early and late neurodegeneration and memory disruption after intracerebroventricular streptozotocin

Glucose metabolism and insulin signaling disruptions in the brain have been proposed as a likely etiology of Alzheimer's disease. The aim of the present study was to investigate the time course of cognitive impairments induced by intracerebroventricular injection of streptozotocin (STZ) in rats and correlate them with the ensuing neurodegenerative process. Early and late effects of STZ were evaluated by using the reference and working memory versions of the Morris' water maze task and the evaluation of neurodegenerative markers by immunoblotting and the Fluoro-jade C histochemistry. The results revealed different types of behavioral and neurodegenerative responses, with distinct time courses. We observed an early disruption on the working memory as early as 3 h after STZ injections, which was followed by degenerative processes in the hippocampus at 1 and 15 days after STZ injections. Memory disruption increases over time and culminates with significant changes in amyloid-beta peptide and hyperphosphorylated Tau protein levels in distinct brain structures. These findings add information on the Alzheimer's disease-like STZ animal model and on the mechanisms underlying neurodegenerative processes. (C) 2012 Elsevier Inc. All rights reserved.

Inhibition of the NMDA receptor/Nitric Oxide pathway in the dorsolateral periaqueductal gray causes anxiolytic-like effects in rats submitted to the Vogel conflict test

Abstract Background Several studies had demonstrated the involvement of the dorsolateral portion of periaqueductal grey matter (dlPAG) in defensive responses. This region contains a significant number of neurons containing the enzyme nitric oxide synthase (NOS) and previous studies showed that non-selective NOS inhibition or glutamate NMDA-receptor antagonism in the dlPAG caused anxiolytic-like effects in the elevated plus maze. Methods In the present study we verified if the NMDA/NO pathway in the dlPAG would also involve in the behavioral suppression observed in rats submitted to the Vogel conflict test. In addition, the involvement of this pathway was investigated by using a selective nNOS inhibitor, Nω-propyl-L-arginine (N-Propyl, 0.08 nmol/200 nL), a NO scavenger, carboxy-PTIO (c-PTIO, 2 nmol/200 nL) and a specific NMDA receptor antagonist, LY235959 (4 nmol/200 nL). Results Intra-dlPAG microinjection of these drugs increased the number of punished licks without changing the number of unpunished licks or nociceptive threshold, as measure by the tail flick test. Conclusion The results indicate that activation of NMDA receptors and increased production of NO in the dlPAG are involved in the anxiety behavior displayed by rats in the VCT.

New perspective on the pathophysiology of panic: merging serotonin and opioids in the periaqueductal gray

Panic disorder patients are vulnerable to recurrent panic attacks. Two neurochemical hypotheses have been proposed to explain this susceptibility. The first assumes that panic patients have deficient serotonergic inhibition of neurons localized in the dorsal periaqueductal gray matter of the midbrain that organize defensive reactions to cope with proximal threats and of sympathomotor control areas of the rostral ventrolateral medulla that generate most of the neurovegetative symptoms of the panic attack. The second suggests that endogenous opioids buffer normal subjects from the behavioral and physiological manifestations of the panic attack, and their deficit brings about heightened suffocation sensitivity and separation anxiety in panic patients, making them more vulnerable to panic attacks. Experimental results obtained in rats performing one-way escape in the elevated T-maze, an animal model of panic, indicate that the inhibitory action of serotonin on defense is connected with activation of endogenous opioids in the periaqueductal gray. This allows reconciliation of the serotonergic and opioidergic hypotheses of panic pathophysiology, the periaqueductal gray being the fulcrum of serotonin-opioid interaction.

Chronic unpredictable mild stress alters an anxiety-related defensive response, Fos immunoreactivity and hippocampal adult neurogenesis

