A measure of striatal function predicts motor stereotypy

Sociality, stress, and the corpus striatum of the green anolis lizard

The green anolis lizard, Anolis carolinensis, is a uniquely convenient species with great potential for providing insights about the causes and consequences of social behavior from an evolutionary perspective. In this species, social interactions are mediated by visual displays in which specific units of behavior are combined in various ways to communicate several more-or-less specific messages. Two related research programs that utilize this species converge in provocative ways to provide insight into this phenomenon. The first program is centered on the basal ganglia, now known to be crucial to the expression of aggressive territoriality in this species, and the second research program examines the way the physiological stress response is involved in aggression and its subsequent adaptive outcomes. Both the neural and the neuroendocrine systems affect the progress of social interactions as well as the subsequent social dominance relationships when combatants subsequently live together. Further, because body color depends almost exclusively on the stress response, skin color provides a unique in situ bioassay of otherwise inaccessible information about the animal's internal state. The fullest understanding of the physiological ethology of this model species will depend on an interdisciplinary approach that considers both proximate (physiological) and ultimate (evolutionary) causes of displays. Questions thus arising include how the nervous system controls and assembles the specific units of behavior-motor patterns and autonomic reflexes-into displays that are adaptive in specific contexts.

Expression of Foxp2, a gene involved in speech and language, in the developing and adult striatum

Many members of the forkhead/winged helix transcriptional factors are known to be regulators of embryogenesis. Mutations of the Fox gene family have been implicated in a range of human developmental disorders. Foxp2, a member of the Fox gene family, has recently been identified as the first gene that is linked to an inherited form of language and speech disorder. To elucidate the anatomical basis of language processing in the brain, we have examined the expression pattern of Foxp2 gene and its homologous gene, Foxp1, in the rat brain through development. Expression of Foxp2 mRNA was detected in the ventral telencephalon as early as embryonic day 13. Foxp2 mRNA was expressed primarily in differentiated cells of the lateral ganglionic eminence (striatal primordium). Of particular interest was that the developmental expression of Foxp2 followed a compartmental order in the striatum. Patches containing high levels of Foxp2 were aligned with patches enriched in mu-opoid receptor, a marker for striosomal cells, in the striatum through postnatal development. Conversely, Foxp2-positive patches were devoid of calbindin-D28k, a maker for striatal matrix cells. Therefore, Foxp2 was preferentially expressed in striosomal compartment in the striatum during development. In the mature striatum, Foxp2 expression was maintained in striosomes, although its expression level was reduced. In contrast to Foxp2, Foxp1 was expressed in both the striosomal and matrix compartments in the striatum through development. The striatum is known to be involved in the process of procedural memory, and mutation of Foxp2 results in neurological disorders of language and speech. Given the preferential expression of Foxp2 in the striosomal compartment, the striatum, particularly the striosomal system, may participate in neural information processing for language and speech. Our suggestion is consistent with the declarative/procedural model proposed by Ullman and colleagues (Ullman et al. [1997] J. Cogn. Neurosci. 9:266-276; Ullman [2001] Nat. Rev. Neurosci. 2:717-726), in which the procedural memory-dependent mental grammar is rooted in the basal ganglia and the frontal cortex and the declarative memory-dependent mental lexicon is rooted in the temporal lobe.

Neurotensin: dual roles in psychostimulant and antipsychotic drug responses

Central administration of neurotensin (NT) results in a variety of neurobehavioral effects which, depending upon the administration site, resemble the effects of antipsychotic drugs (APDs) and psychostimulants. All clinically effective APDs exhibit significant affinities for dopamine D(2) receptors, supporting the hypothesis that an increase in dopaminergic tone contributes to schizophrenic symptoms. Psychostimulants increase extracellular dopamine (DA) levels and chronics administration can produce psychotic symptoms over time. APDs and psychostimulants induce Fos and NT expression in distinct striatal subregions, suggesting that changes in gene expression underlie some of their effects. To gain insight into the functions of NT, we analyzed APD and psychostimulant induction of Fos in NT knockout mice and rats pretreated with the NT antagonist SR 48692. In both NT knockout mice and rats pretreated with SR 48692, haloperidol-induced Fos expression was markedly attenuated in the dorsolateral striatum; amphetamine-induced Fos expression was reduced in the medial striatum. These results indicate that NT is required for the activation of specific subpopulations of striatal neurons in distinct striatal subregions in response to both APDs and psychostimulants. This review integrates these new findings with previous evidence implicating NT in both APD and psychostimulant responses.

