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Background: Intraoperative cholangiography (IOC) is a contrast-enhanced X-ray acquired during laparoscopic cholecystectomy. IOC images the biliary tree whereby filling defects, anatomical anomalies and duct injuries can be identified. In Australia, IOC are performed in over 81% of cholecystectomies compared with 20 to 30% internationally (Welfare AIoHa in Australian Atlas of Healthcare Variation, 2017). In this study, we aim to train artificial intelligence (AI) algorithms to interpret anatomy and recognise abnormalities in IOC images. This has potential utility in (a) intraoperative safety mechanisms to limit the risk of missed ductal injury or stone, (b) surgical training and coaching, and (c) auditing of cholangiogram quality. Methodology: Semantic segmentation masks were applied to a dataset of 1000 cholangiograms with 10 classes. Classes corresponded to anatomy, filling defects and the cholangiogram catheter instrument. Segmentation masks were applied by a surgical trainee and reviewed by a radiologist. Two convolutional neural networks (CNNs), DeeplabV3+ and U-Net, were trained and validated using 900 (90%) labelled frames. Testing was conducted on 100 (10%) hold-out frames. CNN generated segmentation class masks were compared with ground truth segmentation masks to evaluate performance according to a pixel-wise comparison. Results: The trained CNNs recognised all classes.. U-Net and DeeplabV3+ achieved a mean F1 of 0.64 and 0.70 respectively in class segmentation, excluding the background class. The presence of individual classes was correctly recognised in over 80% of cases. Given the limited local dataset, these results provide proof of concept in the development of an accurate and clinically useful tool to aid in the interpretation and quality control of intraoperative cholangiograms. Conclusion: Our results demonstrate that a CNN can be trained to identify anatomical structures in IOC images. Future performance can be improved with the use of larger, more diverse training datasets. Implementation of this technology may provide cholangiogram quality control and improve intraoperative detection of ductal injuries or ductal injuries. Graphical abstract:

BackgroundPopulation-based DNA screening for medically actionable conditions has the potential to improve public health by enabling early detection, treatment and/or prevention; however, public attitudes and willingness to participate in DNA screening have not been well investigated.MethodsWe presented a scenario to members of the Australian public, randomly selected from the electoral roll via the Australian Survey of Societal Attitudes, describing an adult population DNA screening programme currently under development, to detect risk of medically actionable cancers and heart disease. We asked questions regarding willingness to participate and pay, preferred delivery methods and concerns.ResultsWe received 1060 completed questionnaires (response rate 23%, mean age 58 years). The vast majority (>92%) expressed willingness to undertake DNA screening. When asked about the optimal age of screening, most (56%) favoured early adulthood (aged 18–40 years) rather than at birth or childhood. Many respondents would prefer samples and data be kept for re-screening (36%) or research use (43%); some preferred samples to be destroyed (21%). Issues that decrease likelihood of participation included privacy (75%) and insurance (86%) implications.ConclusionOur study demonstrates public willingness to participate in population DNA screening in Australia, and identifies barriers to participation, to be addressed in the design of screening programmes. Results are informing the development of a pilot national DNA screening programme.

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Chest x-rays are widely used in clinical practice; however, interpretation can be hindered by human error and a lack of experienced thoracic radiologists. Deep learning has the potential to improve the accuracy of chest x-ray interpretation. We therefore aimed to assess the accuracy of radiologists with and without the assistance of a deep-learning model.

Disease modification in Parkinson’s disease (PD) is an unmet medical need. In the current study, we evaluated trehalose, a safe and well-tolerated disaccharide that has previously demonstrated efficacy in rodent models of neurodegenerative diseases, including PD. In a rat model of PD, based on delivery of adeno-associated virus serotype 1/2 containing the mutated human A53T α-synuclein gene (AAV1/2-hourA53T-aSyn) to the substantia nigra (SN), we showed that rats administered trehalose (2.67 g/kg per day, by mouth) for 6 weeks had less forelimb asymmetry (93% reduction) and higher striatal dopamine (54% increase) compared with rats receiving vehicle. In a pharmacokinetic study, we determined that efficacy was associated with plasma Cmaxof 8900 ng/ml and area under the curve from time 0 to infinity (AUC0–inf) of 11,136 hour⋅ng/ml. We then showed, in macaques, that oral administration of trehalose (2.67 g/kg per day) produced plasma exposures of similar magnitude, with plasma Cmaxof 10,918 ng/ml and AUC0–infof 27,445 hour⋅ng/ml. In a macaque model of PD, also based on delivery of AAV1/2-hourA53T-aSyn to the SN, trehalose (2.67 g/kg per day, by mouth), administered for 142 days, produced higher striatal dopamine (by 39%) and dopamine transporter levels (by 50%), compared with macaques receiving vehicle. In neither model did trehalose treatment prevent loss of tyrosine hydroxylase (TH) positive (TH+ve) cells in the SN or alter α-synuclein levels in the striatum. These studies demonstrated that trehalose reduces striatal dopaminergic deficits in a rodent and macaque model of synucleinopathy in PD. Furthermore, we have determined the pharmacokinetic parameters associated with efficacy, and thus defined exposures to target in future clinical trials.

Dyskinesia is a common motor complication associated with the use of levodopa to treat Parkinson’s disease. Numerous animal studies in mice, rats, and nonhuman primates have demonstrated that the N-methyl-d-aspartate antagonist, amantadine, dose dependently reduces levodopa-induced dyskinesia (LID). However, none of these studies characterized the amantadine plasma concentrations required for a therapeutic effect. This study evaluates the pharmacokinetic (PK)/pharmacodynamic (PD) relationship between amantadine plasma concentrations and antidyskinetic efficacy across multiple species to define optimal therapeutic dosing. The PK profile of amantadine was determined in mice, rats, and macaques. Efficacy data from the 6-hydroxydopamine rat and the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine macaque model of LID, along with previously published antidyskinetic efficacy data, were used to establish species-specific PK/PD relationships using a direct-effect maximum possible effect model. Results from the PK/PD model were compared with amantadine plasma concentrations and antidyskinetic effect in a phase 2 study in patients with Parkinson’s disease treated with ADS-5102, an extended-release amantadine capsule formulation. Outcomes from each of the species evaluated indicate that the EC50of amantadine for reducing dyskinesia range from 1025 to 1633 ng/ml (1367 ng/ml for an all-species model). These data are consistent with the mean amantadine plasma concentrations observed in patients with Parkinson’s disease (∼1500 ng/ml) treated with ADS-5102 at doses that demonstrated a statistically significant reduction in dyskinesia. These results demonstrate that the EC50of amantadine for reducing dyskinesia is consistent across multiple species and supports a plasma concentration target of ∼1400 ng/ml to achieve therapeutic efficacy.