Previous results show that elevated T-maze (ETM) avoidance responses are facilitated by acute restraint. Escape, on the other hand, was unaltered. To examine if the magnitude of the stressor is an important factor influencing these results, we investigated the effects of unpredictable chronic mild stress (UCMS) on ETM avoidance and escape measurements. Analysis of Fos protein immunoreactivity (Fos-ir) was used to map areas activated by stress exposure in response to ETM avoidance and escape performance. Additionally, the effects of the UCMS protocol on the number of cells expressing the marker of migrating neuroblasts doublecortin (DCX) in the hippocampus were investigated. Corticosterone serum levels were also measured. Results showed that UCMS facilitates ETM avoidance, not altering escape. In unstressed animals, avoidance performance increases Fos-ir in the cingulate cortex, hippocampus (dentate gyrus) and basomedial amygdala, and escape increases Fos-ir in the dorsolateral periaqueductal gray and locus ceruleus. In stressed animals submitted to ETM avoidance, increases in Fos-ir were observed in the cingulate cortex, ventrolateral septum, hippocampus, hypothalamus, amygdala, dorsal and median raphe nuclei. In stressed animals submitted to ETM escape, increases in Fos-ir were observed in the cingulate cortex, periaqueductal gray and locus ceruleus. Also, UCMS exposure decreased the number of DCX-positive cells in the dorsal and ventral hippocampus and increased corticosterone serum levels. These data suggest that the anxiogenic effects of UCMS are related to the activation of specific neurobiological circuits that modulate anxiety and confirm that this stress protocol activates the hypothalamus-pituitary-adrenal axis and decreases hippocampal adult neurogenesis.

Enhancement of behavioral sensitization, anxiety-like behavior, and hippocampal and frontal cortical CREB levels following cocaine abstinence in mice exposed to cocaine during adolescence

Adolescence has been linked to greater risk-taking and novelty-seeking behavior and a higher prevalence of drug abuse and risk of relapse. Decreases in cyclic adenosine monophosphate response element binding protein (CREB) and phosphorylated CREB (pCREB) have been reported after repeated cocaine administration in animal models. We compared the behavioral effects of cocaine and abstinence in adolescent and adult mice and investigated possible age-related differences in CREB and pCREB levels. Adolescent and adult male Swiss mice received one daily injection of saline or cocaine (10 mg/kg, i.p.) for 8 days. On day 9, the mice received a saline injection to evaluate possible environmental conditioning. After 9 days of withdrawal, the mice were tested in the elevated plus maze to evaluate anxiety-like behavior. Twelve days after the last saline/cocaine injection, the mice received a challenge injection of either cocaine or saline, and locomotor activity was assessed. One hour after the last injection, the brains were extracted, and CREB and pCREB levels were evaluated using Western blot in the prefrontal cortex (PFC) and hippocampus. The cocaine-pretreated mice during adolescence exhibited a greater magnitude of the expression of behavioral sensitization and greater cocaine withdrawal-induced anxiety-like behavior compared with the control group. Significant increases in CREB levels in the PFC and hippocampus and pCREB in the hippocampus were observed in cocaine-abstinent animals compared with the animals treated with cocaine in adulthood. Interestingly, significant negative correlations were observed between cocaine sensitization and CREB levels in both regions. These results suggest that the behavioral and neurochemical consequences of psychoactive substances in a still-developing nervous system can be more severe than in an already mature nervous system

The role of Nox2-derived ROS in the development of cognitive impairment after sepsis

BACKGROUND: Sepsis- associated encephalopathy (SAE) is an early and common feature of severe infections. Oxidative stress is one of the mechanisms associated with the pathophysiology of SAE. The goal of this study was to investigate the involvement of NADPH oxidase in neuroinflammation and in the long-term cognitive impairment of sepsis survivors. METHODS: Sepsis was induced in WT and gp91phox knockout mice (gp91phox-/-) by cecal ligation and puncture (CLP) to induce fecal peritonitis. We measured oxidative stress, Nox2 and Nox4 gene expression and neuroinflammation in the hippocampus at six hours, twenty-four hours and five days post-sepsis. Mice were also treated with apocynin, a NADPH oxidase inhibitor. Behavioral outcomes were evaluated 15 days after sepsis with the inhibitory avoidance test and the Morris water maze in control and apocynin-treated WT mice. RESULTS: Acute oxidative damage to the hippocampus was identified by increased 4-HNE expression in parallel with an increase in Nox2 gene expression after sepsis. Pharmacological inhibition of Nox2 with apocynin completely inhibited hippocampal oxidative stress in septic animals. Pharmacologic inhibition or the absence of Nox2 in gp91phox-/- mice prevented glial cell activation, one of the central mechanisms associated with SAE. Finally, treatment with apocynin and inhibition of hippocampal oxidative stress in the acute phase of sepsis prevented the development of long-term cognitive impairment. CONCLUSIONS: Our results demonstrate that Nox2 is the main source of reactive oxygen species (ROS) involved in the oxidative damage to the hippocampus in SAE and that Nox2-derived ROS are determining factors for cognitive impairments after sepsis. These findings highlight the importance of Nox2-derived ROS as a central mechanism in the development of neuroinflammation associated with SAE.

