Abnormal dopamine uptake sites in postmortem striatum from patients with Tourette's syndrome

Olanzapine, quetiapine, and risperidone: long-term effects on monoamine transporters in rat forebrain

Long-term effects of novel atypical antipsychotic drugs on monoamine transporters are unknown. We compared labeling of dopamine (DAT) and serotonin (SERT) transporter proteins in subregions of rat corpus striatum by quantitative autoradiography with [(3)H]2-beta-carbomethoxy-3-beta-[4'-iodophenyl]tropane ([(3)H]beta-CIT) and [(3)H]paroxetine after 28 days of continuous subcutaneous infusion of olanzapine, quetiapine, risperidone, or vehicle controls. Drug treatment did not significantly alter the abundance of either transporter type in caudate-putamen or nucleus accumbens, indicating that transporter proteins required to inactivate synaptically released dopamine and serotonin resist adaptations to long-term treatment with novel antipsychotics that affect neurotransmission by these amines.

Human dopamine transporter gene: coding region conservation among normal, Tourette's disorder, alcohol dependence and attention-deficit hyperactivity disorder populations

The dopamine transporter (DAT) provides major regulation of the synaptic levels of dopamine and is a principal target of psychostimulant drugs. Associations between DAT gene polymorphisms and human disorders with possible links to dopaminergic neurotransmission, including attention-deficit/hyperactivity disorder (ADHD) and consequences of cocaine and alcohol administration, have been reported. We now report approximately 60000 bp of genomic sequence containing the entire DAT gene. This sequence was used to amplify each of the 15 DAT gene exons and several introns and analyze these amplification products by single-stranded sequence conformation (SSCP) and/or direct sequencing. These results define silent allelic single nucleotide sequence variants in DAT gene exons 2, 6, 9 and 15. Rare conservative mutations are identified in amino acids encoded by DAT exons 2 and 8. Analyses of the common nucleotide variants and the previously reported VNTR in the non-coding region of exon 15 define the pattern of linkage disequilibrium across the DAT locus. These comprehensive analyses, however, fail to identify any common protein coding DAT sequence variant in more than 150 unrelated individuals free of neuropsychiatric disease, 109 individuals meeting City of Hope criteria for Tourette's syndrome, 64 individuals with DSM-IV diagnoses of ethanol dependence, or 15 individuals with ADHD. These data are consistent with substantial evolutionary conservation of the DAT protein sequence. They suggest that gene variants that alter levels of DAT expression provide the best current candidate mechanism for reported associations between DAT gene markers, ADHD and other more tentatively associated neuropsychiatric disorders.

Suppression of serum gonadal steroids in rats by chronic treatment with dopamine and serotonin reuptake inhibitors

The impact of chronic administration (3 weeks) of dopamine and serotonin reuptake inhibitors on serum gonadal steroid hormones and prolactin was studied in intact male and female rats. Both the dopamine and the serotonin reuptake inhibitors lowered serum estradiol and progesterone levels in the female rats. The dopamine transporter blockers suppressed testosterone serum levels in the male rats, whereas serotonin reuptake inhibitors induced only a non-significant reduction (30%) of this hormone. In contrast to the decrease in gonadal steroids, none of the serotonin or the dopamine reuptake blockers altered prolactin serum levels in either the male or female rats. It seems that the effect of these agents on ovarian and testicular hormones is related to the impact of the monoamine reuptake inhibitors on the hypothalamic-pituitary-gonadal axis.

Neurobiology of the obsessive-compulsive spectrum disorders

Advances in obsessive-compulsive disorder (OCD) research have led to increased attention to a range of disorders with possibly overlapping phenomenological and neurobiological features; the so-called OCD spectrum disorders. This article briefly reviews neurobiological data relevant to the construction of an OCD spectrum, including neurochemical, neuroanatomic, genetic, neuroimmunology, and animal studies. OCD and related disorders may be heterogenous conditions, and the neurobiology of many putative OCD spectrum disorders has not been well studied. Nevertheless, a gradual accumulation of neurobiological data has provided a number of exciting, and partially overlapping, approaches to an hypothesized OCD spectrum.

Expletives: neurolinguistic and neurobehavioral perspectives on swearing

Severe aphasia, adult left hemispherectomy, Gilles de la Tourette syndrome (GTS), and other neurological disorders have in common an increased use of swearwords. There are shared linguistic features in common across these language behaviors, as well as important differences. We explore the nature of swearing in normal human communication, and then compare the clinical presentations of selectively preserved, impaired and augmented swearing. These neurolinguistic observations, considered along with related neuroanatomical and neurochemical information, provide the basis for considering the neurobiological foundation of various types of swearing behaviors.

Developmental and age-related changes of dopamine transporter, and dopamine D1 and D2 receptors in human basal ganglia

The developmental and age-related changes of the dopamine transporter (DAT), and the dopamine D1 and D2 receptor (D1R and D2R) subtypes were investigated in basal ganglia (BG) of human brain. DAT immunostaining was mainly observed in the neuropil, neurons, and glia of the striatum. The DAT-positive neuropil was detectable at 32 GW, a peak being reached at 9-10 years of age, with a decrease to 50-63 years of age. The developmental pattern of DAT immunoreactivity in neuron was similar to that of the neuropil. DAT-positive glia were observed in the BG at 32 GW, which increased slightly at 38-40 GW, and then did not obviously change until 6-8 months after birth. D2R-positive neurons were clearly observed at 19 GW, a peak being reached at 32 GW and 1-3 months of age in the globus pallidus and striatum, respectively, with a decrease after 9-10 years of age. D1R was expressed as early as D2R, but decreased after 6-8 months. Our results suggest that D1R and D2R expression is an intrinsic property of striatal neurons and is independent of dopaminergic innervation. D1R may play a more important role in neuronal maturation of the BG than D2R. D2R may be closely correlated with late neuronal development. The higher expression of DAT during adolescence may be related to function of the BG which learns complex behavioral patterns. The significance of the age-related decreases in DAT, D1R and D2R in the BG remains to be further investigated.

