High frequency stimulation of the subthalamic nucleus improves speed of locomotion but impairs forelimb movement in Parkinsonian rats

The effects of L-DOPA on gait abnormalities in a unilateral 6-OHDA rat model of Parkinson's disease

Parkinson's Disease (PD) is a neurodegenerative movement disorder characterized by dopamine (DA) cell loss in the substantia nigra pars compacta (SNc). As PD progresses, patients display disruptions in gait such as changes in posture, bradykinesia, and shortened stride. DA replacement via L-DOPA alleviates many PD symptoms, though its effects on gait are not well demonstrated. This study aimed to assess the relationship between DA lesion, gait, and deficit-induced reversal with L-DOPA. To do so, Sprague-Dawley rats (N = 25, 14 males, 11 females) received unilateral medial forebrain bundle (MFB) DA lesions with 6-hydroxydopamine (6-OHDA). An automated gait analysis system assessed spatiotemporal gait parameters pre- and post-lesion, and after various doses of L-DOPA (0, 3, or 6 mg/kg; s.c.). The forepaw adjusting steps (FAS) test was implemented to evaluate lesion efficacy while the abnormal involuntary movements (AIMs) scale monitored the emergence of L-DOPA-induced dyskinesia (LID). High performance liquid chromatography (HPLC) assessed changes in brain monoamines on account of lesion and treatment. Results revealed lesion-induced impairments in gait, inclusive of max-contact area and step-sequence alterations that were not reversible with L-DOPA. However, the emergence of AIMs were observed at higher doses. Post-mortem, 6-OHDA lesions induced a loss of striatal DA and norepinephrine (NE), while prefrontal cortex (PFC) displayed noticeable reduction in NE but not DA. Our findings indicate that hemiparkinsonian rats display measurable gait disturbances similar to PD patients that are not rescued by DA replacement. Furthermore, non-DA mechanisms such as attention-related NE in PFC may contribute to altered gait and may constitute a novel target for its treatment.

Hordenine improves Parkinsonian-like motor deficits in mice and nematodes by activating dopamine D2 receptor-mediated signaling

Parkinson's disease (PD) is a chronic neurodegenerative disease characterized by selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the striatum, leading to dopamine (DA) deficiency in the striatum and typical motor symptoms. A small molecule as a dietary supplement for PD would be ideal for practical reasons. Hordenine (HOR) is a phenolic phytochemical marketed as a dietary supplement found in cereals and germinated barley, as well as in beer, a widely consumed beverage. This study was aimed to identify HOR as a dopamine D2 receptor (DRD2) agonist in living cells, and investigate the alleviative effect and mechanism of HOR on PD-like motor deficits in mice and nematodes. Our results firstly showed that HOR is an agonist of DRD2, but not DRD1, in living cells. Moreover, HOR could improve the locomotor dysfunction, gait, and postural imbalance in MPTP- or 6-OHDA-induced mice or Caenorhabditis elegans, and prevent α-synuclein accumulation via the DRD2 pathway in C. elegans. Our results suggested that HOR could activate DRD2 to attenuate the PD-like motor deficits, and provide scientific evidence for the safety and reliability of HOR as a dietary supplement.

Longitudinal assessment of motor function following the unilateral intrastriatal 6-hydroxydopamine lesion model in mice

Introduction

Despite the widespread use of the unilateral striatal 6-hydroxydopamine (6-OHDA) lesion model in mice in recent years, the stability of behavioral deficits in the 6-OHDA striatal mouse model over time is not yet clear, raising concerns about using this model to evaluate a compound's long-term therapeutic effects.

Materials and methods

In the current study, mice were tested at regular intervals in the cylinder test and gait analysis beginning 3 days after 6-OHDA injection of 4 and 8 μg and lasting until 56 days post-lesion. Apomorphine-induced rotational test and rotarod test were also performed on Day 23 and 43 post-lesion, respectively. Immunohistochemistry for dopaminergic neurons stained by tyrosine hydroxylase (TH) was also performed.

Results

Our results showed that both the 4 and 8 μg 6-OHDA lesion groups exhibited forelimb use asymmetry with a preference for the ipsilateral (injection) side on Day 3 and until Day 21 post-lesion, but did not show forelimb asymmetry on Day 28 to 56 post-lesion. The 8 μg 6-OHDA lesion group still exhibited forelimb asymmetry on Day 28 and 42 post-lesion, but not on Day 56. The gait analysis showed that the contralateral front and hind step cycles increased from Day 3 to 42 post-lesion and recovered on Day 56 post-lesion. In addition, our results displayed a dose-dependent reduction in TH⁺ cells and TH⁺ fibers, as well as dose-dependent apomorphine-induced rotations. In the rotarod test, the 8 μg 6-OHDA lesion group, but not the 4 μg group, decreased the latency to fall on the rotarod on Day 43 post-lesion.

Conclusion

In summary, unilateral striatal 6-OHDA injections of 4 and 8 μg induced spontaneous motor impairment in mice, which partially recovered starting on Day 28 post-lesion. Forced motor deficits were observed in the 8 g 6-OHDA lesion group, which remained stable on Day 43 post-lesion. In addition, the rotarod test and apomorphine-induced rotational test can distinguish between lesions of different extents and are useful tools for the assessment of functional recovery in studies screening novel potential therapies.

Gait performance of adolescent mice assessed by the CatWalk XT depends on age, strain and sex and correlates with speed and body weight

The automatization of behavioral tests assessing motor activity in rodent models is important for providing robust and reproducible results and evaluating new therapeutics. The CatWalk system is an observer-independent, automated and computerized technique for the assessment of gait performance in rodents. This method has previously been used in adult rodent models of CNS-based movement disorders such as Parkinson's and Huntington's diseases. As motor and gait abnormalities in neuropsychiatric disorders are observed during infancy and adolescence, it became important to validate the CatWalk XT in the gait analysis of adolescent mice and unravel factors that may cause variations in gait performance. Three adolescent wild-type inbred mouse strains, C57BL/6N, DBA/2 and FVB/N, were tested using the CatWalk XT (Version 10.6) for suitable detection settings to characterize several gait parameters at P32 and P42. The same detection settings being suitable for C57BL/6N and DBA/2 mice allowed a direct comparison between the two strains. On the other hand, due to their increased body weight and size, FVB/N mice required different detection settings. The CatWalk XT reliably measured the temporal, spatial, and interlimb coordination parameters in the investigated strains during adolescence. Additionally, significant effects of sex, development, speed and body weight within each strain confirmed the sensitivity of motor and gait functions to these factors. The CatWalk gait analysis of rodents during adolescence, taking the effect of age, strain, sex, speed and body weight into consideration, will decrease intra-laboratory discrepancies and increase the face validity of rodent models of neuropsychiatric disorders.

