Acrolein scavenger dimercaprol offers neuroprotection in an animal model of Parkinson's disease: implication of acrolein and TRPA1

BACKGROUND

The mechanisms underlying lesions of dopaminergic (DA) neurons, an essential pathology of Parkinson's disease (PD), are largely unknown, although oxidative stress is recognized as a key factor. We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in PD pathology, and that acrolein scavenger hydralazine can reduce the elevated acrolein, mitigate DA neuron death, and alleviate motor deficits in a 6-hydroxydopamine (6-OHDA) rat model. As such, we hypothesize that a structurally distinct acrolein scavenger, dimercaprol (DP), can also offer neuroprotection and behavioral benefits.

METHODS

DP was used to lower the elevated levels of acrolein in the basal ganglia of 6-OHDA rats. The acrolein levels and related pathologies were measured by immunohistochemistry. Locomotor and behavioral effects of 6-OHDA injections and DP treatment were examined using the open field test and rotarod test. Pain was assessed using mechanical allodynia, cold hypersensitivity, and plantar tests. Finally, the effects of DP were assessed in vitro on SK-N-SH dopaminergic cells exposed to acrolein.

RESULTS

DP reduced acrolein and reversed the upregulation of pain-sensing transient receptor potential ankyrin 1 (TRPA1) channels in the substantia nigra, striatum, and cortex. DP also mitigated both motor and sensory deficits typical of PD. In addition, DP lowered acrolein and protected DA-like cells in vitro. Acrolein's ability to upregulate TRPA1 was also verified in vitro using cell lines.

CONCLUSIONS

These results further elucidated the acrolein-mediated pathogenesis and reinforced the critical role of acrolein in PD while providing strong arguments for anti-acrolein treatments as a novel and feasible strategy to combat neurodegeneration in PD. Considering the extensive involvement of acrolein in various nervous system illnesses and beyond, anti-acrolein strategies may have wide applications and broad impacts on human health.

In vivo imaging of synaptic SV2A protein density in healthy and striatal-lesioned rats with [11C]UCB-J PET

The number of functionally active synapses provides a measure of neural integrity, with reductions observed in neurodegenerative disorders. [11C]UCB-J binds to synaptic vesicle 2A (SV2A) transmembrane protein located in secretory vesicles. We aimed to assess [11C]UCB-J PET as an in vivo biomarker of regional cerebral synaptic SV2A density in rat lesion models of neurodegeneration. Healthy anesthetized rats had [11C]UCB-J PET and arterial blood sampling. We compared different models describing [11C]UCB-J brain uptake kinetics to determine its regional distribution. Blocking studies were performed with levetiracetam (LEV), an antiepileptic SV2A antagonist. Tracer binding was measured in rodent unilateral acute lesion models of Parkinsonism and Huntington's disease, induced with 6-hydroxydopamine (6-OHDA) and quinolinic acid (QA), respectively. [3H]UCB-J autoradiography was performed in postmortem tissue. Rat brain showed high and fast [11C]UCB-J uptake and washout with up to 80% blockade by LEV. [11C]UCB-J PET showed a 6.2% decrease in ipsilateral striatal SV2A binding after 6-OHDA and 39.3% and 55.1% decreases after moderate and high dose QA confirmed by autoradiography. In conclusion, [11C]UCB-J PET provides a good in vivo marker of synaptic SV2A density which can potentially be followed longitudinally along with synaptic responses to putative neuroprotective agents in models of neurodegeneration.

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

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by progressive loss of nigrostriatal dopaminergic neurons leading to dopamine depletion and problems of movement, emotions, and cognition. While the pathogenesis of PD is not clear, damage of dopaminergic neurons by oxygen-derived free radicals is considered an important contributing mechanism. This study aimed to evaluate the role of treadmill exercise in male Wister rats as a single treatment and as an aid-therapy with L-dopa for rotenone-induced PD. To study the role of the Nrf2- ARE pathway as a mechanism involved in exercise-associated improvement in rotenone-induced PD in rats.

METHOD

Animals were divided into 5 groups, (Control, rotenone, rotenone\exercise, rotenone\L-dopa, and rotenone\exercise\L-dopa (combination)groups). After the PD induction, rats in the rotenone\exercise and combination groups were daily treadmill exercised for 4 weeks.

RESULTS

Treadmill exercise significantly improved behavioral and motor aspects of rotenone-induced PD. When treadmill exercise was introduced as a single intervention, it amended most behavioral aspects of PD, gait fully corrected, short-term memory, and motor coordination. Where L-dopa corrected locomotor activity and motor coordination but failed to improve short-term memory and only partially corrected the gait of rotenone-treated rats. When treadmill exercise was combined with L-dopa, all features of PD were corrected. It was found that exercise upregulated some of its associative genes to Nrf2 pathways such as TFAM, Nrf2 and NQO.1 mRNA expression.

CONCLUSION

This study suggests that forced exercise improved parkinsonian like features by activating the Nrf2 pathway.

Chrysin protects against behavioral, cognitive and neurochemical alterations in a 6-hydroxydopamine model of Parkinson's disease

Parkinson's disease (PD) is an age-related neurodegenerative disorder that severely affects quality of life of patients and their families. The flavonoid chrysin (5,7-dihydroxylflavone) is a naturally occurring flavone with several pharmacological activities, including anti-inflammatory and anti-oxidative. We investigated the effects of a 28-day chrysin treatment (10 mg/kg/day, i.g.) on a model of PD induced by 6-OHDA in aged (20-month old) mice. We found a protective effect of chrysin on behavioral and cognitive alterations (rotational behavior, passive avoidance and Barnes maze tests), nitric oxide synthesis (NOx), lipid peroxidation (HNE), glutathione levels (GSH), reactive species levels (RS), neuroinflammation (interleukin-1 beta - IL-1β and tumor necrosis factor alpha - TNF-α), Na⁺, K⁺-ATPase and nicotinamide adenine dinucleotide phosphate oxidase activity (NADPH oxidase) activities. In addition, chrysin protected against changes in striatal dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. In conclusion, chrysin improved several behavioral, cognitive and neurochemical parameters in a relevant preclinical model of PD in aged mice.

Unilateral Lesion of Dopamine Neurons Induces Grooming Asymmetry in the Mouse

Grooming behaviour is the most common innate behaviour in animals. In rodents, it consists of sequences of movements organized in four phases, executed symmetrically on both sides of the animal and creating a syntactic chain of behavioural events. The grooming syntax can be altered by stress and novelty, as well as by several mutations and brain lesions. Grooming behaviour is known to be affected by alterations of the dopamine system, including dopamine receptor modulation, dopamine alteration in genetically modified animals, and after brain lesion. While a lot is known about the initiation and syntactic modifications of this refined sequence of movements, effects of unilateral lesion of dopamine neurons are unclear particularly regarding the symmetry of syntactic chains. In the present work we studied grooming in mice unilaterally lesioned in the medial forebrain bundle by 6-hydroxydopamine. We found a reduction in completion of grooming bouts, associated with reduction in number of transitions between grooming phases. The data also revealed the development of asymmetry in grooming behaviour, with reduced tendency to groom the contralateral side to the lesion. Symmetry was recovered following treatment with L-DOPA. Thus, the present work shows that unilateral lesion of dopamine neurons reduces self-grooming behaviour by affecting duration and numbers of events. It produces premature discontinuation of grooming chains but the sequence syntax remains correct. This deficient grooming could be considered as an intrinsic symptom of Parkinson’s disease in animal models and could present some similarities with abnormalities of motor movement sequencing seen in patients. Our study also suggests grooming analysis as an additional method to screen parkinsonism in animal models.

Reversal of haloperidol induced motor deficits in rats exposed to repeated immobilization stress

Stress is defined as a non specific response of body to any physiological and psychological demand. Preclinical studies have shown that an uncontrollable stress condition produces neurochemical and behavioral deficits. The present study was conducted to test the hypothesis that a decrease in the responsiveness of somatodendritic 5-hydroxytryptamine (5-HT)-1A receptors following adaptation to stress could attenuate haloperidol induced acute parkinsonian like effect. Results showed that single exposure (2h) to immobilization stress markedly decreased food intake, growth rate and locomotor activity but these stress-induced behavioral deficits were not observed following repeated (2h/day for 5 days) exposure of immobilization stress suggesting behavioral tolerance occurs to similar stress. An important finding of present study is a reversal of haloperidol-induced motor deficits in animals exposed to repeated immobilization stress than respective control animals. It is suggested that stress induced possible desensitization of somatodendritic 5-HT-1A as well as 5-HT-2C receptors could release dopamine system from the inhibitory influence of serotonin. On the other hand, an increase in the effectiveness of postsynaptic 5-HT-1A receptors elicits a direct stimulatory influence on the activity of dopaminergic neuron and is possibly involved in the reversal of haloperidol-induced parkinsonian like symptoms in repeatedly immobilized rats.