Dopamine transporters and neuronal injury

The plasma membrane dopamine transporter (DAT) and the vesicular monoamine transporter (VMAT2) are essential for normal dopamine neurotransmission. DAT terminates the actions of dopamine by rapidly removing dopamine from the synapse, whereas VMAT2 loads cytoplasmic dopamine into vesicles for storage and subsequent release. Recent data suggest that perturbation of the tightly regulated balance between these two transporters predisposes the neurone to damage by a variety of insults. Most notable is the selective degeneration of DAT- and VMAT2-expressing dopamine nerve terminals in the striatum thought to underlie Parkinson's disease. DAT and VMAT2 expression can predict the selective vulnerability of neuronal populations, which suggests that therapeutic strategies aimed at altering DAT and VMAT2 function could have significant benefits in a variety of disorders.

Striatal dopaminergic markers in dementia with Lewy bodies, Alzheimer's and Parkinson's diseases: rostrocaudal distribution

Dementia with Lewy bodies (DLB) is a neuropsychiatric disease associated with extrapyramidal features which differ from those of Parkinson's disease, including reduced effectiveness of L-dopa and severe sensitivity reactions to neuroleptic drugs. Distinguishing Alzheimer's disease from DLB is clinically relevant in terms of prognosis and appropriate treatment. Dopaminergic activities have been investigated at coronal levels along the rostrocaudal striatal axis from a post-mortem series of 25 DLB, 14 Parkinson's disease and 17 Alzheimer's disease patients and 20 elderly controls. [(3)H]Mazindol binding to the dopamine uptake site was significantly reduced in the caudal putamen in DLB compared with controls (57%), but not as extensively as in Parkinson's disease (75%), and was unchanged in Alzheimer's disease. Among three dopamine receptors measured (D1, D2 and D3), the most striking changes were apparent in relation to D2. In DLB, [(3)H]raclopride binding to D2 receptors was significantly reduced in the caudal putamen (17%) compared with controls, and was significantly lower than in Parkinson's disease at all levels. D2 binding was significantly elevated at all coronal levels in Parkinson's disease compared with controls, most extensively in the rostral putamen (71%). There was no change from the normal pattern of D2 binding in Alzheimer's disease. The only significant alteration in D1 binding ([(3)H]SCH23390) in the groups examined was an elevation (30%) in the caudal striatum in Parkinson's disease. There were no differences in D3 binding, measured using [(3)H]7-OH-DPAT, in DLB compared with controls. A slight, significant decrease in D3 binding in the caudal striatum of Parkinson's disease (13%) patients and an increase in Alzheimer's disease (20%) in the dorsal striatum at the level of the nucleus accumbens were found. The concentration and distribution of dopamine were disrupted in both DLB and Parkinson's disease, although in the caudate nucleus the loss of dopamine in DLB was uniform whereas in Parkinson's disease the loss was greater caudally. In the caudal putamen, dopamine was reduced by 72% in DLB and by 90% in Parkinson's disease. The homovanillic acid : dopamine ratio, a metabolic index, indicated compensatory increased turnover in Parkinson's disease, which was absent in DLB despite the loss of substantia nigra neurons (49%), dopamine and uptake sites. These differences between DLB, Parkinson's disease and Alzheimer's disease may explain some characteristics of the extrapyramidal features of DLB and its limited response to L-dopa and severe neuroleptic sensitivity. The distinct changes in the rostrocaudal pattern of expression of dopaminergic parameters are relevant to the interpretation of the in vivo imaging and diagnosis of DLB.

Immunocytochemical localization of the dopamine transporter in human brain

The dopamine transporter (DAT) was localized in normal human brain tissue by light microscopic immunocytochemistry by using highly specific monoclonal antibodies. Regional distribution of DAT was found in areas with established dopaminergic circuitry, e.g., mesostriatal, mesolimbic, and mesocortical pathways. Mesencephalic DAT-immunoreactivity was enriched in the dendrites and cell bodies of neurons in the substantia nigra pars compacta and ventral tegmental area. Staining in the striatum and nucleus accumbens was dense and heterogeneous. Mesocortical DAT immunoreactivity in motor, premotor, anterior cingulate, prefrontal, entorhinal/perirhinal, insular, and visual cortices was detected in scattered varicose and a few nonvaricose fibers. Varicose fibers were relatively enriched in the basolateral and central subnuclei of amygdala, with sparser fibers in lateral and basomedial subnuclei. Double-labeling studies combining DAT and tyrosine hydroxylase (TH) immunostaining in the ventral mesencephalon showed two subpopulations of dopaminergic neurons differentiated by the presence or absence of DAT-immunoreactivity in the A9 and A10 cell groups. In other dopaminergic cell groups (All, A13-A15), TH-positive hypothalamic neurons showed no detectable DAT-immunoreactivity. However, fine DAT-immunoreactive axons were scattered throughout the hypothalamus, particularly concentrated along the medial border, with more coarse axons present along the lateral border. These findings demonstrate that most mesotelencephalic dopamine neurons of human brain express high levels of DAT throughout their entire somatodendritic and axonal domains, whereas a smaller subpopulation of mesencephalic dopamine cells and all hypothalamic dopamine cell groups examined express little or no DAT. These data indicate that different subpopulations of dopaminergic neurons use different mechanisms to regulate their extracellular dopamine levels.

High presynaptic dopaminergic activity in children with Tourette's disorder

OBJECTIVE

Tourette's disorder is characterized by chronic fluctuating motor and vocal tics. Despite extensive investigation of the neuropathophysiology of the disorder by a wide array of methodologies, its neurobiochemical substrate is still unclear. Converging evidence, however, suggests a primary role of the dopaminergic system, particularly within the basal ganglia.