Magnetothermal nanoparticle technology alleviates parkinsonian-like symptoms in mice

Deep brain stimulation (DBS) has long been used to alleviate symptoms in patients suffering from psychiatric and neurological disorders through stereotactically implanted electrodes that deliver current to subcortical structures via wired pacemakers. The application of DBS to modulate neural circuits is, however, hampered by its mechanical invasiveness and the use of chronically implanted leads, which poses a risk for hardware failure, hemorrhage, and infection. Here, we demonstrate that a wireless magnetothermal approach to DBS (mDBS) can provide similar therapeutic benefits in two mouse models of Parkinson's disease, the bilateral 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and in the unilateral 6-hydroxydopamine (6-OHDA) model. We show magnetothermal neuromodulation in untethered moving mice through the activation of the heat-sensitive capsaicin receptor (transient receptor potential cation channel subfamily V member 1, TRPV1) by synthetic magnetic nanoparticles. When exposed to an alternating magnetic field, the nanoparticles dissipate heat, which triggers reversible firing of TRPV1-expressing neurons. We found that mDBS in the subthalamic nucleus (STN) enables remote modulation of motor behavior in healthy mice. Moreover, mDBS of the STN reversed the motor deficits in a mild and severe parkinsonian model. Consequently, this approach is able to activate deep-brain circuits without the need for permanently implanted hardware and connectors.

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.

Striatal Acetylcholine Helps to Preserve Functional Outcomes in a Mouse Model of Stroke

Acetylcholine (ACh) has been suggested to facilitate plasticity and improve functional recovery after different types of brain lesions. Interestingly, numerous studies have shown that striatal cholinergic interneurons are relatively resistant to acute ischemic insults, but whether ACh released by these neurons enhances functional recovery after stroke is unknown. We investigated the role of endogenous striatal ACh in stroke lesion volume and functional outcomes following middle cerebral artery occlusion to induce focal ischemia in striatum-selective vesicular acetylcholine transporter-deficient mice (stVAChT-KO). As transporter expression is almost completely eliminated in the striatum of stVAChT-KO mice, ACh release is nearly abolished in this area. Conversely, in other brain areas, VAChT expression and ACh release are preserved. Our results demonstrate a larger infarct size after ischemic insult in stVAChT-KO mice, with more pronounced functional impairments and increased mortality than in littermate controls. These changes are associated with increased activation of GSK-3, decreased levels of β-catenin, and a higher permeability of the blood–brain barrier in mice with loss of VAChT in striatum neurons. These results support a framework in which endogenous ACh secretion originating from cholinergic interneurons in the striatum helps to protect brain tissue against ischemia-induced damage and facilitates brain recovery by supporting blood–brain barrier function.

Rat subthalamic stimulation: Evaluating stimulation-induced dyskinesias, choosing stimulation currents and evaluating the anti-akinetic effect in the cylinder test

In experimental deep brain stimulation of the subthalamic nucleus (STN HFS), stimulation currents just below the appearance threshold of stimulation-induced dyskinesias has often been used. The behavioral effect of STN HFS can be measured by the reversal of forelimb use asymmetry produced by hemiparkinsonism can be measured with the cylinder test among other tests. We used 18 Wistar rats with 6-hydroxydopamine induced hemiparkinsonism to test a customized scale to rate the severity of stimulation-induced dyskinesia; we then used these ratings to choose low and high stimulation currents. Subsequent cylinder tests showed that stimulation at the higher current, inducing mild and short-lived dyskinesias, was required for robust improvement in forelimb use, contradicting the use of currents below stimulation-induced dyskinesia threshold. It was also beneficial to separately count both all touches and first touches with the cylinder wall; this provided additional sensitivity and robustness to our results.

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Scoring stimulation-induced dyskinesias can be used as a quantitative measure of dyskinesias and to choose stimulation currents.

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Cylinder test scoring separately for both first and all touches can improve both sensitivity and reliability.

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STN HFS at a current producing short-lived dyskinesias was required for robust improvement in forelimb use asymmetry.

Botulinum toxin A injection into the entopeduncular nucleus improves dynamic locomotory parameters in hemiparkinsonian rats

Parkinson’s disease is associated with hyperactivity of the subthalamic nucleus (STN), contributing to motor and gait disturbances. Although deep brain stimulation of the STN alleviates certain motor dysfunction, its specific effect on gait abnormalities remains controversial. This study investigated the long-term changes in locomotion following direct infusions of botulinum toxin-A into the globus pallidus internal segment (GPi) to suppress the flow of information from the STN to the GPi in a hemiparkinsonian rat model. Static and dynamic gait parameters were quantified using a CatWalk apparatus. Interestingly, botulinum toxin-A at 0.5 ng significantly reduced only the dynamic gait parameters of hemiparkinsonian rats at 1 week and 1 month post-infusion, while static gait parameters did not change. This study offers new insights into the complexity of basal ganglia in locomotor control and shows the potential of central infusion of botulinum toxin-A as a novel intervention in the study of experimental hemiparkinson’s disease.

Systematic data analysis and data mining in CatWalk gait analysis by heat mapping exemplified in rodent models for neurodegenerative diseases

BACKGROUND

Motor impairment appears as a characteristic symptom of several diseases and injuries. Therefore, tests for analyzing motor dysfunction are widely applied across preclinical models and disease stages. Among those, gait analysis tests are commonly used, but they generate a huge number of gait parameters. Thus, complications in data analysis and reporting raise, which often leads to premature parameter selection.