Oral administration of haloperidol at clinically recommended doses elicits smaller parkinsonian effects but more tardive dyskinesia in rats

The present study was designed to monitor extrapyramidal symptoms (EPS) elicited by the oral administration of haloperidol at clinically recommended doses and to compare it with EPS produced when the drug is injected intraperitoneally at doses used in animal research. Rats injected with haloperidol at a dose of 1 mg/kg daily for 5 weeks exhibited akinesia in an open field and impaired motor coordination. Effects of the drug on motor coordination but not on open field akinesia were attenuated gradually from 2-5 weeks of treatment. Oral administration of haloperidol in drinking water at clinically recommended dose exhibited decreased exploratory activity without producing akinesia. Motor coordination was impaired maximally after 3 weeks and tolerance was developed in the drug induced motor impairment after 5 weeks of treatment. Intensity of vacuous chewing movements (VCMs) and tardive VCMs was greater by oral administration than intraperitoneal injections of haloperidol. The present results showed that oral administration of haloperidol expected to produce sustained effect may result in tolerance in acute parkinsonian like effects but more intensity of tardive dyskinesia. We suggest that drugs which may helpful in alleviating tardive dyskinesia may be more useful if person is on oral drug therapy.

Cognitive dysfunction in idiopathic and vascular parkinsonism

AIM

To evaluate the characteristics of cognitive disturbances in patients with parkinsonism and to point out the need of following up those changes by highly specific tests.

METHODS

The first group consisted of patients with Parkinson's disease, and the second group of patients with vascular parkinsonism. The neuropsychological assessments were performed with mini mental state examination (MMSE) and the Raven progressive matrices.

RESULTS

The MMSE has shown a higher percentage of patients with vascular parkinsonism who had dementia. For evaluating the nonverbal possibilities, the aim of understanding the complex situation and the visual perception, the Raven's progressive matrices were used showing that in both groups of the patients those specific changes were highly present.

CONCLUSIONS

It was concluded that MMSE and Raven's progressive matrices have to be obtained in early phases of the disease, and have to be repeated to follow up the therapy effect.

Sleep alterations in an environmental neurotoxin-induced model of parkinsonism

Parkinson's disease (PD) is classically defined as a motor disorder resulting from decreased dopamine production in the basal ganglia circuit. In an attempt to better diagnose and treat PD before the onset of severe motor dysfunction, recent attention has focused on the early, non-motor symptoms, which include but are not limited to sleep disorders such as excessive daytime sleepiness (EDS) and REM behavioral disorder (RBD). However, few animal models have been able to replicate both the motor and non-motor symptoms of PD. Here, we present a progressive rat model of parkinsonism that displays disturbances in sleep/wake patterns. Epidemiological studies elucidated a link between the Guamanian variant of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) and the consumption of flour made from the washed seeds of the plant Cycas micronesica (cycad). Our study examined the effects of prolonged cycad consumption on sleep/wake activity in male, Sprague-Dawley rats. Cycad-fed rats exhibited an increase in length and/or number of bouts of rapid eye movement (REM) sleep and Non-REM (NREM) sleep at the expense of wakefulness during the active period when compared to control rats. This hypersomnolent behavior suggests an inability to maintain arousal. In addition, cycad-fed rats had significantly fewer orexin cells in the hypothalamus. Our results reveal a novel rodent model of parkinsonism that includes an EDS-like syndrome that may be associated with a dysregulation of orexin neurons. Further characterization of this early, non-motor symptom, may provide potential therapeutic interventions in the treatment of PD.

Noggin enhances dopamine neuron production from human embryonic stem cells and improves behavioral outcome after transplantation into Parkinsonian rats

Symptoms of Parkinson's disease have been improved by transplantation of fetal dopamine neurons recovered from aborted fetal tissue, but tissue recovery is difficult. Human embryonic stem cells may provide unlimited cells for transplantation if they can be converted to dopamine neurons and survive transplantation into brain. We have found that the bone morphogenic protein antagonist Noggin increased the number of dopamine neurons generated in vitro from human and mouse embryonic stem cells differentiated on mouse PA6 stromal cells. Noggin effects were seen with either early (for mouse, days 0-7, and for human, days 0-9) or continuous treatment. After transplant into cyclosporin-immunosuppressed rats, human dopamine neurons improved apomorphine circling in direct relation to the number of surviving dopamine neurons, which was fivefold greater after Noggin treatment than with control human embryonic stem cell transplants differentiated only on PA6 cells. We conclude that Noggin promotes dopamine neuron differentiation and survival from human and mouse embryonic stem cells. Disclosure of potential conflicts of interest is found at the end of this article.

Identification of differentially expressed proteins in striatum of maneb-and paraquat-induced Parkinson's disease phenotype in mouse

Behavioral, phenotypic and biochemical changes induced by maneb+paraquat (MB+PQ) in experimental animals have shown their role in the etiologies of Parkinson's disease (PD); however, MB+PQ induced neuronal damage at genome and proteome level have not yet been clearly understood. The present study was undertaken to investigate the differential protein expression patterns in control and MB+PQ treated mouse striatum and to identify differentially expressed proteins. Animals were treated with and without MB+PQ, twice a week for three, six and nine weeks and proteome profiles of striatum were compared. Three differentially expressed proteins were identified as complexin-I, alpha-enolase and glia maturation factor-beta (GMF-beta) using 2D-PAGE and mass spectrometry. The differential expressions were also confirmed at transcription level by semi-quantitative RT-PCR. The results suggest the involvement of complexin-I, alpha-enolase and GMF-beta in MB+PQ induced PD phenotype in mouse.

Treadmill exercise suppresses nigrostriatal dopaminergic neuronal loss in 6-hydroxydopamine-induced Parkinson's rats

In Parkinson's disease, the progressive loss of dopaminergic neurons in the pars compacta of the substantia nigra leads to debilitating motor dysfunction. In the present study, we investigated the effects of treadmill exercise on the dopaminergic neuronal cell death in the substantia nigra and on the dopaminergic fiber loss in the striatum of Parkinson's rats. Parkinson's rats were made by injecting 6-hydroxydopamine into the striatum with using a stereotaxic instrument. The rats in the exercise groups were put on the treadmill to run for 30 min once a day for 14 consecutive days after 6-hydroxydopamine administration into the striatum. Two weeks after the intrastriatal injection of 6-hydroxydopamine, the rats without treadmill exercise displayed rotational asymmetry following injection of apomorphine (0.5 mg/kg, s.c.). In contrast, the rats undergoing treadmill exercise showed a significant reduction of rotational asymmetry. Analysis via immunohistochemistry for the tyrosine hydroxylase expression revealed a substantial loss of cell bodies in the substantia nigra and their projected fibers in the striatum ipsilateral to the lesion following 6-hydroxydapamine injection into the striatum. However, treadmill running enhanced the survival of dopaminergic neurons in the substantia nigra and also their fibers projecting into the striatum. The results of the present study show that treadmill exercise may provide therapeutic value for the treatment of Parkinson's disease patients.

Behavioral recovery following sub-chronic paeoniflorin administration in the striatal 6-OHDA lesion rodent model of Parkinson's disease

In the present studies, the effect of paeoniflorin (PF), one of the main compounds extracted from Paeoniae radix, in alleviating the neurological impairment following unilateral striatal 6-hydroxydopamine (6-OHDA) lesion was examined in Sprague-Dawley rats. Sub-chronic PF (2.5, 5 and 10 mg/kg, s.c., twice daily for 11 days) administration dose-dependently reduced apomorphine (APO)-induced rotation, suggesting that PF had an ameliorative effect on the 6-OHDA-induced neurological impairment. Notably, PF had no direct action on dopamine D(1) receptor or dopamine D(2) receptor indicated by the competitive binding experiments. These results suggest that PF, an active component of Paeoniae radix, might provide an opportunity to introduce a non-dopaminergic management of Parkinson's disease.

