Development of dyskinesias in a 5-year trial of ropinirole and L-dopa.

A 5-year trial of ropinirole and levodopa in early Parkinson's disease showed that ropinirole is associated with reduced incidence of dyskinesias. This post hoc analysis investigated whether the dyskinesia-sparing benefit of ropinirole is lost when levodopa is added to the regimen and evaluated other risk factors for developing dyskinesias. Patients receiving levodopa had a significantly higher risk of dyskinesias than those taking ropinirole monotherapy (hazard ratio [HR], 6.67; 95% confidence interval [CI], 3.23-14.29; P < 0.001). When patients randomized to ropinirole were treated with supplementary levodopa, the development of dyskinesias was not significantly different from that in those receiving levodopa from the start (HR, 0.80; 95% CI, 0.48-1.33; P = 0.39). However, the onset of dyskinesias was delayed by around 3 years compared with levodopa monotherapy. Adjusted analyses taking into account baseline and on-treatment factors that influenced use of supplementary levodopa or the development of dyskinesias produced similar results. In conclusion, the risk of developing dyskinesias during maintained initial ropinirole monotherapy is very low. Only once levodopa is added does the risk substantially change. Early use of ropinirole postpones the onset of dyskinesias, but these benefits decline when levodopa therapy is started, with no evidence of a subsequent rapid "catch-up" or a persisting preventive effect.     

Disordered respiration as a levodopa-induced dyskinesia in Parkinson's disease.

Symptomatic respiratory disturbance as a consequence of levodopa (L-dopa) therapy for Parkinson's disease (PD) has been described only rarely and may be underrecognized in clinical practice. We report on two patients with PD in whom the introduction or augmentation of L-dopa therapy was associated with the development of irregular and rapid breathing. Analysis of breathing patterns before and after L-dopa demonstrated a striking change in respiratory rate after administration of L-dopa, with the emergence of irregular tachypnea alternating with brief periods of apnea, in a pattern consistent with a central origin. In both cases, the temporal relationship of the respiratory disturbance to the administration of L-dopa suggested a peak-dose drug effect. Previous reports of L-dopa-induced respiratory dyskinesia are reviewed, and the potential mechanisms whereby L-dopa might influence the central control of respiration to produce irregular breathing patterns are discussed.     

Onset of dyskinesia with adjunct ropinirole prolonged‐release or additional levodopa in early Parkinson's disease

Levodopa‐induced dyskinesia can result in significant functional disability and reduced quality of life in patients with Parkinson's disease (PD). The goal of this study was to determine if the addition of once‐daily ropinirole 24‐hour prolonged‐release (n = 104) in PD patients not optimally controlled with levodopa after up to 3 years of therapy with less than 600 mg/d delays the onset of dyskinesia compared with increasing doses of levodopa (n = 104). During the study, 3% of the ropinirole prolonged‐release group (mean dose 10 mg/d) and 17% of the levodopa group (mean additional dose 284 mg/d) developed dyskinesia (P < 0.001). There were no significant differences in change in Unified Parkinson's Disease Rating Scale activities of daily living or motor scores, suggesting comparable efficacy between the two treatments. Adverse events were comparable in the two groups with nausea, dizziness, insomnia, back pain, arthralgia, somnolence, fatigue, and pain most commonly reported. Ropinirole prolonged‐release delayed the onset of dyskinesia with comparable efficacy to increased doses of levodopa in early PD patients not optimally controlled with levodopa. © 2010 Movement Disorder Society     

Effect of pulsatile administration of levodopa on dyskinesia induction in drug‐naïve MPTP‐treated common marmosets: Effect of dose,frequency of administration,and brain exposure

