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Biomedical subjects

Raul R Gainetdinov

Publications and source records attributed to Raul R Gainetdinov.

At least 19 recordsLinked to original sources
PubMed2026

Comparative Proteomic Analysis of the Striatum in Heterozygous and Null DAT Knockout Rats.

Deregulation of striatal neurotransmission is a key pathogenetic mechanism in neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) and autism. In the present study, we applied a proteomic approach to demonstrate shifts in striatal protein expression in rats with heterozygous (DAT-Het) and homozygous (DAT-KO) dopamine transporter (DAT) gene knockouts. These animals model dose-dependent ADHD- and autism-like behaviors, ranging from slightly increased activity and social disturbances in DAT-Het rats to a pronounced phenotype in DAT-KO rats. We revealed pronounced changes in the proteomic profiles of both groups, associated primarily with deregulation of proteins involved in energy and carbon metabolism. Furthermore, we identified changes in vesicular transport proteins specific to DAT-KO and DAT-Het rats. Since these changes involved SNARE complex components, we evaluated SNARE mRNA expression in our models and public transcriptomic data for mouse models of neurodevelopmental disorders, including Mbd5 gene haploinsufficiency and a polygenic model of ADHD. No significant changes in mRNA levels were revealed in any model. Thus, the identified protein expression changes likely depend on post-transcriptional mechanisms. These data suggest a deregulation of metabolism in DAT-Het rats, which becomes more pronounced in DAT-KO rats.

Animals↗
PubMed2006

Dopamine enhances motor and neuropathological consequences of polyglutamine expanded huntingtin.

An expansion in the CAG repeat of the IT15 (huntingtin) gene underlies the development of Huntington's disease (HD), but the basis for the specific vulnerability of dopamine-receptive striatal neurons remains unclear. To examine the potential role of the dopamine system in the emergence of pathological conditions in HD, we generated a double mutant mouse strain with both enhanced dopamine transmission and endogenous expression of a mutant huntingtin gene. This strain was generated by crossing the dopamine transporter knock-out mouse, which exhibits a 5-fold elevation in extracellular dopamine levels in the striatum and locomotor hyperactivity, to a knock-in mouse model of HD containing 92 CAG repeats. These double mutant mice exhibited an increased stereotypic activity at 6 months of age, followed by a progressive decline of their locomotor hyperactivity. Expression of the mutated huntingtin did not alter dopamine or its metabolite levels in normal or dopamine transporter knock-out mice. However, the mutant huntingtin protein aggregated much earlier and to a greater extent in the striatum and other dopaminergic brain regions in the hyperdopaminergic mouse model of HD. Furthermore, the formation of neuropil aggregates in the striatum and other regions of hyperdopaminergic HD mice was observed at 4 months of age, well before similar events occurred in normal HD mice (12 months). These findings indicate that dopamine contributes to the deleterious effects of mutated huntingtin on striatal function, and this is accompanied by enhanced formation of huntingtin aggregates.

Aging↗
PubMed2006

Rapid alterations in corticostriatal ensemble coordination during acute dopamine-dependent motor dysfunction.

Dopaminergic dysregulation can cause motor dysfunction, but the mechanisms underlying dopamine-related motor disorders remain under debate. We used an inducible and reversible pharmacogenetic approach in dopamine transporter knockout mice to investigate the simultaneous activity of neuronal ensembles in the dorsolateral striatum and primary motor cortex during hyperdopaminergia ( approximately 500% of controls) with hyperkinesia, and after rapid and profound dopamine depletion (<0.2%) with akinesia in the same animal. Surprisingly, although most cortical and striatal neurons ( approximately 70%) changed firing rate during the transition between dopamine-related hyperkinesia and akinesia, the overall cortical firing rate remained unchanged. Conversely, neuronal oscillations and ensemble activity coordination within and between cortex and striatum did change rapidly between these periods. During hyperkinesia, corticostriatal activity became largely asynchronous, while during dopamine-depletion the synchronicity increased. Thus, dopamine-related disorders like Parkinson's disease may not stem from changes in the overall levels of cortical activity, but from dysfunctional activity coordination in corticostriatal circuits.

Action Potentials↗
PubMed2006

Dopaminergic control of sleep-wake states.