A major challenge in Parkinson disease (PD) will be to turn an emerging and expanding pipeline of novel disease-modifying candidate compounds into therapeutics. Novel targets need in vivo validation, and candidate therapeutics require appropriate preclinical platforms on which to define potential efficacy and target engagement before advancement to clinical development. We propose that α-synuclein (α-syn)-based mammalian models will be crucial for this process. Here, we review α-syn transgenic mouse models, viral vector models of α-syn overexpression and models of 'prion-like' spread of α-syn, and describe how each of these model types may contribute to PD drug discovery. We conclude by presenting our opinion on how to use a combination of these models through the late-stage preclinical, proof-of-principle investigation of novel therapeutics.

Depression is a common concomitant of pancreatic cancer, and, because it often occurs before the cancer is diagnosed, its occurrence is likely to be intrinsic to the condition rather than a reaction to such a diagnosis. Because pancreatic cancer is associated with a very high mortality, its early detection is a key task. We therefore review relevant literature to determine whether the depression is prototypically distinctive and whether its identification might lead to earlier diagnosis of pancreatic cancer. We report on the epidemiology and prognosis of pancreatic cancer and on the prevalence, description, and possible mechanisms involved for the occurrence of any associated depressive state, before reviewing the comparative utility of depression in relation to other risk factors in aiding diagnosis. Published studies fail to identify any distinct depressive prototypic phenotype to depression associated with pancreatic cancer. Although it is a relatively common concomitant of pancreatic cancer, the utility of depression as a marker of the condition is not suggested from a key study evaluating its contribution in relation to other symptoms and risk factors.

How do we create workplaces that are positive environments, where staff enjoy coming to work, absentee rates are low, and children are happy? These are important questions for providers who want to keep up high standards, retain staff, and to stay popular with parents.

Striatal dopamine deficiency is the core feature of the pathology of Parkinson’s disease (PD), and dopamine replacement with l-3,4-dihydroxyphenylalanine (l-DOPA) is the mainstay of PD treatment. Unfortunately, chronic l-DOPA administration is marred by the emergence of dyskinesia and wearing-off. Alternatives to l-DOPA for alleviation of parkinsonism are of interest, although none can match the efficacy of l-DOPA to date. Catechol-O-methyltransferase and monoamine oxidase inhibitors are currently used to alleviate wearing-off, but they do not increase “on-time” without exacerbating dyskinesia. Alternate approaches to dopamine replacement in parkinsonism generally (and to wearing-off and dyskinesia, specifically) are therefore urgently needed. Inasmuch as they increase synaptic dopamine levels, dopamine transporter (DAT) inhibitors, whether they are selective or have actions on noradrenaline or serotonin transporters, theoretically represent an attractive way to alleviate parkinsonism per se and potentially enhance l-DOPA antiparkinsonian action (provided that sufficient dopamine terminals remain within the striatum). Several nonhuman primate studies and clinical trials have been performed to evaluate the potential of DAT inhibitors for PD. In this article, we review nonhuman primate studies and clinical trials, we summarize the current knowledge of DAT inhibitors in PD, and we propose a hypothesis as to how tailoring the selectivity of DAT inhibitors might maximize the benefits of DAT inhibition in PD.

For the first time, we apply a high-speed imaging technique to record the activity of acoustically driven cavitation bubbles (86 kHz) on micropatterned surfaces with hydrophobic and hydrophilic stripes. The width of the hydrophobic stripes lies between 3.5 and 115 μm. This work provides the first direct visualization of the preferential location of bubbles on the hydrophobic areas of the patterns. The results confirm our previous prediction that surface cavitation strongly depends on the surface energy of the irradiated substrate. The observations show a remarkable effect of the stripe width on the size, movement, growth, splitting, and multiplying of the bubbles. The high-speed imaging also reveals that there is a minimal width of the hydrophobic stripes that allows bubble attraction and formation. Our observations are supported by a theoretical approach based on the forces acting on the bubbles.

l-3,4-Dihydroxyphenylalanine (l-DOPA) remains the most effective symptomatic treatment of Parkinson’s disease (PD). However, long-term administration of l-DOPA is marred by the emergence of abnormal involuntary movements, i.e., l-DOPA-induced dyskinesia (LID). Years of intensive research have yielded significant progress in the quest to elucidate the mechanisms leading to the development and expression of dyskinesia and maintenance of the dyskinetic state, but the search for a complete understanding is still ongoing. Herein, we summarize the current knowledge of the pharmacology of LID in PD. Specifically, we review evidence gathered from postmortem and pharmacological studies, both preclinical and clinical, and discuss the involvement of dopaminergic and nondopaminergic systems, including glutamatergic, opioid, serotonergic, γ-aminobutyric acid (GABA)-ergic, adenosine, cannabinoid, adrenergic, histaminergic, and cholinergic systems. Moreover, we discuss changes occurring in transcription factors, intracellular signaling, and gene expression in the dyskinetic phenotype. Inasmuch as a multitude of neurotransmitters and receptors play a role in the etiology of dyskinesia, we propose that to optimally alleviate this motor complication, it may be necessary to develop combined treatment approaches that will target simultaneously more than one neurotransmitter system. This could be achieved via three ways as follows: 1) by developing compounds that will interact simultaneously to a multitude of receptors with the required agonist/antagonist effect at each target, 2) by targeting intracellular signaling cascades where the signals mediated by multiple receptors converge, and/or 3) to regulate gene expression in a manner that has effects on signaling by multiple pathways