METHOD

This study examined the integrity of presynaptic dopaminergic function in children with Tourette's disorder, using positron emission tomography and the tracer [18F]fluorodopa (FDOPA). Accumulation of FDOPA in synaptic terminals, a measure of DOPA decarboxylase activity, was quantified in caudate nucleus, putamen, frontal cortex, and midbrain (i.e., substantia nigra and ventral tegmentum).

RESULTS

Subjects with Tourette's disorder showed higher FDOPA accumulation than controls in the left caudate nucleus (by 25%; p = .03) and right midbrain (by 53%; p = .08).

CONCLUSION

These findings provide evidence of dopaminergic dysfunction in children with Tourette's disorder which affects both cell nuclei and nerve terminals. Based on the known regulation of DOPA decarboxylase activity by post- and presynaptic receptors, and by extracellular dopamine concentration, abnormal activity in this enzyme may reflect deficits in a variety of functional elements of the dopamine system. The precise mechanism underlying an up-regulation of DOPA decarboxylase activity needs to be identified in future studies.

Possible role of neuropeptides in obsessive compulsive disorder

The most consistent finding in clinical research of obsessive compulsive disorder (OCD) is the significant treatment advantage of potent serotonin uptake inhibitors (SUIs) over other classes of antidepressant and antianxiety drugs. Clinical neurobiological studies of OCD, however, have yielded limited and inconsistent evidence for significant fundamental abnormalities in monoamine systems including serotonin, norepinephrine and dopamine. Furthermore, one-third to one-half of OCD patients do not experience a clinically meaningful improvement with SUI treatment. Investigation beyond the monoamine systems may be necessary in order to more fully understand the pathophysiology of obsessive-compulsive symptoms and develop improved treatments. Evidence from preclinical studies suggests that neuropeptides may have important influences on memory acquisition, maintenance and retrieval; grooming, maternal, sexual and aggressive behavior; fixed action patterns; and stereotyped behavior; these phenomena may relate to some features of OCD. In addition, extensive interactions have been identified in the brain between neuropeptidergic and monoaminergic systems, including co-localization among specific populations of neurons. The purpose of this review is to present the current knowledge of the role of neuropeptides in the clinical neurobiology of children, adolescents and adults with OCD focusing primarily on results from pharmacological challenge and cerebrospinal fluid studies. Where evidence exists, developmentally regulated differences in neuropeptide function between children and adolescents versus adults with OCD will be emphasized; these data are intended to underscore the potential importance of establishing the age of symptom onset (childhood versus adult) in individual patients with OCD participating in clinical neurobiological investigations. Likewise, where information is available, differences in measures of neuropeptides between patients with non-tic-related OCD versus tic-related OCD will be highlighted; these data will demonstrate the critical value of diagnostic precision, as these two particular subtypes of OCD may have different neurochemical underpinnings.

Visualization of the dopamine transporter in the human brain postmortem with the new selective ligand [125I]PE2I

Using a new, 125I-labeled, selective high affinity dopamine transporter ligand, N-(3-iodoprop-2E-enyl)-2beta-carbomethoxy-3beta-(4'-methy lph enyl)nort ropane (PE2I), the distribution of the dopamine transporter was characterized in the normal postmortem human brain using whole hemisphere autoradiography. PE2I was radioiodinated to high specific radioactivity (2200 Ci/mmol, 81 GBq/micromol). PE2I binds to the dopamine transporter with high potency and, in contrast to beta-CIT, it has very low affinities for the serotonin and noradrenaline transporters. The autoradiograms showed very intense binding in basal ganglia (putamen, nucleus caudatus, nucleus accumbens) and lower binding in substantia nigra. Very low or no binding was found in other brain structures, including the neocortex or cerebellum. The labeling of human dopamine transporters with [125I]PE2I was inhibited by the dopamine transporter inhibitors GBR 12909 and beta-CIT, but not by citalopram (serotonin transporter inhibitor) or maprotiline (noradrenaline transporter inhibitor). Possibly due to the relatively high lipophilicity of the compound (theoretical log p = 4.68), it accumulated slightly in white matter. Thus, in vitro autoradiography using [125I]PE2I provided detailed qualitative and quantitative evidence that the dopamine transporter is almost exclusively localized in the basal ganglia of the human brain. Moreover, the autoradiograms indicate that [11C]PE2I and [123I]PE2I should be suitable for the in vivo visualization of the human dopamine transporter with PET or SPECT, respectively.

The temporal dynamics of tics in Gilles de la Tourette syndrome

BACKGROUND

Statistical characterization of tic behavior in Gilles de la Tourette syndrome (GTS) may provide insight into the dynamic functioning of the human central nervous system, as well as improve the quantitative assessment of tic symptom severity.

METHODS

Twenty-two medication-free GTS subjects underwent videotaping of their tics. The intervals between temporally adjacent tics were measured, and the statistical properties of these intervals were assessed through graphical representation of frequency distributions, autoregressive integrated moving average (ARIMA) modeling, spectral analysis, and construction of first return maps.

RESULTS

The frequency distribution of tic interval durations followed an inverse power law of temporal scaling. Spectral analyses similarly demonstrated that the spectral power density of tic interval duration scales inversely with frequency. ARIMA modeling suggested that the time series for tics are nonstationary as well as moving average processes. The first return maps demonstrated "burstlike" behavior and short-term periodicity in tics, and proved that successive tic intervals are not statistically independent. Graphic display of the time series confirmed shortterm periodicity, and in addition suggested the presence of period doubling.

CONCLUSIONS

These findings are suggestive though not conclusive evidence for the presence of a fractal, deterministic, and possibly chaotic process in the tic time series. These analytic methods provide insight into the temporal features of tics that commonly are described clinically (such as short-term bouts or bursting, and longer term waxing and waning), and they reveal certain important temporal features of tics that have not been clinically described. The methods may also prove useful in the improved characterization of tic symptom severity.

