Deficits in basal and evoked striatal dopamine release following alpha-synuclein preformed fibril injection: An in vivo microdialysis study

Parkinson's disease (PD) is characterized by the accumulation of misfolded alpha-synuclein (α-syn) protein, forming intraneuronal Lewy body (LB) inclusions. The α-syn preformed fibril (PFF) model of PD recapitulates α-syn aggregation, progressive nigrostriatal degeneration and motor dysfunction; however, little is known about the time course of PFF-induced alterations in basal and evoked dopamine (DA). In vivo microdialysis is well suited for identifying small changes in neurotransmitter levels over extended periods. In the present study, adult male Fischer 344 rats received unilateral, intrastriatal injections of either α-syn PFFs or phosphate-buffered saline (PBS). At 4 or 8 months post-injection (p.i.), animals underwent in vivo microdialysis to evaluate basal extracellular striatal DA and metabolite levels, local KCl-evoked striatal DA release and the effects of systemic levodopa (l-DOPA). Post-mortem analysis demonstrated equivalent PFF-induced reductions in tyrosine hydroxylase (TH) immunoreactive nigral neurons (~50%) and striatal TH (~20%) at both time points. Compared with reduction in striatal TH, reduction in striatal dopamine transporter (DAT) was more pronounced and progressed between the 4- and 8-month p.i. intervals (36% ➔ 46%). Significant PFF-induced deficits in basal and evoked striatal DA, as well as deficits in motor performance, were not observed until 8 months p.i. Responses to l-DOPA did not differ regardless of PBS or PFF treatment. These results suggest that basal and evoked striatal DA are maintained for several months following PFF injection, with loss of both associated with motor dysfunction. Our studies provide insight into the time course and magnitude of PFF-induced extracellular dopaminergic deficits in the striatum.

Striatal serotonin transporter gain-of-function in L-DOPA-treated, hemi-parkinsonian rats

L-DOPA is the standard treatment for Parkinson's disease (PD), but chronic treatment typically leads to L-DOPA-induced dyskinesia (LID). LID involves a complex interaction between the remaining dopamine (DA) system and the semi-homologous serotonin (5-HT) system. Since serotonin transporters (SERT) have some affinity for DA uptake, they may serve as a functional compensatory mechanism when DA transporters (DAT) are scant. DAT and SERT's functional contributions in the dyskinetic brain have not been well delineated. The current investigation sought to determine how DA depletion and L-DOPA treatment affect DAT and SERT transcriptional processes, translational processes, and functional DA uptake in the 6-hydroxydopamine-lesioned hemi-parkinsonian rat. Rats were counterbalanced for motor impairment into equally lesioned treatment groups then given daily L-DOPA (0 or 6 mg/kg) for 2 weeks. At the end of treatment, the substantia nigra was processed for tyrosine hydroxylase (TH) and DAT gene expression and dorsal raphe was processed for SERT gene expression. The striatum was processed for synaptosomal DAT and SERT protein expression and ex vivo DA uptake. Nigrostriatal DA loss severely reduced DAT mRNA and protein expression in the striatum with minimal changes in SERT. L-DOPA treatment, while not significantly affecting DAT or SERT alone, did increase striatal SERT:DAT protein ratios. Using ex vivo microdialysis, L-DOPA treatment increased DA uptake via SERT when DAT was depleted. Overall, these results suggest that DA loss and L-DOPA treatment uniquely alter DAT and SERT, revealing implications for monoamine transporters as potential biomarkers and therapeutic targets in the hemi-parkinsonian model and dyskinetic PD patients.

Moderate intensity aerobic exercise in 6-OHDA-lesioned rats alleviates established motor deficits and reduces neurofilament light and glial fibrillary acidic protein serum levels without increased striatal dopamine or tyrosine hydroxylase protein

Background

Alleviation of motor impairment by aerobic exercise (AE) in Parkinson's disease (PD) points to a CNS response that could be targeted by therapeutic approaches, but recovery of striatal dopamine (DA) or tyrosine hydroxylase (TH) has been inconsistent in rodent studies.

Objective

To increase translation of AE, 3 components were implemented into AE design to determine if recovery of established motor impairment, concomitant with >80% striatal DA and TH loss, was possible. We also evaluated if serum levels of neurofilament light (NfL) and glial fibrillary acidic protein (GFAP), blood-based biomarkers of disease severity in human PD, were affected.

Methods

We used a 6-OHDA hemiparkinson rat model featuring progressive nigrostriatal neuron loss over 28 days, with impaired forelimb use 7 days post-lesion, and hypokinesia onset 21 days post-lesion. After establishing forelimb use deficits, moderate intensity AE began 1-3 days later, 3x per week, for 40 min/session. Motor assessments were conducted weekly for 3 wks, followed by determination of striatal DA, TH protein and mRNA, and NfL and GFAP serum levels.

Results

Seven days after 6-OHDA lesion, recovery of depolarization-stimulated extracellular DA and DA tissue content was <10%, representing severity of DA loss in human PD, concomitant with 50% reduction in forelimb use. Despite severe DA loss, recovery of forelimb use deficits and alleviation of hypokinesia progression began after 2 weeks of AE and was maintained. Increased NfLand GFAP levels from lesion were reduced by AE. Despite these AE-driven changes, striatal DA tissue and TH protein levels were unaffected.

Conclusions

This proof-of-concept study shows AE, using exercise parameters within the capabilities most PD patients, promotes recovery of established motor deficits in a rodent PD model, concomitant with reduced levels of blood-based biomarkers associated with PD severity, without commensurate increase in striatal DA or TH protein.

Broad Serotonergic Actions of Vortioxetine as a Promising Avenue for the Treatment of L-DOPA-Induced Dyskinesia

Parkinson's Disease (PD) is a neurodegenerative disorder characterized by motor symptoms that result from loss of nigrostriatal dopamine (DA) cells. While L-DOPA provides symptom alleviation, its chronic use often results in the development of L-DOPA-induced dyskinesia (LID). Evidence suggests that neuroplasticity within the serotonin (5-HT) system contributes to LID onset, persistence, and severity. This has been supported by research showing 5-HT compounds targeting 5-HT1A/1B receptors and/or the 5-HT transporter (SERT) can reduce LID. Recently, vortioxetine, a multimodal 5-HT compound developed for depression, demonstrated acute anti-dyskinetic effects. However, the durability and underlying pharmacology of vortioxetine's anti-dyskinetic actions have yet to be delineated. To address these gaps, we used hemiparkinsonian rats in Experiment 1, examining the effects of sub-chronic vortioxetine on established LID and motor performance. In Experiment 2, we applied the 5-HT1A antagonist WAY-100635 or 5-HT1B antagonist SB-224289 in conjunction with L-DOPA and vortioxetine to determine the contributions of each receptor to vortioxetine's effects. The results revealed that vortioxetine consistently and dose-dependently attenuated LID while independently, 5-HT1A and 5-HT1B receptors each partially reversed vortioxetine's effects. Such findings further support the promise of pharmacological strategies, such as vortioxetine, and indicate that broad 5-HT actions may provide durable responses without significant side effects.

