Treatment with the calcineurin inhibitor and immunosuppressant cyclosporine A impairs sensorimotor gating in Dark Agouti rats.

RATIONALE: Calcineurin is a protein regulating cytokine expression in T lymphocytes and calcineurin inhibitors such as cyclosporine A (CsA) are widely used for immunosuppressive therapy. It also plays a functional role in distinct neuronal processes in the central nervous system. Disturbed information processing as seen in neuropsychiatric disorders is reflected by deficient sensorimotor gating, assessed as prepulse inhibition (PPI) of the acoustic startle response (ASR). OBJECTIVE: Patients who require treatment with immunosuppressive drugs frequently display neuropsychiatric alterations during treatment with calcineurin inhibitors. Importantly, knockout of calcineurin in the forebrain of mice is associated with cognitive impairments and symptoms of schizophrenia-like psychosis as seen after treatment with stimulants. METHODS: The present study investigated in rats effects of systemic acute and subchronic administration of CsA on sensorimotor gating. Following a single injection with effective doses of CsA, adult healthy male Dark Agouti rats were tested for PPI. For subchronic treatment, rats were injected daily with the same doses of CsA for 1 week before PPI was assessed. Since calcineurin works as a modulator of the dopamine pathway, activity of the enzyme tyrosine hydroxylase was measured in the prefrontal cortex and striatum after accomplishment of the study. RESULTS: Acute and subchronic treatment with the calcineurin inhibitor CsA disrupted PPI at a dose of 20 mg/kg. Concomitantly, following acute CsA treatment, tyrosine hydroxylase activity was reduced in the prefrontal cortex, which suggests that dopamine synthesis was downregulated, potentially reflecting a stimulatory impact of CsA on this neurotransmitter system. CONCLUSIONS: The results support experimental and clinical evidence linking impaired calcineurin signaling in the central nervous system to the pathophysiology of neuropsychiatric symptoms. Moreover, these findings suggest that therapy with calcineurin inhibitors may be a risk factor for developing neurobehavioral alterations as observed after the abuse of psychomotor stimulant drugs.

Forced exercise activates the NrF2 pathway in the striatum and ameliorates motor and behavioral manifestations of Parkinson's disease in rotenone-treated rats.

BACKGROUND: Parkinson's disease (PD) is a common neurodegenerative disorder characterized by progressive loss of nigrostriatal dopaminergic neurons leading to dopamine depletion and problems of movement, emotions, and cognition. While the pathogenesis of PD is not clear, damage of dopaminergic neurons by oxygen-derived free radicals is considered an important contributing mechanism. This study aimed to evaluate the role of treadmill exercise in male Wister rats as a single treatment and as an aid-therapy with L-dopa for rotenone-induced PD. To study the role of the Nrf2- ARE pathway as a mechanism involved in exercise-associated improvement in rotenone-induced PD in rats. METHOD: Animals were divided into 5 groups, (Control, rotenone, rotenone\exercise, rotenone\L-dopa, and rotenone\exercise\L-dopa (combination)groups). After the PD induction, rats in the rotenone\exercise and combination groups were daily treadmill exercised for 4 weeks. RESULTS: Treadmill exercise significantly improved behavioral and motor aspects of rotenone-induced PD. When treadmill exercise was introduced as a single intervention, it amended most behavioral aspects of PD, gait fully corrected, short-term memory, and motor coordination. Where L-dopa corrected locomotor activity and motor coordination but failed to improve short-term memory and only partially corrected the gait of rotenone-treated rats. When treadmill exercise was combined with L-dopa, all features of PD were corrected. It was found that exercise upregulated some of its associative genes to Nrf2 pathways such as TFAM, Nrf2 and NQO.1 mRNA expression. CONCLUSION: This study suggests that forced exercise improved parkinsonian like features by activating the Nrf2 pathway.

Loss of striatal tyrosine-hydroxylase interneurons impairs instrumental goal-directed behavior.