l-DOPA-induced dyskinesia remains an unmet challenge in the treatment of Parkinson's disease (PD). Here, we investigate the potential antidyskinetic efficacy of 3-([4-(4-chlorophenyl)piperazin-1-yl]methyl)-1H-pyrrolo[2,3-b]pyridine (l-745,870), a potent and selective dopamine D4receptor antagonist with a good toxicology profile and an excellent safety and tolerability record in phase I/II clinical studies, for non-PD indications. Six macaques were rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration. After induction of stable and marked dyskinesia, animals were administered acute challenges of l-745,870in combination with l-DOPA. To guarantee D4selectivity at the doses used in the study, we determined the plasma, cerebrospinal fluid, and brain levels of l-745,870. Coadministration of l-745,870(1 mg/kg) and l-DOPA significantly reduced the severity of dyskinesia, by up to 59%, in comparison with l-DOPA alone (P< 0.01). l-745,870had no effect on the duration of antiparkinsonian benefit (ON-time) (P> 0.05). However, l-745,870(1 mg/kg) significantly increased the duration of ON-time without disabling dyskinesia (+204%; P< 0.001) and decreased duration of ON-time with disabling dyskinesia compared with l-DOPA alone (−56%; P< 0.01). Brain levels of l-745,870(∼600 ng/g) were within the range at which l-745,870provides selective D4receptor antagonism. Plasma levels were comparable with those demonstrated to be well tolerated in human studies. These data suggest that selective D4receptor antagonists represent a potential therapeutic approach for l-DOPA-induced dyskinesia. It is noteworthy that l-745,870has already undergone significant clinical development, has an excellent profile for a therapeutic candidate, and could be advanced rapidly to phase IIa clinical studies for dyskinesia in PD.

L-DOPA-induced dyskinesia remains an unmet challenge in the treatment of Parkinson's disease (PD). Here, we investigate the potential antidyskinetic efficacy of 3-([4-(4-chlorophenyl)piperazin-1-yl]methyl)-1H-pyrrolo[2,3-b]pyridine (L-745,870), a potent and selective dopamine D(4) receptor antagonist with a good toxicology profile and an excellent safety and tolerability record in phase I/II clinical studies, for non-PD indications. Six macaques were rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration. After induction of stable and marked dyskinesia, animals were administered acute challenges of L-745,870 in combination with L-DOPA. To guarantee D(4) selectivity at the doses used in the study, we determined the plasma, cerebrospinal fluid, and brain levels of L-745,870. Coadministration of L-745,870 (1 mg/kg) and L-DOPA significantly reduced the severity of dyskinesia, by up to 59%, in comparison with L-DOPA alone (P < 0.01). L-745,870 had no effect on the duration of antiparkinsonian benefit (ON-time) (P > 0.05). However, L-745,870 (1 mg/kg) significantly increased the duration of ON-time without disabling dyskinesia (+204%; P < 0.001) and decreased duration of ON-time with disabling dyskinesia compared with L-DOPA alone (-56%; P < 0.01). Brain levels of L-745,870 (∼600 ng/g) were within the range at which L-745,870 provides selective D(4) receptor antagonism. Plasma levels were comparable with those demonstrated to be well tolerated in human studies. These data suggest that selective D(4) receptor antagonists represent a potential therapeutic approach for L-DOPA-induced dyskinesia. It is noteworthy that L-745,870 has already undergone significant clinical development, has an excellent profile for a therapeutic candidate, and could be advanced rapidly to phase IIa clinical studies for dyskinesia in PD.

Ultrasound has become an increasingly popular tool in the modification of metal surfaces, imbuing them with various desired characteristics and functionalities. The exact role played by ultrasound in such processes remains largely speculative and thus requires clarification. In this study, aluminum was taken as a model metal to probe the nature of the surface modification, focusing on both chemical and physical changes. Using metal plates as substrates, the formation of a characteristic porous surface structure was ascertained to arise from a purely thermal mechanism, with the ultrasound providing an inhibitory influence when compared with controlled experiments matching the thermal conditions of sonication. No beneficial effect was observed through sonication, with regards to surface texture, porosity, and electrochemistry. However, for metal powders, a pronounced change in the phase composition was observed following ultrasonic exposure, largely attributed to the growth of bayerite from the surface. The immobilization of the powder on a thin epoxy film nullified such effects. This suggests that the changes in phase composition are due to the effect of ultrasound-induced mechanical stirring and high speed particle motion on the dissolution and reprecipitation of the metal oxide and hydrated oxide species. This work is of significant value to researchers both in materials science and in sonochemistry.

l-DOPA remains the most effective treatment for Parkinson’s disease (PD). However, long-term administration of l-DOPA is compromised by complications, particularly dyskinesia. Serotonergic type 1A (5-HT1A) receptor agonists and serotonergic type 2A (5-HT2A) receptor antagonists were, until recently, considered to be promising therapies against dyskinesia. However, there have been some recent high-profile failures in clinical trials, notably with sarizotan, and it seems that these classes of drugs may also impair l-DOPA antiparkinsonian efficacy. A simple explanation for the loss of antiparkinsonian benefit might be lack of good selectivity of these compounds for their respective targets, particularly with respect to off-target actions on dopaminergic receptors or poor dose selection in clinical studies. However, such explanations do not hold broadly when considering the actions of all compounds studied to date, whether in animal models or clinical trials. Here, we review 5-HT1Aand 5-HT2Areceptor function in PD and provide an anatomically based rationale as to why in some instances 5-HT1A- and 5-HT2A-modulating drugs might worsen parkinsonism, in addition to reducing dyskinesia. We propose that, in addition to selectivity for specific receptor subtypes, to target 5-HT1Aand 5-HT2Areceptors to alleviate dyskinesia, without worsening parkinsonism, it will be necessary to develop compounds that display anatomical selectivity, targeting corticostriatal transmission, while avoiding 5-HT receptors on ascending serotonergic and dopaminergic inputs from the raphe and substantia nigra, respectively.

L-DOPA remains the most effective treatment for Parkinson's disease (PD). However, long-term administration of L-DOPA is compromised by complications, particularly dyskinesia. Serotonergic type 1A (5-HT(1A)) receptor agonists and serotonergic type 2A (5-HT(2A)) receptor antagonists were, until recently, considered to be promising therapies against dyskinesia. However, there have been some recent high-profile failures in clinical trials, notably with sarizotan, and it seems that these classes of drugs may also impair l-DOPA antiparkinsonian efficacy. A simple explanation for the loss of antiparkinsonian benefit might be lack of good selectivity of these compounds for their respective targets, particularly with respect to off-target actions on dopaminergic receptors or poor dose selection in clinical studies. However, such explanations do not hold broadly when considering the actions of all compounds studied to date, whether in animal models or clinical trials. Here, we review 5-HT(1A) and 5-HT(2A) receptor function in PD and provide an anatomically based rationale as to why in some instances 5-HT(1A)- and 5-HT(2A)-modulating drugs might worsen parkinsonism, in addition to reducing dyskinesia. We propose that, in addition to selectivity for specific receptor subtypes, to target 5-HT(1A) and 5-HT(2A) receptors to alleviate dyskinesia, without worsening parkinsonism, it will be necessary to develop compounds that display anatomical selectivity, targeting corticostriatal transmission, while avoiding 5-HT receptors on ascending serotonergic and dopaminergic inputs from the raphe and substantia nigra, respectively.