Characterizing the relationship between L-DOPA-induced-dyskinesia and psychosis-like behaviors in a bilateral rat model of Parkinson's disease

Parkinson's disease associated psychosis (PDAP) is a prevalent non-motor symptom (NMS) that significantly erodes patients' and caregivers' quality of life yet remains vastly understudied. One potential source of PDAP in late-stage Parkinson's disease (PD) is the common dopamine (DA) replacement therapy for motor symptoms, Levodopa (L-DOPA). Given the high incidence of L-DOPA-induced dyskinesia (LID) in later phases of PD, this study sought to characterize the relationship between PDAP and LID in a bilateral medial forebrain bundle 6-hydroxydopamine hydrobromide (6-OHDA) lesion rat model. To assess PDAP in this model, prepulse inhibition (PPI), a well-validated assay of sensorimotor gating, was employed. First, we tested whether a bilateral lesion alone or after chronic L-DOPA treatment was sufficient to induce PPI dysfunction. Rats were also monitored for LID development, using the abnormal involuntary movements (AIMs) test, to examine PPI and LID associations. In experiment 2, Vilazodone (VZD), a serotonin transporter (SERT) blocker and 1A receptor (5-HT_1A) partial agonist was administered to test its potential efficacy in reducing LID and PPI dysfunction. Once testing was complete, tissue was collected for high performance liquid chromatography (HPLC) to examine the monoamine levels in motor and non-motor circuits. Results indicate that bilateral DA lesions produced motor deficits and that chronic L-DOPA induced moderate AIMs; importantly, rats that developed more severe AIMs were more likely to display sensorimotor gating dysfunction. In addition, VZD treatment dose-dependently reduced L-DOPA-induced AIMs without impairing L-DOPA efficacy, although VZD's effects on PPI were limited. Altogether, this project established the bilateral 6-OHDA lesion model accurately portrayed LID and PDAP-like behaviors, uncovered their potential relationship, and finally, demonstrated the utility of VZD for reducing LID.

Pharmacological targeting of G protein-coupled receptor heteromers

A main rationale for the role of G protein-coupled receptor (GPCR) heteromers as targets for drug development is the putative ability of selective ligands for specific GPCRs to change their pharmacological properties upon GPCR heteromerization. The present study provides a proof of concept for this rationale by demonstrating that heteromerization of dopamine D1 and D3 receptors (D1R and D3R) influences the pharmacological properties of three structurally similar selective dopamine D3R ligands, the phenylpiperazine derivatives PG01042, PG01037 and VK4-116. By using D1R-D3R heteromer-disrupting peptides, it could be demonstrated that the three D3R ligands display different D1R-D3R heteromer-dependent pharmacological properties: PG01042, acting as G protein-biased agonist, counteracted D1R-mediated signaling in the D1R-D3R heteromer; PG01037, acting as a D3R antagonist cross-antagonized D1R-mediated signaling in the D1R-D3R heteromer; and VK4-116 specifically acted as a ß-arrestin-biased agonist in the D1R-D3R heteromer. Molecular dynamics simulations predicted potential molecular mechanisms mediating these qualitatively different pharmacological properties of the selective D3R ligands that are dependent on D1R-D3R heteromerization. The results of in vitro experiments were paralleled by qualitatively different pharmacological properties of the D3R ligands in vivo. The results supported the involvement of D1R-D3R heteromers in the locomotor activation by D1R agonists in reserpinized mice and L-DOPA-induced dyskinesia in rats, highlighting the D1R-D3R heteromer as a main pharmacological target for L-DOPA-induced dyskinesia in Parkinson's disease. More generally, the present study implies that when suspecting its pathogenetic role, a GPCR heteromer, and not its individual GPCR units, should be considered as main target for drug development.

P12.08.A Uncovering the glioblastoma tumor-microenvironment by high-end multiplexing with imaging mass cytometry

Background

Glioblastoma is one of the most aggressive cancers, and hypoxia plays an essential role in its tumor- microenvironment. Tumor-associated microglia and macrophages (TAMs) have been reported to constitute up to 30 % of the cells, a fraction that is even higher in hypoxic areas. Single-cell mRNA sequencing of glioblastoma tumors has revealed vast heterogeneity, but the spatial aspects are not entirely defined yet. The aim of this study was to uncover differences between the hypoxic and normoxic tumor-microenvironment of human glioblastoma by high-end multiplexing with imaging mass cytometry.

Material and Methods

A tissue microarray (TMA) with normoxic and hypoxic areas from 4 IDH-wildtype glioblastomas was prepared based on the hypoxia marker hypoxia-inducing factor 1 alpha (HIF1 alpha). The TMA was stained with 18 metal-tagged antibodies covering TAMs, lymphocytes, immune checkpoints, vessels, tumor cells and proliferation. The Hyperion-CYTOF technology was used to ablate the samples and the images were analyzed by MCD viewer, Visiopharm software, and customized R scripts.

Results

Single-cell analysis of 160 fields covering around 45,000 cells in the glioblastoma microenvironment revealed multiple cellular phenotypes. It was revealed that proliferating TAMs (IBA1+, Ki67+) were more frequent in hypoxia, whereas proliferating vessels (CD34+, Ki67+) were more frequent in normoxia. Additionally, proliferating stem-like tumor cells (OLIG-2+, Ki67+) were more frequent in normoxia regions.

Conclusion

Our study revealed multiple cellular phenotypes in the glioblastoma microenvironment. The TAMs, endothelial and tumor cell phenotypes revealed may play a critical role in glioblastoma biology however this needs to be elucidated in future studies.

Combined Knockout of Lrrk2 and Rab29 Does Not Result in Behavioral Abnormalities in vivo

BACKGROUND

Coding mutations in the LRRK2 gene, encoding for a large protein kinase, have been shown to cause familial Parkinson's disease (PD). The immediate biological consequence of LRRK2 mutations is to increase kinase activity, suggesting that inhibition of this enzyme might be useful therapeutically to slow disease progression. Genome-wide association studies have identified the chromosomal loci around LRRK2 and one of its proposed substrates, RAB29, as contributors towards the lifetime risk of sporadic PD.

OBJECTIVE

Considering the evidence for interactions between LRRK2 and RAB29 on the genetic and protein levels, we set out to determine whether there are any consequences on brain function with aging after deletion of both genes.

METHODS

We generated a double knockout mouse model and performed a battery of motor and non-motor behavioral tests. We then investigated postmortem assays to determine the presence of PD-like pathology, including nigral dopamine cell count, astrogliosis, microgliosis, and striatal monoamine content.

RESULTS

Behaviorally, we noted only that 18-24-month Rab29-/- and double (Lrrk2-/-/Rab29-/-) knockout mice had diminished locomotor behavior in open field compared to wildtype mice. However, no genotype differences were seen in the outcomes that represented PD-like pathology.

CONCLUSION

These results suggest that depletion of both LRRK2 and RAB29 is tolerated, at least in mice, and support that this pathway might be able to be safely targeted for therapeutics in humans.