The striatum mediates a broad range of cognitive and motor functions. Within the striatum, recently discovered tyrosine hydroxylase expressing interneurons (THINs) provide a source of intrastriatal synaptic connectivity that is critical for regulating striatal activity, yet the role of THIN's in behavior remains unknown. Given the important role of the striatum in reward-based behaviors, we investigated whether loss of striatal THINs would impact instrumental behavior in mice. We selectively ablated striatal THINs in TH-Cre mice using chemogenetic techniques, and then tested THIN-lesioned or control mice on three reward-based striatal-dependent instrumental tests: (a) progressive ratio test; (b) choice test following selective-satiety induced outcome devaluation; (c) outcome reinstatement test. Both striatal-THIN-lesioned and control mice acquired an instrumental response for flavored food pellets, and their behavior did not differ in the progressive ratio test, suggesting intact effort to obtain rewards. However, striatal THIN lesions markedly impaired choice performance following selective-satiety induced outcome devaluation. Unlike control mice, THIN-lesioned mice did not adjust their choice of actions following a change in outcome value. In the outcome reinstatement test THIN-lesioned and control mice showed response invigoration by outcome presentation, suggesting the incentive properties of outcomes were not disrupted by THIN lesions. Overall, we found that striatal THIN lesions selectively impaired goal-directed behavior, while preserving motoric and appetitive behaviors. These findings are the first to describe a function of striatal THINs in reward-based behavior, and further illustrate the important role for intrastriatal interneuronal connectivity in behavioral functions ascribed to the striatum more generally.

In vitro phosphodiesterase 10A (PDE10A) binding in whole hemisphere human brain using the PET radioligand [18F]MNI-659.

Highly specific and sensitive biomarkers for pathologies related to dysfunctions in the basal ganglia circuit are of great value to assess therapeutic efficacy not only clinically to establish an early diagnosis, but also in terms of monitoring the efficacy of therapeutic interventions and decelerated neurodegeneration. The phosphodiesterase 10A (PDE10A) enzyme plays a central role in striatal signaling and is implicated in several neuropsychiatric disorders involving striatal pathology, such as Huntingtons disease (HD) and schizophrenia. Inhibition of PDE10A activates the neurons in the striatum and consequently leads to alteration of behavioral aspects modulated by the striatal circuit. [18F]MNI-659, (2-(2-(3-(4-(2-[18F]fluoroethoxy)phenyl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione), is a newly developed PET radioligand that shows a high binding to PDE10A in the human brain in vivo. In the present study, we examined the in vitro binding of [18F]MNI-659 in human postmortem brain to gain a better understanding of the presence, density, disease-related alterations and therapy related to changes in PDE10A expression. The results show high specific binding of [18F]MNI-659 in the caudate nucleus, putamen and the hippocampal formation. Low specific [18F]MNI-659 binding was detected in nucleus accumbens in comparison to the caudate nucleus and putamen. In vitro binding studies with [18F]MNI-659 will facilitate in elucidating better understanding of the role of PDE10A activity in health and disease that may lead to new diagnostic opportunities in HD.

Oxadiazon affects the expression and activity of aldehyde dehydrogenase and acylphosphatase in human striatal precursor cells: A possible role in neurotoxicity.

Exposure to herbicides can induce long-term chronic adverse effects such as respiratory diseases, malignancies and neurodegenerative diseases. Oxadiazon, a pre-emergence or early post-emergence herbicide, despite its low acute toxicity, may induce liver cancer and may exert adverse effects on reproductive and on endocrine functions. Unlike other herbicides, there are no indications on neurotoxicity associated with long-term exposure to oxadiazon. Therefore, we have analyzed in primary neuronal precursor cells isolated from human striatal primordium the effects of non-cytotoxic doses of oxadiazon on neuronal cell differentiation and migration, and on the expression and activity of the mitochondrial aldehyde dehydrogenase 2 (ALDH2) and of the acylphosphatase (ACYP). ALDH2 activity protects neurons against neurotoxicity induced by toxic aldehydes during oxidative stress and plays a role in neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease. ACYP is involved in ion transport, cell differentiation, programmed cell death and cancer, and increased levels of ACYP have been revealed in fibroblasts from patients affected by Alzheimer's disease. In this study we demonstrated that non-cytotoxic doses of oxadiazon were able to inhibit neuronal striatal cell migration and FGF2- and BDNF-dependent differentiation towards neuronal phenotype, and to inhibit the expression and activity of ALDH2 and to increase the expression and activity of ACYP2. In addition, we have provided evidence that in human primary neuronal precursor striatal cells the inhibitory effects of oxadiazon on cell migration and differentiation towards neuronal phenotype were achieved through modulation of ACYP2. Taken together, our findings reveal for the first time that oxadiazon could exert neurotoxic effects by impairing differentiative capabilities of primary neuronal cells and indicate that ALDH2 and ACYP2 are relevant molecular targets for the neurotoxic effects of oxadiazon, suggesting a potential role of this herbicide in the onset of neurodegenerative diseases.