Dopamine uptake by platelet storage granules in first-degree relatives of Tourette's syndrome patients

BACKGROUND

Considering that platelets have been established to be good peripheral markers for the study of catecholaminergic neurons, we have applied an assay to measure the uptake of (3H)-dopamine (DA) into platelet storage granules (PSG). Recently, we reported that Tourette's syndrome (TS) patients (pts) show decreased DA uptake into PSG.

METHODS

In the present study, 28 first-degree relatives (3 with chronic motor tics, 3 with transient tics, 6 with obsessive-compulsive behavior, and 16 without symptomatology) belonging to the families of 13 patients, and 14 unrelated healthy controls were studied.

RESULTS

Double reciprocal plots were constructed for each subject, and the apparent maximum velocity (Vmax) and Michaelis constant (K(m)) were determined by linear regression analysis (Lineaweaver-Burke plots). The uptake of DA (0.5-5 mumol/L) (mean +/- SEM) by PSG from relatives with symptomatology was similar to the TS patients (symptomatic relatives Vmax 181 +/- 22.2 fmol/mg protein, K(m) (mumol/L) 6.42 +/- 0.29; TS pts Vmax 108 +/- 6.9, K(m) 7.79 +/- 0.64). Relatives without symptomatology on the contrary showed DA affinity characteristics similar to the controls (t test, paired t test, multivariate analysis of variance, and log transformation).

CONCLUSIONS

The data presented suggest that TS is hereditary, but they do not distinguish between an autosomal dominant inheritance and a mixed or polygenic model.

Postnatal development of dopamine and serotonin transporters in rat caudate-putamen and nucleus accumbens septi

Density of dopamine transporter (DAT) and serotonin transporter (5-HTT) membrane proteins in the caudate-putamen (CPu) and nucleus accumbens (NAc) of rat brain was assessed at seven ages at postnatal days (PD) 7-60, by in vitro quantitative autoradiography. Binding of [3H]GBR-12935 (to DAT) and [3H]paroxetine (to 5-HTT) increased steadily and very similarly, from low levels at PD-7 to maximal levels, to 6-7-fold higher density at PD-60 in both regions. These findings indicate that DAT and 5-HTT follow a synchronized course of development in rat CPu and NAc. In contrast to reported elimination of excessive receptors in CPu and NAc during maturation, there was no evidence of pruning of DAT or 5-HTT in these regions of rat forebrain.

Neuroreceptor imaging: new developments in PET and SPECT imaging of neuroreceptor binding (including dopamine transporters, vesicle transporters and post synaptic receptor sites)

Positron emission tomography and single photon emission computed tomography have been used to measure receptor concentration and function through the use of a variety of radiotracers and data analysis techniques. Changes in presynaptic function and postsynaptic receptor concentration reflect both loss due to disease and compensatory responses.

Localization and dynamic regulation of biogenic amine transporters in the mammalian central nervous system

The monoamines, serotonin, dopamine, norepinephrine, epinephrine and histamine, play a critical role in the function of the hypothalamic-pituitary-adrenal axis and in the integration of information in sensory, limbic, and motor systems. The primary mechanism for termination of monoaminergic neurotransmission is through reuptake of released neurotransmitter by Na+, CI-dependent plasma membrane transporters. A second family of transporters packages monoamines into synaptic and secretory vesicles by exchange of protons. Identification of those cells which express these two families of neurotransmitter transporters is an initial step in understanding what adaptive strategies cells expressing monoamine transporters use to establish the appropriate level of transport activity and thus attain the appropriate efficiency of monoamine storage and clearance. The most recent advances in this field have yielded several surprises about their function, cellular and subcellular localization, and regulation, suggesting that these molecules are not static and most likely are the most important determinants of extracellular levels of monoamines. Here, information on the localization of mRNAs for these transporters in rodent and human brain is summarized along with immunohistochemical information at the light and electron microscopic levels. Regulation of transporters at the mRNA level by manipulation in rodents and differences in transporter site densities by tomographic techniques as an index of regulation in human disease and addictive states are also reviewed. These studies have highlighted the presence of monoamine neurotransmitter transporters in neurons but not in glia in situ. The norepinephrine transporter is present in all cells which are both tyrosine hydroxylase (TH)- and dopamine beta-hydroxylase-positive but not in those cells which are TH- and phenyl-N-methyltransferase-positive, suggesting that epinephrine cells may have their own, unique transporter. In most dopaminergic cells, dopamine transporter mRNA completely overlaps with TH mRNA-positive neurons. However, there are areas in which there is a lack of one to one correspondence. The serotonin transporter (5-HTT) mRNA is found in all raphe nuclei and in the hypothalamic dorsomedial nucleus where the 5-HTT mRNA is dramatically reduced following immobilization stress. The vesicular monoamine transporter 2 (VMAT2) is present in all monoaminergic neurons including epinephrine- and histamine-synthesizing cells. Immunohistochemistry demonstrates that the plasma membrane transporters are present along axons, soma, and dendrites. Subcellular localization of DAT by electron microscopy suggests that these transporters are not at the synaptic density but are confined to perisynaptic areas, implying that dopamine diffuses away from the synapse and that contribution of diffusion to dopamine signalling may vary between brain regions. Interestingly, the presence of VMAT2 in vesicles underlying dendrites, axons, and soma suggests that monoamines may be released at these cellular domains. An understanding of the regulation of transporter function may have important therapeutic consequences for neuroendocrine function in stress and psychiatric disorders.