The terms ‘tolerance’ and ‘poop out’ are commonly applied to describe the progressive loss of effectiveness of a previously effective antidepressant and where the individual may be a rapid metabolizer of those drugs as a consequence of possessing certain polymorphisms of P450 (CYP) liver enzymes, especially CYP2D6 and CYP2C19. As the antidepressant desvenlafaxine is not metabolized by those enzymes, it might be hypothesized that it would be less likely to be associated with tolerance or poop out, even for patients whose genotyping pattern is indicative of rapid metabolizing. In this study, we report on five patients who had a historical pattern suggestive of tolerance to other antidepressant drugs, whose genotyping test indicated that they were CYP2C19 rapid metabolizers, and who experienced ‘poop out’ again when commenced on desvenlafaxine. Although desvenlafaxine is theoretically an option in patients with a history of tolerance to antidepressants, these case reports indicate that this drug may not necessarily overcome the problem of tolerance in rapid metabolizing patients.

Dopaminergic therapies remain the most efficacious symptomatic treatments for Parkinson’s disease (PD) but are associated with motor complications, including dyskinesia, and nonmotor complications, such as psychosis, impulse control disorders (ICD), and dopamine dysregulation syndrome (DDS). Nondopaminergic neurotransmitter systems, including the endocannabinoid system, are probably critical to the development of these complications. The role of fatty acid amide hydrolase (FAAH) in mediating l-3,4-dihydroxyphenylalanine (l-DOPA)-induced behaviors was explored in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned marmoset model of PD. Pharmacodynamic and locomotor effects of the selective FAAH inhibitor [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate (URB597) were assessed via bioanalytical (liquid chromatography-tandem mass spectrometry) and behavioral observation approaches. URB597 (3, 10, 30, or 60 mg/kg p.o.) increased plasma levels of the FAAH substrates N-arachidonoyl ethanolamide (anandamide), N-oleoyl ethanolamide, and N-palmitoyl ethanolamide by 10.3 ± 0.3-, 7.8 ± 0.2-, and 1.8 ± 0.1-fold (mean of URB597 groups ± S.E.M.), respectively, compared with vehicle (all p< 0.001) 4 h after administration. Treatment with l-DOPA (20 mg/kg s.c.) alleviated parkinsonism but elicited dyskinesia, psychosis-like-behaviors and hyperactivity, a potential correlate of ICD and DDS. During the 2 to 4 h after l-DOPA, corresponding to 4 to 6 h after URB597 administration, URB597 reduced total l-DOPA-induced activity and the magnitude of hyperactivity by 32 and 52%, respectively, to levels equivalent to those seen in normal animals. Treatment with URB597 (10 mg/kg p.o.) did not modify the antiparkinsonian actions of l-DOPA or l-DOPA-induced dyskinesia and psychosis. URB597 did not alter plasma l-DOPA levels and was without behavioral effects when administered alone. Inhibition of FAAH may represent a novel approach to reducing l-DOPA-induced side effects, such as ICD and DDS, while maintaining the antiparkinsonian benefits of l-DOPA treatment.

Dopaminergic therapies remain the most efficacious symptomatic treatments for Parkinson's disease (PD) but are associated with motor complications, including dyskinesia, and nonmotor complications, such as psychosis, impulse control disorders (ICD), and dopamine dysregulation syndrome (DDS). Nondopaminergic neurotransmitter systems, including the endocannabinoid system, are probably critical to the development of these complications. The role of fatty acid amide hydrolase (FAAH) in mediating l-3,4-dihydroxyphenylalanine (L-DOPA)-induced behaviors was explored in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned marmoset model of PD. Pharmacodynamic and locomotor effects of the selective FAAH inhibitor [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate (URB597) were assessed via bioanalytical (liquid chromatography-tandem mass spectrometry) and behavioral observation approaches. URB597 (3, 10, 30, or 60 mg/kg p.o.) increased plasma levels of the FAAH substrates N-arachidonoyl ethanolamide (anandamide), N-oleoyl ethanolamide, and N-palmitoyl ethanolamide by 10.3 ± 0.3-, 7.8 ± 0.2-, and 1.8 ± 0.1-fold (mean of URB597 groups ± S.E.M.), respectively, compared with vehicle (all p < 0.001) 4 h after administration. Treatment with L-DOPA (20 mg/kg s.c.) alleviated parkinsonism but elicited dyskinesia, psychosis-like-behaviors and hyperactivity, a potential correlate of ICD and DDS. During the 2 to 4 h after L-DOPA, corresponding to 4 to 6 h after URB597 administration, URB597 reduced total L-DOPA-induced activity and the magnitude of hyperactivity by 32 and 52%, respectively, to levels equivalent to those seen in normal animals. Treatment with URB597 (10 mg/kg p.o.) did not modify the antiparkinsonian actions of L-DOPA or L-DOPA-induced dyskinesia and psychosis. URB597 did not alter plasma L-DOPA levels and was without behavioral effects when administered alone. Inhibition of FAAH may represent a novel approach to reducing L-DOPA-induced side effects, such as ICD and DDS, while maintaining the antiparkinsonian benefits of L-DOPA treatment.

