Phosphodiesterase 10A levels are related to striatal function in schizophrenia: a combined positron emission tomography and functional magnetic resonance imaging study.

Pharmacological inhibition of phosphodiesterase 10A (PDE10A) is being investigated as a treatment option in schizophrenia. PDE10A acts postsynaptically on striatal dopamine signaling by regulating neuronal excitability through its inhibition of cyclic adenosine monophosphate (cAMP), and we recently found it to be reduced in schizophrenia compared to controls. Here, this finding of reduced PDE10A in schizophrenia was followed up in the same sample to investigate the effect of reduced striatal PDE10A on the neural and behavioral function of striatal and downstream basal ganglia regions. A positron emission tomography (PET) scan with the PDE10A ligand [11C]Lu AE92686 was performed, followed by a 6 min resting-state magnetic resonance imaging (MRI) scan in ten patients with schizophrenia. To assess the relationship between striatal function and neurophysiological and behavioral functioning, salience processing was assessed using a mismatch negativity paradigm, an auditory event-related electroencephalographic measure, episodic memory was assessed using the Rey auditory verbal learning test (RAVLT) and executive functioning using trail-making test B. Reduced striatal PDE10A was associated with increased amplitude of low-frequency fluctuations (ALFF) within the putamen and substantia nigra, respectively. Higher ALFF in the substantia nigra, in turn, was associated with lower episodic memory performance. The findings are in line with a role for PDE10A in striatal functioning, and suggest that reduced striatal PDE10A may contribute to cognitive symptoms in schizophrenia.

Repeated Administration of 3,4-Methylenedioxymethamphetamine (MDMA) Elevates the Levels of Neuronal Nitric Oxide Synthase in the Nigrostriatal System: Possible Relevance to Neurotoxicity.

Previous studies have consistently demonstrated that the amphetamine-related drug 3,4-methylenedioxymethamphetamine (MDMA) induces dopaminergic damage in the mouse brain, and that this effect is most marked in the nigrostriatal system. Moreover, it has been suggested that the overproduction of nitric oxide (NO) may participate in the dopaminergic damage induced by MDMA. To further elucidate this issue, we evaluated the levels of the enzyme nitric oxide synthase (nNOS), which catalyzes the production of NO, in mice treated with regimens of MDMA that induce progressive and persistent neurotoxicity in the dopaminergic nigrostriatal system. Mice received 14, 28, or 36 administrations of MDMA (10 mg/kg i.p.), twice a day/twice a week, and were sacrificed at different time-points after treatment discontinuation. Thereafter, the number of nNOS-positive neurons was quantified by immunohistochemistry in the caudate-putamen (CPu) and substantia nigra pars compacta (SNc). MDMA elevated the numbers of nNOS-positive neurons in the CPu of mice that received 28 or 36 drug administrations. This effect was still detectable at 3 months after treatment discontinuation. Moreover, MDMA elevated the numbers of nNOS-positive neurons in the SNc. However, this effect occurred only in mice that received 28 drug administrations and were sacrificed 3 days after treatment discontinuation. These results are in line with the hypothesis that activation of the NO cascade participates in the toxic effects induced by MDMA in the dopaminergic nigrostriatal system. Moreover, they suggest that activation of the NO cascade induces toxic effects that are more marked in striatal terminals, compared with nigral neurons.

Effects of acute ethanol exposure on class I HDACs family enzymes in wild-type and BDNF(+/-) mice.

BACKGROUND: Alterations of brain-derived neurotrophic factor (BDNF) have been associated with the development of addiction to different drugs of abuse, including ethanol (EtOH). EtOH exposure activates the BDNF-signaling cascade in dorsal striatum, which in turn affects further EtOH intake. Different alcohol exposures have been widely demonstrated to modulate chromatin remodeling, affecting histone acetylation/deacetylation balance. Recently, class I histone deacetylases (HDACs) inhibition has been reported to modulate BDNF mRNA expression and to attenuate morphological and behavioral phenomena related to EtOH exposure. However, the role played by different HDAC isoforms in EtOH-induced plasticity is still unclear. METHODS: We investigated the effects induced by acute EtOH exposure on the protein levels of class I HDAC 1-3 isoforms of wild-type (WT) and BDNF heterozygous mice (BDNF(+/-)), in nuclear and cytoplasmic extracts of specific brain regions associated with EtOH addiction. RESULTS: Nuclear HDAC 1-3 levels were markedly reduced after acute EtOH treatment in the caudate putamen (CPu) of WT mice only. Furthermore, CPu basal levels of nuclear HDAC isoforms were significantly lower in BDNF(+/-) mice compared to WT. With the exception of nuclear HDAC 3, no significant changes were observed after acute EtOH treatment in the prefrontal cortex (PFCx) of BDNF(+/-) and WT mice. In this area, the nuclear HDAC basal levels were significantly different between the two experimental groups. CONCLUSIONS: These results provide details about EtOH effects on class I HDAC isoforms and strongly support a correlation between BDNF and class I HDACs, suggesting a possible influence of BNDF on these enzymes.

