Neutral sphingomyelinase controls acute and chronic alcohol effects on brain activity.

Alcohol consumption is a widespread phenomenon throughout the world. However, how recreational alcohol use evolves into alcohol use disorder (AUD) remains poorly understood. The Smpd3 gene and its coded protein neutral sphingomyelinase (NSM) are associated with alcohol consumption in humans and alcohol-related behaviors in mice, suggesting a potential role in this transition. Using multiparametric magnetic resonance imaging, we characterized the role of NSM in acute and chronic effects of alcohol on brain anatomy and function in female mice. Chronic voluntary alcohol consumption (16 vol% for at least 6 days) affected brain anatomy in WT mice, reducing regional structure volume predominantly in cortical regions. Attenuated NSM activity prevented these anatomical changes. Functional MRI linked these anatomical adaptations to functional changes: Chronic alcohol consumption in mice significantly modulated resting state functional connectivity (RS FC) in response to an acute ethanol challenge (i.p. bolus of 2 g kg-1) in heterozygous NSM knockout (Fro), but not in WT mice. Acute ethanol administration in alcohol-naïve WT mice significantly decreased RS FC in cortical and brainstem regions, a key finding that was amplified in Fro mice. Regarding direct pharmacological effects, acute ethanol administration increased the regional cerebral blood volume (rCBV) in many brain areas. Here, chronic alcohol consumption otherwise attenuated the acute rCBV response in WT mice but enhanced it in Fro mice. Altogether, these findings suggest a differential role for NSM in acute and chronic functional brain responses to alcohol. Therefore, targeting NSM may be useful in the prevention or treatment of AUD.

Serotonin Signaling through Lipid Membranes.

Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.

Sex-specific pleiotropic changes in emotional behavior and alcohol consumption in human α-synuclein A53T transgenic mice during early adulthood.

Point mutations in the α-synuclein coding gene may lead to the development of Parkinson's disease (PD). PD is often accompanied by other psychiatric conditions, such as anxiety, depression, and drug use disorders, which typically emerge in adulthood. Some of these point mutations, such as SNCA and A30T, have been linked to behavioral effects that are not commonly associated with PD, especially regarding alcohol consumption patterns. In this study, we investigated whether the familial PD point mutation A53T is associated with changes in alcohol consumption behavior and emotional states at ages not yet characterized by α-synuclein accumulation. The affective and alcohol-drinking phenotypes remained unaltered in female PDGF-hA53T-synuclein-transgenic (A53T) mice during both early and late adulthood. Brain region-specific activation of ceramide-producing enzymes, acid sphingomyelinase (ASM), and neutral sphingomyelinase (NSM), known for their neuroprotective properties, was observed during early adulthood but not in late adulthood. In males, the A53T mutation was linked to a reduction in alcohol consumption in both early and late adulthood. However, male A53T mice displayed increased anxiety- and depression-like behaviors during both early and late adulthood. Enhanced ASM activity in the dorsal mesencephalon and ventral hippocampus may potentially contribute to these adverse behavioral effects of the mutation in males during late adulthood. In summary, the A53T gene mutation was associated with diverse changes in emotional states and alcohol consumption behavior long before the onset of PD, and these effects varied by sex. These alterations in behavior may be linked to changes in brain ceramide metabolism.

The beer component hordenine inhibits alcohol addiction-associated behaviours in mice.

Alcohol consumption is a widespread behaviour that may eventually result in the development of alcohol use disorder (AUD). Alcohol, however, is rarely consumed in pure form but in fruit- or corn-derived preparations, like beer. These preparations add other compounds to the consumption, which may critically modify alcohol intake and AUD risk. We investigated the effects of hordenine, a barley-derived beer compound on alcohol use-related behaviours. We found that the dopamine D2 receptor agonist hordenine (50 mg/kg) limited ongoing alcohol consumption and prophylactically diminished relapse drinking after withdrawal in mice. Although not having reinforcing effects on its own, hordenine blocked the establishment of alcohol-induced conditioned place preference (CPP). However, it independently enhanced alcohol CPP retrieval. Hordenine had a dose-dependent inhibitory effect on locomotor activity. Chronic hordenine exposure enhanced monoamine tissue levels in many brain regions. Further characterization revealed monoaminergic binding sites of hordenine and found a strong binding on the serotonin and dopamine transporters, and dopamine D3 , and adrenergic α1A and α2A receptor activation but no effects on GABAA receptor or glycinergic signalling. These findings suggest that natural ingredients of beer, like hordenine, may work as an inhibitory and use-regulating factor by their modulation of monoaminergic signalling in the brain.