Long-term motor complications of dopamine replacement, such as l-DOPA-induced dyskinesia (LID) and reduced quality of l-DOPA action, remain obstacles in the treatment of Parkinson's disease. Dysfunctional glutamatergic neurotransmitter systems have been observed in both the untreated parkinsonian and dyskinetic states and represent novel targets for treatment. Here, we assess the pharmacokinetic profile and corresponding pharmacodynamic effects on behavior of the orally active, selective metabotropic glutamate receptor type 5 (mGlu5) antagonist, 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) (as the hydrochloride salt) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned macaque. Six parkinsonian, MPTP-lesioned cynomolgus monkeys, with established LID, were administered acute challenges with MTEP (4.5–36 mg/kg p.o.) or vehicle, either alone or in combination with l-DOPA (33 ± 1 mg/kg p.o.). Motor activity, parkinsonian disability, and dyskinesia were assessed for a 6-h period. Plasma drug levels were assessed by liquid chromatography-tandem mass spectrometry. MTEP had no antiparkinsonian action as monotherapy. However, administration of l-DOPA in combination with MTEP (36 mg/kg) reduced peak dose LID by 96%. Moreover, although total on-time (duration for which l-DOPA exerted an antiparkinsonian effect) was not significantly reduced, MTEP (36 mg/kg) reduced the duration of on-time with disabling LID by 70% compared with that for l-DOPA alone. These effects were associated with a peak plasma concentration of 20.9 μM and an area under the curve from 0 to 24 h of 136.1 h · μM (36 mg/kg). Although total on-time was not reduced, the peak antiparkinsonian benefit of l-DOPA/MTEP (36 mg/kg) was less than that with l-DOPA alone. Selective mGlu5 inhibitors may have significant potential to ameliorate dyskinesia, but care should be taken to ensure that such effects do not come at the expense of the peak antiparkinsonian benefit of l-DOPA.

Long-term motor complications of dopamine replacement, such as L-DOPA-induced dyskinesia (LID) and reduced quality of L-DOPA action, remain obstacles in the treatment of Parkinson's disease. Dysfunctional glutamatergic neurotransmitter systems have been observed in both the untreated parkinsonian and dyskinetic states and represent novel targets for treatment. Here, we assess the pharmacokinetic profile and corresponding pharmacodynamic effects on behavior of the orally active, selective metabotropic glutamate receptor type 5 (mGlu5) antagonist, 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) (as the hydrochloride salt) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned macaque. Six parkinsonian, MPTP-lesioned cynomolgus monkeys, with established LID, were administered acute challenges with MTEP (4.5-36 mg/kg p.o.) or vehicle, either alone or in combination with L-DOPA (33 +/- 1 mg/kg p.o.). Motor activity, parkinsonian disability, and dyskinesia were assessed for a 6-h period. Plasma drug levels were assessed by liquid chromatography-tandem mass spectrometry. MTEP had no antiparkinsonian action as monotherapy. However, administration of L-DOPA in combination with MTEP (36 mg/kg) reduced peak dose LID by 96%. Moreover, although total on-time (duration for which L-DOPA exerted an antiparkinsonian effect) was not significantly reduced, MTEP (36 mg/kg) reduced the duration of on-time with disabling LID by 70% compared with that for L-DOPA alone. These effects were associated with a peak plasma concentration of 20.9 microM and an area under the curve from 0 to 24 h of 136.1 h x microM (36 mg/kg). Although total on-time was not reduced, the peak antiparkinsonian benefit of l-DOPA/MTEP (36 mg/kg) was less than that with L-DOPA alone. Selective mGlu5 inhibitors may have significant potential to ameliorate dyskinesia, but care should be taken to ensure that such effects do not come at the expense of the peak antiparkinsonian benefit of L-DOPA.

Parkinson disease (PD) is a disorder with a substantive period before the emergence of motor symptoms, during which significant dopaminergic neuronal loss is counterbalanced by endogenous compensatory mechanisms. Many potential compensatory mechanisms have now been proposed; these are both dopaminergic, focused on enhancing effects or exposure to existing dopamine, and nondopaminergic, being focused on reducing activity of the indirect striatal output pathway. Compensatory mechanisms can potentially postpone and reduce the severity of parkinsonian symptoms, and contribute to the benefit provided by a symptomatic therapy, thus offering targets for novel therapeutics. However, enhancement of certain compensatory mechanisms may produce problems when subsequent therapies are initiated, e.g., the development of motor complications with levodopa. Supporting endogenous compensatory mechanisms, to delay or reverse apparent disease progression, is a novel and attractive “disease-modifying” approach to PD. Such actions may contribute to the apparent disease-modifying benefit of initiating early treatment with levodopa or rasagiline, as suggested by the ELLDOPA and TEMPO studies.

The mechanisms underlying actions of dihydroxyphenylalanine (l-DOPA) in Parkinson’s disease remain to be fully elucidated. Noradrenaline formed from l-DOPA may stimulate α1-adrenoceptors. We assessed the involvement of α1-adrenoceptors in actions of l-DOPA in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned macaques. In each animal, the minimal dose of l-DOPA required to alleviate parkinsonian symptoms was defined (12.5–25 mg/kg p.o.). The effects of coadministration of the α1-adrenoceptor antagonist prazosin ([4-(4-amino-6,7-dimethoxy-quinazolin-2-yl) piperazin-1-yl]-(2-furyl)methanone) on motor activity, parkinsonism, and dyskinesia were assessed. Antiparkinsonian benefit was accompanied by mild dyskinesia. l-DOPA also elicited hyperactivity, i.e., activity greater than that seen in normal animals. Coadministration of prazosin (0.16–0.63 mg/kg p.o.) with l-DOPA did not significantly affect either its antiparkinsonian actions or dyskinesia. However, prazosin significantly and dose-dependently attenuated l-DOPA-induced activity, reducing it to a level equivalent to that of normal animals. More specifically, during periods of pronounced l-DOPA-induced activity, prazosin attenuated the total and duration of activity by 80 and 76%, respectively. These actions of prazosin were expressed in the absence of sedation. Although activation of α1-adrenoceptors plays no major role in the antiparkinsonian and dyskinetic effects of l-DOPA per se, it does contribute to the induction of hyperactivity. α1-Adrenoceptors may be involved in pathological responses to l-DOPA treatment, including the dopamine dysregulation syndrome.