Levodopa (L ‐dopa) consistently primes basal ganglia for the appearance of dyskinesia in parkinsonian patients and 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine hydrochloride (MPTP) ‐treated primates. This finding may reflect its relatively short duration of effects resulting in pulsatile stimulation of postsynaptic dopamine receptors in the striatum. We have compared the relationship between L ‐dopa dose and frequency of administration on dyskinesia initiation in drug‐naïve, MPTP‐treated common marmosets. We have also studied the effect of increased brain exposure to pulsatile administration by combining a low‐dose of L ‐dopa with the peripheral catechol‐O‐methyltransferase inhibitor (COMT‐I), entacapone. Pulsatile administration of a low (dose range, 5.0–7.5 mg/kg p.o.) or a high (12.5 mg/kg) dose of L ‐dopa plus carbidopa b.i.d. produced a dose‐related reversal of motor deficits. Repeated administration of low and high doses of L ‐dopa for 26 days to drug‐naïve, MPTP‐treated animals also caused a dose‐related induction of peak‐dose dyskinesia. Repeated administration of high‐dose L ‐dopa b.i.d. compared to once daily caused a frequency‐related improvement of motor symptoms, resulting in a more rapid and initially more intense appearance of peak‐dose dyskinesia. Administration of low‐dose L ‐dopa b.i.d. for 26 days in combination with entacapone enhanced the increase in locomotor activity and reversal of disability produced by L ‐dopa alone, but with no obvious change in duration of L ‐dopa's effect. However, combining entacapone with L ‐dopa resulted in the more rapid appearance of dyskinesia, which was initially more severe than occurred with L ‐dopa alone. Importantly, increasing pulsatile exposure of brain to L ‐dopa by preventing its peripheral breakdown also increases dyskinesia induction. © 2003 Movement Disorder Society     

The monoamine reuptake blocker brasofensine reverses akinesia without dyskinesia in MPTP-treated and levodopa-primed common marmosets.

The common marmoset develops motor deficits after MPTP treatment and exhibits dyskinesia after chronic levodopa (L-dopa) dosing and subsequent re-challenge with L-dopa and other dopaminergic agents. We report on the actions of the potent monoamine reuptake blocker brasofensine on motor disability, locomotor activity, and dyskinesia in the 1-methyl-4-1, 2,3,6-tetrahydropyridine (MPTP) -treated marmoset model of Parkinson's disease. Oral administration of brasofensine (0.25, 0.5, 1.0, or 2.5 mg/kg) to MPTP-treated marmosets produced a long-lasting, dose-dependent increase in locomotor activity and reduction in disability scores. In addition, coadministration of the lowest dose of brasofensine (0.25 mg/kg orally) with a threshold oral dose of L-dopa (2.5 mg/kg) caused a marked increase in locomotor activity, greater than that produced by either drug alone. In other MPTP-treated marmosets previously primed to exhibit dyskinesia by repeated L-dopa dosing, brasofensine effectively reversed akinesia with a naturalistic and prolonged motor response without the appearance of dyskinesia or stereotypy. This finding contrasts with the severe dyskinesia, stereotypy, and hyperkinesis produced by equivalent doses of L-dopa. The ability of brasofensine to produce a prolonged and naturalistic antiparkinsonian response without eliciting dyskinesia after previous L-dopa priming may relate to actions on D(1) receptor-linked pathways. These findings suggest that monoamine reuptake blockade may be of value in the treatment of Parkinson's disease, both early in the disease course and when L-dopa-induced dyskinesias complicate treatment.     

Tardive dyskinesia model in the common marmoset.

Thirteen adult common marmosets (Callithrix jacchus) were given once-monthly injections of haloperidol decanoate (5-15 mg/kg i.m.) for one year. Thereafter, drug-free and treatment periods alternated at 3-month intervals. After 2.5 to 14 months, 12 monkeys showed symptoms of tardive dyskinesia (TD), such as periocular and perioral twitchings, tongue protrusions, masticatory movements, and choreic movements in arms and legs. When TD symptoms were evident, the periodic treatment was interrupted and symptoms persisted for at least 5 months after the last haloperidol dose, worsened by injection of the anticholinergic drug biperiden. An injection of nondepot haloperidol (0.12 or 0.25 mg/kg) produced a reduction of TD symptoms. At the end of the study, nondepot haloperidol was injected once a week at two doses (0.12 and 0.25 mg/kg i.m.). A syndrome of excitation with peculiar behavior, interpreted as acute dystonia, was precipitated in all animals. The animals showed sustained retrocollis, climbing upside down, biting the perch, repetitive turnings, and frequent backward movements. The dystonic movements lasted approximately 6 hours and were reduced but not completely extinguished by biperiden (0.1 mg/kg). The TD syndrome registered in marmosets may provide a useful model for screening new antipsychotics for their propensity to induce TD.     