Amitraz changes NE, DA and 5-HT biosynthesis and metabolism mediated by alterations in estradiol content in CNS of male rats.

Amitraz is a formamidine insecticide/acaricide that alters different neurotransmitters levels, among other neurotoxic effects. Oral amitraz exposure (20, 50 and 80 mg/kg bw, 5 days) has been reported to increase serotonin (5-HT), norepinephrine (NE) and dopamine (DA) content and to decrease their metabolites and turnover rates in the male rat brain, particularly in the striatum, prefrontal cortex, and hippocampus. However, the mechanisms by which these alterations are produced are not completely understood. One possibility is that amitraz monoamine oxidase (MAO) inhibition could mediate these effects. Alternatively, it alters serum concentrations of sex steroids that regulate the enzymes responsible for these neurotransmitters synthesis and metabolism. Thus, alterations in sex steroids in the brain could also mediate the observed effects. To test these hypothesis regarding possible mechanisms, we treated male rats with 20, 50 and 80 mg/kg bw for 5 days and then isolated tissue from striatum, prefrontal cortex, and hippocampus. We then measured tissue levels of expression and/or activity of MAO, catechol-O-metyltransferase (COMT), dopamine-ß-hydroxylase (DBH), tyrosine hydroxylase (TH) and tryptophan hydroxylase (TRH) as well as estradiol levels in these regions. Our results show that amitraz did not inhibit MAO activity at these doses, but altered MAO, COMT, DBH, TH and TRH gene expression, as well as TH and TRH activity and estradiol levels. The alteration of these enzymes was partially mediated by dysregulation of estradiol levels. Our present results provide new understanding of the mechanisms contributing to the harmful effects of amitraz.

Ursodeoxycholic Acid Ameliorates Apoptotic Cascade in the Rotenone Model of Parkinson's Disease: Modulation of Mitochondrial Perturbations.

The recent emergence of ursodeoxycholic acid (UDCA) as a contender in modifying neurotoxicity in human dopaminergic cells as well as its recognized anti-apoptotic and anti-inflammatory potentials in various hepatic pathologies raised impetus in investigating its anti-parkinsonian effect in rat rotenone model. UDCA prominently improved motor performance in the open field test and halted the decline in the striatal dopamine content. Meanwhile, it improved mitochondrial function as verified by elevation of ATP associated with preservation of mitochondrial integrity as portrayed in the electron microscope examination. In addition, through its anti-inflammatory potential, UDCA reduced the rotenone-induced nuclear factor-κB expression and tumor necrosis factor alpha level. Furthermore, UDCA amended alterations in Bax and Bcl-2 and reduced the activities of caspase-8, caspase-9, and caspase-3, indicating that it suppressed rotenone-induced apoptosis via modulating both intrinsic and extrinsic pathways. In conclusion, UDCA can be introduced as a novel approach for the management of Parkinson's disease via anti-apoptotic and anti-inflammatory mechanisms. These effects are probably linked to dopamine synthesis and mitochondrial regulation.

Beneficial effects of lycopene against haloperidol induced orofacial dyskinesia in rats: Possible neurotransmitters and neuroinflammation modulation.