Nuovo modello animale per lo studio della working memory: validazione farmacologica e applicazioni

The present study was performed to validate a spatial working memory task using pharmacological manipulations. The water escape T-maze, which combines the advantages of the Morris water maze and the T-maze while minimizes the disadvantages, was used. Scopolamine, a drug that affects cognitive function in spatial working memory tasks, significantly decreased the rat performance in the present delayed alternation task. Since glutamate neurotransmission plays an important role in the maintaining of working memory, we evaluated the effect of ionotropic and metabotropic glutamatergic receptors antagonists, administered alone or in combination, on rat behaviour. As the acquisition and performance of memory tasks has been linked to the expression of the immediately early gene cFos, a marker of neuronal activation, we also investigated the neurochemical correlates of the water escape T-maze after pharmacological treatment with glutamatergic antagonists, in various brain areas. Moreover, we focused our attention on the involvement of perirhinal cortex glutamatergic neurotransmission in the acquisition and/or consolidation of this particular task. The perirhinal cortex has strong and reciprocal connections with both specific cortical sensory areas and some memory-related structures, including the hippocampal formation and amygdala. For its peculiar position, perirhinal cortex has been recently regarded as a key region in working memory processes, in particular in providing temporary maintenance of information. The effect of perirhinal cortex lesions with ibotenic acid on the acquisition and consolidation of the water escape T-maze task was evaluated. In conclusion, our data suggest that the water escape T-maze could be considered a valid, simple and quite fast method to assess spatial working memory, sensible to pharmacological manipulations. Following execution of the task, we observed cFos expression in several brain regions. Furthermore, in accordance to literature, our results suggest that glutamatergic neurotransmission plays an important role in the acquisition and consolidation of working memory processes.

Study on the regulation of mRNA expression of GABA transporters (GAT-1 and GAT-3) in rat brain

The submitted work concentrated on the study of mRNA expression of two distinct GABA transporters, GAT-1 and GAT-3, in the rat brain. For the detection and quantification of the chosen mRNAs, appropriate methods had to be established. Two methods, ribonuclease protection assay (RPA) and competitive RT-PCR were emloyed in the present study. Competitive RT-PCR worked out to be 20 times more sensitive as RPA. Unlike the sensitivity, the fidelity of both techniques was comparable with respect to their intra- and inter-assay variability.The basal mRNA levels of GAT-1 and GAT-3 were measured in various brain regions. Messenger RNAs for both transporters were detected in all tested brain regions. Depending on the region, the observed mRNA level for GAT-1 was 100-300 higher than for GAT-3. The GAT-1 mRNA levels were similar in all tested regions. The distribution of GAT-3 mRNA seemed to be more region specific. The strongest GAT-3 mRNA expression was detected in striatum, medulla oblongata and thalamus. The lowest levels of GAT-3 were in cortex frontalis and cerebellum.Furthermore, the mRNA expression for GAT-1 and GAT-3 was analysed under altered physiological conditions; in kindling model of epilepsy and also after long-term treatment drugs modulating GABAergic transmission. In kindling model of epilepsy, altered GABA transporter function was hypothesised by During and coworkers (During et al., 1995) after observed decrease in binding of nipecotic acid, a GAT ligand, in hippocampus of kindled animals. In the present work, the mRNA levels were measured in hippocampus and whole brain samples. Neither GAT-1 nor GAT-3 showed altered transcription in any tested region of kindled animals compared to controls. This leads to conclusion that an altered functionality of GABA transporters is involved in epilepsy rather than a change in their expression.The levels of GAT-1 and GAT-3 mRNAs were also measured in the brain of rats chronically treated with diazepam or zolpidem, GABAA receptor agonists. Prior to the molecular biology tests, behavioural analysis was carried out with chronically and acutely treated animals. In two tests, open field and elevated plus-maze, the basal activity exploration and anxiety-like behaviour were analysed. Zolpidem treatment increased exploratory activity. There were observed no differencies between chronically and acutely treated animals. Diazepam increased exploratory activity and decresed anxiety-like behaviour when applied acutely. This effect disappeard after chronic administration of diazepam. The loss of effect suggested a development of tolerance to effects of diazepam following long-term administration. Double treatment, acute injection of diazepam after chronic diazepam treatment, confirmed development of a tolerance to effects of diazepam. Also, the mRNAs for GAT-1 and GAT-3 were analysed in cortex frontalis, hippocampus, cerebellum and whole brain samples of chronically treated animals. The mRNA levels for any of tested GABA transporters did not show significant changes in any of tested region neither after diazepam nor zolpidem treatment. Therefore, changes in GAT-1 and GAT-3 transcription are probably not involved in adaptation of GABAergic system to long-term benzodiazepine administration and so in development of tolerance to benzodiazepines.