Antiparkinsonian effects of the novel D3/D2 dopamine receptor agonist, S32504, in MPTP-lesioned marmosets: Mediation by D2, not D3, dopamine receptors.

L-dopa remains the most common treatment for Parkinson's disease. However, there is considerable interest in D3/D2 receptor agonists such as the novel agent S32504, since they exert antiparkinsonian properties in the absence of dyskinesia. An important question concerns the roles of D2 vs. D3 receptors, an issue we addressed with the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned nonhuman primate model of Parkinson's disease. In L-dopa-primed animals, S32504 (0.16-2.5 mg/kg p.o.) dose-dependently enhanced locomotor activity. This action was abolished by the D2 antagonist, L741,626 (2.5 mg/kg), but potentiated by the D3 antagonist, S33084 (0.63 mg/kg). Both antagonists were inactive alone. In drug-naive animals, a maximally effective dose of S32504 (2.5 mg/kg p.o.) displayed pronounced antiparkinsonian properties from the third day of administration, and its actions were expressed rapidly and durably. Thus, on day 33, antiparkinsonian properties of S32504 were apparent within 5 minutes and present for > 4 hours. Moreover, they were associated with neither wearing off nor significant dyskinesia. In conclusion, the novel D3/D2 agonist S32504 may offer advantages over L-dopa in the treatment of newly diagnosed parkinsonian patients. Its actions are expressed primarily by activation of D2, not D3, receptors.     

Effects of CB1 cannabinoid receptor modulating compounds on the hyperkinesia induced by high-dose levodopa in the reserpine-treated rat model of Parkinson's disease.

The present study was designed to determine the potential of CB1 cannabinoid receptor modulating compounds in the treatment of L-3,4-dihydroxyphenylalanine (L-dopa)-induced dyskinesia in Parkinson's disease. In the reserpine-treated rat model of parkinsonism, administration of a high dose of L-dopa (150 mg/kg) but not of Cl-APB (0.5 mg/kg) or quinpirole (0.5 mg/kg) produced a hyperkinetic state characterised by an increase in horizontal and vertical activity, which likely represent correlates of antiparkinsonian and dyskinetic activity, respectively. Injection of the CB1 cannabinoid receptor antagonist SR141716 (0.1-3 mg/kg) reduced the increase in vertical activity elicited by L-dopa without affecting the increase in horizontal activity. Injection of the CB1 cannabinoid receptor agonist WIN55,212-2 (0.1-3 mg/kg) reduced the L-dopa-induced increase in vertical activity and, at the highest dose only (3 mg/kg), also reduced horizontal activity elicited by L-dopa. WIN55,212-2 (1 mg/kg) reduced motor activity induced by both the D1 receptor agonist Cl-APB (0.5 mg/kg) and the D2 receptor agonist quinpirole (0.5 mg/kg) in the reserpine-treated rat. SR141716 (1 mg/kg) had no effects on motor activity induced by Cl-APB (0.5 mg/kg) nor quinpirole (0.5 mg/kg) in the reserpine-treated rat. Injection of the inhibitor of endocannabinoid transport AM404 (0.1-1 mg/kg) did not affect the increase in horizontal or vertical activity elicited by L-dopa (150 mg/kg) in the reserpine-treated rat. The data suggest that both CB1 cannabinoid receptor antagonists and agonists can modulate the behavioural effects of L-dopa and may be useful for the treatment of the dyskinesia associated with long-term L-dopa treatment of Parkinson's disease.     