Tardive Dyskinesia is a severe side effect of chronic neuroleptic treatment consisting of abnormal involuntary movements, characterized by orofacial dyskinesia. The study was designed to investigate the protective effect of lycopene against haloperidol induced orofacial dyskinesia possibly by neurochemical and neuroinflammatory modulation in rats. Rats were administered with haloperidol (1mg/kg, i.p for 21 days) to induce orofacial dyskinesia. Lycopene (5 and 10mg/kg, p.o) was given daily 1hour before haloperidol treatment for 21 days. Behavioral observations (vacuous chewing movements, tongue protrusions, facial jerking, rotarod activity, grip strength, narrow beam walking) were assessed on 0th, 7th(,) 14th(,) 21st day after haloperidol treatment. On 22nd day, animals were killed and striatum was excised for estimation of biochemical parameters (malondialdehyde, nitrite and endogenous enzyme (GSH), pro-inflammatory cytokines [Tumor necrosis factor, Interleukin 1ß, Interleukin 6] and neurotransmitters level (dopamine, serotonin, nor epinephrine, 5-Hydroxyindole acetic acid (5-HIAA), Homovanillic acid, 3,4- dihydroxyphenylacetic acid. Haloperidol treatment for 21 days impaired muscle co-ordination, motor activity and grip strength with an increased in orofacial dyskinetic movements. Further free radical generation increases MDA and nitrite levels, decreasing GSH levels in striatum. Neuroinflammatory markers were significantly increased with decrease in neurotransmitters levels. Lycopene (5 and 10mg/kg, p.o) treatment along with haloperidol significantly attenuated impairment in behavioral, biochemical, neurochemical and neuroinflammatory markers. Results of the present study attributed the therapeutic potential of lycopene in the treatment (prevented or delayed) of typical antipsychotic induced orofacial dyskinesia.

Preclinical evaluation of a promising C-11 labeled PET tracer for imaging phosphodiesterase 10A in the brain of living subject.

Phosphodiesterase 10A (PDE10A) plays a key role in the regulation of brain striatal signaling. A PET tracer for PDE10A may serve as a tool to evaluate PDE10A expression in vivo in central nervous system disorders with striatal pathology. Here, we further characterized the binding properties of a previously reported radioligand we developed for PDE10A, [(11)C]TZ1964B, in rodents and nonhuman primates (NHPs). The tritiated counterpart [(3)H]TZ1964B was used for in vitro binding characterizations in rat striatum homogenates and in vitro autoradiographic studies in rat brain slices. The carbon-11 labeled [(11)C]TZ1964B was utilized in the ex vivo autoradiography studies for the brain of rats and microPET imaging studies for the brain of NHPs. MicroPET scans of [(11)C]TZ1964B in NHPs were conducted at baseline, as well as with using a selective PDE10A inhibitor MP-10 for either pretreatment or displacement. The in vivo regional target occupancy (Occ) was obtained by pretreating with different doses of MP-10 (0.05-2.00 mg/kg). Both in vitro binding assays and in vitro autoradiographic studies revealed a nanomolar binding affinity of [(3)H]TZ1964B to the rat striatum. The striatal binding of [(3)H]TZ1964B and [(11)C]TZ1964B was either displaced or blocked by MP-10 in rats and NHPs. Autoradiography and microPET imaging confirmed that the specific binding of the radioligand was found in the striatum but not in the cerebellum. Blocking studies also confirmed the suitability of the cerebellum as an appropriate reference region. The binding potentials (BPND) of [(11)C]TZ1964B in the NHP striatum that were calculated using either the Logan reference model (LoganREF, 3.96 ± 0.17) or the simplified reference tissue model (SRTM, 4.64 ± 0.47), with the cerebellum as the reference region, was high and had good reproducibility. The occupancy studies indicated a MP-10 dose of 0.31 ± 0.09 mg/kg (LoganREF)/0.45 ± 0.17mg/kg (SRTM) occupies 50% striatal PDE10A binding sites. Studies in rats and NHPs demonstrated radiolabeled TZ1964B has a high binding affinity and good specificity for PDE10A, as well as favorable in vivo pharmacokinetic properties and binding profiles. Our data suggests that [(11)C]TZ1964B is a promising radioligand for in vivo imaging PDE10A in the brain of living subject.

Huntington's disease: Neural dysfunction linked to inositol polyphosphate multikinase.

Huntington's disease (HD) is a progressive neurodegenerative disease caused by a glutamine repeat expansion in mutant huntingtin (mHtt). Despite the known genetic cause of HD, the pathophysiology of this disease remains to be elucidated. Inositol polyphosphate multikinase (IPMK) is an enzyme that displays soluble inositol phosphate kinase activity, lipid kinase activity, and various noncatalytic interactions. We report a severe loss of IPMK in the striatum of HD patients and in several cellular and animal models of the disease. This depletion reflects mHtt-induced impairment of COUP-TF-interacting protein 2 (Ctip2), a striatal-enriched transcription factor for IPMK, as well as alterations in IPMK protein stability. IPMK overexpression reverses the metabolic activity deficit in a cell model of HD. IPMK depletion appears to mediate neural dysfunction, because intrastriatal delivery of IPMK abates the progression of motor abnormalities and rescues striatal pathology in transgenic murine models of HD.