Altropane, a SPECT or PET imaging probe for dopamine neurons: I. Dopamine transporter binding in primate brain

Increasing evidence suggests that the dopamine transporter is an important marker for physiological and pathological changes in dopamine neurons. Potent dopamine transport inhibitors of the phenyltropane series (e.g., WIN 35,428 or CFT) are particularly suitable for PET (positron emission tomography) or SPECT (single photon emission computed tomography) imaging of the dopamine transporter in living brain. We investigated whether altropane, an N-iodoallyl analog of WIN 35,428 (IACFT:E-N-iodoallyl-2 -carbomethoxy-3beta-(4-fluorophenyl)tropane), displayed in vitro properties suitable for evaluation as a SPECT imaging agent. In brain striatum of cynomolgus monkey (Macaca fascicularis), the unlabeled E-isomer (IC50: 6.62 +/- 0.78 nM) was more potent than the Z-isomer (IC50: 52.6 +/- 0.3 nM) and displayed a relatively high dopamine:serotonin transporter selectivity (28-fold). In radiolabeled form, [125I]altropane bound to sites in the striatum with a single high affinity (KD: 5.33 +/- 0.55 nM) and with a site density (BMAX: 301 pmol/g original wet tissue weight) that was within the density range reported previously for the dopamine transporter in striatum. Drugs inhibited [125I]altropane binding with a rank order of potency that corresponded closely to their potencies for inhibiting [3H]WIN 35,428 binding (r2: 0.99; P < 0.0001) to the blocking dopamine transport. The favorable binding properties of altropane, together with its rapid entry into primate brain and highly localized distribution in dopamine-rich brain regions, suggest it is a suitable iodinated probe for monitoring the dopamine transporter in vitro and in vivo by SPECT or PET imaging.

A developmental study of the dopamine D2R receptors in the human basal ganglia and thalamus

The development of the dopamine D2R receptors (D2R) in the human basal ganglia (BG) and thalamus was investigated in 25 normal brains by means of an immunohistochemical method and Western blotting. Immunoreactivity to D2R was detected in the cytoplasm and dendrites of small and large neurons in the BG and thalamus. D2R-positive neurons were clearly observed at 19 weeks of gestation (GW) in the globus pallidus and thalamus, and at 21 GW in the striatum. The number of D2R-positive neurons gradually increased and reached a peak at 27 GW in the globus pallidus, at 39 GW in the thalamus, and at 1 month of age in the striatum. The number of D2R-positive large neurons in the globus pallidus and small neurons in the striatum decreased after 1 year and about 10 years of age, respectively. Western blotting confirmed the specificity of the immunohistochemistry. Our results suggest that the D2R protein begins to be synthesized at an early fetal stage in the BG and thalamus, and the development of D2R is mostly consistent with neuronal maturation in the BG. D2R may play an important role in regulating the neuronal development of the BG. The decrease in D2R-positive neurons may be related to D2R post-transcriptional regulation.

Effects of prenatal methylazoxymethanol treatment on striatal dopaminergic systems in rat brain

To further examine the effects of prenatal methylazoxymethanol (MAM) treatment on striatal dopaminergic systems, the status of presynaptic dopamine transporters was examined by quantitative autoradiography of [3H]GBR 12935 binding. Significantly higher [3H]GBR 12935 binding was seen in MAM-lesioned striatum in comparison to the controls, indicating relative dopaminergic hyperinnervation in MAM-induced hypoplastic striatum. The effect of prenatal MAM treatment on extracellular levels of dopamine and its metabolites in the striatum was also examined using in vivo microdialysis. As measured in conscious freely-moving rats, prenatal MAM treatment significantly increased basal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) release in the striatum in comparison with control rats. These data suggest that in accordance with morphological dopaminergic hyperinnervation, dopaminergic functions are significantly augmented in MAM-lesioned brains. Thus, it is suggested that MAM-induced microencephalic rats should serve as a good animal model for the study of augmented dopaminergic functions in the striatum.

Dopamine transporter development in postnatal rat striatum: an autoradiographic study with [3H]WIN 35,428

The dopamine transporter mediates the reinforcing effects of cocaine, thus playing a central role in human cocaine addiction, and perhaps providing the mechanism for inducing the effects of prenatal cocaine exposure. This possibility has stimulated growing interest in the normal and abnormal development of this transporter. [3H]WIN 35,428 is a cocaine analog that is useful for studying the distribution and density of the dopamine transporter in striatum and other brain regions. The postnatal development of the dopamine transporter in the rat striatum was measured by quantitative autoradiography with [3H]WIN 35,428. Dopamine transporter levels were low at birth, increased through day 15, followed by much more rapid growth in late postnatal development. The majority of the transporter sites appeared after day 15. Lateral to medial and anterior to posterior gradients in transporter density were established early during development, and there was also an early concentration of transporter in striosomes that became difficult to identify by day 15. Differences between the developmental patterns described here and studies using other ligands for the dopamine transporter suggest there are significant differences in the transporter binding sites for these drugs. These differences in transporter ligand binding characteristics may reflect developmental changes in post-translational modification of the transporter and/or changes in the functional activity rather than simply the presence of the transporter.

Tic disorders

The picture that emerges is one of complex behavioral phenotypes that alter over the course of CNS development. While many cases are mild and may not come to medical attention, others are chronic and disabling. The aim of this article is to provide an overview of recent progress in understanding phenomenology, epidemiology, genetics, neurobiology, and treatment of tic disorders.

Neuroimaging and neuropsychology of the striatum. Bridging basic science and clinical practice

Neuroimaging and neuropsychology are complementary disciplines that provide powerful means for assessing the structure and function of corticostriatal systems. Findings from four model basal ganglia disorders--OCD, TS, HD, and PD--are reviewed. This survey is intended as a vehicle for illustrating the breadth of current clinical and research applications, as well as the potential for future advances. The perspectives brought by neuroimaging and neuropsychology serve as a natural bridge from the basic neuroscience to the clinical practice articles in this issue.