Striatal NOS1 has dimorphic expression and activity under stress and nicotine sensitization.

Nicotine exerts its addictive influence through the meso-cortico-limbic reward system, where the striatum is essential. Nicotine addiction involves different neurotransmitters, nitric oxide (NO) being especially important, since it triggers the release of the others by positive feedback. In the nervous system, NO is mainly produced by nitric oxide synthase 1 (NOS1). However, other subtypes of synthases can also synthesize NO, and little is known about the specific role of each isoform in the process of addiction. In parallel, NOS activity and nicotine addiction are also affected by stress and sexual dimorphism. To determine the specific role of this enzyme, we analyzed both NOS expression and NO synthesis in the striatum of wild-type and NOS1-knocked out (KO) mice of both sexes in situations of nicotine sensitization and stress. Our results demonstrated differences between the caudate-putamen (CP) and nucleus accumbens (NA). With respect to NOS1 expression, the CP is a dimorphic region (27.5% lower cell density in males), but with a stable production of NO, exclusively due to this isoform. Thus, the nitrergic system of CP may not be involved in stress or nicotine addiction. Conversely, the NA is much more variable and strongly involved in both situations: its NO synthesis displays dimorphic variations at both basal (68.5% reduction in females) and stress levels (65.9% reduction in males), which disappear when nicotine is infused. Thus, the KO animals showed an increase in NO production (21.7%) in the NA, probably by NOS3, in an attempt to compensate the lack of NOS1.

Dysregulation of glucose metabolism is an early event in sporadic Parkinson's disease.

Unlike most other cell types, neurons preferentially metabolize glucose via the pentose phosphate pathway (PPP) to maintain their antioxidant status. Inhibiting the PPP in neuronal cell models causes cell death. In rodents, inhibition of this pathway causes selective dopaminergic cell death leading to motor deficits resembling parkinsonism. Using postmortem human brain tissue, we characterized glucose metabolism via the PPP in sporadic Parkinson's disease (PD), Alzheimer's disease (AD), and controls. AD brains showed increased nicotinamide adenine dinucleotide phosphate (NADPH) production in areas affected by disease. In PD however, increased NADPH production was only seen in the affected areas of late-stage cases. Quantifying PPP NADPH-producing enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase by enzyme-linked immunosorbent assay, showed a reduction in the putamen of early-stage PD and interestingly in the cerebellum of early and late-stage PD. Importantly, there was no decrease in enzyme levels in the cortex, putamen, or cerebellum of AD. Our results suggest that down-regulation of PPP enzymes and a failure to increase antioxidant reserve is an early event in the pathogenesis of sporadic PD.

Early down-regulation of PKCδ as a pro-survival mechanism in Huntington's disease.

A balance between cell survival and apoptosis is crucial to avoid neurodegeneration. Here, we analyzed whether the pro-apoptotic protein PKCδ, and the pro-survival PKCα and ßII, were dysregulated in the brain of R6/1 mouse model of Huntington's disease (HD). Protein levels of the three PKCs examined were reduced in all the brain regions analyzed being PKCδ the most affected isoform. Interestingly, PKCδ protein levels were also decreased in the striatum and cortex of R6/2 and Hdh(Q111/Q111) mice, and in the putamen of HD patients. Nuclear PKCδ induces apoptosis, but we detected reduced PKCδ in both cytoplasmic and nuclear enriched fractions from R6/1 mouse striatum, cortex and hippocampus. In addition, we show that phosphorylation and ubiquitination of PKCδ are increased in 30-week-old R6/1 mouse brain. All together these results suggest a pro-survival role of reduced PKCδ levels in response to mutant huntingtin-induced toxicity. In fact, we show that over-expression of PKCδ increases mutant huntingtin-induced cell death in vitro, whereas over-expression of a PKCδ dominant negative form or silencing of endogenous PKCδ partially blocks mutant huntingtin-induced cell death. Finally, we show that the analysis of lamin B protein levels could be a good marker of PKCδ activity, but it is not involved in PKCδ-mediated cell death in mutant huntingtin-expressing cells. In conclusion, our results suggest that neurons increase the degradation of PKCδ as a compensatory pro-survival mechanism in response to mutant huntingtin-induced toxicity that can help to understand why cell death appears late in the disease.