Age-related alterations in the expression of genes and synaptic plasticity associated with nitric oxide signaling in the mouse dorsal striatum.

Age-related alterations in the expression of genes and corticostriatal synaptic plasticity were studied in the dorsal striatum of mice of four age groups from young (2-3 months old) to old (18-24 months of age) animals. A significant decrease in transcripts encoding neuronal nitric oxide (NO) synthase and receptors involved in its activation (NR1 subunit of the glutamate NMDA receptor and D1 dopamine receptor) was found in the striatum of old mice using gene array and real-time RT-PCR analysis. The old striatum showed also a significantly higher number of GFAP-expressing astrocytes and an increased expression of astroglial, inflammatory, and oxidative stress markers. Field potential recordings from striatal slices revealed age-related alterations in the magnitude and dynamics of electrically induced long-term depression (LTD) and significant enhancement of electrically induced long-term potentiation in the middle-aged striatum (6-7 and 12-13 months of age). Corticostriatal NO-dependent LTD induced by pharmacological activation of group I metabotropic glutamate receptors underwent significant reduction with aging and could be restored by inhibition of cGMP hydrolysis indicating that its age-related deficit is caused by an altered NO-cGMP signaling cascade. It is suggested that age-related alterations in corticostriatal synaptic plasticity may result from functional alterations in receptor-activated signaling cascades associated with increasing neuroinflammation and a prooxidant state.

STEP levels are unchanged in pre-frontal cortex and associative striatum in post-mortem human brain samples from subjects with schizophrenia, bipolar disorder and major depressive disorder.

Increased protein levels of striatal-enriched tyrosine phosphatase (STEP) have recently been reported in postmortem schizophrenic cortex. The present study sought to replicate this finding in a separate cohort of postmortem samples and to extend observations to striatum, including subjects with bipolar disorder and major depressive disorder in the analysis. No statistically significant changes between disease and control subjects were found in STEP mRNA or protein levels in dorsolateral prefrontal cortex or associative striatum. Although samples were matched for several covariates, postmortem interval correlated negatively with STEP protein levels, emphasizing the importance of including these analyses in postmortem studies.

Omega-3 fatty acids prevent the ketamine-induced increase in acetylcholinesterase activity in an animal model of schizophrenia.

AIMS: Schizophrenia is a debilitating neurodevelopmental disorder that is associated with dysfunction in the cholinergic system. Early prevention is a target of treatment to improve long-term outcomes. Therefore, we evaluated the preventive effects of omega-3 fatty acids on AChE activity in the prefrontal cortex, hippocampus and striatum in an animal model of schizophrenia. MAIN METHODS: Young Wistar rats (30 days old) were initially treated with omega-3 fatty acids or vehicle alone. Animals received ketamine to induce an animal model of schizophrenia or saline plus omega-3 fatty acids or vehicle alone for 7 consecutive days beginning on day 15. A total of 22 days elapsed between the treatment and intervention. Animals were sacrificed, and brain structures were dissected to evaluate AChE activity and gene expression. KEY FINDINGS: Our results demonstrate that ketamine increased AChE activity in these three structures, and omega-3 fatty acids plus ketamine showed lower values for the studied parameters, which indicate a partial preventive mechanism of omega-3 fatty acid supplementation. We observed no effect on AChE expression. Together, these results indicate that omega-3 fatty acid supplementation effectively reduced AChE activity in an animal model of schizophrenia in all studied structures. In conclusion, the present study provides evidence that ketamine and omega-3 fatty acids affect the cholinergic system, and this effect may be associated with the physiopathology of schizophrenia. Further studies are required to investigate the mechanisms that are associated with this effect.

Adenylyl cyclase-5 in the dorsal striatum function as a molecular switch for the generation of behavioral preferences for cue-directed food choices.