Dopamine depletion is involved in the pathophysiology of Parkinson's disease, whereas hyperdopaminergia may play a fundamental role in generating endophenotypes associated with schizophrenia. Sleep disturbances are known to occur in both schizophrenia and Parkinson's disease, suggesting that dopamine plays a role in regulating the sleep-wake cycle. Here, we show that novelty-exposed hyperdopaminergic mice enter a novel awake state characterized by spectral patterns of hippocampal local field potentials that resemble electrophysiological activity observed during rapid-eye-movement (REM) sleep. Treatment with haloperidol, a D2 dopamine receptor antagonist, reduces this abnormal intrusion of REM-like activity during wakefulness. Conversely, mice acutely depleted of dopamine enter a different novel awake state characterized by spectral patterns of hippocampal local field potentials that resemble electrophysiological activity observed during slow-wave sleep (SWS). This dopamine-depleted state is marked by an apparent suppression of SWS and a complete suppression of REM sleep. Treatment with D2 (but not D1) dopamine receptor agonists recovers REM sleep in these mice. Altogether, these results indicate that dopamine regulates the generation of sleep-wake states. We propose that psychosis and the sleep disturbances experienced by Parkinsonian patients result from dopamine-mediated disturbances of REM sleep.

Animals↗
PubMed2006

DDD mice, a novel acute mouse model of Parkinson's disease.

We describe the development of a novel animal model of acute severe dopamine (DA) deficiency by using genetically altered mice lacking the DA transporter (DAT-KO mice). In the absence of a DAT-mediated recycling mechanism in these mice, striatal DA concentrations become entirely dependent on its de novo synthesis, and acute pharmacologic inhibition of tyrosine hydroxylase induces transient (up to 16 hours) elimination of brain DA. Dopamine-deficient DAT-KO mice (DDD mice) demonstrate a striking behavioral phenotype manifested as severe akinesia, rigidity, tremor, and ptosis. We propose that DDD mice represent a novel acute model of severe DA deficiency that might be used to identify compounds with potential therapeutic use for the treatment of Parkinson's disease (PD). This model is particularly promising as a tool for evaluating the efficacy of compounds that may induce movement independently of DA. The advantages and limitations of DDD mice in comparison to other rodent PD models are discussed.

Animals↗
PubMed2006

Mice deficient for the vesicular acetylcholine transporter are myasthenic and have deficits in object and social recognition.

An important step for cholinergic transmission involves the vesicular storage of acetylcholine (ACh), a process mediated by the vesicular acetylcholine transporter (VAChT). In order to understand the physiological roles of the VAChT, we developed a genetically altered strain of mice with reduced expression of this transporter. Heterozygous and homozygous VAChT knockdown mice have a 45% and 65% decrease in VAChT protein expression, respectively. VAChT deficiency alters synaptic vesicle filling and affects ACh release. Whereas VAChT homozygous mutant mice demonstrate major neuromuscular deficits, VAChT heterozygous mice appear normal in that respect and could be used for analysis of central cholinergic function. Behavioral analyses revealed that aversive learning and memory are not altered in mutant mice; however, performance in cognitive tasks involving object and social recognition is severely impaired. These observations suggest a critical role of VAChT in the regulation of ACh release and physiological functions in the peripheral and central nervous system.

Acetylcholine↗
PubMed2006

Paradoxical striatal cellular signaling responses to psychostimulants in hyperactive mice.

Recent investigations have shown that three major striatal-signaling pathways (protein kinase A/DARPP-32, Akt/glycogen synthase kinase 3, and ERK) are involved in the regulation of locomotor activity by the monoaminergic neurotransmitter dopamine. Here we used dopamine transporter knock-out mice to examine which particular changes in the regulation of these cell signaling mechanisms are associated with distinct behavioral responses to psychostimulants. In normal animals, amphetamine and methylphenidate increase extracellular levels of dopamine, leading to an enhancement of locomotor activity. However, in dopamine transporter knock-out mice that display a hyperactivity phenotype resulting from a persistent hyperdopaminergic state, these drugs antagonize hyperactivity. Under basal conditions, dopamine transporter knock-out mice show enhanced striatal DARPP-32 phosphorylation, activation of ERK, and inactivation of Akt as compared with wild-type littermates. However, administration of amphetamine or methylphenidate to these mice reveals that inhibition of ERK signaling is a common determinant for the ability of these drugs to antagonize hyperactivity. In contrast, psychostimulants activate ERK and induce hyperactivity in normal animals. In hyperactive mice psychostimulant-mediated behavioral inhibition and ERK regulation are also mimicked by the serotonergic drugs fluoxetine and 5-carboxamidotryptamine, thereby revealing the involvement of serotonin-dependent inhibition of striatal ERK signaling. Furthermore, direct inhibition of the ERK signaling cascade in vivo using the MEK inhibitor SL327 recapitulates the actions of psychostimulants in hyperactive mice and prevents the locomotor-enhancing effects of amphetamine in normal animals. These data suggest that the inhibitory action of psychostimulants on dopamine-dependent hyperactivity results from altered regulation of striatal ERK signaling. In addition, these results illustrate how altered homeostatic state of neurotransmission can influence in vivo signaling responses and biological actions of pharmacological agents used to manage psychiatric conditions such as Attention Deficit Hyperactivity Disorder (ADHD).