Genetic basis of susceptibility to low-dose paraquat and variation between the sexes in Drosophila melanogaster

Toxicant resistance is a complex trait, affected both by genetics and the environment. Like most complex traits, it can exhibit sexual dimorphism, yet sex is often overlooked as a factor in studies of toxicant resistance. Paraquat, one such toxicant, is a commonly used herbicide and is known to produce mitochondrial oxidative stress, decrease dopaminergic neurons and dopamine (DA) levels, and decrease motor ability. While the main effects of paraquat are well-characterized, less is known about the naturally occurring variation in paraquat susceptibility. The purpose of this study was to map the genes contributing to low-dose paraquat susceptibility in Drosophila melanogaster, and to determine if susceptibility differs between the sexes. One hundred of the Drosophila Genetic Reference Panel (DGRP) lines were scored for susceptibility via climbing ability and used in a genome-wide association study (GWAS). Variation in seventeen genes in females and thirty-five genes in males associated with paraquat susceptibility. Only two candidate genes overlapped between the sexes despite a significant positive correlation between male and female susceptibilities. Many associated polymorphisms had significant interactions with sex, with most having conditionally neutral effects. Conditional neutrality between the sexes probably stems from sex-biased expression which may result from partial resolution of sexual conflict. Candidate genes were verified with RNAi knockdowns, gene expression analyses, and DA quantification. Several of these genes are novel associations with paraquat susceptibility. This research highlights the importance of assessing both sexes when studying toxicant susceptibility.

Dopamine D3 Receptor Plasticity in Parkinson's Disease and L-DOPA-Induced Dyskinesia

Parkinson’s Disease (PD) is characterized by primary and secondary plasticity that occurs in response to progressive degeneration and long-term L-DOPA treatment. Some of this plasticity contributes to the detrimental side effects associated with chronic L-DOPA treatment, namely L-DOPA-induced dyskinesia (LID). The dopamine D3 receptor (D3R) has emerged as a promising target in LID management as it is upregulated in LID. This upregulation occurs primarily in the D1-receptor-bearing (D1R) cells of the striatum, which have been repeatedly implicated in LID manifestation. D3R undergoes dynamic changes both in PD and in LID, making it difficult to delineate D3R’s specific contributions, but recent genetic and pharmacologic tools have helped to clarify its role in LID. The following review will discuss these changes, recent advances to better clarify D3R in both PD and LID and potential steps for translating these findings.

Stereotaxic Intracranial Delivery of Chemicals, Proteins or Viral Vectors to Study Parkinson's Disease

Parkinson's disease (PD) is a progressive disorder traditionally defined by resting tremor and akinesia, primarily due to loss of dopaminergic neurons in the substantia nigra. Affected brain areas display intraneuronal fibrillar inclusions consisting mainly of alpha-synuclein (asyn) proteins. No animal model thus far has recapitulated all characteristics of this disease. Here, we describe the use of stereotaxic injection to deliver chemicals, proteins, or viral vectors intracranially in order to mimic various aspects of PD. These methods are well-established and widely used throughout the PD field. Stereotaxic injections are incredibly flexible; they can be adjusted in concentration, age of animal used for injection, brain area targeted and in animal species used. Combinations of substances allow for rapid variations to assess treatments or alter severity of the pathology or behavioral deficits. By injecting toxins into the brain, we can mimic inflammation and/or a severe loss of dopaminergic neurons resulting in substantial motor phenotypes. Viral vectors can be used to transduce cells to mimic genetic or mechanistic aspects. Preformed fibrillar asyn injections best recapitulate the progressive phenotype over an extended period of time. Once these methods are established, it can be economical to generate a new model compared to creating a new transgenic line. However, this method is labor intensive as it requires 30 minutes to four hours per animal depending on the model used. Each animal will have a slightly different targeting and therefore create a diverse cohort which on one hand can be challenging to interpret results from; on the other hand, help mimic a more realistic diversity found in patients. Mistargeted animals can be identified using behavioral or imaging readouts, or only after being sacrificed leading to smallercohort size after the study has already been concluded. Overall, this method is a rudimentary but effective way to assess a diverse set of PD aspects.

Effects of pedunculopontine nucleus cholinergic lesion on gait and dyskinesia in hemiparkinsonian rats

Pedunculopontine nucleus (PPN) cholinergic neurons are implicated in freezing of gait in Parkinson's disease (PD) and motor stereotypy in normal animals, but the causal role of these neurons on specific gait parameters and treatment-induced dyskinesia remains speculative. Therefore, we examined whether selective cholinergic lesion of the rostral PPN affects PD motor and gait deficits, L-DOPA-induced dyskinesia and motor improvement, and DA-agonist-induced dyskinesia. Sprague-Dawley rats were assigned to one unilaterally lesioned group: Sham lesion, PPN cholinergic lesion with diphtheria urotensin II fusion toxin, medial forebrain bundle dopamine lesion with 6-hydroxydopamine, or dual acetylcholine and dopamine lesion. We used gait analysis and forepaw adjusting steps to examine PD gait and motor deficits. Forepaw adjusting steps were also used to assess motor improvement with L-DOPA treatment. The abnormal involuntary movements scale measured L-DOPA and dopamine D1- and D2-receptor agonist-induced dyskinesia. Lesions, verified via tyrosine hydroxylase and choline acetyltransferase immunohistochemistry reduced an average of 95% of nigral dopamine neurons and 80% of PPN cholinergic neurons, respectively. Rats receiving acetylcholine and dual lesion demonstrated enhanced freezing, and acetylcholine lesioned rats exhibited increased print area and stand index. Dopamine and dual lesion produced similar forepaw adjusting steps task on and off L-DOPA. Relative to DA lesioned rats, dual lesioned rats displayed reduced L-DOPA and DA agonist-induced dyskinesia at specific time points. Our results indicate that PPN cholinergic neurons affect gait parameters related to postural stability. Therefore, therapeutically targeting PPN cholinergic neurons could reduce intractable postural instability in PD without affecting motor benefits or side effects of L-DOPA treatment.

Genetic suppression of the dopamine D3 receptor in striatal D1 cells reduces the development of L-DOPA-induced dyskinesia

Parkinson's Disease (PD) is symptomatically managed with L-DOPA but chronic use results in L-DOPA-induced dyskinesia (LID) characterized by abnormal involuntary movements (AIMs). In LID, dopamine D3 receptors (D3R) are upregulated on D1 receptor (D1R)-bearing medium spiny neurons where the can synergistically drive downstream signaling and motor behaviors. Despite evidence implying D1R-D3R cooperativity in LID, the dyskinesiogenic role of D3R has never been directly tested. To this end, we developed a specific cre-dependent microRNA (miRNA) to irreversibly prevent D3R upregulation in D1R striatal cells. D1-Cre rats received unilateral 6-hydroxydopamine lesions. Three weeks later, rats received an adeno-associated virus expressing either D3R miRNA or a scrambled (SCR) miRNA delivered into the striatum. After 4 weeks, rats received chronic L-DOPA (6 mg/kg) or vehicle. AIMs development and motor behaviors were assayed throughout treatment. At the conclusion of the experiment, efficacy and fidelity of the miRNA strategy was analyzed using in situ hybridization (ISH). ISH analyses demonstrated that D1R+/D3R+ cells were upregulated in LID and that the selective D3R miRNA reduced D1R+/D3R+ co-expression. Importantly, silencing of D3R also significantly attenuated LID development without impacting L-DOPA efficacy or other locomotion. These data highlight a dyskinesiogenic role of D3R within D1R cells in LID and highlight aberrant D1R-D3R interactions as targets of LID management.

Evaluation of Deep Learning to Augment Image-Guided Radiotherapy for Head and Neck and Prostate Cancers

IMPORTANCE

Personalized radiotherapy planning depends on high-quality delineation of target tumors and surrounding organs at risk (OARs). This process puts additional time burdens on oncologists and introduces variability among both experts and institutions.

OBJECTIVE

To explore clinically acceptable autocontouring solutions that can be integrated into existing workflows and used in different domains of radiotherapy.