BACKGROUND: Behavioral choices in habits and innate behaviors occur automatically in the absence of conscious selection. These behaviors are not easily modified by learning. Similar types of behaviors also occur in various mental illnesses including drug addiction, obsessive-compulsive disorder, schizophrenia, and autism. However, underlying mechanisms are not clearly understood. In the present study, we investigated the molecular mechanisms regulating unconditioned preferred behaviors in food-choices. RESULTS: Mice lacking adenylyl cyclase-5 (AC5 KO mice), which is preferentially expressed in the dorsal striatum, consumed food pellets nearly one after another in cages. AC5 KO mice showed aversive behaviors to bitter tasting quinine, but they compulsively chose quinine-containing AC5 KO-pellets over fresh pellets. The unusual food-choice behaviors in AC5 KO mice were due to the gain of behavioral preferences for food pellets containing an olfactory cue, which wild-type mice normally ignored. Such food-choice behaviors in AC5 KO mice disappeared when whiskers were trimmed. Conversely, whisker trimming in wildtype mice induced behavioral preferences for AC5 KO food pellets, indicating that preferred food-choices were not learned through prior experience. Both AC5 KO mice and wildtype mice with trimmed whiskers had increased glutamatergic input from the barrel cortex into the dorsal striatum, resulting in an increase in the mGluR1-dependent signaling cascade. The siRNA-mediated inhibition of mGluR1 in the dorsal striatum in AC5 KO mice and wildtype mice with trimmed whiskers abolished preferred choices for AC5 KO food pellets, whereas siRNA-mediated inhibition of mGluR3 glutamate receptors in the dorsal striatum in wildtype mice induced behavioral preferences for AC5 KO food pellets, thus mimicking AC5 KO phenotypes. CONCLUSIONS: Our results show that the gain and loss of behavioral preferences for a specific cue-directed option were regulated by specific cellular factors in the dorsal striatum, such that the preferred food choices were switched on when either the mGluR3-AC5 pathway was inactive or the mGluR1 pathway was active, whereas the preferred food-choices were switched off when mGluR1 or its downstream pathway was suppressed. These results identify the AC5 and mGluR system in the dorsal striatum as molecular on/off switches to direct decisions on behavioral preferences for cue-oriented options.

Protective effects of phosphodiesterase-1 (PDE1) and ATP sensitive potassium (KATP) channel modulators against 3-nitropropionic acid induced behavioral and biochemical toxicities in experimental Huntington׳s disease.

Huntington׳s disease (HD), a devastating neurodegenerative disorder, is characterized by weight loss, impairment of motor function, cognitive dysfunction, neuropsychiatric disturbances and striatal damage. Phosphodiesterase-1 (PDE1) has been implicated in various neurological diseases. Mitochondrial potassium channels in the brain take part in neuroprotection. This study has been structured to investigate the role of vinpocetine, a selective PDE1 inhibitor as well as nicorandil, selective ATP sensitive potassium (KATP) channel opener in 3-nitropropionic acid (3-NP) induced HD symptoms in rats. Systemic administration of 3-NP significantly, reduced body weight, impaired locomotion, grip strength and impaired cognition. 3-NP elicited marked oxidative stress in the brain (enhanced malondialdehyde-MDA, reduced glutathione-GSH content, superoxide dismutase-SOD and catalase-CAT), elevated brain acetylcholinesterase activity and inflammation (myeloperoxidase-MPO), with marked nitrosative stress (nitrite/nitrate) in the brain. 3-NP has also induced mitochondrial dysfunction (impaired mitochondrial NADH dehydrogenase-complex I, succinate dehydrogenase-complex II and cytochrome oxidase-complex IV) activities in the striatum of the rat. Tetrabenazine was used as a positive control. Treatment with vinpocetine, nicorandil and tetrabenazine ameliorated 3-NP induced reduction in body weight, impaired locomotion, grip strength and impaired cognition. Treatment with these drugs reduced brain striatum oxidative (MDA, GSH, SOD and CAT) and nitrosative (nitrite/nitrate) stress, acetylcholinesterase activity, inflammation and mitochondrial dysfunctions. These results indicate that vinpocetine, a selective PDE1 inhibitor and nicorandil, a KATP channel opener have attenuated 3-NP induced experimental HD. Hence, pharmacological modulation of PDE1 as well as KATP channels may be considered as potential research targets for mitigation of HD.