NEW METHODS

In order to avoid arbitrary parameter selection, we present here a systematic initial data analysis by utilizing heat-maps for data reporting. We exemplified this approach within an intervention study, as well as applied it to two longitudinal studies in rodent models related to Parkinson's disease (PD) and Huntington disease (HD).

RESULTS

The systematic initial data analysis (IDA) is feasible for exploring gait parameters, both in experimental and longitudinal studies. The resulting heat maps provided a visualization of gait parameters within a single chart, highlighting important clusters of differences.

COMPARISON WITH EXISTING METHOD

Often, premature parameter selection is practiced, lacking comprehensiveness. Researchers often use multiple separated graphs on distinct gait parameters for reporting. Additionally, negative results are often not reported.

CONCLUSIONS

Heat mapping utilized in initial data analysis is advantageous for reporting clustered gait parameter differences in one single chart and improves data mining.

Effects of subthalamic deep brain stimulation on striatal metabolic connectivity in a rat hemiparkinsonian model

Deep brain stimulation (DBS) in the subthalamic nucleus (STN) has been successfully used for the treatment of advanced Parkinson's disease, although the underlying mechanisms are complex and not well understood. There are conflicting results about the effects of STN-DBS on neuronal activity of the striatum, and its impact on functional striatal connectivity is entirely unknown. We therefore investigated how STN-DBS changes cerebral metabolic activity in general and striatal connectivity in particular. We used ipsilesional STN stimulation in a hemiparkinsonian rat model in combination with [¹⁸F]FDOPA-PET, [¹⁸F]FDG-PET and metabolic connectivity analysis. STN-DBS reversed ipsilesional hypometabolism and contralesional hypermetabolism in hemiparkinsonian rats by increasing metabolic activity in the ipsilesional ventrolateral striatum and by decreasing it in the contralesional hippocampus and brainstem. Other STN-DBS effects were subject to the magnitude of dopaminergic lesion severity measured with [¹⁸F]FDOPA-PET, e.g. activation of the infralimbic cortex was negatively correlated to lesion severity. Connectivity analysis revealed that, in healthy control animals, left and right striatum formed a bilateral functional unit connected by shared cortical afferents, which was less pronounced in hemiparkinsonian rats. The healthy striatum was metabolically connected to the ipsilesional substantia nigra in hemiparkinsonian rats only (OFF condition). STN-DBS (ON condition) established a new functional striatal network, in which interhemispheric striatal connectivity was strengthened, and both the dopamine-depleted and the healthy striatum were functionally connected to the healthy substantia nigra. We conclude that both unilateral dopamine depletion and STN-DBS affect the whole brain and alter complex interhemispheric networks.

Summary: Deep brain stimulation in the subthalamic nucleus in rats with a unilateral dopaminergic lesion established a new functional interhemispheric striatal network.

Gait Analysis for Early Detection of Motor Symptoms in the 6-OHDA Rat Model of Parkinson's Disease

Computer-supported gait analysis has proven to be effective for the comprehensive assessment of gait changes in rodent models of neurodegenerative and neurological disorders. However, full characterization of individual gait parameters is required for specific neurological or neurodegenerative disorders such as Parkinson's disease (PD). Gait disturbances in particular present as the most constraining set of symptoms in PD, finally depriving patients from most activities of normal daily living. In this study, we have characterized the gait pattern abnormalities observed in two rat models of PD: the medial forebrain bundle (MFB) 6-OHDA lesion model and the striatal 6-OHDA lesion model. Our data indicates significant changes in 21 different gait parameters in the MFB lesion cohort. We observed a steady decline in the overall walking speed and cadence, as well as significant alterations in the gait parameters stride length, initial dual stance, paw print position, step cycle, swing phase of the step cycle, stand index, phase dispersion, print length, and print area in at least one of the paws. These alterations correlated with the extent of tyrosine hydroxylase (TH) neuronal loss observed in this group. These alterations were detected as early as 1 week post lesion. In contrast, limited gait dysfunction was detected in the striatal lesion cohort related to the low level of TH neuronal loss detected in this group. In this study we have demonstrated that gait analysis is a reliable method for the detection of motor deficiencies in a MFB 6-OHDA lesion model of PD and may prove a clinically relevant, low impact method of testing functional impairment as early as 1 week post lesion.

Subthalamic Nucleus Deep Brain Stimulation Does Not Modify the Functional Deficits or Axonopathy Induced by Nigrostriatal α-Synuclein Overexpression

Subthalamic nucleus deep brain stimulation (STN DBS) protects dopaminergic neurons of the substantia nigra pars compacta (SNpc) against 6-OHDA and MPTP. We evaluated STN DBS in a parkinsonian model that displays α-synuclein pathology using unilateral, intranigral injections of recombinant adeno-associated virus pseudotype 2/5 to overexpress wildtype human α-synuclein (rAAV2/5 α-syn). A low titer of rAAV2/5 α-syn results in progressive forelimb asymmetry, loss of striatal dopaminergic terminal density and modest loss of SNpc dopamine neurons after eight weeks, corresponding to robust human-Snca expression and no effect on rat-Snca, Th, Bdnf or Trk2. α-syn overexpression increased phosphorylation of ribosomal protein S6 (p-rpS6) in SNpc neurons, a readout of trkB activation. Rats received intranigral injections of rAAV2/5 α-syn and three weeks later received four weeks of STN DBS or electrode implantation that remained inactive. STN DBS did not protect against α-syn-mediated deficits in forelimb akinesia, striatal denervation or loss of SNpc neuron, nor did STN DBS elevate p-rpS6 levels further. ON stimulation, forelimb asymmetry was exacerbated, indicating α-syn overexpression-mediated neurotransmission deficits. These results demonstrate that STN DBS does not protect the nigrostriatal system against α-syn overexpression-mediated toxicity. Whether STN DBS can be protective in other models of synucleinopathy is unknown.