Intrastriatal administration of erythropoietin protects dopaminergic neurons and improves neurobehavioral outcome in a rat model of Parkinson’s disease

Erythropoietin (EPO), a hematopoietic cytokine, has recently been demonstrated to protect nigral dopaminergic neurons in a mouse model of Parkinson's disease (PD). In the present study, we tested the hypothesis that recombinant human erythropoietin (rhEPO) could protect dopaminergic neurons and improve neurobehavioral outcome in a rat model of PD. rhEPO (20 units in 2 microl of vehicle) was stereotaxically injected into one side of the striatum. 6-hydroxydopamine (6-OHDA) was injected into the same side 1 day later. Another group of rats received rhEPO (5000 u/kg, i.p.) daily for 8 days, and unilateral injection of 6-OHDA in the striatum 3 days after systemic administration of rhEPO. We observed that intrastriatal administration, but not systemic administration of rhEPO significantly reduced the degree of rotational asymmetry. The rhEPO-treated rats also showed an improvement in skilled forelimb use when compared with control rats. The number of tyrosine hydroxylase (TH)-immunoreactive (IR) neurons in the ipsilateral substantia nigra (SN) was significantly larger in intrastriatal rhEPO-treated rats than that in control rats. TH-IR fibers in the 6-OHDA-lesioned striatum were also increased in the intrastriatal rhEPO-treated rats when compared with control rats. In addition, there were lower levels of expression of major histocompatibility complex (MHC) class II antigens and a smaller number of activated microglia in the ipsilateral SN in intrastriatal rhEPO-treated rats than that in control rats at 2 weeks, suggesting that intrastriatal injection of rhEPO attenuated 6-OHDA-induced inflammation in the ipsilateral SN. Our results suggest that intrastriatal administration of rhEPO can protect nigral dopaminergic neurons from cell death induced by 6-OHDA and improve neurobehavioral outcome in a rat model of PD. Anti-inflammation may be one of mechanisms responsible for rhEPO neuroprotection.

A new model to study compensatory mechanisms in MPTP-treated monkeys exhibiting recovery

The cardinal symptoms in Parkinson's disease (PD), akinesia, rigidity and tremor, are only observed when the striatal level of dopamine is decreased by 60-80%. During the preclinical phase of PD, compensatory mechanisms are probably involved in delaying the appearance of motor symptoms. In a MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) monkey model of PD, a spontaneous recovery has been reported after initial intoxication suggesting that compensatory mechanisms are activated in this model as well. Assuming that mechanisms are similar in these phenomena, the study of recovery in monkeys following MPTP intoxication may enable identification of compensatory mechanisms involved in the preclinical phase of PD. In order to maximize the temporal similarity between PD and the MPTP model, we assessed a new progressive monkey model in which spontaneous recovery is expressed systematically and to characterize it based on (1) its behavioural features, and (2) the presence of compensatory mechanisms revealed by an immunohistological approach comparing dopaminergic and serotoninergic innervation between monkeys either exhibiting behavioural recovery or stable motor symptoms. This immunohistological study focused on the substantia nigra, striatum and pallidum, and their anatomical and functional subdivisions: sensorimotor, associative and limbic. The behavioural analysis revealed that with progressive MPTP intoxication motor symptoms were initially expressed in all monkeys. Observable recovery from these symptoms occurred in all monkeys (7/7) within 3-5 weeks after the last MPTP injection, and most exhibited a full recovery. In contrast, acute intoxication induced stable motor symptoms. Despite this obvious behavioural difference, immunohistological methods revealed that the loss of dopaminergic cell bodies in substantia nigra was substantial and similar in both MPTP-treated groups. However, quantification of fibres revealed that recovered monkeys displayed more dopaminergic and serotoninergic fibres than those with stable motor symptoms in sensorimotor and associative territories of striatum and more dopaminergic fibres in internal pallidum. This study provides a new model of PD where all monkeys expressed functional recovery from motor symptoms despite a large dopaminergic neuronal loss. The immunohistological results suggest that both dopamine and serotonin could be implicated in the compensatory mechanisms.

Aging-related changes in the nigrostriatal dopamine system and the response to MPTP in nonhuman primates: diminished compensatory mechanisms as a prelude to parkinsonism

Aging is the most prominent risk factor for Parkinson's disease. Yet, consensus of how advancing age may predispose the dopamine (DA) system to parkinsonism is lacking. Three age ranges of female rhesus monkeys, 8-9, 15-17, and 21-31 years, received unilateral DA depletion with intracarotid 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Morphological and biochemical analyses of DA-depleted and intact hemispheres revealed three primary findings: (1) The intact striatum exhibited age-related declines in dopamine (DA) and homovanillic acid (HVA) that were present by middle age; (2) In the MPTP-treated striatum, the compensatory increase in DA activity was absent in old monkeys; and (3) Age-associated morphological changes included declines in the density of tyrosine hydroxylase (TH) positive fibers in striatum, decreased nigral soma size, and optical density of TH, but no significant loss of neurons. These findings suggest that aging produces changes in the nigrostriatal DA system that approach the threshold for expression of parkinsonian features, and that progressive impairment of plasticity may be central to the role of aging in development of parkinsonism.

Protease-activated receptor-1 mediates protection elicited by thrombin preconditioning in a rat 6-hydroxydopamine model of Parkinson's disease

The etiology of Parkinson's disease remains poorly understood, and current treatment options do not slow disease progression. Recently, chemical (thrombin) preconditioning (TPC) was found to be protective in a 6-hydroxydopamine (6-OHDA) model of the disease. It is important to understand the mechanisms behind these thrombin-induced protective effects. The current study was conducted in the rat to determine whether the protective effects of TPC are mediated via activation of protease-activated receptors (PARs). Preconditioning with specific local infusion of agonist peptides for PAR-1 and PAR-4 3 days before unilateral 6-OHDA administration (10 microg into the medial forebrain bundle) was tested. In addition, co-administration of a PAR-1 antagonist with TPC was examined. In a neurobehavioral assessment battery, PAR-1 agonist preconditioning provided protection in a vibrissae-elicited forelimb placing test, a forelimb-use asymmetry test, and a corner turn test. In addition, inclusion of a PAR-1 antagonist prevented the protective effects elicited by TPC. In contrast to the effects of the PAR-1 agonist, PAR-4 agonist preconditioning afforded no such protection. Indeed, in a lower-dose model of 6-OHDA (5 microg), PAR-4 preconditioning significantly increased behavioral deficits. These results indicate that the protective effects of TPC in this model are mediated through PAR-1 activation. Neither the effects of PAR-1 nor TPC on later 6-OHDA-induced behavioral deficits appeared to be mediated through (DA) content sparing. Further mechanistic studies on the actions of PAR-1 and PAR-4 as detrimental in experimental models of Parkinson's disease are warranted.

Attenuation by Nardostachys jatamansi of 6-hydroxydopamine-induced parkinsonism in rats: behavioral, neurochemical, and immunohistochemical studies

Parkinson's disease (PD) is one of the commonest neurodegenerative diseases, and oxidative stress has been evidenced to play a vital role in its causation. In the present study, we evaluated whether ethanolic extract of Nardostachys jatamansi roots (ENj), an antioxidant and enhancer of biogenic amines, can slow the neuronal injury in a 6-OHDA-rat model of Parkinson's. Rats were treated with 200, 400, and 600 mg/kg body weight of ENj for 3 weeks. On day 21, 2 microl of 6-OHDA (12 microg in 0.01% in ascorbic acid-saline) was infused into the right striatum, while the sham-operated group received 2 microl of vehicle. Three weeks after the 6-OHDA injection, the rats were tested for neurobehavioural activity and were sacrificed after 6 weeks for the estimation of lipid peroxidation, reduced glutathione content, the activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase, quantification of catecholamines, dopaminergic D2 receptor binding and tyrosine hydroxylase expression. The increase in drug-induced rotations and deficits in locomotor activity and muscular coordination due to 6-OHDA injections were significantly and dose-dependently restored by ENj. Lesioning was followed by an increased lipid peroxidation and significant depletion of reduced glutathione content in the substantia nigra, which was prevented with ENj pretreatment. The activities of glutathione-dependent enzymes, catalase and superoxide dismutase in striatum, which were reduced significantly by lesioning, were dose-dependently restored by ENj. A significant decrease in the level of dopamine and its metabolites and an increase in the number of dopaminergic D2 receptors in striatum were observed after 6-OHDA injection, and both were significantly recovered following ENj treatment. All of these results were exhibited by an increased density of tyrosine hydroxylase immunoreactive (TH-IR) fibers in the ipsilateral striatum of the lesioned rats following treatment with ENj; 6-OHDA injection had induced almost a complete loss of TH-IR fibers. This study indicates that the extract of Jatamansi might be helpful in attenuating Parkinsonism.