Effect of chronic antipsychotic treatment on striatal phosphodiesterase 10A levels: a [¹¹C]MP-10 PET rodent imaging study with ex vivo confirmation.

A number of phosphodiesterase 10A (PDE10) inhibitors are about to undergo clinical evaluation for their efficacy in treating schizophrenia. As phosphodiesterases are in the same signalling pathway as dopamine D2 receptors, it is possible that prior antipsychotic treatment could influence these enzyme systems in patients. Chronic, in contrast to acute, antipsychotic treatment has been reported to increase brain PDE10A levels in rodents. The aim of this study was to confirm these findings in a manner that can be translated to human imaging studies to understand its consequences. Positron emission tomography (PET) scanning was used to evaluate PDE10A enzyme availability, after chronic haloperidol administration, using a specific PDE10A ligand ([(11)C]MP-10). The binding of [(11)C]MP-10 in the striatum and the cerebellum was measured in rodents and a simplified reference tissue model (SRTM) with cerebellum as the reference region was used to determine the binding potential (BPND). In rats treated chronically with haloperidol (2 mg kg(-1) per day), there was no significant difference in PDE10A levels compared with the vehicle-treated group (BPND±s.d.: 3.57 ± 0.64 versus 2.86 ± 0.71). Following PET scans, ex vivo analysis of striatal brain tissue for PDE10A mRNA (Pde10a) and PDE10A enzyme activity showed no significant difference. Similarly, the PDE10A protein content determined by western blot analysis was similar between the two groups, contrary to an earlier finding. The results of the study indicate that prior exposure to antipsychotic medication in rodents does not alter PDE10A levels.

Inhibition of striatal-enriched tyrosine phosphatase 61 in the dorsomedial striatum is sufficient to increased ethanol consumption.

The STriatal-Enriched protein tyrosine Phosphatase 61 (STEP61 ) inhibits the activity of the tyrosine kinase Fyn and dephosphorylates the GluN2B subunit of the NMDA receptor, whereas the protein kinase A phosphorylation of STEP61 inhibits the activity of the phosphatase (Pharmacol. Rev., 64, , p. 65). Previously, we found that ethanol activates Fyn in the dorsomedial striatum (DMS) leading to GluN2B phosphorylation, which, in turn, underlies the development of ethanol intake (J. Neurosci., 30, , p. 10187). Here, we tested the hypothesis that inhibition of STEP61 by ethanol is upstream of Fyn/GluN2B. We show that exposure of mice to ethanol increased STEP61 phosphorylation in the DMS, which was maintained after withdrawal and was not observed in other striatal regions. Specific knockdown of STEP61 in the DMS of mice enhanced ethanol-mediated Fyn activation and GluN2B phosphorylation, and increased ethanol intake without altering the level of water, saccharine, quinine consumption or spontaneous locomotor activity. Together, our data suggest that blockade of STEP61 activity in response to ethanol is sufficient for the activation of the Fyn/GluN2B pathway in the DMS. Being upstream of Fyn and GluN2B, inactive STEP61 in the DMS primes the induction of ethanol intake. We show that ethanol-mediated inhibition of STEP61 in the DMS leads to Fyn activation and GluN2B phosphorylation. (a) Under basal conditions, active STEP61 inhibits Fyn activity and dephosphorylates GluN2B. (b) Ethanol leads to the phosphorylation of STEP61 on a specific inhibitory site. The inhibition of STEP61 activity contributes to the activation of Fyn in response to ethanol, which, in turn, phosphorylates GluN2B. These molecular adaptations in the DMS promote ethanol drinking.

Chronic overload of SEPT4, a parkin substrate that aggregates in Parkinson's disease, causes behavioral alterations but not neurodegeneration in mice.