Cyclic AMP responsive element binding protein phosphorylation and persistent expression of levodopa-induced response alterations in unilateral nigrostriatal 6-OHDA lesioned rats

Activation of cAMP responsive element binding protein (CREB) has been increasingly implicated in the formation and maintenance of long-term memory. To elucidate molecular mechanisms that underlie the persisting alterations in motor response occurring with levodopa (L-dopa) treatment of parkinsonian patients, we evaluated the time course of these changes in relation to the activation of striatal CREB in 6-hydroxydopamine (6-OHDA) lesioned animals. Three weeks of twice-daily L-dopa treatment reduced the duration of the rotational response to acute L-dopa challenge in hemiparkinsonian rats, which lasted about 5 weeks after withdrawal of chronic L-dopa therapy. This shortened response duration, resembling human wearing-off fluctuations, was associated with a marked increase in Ser-133 phosphorylated CREB (pCREB) immunoreactivity in medium spiny neurons in dorsolateral striatum in response to acute dopaminomimetic challenge. Intermittent treatment with the D1 receptor-preferring agonist SKF 38393, but not the D2 receptor-preferring agonist quinpirole, produced a similar rise in CREB phosphorylation. The time course of changes in CREB phosphorylation correlated with the time course of changes in motor behavior after cessation of chronic L-dopa therapy. Both the altered motor response duration and the degree of CREB phosphorylation were attenuated by the intrastriatal administration of CREB antisense or protein kinase A inhibitor Rp-cAMPS. The results suggest that region-specific Ser-133 CREB phosphorylation in D1 receptor containing spiny neurons contributes to the persistence of the motor response alterations produced by intermittent stimulation of striatal dopaminergic receptors.

Cocaine abusers have an overexpression of alpha-synuclein in dopamine neurons

Alpha-synuclein is a presynaptic protein that has been implicated as a possible causative agent in the pathogenesis of Parkinson's disease. The native protein is a major component of nigral Lewy bodies in Parkinson's disease, and full-length alpha-synuclein accumulates in Lewy neurites. Here we present evidence that alpha-synuclein levels are elevated in midbrain dopamine (DA) neurons of chronic cocaine abusers. Western blot and immunoautoradiographic studies were conducted on postmortem neuropathological specimens from cocaine users and age-matched drug-free control subjects. The results demonstrated that alpha-synuclein levels in the DA cell groups of the substantia nigra/ventral tegmental complex were elevated threefold in chronic cocaine users compared with normal age-matched subjects. The increased protein levels in chronic cocaine users were accompanied by changes in the expression of alpha-synuclein mRNA in the substantia nigra and ventral tegmental area. Although alpha-synuclein expression is prominent in the hippocampus, there was no increase in protein expression in this brain region. The levels of beta-synuclein, a possible negative regulator of alpha-synuclein, also were not affected by cocaine exposure. Alpha-synuclein protein levels were increased in the ventral tegmental area, but not the substantia nigra, in victims of excited cocaine delirium who experienced paranoia, marked agitation, and hyperthermia before death. The overexpression of alpha-synuclein may occur as a protective response to changes in DA turnover and increased oxidative stress resulting from cocaine abuse. However, the accumulation of alpha-synuclein protein with long-term cocaine abuse may put addicts at increased risk for developing the motor abnormalities of Parkinson's disease.

Neonatal administration of monosodium glutamate prevents the development of ethanol- but not psychostimulant-induced sensitization: a putative role of the arcuate nucleus

Lesions of the arcuate nucleus by monosodium glutamate, goldthioglucose and oestradiol valerate treatments are known to prevent the acute stimulating effect of ethanol in mice. On the basis of these results, the current study analysed whether a lesion of the arcuate nucleus by monosodium glutamate was able to block ethanol-induced locomotor sensitization. To produce the arcuate nucleus lesions, pups were injected with saline or monosodium glutamate (4 mg/g body weight) subcutaneously on 5 alternate days, starting on postnatal day one. Sensitization treatments began 10 weeks after the initial lesions. Sensitization training consisted of six trials on alternate days, in which groups of mice were treated with ethanol (2 g/kg) or saline, and then tested in an open-field for the induction of locomotor activity. The present study demonstrated that animals with monosodium glutamate-induced lesions did not develop locomotor sensitization to ethanol. Different groups of mice were used to assay blood ethanol levels and to evaluate the effect of arcuate nucleus lesions on psychostimulant-induced locomotor sensitization. Sensitization to cocaine or amphetamine was spared in monosodium glutamate-pre-treated animals, although the lesion of arcuate nucleus reduced the sensitivity of mice to cocaine. Our findings therefore suggest that the arcuate nucleus may be critical for the neuroadaptations that underlie the behavioural sensitization to ethanol, in contrast to those mediating psychostimulant-induced sensitization.