The mechanisms underlying actions of dihydroxyphenylalanine (L-DOPA) in Parkinson's disease remain to be fully elucidated. Noradrenaline formed from L-DOPA may stimulate alpha(1)-adrenoceptors. We assessed the involvement of alpha(1)-adrenoceptors in actions of L-DOPA in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned macaques. In each animal, the minimal dose of L-DOPA required to alleviate parkinsonian symptoms was defined (12.5-25 mg/kg p.o.). The effects of coadministration of the alpha(1)-adrenoceptor antagonist prazosin ([4-(4-amino-6,7-dimethoxy-quinazolin-2-yl) piperazin-1-yl]-(2-furyl)methanone) on motor activity, parkinsonism, and dyskinesia were assessed. Antiparkinsonian benefit was accompanied by mild dyskinesia. L-DOPA also elicited hyperactivity, i.e., activity greater than that seen in normal animals. Coadministration of prazosin (0.16-0.63 mg/kg p.o.) with L-DOPA did not significantly affect either its antiparkinsonian actions or dyskinesia. However, prazosin significantly and dose-dependently attenuated L-DOPA-induced activity, reducing it to a level equivalent to that of normal animals. More specifically, during periods of pronounced L-DOPA-induced activity, prazosin attenuated the total and duration of activity by 80 and 76%, respectively. These actions of prazosin were expressed in the absence of sedation. Although activation of alpha(1)-adrenoceptors plays no major role in the antiparkinsonian and dyskinetic effects of L-DOPA per se, it does contribute to the induction of hyperactivity. alpha(1)-Adrenoceptors may be involved in pathological responses to L-DOPA treatment, including the dopamine dysregulation syndrome.

The sonoluminescence emission and sonochemical efficiency of a typical laboratory scale, high-frequency standing wave reactor (355 kHz), stimulated by low-frequency pulses (20 kHz) has been investigated in the presence and absence of some water-soluble solutes, namely, propanol and polyethylene oxide. It has been found that, although dual-frequency sonication causes a decrease in the integrated sonoluminescence intensity and sonochemical efficiency in water, in the presence of solutes, a significant enhancement in activity could be attained. This enhancement effect is ascribed, in part, to changes in the extent of bubble coalescence brought about by the water-soluble solutes.

Sonoluminescence emission, sonochemiluminescence from luminol and the sonochemical yield of hydrogen peroxide were studied under a dual frequency field combining low-frequency (20 kHz) and high-frequency (355 kHz) ultrasound. Under certain conditions it was found that a synergistic enhancement of both sonoluminescence and sonochemical processes could be attained. Ultrasound parameters including pulsing conditions and sonication time were found to sensitively influence the efficiency of the dual-frequency mode operation. Possible mechanisms responsible for the dual-frequency effects are discussed.

Sonoluminescence (SL) originating from a dual-frequency ultrasound system, in water and in the presence of certain water-soluble solutes, was investigated. The ultrasound arrangement consisted of a 20-kHz horn, vertically opposing a high-frequency transducer operating at 355 or 1056 kHz. It was found that the power setting of the high frequency sensitively determined the SL yield of the dual-frequency system. A significant synergy effect was observed at low power, while at high power the dual-frequency mode attenuated the SL signal. Additives representing three different classes of solutes, namely, surfactants, alcohols, and polymers, were studied, with respect to their effect on the intensity of SL. The results obtained reinforce those from previous single-frequency studies, while simultaneously providing some insight into cavitation under dual-frequency conditions. It was demonstrated that the synergy effect of dual-frequency ultrasound on SL observed in water could be further enhanced in the presence of these solutes.

The authors report on the psychometric characteristics and clinical efficacy of two versions of a recently developed screening measure of depression (the DMI-18 and DMI-10) in the cardiac population. Patients with acute coronary syndrome or heart failure (N = 322) completed the DMI measures, psychosocial questionnaires, and a semistructured clinical interview during the hospital stay. The DMI-18 and DMI-10 measures have adequate psychometric properties, demonstrating high sensitivity and specificity when evaluated against clinical judgment based on a semistructured interview. The DMI-18 and DMI-10 are appropriate for use as screening instruments in cardiac patients.

Innovative drug delivery in Parkinson’s disease (PD) has the potential to reduce or avoid many side effects of current treatment, such as wearing-off type fluctuations, dyskinesia, on-off phenomena or bouts of motor freezing. The traditional orally administered formulations of l-dihydroxyphenylalanine combined with a peripheral aromatic acid decarboxylase inhibitor remain the mainstay of treatments for PD. However, such combination therapies have been further formulated to extend their duration of action by including a catechol-O-methyltransferase inhibitor. Preventing the breakdown of dopamine has also been achieved by monoamine oxidase-B inhibition; this approach now having been formulated for sublingual use (Zelapar®, Valeant Pharmaceuticals). An alternative approach bypasses the oral route of administration and instead relies on continuous duodenal infusion (Duodopa®, Solvay, NeoPharma AB) for better therapeutic effect. The clinical use of dopamine agonists as antiparkinsonian drugs now incorporates a variety of delivery techniques. For example, apomorphine, which relies on parenteral administration for maximum bioavailability, may be delivered via rectal, intranasal, sublingual and subcutaneous (e.g., Apokyn®, Mylan Bertek) routes. Meanwhile, rotigotine and lisuride have both been formulated for delivery via skin patches. Finally, the authors examine more experimental delivery techniques, including the delivery of genes via viral vectors or liposomes, intracranial transplant of a variety of cells and of l-dihydroxyphenylalanine by prodrug-dispensing liposomes or pulmonary delivery (AIR®, Alkermes). The advent and application of these varied technologies will help encourage patient-specific means of treatment for PD.

Some carriers of a “premutation” allele of the FMR1gene develop late‐onset tremor/ataxia. We conducted a magnetic resonance imaging volumetric study in an unselected sample of eight older male premutation carriers. Volumetric measures, including total brain volume, and the volumes of cerebrum, cerebellum, and cerebral cortex all were significantly reduced in premutation carriers compared with similar data from 21 age‐matched normal controls. Total brain and cerebral volumes were significantly related to the number of CGG repeats in the FMR1gene. Moreover, increased hippocampal volume indicates this premutation may account for both neurodegenerative and neurodevelopmental changes. Ann Neurol 2005;58:326–330

This case report describes a 59-year-old male who presented with headaches, seizures and hypertension followed by coma. Initial magnetic resonance imaging showed T2 hyperintensities typical of Hypertensive Encephalopathy (HE), the follow up scans showed diffusion-weighted imaging (DWI) hyperintensities which is a rare finding in HE. DWI hyperintensities are typically suggestive of areas of cytotoxic damage, and the presence of these changes makes this case unusual, since the pathogenesis of HE is usually due to vasogenic oedema rather than cytotoxic damage of the brain tissue.