DESIGN, SETTING, AND PARTICIPANTS

This quality improvement study used a multicenter imaging data set comprising 519 pelvic and 242 head and neck computed tomography (CT) scans from 8 distinct clinical sites and patients diagnosed either with prostate or head and neck cancer. The scans were acquired as part of treatment dose planning from patients who received intensity-modulated radiation therapy between October 2013 and February 2020. Fifteen different OARs were manually annotated by expert readers and radiation oncologists. The models were trained on a subset of the data set to automatically delineate OARs and evaluated on both internal and external data sets. Data analysis was conducted October 2019 to September 2020.

MAIN OUTCOMES AND MEASURES

The autocontouring solution was evaluated on external data sets, and its accuracy was quantified with volumetric agreement and surface distance measures. Models were benchmarked against expert annotations in an interobserver variability (IOV) study. Clinical utility was evaluated by measuring time spent on manual corrections and annotations from scratch.

RESULTS

A total of 519 participants' (519 [100%] men; 390 [75%] aged 62-75 years) pelvic CT images and 242 participants' (184 [76%] men; 194 [80%] aged 50-73 years) head and neck CT images were included. The models achieved levels of clinical accuracy within the bounds of expert IOV for 13 of 15 structures (eg, left femur, κ = 0.982; brainstem, κ = 0.806) and performed consistently well across both external and internal data sets (eg, mean [SD] Dice score for left femur, internal vs external data sets: 98.52% [0.50] vs 98.04% [1.02]; P = .04). The correction time of autogenerated contours on 10 head and neck and 10 prostate scans was measured as a mean of 4.98 (95% CI, 4.44-5.52) min/scan and 3.40 (95% CI, 1.60-5.20) min/scan, respectively, to ensure clinically accepted accuracy. Manual segmentation of the head and neck took a mean 86.75 (95% CI, 75.21-92.29) min/scan for an expert reader and 73.25 (95% CI, 68.68-77.82) min/scan for a radiation oncologist. The autogenerated contours represented a 93% reduction in time.

CONCLUSIONS AND RELEVANCE

In this study, the models achieved levels of clinical accuracy within expert IOV while reducing manual contouring time and performing consistently well across previously unseen heterogeneous data sets. With the availability of open-source libraries and reliable performance, this creates significant opportunities for the transformation of radiation treatment planning.

Striatal Nurr1, but not FosB expression links a levodopa-induced dyskinesia phenotype to genotype in Fisher 344 vs. Lewis hemiparkinsonian rats

Numerous genes, and alterations in their expression, have been identified as risk factors for developing levodopa-induced dyskinesia (LID). However, our understanding of the complexities of molecular changes remains insufficient for development of clinical treatment. In the current study we used gene array, in situ hybridization, immunohistochemistry, and microdialysis to provide a unique compare and contrast assessment of the relationship of four candidate genes to LID, employing three genetically distinct rat strains (Sprague-Dawley (SD), Fischer-344 (F344) and Lewis-RT.1) showing differences in dyskinesia susceptibility and 'first-ever LID' versus 'chronic LID' expression in subjects displaying equal dyskinesia severity. In these studies, rat strains were easily distinguishable for their LID propensity with: 1) a majority of SD rats expressing LID (LID+) and a subset being resistant (LID-); 2) all F344 rats readily developing (LID+); and 3) all Lewis rats being LID-resistant (LID-). Following chronic levodopa, LID+ SD rats showed significant increases in candidate gene expression: Nr4a2/(Nurr1) > > Trh > Inhba = Fosb. However, SD rats with long-standing striatal dopamine (DA) depletion treated with first-ever versus chronic high-dose levodopa revealed that despite identical levels of LID severity: 1) Fosb and Nurr1 transcripts but not protein were elevated with acute LID expression; 2) FOSB/ΔFOSB and NURR1 proteins were elevated only with chronic LID; and 3) Trh transcript and protein were elevated only with chronic LID. Strikingly, despite similar levodopa-induced striatal DA release in both LID-expressing F344 and LID-resistant Lewis rats, Fosb, Trh, Inhba transcripts were significantly elevated in both strains; however, Nurr1 mRNA was significantly increased only in LID+ F344 rats. These findings suggest a need to reevaluate currently accepted genotype-to-phenotype relationships in the expression of LID, specifically that of Fosb, a transcription factor generally assumed to play a causal role, and Nurr1, a transcription factor that has received significant attention in PD research linked to its critical role in the survival and function of midbrain DA neurons but who's striatal expression, generally below levels of detection, has remained largely unexplored as a regulator of LID. Finally these studies introduce a novel 'model' (inbred F344 vs inbred Lewis) that may provide a powerful tool for investigating the role for 'dyskinesia-resistance' genes downstream of 'dyskinesia-susceptibility' genes in modulating LID expression, a concept that has received considerably less attention and offers a new ways of thinking about antidyskinetic therapies.

Pedunculopontine Nucleus Degeneration Contributes to Both Motor and Non-Motor Symptoms of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by hypokinetic motor features; however, patients also display non-motor symptoms like sleep disorders. The standard treatment for PD is dopamine replacement with L-DOPA; however, symptoms including gait deficits and sleep disorders are unresponsive to L-DOPA. Notably, these symptoms have been linked to aberrant activity in the pedunculopontine nucleus (PPN). Of late, clinical trials involving PPN deep brain stimulation (DBS) have been employed to alleviate gait deficits. Although preclinical evidence implicating PPN cholinergic neurons in gait dysfunction was initially promising, DBS trials fell short of expected outcomes. One reason for the failure of DBS may be that the PPN is a heterogenous nucleus that consists of GABAergic, cholinergic, and glutamatergic neurons that project to a diverse array of brain structures. Second, DBS trials may have been unsuccessful because PPN neurons are susceptible to mitochondrial dysfunction, Lewy body pathology, and degeneration in PD. Therefore, pharmaceutical or gene-therapy strategies targeting specific PPN neuronal populations or projections could better alleviate intractable PD symptoms. Unfortunately, how PPN neuronal populations and their respective projections influence PD motor and non-motor symptoms remains enigmatic. Herein, we discuss normal cellular and neuroanatomical features of the PPN, the differential susceptibility of PPN neurons to PD-related insults, and we give an overview of literature suggesting a role for PPN neurons in motor and sleep deficits in PD. Finally, we identify future approaches directed towards the PPN for the treatment of PD motor and sleep symptoms.

Reciprocal cross-sensitization of D1 and D3 receptors following pharmacological stimulation in the hemiparkinsonian rat

In the majority of Parkinson's disease (PD) patients, long-term dopamine (DA) replacement therapy leads to dyskinesia characterized by abnormal involuntary movements (AIMs). There are various mechanisms of dyskinesia, such as the sensitization of striatal DA D1 receptors (D₁R) and upregulation of DA D3 receptors (D₃R). These receptors interact physically and functionally in D₁R-bearing medium spiny neurons to synergistically drive dyskinesia. However, the cross-receptor-mediated effects due to D₁R-D₃R cooperativity are still poorly understood. In pursuit of this, we examined whether or not pharmacological D₁R or D₃R stimulation sensitizes the dyskinetic response to the appositional agonist, a process known as cross-sensitization. First, we established D₁R-D₃R behavioral synergy in a cohort of 6-OHDA-lesioned female adult Sprague-Dawley rats. Then, in a new cohort, we tested for cross-sensitization in a between-subject design. Five groups received a sub-chronic regimen of either saline, the D₁R agonist SKF38393 (1.0 mg/kg), or the D₃R agonist PD128907 (0.3 mg/kg). For the final injection, each group received an acute injection of the other agonist. AIMs were monitored following each injection. Sub-chronic administration of both SKF38393 and PD128907 induced the development of dyskinesia. More importantly, cross-agonism tests revealed reciprocal cross-sensitization; chronic treatment with either SKF38393 or PD128907 induced sensitization to a single administration of the other agonist. This reciprocity was not marked by changes to either D₁R or D₃R striatal mRNA expression. The current study provides key behavioral data demonstrating the role of D3R in dyskinesia and provides behavioral evidence of D1R and D3R functional interactions.