Parkinsonian signs and cognitive function in old age

Studies have shown that parkinsonian signs are related to cognitive function in aging. What remains unclear is whether this association is stronger for some cognitive domains than it is for others, and precisely how much variability in global and specific cognitive functions is explained by the motor signs. We examined the associations between four parkinsonian signs (gait, rigidity, bradykinesia, tremor) and five cognitive domains (episodic memory, semantic memory, working memory, perceptual speed, visuospatial ability) in a large cohort of older persons who were free of Parkinson's disease and dementia and were participating in the Rush Memory and Aging Project. In a series of regression equations that controlled for age, sex, and education, higher levels of three signs (gait, rigidity, and bradykinesia) were related to lower levels of cognitive function, but they accounted for less than 5% of the variance in most measures. The results did not change when the presence of depressive symptoms, diabetes, and hypertension were added to the models. The cross-sectional association between parkinsonian signs and cognitive function did not vary substantially across specific cognitive domains or specific cognitive tests. The results suggest that parkinsonian signs have a modest, but statistically reliable, association with level of cognitive function in old age.

Sumanirole, a Highly Dopamine D2-Selective Receptor Agonist: In Vitro and in Vivo Pharmacological Characterization and Efficacy in Animal Models of Parkinson's Disease

The purpose of this study is to demonstrate that sumanirole is a novel dopamine receptor agonist with high in vitro and in vivo selectivity for the D(2) receptor subtype. Sumanirole, (R)-5,6-dihydro-5-(methylamino)-4H-imidazo[4,5,1-ij]quinolin-2(1H)-one (Z)-2-butenedioate (1:1), is unique; it has greater than 200-fold selectivity for the D(2) receptor subtype versus the other dopamine receptor subtypes in radioligand binding assays. In cell-based assays, sumanirole is a fully efficacious agonist, with EC(50) values between 17 and 75 nM. In animals, sumanirole elicits many physiological responses attributed to D(2)-like receptor function. In rats, sumanirole is a full agonist for elevation of striatal acetylcholine levels (ED(50) = 12.1 micromol/kg i.p.). Sumanirole s.c. dose dependently decreased plasma prolactin levels and depressed dopamine neuron firing rates in the substantia nigra pars compacta with an ED(50) of 2.3 micromol/kg i.v. This high selectivity for D(2) receptors translates into excellent locomotor stimulant activity in animal models of Parkinson's disease. In reserpinized, alpha-methyl-para-tyrosine-treated rats, sumanirole caused a significant and sustained increase in horizontal activity at doses > or =12.5 micromol/kg s.c. In unilateral 6-hydroxydopamine-lesioned rats, sumanirole caused profound, sustained rotational behavior and was substantially more efficacious than any other agonist tested. Sumanirole-stimulated rotational behavior was blocked by the dopamine receptor antagonist haloperidol. Sumanirole dose dependently improved disability scores and locomotor activities of two of three 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned monkeys. In summary, sumanirole is the first published selective D(2) receptor agonist. The compound has activity in animal models of dopamine hypofunction and has a high level of efficacy in animal models of Parkinson's disease.

Relationship of neuromotor disturbances to psychosis symptoms in first-episode neuroleptic-naive schizophrenia patients

From the very inception of the modern diagnostic scheme for psychotic disorders, abnormalities in motor function have been observed in these conditions. Despite convergence from multiple areas of research supporting the notion that multiple frontal-subcortical circuits regulate motor and limbic behavior, the precise relationship between motor abnormalities and psychopathology has not been elucidated. The goals of this study were to examine the prevalence of extrapyramidal signs (EPS) in first-episode schizophrenia patients and their relationships to three psychopathological dimensions (positive psychosis syndrome, negative syndrome, and disorganization). We assessed EPS using traditional observer-based as well as quantitative instrumental measures in 39 neuroleptic-naive first-episode schizophrenia subjects. Subjects were followed for 6 months after initiating antipsychotic treatment to examine the stability of motor-limbic relationships. Four main findings emerged from this study. First, depending on the measure used the prevalence of dyskinesia prior to treatment ranged from 13% to 20%. The prevalence of parkinsonism ranged from 18% to 28%. Second, severity of dyskinesia was associated with the positive psychotic syndrome; whereas parkinsonism was associated with the positive psychosis, negative syndrome and disorganization. Third, psychopathology improved significantly across all symptom dimensions following antipsychotic treatment, while EPS remained stable. This suggests that some motor abnormalities in schizophrenia may reflect trait characteristics. Fourth, abnormalities on the pre-treatment instrumental measure of parkinsonism predicted greater improvement on positive psychosis symptoms following treatment (p=0.008). Our findings support the notion that neuromotor disturbances may be a core feature of schizophrenia in a substantial proportion of patients and implicate multiple fronto-striatal circuits regulating limbic and neuromotor behavior in schizophrenia.

Physiological studies of information processing in the normal and Parkinsonian basal ganglia: pallidal activity in Go/No-Go task and following MPTP treatment

Understanding the role of the basal ganglia in day to day behavior is critical for a better understanding of the role of these structures in pathological states--such as Parkinson's disease. To elucidate this connection, we studied pallidal activity in a monkey performing a delayed release Go/No-Go task and in monkeys treated with the dopaminergic neurotoxin--MPTP. We compared the results with the predictions of the action selection and reinforcement driven dimensionality reduction models of the basal ganglia. The fraction of responding pallidal neurons, as well as the ratio of positive to negative responses, were equal in the Go and the No-Go modes. The fraction of pallidal neurons with significant responses following the trigger signal (19/26) was higher than that following the visual cue (11/26); however, the fraction of negative responses was significantly higher following the cue signal (47%) than that following the trigger signal (22%). Most (80%) of the cue responses were sensitive to the laterality of the cue, whereas only 25% of the responses following the trigger signal were sensitive to the cue or movement direction. Finally, pallidal spiking activity was not correlated in the normal behaving monkey, and became highly synchronized following MPTP treatment. We conclude that pallidal activity in the normal monkey is consistent with the model of action selection, assuming that action is selected following the visual cue. However, the reinforcement driven dimensionality reduction model is consistent with both the Go/No-Go responses and the normal/MPTP correlation studies.

Protective effect of caffeine against neurodegeneration in a model of Parkinson's disease in rat: behavioral and histochemical evidence

Epidemiological studies have consistently demonstrated an inverse association between coffee consumption and Parkinson's disease (PD). This study was designed to investigate the beneficial effect of caffeine at a dose comparable to that of human exposure in a model of PD. For this purpose, unilateral intrastriatal 6-hydroxydopamine (6-OHDA)-lesioned rats were pretreated with caffeine (20 mg/kg; i.p.) 1 h before surgery and treated twice a day (10 mg/kg) for 1 month. Apomorphine-induced rotations and number of Nissl-stained neurons of substantia nigra pars compacta (SNC) were counted. The results demonstrated that caffeine administration for 1 month could attenuate the rotational behavior in lesioned rats and protect the neurons of SNC against 6-OHDA toxicity.

DAT imaging in drug-induced and psychogenic parkinsonism

Parkinson's syndrome (PS) is frequently encountered in disorders associated with prominent degeneration of the nigrostriatal pathway as in Parkinson's disease, multisystem atrophy, and progressive supranuclear palsy (presynaptic PS). Drug-induced parkinsonism, a common, underdiagnosed health problem and psychogenic parkinsonism are causes of Parkinson's syndrome which, evidence suggests, occurs without degeneration of nigrostriatal structures. We review clinical features and results of DAT imaging in drug-induced parkinsonism and psychogenic parkinsonism. These two conditions normally give normal striatal DAT imaging results; an abnormal result in either case could exclude both conditions, corroborating a diagnosis of organic parkinsonism in uncertain cases.