Cocaine-induced psychomotor activity is associated with its ability to induce c-fos mRNA expression in the subthalamic nucleus: effects of dose and repeated treatment

Factors that modulate the psychomotor activating effects of amphetamine and cocaine, such as environmental novelty and dose, also regulate the ability of these drugs to induce c-fos mRNA expression in the subthalamic nucleus (STN). We hypothesized therefore that engagement of the STN may be important for stimulant-induced psychomotor activation. To further test this hypothesis we examined whether repeated treatment with cocaine, which enhances its psychomotor activating effects (i.e. produces behavioural sensitization), also enhances its ability to induce c-fos expression in the STN. In addition, given that STN activity is thought to be influenced by preproenkephalin mRNA-containing (ENK+) neurons in the caudate-putamen, we also examined whether repeated cocaine treatment alters c-fos expression in ENK+ cells. We report that: (i) cocaine pretreatment enhances the ability of a cocaine challenge to induce c-fos mRNA expression in the STN, and this effect is most robust at challenge doses where behavioural sensitization is observed; (ii) the ability of cocaine to induce c-fos in the STN is independent of the ability of cocaine to engage ENK+ cells. These results support the idea that the STN is involved in stimulant-induced psychomotor activation and sensitization, but suggest that stimulant-induced engagement of the STN is not dependent on ENK+ cells in the caudate-putamen. These findings may have implications concerning the neurobiological mechanisms underlying the behavioural effects of psychostimulant drugs.

It could be habit forming: drugs of abuse and striatal synaptic plasticity

Drug addiction can take control of the brain and behavior, activating behavioral patterns that are directed excessively and compulsively toward drug usage. Such patterns often involve the development of repetitive and nearly automatic behaviors that we call habits. The striatum, a subcortical brain region important for proper motor function as well as for the formation of behavioral habits, is a major target for drugs of abuse. Here, we review recent studies of long-term synaptic plasticity in the striatum, emphasizing that drugs of abuse can exert pronounced influences on these processes, both in the striatum and in the dopaminergic midbrain. Synaptic plasticity in the ventral striatum appears to play a prominent role in early stages of drug use, whereas dopamine- and endocannabinoid-dependent synaptic plasticity in the dorsal striatum could contribute to the formation of persistent drug-related habits when casual drug use progresses towards compulsive drug use and addiction.

Focused motor stereotypies do not require enhanced activation of neurons in striosomes

Stereotypic motor behavior is a widespread phenomenon of many neurologic and psychiatric disorders. Studies on the mechanisms controlling motor stereotypies have focused on the role of dopamine in modulating the activity of basal ganglia neuronal circuits, and recent results demonstrated that stereotypic motor responses characteristic of psychomotor stimulant sensitization correlate with an enhanced activation of neurons located in striatal striosomes that substantially exceeds that of the surrounding matrix. The present study tested whether predominant striosomal activation is a general predictor for stereotypy. Wild-type and dopamine D(2) and D(3) receptor knockout mice were treated either three times with methamphetamine (METH; 3 x 5 mg/kg every 2 hours) or once with a full D(1) agonist. Depending on the genotype, both treatments elicit the same focused stereotypy (taffy pulling). Repeated METH-treatment elicits intense stereotypy in wild-type and D(3) mutants but not in D(2) single and D(2)/D(3) double mutants. The stereotypic response of wild-type and D(3) mutants correlates with a predominant activation of neurons located in striosomes. No striosomal predominance is detected in METH-treated D(2) single and D(2)/D(3) double mutants. In contrast, D(2) single and D(2)/D(3) double mutants exhibited the most severe stereotypic response to D(1)-agonist treatment. However, this treatment did not result in enhanced striosomal activation. Thus, whereas the expression of stereotypy in response to repeated METH treatment requires D(2) receptor expression, D(2) receptor expression diminishes stereotypic responses to an acute dose of a D(1) agonist. Enhanced striosomal activation, however, is a reliable indicator of D(1)- and D(2)-receptor coactivation but not a predictor for repetitive motor behavior in general.

Distinct effects of methamphetamine and cocaine on preprodynorphin messenger RNA in rat striatal patch and matrix

We and others previously reported that equimolar doses of methamphetamine and cocaine differentially increase preprodynorphin mRNA in striatum: methamphetamine causes a patchy increase, whereas cocaine produces a more homogenous one. The current study directly examined whether this effect reflects differential induction in the patch-matrix division of striatum, as identified by micro opioid receptor immunohistochemistry. In addition, we determined whether doses of cocaine (30 mg/kg) and methamphetamine (2 mg/kg) that produced equivalent increases in extracellular dopamine differentially affected preprodynorphin mRNA expression in striatum of male, Sprague-Dawley rats. In both experiments, methamphetamine and cocaine differentially affected preprodynorphin mRNA in striatum after 3 h. The high, equimolar dose of methamphetamine selectively increased preprodynorphin mRNA in the patch division of rostral striatum, whereas cocaine increased preprodynorphin mRNA throughout patch and matrix divisions of striatum. In contrast, a dose of methamphetamine (2.0 mg/kg) that caused an increase in extracellular dopamine similar to that produced by 30 mg/kg cocaine did not significantly affect preprodynorphin mRNA in any region of striatum. These data provide further evidence that cocaine and amphetamines exert distinct effects on the patch-matrix division of striatum and suggest further that the post-synaptic consequences of elevated extracellular dopamine produced by methamphetamine and cocaine are distinct.