Diverse serotonin actions of vilazodone reduce l-3,4-dihidroxyphenylalanine-induced dyskinesia in hemi-parkinsonian rats

BACKGROUND

The serotonergic system is a well-established modulator of l-dopa-induced dyskinesia. To date, targeting serotonin transporters or serotonin receptor subtype 1A (5-HT_1A ) reduces l-dopa-induced dyskinesia in animal models; however, these strategies have failed to translate clinically. Ideally, a compound acting at both known antidyskinetic sites could optimize serotonin-mediated approaches. Vilazodone is a selective serotonin reuptake inhibitor and a partial 5-HT_1A agonist approved by the U.S. Food and Drug Administration, situating Vilazodone in a unique position to reduce l-dopa-induced dyskinesia without compromising l-dopa-mediated motor improvements.

OBJECTIVES

The goal of the present study was to characterize Vilazodone's effects on l-dopa-induced behaviors, neurochemistry and gene expression in unilateral 6-hydroxydopamine-lesioned hemi-parkinsonian rats.

METHODS

In experiments 1 and 2, l-dopa-naïve and l-dopa-primed animals were coadministered Vilazodone and l-dopa daily for 3 weeks to model subchronic use, and behavioral, neurochemical, and messenger RNA (mRNA) expression changes were measured. In experiment 3, dyskinetic behavior was assessed following 5-HT_1A or serotonin receptor subtype 1B blockade prior to Vilazodone-l-dopa coadministration.

RESULTS

Vilazodone significantly suppressed developing and established l-dopa-induced dyskinesia without compromising the promotor effects of l-dopa therapy. In the dopamine-depleted striatum, Vilazodone-l-dopa cotreatment increased dopamine content, suggesting a normalization of dopamine kinetics in dyskinetic brain, and reduced l-dopa-induced c-Fos and preprodynorphin mRNA overexpression, indicative of attenuated dopamine D₁ receptor-mediated direct pathway overactivity. Only 5-HT_1A antagonism partially attenuated Vilazodone's antidyskinetic efficacy, suggesting both serotonin transporter-dependent effects and 5-HT_1A receptors in Vilazodone's actions.

CONCLUSIONS

Our findings show Vilazodone has a serotonin-dependent effect on rodent l-dopa-induced dyskinesia and implicate the potential for repositioning Vilazodone against l-dopa-induced dyskinesia development and expression in Parkinson's disease patients. © 2018 International Parkinson and Movement Disorder Society.

The effect of foot orthoses and insoles on running economy and performance in distance runners: A systematic review and meta-analysis

Foot orthoses and insoles are prescribed to runners, however their impact on running economy and performance is uncertain. The aim of this systematic review and meta-analysis was to determine the effect of foot orthoses and insoles on running economy and performance in distance runners. Seven electronic databases were searched from inception until June 2018. Eligible studies investigated the effect of foot orthoses or insoles on running economy (using indirect calorimetry) or running performance. Standardised mean differences (SMDs) were computed and meta-analyses were conducted using random effects models. Methodological quality was assessed using the Quality Index. Nine studies met the criteria and were included: five studies investigated the effect of foot orthoses on running economy and four investigated insoles. Foot orthoses were associated with small negative effects on running economy compared to no orthoses (SMD 0.42 [95% CI 0.17,0.72] p = 0.007). Shock absorbing insoles were also associated with negative effects on running economy, but an imprecise estimate (SMD 0.26 [95% CI -0.33,0.84] p = 0.83). Quality Index scores ranged from 4 to 15 out of 17. Foot orthoses and shock absorbing insoles may adversely affect running economy in distance runners. Future research should consider their potential effects on running performance.

Vapor-Deposited Ethylbenzene Glasses Approach "Ideal Glass" Density

Spectroscopic ellipsometry was used to characterize vapor-deposited glasses of ethylbenzene (T_g = 115.7 K). For this system, previous calorimetric experiments have established that a transition to the ideal glass state is expected to occur near 101 K (the Kauzmann temperature, T_K) if the low-temperature supercooled liquid has the properties expected based upon extrapolation from above T_g. Ethylbenzene glasses were vapor-deposited at substrate temperatures between 100 (∼0.86 T_g) and 116 K (∼T_g), using deposition rates of 0.02-2.1 nm/s. Down to 103 K, glasses prepared in the limit of low deposition rate have densities consistent with the extrapolated supercooled liquid. The highest density glass is within 0.15% of the density expected for the ideal glass. These results support the hypothesis that the extrapolated properties of supercooled ethylbenzene are correct to within just a few Kelvin of T_K, consistent with the existence of a phase transition to an ideal glass state at T_K.

Late aging-associated increases in L-DOPA-induced dyskinesia are accompanied by heightened neuroinflammation in the hemi-parkinsonian rat

Aging is a primary risk factor for the development of Parkinson's disease (PD), and aging differentially predicts the incidence of L-DOPA-induced dyskinesia (LID). The goal of this work was to establish whether late aging-associated exacerbation of LID would be related to neuroinflammation in the hemi-parkinsonian rat. Two studies were conducted in which adult (3 months) and aged (18 months) male Fischer 344 rats bearing unilateral 6-hydroxydopamine lesions of the medial forebrain bundle were injected acutely with vehicle or L-DOPA (6 mg/kg). LID was quantified, and neuroinflammation was assessed postmortem via gene expression markers in the striatum (experiment 1) or through concurrent large-molecule microdialysis (experiment 2). In addition to exacerbating LID despite similar levels of striatal dopamine loss, late aging was associated with persistently elevated IL-1β gene expression ipsilateral to lesion, as well as a trend toward greater extracellular concentrations of IL-1β in response to acute L-DOPA treatment. In contrast, aged sham-operated rats displayed greater extracellular IL-6. Taken together, these data demonstrate an age-related vulnerability to LID and highlight potential neuroinflammatory mediators associated with these effects.

Effects of Muscarinic Acetylcholine m1 and m4 Receptor Blockade on Dyskinesia in the Hemi-Parkinsonian Rat

Standard treatment for Parkinson's disease (PD) is L-DOPA, but with chronic administration the majority of patients develop L-DOPA-induced dyskinesia (LID). Emerging evidence implicates the cholinergic system in PD and LID. Muscarinic acetylcholine receptors (mAChR) are known to modulate movement and of late have been implicated as possible targets for LID. Therefore the current study investigated the role of M₁ and M₄ mAChRs in LID, on motor performance following L-DOPA treatment, and sought to identify brain sites through which these receptors were acting. We first administered M₁R-preferring antagonist trihexyphenidyl (0, 0.1, and 1.0 mg/kg, i.p.) or the M₄R-preferring antagonist tropicamide (0, 10, and 30 mg/kg, i.p.) before L-DOPA, after which LID and motor performance were evaluated. Both compounds worsened and extended the time course of LID, while M₁R blockade improved motor performance. We then evaluated the effects of tropicamide and trihexyphenidyl on dyskinesia induced by D₁R agonist SKF81297 or D₂R agonist quinpirole. Surprisingly, both M₁R and M₄R antagonists reduced D₁R agonist-induced dyskinesia but not D₂R agonist-induced dyskinesia, suggesting that mAChR blockade differentially affects MSN firing in the absence of postsynaptic DA. Finally, we evaluated effects of striatum- or PPN-targeted tropicamide microinfusion on LID and motor performance. Despite prior evidence, M₄R blockade in either site alone did not affect the severity of LID via local striatal or PPN infusions. Taken together, these data suggest M₄R as a promising therapeutic target for reducing LID using more selective compounds.