Protective effect of adenosine in rat model of Parkinson's disease: neurobehavioral and neurochemical evidences

Normal cellular metabolism produces oxidants which are neutralized within the cell by antioxidant enzymes and other antioxidants. An imbalance between oxidant and antioxidant has been postulated to lead the degeneration of dopaminergic neurons in Parkinson's disease. In this study, we examined whether adenosine, an antioxidant, can prevent or slowdown neuronal injury in 6-hydroxydopamine (6-OHDA) model of Parkinsonism. Rats were treated with adenosine (500, 250, 125 mg/kg b.wt.) once before surgery and five times after surgery (1 h interval). 2 microl 6-OHDA (12.5 microg in 0.2% ascorbic acid in normal saline) was infused in the right striatum. Two weeks after 6-OHDA infused rats were tested for neurobehavioral activity and sacrificed after 3 weeks of 6-OHDA infusion, for the estimation of glutathione peroxidase, glutathione-S-transferase, glutathione reductase, glutathione content, lipid peroxidation and dopamine and its metabolites. Adenosine was found to be successful in up-regulating the antioxidant status, lowering the dopamine loss and functional recovery returned close to the baseline dose. This study revealed that adenosine, which is an essential part of our body, might be helpful in slowing down the progression of neurodegeneration in Parkinsonism.

Estradiol and dehydroepiandrosterone potentiate levodopa-induced locomotor activity in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine monkeys

Six monkeys were rendered hemiparkinsonian with a unilateral injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These monkeys displayed ipsilateral circling under basal conditions, and after dopaminergic stimulation with levodopa they decreased their ipsilateral circling and started turning to the contralateral side of their lesion. The effect of 17beta-estradiol and dehydroepiandrosterone (DHEA) was investigated in these animals. 17beta-Estradiol (0.1 mg/kg) added to a threshold dose of levodopa significantly potentiated contralateral circling (mean/30 min) compared to saline or threshold levodopa treatment whereas the duration of circling remained unchanged. DHEA (1-15 mg/kg) alone induced contralateral circling, compared to saline treatment, for 90 min. In addition, DHEA (1-15 mg/kg) potentiated the contralateral circling (mean/30 min) induced by a threshold dose of levodopa and did not change the duration of levodopa circling. A maximal response was observed with 1 or 5 mg/kg of DHEA combined with levodopa depending on the monkey. No correlation was found between the dose for the maximal DHEA response and baseline circling or threshold dose of levodopa. These results suggest that 17beta-estradiol or DHEA is able to potentiate locomotor activity of hemiparkinsonian monkeys. The DHEA doses investigated are similar to those presently used in humans. DHEA may be an alternative to 17beta-estradiol to modulate dopaminergic activity.

Intrastriatal grafting of glomus cells ameliorates behavioral defects of Parkinsonian rats

Parkinson's disease is associated with severe motor dysfunctions due to a progressive loss of dopaminergic neurons in substantia nigra. Transplantation of midbrain neurons from human fetuses to the striatum of patients provides effective treatment for the disease. This type of approach, however, could not be adopted widely due to insufficient supply of fetal materials and the controversial ethical and legal issues. The carotid body is a chemoreceptive organ containing chromaffin-like glomus cells that secrete dopamine (DA) as the neurotransmitter. Here, we report the generation of a clonal dopaminergic cell line of the carotid body using the H-2K(b)-tsA58 transgenic mouse. Cells from the carotid body were immortalized at the permissive temperatures and in the presence of gamma-interferon. The glomus cells were isolated by flow cytometry, and purified to homogeneity by a limited dilution procedure. Upon switching the culture to a nonpermissive condition, the immortal cells ceased to divide, became terminally differentiated and secreted high levels of DA. In rats rendered hemi-Parkinsonian by injection of 6-hydroxydopamine (6-OHDA) into the substantial nigra, intrastriatal grafting of the glomus cells resulted in significant recovery of motor asymmetries and sensorimotor dysfunction. The effects were apparent approximately 10 days after transplantation and remained throughout the 4 months of the study. The recovery of behavioral defects was correlated with the ability of cell grafts to release DA in the brain. As none of the existing treatments for Parkinson's disease is completely satisfactory, establishment of a clonal cell line that secretes DA opens a new avenue for the effective control of this neurological disorder.

Naloxone reduces levodopa-induced dyskinesias and apomorphine-induced rotations in primate models of parkinsonism

Using in situ hybridization, it was found that subchronic treatment with levodopa/benserazide increased preproenkephalin-A and preproenkephalin-B mRNAs in the dopamine-depleted striatum. In order to examine whether dysfunction of the endogenous opioid system may underlie the development of levodopa-induced dyskinesias, the effect of naloxone, an opioid antagonist, on dyskinesias was investigated in two models of parkinsonism in the common marmoset. MPTP-treated monkeys were administered a daily oral dose of levodopa/benserazide which relieved the parkinsonian symptoms but induced severe and reproducible dyskinetic movements. Naloxone (0.1, 0.2 or 0.5 mg/kg) was given subcutaneously (s.c.) during peak-dose dyskinesia, which reduced the dyskinesias significantly using the highest dose, normalized the motor activity, but did not modify the antiparkinson effect. Unilaterally 6-OHDA -lesioned marmosets received apomorphine s.c., which caused a contralateral turning behavior that could be reduced up to 35 percent by concomitant administration of naloxone. Taken together the present results suggest a possible role for the endogenous opioid system in the pathogenesis of levodopa-induced dyskinesia in primates.

PNU-96391A (OSU6162) antagonizes the development of behavioral sensitization induced by dopamine agonists in a rat model for Parkinson's disease

PNU-96391A is a weak dopamine (DA) D(2) receptor antagonist with behavioral stabilizing properties. Previous experiments revealed that PNU-96391A antagonizes the expression of L-DOPA induced behavioral sensitization (dyskinesias) in lesioned primates without inducing akinesia or reducing the anti-Parkinsonian efficacy of L-DOPA. This study evaluated the ability of PNU-96391A to block the development of DA agonist-induced behavioral sensitization in rats with unilateral 6-OH-DA lesions of the median forebrain bundle. Repeated twice daily treatment with L-DOPA and the decarboxylase inhibitor benserazide (15 and 5 mg/kg, IP, respectively), or quinpirole (D(2)/D(3) agonist, 0.1 mg/kg, SC) increased the contralateral rotations measured on day 7 and 14 as compared to day 1. PNU-96391A (10-60 mg/kg, SC, bid.) antagonized the development of behavioral sensitization induced by both agonists. The basal activity of L-DOPA was not affected while a reduction of quinpirole-induced rotations was observed after 30-60 mg/kg, SC of PNU-96391A. Neurochemical analyses confirmed >99 % reductions of striatal DA levels, unilaterally. Concomitant treatment with PNU-96391A and L-DOPA did not affect plasma levels of PNU-96391A indicating that the effects observed are not related to pharmacokinetic interactions. These results suggest that PNU-96391A could be therapeutically useful to prevent the development of behavioral sensitization induced by DA agonists.

[Effect of quetiapine fumarate on drug-induced psychosis in patients with Parkinson's disease]

Among atypical antipsychotics, quetiapine is characterized by a lower incidence of aggravation of parkinsonism due to its lower affinity to D 2. In this study, the effect of quetiapine fumarate (quetiapine) on antiparkinsonian-drug-induced psychosis (e.g. hallucination and delusion) in patients with Parkinson's disease was examined. Ten patients with antiparkinsonian-drugs-induced psychosis were enrolled in this study. The average age of the patients was 69 years and the mean duration of illness was 7 years and 5 months. Psychosis and parkinsonism in these patients were assessed by the Japanese version of PANSS (Positive and Negative Symptom Scale) and UPDRS (Unified Parkinson's Disease Rating Scale) before and during administration of quetiapine, respectively. During the assessment of the effect of quetiapine, the antiparkinsonian drugs that the patients were taking were unchanged. In nine out of the 10 patients, psychotic symptoms disappeared following administration of a relative small dose of quetiapine. No remarkable aggravation of parkinsonism was observed. The present results indicate that quetiapine is an useful drug for treating antiparkinsonian-drug-induced psychosis in the patient with Parkinson's disease.