Pelvic movements as rhythmic motor manifestation associated with restless legs syndrome

Video-polysomnographic monitoring of a patient with a 4-year history of an unpleasant restless sensation originating in his lower abdomen showed stereotyped, repetitive, rhythmic pelvic body movements resembling coital behaviour at the wake-sleep transition. We discuss the association between restless legs syndrome and rhythmic movement disorder as a particular manifestation of a spectrum of rhythmic sleep-related movement disorders.

Compartment-specific changes in striatal neuronal activity during expression of amphetamine sensitization are the result of drug hypersensitivity

Repeated exposure to drugs of abuse induces behavioural sensitization, i.e. a persistent hypersensitivity to the psychomotor stimulant effects of these drugs. This may be the result of increased responsiveness, to drugs, of mesostriatal dopamine systems and their projections, but it has also been suggested that acute and sensitized behavioural responses to psychostimulant drugs involve activation of distinct neuronal circuits. In order to distinguish between these possibilities, we studied amphetamine-induced c-fos immunoreactivity in subregions of rat striatum (patch and matrix compartments of caudate-putamen and nucleus accumbens core and shell) in drug-naive rats, as well as during long-term expression of amphetamine sensitization. We found that, in sensitized animals, amphetamine (1.0 mg/kg) evoked an increase in the ratio of c-fos-immunopositive cells in striatal patch and matrix compartments, suggesting a preferential involvement of striatal patches in the sensitized response to amphetamine. In drug-naive rats, amphetamine (0.5-5.0 mg/kg) dose-dependently increased c-fos expression in all striatal subregions. Remarkably, the highest dose of amphetamine also evoked an increase in patch : matrix ratio of c-fos immunoreactivity. In nucleus accumbens core and shell of amphetamine- and saline-pretreated animals, amphetamine (1.0 mg/kg) evoked comparable increases in c-fos expression. These data indicate that distinct striatal compartments display a differential sensitivity to amphetamine in both drug-naive and amphetamine-sensitized animals. In addition, they suggest that the shift in amphetamine-induced c-fos expression from striatal matrix to patches in sensitized animals is the consequence of a change in the sensitivity to amphetamine, rather than a long-term circuitry reorganization that is exclusive to the sensitized state.

Tourette's syndrome

As our knowledge of Gilles de la Tourette's syndrome increases, so does our appreciation for the pathogenic complexity of this disorder and the challenges associated with its treatment. Advances in the neurosciences have led to new models of pathogenesis, whereas clinical studies have reinvigorated early hypotheses. The interdependent roles of genes and environment in disease formation have yet to be fully elucidated. Results of epidemiological studies have prompted debate on how best to characterise and diagnose this disorder. Absence of ideal anti-tic drugs, combined with knowledge that uncomplicated cases of childhood Tourette's syndrome frequently have a favourable outcome, has led to striking changes in care and treatment of patients. This seminar focuses on these changing views and offers a new perspective on our understanding of the pathogenesis of Tourette's syndrome and on principles for treatment of patients with this disorder.

Locomotor sensitization to cocaine is associated with increased Fos expression in the accumbens, but not in the caudate

Behavioral sensitization following repeated intermittent cocaine administrations is thought to involve alterations in cocaine regulation of neural activity within the accumbens and caudate brain regions. Although Fos immunohistochemistry and c-fos in situ hybridization have frequently been used to assess changes in cocaine-induced neural activity following prior cocaine exposure, these techniques have rarely been used to examine neural activity in the accumbens of behaviorally sensitized animals. In the present experiment, we compared the ability of increasing doses of cocaine to induce Fos in the accumbens and caudate of rats following a treatment procedure (7 once daily injections of 15 mg/kg of cocaine or the saline vehicle) shown to produce robust and persistent (1 week) locomotor sensitization. In sensitized animals, there was a leftward shift in the dose-response curve for cocaine induction of Fos in the accumbens, but not in the caudate. These results provide the first parametric evidence for sensitization of cocaine-induced Fos expression in the accumbens.