Behavioural effects of APH199, a selective dopamine D4 receptor agonist, in animal models.

RATIONALE: The dopamine D4 receptors (DRD4) play a key role in numerous brain functions and are involved in the pathogenesis of various psychiatric disorders. DRD4 ligands have been shown to moderate anxiety, reward and depression-like behaviours, and cognitive impairments. Despite a series of promising but ambiguous findings, the therapeutic advantages of DRD4 stimulation remain elusive. OBJECTIVES: The investigation focused on the behavioural effects of the recently developed DRD4 agonist, APH199, to evaluate its impact on anxiety, anhedonia, behavioural despair, establishment and retrieval of alcohol reinforcement, and amphetamine (AMPH)-induced symptoms. METHODS: Male C57BL/6 J mice and Sprague-Dawley rats were examined in five independent experiments. We assessed APH199 (0.1-5 mg/kg, i.p.) effects on a broad range of behavioural parameters in the open field (OF) test, conditioned place preference test (CPP), elevated plus maze (EPM), light-dark box (LDB), novelty suppressed feeding (NSF), forced swim test (FST), sucrose preference test (SPT), AMPH-induced hyperlocomotion test (AIH), and prepulse inhibition (PPI) of the acoustic startle response in AMPH-sensitized rats. RESULTS: APH199 caused mild and sporadic anxiolytic and antidepressant effects in EPM and FST, but no remarkable impact on behaviour in other tests in mice. However, we found a significant increase in AMPH-induced hyperactivity, suggesting an exaggeration of the psychotic-like responses in the AMPH-sensitized rats. CONCLUSIONS: Our data challenged the hypothesis of the therapeutic benefits of DRD4 agonists, pointing out a possible aggravation of psychosis. We suggest a need for further preclinical studies to ensure the safety of antipsychotics with DRD4 stimulating properties.

Sex-specific effects of different types of prenatal stress on foetal testosterone levels and NMDA expression in mice.

Prenatal stress is a critical life event often resulting in mental illnesses in the offspring. The critical developmental processes, which might trigger a cascade of molecular events resulting in mental disorders in adulthood, are still to be elucidated. Here we proposed that sex hormones, particularly testosterone, might determine the "developmental programming" of long-term consequences of prenatal stress in foetuses of both sexes. We observed that severe prenatal stress in the model of repeated corticosterone injections enhanced brain levels of corticosterone and testosterone in male foetuses. The expression of GluN1 and GluN2A, but not GluN2B NMDA receptor subunits were significantly reduced in the brain of stressed male foetuses. However, female foetuses were protected against stress effects on the brain corticosterone and testosterone levels. More moderate types of stress, such as repeated restraint stress and chronic unpredictable stress, did not induce an increase in brain corticosterone in dams and testosterone concentrations in foetuses of both sexes. Moreover, chronic unpredictable stress reduced brain testosterone concentration in male foetuses. Altogether, changes in brain testosterone level might be one of the crucial mechanisms determining the development of long-term consequences of severe prenatal stress in male, but not in female foetuses. Targeting this mechanism might allow to develop principally new prediction and therapeutic approaches for prenatal stress-associated psychiatric disorders.

Adult alcohol drinking and emotional tone are mediated by neutral sphingomyelinase during development in males.

Alcohol use, abuse, and addiction, and resulting health hazards are highly sex-dependent with unknown mechanisms. Previously, strong links between the SMPD3 gene and its coded protein neutral sphingomyelinase 2 (NSM) and alcohol abuse, emotional behavior, and bone defects were discovered and multiple mechanisms were identified for females. Here we report strong sex-dimorphisms for central, but not for peripheral mechanisms of NSM action in mouse models. Reduced NSM activity resulted in enhanced alcohol consumption in males, but delayed conditioned rewarding effects. It enhanced the acute dopamine response to alcohol, but decreased monoaminergic systems adaptations to chronic alcohol. Reduced NSM activity increased depression- and anxiety-like behavior, but was not involved in alcohol use for the self-management of the emotional state. Constitutively reduced NSM activity impaired structural development in the brain and enhanced lipidomic sensitivity to chronic alcohol. While the central effects were mostly opposite to NSM function in females, similar roles in bone-mediated osteocalcin release and its effects on alcohol drinking and emotional behavior were observed. These findings support the view that the NSM and multiple downstream mechanism may be a source of the sex-differences in alcohol use and emotional behavior.