Clinical characteristics of neuroleptic-induced parkinsonism

In order to characterize the clinical spectrum of neuroleptic-induced parkinsonism (NIP), we studied a population of consecutive psychiatric in-patients treated with neuroleptics for at least two weeks, who were diagnosed by their psychiatrist as having parkinsonism. Parkinsonism was confirmed by a movement disorders specialist who performed neurological assessment including the motor examination and the activities of daily living (ADL) sections of the Unified Parkinson's Disease Rating Scale (UPDRS), and the Hoehn and Yahr (H&Y) staging. Seventy-five patients (54 males), aged 46 +/- 13 years (range 21 to 73 years) were included in the analysis. The mean duration of neuroleptic therapy was 15 +/- 12 years, while 61% were treated for more than 10 years. Most of the patients (n = 66, 88%) were scored as H&Y stage 2.5 or less. Rest tremor was present in 44% of the patients, and usually persisted in action. Forty-one patients (61%) had symmetrical involvement. Parkinsonian signs were significantly more common and pronounced in the upper in comparison with the lower limbs (p = 0.0001). Gait disturbances were mild and freezing of gait was very rare (n = 2). Neither age nor duration of therapy or their interaction affected the total motor score or any of the motor sub-scores. In conclusion, NIP differs from PD for more bilateral involvement with relative symmetry, and by affecting upper limbs more often than the lower ones. NIP tends to be associated with the triad of bradykinesia, tremor and rigidity while PD tends to involve gait and posture more often. NIP develops unrelated to duration of neuroleptic treatment or age of the patient, suggesting an individual predisposition to blockage of the dopaminergic receptors.

Effects of the prolyl endopeptidase inhibitor S 17092 on cognitive deficits in chronic low dose MPTP-treated monkeys

A number of neuropeptides are affected in Parkinson's disease and the enzyme proline endopeptidase contributes to the degradation of many of these neuropeptides, some of which are linked to a variety of cognitive functions. In the present study, the effects of the highly potent proline endopeptidase inhibitor S 17092 on cognitive deficits in monkeys induced by chronic low dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration were examined. Chronic low dose MPTP administration resulted in deficits in performance of variable delayed response, delayed matching-to-sample, and delayed alternation tasks. Seven day oral administration of S 17092 followed by single dose administration of the same dose on the day of testing significantly improved overall performance on these tasks. The most effective dose of S 17092 was 3 mg/kg. These results indicate that S 17092 has cognition-enhancing properties in this model of early parkinsonism.

Pharmacological validation of behavioural measures of akinesia and dyskinesia in a rat model of Parkinson's disease

In an attempt to define clinically relevant models of akinesia and dyskinesia in 6-hydroxydopamine (6-OHDA)-lesioned rats, we have examined the effects of drugs with high (L-DOPA) vs. low (bromocriptine) dyskinesiogenic potential in Parkinson's disease on three types of motor performance, namely: (i) abnormal involuntary movements (AIMs) (ii) rotational behaviour, and (iii) spontaneous forelimb use (cylinder test). Rats with unilateral 6-OHDA lesions received single daily i.p. injections of L-DOPA or bromocriptine at therapeutic doses. During 3 weeks of treatment, L-DOPA but not bromocriptine induced increasingly severe AIMs affecting the limb, trunk and orofacial region. Rotational behaviour was induced to a much higher extent by bromocriptine than L-DOPA. In the cylinder test, the two drugs initially improved the performance of the parkinsonian limb to a similar extent. However, L-DOPA-treated animals showed declining levels of performance in this test because the drug-induced AIMs interfered with physiological limb use, and gradually replaced all normal motor activities. L-DOPA-induced axial, limb and orolingual AIM scores were significantly reduced by the acute administration of compounds that have antidyskinetic efficacy in parkinsonian patients and/or nonhuman primates (-91%, yohimbine 10 mg/kg; -19%, naloxone 4-8 mg/kg; -37%, 5-methoxy 5-N,N-dimethyl-tryptamine 2 mg/kg; -30%, clozapine 8 mg/kg; -50%, amantadine 40 mg/kg). L-DOPA-induced rotation was, however, not affected. The present results demonstrate that 6-OHDA-lesioned rats do exhibit motor deficits that share essential functional similarities with parkinsonian akinesia or dyskinesia. Such deficits can be quantified using novel and relatively simple testing procedures, whereas rotometry cannot discriminate between dyskinetic and antiakinetic effects of antiparkinsonian treatments.

Pharmacological involvement of the calcium channel blocker flunarizine in dopamine transmission at the striatum

Single intrastriatal microinjections of 25, 50 and 100nmol/microl of flunarizine in normal rats produced a dose-dependent turning behavior toward the injected side when they were challenged with apomorphine (1mg/kg, s.c). This effect was seen at 1, 3 and 7 days following administration of the high dose of flunarizine, but had subsided by 24h after administration of the intermediate dose; the low dose was ineffective. However, intrastriatal injection of the high dose of flunarizine resulted in a local lesion and thereafter this dose was not used. A similar dose-response relationship was determined for nifedipine, an L-type calcium channel antagonist. Injection of this antagonist did not result in apomorphine-elicited rotational behavior, reflecting its lack of antidopaminergic action. Intrastriatal injections of haloperidol (5microg/microl), an antagonist of dopamine D(2) receptors, or the sodium channel blocker lidocaine (40microg/microl), were given in order to compare their effects to those observed with flunarizine. Intracerebral injection of haloperidol produced ipsilateral turning in response to systemic administration of apomorphine given 60min after. The same response was obtained with the injection of apomorphine 10min after the injection of intracerebral lidocaine. This effect was no longer apparent 24h after the microinjection of haloperidol and 60min after the injection of lidocaine. In rats rendered hemiparkinsionian by lesioning the nigrostriatal pathway with 6OHDA, intrastriatal microinjection of flunarizine (50nmol/microl) significantly reduced apomorphine (0.2mg/kg, s.c.)-elicited turning behavior towards the non-lesioned side. These results suggest an antidopaminergic effect of flunarizine mediated by antagonistic action of post-synaptic striatal dopamine receptors. However, an action of the drug on sodium channels may not be ruled out. These studies offer additional supporting evidence for the induction or aggravation of extrapyramidal side-effects in patients receiving flunarizine.

[Effects of yanggan xifeng recipe on changes of neurological behavior of rat of Parkinson's model]

OBJECTIVE

To investigate the effect of Yanggan Xifeng Recipe (YGXFR) for nourishing Liver to calm down endogenous Wind on neurological behavior of Parkinson's disease (PD) rat model.

METHODS

PD rat model was established by destroying the substantia nigra condense area (SNc) and ventral tegmental area (VTA) unilaterally with 6-hydroxy dopamine (6-OHDA). The rats for control were injected in the same site with the same dose of normal saline. The animals were randomly divided into 3 groups (7 in each group), the control group, the model group and the TCM treated group. Staircase test and rotation test induced by apomorphine were performed in all groups and compared.

RESULTS

The staircase test demonstrated that, after being treated with YGXFR, the food pellets intake were increased compared to model group (P < 0.05), and their rotation induced by apomorphine was lessened (P < 0.01).

CONCLUSION

YGXFR could recover the neurological behavior deficits of PD rat models.

[Follow-up study after enteral manganese poisoning: clinical, laboratory and neuroradiological findings]

Manganese intoxication is an unusual, severe form of intoxication. This report deals with a patient now 80 years old who accidentally ingested a solution of potassium permanganate for a period of at least 4 weeks 14 years ago. Since then, the patient suffers from a mild parkinsonian syndrome and distally accentuated polyneuropathies. Psychiatric disorders, especially demential or depressive symptoms, were not observed. Manganese analysis of his hair still shows a clear increase in manganese concentration. The MRI of his brain showed no pathological changes, in particular none of those often described with symmetric signal elevation in T1 in the area of the basal ganglia. In this study, we present clinical, laboratory, and neuroradiological findings. Unusual in this case with a short exposition is the long duration and clinical improvement without L-dopa treatment.

Spatial memory improvement by levodopa in parkinsonian MPTP-treated monkeys

RATIONALE

The ameliorative effects of levodopa (L-3,4-dihydroxy-phenylalanine) on the motor impairment in Parkinson's disease patients is well established, but characterization of its effects on the associated cognitive deficits is still incomplete.

OBJECTIVE

The present study determined the effect of different doses of levodopa on performance on a test of working memory in MPTP-treated rhesus monkeys, an animal model of Parkinson's disease.

METHODS

Four MPTP-treated monkeys and their age-matched controls with the same experimental history as the MPTP-treated monkeys were tested on a spatial delay response task. Each daily session consisted of five trials at each of seven randomly presented delays (0, 10, 20, 30, 40, 50 and 60 s). Training was continued for 5 days in each of five different conditions. In the first condition, control and MPTP-treated animals performed the task without levodopa. In the second condition, both groups were tested with a dose of 100 mg of levodopa. In the third and fourth conditions, in which the doses of levodopa were increased to 250 and 500 mg, respectively, only the MPTP-treated animals were tested. In the final condition, the MPTP-treated animals where retested without levodopa.