Early motor dysfunction and striosomal distribution of huntingtin microaggregates in Huntington's disease knock-in mice

Huntington's disease (HD) is characterized by a progressive loss of neurons in the striatum and cerebral cortex and is caused by a CAG repeat expansion in the gene encoding huntingtin. Mice with the mutation inserted into their own huntingtin gene (knock-in mice) are, genetically, the best models of the human disease. Here we show for the first time that knock-in mice with 94 CAG repeats develop a robust and early motor phenotype at 2 months of age, characterized by increased rearing at night. This initial increase in repetitive movements was followed by decreased locomotion at 4 and 6 months, despite a normal life span. The decrease in striatal enkephalin mRNA that is known to occur at 4 months was not present at 2 months, when increased rearing was observed. Both the hyperactive and hypoactive phases of motor dysfunction preceded the detection of nuclear microaggregates of mutated huntingtin in striatal neurons. Nuclear microaggregates, defined as small huntingtin-positive punctas detected by light microscopy, were very rare at 4 months but became widely distributed in striatal neurons at 6 months. Nuclear inclusions did not appear until 18 months. When present, nuclear microaggregates predominated in the striosomal compartment of the striatum, providing a possible explanation for the different neuronal vulnerability of striatal compartments observed in humans. The early motor phenotype observed in the knock-in mouse is reminiscent of repetitive movements often observed in early HD and provides a novel opportunity to assess the ability of therapies to prevent the initial effects of the mutation in vivo.

Concurrent activation of dopamine D1 and D2 receptors is required to evoke neural and behavioral phenotypes of cocaine sensitization

Repeated exposure to psychomotor stimulants produces a striking behavioral syndrome involving repetitive, stereotypic behaviors that occur if an additional exposure to the stimulant is experienced. The same stimulant exposure produces specific alterations in gene expression patterns in the striatum. To identify the dopamine receptor subtypes required for the parallel expression of these acquired neural and behavioral responses, we treated rats with different D1-class and D2-class dopamine receptor agonists and compared the responses of drug-naive rats with those of rats given previous intermittent treatment with cocaine. In rats exposed to repeated cocaine treatment, the effects of a subsequent challenge treatment with either a D1-class agonist (SKF 81297) or a D2-class agonist (quinpirole) were not significantly different from those observed in drug-naive animals: the drugs administered singly did not induce robust stereotyped motor behaviors nor produce significantly striosome-predominant expression of early genes in the striatum. In contrast, challenge treatment with the D1-class and D2-class agonists in combination led to marked and correlated increases in stereotypy and striosome-predominant gene expression in the striatum. Thus, immediately after repeated psychomotor stimulant exposure, only the concurrent activation of D1 and D2 receptor subclasses evoked expression of the neural and behavioral phenotypes acquired through repeated cocaine exposure. These findings suggest that D1-D2 dopamine receptor synergisms underlie the coordinate expression of both network-level changes in basal ganglia activation patterns and the repetitive and stereotypic motor response patterns characteristic of psychomotor stimulant sensitization.

Local circuit neurons in the striatum regulate neural and behavioral responses to dopaminergic stimulation

Interneurons are critical for shaping neuronal circuit activity in many parts of the central nervous system. To study interneuron function in the basal ganglia, we tested and characterized an NK-1 receptor-based method for targeted ablation of specific classes of interneuron in the striatum. Our findings demonstrate that the neurotoxin SP-PE35, a substance P-Pseudomonas exotoxin conjugate, selectively targets striatal cholinergic and nitric oxide synthase/somatostatinergic interneurons when injected locally into the striatum. The effects of this selective cell targeting encompassed alterations in both behavioral and neural responses to dopaminergic stimulation, including altered patterns of early-gene response in striosomes and matrix. We conclude that NK-1-bearing local circuit neurons of the striatum regulate the differential responses of striatal projection neurons to dopamine-mediated signaling.

Motor and associative deficits in D2 dopamine receptor knockout mice

Behavioral abnormalities produced by D2 dopamine receptor gene deletion in mice have been attributed either to resulting Parkinson-like features (i.e. response slowing and response initiation difficulties) or to behavioral deficits contributed by alleles of the originating 129Sv strain. Three strategies were used to address these conflicting hypotheses: (1) we used mice congenic at n10 backcross into the C57BL/6 line to minimize the 129Sv contribution; (2) we compared mice that were wild-type (+/+), heterozygous (+/-), or homozygous (-/-) for the D2 gene with the two most relevant inbred lines (129Sv and C57BL/6) and (3) we used both conventional and novel behavioral assessment methods. Behavioral attributes were expressed in terms of locomotor activity, wall rearing, rotarod performance, operant response acquisition, operant response performance, lick dynamics (force, rhythm), grip strength, and tremor in response to harmaline challenge. Results showed that, compared to controls, the -/- mice exhibited longer duration wall rears, retarded operant response acquisition, increased latencies to move from the operandum to the reward well, and exaggerated response to harmaline. Age was investigated as a variable (10-11 weeks versus 41-44 weeks of age) in the locomotor activity and wall rear assessments. A gene dosage effect (deficits in the +/- mice) on these two variables became apparent in the older mice. Taken together, the results showed that mice without the D2 gene exhibited Parkinson-like behavioral features that were not easily attributed to alleles contributed by the 129Sv strain, but were consistent with basal ganglia dysfunction.