Reduced striatal ecto-nucleotidase activity in schizophrenia patients supports the "adenosine hypothesis".

Schizophrenia (SZ) is a major chronic neuropsychiatric disorder characterized by a hyperdopaminergic state. The hypoadenosinergic hypothesis proposes that reduced extracellular adenosine levels contribute to dopamine D2 receptor hyperactivity. ATP, through the action of ecto-nucleotidases, constitutes a main source of extracellular adenosine. In the present study, we examined the activity of ecto-nucleotidases (NTPDases, ecto-5'-nucleotidase, and alkaline phosphatase) in the postmortem putamen of SZ patients (n = 13) compared with aged-matched controls (n = 10). We firstly demonstrated, by means of artificial postmortem delay experiments, that ecto-nucleotidase activity in human brains was stable up to 24 h, indicating the reliability of this tissue for these enzyme determinations. Remarkably, NTPDase-attributable activity (both ATPase and ADPase) was found to be reduced in SZ patients, while ecto-5'-nucleotidase and alkaline phosphatase activity remained unchanged. In the present study, we also describe the localization of these ecto-enzymes in human putamen control samples, showing differential expression in blood vessels, neurons, and glial cells. In conclusion, reduced striatal NTPDase activity may contribute to the pathophysiology of SZ, and it represents a potential mechanism of adenosine signalling impairment in this illness.

Acute ethanol administration differentially alters enkephalinase and aminopeptidase N activity and mRNA levels in regions of the nigrostriatal pathway.

Opioid peptides play a key role in ethanol reinforcement and may also represent important determinants in brain sensitivity to ethanol through modulation of nigrostriatal dopaminergic activity. Regulation of opioid levels by peptidase-degrading enzymes could be relevant in ethanol's actions. The aim of this work was to study the acute ethanol (2.5 g/kg) effects on the activity and mRNA expression of enkephalinase (NEP) and aminopeptidase N (APN) in the rat substantia nigra (SN) and the anterior-medial (amCP) and medial-posterior (mpCP) regions of the caudate-putamen (CP). Enzymatic activities were measured by fluorometric assays and mRNA expression by reverse transcriptase polymerase chain reaction. Acute ethanol administration differentially altered peptidase activities and mRNA expression with different kinetics. Ethanol increased and decreased NEP mRNA levels in the SN and amCP, respectively, but produced biphasic effects in the mpCP. APN mRNA levels were increased by ethanol in all brain regions. Ethanol induced a transient and long-lasting increase in NEP (mpCP) and APN (amCP) activities, respectively. Peptidase activities were not changed by ethanol in the SN. Our results indicate that striatal NEP and APN are important ethanol targets. Ethanol-induced changes in these neuropeptidases in the CP could contribute to the mechanisms involved in brain sensitivity to ethanol.

Safety and tolerability of magnetic resonance imaging-guided convection-enhanced delivery of AAV2-hAADC with a novel delivery platform in nonhuman primate striatum.

Degeneration of nigrostriatal neurons in Parkinson's disease (PD) causes progressive loss of aromatic l-amino acid decarboxylase (AADC), the enzyme that converts levodopa (l-DOPA) into dopamine in the striatum. Because loss of this enzyme appears to be a major driver of progressive impairment of response to the mainstay drug, l-DOPA, one promising approach has been to use gene therapy to restore AADC activity in the human putamen and thereby restore normal l-DOPA response in patients with PD. An open-label phase I clinical trial of this approach in patients with PD provided encouraging signs of improvement in Unified Parkinson's Disease Rating Scale scores and reductions in antiparkinsonian medications. However, such improvement was modest compared with the results previously reported in parkinsonian rhesus macaques. The reason for this discrepancy may have been that the relatively small volume of vector infused in the clinical study restricted the distribution of AADC expression, such that only about 20% of the postcommissural putamen was covered, as revealed by l-[3-(18)F]-α-methyltyrosine-positron emission tomography. To achieve more quantitative distribution of vector, we have developed a visual guidance system for parenchymal infusion of AAV2. The purpose of the present study was to evaluate the combined magnetic resonance imaging-guided delivery system with AAV2-hAADC under conditions that approximate the intended clinical protocol. Our data indicate that this approach directed accurate cannula placement and effective vector distribution without inducing any untoward effects in nonhuman primates infused with a high dose of AAV2-hAADC.