Neurobehavioral testing in subarachnoid hemorrhage: A review of methods and current findings in rodents

The most important aspect of a preclinical study seeking to develop a novel therapy for neurological diseases is whether the therapy produces any clinically relevant functional recovery. For this purpose, neurobehavioral tests are commonly used to evaluate the neuroprotective efficacy of treatments in a wide array of cerebrovascular diseases and neurotrauma. Their use, however, has been limited in experimental subarachnoid hemorrhage studies. After several randomized, double-blinded, controlled clinical trials repeatedly failed to produce a benefit in functional outcome despite some improvement in angiographic vasospasm, more rigorous methods of neurobehavioral testing became critical to provide a more comprehensive evaluation of the functional efficacy of proposed treatments. While several subarachnoid hemorrhage studies have incorporated an array of neurobehavioral assays, a standardized methodology has not been agreed upon. Here, we review neurobehavioral tests for rodents and their potential application to subarachnoid hemorrhage studies. Developing a standardized neurobehavioral testing regimen in rodent studies of subarachnoid hemorrhage would allow for better comparison of results between laboratories and a better prediction of what interventions would produce functional benefits in humans.

Validity and reliability of the CatWalk system as a static and dynamic gait analysis tool for the assessment of functional nerve recovery in small animal models

INTRODUCTION

A range of behavioral testing paradigms have been developed for the research of central and peripheral nerve injuries with the help of small animal models. Following any nerve repair strategy, improved functional outcome may be the most important evidence of axon regeneration. A novel automated gait analysis system, the CatWalk^™, can measure dynamic as well as static gait patterns of small animals. Of most interest in detecting functional recovery are in particular dynamic gait parameters, coordination measures, and the intensity of the animals paw prints. This article is designed to lead to a more efficient choice of CatWalk parameters in future studies concerning the functional evaluation of nerve regeneration and simultaneously add to better interstudy comparability.

METHODS

The aims of the present paper are threefold: (1) to describe the functional method of CatWalk gait analysis, (2) to characterize different parameters acquired by CatWalk gait analysis, and to find the most frequently used parameters as well as (3) to compare their reliability and validity throughout the different studies.

RESULTS

In the reviewed articles, the most frequently used parameters were Swing Duration (30), Print Size (27), Stride Length (26), and Max Contact Area (24). Swing Duration was not only frequently used but was also the most reliable and valid parameter. Therefore, we hypothesize that Swing Duration constitutes an important parameter to be chosen for future studies, as it has the highest level of reliability and validity.

CONCLUSION

In conclusion, CatWalk can be used as a complementary approach to other behavioral testing paradigms to assess clinically relevant behavioral benefits, with the main advantage that this system demonstrates both static and dynamic gait parameters at the same time. Due to limited reliability and validity of certain parameters, we recommend that only the most frequently assessed parameters should be used in the future.

Subthalamic Nucleus Deep Brain Stimulation Employs trkB Signaling for Neuroprotection and Functional Restoration

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is the most common neurosurgical treatment for Parkinson's disease motor symptoms. In preclinical models, STN DBS provides neuroprotection for substantia nigra (SN) dopamine neurons and increases BDNF in the nigrostriatal system and primary motor cortex. However, whether BDNF signaling in the SN participates in the neuroprotective effects of DBS remains unknown. We demonstrate that STN DBS in male rats activates signaling downstream of tropomyosin receptor kinase type B (trkB), namely, phosphorylation of Akt and ribosomal protein S6, in SN neurons. Long-term trkB blockade abolished STN DBS-mediated neuroprotection of SN neurons following progressive 6-hydroxydopamine lesion and was associated with decreased phosphorylated ribosomal protein S6 immunoreactivity. Acute trkB blockade in rats with stable nigrostriatal denervation attenuated the forelimb akinesia improvement normally induced by STN DBS. These results suggest that STN DBS increases BDNF-trkB signaling to contribute to the neuroprotective and symptomatic efficacy of STN DBS.SIGNIFICANCE STATEMENT Subthalamic nucleus deep brain stimulation (STN DBS) is increasingly used in mid- to late-stage Parkinson's disease (PD) but with an incomplete knowledge of its molecular mechanisms. STN DBS is neuroprotective against neurotoxicants in animal models and increases BDNF. This study is the first to show that BDNF signaling through the cognate tropomyosin receptor kinase type B (trkB) receptor occurs in substantia nigra pars compacta neurons and is required for neuroprotection. In addition, blockade of trkB unexpectedly reduced the functional benefit of STN DBS on a short timescale that is inconsistent with canonical trkB signaling pathways, suggesting a noncanonical role for trkB in STN DBS-mediated behavioral effects. Together, these data implicate trkB signaling in the symptomatic efficacy and disease-modifying potential of STN DBS.

Vitamin C Deficiency Causes Severe Defects in the Development of the Neonatal Cerebellum and in the Motor Behaviors of Gulo(-/-) Mice

AIMS

The developing brain of a neonate is particularly susceptible to damage by vitamin C deficiency because of its rapid growth and immature antioxidant system. Cognitive impairment and sensory motor deficits are found in the adult brain upon vitamin C deficiency. Therefore, the aim of this study was to clarify the role of vitamin C in its own right and its related mechanisms in Gulo(-/-) mice incapable of synthesizing vitamin C.

RESULTS

When vitamin C supplementation was ceased for 2 weeks until delivery, stillbirths and a significant reduction in neonatal mice were observed and the growth of neonates was remarkably decreased. In addition, intraparenchymal hemorrhages were found in most of the brains, especially in the stillborn neonates. In addition, the levels of malondialdehyde (MDA) and 8-isoprostanes were increased and structural abnormalities were found in the cortex, hippocampus, and cerebellum. Especially, vitamin C deficiency caused the failure of or a delay in the formation of cerebellar fissures accompanied by abnormal foliation and altered Purkinje cell alignment. In the developed adult brains from vitamin C-deficient Gulo(-/-) mice, the levels of glutathione, MDA, nitrate, IL-6, TNF-α, and Bax were increased and the expression of the GABRA6 and calbindin-28k was decreased. Due to atrophy of the granule and Purkinje cells, the motor behavior of vitamin C-deficient Gulo(-/-) mice declined.

INNOVATION AND CONCLUSION

Vitamin C deficiency during gestation induces intraparenchymal hemorrhages and severe defects in the development of the cerebellum. In fully developed brains, it induces the functional impairment by altering the cellular composition in the cerebellum.