BACKGROUND: In autosomal recessive early-onset Parkinsonism (PARK2), the pathogenetic process from the loss of function of a ubiquitin ligase parkin to the death of dopamine neurons remains unclear. A dominant hypothesis attributes the neurotoxicity to accumulated substrates that are exempt from parkin-mediated degradation. Parkin substrates include two septins; SEPT4/CDCrel-2 which coaggregates with α-synuclein as Lewy bodies in Parkinson's disease, and its closest homolog SEPT5/CDCrel-1/PNUTL1 whose overload with viral vector can rapidly eliminate dopamine neurons in rats. However, chronic effects of pan-neural overload of septins have never been examined in mammals. To address this, we established a line of transgenic mice that express the largest gene product SEPT4(54kDa) via the prion promoter in the entire brain. RESULTS: Histological examination and biochemical quantification of SEPT4-associated proteins including α-synuclein and the dopamine transporter in the nigrostriatal dopamine neurons found no significant difference between Sept4(Tg/+) and wild-type littermates. Thus, the hypothetical pathogenicity by the chronic overload of SEPT4 alone, if any, is insufficient to trigger neurodegenerative process in the mouse brain. Intriguingly, however, a systematic battery of behavioral tests revealed unexpected abnormalities in Sept4(Tg/+) mice that include consistent attenuation of voluntary activities in distinct behavioral paradigms and altered social behaviors. CONCLUSIONS: Together, these data indicate that septin dysregulations commonly found in postmortem human brains with Parkinson's disease, schizophrenia and bipolar disorders may be responsible for a subset of behavioral abnormalities in the patients.

Castration induces Parkinson disease pathologies in young male mice via inducible nitric-oxide synthase.

Although Parkinson disease (PD) is a progressive neurodegenerative disorder, available animal models do not exhibit irreversible neurodegeneration, and this is a major obstacle in finding out an effective drug against this disease. Here we delineate a new irreversible model to study PD pathogenesis. The model is based on simple castration of young male mice. Levels of inducible nitric-oxide synthase (iNOS), glial markers (glial fibrillary acidic protein and CD11b), and α-synuclein were higher in nigra of castrated male mice than normal male mice. On the other hand, after castration, the level of glial-derived neurotrophic factor (GDNF) markedly decreased in the nigra of male mice. Accordingly, castration also induced the loss of tyrosine hydroxylase-positive neurons in the nigra and decrease in tyrosine hydroxylase-positive fibers and neurotransmitters in the striatum. Reversal of nigrostriatal pathologies in castrated male mice by subcutaneous implantation of 5α-dihydrotestosterone pellets validates an important role of male sex hormone in castration-induced nigrostriatal pathology. Interestingly, castration was unable to cause glial activation, decrease nigral GDNF, augment the death of nigral dopaminergic neurons, induce the loss of striatal fibers, and impair neurotransmitters in iNOS(-/-) male mice. Furthermore, we demonstrate that iNOS-derived NO is responsible for decreased expression of GDNF in activated astrocytes. Together, our results suggest that castration induces nigrostriatal pathologies via iNOS-mediated decrease in GDNF. These results are important because castrated young male mice may be used as a simple, toxin-free, and nontransgenic animal model to study PD-related nigrostriatal pathologies, paving the way for easy drug screening against PD.

NADPH oxidase and the degeneration of dopaminergic neurons in parkinsonian mice.

Several lines of investigation have implicated oxidative stress in Parkinson's disease (PD) pathogenesis, but the mechanisms involved are still unclear. In this study, we characterized the involvement of NADPH oxidase (Nox), a multisubunit enzyme that catalyzes the reduction of oxygen, in the 6-hydroxydopamine- (6-OHDA-) induced PD mice model and compared for the first time the effects of this neurotoxin in mice lacking gp91(phox-/-), the catalytic subunit of Nox2, and pharmacological inhibition of Nox with apocynin. Six-OHDA induced increased protein expression of p47(phox), a Nox subunit, in striatum. gp91(phox-/-) mice appear to be completely protected from dopaminergic cell loss, whereas the apocynin treatment conferred only a limited neuroprotection. Wt mice treated with apocynin and gp91(phox-/-) mice both exhibited ameliorated apomorphine-induced rotational behavior. The microglial activation observed within the striatum and the substantia nigra pars compacta (SNpc) of 6-OHDA-injected Wt mice was prevented by apocynin treatment and was not detected in gp91(phox-/-) mice. Apocynin was not able to attenuate astrocyte activation in SN. The results support a role for Nox2 in the 6-OHDA-induced degeneration of dopaminergic neurons and glial cell activation in the nigrostriatal pathway and reveal that no comparable 6-OHDA effects were observed between apocynin-treated and gp91(phox-/-) mice groups.