The system's genetics of depression and its somatic and mental comorbidities.

Depression is a common mood disorder characterised by high comorbidity with other mental and somatic diseases. New studies reveal a shared genetic base for mental core symptoms and somatic comorbidities. Functional analyses showed multiple brain-body pathways involved. This may help considering new therapeutic approaches for depression as a system's disorder.

Sphingolipid control of cognitive functions in health and disease.

Cognitive processes, particularly learning and memory, are crucial brain mechanisms mediating the successful adaptation of individuals to constantly changing environmental conditions. Impairments in memory performance during neurodegenerative disorders or dementias affect life quality of patients as well as their relatives and careers, and thus have a severe socio-economic impact. The last decades have viewed learning and memory as predominantly protein-mediated process at the synapses of brain neurons. However, recent developments propose a principally new, lipid-based mechanism that regulates cognition. Thereby, crucial members of cell membranes, the sphingolipids, emerged to play an outstanding role in learning and memory. The most abundant brain sphingolipids, ceramides and gangliosides, dynamically shape the composition of protein carrying cellular membranes. This, in turn, regulates protein signaling through the membranes and overall neuronal plasticity. An imbalance in sphingolipid composition and disrupted dynamics significantly affect normal functioning of cells and results in the development of multiple psychiatric and neurological disorders with cognitive impairments. Ceramides and gangliosides interact with a plethora of molecular pathways determining de novo learning and memory, as well as pathogenic pathways of neurodegenerative disorders and dementias of various origins. Considering sphingolipids as a trigger mechanism for learning and memory under physiological and pathological conditions, a principally new class of lipid-based preventive and therapeutic approaches to target cognitive impairments and dementias is emerging.

Neutral sphingomyelinase mediates the co-morbidity trias of alcohol abuse, major depression and bone defects.

Mental disorders are highly comorbid and occur together with physical diseases, which are often considered to arise from separate pathogenic pathways. We observed in alcohol-dependent patients increased serum activity of neutral sphingomyelinase. A genetic association analysis in 456,693 volunteers found associations of haplotypes of SMPD3 coding for NSM-2 (NSM) with alcohol consumption, but also with affective state, and bone mineralisation. Functional analysis in mice showed that NSM controls alcohol consumption, affective behaviour, and their interaction by regulating hippocampal volume, cortical connectivity, and monoaminergic responses. Furthermore, NSM controlled bone-brain communication by enhancing osteocalcin signalling, which can independently supress alcohol consumption and reduce depressive behaviour. Altogether, we identified a single gene source for multiple pathways originating in the brain and bone, which interlink disorders of a mental-physical co-morbidity trias of alcohol abuse-depression/anxiety-bone disorder. Targeting NSM and osteocalcin signalling may, thus, provide a new systems approach in the treatment of a mental-physical co-morbidity trias.

Neutral Sphingomyelinase is an Affective Valence-Dependent Regulator of Learning and Memory.

Sphingolipids and enzymes of the sphingolipid rheostat determine synaptic appearance and signaling in the brain, but sphingolipid contribution to normal behavioral plasticity is little understood. Here we asked how the sphingolipid rheostat contributes to learning and memory of various dimensions. We investigated the role of these lipids in the mechanisms of two different types of memory, such as appetitively and aversively motivated memory, which are considered to be mediated by different neural mechanisms. We found an association between superior performance in short- and long-term appetitively motivated learning and regionally enhanced neutral sphingomyelinase (NSM) activity. An opposite interaction was observed in an aversively motivated task. A valence-dissociating role of NSM in learning was confirmed in mice with genetically reduced NSM activity. This role may be mediated by the NSM control of N-methyl-d-aspartate receptor subunit expression. In a translational approach, we confirmed a positive association of serum NSM activity with long-term appetitively motivated memory in nonhuman primates and in healthy humans. Altogether, these data suggest a new sphingolipid mechanism of de-novo learning and memory, which is based on NSM activity.

Neutral ceramidase is a marker for cognitive performance in rats and monkeys.