Dopamine function in obsessive-compulsive disorder: growth hormone response to apomorphine stimulation

Indirect observations suggest that the dopaminergic system may be involved in the pathophysiology of obsessive-compulsive disorder (OCD). The dopaminergic function of 15 patients with OCD and 15 age/sex-matched controls was evaluated by measuring the growth hormone (GH) responses to stimulation with the dopaminergic agonist apomorphine (APO), which increases growth hormone-releasing hormone (GHRH), GH, and somatomedine C (SMD-C) secretions. Therefore, we measured basal plasma GH and SMD-C concentrations and GH responses to GHRH stimulation to exclude that a downstream pathology of the somatotropic axis could obscure the significance of the results of the APO test. The response of prolactin (PRL) to APO inhibition were also measured. Basal plasma levels of GH, SMD-C, and PRL, GH responses to GHRH stimulation, and PRL responses to APO inhibition did not differ in the two groups of subjects. GH responses to APO stimulation were blunted in obsessive-compulsive (OC) patients. The emetic response to the same stimulation was stronger in patients than in controls. These responses suggest that in our OC patients there is a dysregulation of the dopaminergic system, which is possibly expressed in different ways in the various areas of the central nervous system.

Reduced striatal vesicular monoamine transporters after neurotoxic but not after behaviorally-sensitizing doses of methamphetamine

Prior studies indicate long-term reductions of striatal dopaminergic markers after sustained, high dose methamphetamine exposures in vivo, suggesting a neurotoxic effect. We have reported lack of regulation of vesicular monoamine transporter type-2 expression, as opposed to other markers of striatal dopaminergic terminals, under conditions that alter dopaminergic transmission without synaptic terminal losses. In the present study, we evaluated the vesicular monoamine transporter and the neuronal membrane dopamine transporter in rat striata after in vivo exposure to neurotoxic or to intermittent, low dose (behaviorally-sensitizing, non-neurotoxic) methamphetamine administrations. Vesicular monoamine transporter binding was measured by autoradiography of (+)-[3H]dihydrotetrabenazine, the active isomer of (+/-)-[3H]dihydrotetrabenazine. (+)-Dihydrotetrabenazine bound to a homogeneous population of striatal sites in controls with a Kd of 1.5 nM and a Bmax of 3.8 fmol/microg protein. Neurotoxic methamphetamine treatment reduced both striatal vesicular monoamine transporter (-26%) and dopamine transporter (-39%) bindings. There were no changes after the non-neurotoxic treatment regimen. The vesicular monoamine transporter may thus be a valuable marker in the further clinical study of psychostimulant drug neurotoxicity.

Tics secondary to craniocerebral trauma

We describe three adult patients who presented with multifocal motor and vocal tics secondary to craniocerebral trauma. In one case, the tics were accompanied by marked obsessive-compulsive behavior. All patients were involved in motor vehicle accidents resulting in closed craniocerebral trauma. The latency of onset between head trauma and the movement disorder varied between 1 day and a few months. Magnetic resonance imaging, which was performed in all three patients, did not detect any structural lesions of the basal ganglia or the brainstem. Extensive bifrontal leukoencephalopathy was found in one patient who suffered severe head trauma.

A neurobiological model for Tourette syndrome centered on the nucleus accumbens

Tourette syndrome is a genetic disorder characterized by chronic multiple motor and vocal tics with a fluctuating course and modulated by internal and external environmental events. Tourette syndrome is more prevalent in males than females, and is associated with behavioural disorders such as obsessive-compulsive disorder and attention deficit hyperactivity disorder. Tourette syndrome symptoms are commonly attenuated by dopaminergic antagonists and adrenergic agonists, and usually exacerbated by psychostimulants. In this paper, I propose that dysfunction centered on the nucleus accumbens represents the neurobiological basis of Tourette syndrome. Recent evidence indicates that nucleus accumbens has a micro-organization characterized by modules of distinct neurochemical and neuroanatomical features. Our model assumes that external and internal events occurring during the development of the nervous system interact with products derived from the expression of the putative gene for Tourette syndrome, thereby inducing modular changes in nucleus accumbens. The clinical presentation, associated behavioural disturbances and response to drugs would depend on the pattern of modular dysfunction.

Saccades in Gilles de la Tourette's syndrome

Gilles de la Tourette's syndrome (GTS) is presumed to be an inherited disorder with an unclear pathophysiology. An involvement of the basal ganglia is suspected. Besides vocal tics, one of the main symptoms is the presence of motor tics. As eye movements are a specialized part of the motor system, we investigated whether they differed in some typical way in GTS patients. To study the control of saccades in GTS, different paradigms were used to elicit saccades, which were either externally triggered and visually guided or internally triggered and without visual target. GTS patients (n = 10) showed a significant increase of the latency of antisaccades, a highly impaired performance of sequences of memory-guided saccades, and an isolated reduction of the peak velocity in the antisaccades. Overall the results were similar to those found with similar paradigms in patients with Huntington's disease (HD). In analogy to the known pathology of HD, these findings can be attributed to ascending loops from the basal ganglia that inappropriately activate the frontal cortex, especially some of the eye movement-related areas there. This impairment seems to be a rather specific effect, since some oculomotor features that are preserved by structures of the frontal cortex, such as the effect of a fixation target on saccadic latency ("gap effect"), were normal.

Ovariectomy and estradiol treatment affect the dopamine transporter and its gene expression in the rat brain

The impact of gonadal hormone withdrawal and estrogen therapy was investigated on the rat dopamine transporter (DAT). Short-term ovariectomized (ST-OVX, 2 weeks) and long-term ovariectomized (LT-OVX, 3 months) rats were treated or not with 17beta-estradiol (E2) for 2 weeks. DAT mRNA expression was measured by in situ hybridization in the substantia nigra pars compacta (SNc) for the nigrostriatal pathway and the ventral tegmental area (VTA) for the mesolimbic pathway whereas DAT levels were assessed by [3H]GBR-12935 autoradiography, respectively, in the striatum and the nucleus accumbens. Ovariectomy produced a time-dependent decrease of the DAT density in the striatum and the nucleus accumbens and the E2 treatment did not significantly restore these DAT levels. Neither ST-OVX nor E2 treatment of the ST-OVX animals altered the DAT mRNA expression in the SNc and the VTA. However, LT-OVX animals showed increased DAT mRNA levels in these regions. E2 treatment of LT-OVX animals partially restored DAT mRNA levels in the SNc and left these levels unchanged in the VTA. These opposite variations induced by OVX on the DAT density and their mRNA levels suggest the involvement of non-genomic mechanisms, such as post-transcriptional events and/or membrane effects. Altered neurotransmission following gonadal hormone withdrawal may contribute to CNS disorders occurring at menopause in predisposed women. Ovariectomized rats constitute a useful model to study the changes in neurotransmitters balance occurring after menopause.