Amphetamine↗
PubMed2006

Social context-dependent singing-regulated dopamine.

Like the mammalian striatum, the songbird striatum receives dense dopaminergic input from the midbrain ventral tegmental area-substantia nigra pars compacta complex. The songbird striatum also contains a unique vocal nucleus, Area X, which has been implicated in song learning and social context-dependent song production. Area X shows increased neural firing and activity-dependent gene expression when birds sing, and the level of activation is higher and more variable during undirected singing relative to directed singing to other birds. Here we show in the first report of in vivo microdialysis in awake, behaving songbirds that singing is associated with increased dopamine levels in Area X. Dopamine levels are significantly higher with directed relative to undirected singing. This social context-dependent difference in dopamine levels requires the dopamine transporter, because local in vivo blockade of the transporter caused dopamine levels for undirected singing to increase to levels similar to that for directed singing, eliminating the social context-dependent difference. The increase in dopamine is presumably depolarization and vesicular release dependent, because adding of high K+ increased and removal of Ca2+ increased and decreased extracellular DA levels. Our findings implicate DA and molecules that control DA kinetics in singing behavior and social context-dependent brain function.

Animal Communication↗
PubMed2006

Local knockdown of genes in the brain using small interfering RNA: a phenotypic comparison with knockout animals.

BACKGROUND: Recent reports have suggested effectiveness of RNA interference (RNAi) for the analysis of gene functions in the brain. This study sought to determine the efficiency of local small interfering RNA (siRNA) injections, comparing this approach with animals generated through classical gene targeting. METHODS: Small interfering RNA against dopamine transporter (DAT) (35 microg/14 days) or tyrosine hydroxylase (TH) (15 microg/3 days) was injected into the ventral tegmental/substantia nigra areas of the brain of adult wildtype or DAT-knockout mice, respectively. RESULTS: Local injections of siRNA resulted in a 35% to 40% reduction of DAT and TH protein levels in the striatum, respectively. Despite negligible effect of DAT knockdown on novelty-induced locomotion, the locomotor response of DAT siRNA treated animals to amphetamine was blunted similar to what is observed in the DAT heterozygote animals. Since incomplete reduction of TH levels in normal mice does not produce behavioral effects, TH siRNA experiments were carried out in DAT-knockout animals that show increased dependence on newly synthesized dopamine. Knockdown of TH in these animals resulted in reduced basal locomotion. CONCLUSIONS: Local injection of siRNA in the brain reduced gene expression by 40% to 50%, suggesting that siRNA-mediated knockdown of genes in the brain can be a complementary tool to classical transgenesis for the analysis of gene functions.

Animals↗
PubMed2006

Molecular biology, pharmacology and functional role of the plasma membrane dopamine transporter.

The plasma membrane dopamine transporter (DAT) tightly regulates the extracellular concentrations of dopamine (DA) by re-capturing released neurotransmitter back into the presynaptic neuronal terminals and/or neighboring DA projections thereby providing an effective way to regulate synaptic and extrasynaptic DA levels. This transporter is a primary target of many potent psychotropic drugs and neurotoxins, such as cocaine, amphetamines and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this review we summarize recent advances in understanding the structure, regulation, and functional roles of DAT in normal DA physiology and pathological conditions, such as attention deficit hyperactivity disorder (ADHD) and neurodegenerative processes, as well as their contribution to the pharmacology of psychostimulant drugs. Significant new insights on these issues have been gained using mice with genetic deletion of DAT.