Regulation of dopamine neurotransmission from serotonergic neurons by ectopic expression of the dopamine D2 autoreceptor blocks levodopa-induced dyskinesia

Levodopa-induced dyskinesias (LID) are a prevalent side effect of chronic treatment with levodopa (L-DOPA) for the motor symptoms of Parkinson’s disease (PD). It has long been hypothesized that serotonergic neurons of the dorsal raphe nucleus (DRN) are capable of L-DOPA uptake and dysregulated release of dopamine (DA), and that this “false neurotransmission” phenomenon is a main contributor to LID development. Indeed, many preclinical studies have demonstrated LID management with serotonin receptor agonist treatment, but unfortunately, promising preclinical data has not been translated in large-scale clinical trials. Importantly, while there is an abundance of convincing clinical and preclinical evidence supporting a role of maladaptive serotonergic neurotransmission in LID expression, there is no direct evidence that dysregulated DA release from serotonergic neurons impacts LID formation. In this study, we ectopically expressed the DA autoreceptor D2R_s (or GFP) in the DRN of 6-hydroxydopamine (6-OHDA) lesioned rats. No negative impact on the therapeutic efficacy of L-DOPA was seen with rAAV-D2R_s therapy. However, D2R_s treated animals, when subjected to a LID-inducing dose regimen of L-DOPA, remained completely resistant to LID, even at high doses. Moreover, the same subjects remained resistant to LID formation when treated with direct DA receptor agonists, suggesting D2R_s activity in the DRN blocked dyskinesogenic L-DOPA priming of striatal neurons. In vivo microdialysis confirmed that DA efflux in the striatum was reduced with rAAV-D2R_s treatment, providing explicit evidence that abnormal DA release from DRN neurons can affect LID. This is the first direct evidence of dopaminergic neurotransmission in DRN neurons and its modulation with rAAV-D2R_s gene therapy confirms the serotonin hypothesis in LID, demonstrating that regulation of serotonergic neurons achieved with a gene therapy approach offers a novel and potent antidyskinetic therapy.

Behavioral and cellular dopamine D1 and D3 receptor-mediated synergy: Implications for L-DOPA-induced dyskinesia

Individually, D1 and D3 dopamine receptors (D₁R and D₃R, respectively) have been implicated in L-DOPA-induced dyskinesia (LID). Of late, direct D₁R-D₃R interactions have been linked to LID yet remain enigmatic. Therefore, the current research sought to characterize consequences of putative D₁R-D₃R interactions in dyskinesia expression and in LID-associated downstream cellular signaling. To do so, adult male Sprague-Dawley hemi-parkinsonian rats were given daily L-DOPA (6 mg/kg; s.c.) for 2 weeks to establish stable LID, as measured via the abnormal voluntary movements (AIMs) scale. Thereafter, rats underwent dose-response AIMs testing for the D₁R agonist SKF38393 (0, 0.3, 1.0, 3.0 mg/kg) and the D₃R agonist, PD128907 (0, 0.1, 0.3, 1.0 mg/kg). Each agonist dose-dependently induced dyskinesia, implicating individual receptor involvement. More importantly, when threshold doses were co-administered, rats displayed synergistic exacerbation of dyskinesia. Interestingly, this observation was not mirrored in general locomotor behaviors, highlighting a potentially dyskinesia-specific effect. To illuminate the mechanisms by which D₁R-D₃R co-stimulation led to in vivo synergy, levels of striatal phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) were quantified after administration of SKF38393 and/or PD128907. Combined agonist treatment synergistically drove striatal pERK1/2 expression. Together, these results support the presence of a functional, synergistic interaction between D₁R and D₃R that manifests both behaviorally and biochemically to drive dyskinesia in hemi-parkinsonian rats.

A new outlook on cholinergic interneurons in Parkinson's disease and L-DOPA-induced dyskinesia

Traditionally, dopamine (DA) and acetylcholine (ACh) striatal systems were considered antagonistic and imbalances or aberrant signaling between these neurotransmitter systems could be detrimental to basal ganglia activity and pursuant motor function, such as in Parkinson's disease (PD) and L-DOPA-induced dyskinesia (LID). Herein, we discuss the involvement of cholinergic interneurons (ChIs) in striatally-mediated movement in a healthy, parkinsonian, and dyskinetic state. ChIs integrate numerous neurotransmitter signals using intrinsic glutamate, serotonin, and DA receptors and convey the appropriate transmission onto nearby muscarinic and nicotinic ACh receptors to produce movement. In PD, severe DA depletion causes abnormal rises in ChI activity which promote striatal signaling to attenuate normal movement. When treating PD with L-DOPA, hyperkinetic side effects, or LID, develop due to increased striatal DA; however, the role of ChIs and ACh transmission, until recently has been unclear. Fortunately, new technology and pharmacological agents have facilitated understanding of ChI function and ACh signaling in the context of LID, thus offering new opportunities to modify existing and discover future therapeutic strategies in movement disorders.

Ceftriaxone reduces L-dopa-induced dyskinesia severity in 6-hydroxydopamine parkinson's disease model

BACKGROUND

Increased extracellular glutamate may contribute to l-dopa induced dyskinesia, a debilitating side effect faced by Parkinson's disease patients 5 to 10 years after l-dopa treatment. Therapeutic strategies targeting postsynaptic glutamate receptors to mitigate dyskinesia may have limited success because of significant side effects. Increasing glutamate uptake may be another approach to attenuate excess glutamatergic neurotransmission to mitigate dyskinesia severity or prolong the time prior to onset. Initiation of a ceftriaxone regimen at the time of nigrostriatal lesion can attenuate tyrosine hydroxylase loss in conjunction with increased glutamate uptake and glutamate transporter GLT-1 expression in a rat 6-hydroxydopamine model. In this article, we examined if a ceftriaxone regimen initiated 1 week after nigrostriatal lesion, but prior to l-dopa, could reduce l-dopa-induced dyskinesia in an established dyskinesia model.

METHODS

Ceftriaxone (200 mg/kg, intraperitoneal, once daily, 7 consecutive days) was initiated 7 days post-6-hydroxydopamine lesion (days 7-13) and continued every other week (days 21-27, 35-39) until the end of the study (day 39 postlesion, 20 days of l-dopa).

RESULTS

Ceftriaxone significantly reduced abnormal involuntary movements at 5 time points examined during chronic l-dopa treatment. Partial recovery of motor impairment from nigrostriatal lesion by l-dopa was unaffected by ceftriaxone. The ceftriaxone-treated l-dopa group had significantly increased striatal GLT-1 expression and glutamate uptake. Striatal tyrosine hydroxylase loss in this group was not significantly different when compared with the l-dopa alone group.