BACKGROUND: Ceramides are lipid molecules determining cell integrity and intercellular signaling, and thus, involved in the pathogenesis of several psychiatric and neurodegenerative disorders. However, little is known about the role of particular enzymes of the ceramide metabolism in the mechanisms of normal behavioral plasticity. Here, we studied the contribution of neutral ceramidase (NC), one of the main enzymes mediating ceramide degradation, in the mechanisms of learning and memory in rats and non-human primates. METHODS: Naïve Wistar rats and black tufted-ear marmosets (Callithrix penicillata) were tested in several tests for short- and long-term memory and then divided into groups with various memory performance. The activities of NC and acid ceramidase (AC) were measured in these animals. Additionally, anxiety and depression-like behavior and brain levels of monoamines were assessed in the rats. RESULTS: We observed a predictive role of NC activity in the blood serum for superior performance of long-term object memory tasks in both species. A brain area analysis suggested that high NC activity in the ventral mesencephalon (VM) predicts better short-term memory performance in rats. High NC activity in the VM was also associated with worse long-term object memory, which might be mediated by an enhanced depression-like state and a monoaminergic imbalance. CONCLUSIONS: Altogether, these data suggest a role for NC in short- and long-term memory of various mammalian species. Serum activity of NC may possess a predictive role in the assessing the performance of certain types of memory.

A Stearoyl-Coenzyme A Desaturase Inhibitor Prevents Multiple Parkinson Disease Phenotypes in α-Synuclein Mice.

OBJECTIVE: Parkinson disease (PD) has useful symptomatic treatments that do not slow the neurodegenerative process, and no significant disease-modifying treatments are approved. A key therapeutic target in PD is α-synuclein (αS), which is both genetically implicated and accumulates in Lewy bodies rich in vesicles and other lipid membranes. Reestablishing αS homeostasis is a central goal in PD. Based on previous lipidomic analyses, we conducted a mouse trial of a stearoyl-coenzyme A desaturase (SCD) inhibitor ("5b") that prevented αS-positive vesicular inclusions and cytotoxicity in cultured human neurons. METHODS: Oral dosing and brain activity of 5b were established in nontransgenic mice. 5b in drinking water was given to mice expressing wild-type human αS (WT) or an amplified familial PD αS mutation (E35K + E46K + E61K ["3K"]) beginning near the onset of nigral and cortical neurodegeneration and the robust PD-like motor syndrome in 3K. Motor phenotypes, brain cytopathology, and SCD-related lipid changes were quantified in 5b- versus placebo-treated mice. Outcomes were compared to effects of crossing 3K to SCD1-/- mice. RESULTS: 5b treatment reduced αS hyperphosphorylation in E46K-expressing human neurons, in 3K neural cultures, and in both WT and 3K αS mice. 5b prevented subtle gait deficits in WT αS mice and the PD-like resting tremor and progressive motor decline of 3K αS mice. 5b also increased αS tetramers and reduced proteinase K-resistant lipid-rich aggregates. Similar benefits accrued from genetically deleting 1 SCD allele, providing target validation. INTERPRETATION: Prolonged reduction of brain SCD activity prevented PD-like neuropathology in multiple PD models. Thus, an orally available SCD inhibitor potently ameliorates PD phenotypes, positioning this approach to treat human α-synucleinopathies. ANN NEUROL 2021;89:74-90.

Cocaine attenuates acid sphingomyelinase activity during establishment of addiction-related behavior-A translational study in rats and monkeys.

Cocaine addiction is a severe psychiatric condition for which currently no effective pharmacotherapy is available. Brain mechanisms for the establishment of addiction-related behaviors are still not fully understood, and specific biomarkers for cocaine use are not available. Sphingolipids are major membrane lipids, which shape neuronal membrane composition and dynamics in the brain. Here, we investigated how chronic cocaine exposure during establishment of addiction-related behaviors affects the activity of the sphingolipid rheostat controlling enzymes in the brain of rats. As we detected specific effects on several enzymes in the brain, we tested whether the activity of selected enzymes in the blood may serve as potential biomarker for cocaine exposure in non-human primates (Callithrix penicillata). We found that intravenous cocaine self-administration led to a reduced mRNA expression of Cers1, Degs1 and Degs2, and Smpd1 in the prefrontal cortex of rats, as well as a reduction of Cers4 expression in the striatum. These effects reversed after 10 days of abstinence. Monkeys showed a robust cocaine-induced place preference (CPP). This coincided with a reduction in blood acid sphingomyelinase (ASM) activity after CPP establishment. This effect normalized after 15 days of abstinence. Altogether, these findings suggest that the establishment of cocaine addiction-related behaviors coincides with changes in the activity of sphingolipid controlling enzymes. In particular, blood ASM levels may serve as a translational biomarker for recent cocaine exposure.