Interaction between APOE4 genotype and environmental risk factors in Alzheimer's disease

Alzheimer's disease (AD) is probably caused by both genetic and environmental risk factors. The major genetic risk factor is the E4 variant of apolipoprotein E gene called apoE4. Several risk factors for developing AD have been identified including lifestyle, such as dietary habits. The mechanisms behind the AD pathogenesis and the onset of cognitive decline in the AD brain are presently unknown. In this study we wanted to characterize the effects of the interaction between environmental risk factors and apoE genotype on neurodegeneration processes, with particular focus on behavioural studies and neurodegenerative processes at molecular level. Towards this aim, we used 6 months-old apoE4 and apoE3 Target Replacement (TR) mice fed on different diets (high intake of cholesterol and high intake of carbohydrates). These mice were evaluated for learning and memory deficits in spatial reference (Morris Water Maze (MWM)) and contextual learning (Passive Avoidance) tasks, which involve the hippocampus and the amygdala, respectively. From these behavioural studies we found that the initial cognitive impairments manifested as a retention deficit in apoE4 mice fed on high carbohydrate diet. Thus, the genetic risk factor apoE4 genotype associated with a high carbohydrate diet seems to affect cognitive functions in young mice, corroborating the theory that the combination of genetic and environmental risk factors greatly increases the risk of developing AD and leads to an earlier onset of cognitive deficits. The cellular and molecular bases of the cognitive decline in AD are largely unknown. In order to determine the molecular changes for the onset of the early cognitive impairment observed in the behavioural studies, we performed molecular studies, with particular focus on synaptic integrity and Tau phosphorylation. The most relevant finding of our molecular studies showed a significant decrease of Brain-derived Neurotrophic Factor (BDNF) in apoE4 mice fed on high carbohydrate diet. Our results may suggest that BDNF decrease found in apoE4 HS mice could be involved in the earliest impairment in long-term reference memory observed in behavioural studies. The second aim of this thesis was to study possible involvement of leptin in AD. There is growing evidence that leptin has neuroprotective properties in the Central Nervous System (CNS). Recent evidence has shown that leptin and its receptors are widespread in the CNS and may provide neuronal survival signals. However, there are still numerous questions, regarding the molecular mechanism by which leptin acts, that remain unanswered. Thus, given to the importance of the involvement of leptin in AD, we wanted to clarify the function of leptin in the pathogenesis of AD and to investigate if apoE genotype affect leptin levels through studies in vitro, in mice and in human. Our findings suggest that apoE4 TR mice showed an increase of leptin in the brain. Leptin levels are also increased in the cerebral spinal fluid of AD patients and apoE4 carriers with AD have higher levels of leptin than apoE3 carriers. Moreover, leptin seems to be expressed by reactive glial cells in AD brains. In vitro, ApoE4 together with Amyloid beta increases leptin production by microglia and astrocytes. Taken together, all these findings suggest that leptin replacement might not be a good strategy for AD therapy. Our results show that high leptin levels were found in AD brains. These findings suggest that, as high leptin levels do not promote satiety in obese individuals, it might be possible that they do not promote neuroprotection in AD patients. Therefore, we hypothesized that AD brain could suffer from leptin resistance. Further studies will be critical to determine whether or not the central leptin resistance in SNC could affect its potential neuroprotective effects.