Lrrk2 localization in the primate basal ganglia and thalamus: a light and electron microscopic analysis in monkeys.

The Leucine Rich Repeat Kinase-2 (LRRK2) gene is a common mutation target in Parkinson's disease (PD), but the cellular mechanisms by which such mutations underlie the pathophysiology of PD remain poorly understood. Thus, to better characterize the neuronal target sites of LRRK2 mutations in the primate brain, we studied the cellular and ultrastructural localization of Lrrk2 immunoreactivity in the monkey basal ganglia. As previously described, the monkey striatum was the most enriched basal ganglia structure in Lrrk2 labeling. Both projection neurons and parvalbumin-containing GABAergic interneurons displayed Lrrk2 immunoreactivity. At the electron microscopic level, striatal Lrrk2 labeling was associated predominantly with dendritic shafts and subsets of putative glutamatergic axon terminals. At the pallidal level, moderate cellular Lrrk2 immunostaining was found in the external globus pallidus (GPe), while neurons in the internal globus pallidus (GPi) were devoid of Lrrk2 immunoreactivity. Strong labeling was associated with cholinergic neurons in the nucleus basalis of Meynert. Midbrain dopaminergic neurons in the primate substantia nigra pars compacta (SNc) and ventral tegmental area harbored a significant level of Lrrk2 labeling, while neurons in the subthalamic nucleus were lightly immunostained. Most thalamic nuclei were enriched in Lrrk2 immunoreactivity, except for the centromedian nucleus that was completely devoid of labeling. Thus, Lrrk2 protein is widely distributed in the monkey basal ganglia, suggesting that gene mutations in PD may result in multifarious pathophysiological effects that could impact various target sites in the functional circuitry of the primate basal ganglia.

Increased xanthine oxidase in the thalamus and putamen in depression.

A growing body of literature suggests persistent and selective structural changes in the cortico-limbic-thalamic-striatal system in patients with recurrent depressive disorder (DD). Oxidative stress is thought to play a key role in these processes. So far, the main scientific focus has been on antioxidant enzymes in this context. For the first time, this proof of concept study examines the activity of the free radicals producing the enzyme, xanthine oxidase (XO), directly in the cortico-limbic-thalamic-striatal system of patients with recurrent depression. The activity of XO was ascertained in the cortico-limbic-thalamic-striatal regions in post-mortem brain tissue of patients with recurrent depressive episodes and individuals without any neurological or psychiatric history (7/7). We measured the XO activity in following brain areas: hippocampus, regio entorhinalis, thalamus, putamen and caudate nucleus. In this study, we report a significant increase of XO activity in the thalamus and the putamen of patients with depression. Our findings contribute to the growing body of evidence suggesting that oxidative stress plays a pivotal role in certain brain areas in recurrent depressive disorder.

Cocaine-induced hyperactivity and sensitization are dependent on GSK3.

Glycogen synthase kinase 3 (GSK3) is a critical mediator of many intracellular signaling systems. The activity of GSK3 is regulated by several kinases, with inactivation occurring via phosphorylation of the inhibitory serine-21 (alpha-isoform) and serine-9 (beta-isoform) residues. Here, we investigated whether acute cocaine administration regulates GSK3 activity and if inhibition of GSK3 by valproate or the selective GSK3 inhibitor SB 216763 would attenuate cocaine-induced behaviors in mice. Mice injected with cocaine (20 mg/kg, i.p.) showed a reduction in the phosphorylation of GSK3beta in the caudate putamen, reflecting an increase in the activity of the kinase. To assess the role of GSK3 in cocaine-induced hyperactivity, mice were pretreated with valproate (50-300 mg/kg, i.p.), SB 216763 (0.25-7.5 mg/kg, i.p.), or the appropriate vehicle prior to saline or cocaine (20 mg/kg, i.p.). Valproate or SB 216763 produced significant dose-dependent reductions in cocaine-induced ambulatory and stereotypic activity. Repeated administration of cocaine can result in an augmentation of the locomotor-stimulatory effects of the drug, a phenomenon referred to as sensitization. Mice pretreated with SB 216763 (2.5 mg/kg, i.p.) prior to daily cocaine (20 mg/kg, i.p.) for 5 days showed a significant attenuation of the development of cocaine-induced behavioral sensitization following a cocaine challenge on day 13. These results indicate that cocaine activated GSK3beta in the caudate putamen and that pharmacological inhibition of GSK3 reduced both the acute behavioral responses to cocaine and the long-term neuroadaptations produced by repeated cocaine, therefore suggesting a role for GSK3 in the behavioral and neurochemical manifestations associated with cocaine exposure.