Environmental enrichment: effects on stereotyped behavior and regional neuronal metabolic activity

The present study evaluated whether environmental enrichment-related effects on the development of stereotyped behavior in deer mice were associated with alterations in neuronal metabolic activity. Deer mice were reared under either enriched or standard housing conditions for 60 days following weaning. All mice were then placed in automated photocell detectors and classified as either stereotypic or non-stereotypic. Neuronal metabolic activity was then assessed using cytochrome oxidase (CO) histochemistry. The results demonstrated that environmental enrichment significantly increased neuronal metabolic activity in the motor cortex. Furthermore, non-stereotypic mice exhibited significantly more CO activity than stereotypic mice in the cortex, striatum, nucleus accumbens, thalamus, hippocampus and amygdala. This latter effect was due to the enriched mice as evidenced by a significant interaction between housing condition and behavioral status in the cortex, striatum, nucleus accumbens, thalamus and hippocampus. Thus, the observed increase in CO activity reflected increased neuronal metabolic activity in non-stereotypic enriched mice relative to stereotypic enriched mice. These results suggest that, in a developmental model of spontaneous stereotypy, the enrichment-related prevention of stereotyped behavior is associated with increased CO activity.

Differential metabolic activity in the striosome and matrix compartments of the rat striatum during natural behaviors

The striosome and matrix compartments of the striatum are clearly identified by their neurochemical expression patterns and anatomical connections. To determine whether these compartments are distinguishable functionally, we used [14C]deoxyglucose metabolic mapping in the rat and tested whether neutral behavioral states (free movement, gentle restraint, and focal tactile stimulation under gentle restraint) were associated with regions of high metabolic activity in the matrix, in striosomes, or in both. We identified metabolic peaks in the striatum by means of image analysis, striosome-matrix boundaries by [3H]naloxone binding, and primary somatosensory corticostriatal input clusters by injections of anterograde tracer into electrophysiologically identified sites in SI. Peak metabolic activity was primarily confined to the matrix compartment under each behavioral condition. These findings show that during relatively neutral behavioral conditions the balance of activity between the two compartments favors the matrix and suggest that this balance is present in the striatum as part of normal behavior and processing of afferent activity.

Differential effects of typical and atypical antipsychotic drugs on striosome and matrix compartments of the striatum

Administration of typical antipsychotic drugs (APDs) is often accompanied by extrapyramidal side-effects (EPS). Treatment with atypical APDs has a lower incidence of motor side-effects and atypical APDs are superior to typical APDs in treating the negative symptoms of schizophrenia. Although typical APDs strongly induce the immediate-early gene c-fos in the striatum while atypical APDs do so only weakly, it is possible that the effects of atypical APDs are more pronounced within certain regions of the striatum. The striatum contains two histochemically defined compartments, the striosome (patch) and the matrix. These compartments have been well characterized anatomically but their functional attributes are unclear. We therefore examined the effects of typical and atypical APDs on Fos expression in the striosome and matrix of the rat. Typical and atypical APDs were distinguished by the pattern of striatal compartmental activation they induced: the striosome : matrix ratio of Fos-li neurons was greater in rats treated with atypical APDs. Pretreating animals with selective antagonists of receptors that atypical APDs target with high affinity did not increase the striosome : matrix Fos ratio of typical APD-treated rats and thus did not mimic the ratio seen in response to atypical APDs. However, pretreatment with the atypical APD clozapine did recapitulate the characteristic compartmental Fos pattern seen in response to typical APDs. These data suggest that some characteristics of atypical APDs, such as the lower EPS liability and greater reduction of negative symptoms, may be linked to the coordinate regulation of the striatal striosome and matrix.

Diurnal variation of c-Fos expression in subdivisions of the dorsal raphe nucleus of the Mongolian gerbil (Meriones unguiculatus)

Recent studies suggest that the dorsal raphe nucleus (DRN) of the brainstem contains several subdivisions that differ both anatomically and neurochemically. The present study examined whether variation of c-Fos expression across the 24-hour light-dark cycle may also be different in these subdivisions. Animals were kept on a 12:12 light-dark cycle, were perfused at seven different time points, and brain sections were processed by using c-Fos immunocytochemistry. At all coronal levels of the DRN, c-Fos expression reached a peak 1 hour after the light-dark transition (lights-off) and reached its lowest levels in the middle of the light period. In contrast to the light-dark transition, c-Fos levels did not change significantly after the dark-light transition (lights-on). One-way analysis of variance (ANOVA) revealed that the diurnal variation of c-Fos expression was highly significant in the caudal ventral DRN. Similar variation in c-Fos expression also was observed in the other DRN subdivisions, but this variation appeared to gradually diminish in the caudal-to-rostral and ventromedial-to-dorsomedial directions. Double-label immunocytochemistry revealed that, 1 hour after lights-off, only 11% of c-Fos-positive neurons in the caudal ventral DRN were serotonin (5-HT)-immunoreactive. These results suggest that DRN subdivisions may differ functionally with regard to the diurnal cycle, and that these differences may be reflected in the activity of nonserotonergic cells in the DRN.