Biocompatibility of a polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+) for neural implants

Background

The flexibility of implantable neural probes has increased during the last 10 years, starting with stiff materials such as silicone to more flexible materials like polyimide. We have developed a novel polymer based on Off-Stoichiometry Thiol-Enes + Epoxy (OSTE+, consisting of a thiol, two allyls, an epoxy resin and two initiators), which is up to 100 times more flexible than polyimide. Since a flexible neural probe should be more biocompatible than a stiff probe, an OSTE+ probe should be more biocompatible than one composed of a more rigid material. We have investigated the toxicity of OSTE+ as well as of OSTE+ that had been incubated in water for a week (OSTE+H₂O) using MTT assays with mouse L929 fibroblasts. We found that OSTE+ showed cytotoxicity, but OSTE+H₂O did not. Extracts were analyzed using LC-MS and GC-MS in order to identify leaked chemicals.

Results

Most constituents were found in extracts of OSTE+, whereas only initiators were found in OSTE+H₂O extracts. The detected levels of each chemical found in the LC-MS and the GC-MS analysis were below the toxicity level when compared to MTT assays of all the individual chemicals, except for one of the initiators that had an IC₅₀ value close to the detected levels.

Conclusion

Our notion is that the toxicity of OSTE+ was caused by one of the initiators, by impurities in the constituents or by synergistic effects of low doses of leaked chemicals. However, our conclusion is that if OSTE+ is incubated for one week in water, OSTE+ is not cytotoxic and suitable for further in vivo studies.

High-Frequency Stimulation of the Rat Entopeduncular Nucleus Does Not Provide Functional or Morphological Neuroprotection from 6-Hydroxydopamine

Deep brain stimulation (DBS) is the most common neurosurgical treatment for Parkinson’s disease (PD). Whereas the globus pallidus interna (GPi) has been less commonly targeted than the subthalamic nucleus (STN), a recent clinical trial suggests that GPi DBS may provide better outcomes for patients with psychiatric comorbidities. Several laboratories have demonstrated that DBS of the STN provides neuroprotection of substantia nigra pars compacta (SNpc) dopamine neurons in preclinical neurotoxin models of PD and increases brain-derived neurotrophic factor (BDNF). However, whether DBS of the entopeduncular nucleus (EP), the homologous structure to the GPi in the rat, has similar neuroprotective potential in preclinical models has not been investigated. We investigated the impact of EP DBS on forelimb use asymmetry and SNpc degeneration induced by 6-hydroxydopamine (6-OHDA) and on BDNF levels. EP DBS in male rats received unilateral, intrastriatal 6-OHDA and ACTIVE or INACTIVE stimulation continuously for two weeks. Outcome measures included quantification of contralateral forelimb use, stereological assessment of SNpc neurons and BDNF levels. EP DBS 1) did not ameliorate forelimb impairments induced by 6-OHDA, 2) did not provide neuroprotection for SNpc neurons and 3) did not significantly increase BDNF levels in any of the structures examined. These results are in sharp contrast to the functional improvement, neuroprotection and BDNF-enhancing effects of STN DBS under identical experimental parameters in the rat. The lack of functional response to EP DBS suggests that stimulation of the rat EP may not represent an accurate model of clinical GPi stimulation.

Low-cost three-dimensional gait analysis system for mice with an infrared depth sensor

Three-dimensional (3D) open-field gait analysis of mice is an essential procedure in genetic and nerve regeneration research. Existing gait analysis systems are generally expensive and may interfere with the natural behaviors of mice because of optical markers and transparent floors. In contrast, the proposed system captures the subjects shape from beneath using a low-cost infrared depth sensor (Microsoft Kinect) and an opaque infrared pass filter. This means that we can track footprints and 3D paw-tip positions without optical markers or a transparent floor, thereby preventing any behavioral changes. Our experimental results suggest with healthy mice that they are more active on opaque floors and spend more time in the center of the open-field, when compared with transparent floors. The proposed system detected footprints with a comparable performance to existing systems, and precisely tracked the 3D paw-tip positions in the depth image coordinates.

Coexistence of Gait Disturbances and Chorea in Experimental Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by an expanded CAG repeat. The clinical features are progressive motor dysfunction, cognitive deterioration, and psychiatric disturbances. Unpredictable choreic movements, among the most characteristic hallmarks, may contribute to gait disturbances and loss of balance in HD individuals. In this study, we aimed to investigate and characterize the gait abnormalities and choreic movements in a transgenic rat model of HD (tgHD). TgHD presents typical neuropathological, neurophysiological, and behavioral aspects mimicking some of the key features of human HD and is the only described experimental model for HD that exhibits choreiform movements. We used the Catwalk, with emphasis on static and dynamic gait parameters, to test the hypothesis that at symptomatic age (9 months) the dynamic measures of gait in HD are altered and coexist with choreiform movements. Our results showed that the dynamic parameters seem to be more affected than static parameters at this age in tgHD rats. The number of steps and step cycles and swing speed of the paws were increased in tgHD rat in comparison to wild-type controls. Our study demonstrates that gait abnormalities coexist with chorea rather than being caused by it. These symptoms may originate from distinct networks in the basal ganglia and downstream connections.