CONCLUSIONS

Initiation of ceftriaxone after nigrostriatal lesion, but prior to and during l-dopa, may reduce dyskinesia severity without affecting l-dopa efficacy or the reduction of striatal tyrosine hydroxylase loss. © 2017 International Parkinson and Movement Disorder Society.

Working Memory and Speech Recognition in Noise Under Ecologically Relevant Listening Conditions: Effects of Visual Cues and Noise Type Among Adults With Hearing Loss

PURPOSE

This study evaluated the relationship between working memory (WM) and speech recognition in noise with different noise types as well as in the presence of visual cues.

METHOD

Seventy-six adults with bilateral, mild to moderately severe sensorineural hearing loss (mean age: 69 years) participated. Using a cross-sectional design, 2 measures of WM were taken: a reading span measure, and Word Auditory Recognition and Recall Measure (Smith, Pichora-Fuller, & Alexander, 2016). Speech recognition was measured with the Multi-Modal Lexical Sentence Test for Adults (Kirk et al., 2012) in steady-state noise and 4-talker babble, with and without visual cues. Testing was under unaided conditions.

RESULTS

A linear mixed model revealed visual cues and pure-tone average as the only significant predictors of Multi-Modal Lexical Sentence Test outcomes. Neither WM measure nor noise type showed a significant effect.

CONCLUSION

The contribution of WM in explaining unaided speech recognition in noise was negligible and not influenced by noise type or visual cues. We anticipate that with audibility partially restored by hearing aids, the effects of WM will increase. For clinical practice to be affected, more significant effect sizes are needed.

D-512, a novel dopamine D2/3 receptor agonist, demonstrates greater anti-Parkinsonian efficacy than ropinirole in Parkinsonian rats

BACKGROUND AND PURPOSE

Symptoms of Parkinson's disease are commonly managed using selective dopamine D_2/3 receptor agonists, including ropinirole. While D_2/3 agonists are useful in early-stage Parkinson's disease, they tend to lose efficacy in later disease stages and do not appear to modify disease progression. We have recently developed a novel 'multifunctional' compound, D-512: a high-affinity D_2/3 receptor agonist with antioxidant and other neuroprotective properties that may limit Parkinson's disease progression. This study sought to compare the anti-Parkinsonian properties of the clinically used compound, ropinirole, with those of the novel compound, D-512.

EXPERIMENTAL APPROACH

A rat model of Parkinson's disease was created by unilaterally infusing 6-hydroxydopamine, a dopamine neurotoxin, into the medial forebrain bundle. D-512 was compared with ropinirole for ability to stimulate spontaneous motor activity and reverse Parkinsonian akinesia. These beneficial effects were compared against each drug's liability to provoke dyskinesia, a common motor side effect.

KEY RESULTS

Both compounds increased spontaneous movement, but D-512 showed a longer duration of action. Only D-512 was able to significantly reverse forelimb akinesia. Drug-induced dyskinesia was similar for equivalent doses.

CONCLUSIONS AND IMPLICATIONS

Compared with ropinirole, D-512 showed greater peak-dose efficacy and a longer duration of action, despite a similar side-effect profile. Our results add to earlier data showing that D-512 is superior to available D_2/3 agonists and could merit clinical investigation.

Disaggregating asthma: Big investigation versus big data

We are facing a major challenge in bridging the gap between identifying subtypes of asthma to understand causal mechanisms and translating this knowledge into personalized prevention and management strategies. In recent years, “big data” has been sold as a panacea for generating hypotheses and driving new frontiers of health care; the idea that the data must and will speak for themselves is fast becoming a new dogma. One of the dangers of ready accessibility of health care data and computational tools for data analysis is that the process of data mining can become uncoupled from the scientific process of clinical interpretation, understanding the provenance of the data, and external validation. Although advances in computational methods can be valuable for using unexpected structure in data to generate hypotheses, there remains a need for testing hypotheses and interpreting results with scientific rigor. We argue for combining data- and hypothesis-driven methods in a careful synergy, and the importance of carefully characterized birth and patient cohorts with genetic, phenotypic, biological, and molecular data in this process cannot be overemphasized. The main challenge on the road ahead is to harness bigger health care data in ways that produce meaningful clinical interpretation and to translate this into better diagnoses and properly personalized prevention and treatment plans. There is a pressing need for cross-disciplinary research with an integrative approach to data science, whereby basic scientists, clinicians, data analysts, and epidemiologists work together to understand the heterogeneity of asthma.

The Role of Primary Motor Cortex (M1) Glutamate and GABA Signaling in l-DOPA-Induced Dyskinesia in Parkinsonian Rats

Long-term treatment of Parkinson's disease with l-DOPA almost always leads to the development of involuntary movements termed l-DOPA-induced dyskinesia. Whereas hyperdopaminergic signaling in the basal ganglia is thought to cause dyskinesia, alterations in primary motor cortex (M1) activity are also prominent during dyskinesia, suggesting that the cortex may represent a therapeutic target. The present study used the rat unilateral 6-hydroxydopamine lesion model of Parkinson's disease to characterize in vivo changes in GABA and glutamate neurotransmission within M1 and determine their contribution to behavioral output. 6-Hydroxydopamine lesion led to parkinsonian motor impairment that was partially reversed by l-DOPA. Among sham-lesioned rats, l-DOPA did not change glutamate or GABA efflux. Likewise, 6-hydroxydopamine lesion did not impact GABA or glutamate among rats chronically treated with saline. However, we observed an interaction of lesion and treatment whereby, among lesioned rats, l-DOPA given acutely (1 d) or chronically (14-16 d) reduced glutamate efflux and enhanced GABA efflux. Site-specific microinjections into M1 demonstrated that l-DOPA-induced dyskinesia was reduced by M1 infusion of a D1 antagonist, an AMPA antagonist, or a GABAA agonist. Overall, the present study demonstrates that l-DOPA-induced dyskinesia is associated with increased M1 inhibition and that exogenously enhancing M1 inhibition may attenuate dyskinesia, findings that are in agreement with functional imaging and transcranial magnetic stimulation studies in human Parkinson's disease patients. Together, our study suggests that increasing M1 inhibitory tone is an endogenous compensatory response designed to limit dyskinesia severity and that potentiating this response is a viable therapeutic strategy.

SIGNIFICANCE STATEMENT

Most Parkinson's disease patients will receive l-DOPA and eventually develop hyperkinetic involuntary movements termed dyskinesia. Such symptoms can be as debilitating as the disease itself. Although dyskinesia is associated with dynamic changes in primary motor cortex physiology, to date, there are no published studies investigating in vivo neurotransmitter release in M1 during dyskinesia. In parkinsonian rats, l-DOPA administration reduced M1 glutamate efflux and enhanced GABA efflux, coincident with the emergence of dyskinetic behaviors. Dyskinesia could be reduced by local M1 modulation of D1, AMPA, and GABAA receptors, providing preclinical support for the notion that exogenously blunting M1 signaling (pharmacologically or with cortical stimulation) is a therapeutic approach to the treatment of debilitating dyskinesias.