The role of the dorsal raphe nucleus in the development,expression, and treatment of L‐dopa‐induced dyskinesia in hemiparkinsonian rats

Convergent evidence indicates that in later stages of Parkinson's disease raphestriatal serotonin neurons compensate for the loss of nigrostriatal dopamine neurons by converting and releasing dopamine derived from exogenous administration of the pharmacotherapeutic L‐3,4‐dihydroxyphenyl‐L ‐alanine (L ‐dopa). Because the serotonin system is not equipped with dopamine autoregulatory mechanisms, it has been postulated that raphe‐mediated striatal dopamine release may fluctuate dramatically. These fluctuations may portend the development of abnormal involuntary movements called L ‐dopa‐induced dyskinesia (LID). As such, it has been hypothesized that reducing the activity of raphestriatal neurons could dampen supraphysiological stimulation of striatal dopamine receptors thereby alleviating LID. To directly address this, the current study employed the rodent model of LID to investigate the contribution of the rostral raphe nuclei (RRN) in the development, expression and treatment of LID. In the first study, dual serotonin/dopamine selective lesions of the RRN and medial forebrain bundle, respectively, verified that the RRN are essential for the development of LID. In a direct investigation into the neuroanatomical specificity of these effects, microinfusions of ±8‐OH‐DPAT into the intact dorsal raphe nucleus dose‐dependently attenuated the expression of LID without affecting the antiparkinsonian efficacy of L ‐dopa. These current findings reveal the integral contribution of the RRN in the development and expression of LID and implicate a prominent role for dorsal raphe 5‐HT1AR in the efficacious properties of 5‐HT1AR agonists. Synapse 63:610–620, 2009. © 2009 Wiley‐Liss, Inc.     

Pramipexole combined with levodopa improves motor function but reduces dyskinesia in MPTP‐treated common marmosets

Reduced expression of dyskinesia is observed in levodopa‐primed MPTP‐treated common marmosets when dopamine agonists are used to replace levodopa. We now investigate whether a combination of the D‐2/D‐3 agonist pramipexole and levodopa also reduces dyskinesia intensity while maintaining the reversal of motor disability. Drug naïve, non‐dyskinetic MPTP‐treated common marmosets were treated daily for up to 62 days with levodopa (12.5 mg/kg plus carbidopa 12.5 mg/kg p.o. BID) or pramipexole (0.04–0.3 mg/kg BID) producing equivalent reversal of motor disability and increases in locomotor activity. Levodopa alone resulted in marked dyskinesia induction but little or no dyskinesia resulted from the administration of pramipexole. From day 36, some animals were treated with a combination of levodopa (3.125–6.25 mg/kg plus carbidopa 12.5 mg/kg p.o. BID) and pramipexole (0.1–0.2 mg/kg p.o. SID). This improved motor disability to a greater extent than occurred with levodopa alone. Importantly, while dyskinesia was greater than that produced by pramipexole alone, the combination resulted in less intense dyskinesia than produced by levodopa alone. These results suggest that pramipexole could be administered with a reduced dose of levodopa to minimize dyskinesia in Parkinson's disease while maintaining therapeutic efficacy. © 2010 Movement Disorder Society     

Stimulation of cannabinoid receptors reduces levodopa-induced dyskinesia in the MPTP-lesioned nonhuman primate model of Parkinson's disease.

Long-term treatment with levodopa in Parkinson's disease results in the development of motor fluctuations, including reduced duration of antiparkinsonian action and involuntary movements, i.e., levodopa-induced dyskinesia. Cannabinoid receptors are concentrated in the basal ganglia, and stimulation of cannabinoid receptors can increase gamma-aminobutyric acid transmission in the lateral segment of globus pallidus and reduce glutamate release in the striatum. We thus tested the hypothesis that the cannabinoid receptor agonist nabilone (0.01, 0.03, and 0.10 mg/kg) would alleviate levodopa-induced dyskinesia in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) -lesioned marmoset model of Parkinson's disease. Coadministration of nabilone (0.1 mg/kg) with levodopa was associated with significantly less total dyskinesia (dyskinesia score, 12; range, 6-17; primate dyskinesia rating scale) than levodopa alone (22; range, 14-23; P < 0.05). This effect was more marked during the onset period (0-20 minutes post levodopa). There was no reduction in the antiparkinsonian action of levodopa. Furthermore, the intermediate dose of nabilone used (0.03 mg/kg) increased the duration of antiparkinsonian action of levodopa by 76%. Thus, cannabinoid receptor agonists may be useful in the treatment of motor complications in Parkinson's disease.     