Cerebellar transcriptional alterations with Purkinje cell dysfunction and loss in mice lacking PGC-1α

Alterations in the expression and activity of the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator-1α (ppargc1a or PGC-1α) have been reported in multiple movement disorders, yet it is unclear how a lack of PGC-1α impacts transcription and function of the cerebellum, a region with high PGC-1α expression. We show here that mice lacking PGC-1α exhibit ataxia in addition to the previously described deficits in motor coordination. Using q-RT-PCR in cerebellar homogenates from PGC-1α^−/− mice, we measured expression of 37 microarray-identified transcripts upregulated by PGC-1α in SH-SY5Y neuroblastoma cells with neuroanatomical overlap with PGC-1α or parvalbumin (PV), a calcium buffer highly expressed by Purkinje cells. We found significant reductions in transcripts with synaptic (complexin1, Cplx1; Pacsin2), structural (neurofilament heavy chain, Nefh), and metabolic (isocitrate dehydrogenase 3a, Idh3a; neutral cholesterol ester hydrolase 1, Nceh1; pyruvate dehydrogenase alpha 1, Pdha1; phytanoyl-CoA hydroxylase, Phyh; ubiquinol-cytochrome c reductase, Rieske iron-sulfur polypeptide 1, Uqcrfs1) functions. Using conditional deletion of PGC-1α in PV-positive neurons, we determined that 50% of PGC-1α expression and a reduction in a subset of these transcripts could be explained by its concentration in PV-positive neuronal populations in the cerbellum. To determine whether there were functional consequences associated with these changes, we conducted stereological counts and spike rate analysis in Purkinje cells, a cell type rich in PV, from PGC-1α^−/− mice. We observed a significant loss of Purkinje cells by 6 weeks of age, and the remaining Purkinje cells exhibited a 50% reduction in spike rate. Together, these data highlight the complexity of PGC-1α's actions in the central nervous system and suggest that dysfunction in multiple cell types contribute to motor deficits in the context of PGC-1α deficiency.

Progesterone reduces secondary damage, preserves white matter, and improves locomotor outcome after spinal cord contusion

Progesterone is an anti-inflammatory and promyelinating agent after spinal cord injury, but its effectiveness on functional recovery is still controversial. In the current study, we tested the effects of chronic progesterone administration on tissue preservation and functional recovery in a clinically relevant model of spinal cord lesion (thoracic contusion). Using magnetic resonance imaging, we observed that progesterone reduced both volume and rostrocaudal extension of the lesion at 60 days post-injury. In addition, progesterone increased the number of total mature oligodendrocytes, myelin basic protein immunoreactivity, and the number of axonal profiles at the epicenter of the lesion. Further, progesterone treatment significantly improved motor outcome as assessed using the Basso-Bresnahan-Beattie scale for locomotion and CatWalk gait analysis. These data suggest that progesterone could be considered a promising therapeutical candidate for spinal cord injury.

Gait analysis in three different 6-hydroxydopamine rat models of Parkinson's disease

Gait deficits are important clinical symptoms of Parkinson's disease (PD) but are rarely studied. In this study we made three different rat PD models by administration of 6-hydroxydopamine into caudate putamen (CPU), medial forebrain bundle (MFB) and substantia nigra compact (SNC). We evaluated the gait changes in these models by using a computer-assisted CatWalk system. Correlations of gait parameters with tyrosine hydroxylase protein levels in the CPU and SNC were also investigated. The gait readouts were significantly impaired in both the MFB and SNC groups. However, the MFB group showed a more pronounced impairment than the SNC group. In contrast, only mild and incomplete gait impairment occurred in the CPU group. In addition, some gait parameters demonstrated close correlation with the protein levels of TH. This paper suggests that the 6-hydroxydopamine-induced MFB model is more propitious to study gait dysfunction than the other two models and the CatWalk system can provide reliable and objective criteria to stratify gait changes arising from 6-hydroxydopamine lesioned rats. These findings may hold promise in the study of PD disease progression and new therapeutic methods.

The need for speed in rodent locomotion analyses

Locomotion analysis is now widely used across many animal species to understand the motor defects in disease, functional recovery following neural injury, and the effectiveness of various treatments. More recently, rodent locomotion analysis has become an increasingly popular method in a diverse range of research. Speed is an inseparable aspect of locomotion that is still not fully understood, and its effects are often not properly incorporated while analyzing data. In this hybrid manuscript, we accomplish three things: (1) review the interaction between speed and locomotion variables in rodent studies, (2) comprehensively analyze the relationship between speed and 162 locomotion variables in a group of 16 wild-type mice using the CatWalk gait analysis system, and (3) develop and test a statistical method in which locomotion variables are analyzed and reported in the context of speed. Notable results include the following: (1) over 90% of variables, reported by CatWalk, were dependent on speed with an average R(2) value of 0.624, (2) most variables were related to speed in a nonlinear manner, (3) current methods of controlling for speed are insufficient, and (4) the linear mixed model is an appropriate and effective statistical method for locomotion analyses that is inclusive of speed-dependent relationships. Given the pervasive dependency of locomotion variables on speed, we maintain that valid conclusions from locomotion analyses cannot be made unless they are analyzed and reported within the context of speed.

Limiting glutamate transmission in a Vglut2-expressing subpopulation of the subthalamic nucleus is sufficient to cause hyperlocomotion

The subthalamic nucleus (STN) is a key area of the basal ganglia circuitry regulating movement. We identified a subpopulation of neurons within this structure that coexpresses Vglut2 and Pitx2, and by conditional targeting of this subpopulation we reduced Vglut2 expression levels in the STN by 40%, leaving Pitx2 expression intact. This reduction diminished, yet did not eliminate, glutamatergic transmission in the substantia nigra pars reticulata and entopeduncular nucleus, two major targets of the STN. The knockout mice displayed hyperlocomotion and decreased latency in the initiation of movement while preserving normal gait and balance. Spatial cognition, social function, and level of impulsive choice also remained undisturbed. Furthermore, these mice showed reduced dopamine transporter binding and slower dopamine clearance in vivo, suggesting that Vglut2-expressing cells in the STN regulate dopaminergic transmission. Our results demonstrate that altering the contribution of a limited population within the STN is sufficient to achieve results similar to STN lesions and high-frequency stimulation, but with fewer side effects.

Comparison of CatWalk analysis and von Frey testing for pain assessment in a rat model of nerve crush plus inflammation

STUDY DESIGN

Assessment of pain-related behavior and immunohistology of the dorsal root ganglion in a rat model.

OBJECTIVE

To investigate pain-related behavior in a rat model of nerve crush plus inflammation using the CatWalk system.

SUMMARY OF BACKGROUND DATA

A definitive method for evaluating animal models of lumbar disease has not been established. Von Frey testing has often been used in this type of study, but the reliability remains in question. The CatWalk system is a computer-assisted apparatus for analyzing gait that provides an automated way to assess gait function during pain. However, there have been few reports using this system for models of lumbar disease.