Opposite modulatory effects of ovarian hormones on rat brain dopamine and serotonin transporters

The present study was designed to investigate the modulatory effect of gonadal steroids on brain dopamine (DA) and serotonin (5-HT) presynaptic transporters in female and male rats. Female and male rats were castrated and treated with either vehicle or gonadal hormones. The pharmacodynamic characteristics of the DA and 5-HT transporters were analyzed by [3H]BTCP and [3H]imipramine binding respectively. Ovariectomy (OVX) resulted in an upregulation of the striatal DA transporter and this alteration was prevented by estradiol (E2) or E2 + progesterone (P) treatment but not by P alone. In contrast to the DA transporter, the hypothalamic 5-HT transporter was down-regulated by OVX in female rats and this decrease was reversed by the administration of E2, P or their combination. The striatal DA transporter and the hypothalamic 5-HT transporter in male rat were not affected by orchidectomy or by administration of testicular hormone. Our findings indicate that ovarian, but not testicular, steroid hormones may play an important role in the regulation of brain DA and 5-HT transporters. It appears that ovarian hormones modulate rat brain 5-HT and DA transporters in opposite directions. These interactions between ovarian steroids and presynaptic transporters may be relevant to DA- and 5-HT-related neuropsychiatric disorders.

Tourette syndrome. Secondary tic disorders

The putative relationship between a variety of neurologic and neuropsychiatric disorders, which have been reported in association with tics, is reviewed. Tics also may be increased or exacerbated by drugs affecting a variety of neurotransmitter systems. Recognition and study of these secondary tic disorders may further our understanding of basal ganglia physiology and the pathogenesis of Tourette syndrome.

Neurobiology of Tourette syndrome

This article includes a discussion of approaches designed to determine neuroanatomic localization through the use of physical examination, electrophysiologic and neuroradiographic studies, and neuropathologic evaluations. The author reviews the anatomy, function, and biochemistry of frontal-subcortical circuits. Inferred and direct evidence that supports a disorder of frontal-subcortical circuits in Tourette syndrome is presented. Studies investigating specific neurotransmitters are reviewed.

Behavioral and emotional aspects of Tourette syndrome

This article reviews the behavioral and emotional aspects of Tourette syndrome with a focus on behavioral phenomenology and psychiatric comorbidity. Tourette syndrome is a complex neuropsychiatric disorder characterized by disinhibition and dysfunction of the regulation of motor, cognitive, affective, and behavioral functions. Although multiple motor and vocal tics are the key diagnostic phenomena, hyperactivity, impulsivity, inattention, obsessive-compulsive, and emotional symptoms are common in many patients. Evaluation and treatment should take into account the behavioral and emotional symptoms as well as the tics. Treatment should incorporate multimodal strategies so as to address both the tics and symptoms.

Frontal-subcortical circuits: the anatomic basis of executive, social and motivated behaviors

A series of discrete, parallel frontal-subcortical circuits have been demonstrated to link specific areas of the frontal lobe to areas within the basal ganglia and thalamus. A variety of circuit-specific behaviors can be described involving the dorsolateral prefrontal, orbitofrontal and anterior cingulate circuits. Interruptions or imbalance occurring at various levels within these closed looped circuits is felt to underlie the characteristic behavioral patterns seen. The intricate neurochemical arrangement of the striatum and the complex neurotransmitter interactions that occur within these key subcortical structures from the basis for modulatory influences that can affect these circuits.

Pathogenesis of Tourette's syndrome

This review presents a models of disease pathogenesis in the context of CNS development. It begins with an exploration of the clinical features and natural history of Tourette's syndrome. This is followed by a consideration of the role of genetic and nongenetic factors. An effort is then made to review the anatomical organization of the basal ganglia and related cortical sites. These circuits are intimately involved in the normal processing of sensorimotor, cognitive, and emotionally laden information. Evidence implicating these circuits in the pathobiology of Tourette's syndrome is then considered. The review closes with the prospects for advances in interdisciplinary research and therapeutics using this model as a guide.

Tourette syndrome: prediction of phenotypic variation in monozygotic twins by caudate nucleus D2 receptor binding

Tourette syndrome, a chronic tic disorder with autosomal dominant inheritance, exhibits considerable phenotypic variability even within monozygotic twin pairs. The origins of this variability remain unclear. Recent findings have implicated the caudate nucleus as a locus of pathology, and pharmacological evidence supports dopaminergic involvement. Within monozygotic twins discordant for Tourette syndrome severity, differences in D2 dopamine receptor binding in the head of the caudate nucleus predicted differences in phenotypic severity (r = 0.99); this relation was not observed in putamen. These data may link Tourette syndrome with a spectrum of neuropsychiatric disorders that involve associative striatal circuitry.

Tics status

OBJECTIVES

To describe two patients with tics status, propose a definition of this syndrome and draw attention to its clinical significance.

METHOD

Two patients suffering from Tourette's Syndrome who had developed episodes of continual motor tics that lasted from minutes to hours, were non-suppressible and intruded into normal functioning, were treated with an increase in the dose of haloperidol, in one case with the addition of clonazepam.

RESULTS

The offset of the episodes was gradual and the tic disorder was worse after the episodes. One patient had further spontaneous episodes of tics status.

CONCLUSIONS

The recognition of tics status has implications for the management as well as our understanding of the pathobiology of tics and Tourette's Syndrome. The definition of tics status should be standardised.