Cue-elicited drug craving represses ERK activation in mice prefrontal association cortex.

Morphine addiction is characterized by compulsive drug-taking behavior and high rates of relapse that reflect reward-controlled learning, consolidation and reconsolidation of drug cues. Extracellular signal-regulated protein kinase (ERK) is one of the cellular molecules that have been highly implicated in the synaptic plasticity processes of learning and memory in cocaine addiction. However, the roles of ERK in the morphine-paired conditioned place preference (CPP) are not clear. In the present study, we found that compared to the morphine-unpaired and saline-paired and saline-unpaired groups, morphine-paired mice showed depressed ERK2 activity in the Frontal Association Cortex (FrA), whereas ERK1 activity was not changed in the same region. In the Accumbens Nucleus (Acb) and Caudate Putamen (CPu) that are associated with cocaine addiction, the activities of ERK1 and ERK2 among four groups showed no difference. These results suggest that the FrA plays an important role in morphine craving and that ERK2 is involved in eliciting the environment-related morphine craving, which is totally different from those induced by morphine itself.

Localization of Parkinson's disease-associated LRRK2 in normal and pathological human brain.

Mutations in the LRRK2 gene cause autosomal dominant, late-onset parkinsonism, which presents with pleomorphic pathology including alpha-synucleopathy. To promote our understanding of the biological role of LRRK2 in the brain we examined the distribution of LRRK2 mRNA and protein in postmortem human brain tissue from normal and neuropathological subjects. In situ hybridization and immunohistochemical analysis demonstrate the expression and localization of LRRK2 to various neuronal populations in brain regions implicated in Parkinson's disease (PD) including the cerebral cortex, caudate-putamen and substantia nigra pars compacta. Immunofluorescent double labeling studies additionally reveal the prominent localization of LRRK2 to cholinergic-, calretinin- and GABA(B) receptor 1-positive, dopamine-innervated, neuronal subtypes in the caudate-putamen. The distribution of LRRK2 in brain tissue from sporadic PD and dementia with Lewy bodies (DLB) subjects was also examined. In PD brains, LRRK2 immunoreactivity localized to nigral neuronal processes is dramatically reduced which reflects the disease-associated loss of dopaminergic neurons in this region. However, surviving nigral neurons occasionally exhibit LRRK2 immunostaining of the halo structure of Lewy bodies. Moreover, LRRK2 immunoreactivity is not associated with Lewy neurites or with cortical Lewy bodies in sporadic PD and DLB brains. These observations indicate that LRRK2 is not a primary component of Lewy bodies and does not co-localize with mature fibrillar alpha-synuclein to a significant extent. The localization of LRRK2 to key neuronal populations throughout the nigrostriatal dopaminergic pathway is consistent with the involvement of LRRK2 in the molecular pathogenesis of familial and sporadic parkinsonism.

Quetiapine reverses altered locomotor activity and tyrosine hydroxylase immunoreactivity in rat caudate putamen following long-term haloperidol treatment.