RESULTS

Significant improvement was observed at all doses tested (range 100-500 mg).

CONCLUSIONS

Levodopa can ameliorate memory impairments in this parkinsonian model.

Striatal preproenkephalin gene expression is upregulated in acute but not chronic parkinsonian monkeys: implications for the contribution of the indirect striatopallidal circuit to parkinsonian symptomatology

This study examined the extent of striatal dopamine (DA) denervation and coincident expression of preproenkephalin (PPE) mRNA in monkeys made parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. Some animals (n = 4) became moderately parkinsonian after receiving large doses of MPTP over short periods of time and were symptomatic for only a short period of time (1-3 months; acute parkinsonian group). Other animals became moderately parkinsonian after receiving either escalating doses of MPTP over long periods (4-6 months; n = 5) or a high dose of MPTP over a short period (<1 month; n = 1) and remained symptomatic for an extended period (>8 months; chronic parkinsonian group). Despite similar symptomatology and similar degrees of striatal DA denervation at the time of their deaths, only acute parkinsonian animals had significantly increased PPE expression in sensorimotor striatal regions. PPE expression in chronic parkinsonian animals was either not changed or significantly decreased in most striatal regions. These findings suggest that the duration and not the extent of striatal DA denervation is a critical factor in modulating changes in striatal PPE expression. Furthermore, these results question the role of increased activity in the enkephalin-containing indirect striatopallidal pathway in the expression of parkinsonian symptoms.

MPTP-induced Parkinsonism in minipigs: A behavioral, biochemical, and histological study

Fourteen male Göttingen minipigs were used in this study. Nine were administered N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dosage of 1 mg/kg/day, SC, for 6 days, the last five pigs received saline injections for 6 days. All MPTP-treated animals developed Parkinson symptoms, i.e., muscle rigidity, hypokinesia, and impaired coordination within 5 days. The brain levels of dopamine (DA), and its major metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were determined in caudatum and putamen 2, 14, and 93 days (n = 3/time point) after the last drug administration. In eight of the MPTP-treated animals, striatal DA, DOPAC, and HVA concentrations were reduced from 50 to 95% compared to control animals at all time intervals. Animals with the lowest striatal DA concentrations showed the most severe signs of Parkinsonism. The number of cells in substantia nigra (SN) showed a decline only 3 months after MPTP treatment. The minipigs represent a nonprimate model of MPTP-induced parkinsonism syndromes lasting at least months.

The validity of the pretreated, unilaterally MPTP-treated monkeys as a model of Parkinson's disease: a detailed behavioural analysis of the therapeutic and undesired effects of the D2 agonist quinpirole and the D1 agonist SKF 81297

The goal of this study was to evaluate the validity of the pretreated, unilaterally MPTP-treated monkey as an animal model of Parkinson's disease (PD). For that purpose, a detailed ethogram was developed and assessed in four male rhesus monkeys that had received MPTP (2.5 mg) in the carotid artery contralateral to the dominant limb. Subsequently, the behavioural effects of the dopamine D2 agonist quinpirole and the dopamine D1 agonist SKF 81297 were studied. The ethogram was found to allow a clear-cut and objective separation of drug-induced behaviours into therapeutic and undesired effects in the MPTP-treated monkeys. Saline-treated monkeys predominantly displayed ipsilateral goal-directed fore-limb movements, and distinct types of ipsilaterally directed rotations. Although quinpirole and SKF 81297 increased motor behaviours, such as body displacement, contralateral fore-limb movements and contralateral rotational behaviours, assessment of the new detailed ethogram revealed that this increase was completely due to the activation of abnormal, non-goal-directed behaviours, such as dyskinetic fore-limb movements, pivoting and shuffling. Moreover, the new ethogram made clear that the drug treatments induced not only dyskinesia and dystonia, but also epileptoid behaviour, which was confirmed by EEG analysis. In summary, the detailed behavioural analysis showed that this model does not adequately predict the clinical effects of the D2 agonist. It is concluded that the pretreated, unilaterally MPTP-treated monkey is not a valid model to predict the therapeutic and undesired effects of dopaminergic drugs in humans.

The predictive validity of the drug-naive bilaterally MPTP-treated monkey as a model of Parkinson's disease: effects of L-DOPA and the D1 agonist SKF 82958

The aim of this study was twofold: (1) to study the predictive validity of the drug-naive, bilaterally MPTP-treated monkey as an animal model of Parkinson's disease (PD), and (2) to investigate the therapeutic and undesired effects of the D1 agonist SKF 82958 as compared to L-DOPA treatment, in drug-naive and L-DOPA pretreated monkeys. A detailed ethogram was used, allowing the separation of therapeutic and undesired effects. Eight weeks after bilateral intracarotid MPTP administration, SKF 82958 (1 mg/kg, n = 4, SKF 82958, naive group) or methyl-L-DOPA + carbi-dopa (10 + 2.5 mg/kg, n = 4, L-DOPA group) was administered intramuscularly for 22 days. After a drug-free period of eight weeks, the L-DOPA group was treated with SKF 82958 for 22 days (SKF 82959, 1 mg/kg, n=4, pretreated). All drug treatments increased the parameters used classically to evaluate dopaminergic drugs, namely body displacement, dyskinesia and dystonia. However, the new detailed analysis revealed that L-DOPA, but not SKF 82958, had therapeutic effects, reflected by an increase in goal-directed fore-limb use. SKF 82958, but not L-DOPA, induced additional undesired effects; including epileptoid behaviours in both drug-naive and drug-pretreated monkeys. In one L-DOPA-unresponsive monkey, SKF 82958 did induce minor therapeutic effects, as well as undesired effects. Although the effects of SKF 82958 on fore-limb movements, rotational behaviours and body displacement were comparable in the naive and pretreated group, SKF 82958 re-initiated undesired effects in the L-DOPA pretreated group from day one. It is concluded that the bilaterally MPTP-treated monkey is an animal model with predictive validity for PD: it adequately predicts the therapeutic effects and undesired effects of L-DOPA. Furthermore, it is concluded that SKF 82958 is less effective than L-DOPA in the treatment of PD, because it did not induce therapeutic effects, but instead elicited several undesired effects.

[A case of Parkinson syndrome secondary to combined amineptine and bromazepam abuse]

A case report of parkinsonism secondary to chronic abuse of amineptine (3 gr/day) and bromazepam (35 mg/day) in a patient diagnosed of borderline personality disorder is presented. The patient did not take any other drugs and he was not recently on neuroleptic treatment; he recognized the abuse of amineptine, as a stimulant, and the bromazepam abuse, looking for a relief to the excessive anxiety secondary to amineptine. The parkinsonism improved after removing both drugs and taking biperiden and diazepam; lastly the patient was discharged without any medication. The patient did not suffer from other complications associated with amineptine or bromazepam abuse. There are some cases reported of parkinsonism secondary to benzodiazepines but there is none secondary to amineptine. We present a short review of the possible responsible mechanisms, thinking on a complex interaction of both drugs on dopamine and its modulatory systems.

Effects of acute or prolonged administration of cabergoline on parkinsonism induced by MPTP in common marmosets

The effects of a single treatment or chronic administration of cabergoline (1-[(6-allylergolin-8beta-yl)carbonyl]-1-[3-(dimethylamino)p ropyl]-3-ethyl-urea), a potent, long-lasting dopamine receptor agonist, on parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in common marmosets were studied. The administration of 0.2 mg/kg or a higer dose of cabergoline began to reverse parkinsonism-like symptoms 60 min after a subcutaneous injection, and showed steady and constant effects throughout the observation period. For prolonged administration, 0.2 mg/kg cabergoline was injected daily for 22 consecutive days. Locomotor activity in MPTP-treated animals increased until it reached its peak on the third day, then it gradually decreased. Akinesia scores, rating the quality of movements, were also improved, and the improvement was sustained up to the last day of chronic administration. None of the animals developed abnormal behaviors after either acute or chronic administration. These results suggest that cabergoline has long-acting effects in the marmoset model of parkinsonism, and that it will be a useful agent for the treatment of Parkinson's disease, particularly in cases with fluctuating motor disabilities.