METHODS

Fourteen rats were divided into 2 groups: a treatment group and a sham group. For the treatment group, nucleus pulposus was applied to the sciatic nerve and the sciatic nerve was pinched. Two different methods for assessment of pain-related behavior, von Frey testing and CatWalk analysis, were used before surgery and at 4 and 7 days after surgery. Immunohistochemistry was used to examine calcitonin gene-related peptide expression in L4 to L6 dorsal root ganglia.

RESULTS

No significant differences were found between the treatment and sham control groups using von Frey testing. However, significant differences in 4 parameters were found between the 2 groups using the CatWalk system (P < 0.05). The proportion of calcitonin gene-related peptide-immunoreactive neurons was higher in the treatment group than in the control group (P < 0.05).

CONCLUSION

Our results demonstrate that the CatWalk system is useful for the measurement of pain-related behavioral change in our rat model in which nociception was indicated at a cellular level. Although further studies are needed, we think that this system is a valid alternative method for the evaluation of models of lumbar disease in rodents.

GABAA-receptor activation in the subthalamic nucleus compensates behavioral asymmetries in the hemiparkinsonian rat

The subthalamic nucleus (STN) has a pivotal role in the pathophysiology of Parkinson's disease (PD). Modulation of STN activity (by lesions, pharmacological or electrical stimulation) has been shown to improve motor parameters in PD patients and in animal models of PD. In an attempt to characterize the neurochemical bases for such antiparkinsonian action, we address specific neurotransmitter systems via local pharmacological manipulation of the STN in hemiparkinsonian rats. Here, we have focused on the GABAergic and glutamatergic receptors in the STN. In animals with unilateral 6-hydroxydopamine lesions of the nigro-striatal tract, we administered either the selective GABAA-agonist muscimol (0.5 μg and 1.0 μg), the non-competitive N-methyl-d-aspartate (NMDA)-antagonist MK-801 (dizocilpine; 2.5 μg), or vehicle (0.25 μl) into the STN. The effects of GABAergic and glutamatergic modulation of the STN on motor parameters were assessed by gauging rotational behavior and locomotion. Application of muscimol ipsilateral to the side of dopamine-depletion influenced turning behavior in a dose-dependent fashion, with the low dose re-adjusting turning behavior to a non-biased distribution, and the high dose evoking contraversive turning. The administration of MK-801 did not have such effects. These findings give evidence for the involvement of GABAergic activation in the STN in the compensation of motor asymmetries in the hemiparkinsonian rat, whereas N-methyl-d-aspartate (NMDA)-antagonism was ineffective in this model of PD.

Quantitative assessment of gait and neurochemical correlation in a classical murine model of Parkinson's disease

Background

Gait deficits are important clinical symptoms of Parkinson’s disease (PD). However, existing behavioral tests for the detection of motor impairments in rodents with systemic dopamine depletion only measure akinesia and dyskinesia, and data focusing on gait are scarce. We evaluated gait changes in the methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced C57BL/6 murine model of PD by using a computer-assisted CatWalk system. Correlations of gait parameters with tyrosine hydroxylase (TH) protein levels in the substantia nigra (SN) were also investigated.

Results

The gait readouts, including the walking duration, variation of walking speed, step cycle, duty cycle, stance, initial dual stance, terminal dual stance, three- and four-point supports, and the base of support between hind limbs was noted to increase significantly one week after MPTP injection. In contrast, values of the stride length, cadence, swing speed, and diagonal dual support decreased substantially following MPTP treatment (p < 0.05). All of these changes lasted for three weeks after the last MPTP administration. Except for the stance in the fore limbs and the swing speed in the hind limbs, the gait variability in the PD mice showed a closer correlation with the protein levels of TH in the SN than the walking distances in the conventional open field test. Coordination parameters of the regularity index and step pattern were not affected in mice treated with MPTP.

Conclusion

Data of the study suggest that the computer-assisted CatWalk system can provide reliable and objective criteria to stratify gait changes arising from MPTP-induced bilateral lesions in C57/BL6 mice. The extent of gait changes was noted to correlate with the expression of the biomarker for dopaminergic neurons. This novel analytical method may hold promise in the study of disease progression and new drug screening in a murine PD model.

Characterizing effects of subthalamic nucleus deep brain stimulation on methamphetamine-induced circling behavior in hemi-Parkinsonian rats

The unilateral 6-hydroxydopamine (6-OHDA) lesioned rat model is frequently used to study the effects of subthalamic nucleus (STN) deep brain stimulation (DBS) for the treatment of Parkinson's disease. However, systematic knowledge of the effects of DBS parameters on behavior in this animal model is lacking. The goal of this study was to characterize the effects of DBS on methamphetamine-induced circling in the unilateral 6-OHDA lesioned rat. DBS parameters tested include stimulation amplitude, stimulation frequency, methamphetamine dose, stimulation polarity, and anatomical location of the electrode. When an appropriate stimulation amplitude and dose of methamphetamine were applied, high-frequency stimulation (> 130 Hz), but not low frequency stimulation (< 10 Hz), reversed the bias in ipsilateral circling without inhibiting movement. This characteristic frequency tuning profile was only generated when at least one electrode used during bipolar stimulation was located within the STN. No difference was found between bipolar stimulation and monopolar stimulation when the most effective electrode contact was selected, indicating that monopolar stimulation could be used in future experiments. Methamphetamine-induced circling is a simple, reliable, and sensitive behavioral test and holds potential for high-throughput study of the effects of STN DBS in unilaterally lesioned rats.