Presynaptic vesicular accumulation is required for antipsychotic efficacy in psychotic-like rats.

BACKGROUND: The therapeutic effects of antipsychotic drugs (APDs) are mainly attributed to their postsynaptic inhibitory functions on the dopamine D2 receptor, which, however, cannot explain the delayed onset of full therapeutic efficacy. It was previously shown that APDs accumulate in presynaptic vesicles during chronic treatment and are released like neurotransmitters in an activity-dependent manner triggering an auto-inhibitory feedback mechanism. Although closely mirroring therapeutic action onset, the functional consequence of the APD accumulation process remained unclear. AIMS: Here we tested whether the accumulation of the APD haloperidol (HAL) is required for full therapeutic action in psychotic-like rats. METHODS: We designed a HAL analog compound (HAL-F), which lacks the accumulation property of HAL, but retains its postsynaptic inhibitory action on dopamine D2 receptors. RESULTS/OUTCOMES: By perfusing LysoTracker fluorophore-stained cultured hippocampal neurons, we confirmed the accumulation of HAL and the non-accumulation of HAL-F. In an amphetamine hypersensitization psychosis-like model in rats, we found that subchronic intracerebroventricularly delivered HAL (0.1 mg/kg/day), but not HAL-F (0.3-1.5 mg/kg/day), attenuates psychotic-like behavior in rats. CONCLUSIONS/INTERPRETATION: These findings suggest the presynaptic accumulation of HAL may serve as an essential prerequisite for its full antipsychotic action and may explain the time course of APD action. Targeting accumulation properties of APDs may, thus, become a new strategy to improve APD action.

Swiprosin1/EFhd2 is involved in the monoaminergic and locomotor responses of psychostimulant drugs.

Psychostimulants are widely abused drugs that may cause addiction in vulnerable individuals. While the reward circuitry of the brain is involved in addiction establishment, various pathways in the brain may provide protection at the molecular level that limits the acute and chronic effects of drugs. These targets may be used for strategies designed to prevent and treat addiction. Swiprosin-1/EF hand domain 2 (EFhd2) is a Ca2+ -binding cytoskeletal adaptor protein involved in sensation-seeking behaviour, anxiety and alcohol addiction. Here, we tested how EFhd2 contributes to the physiological and behavioural effects of the psychostimulant drugs methamphetamine (METH) and cocaine. An in vivo microdialysis study in EFhd2 knockout mice revealed that EFhd2 controls METH- and cocaine-induced changes in extracellular dopamine, serotonin and noradrenaline levels through different mechanisms in the nucleus accumbens and prefrontal cortex. Electrophysiological recordings in a slice preparation showed that a lack of EFhd2 increases dopaminergic neuronal activity in the ventral tegmental area and increases the sensitivity of neurons to stimulation. We report a role of EFhd2 in METH-induced locomotor activation and in the conditioned locomotor effects. No role, however, was observed in the establishment of METH- or cocaine-induced conditioned place preference. These findings may suggest that EFhd2 modulates the activity of the dopaminergic system and the neurochemical effects of METH and cocaine, which translate into a modulation of the behavioural effects of these drugs at the level of the acute and conditioned locomotor activity.

The selective FKBP51 inhibitor SAFit2 reduces alcohol consumption and reinstatement of conditioned alcohol effects in mice.

There is still no widely effective pharmacotherapy for alcohol addiction available in the clinic. FK506-binding protein 51 (FKBP51) is a negative regulator of the glucocorticoid receptor signaling pathway that regulates the stress-induced glucocorticoid feedback circuit. Here we asked whether selective inhibitors of FKBP51, exemplified by SAFit2, may serve as a new pharmacological strategy to reduce alcohol consumption and conditioned alcohol effects in a mouse model. We report that a relatively short treatment with SAFit2 (20 mg/kg, ip) reduces ongoing 16 vol% alcohol consumption when administered during free access to alcohol in a two-bottle free-choice test. SAFit2 was also able to reduce alcohol consumption when given during an abstinence period immediately before relapse. In contrast, SAFit2 did not affect alcohol consumption when given during a relapse period after repeated withdrawal from alcohol. SAFit2 (10 and 20 mg/kg, ip) showed no effects when used in an intermittent drinking schedule. When 20 vol% alcohol was only available every other day, SAFit2 had no effect on drinking, no matter whether given during a drinking episode or the day before. SAFit2 (2 and 20 mg/kg, ip) did not affect the expression of an alcohol-induced conditioned place preference (CPP). However, SAFit2 was able to inhibit alcohol-induced reinstatement of an extinguished CPP in a dose-dependent way. Altogether, these data may suggest pharmacological inhibition of FKBP51 as a viable strategy to reduce alcohol seeking and consumption.