左旋多巴对体外培养大鼠纹状体的神经毒性及其保护方法的研究

目的 研究左旋多巴（Ｌ－ｄｏｐａ）的神经毒性及其神经保护方法。方法 用胎盼兰染色法检测Ｌ－ｄｏｐａ和抗氧化剂还原型谷胱甘肽（ＧＳＨ）、ＮＭＤＡ受体拮抗剂ＭＫ８０１对体外培养大鼠纹状体的神经元活力的影响。结果 Ｌ－ｄｏｐａ使大鼠纹状体神经元活力明显下降（Ｐ〈０．０１）,ＧＳＨ和ＭＫ８０１可明显减轻Ｌ－ｄｏｐａ引起的纹状体神经元活力下降（Ｐ〈０．０１）。结论 Ｌ－ｄｏｐａ可能通过氧化应激和兴奋ＮＭＤＡ受体两个途径发挥其神经毒性,抗氧化剂或ＮＭＤＡ受体拮抗剂与Ｌ－ｄｏｐａ合用可能减轻Ｌ－ｄｏｐａ的神经毒性。     

Fipamezole (JP-1730) is a potent alpha2 adrenergic receptor antagonist that reduces levodopa-induced dyskinesia in the MPTP-lesioned primate model of Parkinson's disease.

Previous studies in the MPTP-lesioned primate model of Parkinson's disease have demonstrated that alpha(2) adrenergic receptor antagonists such as idazoxan, rauwolscine, and yohimbine can alleviate L-dopa-induced dyskinesia and, in the case of idazoxan, enhance the duration of anti-parkinsonian action of L-dopa. Here we describe a novel alpha(2) antagonist, fipamezole (JP-1730), which has high affinity at human alpha(2A) (K(i), 9.2 nM), alpha(2B) (17 nM), and alpha(2C) (55 nM) receptors. In functional assays, the potent antagonist properties of JP-1730 were demonstrated by its ability to reduce adrenaline-induced (35)S-GTPgammaS binding with K(B) values of 8.4 nM, 16 nM, 4.7 nM at human alpha(2A), alpha(2B), and alpha(2C) receptors, respectively. Assessment of the ability of JP-1730 to bind to a range of 30 other binding sites showed that JP-1730 also had moderate affinity at histamine H1 and H3 receptors and the serotonin (5-HT) transporter (IC(50) 100 nM to 1 microM). In the MPTP-lesioned marmoset, JP-1730 (10 mg/kg) significantly reduced L-dopa-induced dyskinesia without compromising the anti-parkinsonian action of L-dopa. The duration of action of the combination of L-dopa and JP-1730 (10 mg/kg) was 66% greater than that of L-dopa alone. These data suggest that JP-1730 is a potent alpha(2) adrenergic receptor antagonist with potential as an anti-dyskinetic agent in the treatment of Parkinson's disease.     

Beginning-of-dose and rebound worsening in MPTP-treated common marmosets treated with levodopa.

A wide range of motor fluctuations develop in Parkinson's disease (PD) patients after prolonged levodopa (L-dopa) treatment, but few experimental models exist in which these can be investigated. We report on motor fluctuations occurring in MPTP-treated common marmosets (Callithrix jacchus) treated repeatedly with L-dopa. All animals showed an improvement in motor function in response to L-dopa, and rapidly developed peak-dose dyskinesia. During the period of L-dopa action, brief periods of immobility were occasionally observed. After acute L-dopa challenge, animals exhibited a worsening of motor function before improvement, and after the beneficial response to L-dopa declined, motor performance showed rebound worsening to below-baseline values. Before L-dopa challenge and during wearing-off and rebound worsening, leg dystonias were observed. Although these findings cannot necessarily be generalized to all MPTP-treated nonhuman primates, they demonstrate that MPTP-treated marmosets show a range of different motor fluctuations analogous to those seen in PD patients chronically treated with L-dopa. Therefore, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated primates can provide a model in which the pathophysiology of treatment complications can be investigated.     