Effects of repeated administration of l-DOPA and apomorphine on circling behavior and striatal dopamine formation

We tested the circling response to l-DOPA and apomorphine administration in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra. Rats demonstrated a progressively diminished circling response when l-DOPA-carbidopa was repeatedly administered at 120 min intervals. This decreasing response was not present when apomorphine was administered under the same conditions. We also perfused l-DOPA directly into the striatum in vivo of rats with an ipsilateral 6-OHDA nigrotomy at 60 min intervals and monitored striatal dopamine levels with the technique of brain microdialysis. Dopamine formation increased from the first to the fifth trial. This may be secondary to the decrease in uptake sites which accompanies the loss of striatal dopamine nerve terminals. We postulate that the continued presence of dopamine at striatal receptor sites conditions a short-term loss of dopamine receptor sensitivity and a consequent decreased circling response. The observation that desensitization (as measured by decreasing circling) was not present following repeated apomorphine administration may be attributable to its shorter duration of action. We also perfused l-DOPA into the striatum of normal rats and noted a progressive decrease in striatal dopamine levels from the first to the fifth trial. Since this occurred following direct administration of l-DOPA into the striatum, the decrease could not be accounted for by peripheral pharmacodynamics or bioavailability of l-DOPA in the striatum. Since this decrease in dopamine formation was seen only in the normal striatum, its relevance to the diminished behavioral response is unclear.

Behavioural effects of subthalamic nucleus lesions in the hemiparkinsonian marmoset (Callithrix jacchus)

Recent studies in non-human primates support a role for the subthalamic nucleus in the expression of parkinsonian symptomatology, and it has been proposed that subthalamic lesions may provide a surgical treatment for the symptoms of Parkinson's disease in humans. We have applied a broad range of behavioural tests to characterize the effects of lesions of the subthalamic nucleus on parkinsonian symptoms in the unilateral 6-hydroxydopamine (6-OHDA) lesioned marmoset (Callithrix jacchus). Thirteen marmosets were trained on a battery of behavioural tasks that were conducted at regular intervals before and after surgery. All received unilateral 6-OHDA lesions to the medial forebrain bundle. Seven animals were then given an additional N-methyl-D-aspartate lesion of the ipsilateral subthalamic nucleus, whereas the remaining six animals received a variety of control or sham lesions to the nucleus. The 6-OHDA lesions induced a strong ipsilateral bias in head position; mild-moderate ipsilateral rotation spontaneously and after injection of saline or amphetamine; and contralateral rotation after injection of apomorphine. Hemineglect was evident as delayed initiation of reaches on the contralateral side on the staircase reaching task. Additional subthalamic lesions significantly reversed the bias in head position from ipsilateral to contralateral and decreased neglect as evidenced by improved latencies to initiate reaching on the contralateral side at the staircase. However, deficits in skilled movements persisted in the subthalamic nucleus lesion group in that they did not complete the staircase task any faster than the control group and remained impaired on another task which required reaching into tubes. These behavioural effects demonstrate that excitotoxic lesioning of the subthalamic nucleus can ameliorate some, but not all, parkinsonian-like deficits in the unilateral 6-OHDA lesioned marmoset.

Fixed-ratio discrimination training as replacement therapy in Parkinson's disease: studies in a 6-hydroxydopamine-treated rat model

Severe 6-hydroxydopamine (6-OHDA)-induced neostriatal dopamine (DA) depletion is generally held to be irreversible. Adult rats administered 6-OHDA soon after weaning, or neonatally, respectively model Parkinson's disease (PD) and Lesch-Nyhan syndrome (LNS). Prior studies in our laboratory indicate that prolonged training on incrementally more difficult fixed-ratio (FR) discriminations can reverse 'irreversible' 6-OHDA-induced neostriatal DA depletion in adult LNS rats. The present study evaluated the effects of such training on neostriatal DA depletion and its functional consequences in adult PD and control (vehicle-injected) rats. After recovery from 6-OHDA-induced hypophagia, rats were sacrificed to assess neostriatal DA depletion magnitude, or were food-deprived and either subjected to food-maintained operant FR discrimination training or allowed to remain in their home cages. 6-OHDA treatment antagonized amphetamine (AMP)-induced increases in brief rearing behavior and locomotor activity in 3-month-old PD rats prior to training, and reduced operant response rates throughout training without affecting learning rates. One week after training, AMP-increased locomotor and brief-rearing frequencies were augmented in all groups except trained controls, and the prior inhibitory effect of 6-OHDA treatment on AMP-increased behavioral frequencies was essentially eliminated. Cumulative apomorphine (APO) dose-effect curve (0.1-3.2 mg/kg) construction 3 weeks post-training revealed that 6-OHDA treatment abolished APO-induced intense licking behavior. However, training eliminated the hyperresponsiveness of 6-OHDA-treated rats to the locomotor- and brief-rearing stimulant effects of APO but did not affect the depletion of neostriatal DA. Nevertheless, 6-OHDA-induced increases in neostriatal DOPAC/DA and HVA/DA ratios were normalized by age/food-deprivation while that of 3MT/DA was not. These findings suggest that training reduces the functional responsiveness of at least some central DA receptors, FR discrimination training could be a useful adjunct to PD replacement therapy and that the neostriatal DA-repleting action of training in 6-OHDA-treated rats depend on the age at which 6-OHDA is administered.

Physiological aspects of information processing in the basal ganglia of normal and parkinsonian primates

There are two views as to the character of basal-ganglia processing - processing by segregated parallel circuits or by information sharing. To distinguish between these views, we studied the simultaneous activity of neurons in the output stage of the basal ganglia with cross-correlation techniques. The firing of neurons in the globus pallidus of normal monkeys is almost always uncorrelated. However, after dopamine depletion and induction of parkinsonism by treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), oscillatory activity appeared and the firing of many neurons became correlated. We conclude that the normal dopaminergic system supports segregation of the functional subcircuits of the basal ganglia, and that a breakdown of this independent processing is a hallmark of Parkinson's disease.

Antiparkinsonian effects of BAM-1110, a novel ergoline derivative, in MPTP-treated cynomolgus monkeys

BAM-1110 [(5R,8R,10R)-6-methyl-8-(1,2,4-triazol-l-ylmethyl) ergoline maleate] is a newly synthesized dopamine agonist that produces little anorexic side effects (nausea and vomiting). The current study examines the effects of BAM-1110 on parkinsonian symptoms in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys, an animal model of Parkinson's disease. First, a significant antiparkinsonian effect of apomorphine hydrochloride (0.3 mg/kg given subcutaneously) was confirmed in these animals. BAM-1110 (0.1, 0.3, and 1 mg/kg subcutaneously) relieved parkinsonian symptoms in a dose-dependent manner. Significant effects were observed at doses of 0.3 and 1 mg/kg and lasted for at least 3 h. BAM-1110, at a dose of 0.3 mg/kg that produced the submaximal antiparkinsonian effect, did not induce significant abnormal behaviors such as hyperactivity and stereotyped behaviors. Significant stereotyped behaviors were observed at 1 mg/kg of BAM-1110. Apomorphine induced hyperactive and stereotyped behaviors in parallel with its antiparkinsonian effect. BAM-1110 appears to be a potentially useful dopamine agonist to treat Parkinson's disease because of its relatively weak drug-induced hyperactive disturbances and anorexic side effects.

Association of plasma homovanillic acid with behavioral symptoms in patients diagnosed with dementia: a preliminary report

Neuroleptic treatment of psychotic symptoms or agitated behavior in elderly patients diagnosed with dementia is associated with reduced efficacy and increased rates of neuroleptic-induced parkinsonism in comparison to younger patients with schizophrenia. We report the first study to examine the relationship between an in vivo measure of dopaminergic function, plasma homovanillic acid (pHVA), and ratings of psychosis, agitation, and parkinsonism before and after neuroleptic treatment in dementia patients. Pretreatment pHVA was significantly correlated with parkinsonian rigidity, with a trend observed with agitation and hostility. Though mean pHVA did not change during perphenazine treatment, intraindividual change in pHVA at day 15 was correlated with improvement in hostility, with a similar trend for improvement in agitation. These preliminary findings are consistent with reports associating dopaminergic function with agitated, but not psychotic, symptoms in patients diagnosed with dementia, and with a reduced responsivity of dopaminergic systems to neuroleptic treatment in these patients.