Animals↗
PubMed2005

Dopamine-independent locomotor actions of amphetamines in a novel acute mouse model of Parkinson disease.

Brain dopamine is critically involved in movement control, and its deficiency is the primary cause of motor symptoms in Parkinson disease. Here we report development of an animal model of acute severe dopamine deficiency by using mice lacking the dopamine transporter. In the absence of transporter-mediated recycling mechanisms, dopamine levels become entirely dependent on de novo synthesis. Acute pharmacological inhibition of dopamine synthesis in these mice induces transient elimination of striatal dopamine accompanied by the development of a striking behavioral phenotype manifested as severe akinesia, rigidity, tremor, and ptosis. This phenotype can be reversed by administration of the dopamine precursor, L-DOPA, or by nonselective dopamine agonists. Surprisingly, several amphetamine derivatives were also effective in reversing these behavioral abnormalities in a dopamine-independent manner. Identification of dopamine transporter- and dopamine-independent locomotor actions of amphetamines suggests a novel paradigm in the search for prospective anti-Parkinsonian drugs.

Amphetamines↗
PubMed2005

An Akt/beta-arrestin 2/PP2A signaling complex mediates dopaminergic neurotransmission and behavior.

Dopamine plays an important role in the etiology of schizophrenia, and D2 class dopamine receptors are the best-established target of antipsychotic drugs. Here we show that D2 class-receptor-mediated Akt regulation involves the formation of signaling complexes containing beta-arrestin 2, PP2A, and Akt. beta-arrestin 2 deficiency in mice results in reduction of dopamine-dependent behaviors, loss of Akt regulation by dopamine in the striatum, and disruption of the dopamine-dependent interaction of Akt with its negative regulator, protein phosphatase 2A. Importantly, canonical cAMP-mediated dopamine-receptor signaling is not inhibited in the absence of beta-arrestin 2. These results demonstrate that, apart from its classical function in receptor desensitization, beta-arrestin 2 also acts as a signaling intermediate through a kinase/phosphatase scaffold. Furthermore, this function of beta-arrestin 2 is important for the expression of dopamine-associated behaviors, thus implicating beta-arrestin 2 as a positive mediator of dopaminergic synaptic transmission and a potential pharmacological target for dopamine-related psychiatric disorders.

Animals↗
PubMed2005

Characterization of conditioned place preference to cocaine in congenic dopamine transporter knockout female mice.

RATIONALE: The dopamine transporter (DAT) is thought to play a major role in the rewarding effects of cocaine. Therefore, it is surprising that cocaine reveals conditioned effects in DAT knockout (DAT-KO) mice. OBJECTIVES: To examine these findings further, we obtained complete dose-effect curves for DAT-KO and DAT wild-type (DAT-WT) mice in a cocaine conditioned place preference (CPP) procedure. METHODS: Congenic C57BL6 background female DAT-KO and DAT-WT mice were conditioned in a three-compartment place preference apparatus. Conditioning consisted of three 30-min sessions with cocaine (2.5, 5.0, 10.0, 20.0, or 40.0 mg/kg) and three 30-min sessions with saline. The distribution of time in each choice compartment was determined after each pair of conditioning sessions (one cocaine and one saline session). RESULTS: DAT-WT mice revealed CPP over a wide range of cocaine doses (5.0-40 mg/kg), whereas DAT-KO mice revealed CPP over a more restricted range of doses, with consistent CPP only occurring with 10 mg/kg of cocaine. CONCLUSIONS: CPP for cocaine develops in both DAT-KO and DAT-WT mice; however, the dose range at which CPP develops is much more restricted in DAT-KO mice than in DAT-WT mice. These observations corroborate the significant role of DAT inhibition in cocaine's conditioned effects.

Animals↗
PubMed2005

G protein-coupled receptor kinase regulates dopamine D3 receptor signaling by modulating the stability of a receptor-filamin-beta-arrestin complex. A case of autoreceptor regulation.