Striatal AMPA receptor binding is unaltered in the MPTP-lesioned macaque model of Parkinson's disease and dyskinesia

Long-term levodopa or dopamine agonist treatment in the MPTP-lesioned primate model of Parkinson's disease elicits dyskinesia, which is phenotypically similar to levodopa-induced dyskinesia in patients with Parkinson's disease. AMPA receptor antagonists have previously been shown to have both anti-parkinsonian and anti-dyskinetic actions in MPTP-lesioned primates, suggesting that AMPA receptor transmission is functionally overactive under these conditions. In this study, we investigated the level of striatal AMPA receptor binding in the MPTP lesioned primate using the selective AMPA ligand (3)H-(S)-5-fluorowillardiine. AMPA receptor binding was studied in non-parkinsonian, non-dyskinetic parkinsonian, and dyskinetic macaques. Striatal AMPA receptor binding was not different in any of the treatment groups (P > 0.05). Although AMPA receptor-mediated transmission is functionally overactive in Parkinson's disease and dyskinesia, changes in striatal AMPA receptor levels are not likely to be the cause of such movement disorders.     

Both short- and long-acting D-1/D-2 dopamine agonists induce less dyskinesia than L-DOPA in the MPTP-lesioned common marmoset (Callithrix jacchus)

The current concept of dyskinesia is that pulsatile stimulation of D-1 or D-2 receptors by L-DOPA or short-acting dopamine agonists is more likely to induce dyskinesia compared to long-acting drugs producing more continuous receptor stimulation. We now investigate the ability of two mixed D-1/D-2 agonists, namely pergolide (long-acting) and apomorphine (short-acting), to induce dyskinesia in drug-nai;ve MPTP-lesioned primates, compared to L-DOPA. Adult common marmosets (Callithrix jacchus) were lesioned with MPTP (2 mg/kg/day sc for 5 days) and subsequently treated with equieffective antiparkinsonian doses of L-DOPA, apomorphine, or pergolide for 28 days. L-DOPA, apomorphine, and pergolide reversed the MPTP-induced motor deficits to the same degree with no difference in peak response. L-DOPA and apomorphine had a rapid onset of action and short duration of effect producing a pulsatile motor response, while pergolide had a slow onset and long-lasting activity producing a continuous profile of motor stimulation. L-DOPA rapidly induced dyskinesia that increased markedly in severity and frequency over the course of the study, impairing normal motor activity by day 20. Dyskinesia in animals treated with pergolide or apomorphine increased steadily, reaching mild to moderate severity but remaining significantly less marked than that produced by L-DOPA. There was no difference in the intensity of dyskinesia produced by apomorphine and pergolide. These data suggest that factors other than duration of drug action may be important in the induction of dyskinesia but support the use of dopamine agonists in early Parkinson's disease, as a means of delaying L-DOPA therapy and reducing the risk of developing dyskinesia.     

L-dopa dose and the duration and severity of dyskinesia in primed MPTP-treated primates

Summary Most patients with Parkinson’s disease (PD) develop dyskinesia and other motor complications after prolonged L-dopa use. We now report on the relationship between L-dopa dose and the duration and severity of dyskinesia in L-dopa-primed MPTP-treated primates with marked nigral degeneration mimicking late stage PD. With increasing doses of L-dopa, locomotor activity increased and motor disability declined. The duration of dyskinesia following L-dopa administration increased dose-dependently, and showed a linear correlation with total locomotor activity. In addition, the time-course of dyskinesia paralleled closely that of locomotor activity in a dose-dependent manner. In contrast, severity of dyskinesia showed a non-linear correlation with total locomotor activity, low doses of L-dopa eliciting severe dyskinesia for short periods of time. The threshold for dyskinesia induction and the antiparkinsonian effects of L-dopa appear very similar in primed MPTP primates mimicking late stage PD. Reducing individual doses of L-dopa to avoid severe dyskinesia can markedly compromise the antiparkinsonian response. Our results extend the relevance of the dyskinetic MPTP-treated primate in studying the genesis of involuntary movements occurring in L-dopa treated patients with PD.     