Antibodies against neural, nuclear, cytoskeletal, and streptococcal epitopes in children and adults with Tourette's syndrome, Sydenham's chorea, and autoimmune disorders

BACKGROUND

Some cases of Tourette's syndrome (TS) are hypothesized to be caused by autoantibodies that develop in response to a preceding group A beta hemolytic streptococcal infection.

METHODS

To test this hypothesis, we looked for the presence ot total and IgG antibodies against neural, nuclear, cytoskeletal and streptococcal epitopes using indirect immunofluorescent assays and Western blot techniques in three patient groups: TS (n = 81), SC (n = 27), and a group of autoimmune disorders (n = 52) and in normal controls (n = 67). Subjects were ranked after titrations of autoantibodies from 0 to 227 according to their level of immunoreactivity.

RESULTS

TS patients had a significantly higher mean rank for total antineural and antinuclear antibodies, as well as antistreptolysin O titers. However, among children and adolescents, only the total antinuclear antibodies were increased in TS patients compared to age matched controls. Compared to SC patients, TS patients had a significantly lower mean rank for total and IgG class antineural antibodies, significantly lower IgG class anticytoskeletal antibodies, and a significantly higher rank for total antinuclear antibodies. Compared to a mixed group of autoimmune disorders, the TS patients had a significantly lower mean rank for total and IgG class antineural antibodies, total and IgG class antinuclear antibodies, IgG class anticytoskeletal antibodies, and a significantly higher rank for antistreptococcal antibodies.

CONCLUSIONS

TS patients had significantly higher levels of total antineural and antinuclear antibodies than did controls. Their relation to IgG class antineural and antinuclear antibodies, markers for prior streptococcal infection, and other clinical characteristics, especially chronological age, was equivocal.

Induction of stereotypy in dopamine-deficient mice requires striatal D1 receptor activation

Motor stereotypies are abnormally repetitive behaviors that can develop with excessive dopaminergic stimulation and are features of some neurologic disorders. To investigate the mechanisms required for the induction of stereotypy, we examined the responses of dopamine-deficient (DD) mice to increasing doses of the dopamine precursor L-DOPA. DD mice lack the ability to synthesize dopamine (DA) specifically in dopaminergic neurons yet exhibit robust hyperlocomotion relative to wild-type (WT) mice when treated with L-DOPA, which restores striatal DA tissue content to approximately 10% of WT levels. To further elevate brain DA content in DD mice, we administered the peripheral L-amino acid decarboxylase inhibitor carbidopa along with L-DOPA (C/l-DOPA). When striatal DA levels reached >50% of WT levels, a transition from hyperlocomotion to intense, focused stereotypy was observed that was correlated with an induction of c-fos mRNA in the ventrolateral and central striatum as well as the somatosensory cortex. WT mice were unaffected by C/L-DOPA treatments. A D1, but not a D2, receptor antagonist attenuated both the C/L-DOPA-induced stereotypy and the c-fos induction. Consistent with these results, stereotypy could be induced in DD mice by a D1, but not by a D2, receptor agonist, with neither agonist inducing stereotypy in WT mice. Intrastriatal injection of a D1 receptor antagonist ameliorated the stereotypy and c-fos induction by C/L-DOPA. These results indicate that activation of D1 receptors on a specific population of striatal neurons is required for the induction of stereotypy in DD mice.

Dopamine receptor functions: lessons from knockout mice [corrected]

In the past few years, a number of laboratories have used gene targeting via homologous recombination to generate mice deficient for key molecules involved in dopaminergic (DAergic) transmission. This tremendous effort has resulted in the successful generation and characterization of mice deficient for the neurotransmitter DA, the main terminator of DAergic neurotransmission (the DA transporter), and all five subtypes of DA receptors. This review summarizes the results from studies of the various DA receptor knockout mice and of mice deficient in proteins that mediate DA receptor signaling. It focuses on a comparison of the locomotor phenotypes and responses to drugs of abuse (psychostimulants), and reviews the results of anatomic studies examining the morphological and neurochemical differentiation of the striatum in these mutants. Moreover, an overview of recently published results highlighting the physiological relevance of the interaction between different DA receptors and between DA receptors and other neurotransmitter receptors in the modulation of behavioral and molecular responses to DAergic stimulation is presented. Finally, in view of the recently discovered heteroligomeric assemblies of neurotransmitter receptors that involve DA receptor subtypes, the potential value of knockout mice as a tool for testing the in vivo significance of these heteroligomeric receptors is discussed.