Haloperidol (HAL) is a typical antipsychotic drug and known to cause extrapyramidal symptoms (EPS) that may be associated with the blockade of dopamine D2-receptors in nigrostriatal pathway by the drug. In contrast, quetiapine (QTP) is an atypical antipsychotic drug that has the lowest incidence of producing EPS in patients with schizophrenia, while improving psychosis symptoms. In the present study, we investigated the possibility of reversing the HAL-induced changes in locomotor activity and in striatal tyrosine hydroxylase (TH) of rats. Rats were administered HAL (2mg/kg/day, p.o.) for 3 months, followed by vehicle (VEH), QTP (10mg/kg/day), HAL, or HAL+QTP for another 5 weeks. The locomotor activity and TH immunoreactivity of the rats were measured. Chronic administration of HAL caused significant increase in locomotor activity and lower levels of TH immunoreactivity in the caudate putamen of the striatum. When the long-term haloperidol treatment was removed, the change in TH immunoreactivity was normalized, while the HAL induced high level of locomotor activity was returned to normal level only in the rats that stopped HAL consumption and received QTP treatment. In the substantia nigra and ventral tegmental areas, all rats showed comparable numbers of TH-positive cell bodies, which had no shrinkage. These results support a previously proposed relationship between EPS and TH levels in the striatum and provide valuable preclinical information towards understanding why QTP produces a lowest incidence of EPS among antipsychotics and has been used to treat EPS caused by other antipsychotics, and eventually establish a principle of treating EPS.

Single or multiple injections of methamphetamine increased dopamine turnover but did not decrease tyrosine hydroxylase levels or cleave caspase-3 in caudate-putamen.

Methamphetamine (METH), leading to striatal dopamine (DA) nerve terminal toxicity in mammals, is also thought to induce apoptosis of striatal neurons in rodents. We investigated the acute effects induced by multiple injections of METH (4 x 5 mg/kg, i.p.) at 2-h intervals or a single injection of METH (20 mg/kg, i.p.) on terminal dopaminergic toxicity markers, including DA levels, DA turnover, and tyrosine hydroxylase (TH) immunoreactivity in rat caudate-putamen (CPu). We further investigated whether both treatment paradigms would change Bax and activate caspase-3 expression, thus triggering striatal apoptotic mitochondria-dependent biochemical cascades. The first injection of METH (5 mg/kg, i.p.) produced a significant release of DA that peaked 30 min and stayed above control levels up to 1.5 h within CPu. In another set of experiments, rats were killed 1 and 24 h following the last injection, for tissue DA and metabolite content measurement and Western blot analysis (24 h). Multiple doses induced DA depletion and increased turnover at both endpoints. Single-dose METH reproduced these effects at 24 h; however, turnover was significantly higher than that evoked by the multiple doses at 24 h. Although both paradigms evoked similar DA depletion, however, none of the dosing regimens induced changes in TH expression at 24 h. The former paradigm produced an increase in Bax expression in CPu not sufficient to induce cleavage of caspase-3 proenzyme at 24 h. This study suggests that both paradigm induced changes in striatal dopaminergic markers that are independent of terminal degeneration and striatal apoptotic mitochondria-dependent caspase-3 driven cascade within 24 h.

Convection-enhanced delivery of adeno-associated virus type 2 (AAV2) into the striatum and transport of AAV2 within monkey brain.

Adeno-associated virus type 2 (AAV2)-based vectors are promising transgene carriers for experimental gene therapy treatments of brain diseases. However, detailed evaluation of transgene distribution, trafficking, and transport within the brain is of the utmost importance before applying any type of gene therapy in humans. We examined the distribution of AAV2-thymidine kinase (AAV2-TK) and AAV2-aromatic L-amino acid decarboxylase (AAV2-AADC) in monkey brain after convection-enhanced delivery (CED). The AADC group consisted of two 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys that received unilateral infusions of AAV2-AADC into six sites in the right hemisphere. The TK group consisted of three monkeys that received bilateral CED infusion of AAV2-TK into the putamen; one side in all three monkeys was coinfused with heparin. Six weeks after AAV delivery, the brains were collected and processed for immunohistochemical staining. Volumetric measurement of TK distribution showed that at least 75% of the putamen could be covered by a single infusion of the vector; however, no effects of heparin coadministration were found, most likely because of the already robust gene transfer achieved by CED. Interestingly, TK- and AADCimmunoreactive cells were also present outside the striatum, in the globus pallidus, subthalamic nucleus, thalamus, and substantia nigra. CED proved to be an efficient method for delivery of the AAV2 vector. Detection of the transgenes in brain structures distant from the site of injection emphasizes the potential for gene transport, and the advantages and disadvantages of CED for gene therapy deserve further study.

Inhibition of brain angiotensin-converting enzyme by peripheral administration of trandolapril versus lisinopril in Wistar rats.