Ceramides affect alcohol consumption and depressive-like and anxiety-like behavior in a brain region- and ceramide species-specific way in male mice.

Depression and alcohol dependence are associated with increased plasma ceramide concentrations in humans. Pharmacological increase in C16 ceramide concentrations in the dorsal hippocampus (DH) induced a depressive-like phenotype in naïve mice. However, the effects of C16 ceramide on alcohol consumption and anxiety-like behavior as well as the behavioral effects of other ceramide species are yet unknown. Therefore, we investigated whether repeated infusion of ceramides with different fatty acid chain lengths (C8, C16, and C20) into the DH and the basolateral amygdala (BLA) alter alcohol consumption, emotional behavior, and tissue monoamine levels. Our results revealed that C16, but not C8 and C20, ceramide altered alcohol drinking and emotional behavior in a brain region-specific way without altering tissue noradrenaline, dopamine, and serotonin levels in the prefrontal cortex, ventral striatum, and dorsal mesencephalon. In more detail, C16 ceramide increased alcohol consumption when infused into the BLA, but not when infused into the DH. Furthermore, C16 ceramide induced a depressive-like phenotype when infused into the DH, but a predominantly anxiogenic-like phenotype (in a non-social, but not a social context) when infused into the BLA. In turn, alcohol drinking normalized C16 ceramide-induced depressive-like and anxiogenic-like phenotypes. This study demonstrates a complex ceramide species-specific and brain region-specific modulation of alcohol consumption and emotional behavior in mice and provides the framework for future studies investigating the involvement of distinct ceramide species in the regulation of emotional behavior.

Enhanced Alcohol Preference and Anxiolytic Alcohol Effects in Niemann-Pick Disease Model in Mice.

Major depression and alcohol use disorder are severe psychiatric diseases affecting the world's population with high comorbidity level. However, the pathogenesis of this comorbidity remains unclear, and no selective treatment for this condition is available. A pathogenic pathway and a possible therapeutic target for the treatment of depression-alcoholism comorbidity based on the hyperfunction of acid sphingomyelinase (Asm) were recently suggested. Here we analyzed the effects of alcohol on the depression/anxiety state of homozygous Asm-knockout mice (Asm - /-), which can be considered as a model of an early stage of Niemann-Pick disease, as well as their drinking pattern under normal and stress conditions. It was observed that forced treatment with alcohol (2 g/kg, i.p.) reduces the anxiety level of Asm-/- mice as measured in the elevated plus maze (EPM) test, but enhances the depression level in the forced swim test (FST). The analysis of drinking pattern of these animals in a free-choice alcohol drinking paradigm revealed higher alcohol intake and preference in Asm-/- mice compared to wild type (wt) littermates. However, this difference was overwritten by the stress exposure. Stronger sedating effects of alcohol were observed in Asm-/- mice compared to wt animals in the loss of righting reflex test after single and repeated alcohol injections (3 g/kg, i.p.). Altogether, the present findings might indicate an Asm involvement in the mechanisms of comorbidity between alcoholism and anxiety/depression.

Layer-specific axonal degeneration of serotonergic fibers in the prefrontal cortex of aged A53T α-synuclein-expressing mice.

Axonal pathology precedes dopaminergic cell loss in Parkinson's disease (PD), indicating a dying back axonopathy of nigrostriatal projections. Although most attention focused on the dopaminergic system, increasing evidence implies a compromised serotonergic system in PD as well. By combining immunohistological and biochemical approaches, a profound layer-specific reduction of the serotonergic input to the prefrontal cortex (PFC) layers II and V/VI in aged mutant A53T α-synuclein-expressing mice (A53T mice) was detected. In addition, the altered fiber network was characterized by swollen axons and enlarged axonal varicosities within all PFC layers, but most pronounced in PFC layer I. Although prefrontal serotonin levels and synaptic protein expression were preserved, aged A53T mice showed increased levels of kinesin family member 1a and vesicular monoamine transporter 2. Together with increased tryptophan hydroxylase 2 mRNA levels in the raphe nuclei and an elevated serotonin receptor 1b expression in the PFC, these findings point to compensatory mechanisms within the serotonergic system to overcome the reduced neuritic input to the PFC in this transgenic animal model for PD.