Levetiracetam (LEV) (Keppra; UCB Pharma, Brussels, Belgium) has recently been reported to have antidyskinetic activity against levodopa (L-DOPA)-induced dyskinesia in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned marmoset and macaque models of Parkinson's disease. Amantadine is frequently used as adjunctive therapy for L-DOPA-induced dyskinesia, but adverse effects limit its clinical utility. The current study was designed to investigate whether LEV can potentiate the antidyskinetic action of amantadine. The antiparkinsonian and antidyskinetic effects of LEV (13 and 60 mg/kg) and amantadine (0.01, 0.03, 0.1, and 0.3 mg/kg), administered alone and in combination, were assessed in the MPTP-lesioned marmoset model of L-DOPA-induced dyskinesia (n = 12). LEV (60 mg/kg) and amantadine (0.3 mg/kg) administered alone significantly reduced l-DOPA-induced dyskinesia without compromising the antiparkinsonian action of l-DOPA. Lower doses were without any significant effects. The combination of LEV (60 mg/kg) and amantadine (0.01, 0.03, 0.1, and 0.3 mg/kg) significantly decreased dyskinesia severity, without compromising the antiparkinsonian action of L-DOPA, more efficaciously than LEV or amantadine monotherapy. These results support the concept that normalization of different pathophysiological mechanisms (i.e., altered synchronization between neurons and enhanced N-methyl-D-aspartate transmission) has a greater efficacy. Combined LEV/amantadine therapy might be useful as an adjunct to L-DOPA to treat dyskinetic side effects and to expand the population of Parkinson's disease patients who benefit from treatment with amantadine alone.

These studies evaluated the potential antiparkinsonian properties of the novel dopamine D3/D2receptor agonist S32504 [(+)-trans-3,4,4 a,5,6, 10 b-hexahydro-9-carbamoyl-4-propyl-2 H-naphth[1,2-b]-1,4-oxazine] in comparison with those of the clinically employed agonist ropinirole. In rats with a unilateral, 6-hydroxydopamine lesion of the substantia nigra, S32504 (0.0025–0.04 mg/kg, s.c.) more potently elicited contralateral rotation than S32601 [(-)-trans-3,4,4 a,5,6, 10 b-hexahydro-9-carbamoyl-4-propyl-2 H-naphth-[1,2-b]-1,4-oxazine (its less active enantiomer)], ropinirole, and l-3,4-dihydroxyphenylalanine (l-DOPA). Rotation elicited by S32504 was blocked by the D2/D3receptor antagonists haloperidol and raclopride and by the D2antagonist L741,626 [4-(4-chlorophenyl)-1-(1 H-indol-3-ylmethyl)piperidin-4-ol], but not by the D3antagonist S33084 [(3 aR,9 bS)-N-[4-(8-cyano-1,3 a,4,9 b-tetrahydro-3 H-benzopyrano[3,4-c]pyrrole-2-yl)-butyl]-(4-phenyl)benzamide]. As assessed by dialysis in both lesioned and nonlesioned animals, S32504 (0.04–2.5 mg/kg, s.c.) reduced striatal levels of acetylcholine. This effect was blocked by raclopride, haloperidol, and L741,626 but not S33084. In rats treated with reserpine, hypolocomotion was reversed by S32504 and, less potently, by ropinirole. In “unprimed” marmosets treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, both s.c. (0.01–0.04 mg/kg) and p.o. (0.04–1.25 mg/kg) administration of S32504 dose-dependently and rapidly (within 10 min) increased locomotor activity and reduced disability. Furthermore, S32504 dose-dependently reversed bradykinesia and improved posture in “l-DOPA-primed” animals, whereas eliciting less pronounced dyskinesia than l-DOPA. Finally, in terminally differentiated SH-SY5Y cells presenting a dopaminergic phenotype, S32504, but not S32601, abrogated the neurotoxic effects of 1-methyl-4-phenylpyridinium, an action inhibited by raclopride and S33084 but not L741,626. Ropinirole was weakly neuroprotective in this model. In conclusion, S32504 displays potent and stereospecific activity in rodent, primate, and cellular models of antiparkinsonian properties. Although activation of D2receptors is crucial to the motor actions of S32504, engagement of D3receptors contributes to its neuroprotective properties.

These studies evaluated the potential antiparkinsonian properties of the novel dopamine D(3)/D(2) receptor agonist S32504 [(+)-trans-3,4,4a,5,6, 10b-hexahydro-9-carbamoyl-4-propyl-2H-naphth[1,2-b]-1,4-oxazine] in comparison with those of the clinically employed agonist ropinirole. In rats with a unilateral, 6-hydroxydopamine lesion of the substantia nigra, S32504 (0.0025-0.04 mg/kg, s.c.) more potently elicited contralateral rotation than S32601 [(-)-trans-3,4,4a,5,6, 10b-hexahydro-9-carbamoyl-4-propyl-2H-naphth-[1,2-b]-1,4-oxazine (its less active enantiomer)], ropinirole, and l-3,4-dihydroxyphenylalanine (l-DOPA). Rotation elicited by S32504 was blocked by the D(2)/D(3) receptor antagonists haloperidol and raclopride and by the D(2) antagonist L741,626 [4-(4-chlorophenyl)-1-(1H-indol-3-ylmethyl)piperidin-4-ol], but not by the D(3) antagonist S33084 [(3aR,9bS)-N-[4-(8-cyano-1,3a,4,9b-tetrahydro-3H-benzopyrano[3,4-c]pyrrole-2-yl)-butyl]-(4-phenyl)benzamide]. As assessed by dialysis in both lesioned and nonlesioned animals, S32504 (0.04-2.5 mg/kg, s.c.) reduced striatal levels of acetylcholine. This effect was blocked by raclopride, haloperidol, and L741,626 but not S33084. In rats treated with reserpine, hypolocomotion was reversed by S32504 and, less potently, by ropinirole. In "unprimed" marmosets treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, both s.c. (0.01-0.04 mg/kg) and p.o. (0.04-1.25 mg/kg) administration of S32504 dose-dependently and rapidly (within 10 min) increased locomotor activity and reduced disability. Furthermore, S32504 dose-dependently reversed bradykinesia and improved posture in "L-DOPA-primed" animals, whereas eliciting less pronounced dyskinesia than l-DOPA. Finally, in terminally differentiated SH-SY5Y cells presenting a dopaminergic phenotype, S32504, but not S32601, abrogated the neurotoxic effects of 1-methyl-4-phenylpyridinium, an action inhibited by raclopride and S33084 but not L741,626. Ropinirole was weakly neuroprotective in this model. In conclusion, S32504 displays potent and stereospecific activity in rodent, primate, and cellular models of antiparkinsonian properties. Although activation of D(2) receptors is crucial to the motor actions of S32504, engagement of D(3) receptors contributes to its neuroprotective properties.