BACKGROUND: Peripheral administration of blockers of the renin-angiotensin system (RAS) may affect the RAS in the brain to a variable degree. In the present study, we determined inhibition of angiotensin-converting enzyme (ACE) in the brain after peripheral administration of a lipophilic (trandolapril) versus hydrophilic (lisinopril) ACE inhibitor. METHODS: Trandolapril (0.2, 1, and 5 mg/kg/day, subcutaneously) was compared with lisinopril (2, 10, and 50 mg/kg/day, subcutaneously), each for 6 days. At 4 and 24 h after the last dose, (125)I-351A binding on brain ACE was measured. RESULTS: Trandolapril and lisinopril caused similar inhibition of ligand binding outside the blood-brain barrier (BBB). However, inside the BBB, trandolapril was more effective at low and medium doses (for lisinopril, 28% to 51% inhibition at a dose of 2 mg, 63% to 72% at 10 mg, and 84% to 86% at 50 mg; and for trandolapril, 62% to 68% inhibition at a dose of 0.2 mg, 84% to 87% at 1 mg, and 88% to 93% at 5 mg). In contrast, in the brain structures caudate putamen and globus pallidus, lisinopril inhibited ligand binding better than trandolapril (for lisinopril 30% to 44% at a dose of 2 mg and 71% to 74% at 10 mg, versus for trandolapril 21% to 27% at 0.2 mg and 51% to 63% at 1 mg). At 24 h after the last dose, inhibition by trandolapril persisted more than inhibition by lisinopril both outside and inside the BBB. CONCLUSIONS: These results suggest that peripheral administration of even hydrophilic ACE inhibitors can result in marked inhibition of brain ACE inside the BBB but that different brain structures show variable inhibition.

Mice deficient in dihydrolipoamide dehydrogenase show increased vulnerability to MPTP, malonate and 3-nitropropionic acid neurotoxicity.

Altered energy metabolism, including reductions in activities of the key mitochondrial enzymes alpha-ketoglutarate dehydrogenase complex (KGDHC) and pyruvate dehydrogenase complex (PDHC), are characteristic of many neurodegenerative disorders including Alzheimer's Disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). Dihydrolipoamide dehydrogenase is a critical subunit of KGDHC and PDHC. We tested whether mice that are deficient in dihydrolipoamide dehydrogenase (Dld+/-) show increased vulnerability to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), malonate and 3-nitropropionic acid (3-NP), which have been proposed for use in models of PD and HD. Administration of MPTP resulted in significantly greater depletion of tyrosine hydroxylase-positive neurons in the substantia nigra of Dld+/- mice than that seen in wild-type littermate controls. Striatal lesion volumes produced by malonate and 3-NP were significantly increased in Dld+/- mice. Studies of isolated brain mitochondria treated with 3-NP showed that both succinate-supported respiration and membrane potential were suppressed to a greater extent in Dld+/- mice. KGDHC activity was also found to be reduced in putamen from patients with HD. These findings provide further evidence that mitochondrial defects may contribute to the pathogenesis of neurodegenerative diseases.

Decreased striatal dopamine D1 receptor-stimulated adenylyl cyclase activity in human methamphetamine users.

OBJECTIVE: It has been assumed that some behavioral changes associated with repeated exposure to dopaminergic psychostimulant drugs might be explained by changes in activity of dopamine receptors, including the dopamine D(1) receptor, which is linked by a stimulatory G protein to the effector enzyme adenylyl cyclase. To establish whether dopamine D(1) receptor function might be altered in human methamphetamine users, the authors measured dopamine-stimulated adenylyl cyclase activity in the brain of chronic human users of the drug. METHOD: Adenylyl cyclase activity stimulated by dopamine and by guanylyl-imidodiphosphate (to assess G protein and adenylyl cyclase coupling) was determined in the postmortem brain tissue of 16 methamphetamine users who had used the drug both recently and chronically (i.e., at least 1 year) as well as 21 matched comparison subjects. RESULTS: A 25%-30% decrease in the maximal extent of dopamine stimulation of adenylyl cyclase activity was seen in the striatum (nucleus accumbens, caudate, and putamen) of the methamphetamine users. No changes were found in basal or guanylyl-imidodiphosphate-stimulated enzyme activity. CONCLUSIONS: These data suggest that dopamine receptor function linked to adenylyl cyclase is partially desensitized in the striatum of human methamphetamine users. Decreased dopamine D(1) receptor function might underlie part of the known (drug withdrawal syndrome) or expected (drug tolerance) consequences of methamphetamine exposure in humans.