In addition to its postsynaptic role, the dopamine D3 receptor (D3R) serves as a presynaptic autoreceptor, where it provides continuous feedback regulation of dopamine release at nerve terminals for processes as diverse as emotional tone and locomotion. D3R signaling ability is supported by an association with filamin (actin-binding protein 280), which localizes the receptor with G proteins in plasma membrane lipid rafts but is not appreciably antagonized in a classical sense by the ligand-mediated activation of G protein-coupled receptor kinases (GRKs) and beta-arrestins. In this study, we investigate GRK-mediated regulation of D3R.filamin complex stability and its effect on D3R.G protein signaling potential. Studies in HEK-293 cells show that in the absence of agonist the D3R immunoprecipitates in a complex containing both filamin A and beta-arrestin2. Moreover, the filamin directly interacts with beta-arrestin2 as assessed by immunoprecipitation and yeast two-hybrid studies. With reductions in basal GRK2/3 activity, an increase in the basal association of filamin A and beta-arrestin2 with D3R is observed. Conversely, increases in the basal GRK2/3 activity result in a reduction in the interaction between the D3R and filamin but a relative increase in the agonist-mediated interaction between beta-arrestin2 and the D3R. Our data suggest that the D3R, filamin A, and beta-arrestin form a signaling complex that is destabilized by agonist- or expression-mediated increases in GRK2/3 activity. These findings provide a novel GRK-based mechanism for regulating D3R signaling potential and provide insight for interpreting D3R autoreceptor behavior.

Animals↗
PubMed2005

Loss-of-function mutation in tryptophan hydroxylase-2 identified in unipolar major depression.

Dysregulation of central serotonin neurotransmission has been widely suspected as an important contributor to major depression. Here, we identify a (G1463A) single nucleotide polymorphism (SNP) in the rate-limiting enzyme of neuronal serotonin synthesis, human tryptophan hydroxylase-2 (hTPH2). The functional SNP in hTPH2 replaces the highly conserved Arg441 with His, which results in approximately 80% loss of function in serotonin production when hTPH2 is expressed in PC12 cells. Strikingly, SNP analysis in a cohort of 87 patients with unipolar major depression revealed that nine patients carried the mutant (1463A) allele, while among 219 controls, three subjects carried this mutation. In addition, this functional SNP was not found in a cohort of 60 bipolar disorder patients. Identification of a loss-of-function mutation in hTPH2 suggests that defect in brain serotonin synthesis may represent an important risk factor for unipolar major depression.

Adult↗
PubMed2004

Tryptophan hydroxylase-2 controls brain serotonin synthesis.

Dysregulation of brain serotonin contributes to many psychiatric disorders. Tryptophan hydroxylase-2 (Tph2), rather than Tph1, is preferentially expressed in the brain. We report a functional (C1473G) single-nucleotide polymorphism in mouse Tph2 that results in the substitution of Pro447 with Arg447 and leads to decreased serotonin levels in PC12 cells. Moreover, in BALB/cJ and DBA/2 mice that are homozygous for the 1473G allele, brain serotonin tissue content and synthesis are reduced in comparison to C57Bl/6 and 129X1/SvJ mice that are homozygous for the 1473C allele. Our data provide direct evidence for a fundamental role of Tph2 in brain serotonin synthesis.

Alleles↗
PubMed2004

Dissociation of rewarding and dopamine transporter-mediated properties of amphetamine.

The interaction of amphetamine (AMPH) with the dopamine (DA) transporter (DAT) is thought to be critically important for the DA-elevating actions of this drug. It is commonly believed that DA elevations are involved in the rewarding/reinforcing properties of AMPH and other drugs of abuse. Here, we found that DAT deletion did not eliminate the rewarding effects of AMPH as measured by conditioned place preference (CPP). In fact, mice in which the DAT gene has been deleted (DAT-KO mice) exhibited AMPH-induced CPP for many weeks after the time when extinction occurred in WT mice. Moreover, systemic AMPH still increased extracellular DA in the nucleus accumbens (NAc) of mice lacking the DAT, although local infusion of AMPH into the NAc did not have this effect. By using voltammetry in NAc slices, we found that AMPH did not decrease the rate of DA clearance. The rate of ventral tegmental area DA neuron firing was dramatically inhibited by AMPH in brain slices from WT mice, but there was no inhibition of firing in DAT-KO mice. AMPH-induced CPP was abolished by pretreatment with WAY-100635, a serotonin 5-HT(1A) receptor antagonist, in DAT-KO mice, but the drug did not change AMPH place preference in WT mice. Therefore, despite the absence of the DAT, AMPH displays rewarding effects and causes an increase in extracellular DA in the NAc of DAT-KO mice, acting indirectly in this case. The 5-HT system may be involved in the rewarding effects of AMPH in these mice.

Amphetamine↗