Repeated administration of piribedil induces less dyskinesia than L-dopa in MPTP-treated common marmosets: a behavioural and biochemical investigation.

Piribedil ([1‐(3,4‐methylenedioxybenzyl)‐4‐(2‐pyrimidinyl)piperazine]; S 4200) is a dopamine agonist with equal affinity for D₂/D₃ dopamine receptors effective in treating Parkinson's disease as monotherapy or as an adjunct to levodopa (L ‐dopa). However, its ability to prime basal ganglia for the appearance of dyskinesia is unknown. We now report on the ability of repeated administration of piribedil to induce dyskinesia in drug naïve 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) ‐lesioned common marmosets compared with L ‐dopa and its actions on the direct and indirect striatal outflow pathways. Administration of piribedil (4.0–5.0 mg/kg orally) or L ‐dopa (12.5 mg/kg orally plus carbidopa 12.5 mg/kg orally twice daily) produced equivalent increases in locomotor activity and reversal of motor deficits over a 28‐day study period. Administration of L ‐dopa resulted in the progressive development of marked dyskinesia over the period of study. In contrast, administration of piribedil produced a significantly lower degree and intensity of dyskinesia. Surprisingly, piribedil caused an increase in vigilance and alertness compared to L ‐dopa, which may relate to the recently discovered α₂‐noradrenergic antagonist properties of piribedil. The behavioural differences between piribedil and L ‐dopa are reflected in the biochemical changes associated with the direct striatal output pathway. Administration of L ‐dopa or piribedil did not reverse the MPTP‐induced up‐regulation of preproenkephalin A mRNA in rostral or caudal areas of the putamen or caudate nucleus. In contrast, administration of either piribedil or L ‐dopa reversed the downregulation of preprotachykinin mRNA induced by MPTP in rostral and caudal striatum. L ‐dopa, but not Piribedil, reversed the decrease in preproenkephalin B mRNA produced by MPTP treatment. © 2002 Movement Disorder Society     

L-dopa诱导PC12细胞凋亡及相关基因表达的实验研究

目的 探讨Ｌ－ｄｏｐａ在帕金森氏病（ＰＤ）治疗中的神经毒性作用及其毒性机制。方法以ＰＣ１２细胞为多巴胺神经元的细胞模型，利用ＤＮＡ凝胶电泳及图像分析仪、ＴＵＮＥＬ法、流式细胞术及免疫荧光技术检测不同浓度的Ｌ－ｄｏｐａ对ＰＣ１２细胞的凋亡诱导作用及凋亡相关基因Ｂｃｌ－２、Ｂａｘ表达的改变。结果 ２０μｍｏｌ／Ｌ、５０μｍｏｌ／Ｌ、１００μｍｏｌ／Ｌ、１５０μｍｏｌ／Ｌ处理组凋亡率分别为２．５％、１２     

Tyrosine hydroxylase deficiency: clinical manifestations of catecholamine insufficiency in infancy.

Inborn errors of catecholamine biosynthesis are rare but of great interest as they are genetic disorders, and in some, treatment may completely reverse severe neurological abnormalities. They also provide insights into the action of the biogenic amines in the developing brain. We describe the clinical course of an infant with tyrosine hydroxylase (TOH) deficiency over a 30-month period. The parents are consanguineous, and genetic analysis revealed the infant to be homozygous for the common G698A mutation in the TOH gene. TOH deficiency can be seen as a model of pure catecholamine deficiency. Experimental evidence, reports of other disorders of biogenic amines, and our experience with this infant suggest that the symptoms of catecholamine deficiency in infancy can be broadly subdivided. Signs of dopamine deficiency include tremor, hypersensitivity to levadopa (L-dopa) therapy, oculogyric crises, akinesia, rigidity, and dystonia. Manifestations of norepinephrine deficiency include ptosis, miosis, profuse oropharyngeal secretions, and postural hypotension. Hypersensitivity to L-dopa was a particular management problem in this infant.