Monoamine transporter contributions to l-DOPA effects in hemi-parkinsonian rats

l-DOPA is the standard treatment for Parkinson's disease (PD), but chronic treatment typically leads to abnormal involuntary movement or dyskinesia (LID) development. Although poorly understood, dyskinetic mechanisms involve a complex interaction between the remaining dopamine system and the semi-homologous serotonin and norepinephrine systems. Serotonin and norepinephrine transporters (SERT and NET, respectively) have affinity for dopamine uptake especially when dopamine transporters (DAT) are scant. Monoamine reuptake inhibitors have been reported to modulate l-DOPA's anti-parkinsonian effects, but DAT, SERT, and NET's contribution to dyskinesia has not been well delineated. The current investigation sought to uncover the differential expression and function of DAT, SERT, and NET in the l-DOPA-treated hemi-parkinsonian rat. Protein analysis of striatal monoamine transporters in unilateral sham or 6-hydroxydopamine-lesioned rats treated with l-DOPA (0 or 6 mg/kg) showed lesion-induced DAT loss and l-DOPA-induced gain in SERT:DAT and NET:DAT ratios in lesioned rats which positively correlated with dyskinesia expression, suggesting functional shifts among monoamine transporters in the dyskinetic state. SERT blockade with citalopram (3, 5 mg/kg) reduced LID while DAT and NET blockade with GBR-12909 (5, 10 mg/kg) and nisoxetine (5, 10 mg/kg), respectively, mildly exacerbated dyskinesia expression. Transporter inhibition did not significantly alter l-DOPA's ability to reverse motor deficit. Overall, DA and DAT loss with l-DOPA treatment appear to precipitate gain in SERT and NET function. Strong correlations with LID and direct behavioral comparisons of selective transporter blockade reveal novel implications for SERT, DAT, and NET as potential biomarkers and therapeutic targets in the hemi-parkinsonian model and dyskinetic PD patients.

Effect of Paroven on Skin Oxygenation in Patients with Varicose Veins

A double blind placebo-controlled clinical trial was undertaken to investigate the effect of 500 mg bd of Paroven taken for four weeks on the tissue oxygenation, ankle oedema and calf pump function of 48 patients with chronic venous disease.

There was no evidence that Paroven reduced ankle swelling or improved calf pump function, but it did cause a significant improvement in transcutaneous oxygen levels measured in the calf skin of the ulcer hearing area ( p = 0.026) which was confirmed when the oxygen levels of the active and placebo treated groups were compared at the end of four weeks treatment ( p = 0.02). This improvement in tissue oxygenation may be the result of alterations in the capillary exchange produced by the drug and may account for the symptomatic benefit associated with its use.

A working model for the assessment of disruptions in social behavior among aged rats: The role of sex differences, social recognition, and sensorimotor processes

Aging results in a natural decline in social behavior, yet little is known about the processes underlying these changes. Engaging in positive social interaction is associated with many health benefits, including reduced stress reactivity, and may serve as a potential buffer against adverse consequences of aging. The goal of these studies was to establish a tractable model for the assessment of social behavior deficits associated with late aging. Thus, in Exp. 1, 1.5-, 3-, and 18-month-old male Fischer 344 (F344) rats were assessed for object investigation, and social interaction with a same-aged partner (novel/familiar), or a different-aged partner, thereby establishing working parameters for studies that followed. Results revealed that 18-month-old males exhibited reductions in social investigation and social contact behavior, with this age-related decline not influenced by familiarity or age of the social partner. Subsequently, Exp. 2 extended assessment of social behavior to both male and female F344 rats at multiple ages (3, 9, 18, and 24 months), after which a series of sensorimotor performance tests were conducted. In this study, both males and females exhibited late aging-related reductions in social interactions, but these changes were more pronounced in females. Additionally, sensorimotor performance was shown to be impaired in 24-month-olds, but not 18-month-olds, with this deficit more evident in males. Finally, Exp. 3 examined whether aging-related inflammation could account for declines in social behavior during late aging by administering naproxen (0, 7, 14, and 28 mg/kg; s.c.)-a non-steroidal anti-inflammatory drug-to 18-month-old females. Results from this study revealed that social behavior was unaffected by acute or repeated (6 days) naproxen, suggesting that aging-related social deficits in females may not be a consequence of a general aging-related inflammation and/or malaise. Together, these findings demonstrate that aging-related declines in social behavior are (i) specific to social stimuli and (ii) not indicative of a general state of aging-related debilitation. Thus, these findings establish working parameters for a highly tractable model in which the neural and hormonal mechanisms underlying aging-related declines in social behavior can be examined.

Alterations in primary motor cortex neurotransmission and gene expression in hemi-parkinsonian rats with drug-induced dyskinesia

Treatment of Parkinson's disease (PD) with dopamine replacement relieves symptoms of poverty of movement, but often causes drug-induced dyskinesias. Accumulating clinical and pre-clinical evidence suggests that the primary motor cortex (M1) is involved in the pathophysiology of PD and that modulating cortical activity may be a therapeutic target in PD and dyskinesia. However, surprisingly little is known about how M1 neurotransmitter tone or gene expression is altered in PD, dyskinesia or associated animal models. The present study utilized the rat unilateral 6-hydroxydopamine (6-OHDA) model of PD/dyskinesia to characterize structural and functional changes taking place in M1 monoamine innervation and gene expression. 6-OHDA caused dopamine pathology in M1, although the lesion was less severe than in the striatum. Rats with 6-OHDA lesions showed a PD motor impairment and developed dyskinesia when given L-DOPA or the D1 receptor agonist, SKF81297. M1 expression of two immediate-early genes (c-Fos and ARC) was strongly enhanced by either L-DOPA or SKF81297. At the same time, expression of genes specifically involved in glutamate and GABA signaling were either modestly affected or unchanged by lesion and/or treatment. We conclude that M1 neurotransmission and signal transduction in the rat 6-OHDA model of PD/dyskinesia mirror features of human PD, supporting the utility of the model to study M1 dysfunction in PD and the elucidation of novel pathophysiological mechanisms and therapeutic targets.

Effects of the beta-adrenergic receptor antagonist Propranolol on dyskinesia and L-DOPA-induced striatal DA efflux in the hemi-parkinsonian rat

Dopamine (DA) replacement therapy with L-DOPA continues to be the primary treatment of Parkinson's disease; however, long-term therapy is accompanied by L-DOPA-induced dyskinesias (LID). Several experimental and clinical studies have established that Propranolol, a β-adrenergic receptor antagonist, reduces LID without affecting L-DOPA's efficacy. However, the exact mechanisms underlying these effects remain to be elucidated. The aim of this study was to evaluate the anti-dyskinetic profile of Propranolol against a panel of DA replacement strategies, as well as elucidate the underlying neurochemical mechanisms. Results indicated that Propranolol, in a dose-dependent manner, reduced LID, without affecting motor performance. Propranolol failed to alter dyskinesia produced by the D1 receptor agonist, SKF81297 (0.08 mg/kg, sc), or the D2 receptor agonist, Quinpirole (0.05 mg/kg, sc). These findings suggested a pre-synaptic mechanism for Propranolol's anti-dyskinetic effects, possibly through modulating L-DOPA-mediated DA efflux. To evaluate this possibility, microdialysis studies were carried out in the DA-lesioned striatum of dyskinetic rats and results indicated that co-administration of Propranolol (20 mg/kg, ip) was able to attenuate L-DOPA- (6 mg/kg, sc) induced DA efflux. Therefore, Propranolol's anti-dyskinetic properties appear to be mediated via attenuation of L-DOPA-induced extraphysiological efflux of DA.