Funktionelle Bedeutung von P-Glykoprotein für Wirkungen und Nebenwirkungen von Antipsychotika

Therapeutisches Drug Monitoring (TDM) ist eine Maßnahme, bei der durch Messung der Medikamentenspiegel im Blut die Dosis ermittelt wird, bei der mit höchster Wahrscheinlichkeit mit Therapieansprechen gerechnet werden kann. Dabei wird angenommen, dass die Konzentrationen im Blut mit denen im Wirkkompartiment korrelieren. Für Antipsychotika wurde gezeigt, dass die Konzentrationen im Blut direkt mit denen im Gehirn korrelieren, die Verteilung zwischen den beiden Kompartimenten ist jedoch für die verschiedenen Antipsychotika sehr unterschiedlich. Die Distribution von Arzneistoffen zwischen Blut und Gehirn wird durch Effluxtransporter in der Blut-Hirn-Schranke kontrolliert. Welche Rolle dabei P-Glykoprotein (P-gp) für die Verteilung von atypischen Antipsychotika spielt und wie die Pharmakokinetik und –dynamik durch diesen Transporter beeinflusst werden, sollte in dieser Arbeit untersucht werden. Für die Messung des neu eingeführten Antipsychotikums Aripiprazol, sowie für seinen aktiven Metaboliten Dehydroaripiprazol, wurde eine hochleistungsflüssigchromatographische (HPLC) Methode mit Säulenschaltung und spektrophotometrischer Detektion etabliert. Die Methode wurde für die Messung von Serumproben schizophrener Patienten eingesetzt, um einen therapeutischen Bereich für Aripiprazol zu ermitteln. Aus der Analyse von 523 Patientenproben wurde herausgefunden, dass Aripiprazol-Serumkonzentrationen von 150 bis 300 ng/ml mit gutem klinischen Ansprechen und einem geringen Risiko für Nebenwirkungen einhergingen. Weiterhin wurde festgestellt, dass die Serumspiegel bei gleichzeitiger Gabe von Inhibitoren und Induktoren der Cytochrom P450 (CYP) Isoenzyme CYP2D6 und CYP3A4 erhöht bzw. gesenkt wurden. Am Modell der P-gp Knockout Maus im Vergleich zu FVB Wildtyp Mäusen wurden Konzentrationsverläufe von Antipsychotika nach i.p. Gabe von Amisulprid, Aripiprazol, Dehydroaripiprazol, Clozapin, Desmethylclozapin, Haloperidol, Olanzapin, Quetiapin, Risperidon und 9-Hydroxyrisperidon sowie der Kontrollsubstanz Domperidon im Gehirn und Blut über 24 Stunden mittels HPLC-Methoden gemessen. Welchen Einfluss eine verminderte Expression von P-gp auf die Pharmakodynamik hat, wurde in zwei Verhaltenstests untersucht. Mit Hilfe des Rotarods wurden motorische Effekte der Arzneistoffe erfasst und mittels Radial Arm Water Maze kognitive Fähigkeiten. Risperidon und sein aktiver Metabolit 9-Hydroxyrisperidon waren die stärksten Substrate von P-gp. 10-fach höhere Konzentrationen im Gehirn der P-gp Knockout Mäuse führten zu 10-fach stärkeren Beeinträchtigungen in den pharmakodynamischen Untersuchungen im Vergleich zu Wildtyp Tieren. Amisulprid, Aripiprazol, Dehydroaripiprazol, Desmethylclozapin und Quetiapin konnten ebenfalls als Substrate von P-gp identifiziert werden. Olanzapin, Haloperidol und Clozapin wurden durch P-gp wenig bzw. nicht in ihrer Pharmakokinetik und –dynamik beeinflusst. Da P-gp von Nagern und Menschen nach derzeitiger Kenntnis in ihren Substrateigenschaften weitgehend übereinstimmen, muss bei einer Behandlung von schizophrenen Patienten mit Antipsychotika, die als Substrate von P-gp identifiziert wurden, davon ausgegangen werden, dass eine Veränderung der Expression oder Aktivität von P-gp, genetisch verursacht oder durch Medikamente bedingt, für das Therapieansprechen oder das Auftreten von Nebenwirkungen bedeutsam sind.