Unipolar depression is more common in women than men. We pursue a unifying explanation for the sex difference in the incidence of depression that emerges at puberty and is unlikely to be fully explained as an artifact or as a result of socialization or contemporary sex roles. Because symptomatic anxiety disorders show a similar female preponderance in women, we consider the biology of anxiety disorders and their links to depression. Rather than viewing gender as directly determining differential unipolar depression rates, we hypothesize a primary postpubertal effect of gonadal hormones on limbic system hyperactivity, which predisposes women to potentially higher rates of certain anxiety and depressive disorders.

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. © 2002 Movement Disorder Society

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 γ‐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. © 2002 Movement Disorder Society

Treatments for Parkinson's disease based on replacement of lost dopamine have several problems. Following loss of dopamine, enhanced N‐methyl‐D‐aspartate (NMDA) receptor‐mediated transmission in the striatum is thought to be part of the cascade of events leading to the generation of parkinsonian symptoms. We determined the localisation and pharmacological characteristics of NMDA receptors that play a role in generating parkinsonian symptoms within the striatum. Rats were lesioned unilaterally with 6‐hydroxydopamine (6‐OHDA), and cannulae implanted bilaterally to allow injection of a range of NMDA receptor antagonists at different striatal sites. When injected rostrally into the dopamine‐depleted striatum, the glycine site partial agonist, (+)‐HA‐966 (44–400 nmol) caused a dose‐dependent contraversive rotational response consistent with an antiparkinsonian action. (+)‐HA‐966 (400 nmol) had no effect when infused into more caudal regions of the dopamine‐depleted striatum, or following injection into any striatal region on the dopamine‐intact side. To determine the pharmacological profile of NMDA receptors involved in inducing parkinsonism in 6‐OHDA‐lesioned rats, a range of NMDA receptor antagonists was infused directly into the rostral striatum. Ifenprodil (100 nmol) and 7‐chlorokynurenate (37 nmol), but not MK‐801 (15 nmol) or D‐APV (25 nmol) elicited a dramatic rotational response when injected into the dopamine‐depleted striatum. This pharmacological profile is not consistent with an effect mediated via blocking NR2B‐containing NMDA receptors. The effect of intrastriatal injection of ifenprodil was increased in animals previously treated with levodopa (L‐dopa) methyl ester. This was seen as an increase in on‐time and in peak rotational response. We propose that stimulation of NR2B‐containing NMDA receptors in the rostral striatum underlies the generation of parkinsonian symptoms. These studies are in line with previous findings suggesting that administration of NR2B‐selective NMDA receptor antagonists may be therapeutically beneficial for parkinsonian patients, when given de novo and following L‐dopa treatment. © 2002 Movement Disorder Society.

Cannabis may have medicinal uses in a variety of diseases. The neural mechanisms underlying dystonia involve abnormalities within the basal ganglia—in particular, overactivity of the lateral globus pallidus (GPl). Cannabinoid receptors are located presynaptically on GABA terminals within the GPi, where their activation reduces GABA reuptake. Cannabinoid receptor stimulation may thus reduce overactivity of the GPl and thereby reduce dystonia. A double‐blind, randomised, placebo‐controlled, crossover study using the synthetic cannabinoid receptor agonist nabilone in patients with generalised and segmental primary dystonia showed no significant reduction in dystonia following treatment with nabilone. © 2001 Movement Disorder Society.

The lateral segment of the globus pallidus (GPl) is thought to be overactive in levodopa-induced dyskinesia in PD. Stimulation of cannabinoid receptors in the GPl reduces -aminobutyric acid (GABA) reuptake and enhances GABA transmission and may thus alleviate dyskinesia. In a randomized, double-blind, placebo-controlled, crossover trial (n 7), the authors demonstrate that the cannabinoid receptor agonist nabilone significantly reduces levodopa-induced dyskinesia in PD.

The opioid peptides localized in striatal projection neurons are of great relevance to Parkinson's disease, not only as a consequence of their distribution, but also due to the pronounced changes in expression seen in Parkinson's disease. It has long been suspected that increased expression of enkephalin may represent one of the many mechanisms that compensate for dopamine (DA) depletion in Parkinson's disease. Here we demonstrate that a systemically delivered, selective δ opioid agonist (SNC80) has potent antiparkinsonian actions in both rat and primate models of Parkinson's disease. In rats treated with either the D2-preferring DA antagonist haloperidol (1 mg/kg) or the selective D1 antagonist SCH23390 (1 mg/kg), but not a combination of D1 and D2 antagonists, SNC80 (10 mg/kg) completely reversed the catalepsy induced by DA antagonists. In rats rendered immobile by treatment with reserpine, SNC80 dose-dependently reversed akinesia (EC50 7.49 mg/kg). These effects were dose-dependently inhibited (IC50 1.05 mg/kg) by a selective δ opioid antagonist (naltrindole) and by SCH23390 (1 mg/kg), but not by haloperidol (1 mg/kg). SNC80 also reversed parkinsonian symptoms in the MPTP-treated marmoset. At 10 mg/kg (ip), scores measuring bradykinesia and posture were significantly reduced and motor activity increased to levels comparable with pre-MPTP-treatment scores. Any treatment that serves to increase δ opioid receptor activation may be a useful therapeutic strategy for the treatment of Parkinson's disease, either in the early stages or as an adjunct to dopamine replacement therapy. Furthermore, enhanced enkephalin expression observed in Parkinson's disease may serve to potentiate dopamine acting preferentially at D1 receptors.

Long-term treatment of Parkinson's disease with levodopa is complicated by the emergence of involuntary movements, known as levodopa-induced dyskinesia. It has been hypothesized that increased opioid transmission in striatal output pathways may be responsible for the generation of dyskinesia. In this study, we have investigated the effect of blockade of opioid peptide transmission on levodopa-induced dyskinesia in a primate model of Parkinson's disease—the MPTP-lesioned marmoset. Coadministration of nonselective and μ- or δ-subtype-selective opioid receptor antagonists with levodopa resulted in a significant decrease in dyskinesia. There was no attenuation of the anti-parkinsonian actions of levodopa. These data suggest that specific μ- or δ-opioid receptor antagonists might be applicable clinically in the treatment of levodopa-induced dyskinesia in Parkinson's disease.