Polygenic inheritance of Tourette syndrome, stuttering, attention deficit hyperactivity, conduct, and oppositional defiant disorder: the additive and subtractive effect of the three dopaminergic genes--DRD2, D beta H, and DAT1

Polymorphisms of three different dopaminergic genes, dopamine D2 receptor (DRD2), dopamine beta-hydroxylase (D beta H), and dopamine transporter (DAT1), were examined in Tourette syndrome (TS) probands, their relatives, and controls. Each gene individually showed a significant correlation with various behavioral variables in these subjects. The additive and substractive effects of the three genes were examined by genotyping all three genes in the same set of subjects. For 9 of 20 TS associated comorbid behaviors there was a significant linear association between the degree of loading for markers of three genes and the mean behavior scores. The behavior variables showing the significant associations were, in order attention deficit hyperactivity disorder (ADHD), stuttering oppositional defiant, tics, conduct, obsessive-compulsive, mania, alcohol abuse and general anxiety-behaviors that constitute the most overt clinical aspects of TS. For 16 of the 20 behavior scores there was a linear progressive decrease in the mean score with progressively lesser loading for the three gene markers. These results suggest that TS, ADHD, stuttering oppositional defiant and conduct disorder, and other behaviors associated with TS, are polygenic, due in part to these three dopaminergic genes, and that the genetics of other polygenic psychiatric disorders may be deciphered using this technique.

Sensorimotor gating in boys with Tourette's syndrome and ADHD: preliminary results

Deficits in sensorimotor gating, defined by prepulse inhibition (PPI), have been associated with subcortical dopaminergic overactivity in animal and clinical studies. Utilizing supraorbital nerve electrical stimulation, we produced adequate blink responses and measured decreases in amplitude resulting from electric prestimuli just above sensory threshold. Seven boys comorbid for attention-deficit hyperactivity disorder (ADHD) and a tic disorder had significantly reduced PPI, compared to 14 screened controls and seven boys with ADHD alone. If independently replicated, these results may reflect greater neurologic immaturity in these comorbid subjects. Alternatively, these findings, together with other converging lines of evidence, suggest that deficient pallidal inhibition may be etiologically related to tic and movement disorders.

IPT: a novel iodinated ligand for the CNS dopamine transporter

An iodinated cocaine derivative, N-(3'-iodopropen-2'-yl)-2 beta-carbomethoxy-3 beta-(4-chlorophenyl) tropane (IPT), was evaluated as a probe for in vitro and in vivo labeling of dopamine (DA) and serotonin (5-HT) transporters in Sprague-Dawley rat brain. Saturation analysis of [125I]IPT in rat striatal homogenates, in two different buffer solutions, Tris-HCl and phosphate, demonstrated a one-site binding with affinities (Kd) of 0.25 +/- 0.02 and 0.16 +/- 0.02 nM and densities (Bmax) of 939 +/- 161 and 1,982 +/- 137 fmol/mg protein, respectively. Competition by known DA transporter ligands showed a rank order of RTI-55 > IPT > GBR12909 > mazindol > (-)cocaine. Binding to 5-HT transporter sites was evaluated in rat cortical homogenates. Saturation experiment results showed a single site with a Kd value of 1.2 +/- 0.2 nM and a Bmax value of 100 +/- 20 fmol/mg protein. The rank order of potency of several monoamine uptake inhibitors (paroxetine > fluoxetine > mazindol > R-nisoxetine > GBR12909) suggests that [125I] IPT labels 5-HT transporters in rat cortical homogenates. Both ex vivo and in vitro autoradiographic studies revealed high densities of [125I]IPT binding sites in the caudate nucleus, putamen, olfactory tubercle and nucleus accumbens, areas known to be rich in dopaminergic innervation. Moderate accumulation of activity was also observed in the substantia nigra. The dorsal raphe, a region with a high density of 5-HT innervation, was labeled using in vitro autoradiography with [125I]IPT, but the labeling using ex vivo autoradiography was less prominent at 30 min postinjection and not noticeable at 60 min postinjection.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental and age-related alterations in rat brain presynaptic dopaminergic mechanisms

Age-related changes in both pre- and post-synaptic components of dopamine neurons have been demonstrated in humans as well as in animals. Our study was designed to examine the effects of age on presynaptic DA neurons. To assess the developmental changes in rat striatal dopamine carrier, we used [3H]GBR 12935, which binds selectively to this transporter. In addition we monitored changes in amphetamine- and KCl-induced [3H]DA release from rat striatal slices. We were able to demonstrate age dependent changes in DA transporter density, which reached a peak at age 3 months. Amphetamine-induced released of stored DA was exactly reversed, with a nadir at age 3 months. We assumed that the combination of low DA transporter level with increased transporter-mediated DA release may have a major compensatory role with respect to the maintenance of dopaminergic transmission during normal development, aging and neuro-degenerative diseases.

[3H]GBR 12935 labels mainly the piperazine acceptor site in the rat prefrontal cortex

The binding characteristics of [3H]GBR 12935, a ligand for the dopamine (DA) transporter, have been extensively investigated in the striatum. The present study was designed to characterize [3H]GBR 12935-binding to prefrontal cortex (PFC) in rats. This region receives a dense DA input from the ventral tegmental area and is suspected to play a major role in higher associative functions. We demonstrated high-affinity, saturable, mazindol-sensitive [3H]GBR 12935-binding in the rat PFC; however, in contrast to the striatum, such binding was inhibited by increasing concentrations of Na+. This fact, together with the irregular pattern of the association kinetics and the marked sensitivity of [3H]GBR 12935-binding to piperazine derivatives, indicates the possible presence of more than one [3H]GBR 12935-binding site in the PFC. Furthermore, it appears that [3H] 12935 in the rat PFC labels mainly 'the piperazine acceptor site' and not the DA transporter.