A force-plate actometer for quantitating rodent behaviors: illustrative data on locomotion, rotation, spatial patterning, stereotypies, and tremor

This report describes a new kind of actometer for recording the behavior of rodents or other small animals. The instrument, a force-plate actometer, uses a stiff, low-mass horizontal plate coupled to four supporting force transducers positioned at the corners of the plate. When an animal moves on the plate, its movements are sensed by the transducers whose signals are processed by computer to yield measurements of a wide range of behaviors or behavioral attributes, such as locomotor activity, rotation around the center, whole-body tremor, and amphetamine-induced stereotypies. Spatial resolution is less than 1 mm, and temporal resolution is 0.02 s. Sample data were presented comparing the locomotor activity of CD-1, BALB/c, and C57BL/6 mice before and after treatment with D-amphetamine sulfate. Rotational behavior was recorded in an amphetamine-treated rat that had sustained a unilateral 6-hydroxydopamine-induced lesion of the nigrostriatal system. In the C57BL/6 mouse, harmaline-induced tremor was quantified. With rats as subjects, the force-plate actometer was used to quantify amphetamine-induced stereotypies, to demonstrate the development of sensitization to amphetamine's effects, and to quantitate the consistent 11-12 Hz rhythmicities that underlie the sterotypies. The performance of the force-plate actometer was compared with that of a variety of instruments reported in the literature on behavioral instrumentation. Finally, potential applications in neuroscience research other than those illustrated in this report were discussed.

The neurotensin antagonist SR 48692 attenuates haloperidol-induced striatal Fos expression in the rat

Neurotensin interacts with central dopamine systems and has been suggested to exert antipsychotic drug-like actions. Antipsychotic drugs such as haloperidol induce striatal immediate-early gene expression. In order to study neurotensin's role in antipsychotic drug actions, rats were pretreated with the neurotensin antagonist SR 48692 and then injected with haloperidol. SR 48692 dose-dependently decreased haloperidol-elicited immediate-early gene expression in the dorsolateral and central striatum but not other striatal areas. SR 48692 reduced Fos expression in the striatal patch (striosome) and matrix compartments, with a significantly greater effect in the patch. These data suggest that neurotensin may play a role in the actions of haloperidol. In view of proposed functional roles of the striatal patch and matrix, we suggest that neurotensin may be important in the therapeutic rather than side effects of antipsychotic drugs.

Involvement of the extracellular signal-regulated kinase cascade for cocaine-rewarding properties

A central feature of drugs of abuse is to induce gene expression in discrete brain structures that are critically involved in behavioral responses related to addictive processes. Although extracellular signal-regulated kinase (ERK) has been implicated in several neurobiological processes, including neuronal plasticity, its role in drug addiction remains poorly understood. This study was designed to analyze the activation of ERK by cocaine, its involvement in cocaine-induced early and long-term behavioral effects, as well as in gene expression. We show, by immunocytochemistry, that acute cocaine administration activates ERK throughout the striatum, rapidly but transiently. This activation was blocked when SCH 23390 [a specific dopamine (DA)-D1 antagonist] but not raclopride (a DA-D2 antagonist) was injected before cocaine. Glutamate receptors of NMDA subtypes also participated in ERK activation, as shown after injection of the NMDA receptor antagonist MK 801. The systemic injection of SL327, a selective inhibitor of the ERK kinase MEK, before cocaine, abolished the cocaine-induced ERK activation and decreased cocaine-induced hyperlocomotion, indicating a role of this pathway in events underlying early behavioral responses. Moreover, the rewarding effects of cocaine were abolished by SL327 in the place-conditioning paradigm. Because SL327 antagonized cocaine-induced c-fos expression and Elk-1 hyperphosphorylation, we suggest that the ERK intracellular signaling cascade is also involved in the prime burst of gene expression underlying long-term behavioral changes induced by cocaine. Altogether, these results reveal a new mechanism to explain behavioral responses of cocaine related to its addictive properties.

Levodopa-induced dyskinesias and dopamine-dependent stereotypies: a new hypothesis

The basal ganglia are thought to modulate the release or inhibition of movements by way of direct and indirect pathways that act as a push-pull system of cortico-basal ganglia circuits. Here we suggest a three-pathway model of the basal ganglia that takes into consideration the fundamental division of the striatum into striosomes and extrastriosomal matrix. We suggest that, in addition to the balance between direct and indirect pathways on which normal release of individual movements depends, the balance of activity between these matrix-based pathways and the striosomal pathway regulates the frequency of release of given behavioral sequences and, thus, modulates behavioral focus. Differential plasticity in these compartmentally organized circuits might contribute to the development of L-dopa-induced dyskinesias under parkinsonian conditions and dopamine-receptor-agonist induced stereotypies under normal conditions.