Late-onset Parkinsonism in NFκB/c-Rel-deficient mice

Activation of the nuclear factor κB/c-Rel can increase neuronal resilience to pathological noxae by regulating the expression of pro-survival manganese superoxide dismutase (MnSOD, now known as SOD2) and Bcl-xL genes. We show here that c-Rel-deficient (c-rel(-/-)) mice developed a Parkinson's disease-like neuropathology with ageing. At 18 months of age, c-rel(-/-) mice exhibited a significant loss of dopaminergic neurons in the substantia nigra pars compacta, as assessed by tyrosine hydroxylase-immunoreactivity and Nissl staining. Nigral degeneration was accompanied by a significant loss of dopaminergic terminals and a significant reduction of dopamine and homovanillic acid levels in the striatum. Mice deficient of the c-Rel factor exhibited a marked immunoreactivity for fibrillary α-synuclein in the substantia nigra pars compacta as well as increased expression of divalent metal transporter 1 (DMT1) and iron staining in both the substantia nigra pars compacta and striatum. Aged c-rel(-/-) mouse brain were characterized by increased microglial reactivity in the basal ganglia, but no astrocytic reaction. In addition, c-rel(-/-) mice showed age-dependent deficits in locomotor and total activity and various gait-related deficits during a catwalk analysis that were reminiscent of bradykinesia and muscle rigidity. Both locomotor and gait-related deficits recovered in c-rel(-/-) mice treated with l-3,4-dihydroxyphenylalanine. These data suggest that c-Rel may act as a regulator of the substantia nigra pars compacta resilience to ageing and that aged c-rel(-/-) mice may be a suitable model of Parkinson's disease.

A combined in vivo neurochemical and electrophysiological analysis of the effect of high-frequency stimulation of the subthalamic nucleus on 5-HT transmission

Movement disability in advanced Parkinson's disease (PD) can be treated by high frequency stimulation (HFS) of the subthalamic nucleus (STN) but some patients experience psychiatric side-effects including depression, which is strongly linked to decreases in 5-hydroxytryptamine (5-HT). The current study investigated the effect of bilateral STN HFS on extracellular 5-HT in brain regions of anesthetized and freely moving rats as measured with microdialysis. Parallel in vivo electrophysiological experiments allowed a correlation of changes in extracellular 5-HT with the firing of 5-HT neurons. Bilateral STN HFS decreased (by up to 25%) extracellular levels of 5-HT in both striatum and medial prefrontal cortex of anesthetized rats. STN HFS also decreased extracellular 5-HT in the medial prefrontal cortex of freely moving rats. This decrease in extracellular 5-HT persisted after turning off the stimulation, and was present in dopamine-denervated rats. As with changes in extracellular 5-HT, in anesthetized rats STN HFS evoked a decrease in the in vivo firing of midbrain raphe 5-HT neurons that also persisted after cessation of stimulation. These data provide neurochemical evidence for an inhibition of 5-HT neurotransmission by STN HFS, which may contribute to its psychiatric side effects and guide therapeutic options.

Mild dopaminergic lesions are accompanied by robust changes in subthalamic nucleus activity

The subthalamic nucleus (STN) is a major player in the input and output of the basal ganglia motor circuitry. The neuronal regular firing pattern of the STN changes into a pathological bursting mode in both advanced Parkinson's disease (PD) and in PD animals models with severe dopamine depletion. One of the current hypothesis, based on clinical and experimental evidence, is that this typical burst activity is responsible for some of the principal motor symptoms. In the current study we tested whether mild DA depletion, mimicking early stages of PD, induced deficits in motor behaviour and changes in STN neuronal activity. The present study demonstrated that rats with a mild lesion (20-40% loss of DA neurons) and a slowed motor response, but without gross motor abnormalities already have an increased number of bursty STN neurons under urethane anaesthesia. These findings indicate that the early increase in STN burst activity is a compensatory mechanism to maintain the dopamine homeostasis in the basal ganglia.

Automated gait analysis in bilateral parkinsonian rats and the role of L-DOPA therapy

Gait disturbances and postural instability represent major sources of morbidity in Parkinson's disease (PD), and respond poorly to current treatment options. Some aspects of gait disturbances can be observed in rodent models of PD; however, knowledge regarding the stability of rodent gait patterns over time is lacking. Here we investigated the temporal constancy and reproducibility of gait patterns in neurologically intact and bilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, by using an automated quantitative gait analysis method (CatWalk). The bilateral neurotoxin injections into the medial forebrain bundle resulted in an average dopamine (DA) loss of 70% in each striata, which corresponds to the DA levels observed in moderate-mid stage human PD. Rats were tested weekly during one month, and we found that in intact rats all parameters investigated remained constant over multiple tests. The 6-OHDA lesioned rats were impaired in several aspects of gait, such as stride length, swing speed, stance duration, step cycle duration, and base of support. However the stance and step cycle deficits were transient, the performance of 6-OHDA lesioned rats were indistinguishable from control rats by the last test session with regard to these parameters. Finally, we found that administration of a single dose of levodopa (L-DOPA) to the 6-OHDA lesioned rats could counteract all but one observed deficits. Based on these findings we conclude that the gait pattern of intact rats is highly reproducible, 6-OHDA lesioned rats display impairments in gait, and L-DOPA can counteract most deficits seen in this model of experimental PD.

High-frequency stimulation of the subthalamic nucleus inhibits the firing of juxtacellular labelled 5-HT-containing neurones

High-frequency stimulation (HFS) of the subthalamic nucleus (STN) is an established neurosurgical therapy for movement disability in advanced Parkinson's disease (PD), but some patients experience psychiatric side-effects like depression. In a previous electrophysiological study, we observed that HFS of the STN inhibited a population of neurones in the rat dorsal raphe nucleus (DRN), with firing properties characteristic of 5-HT neurones. The present study extended these findings to a second population of neurones, and combined extracellular recording with juxtacellular-labelling to investigate the chemical identity of the neurones affected by HFS. Bilateral HFS (130 Hz, 100-200 μA, 5 min) of the STN inhibited (26.0±2.9%) the firing of 37/74 DRN neurones displaying a slow, regular firing pattern. Slower firing neurones were more strongly inhibited than those firing faster. Importantly, 10 inhibited DRN neurones were juxtacellular-labelled with neurobiotin, and all neurones contained 5-HT as shown by post-mortem 5-HT immunocytochemistry. A minority of slow firing DRN neurones (18/74) were activated by STN HFS (37.9±8.3%) which was not observed previously. Of these neurones, three were juxtacellular-labelled and one was 5-HT immunopositive. Also a small number of DRN neurones (19/74) did not respond to HFS, four of which were juxtacellular-labelled and all contained 5-HT. These data show that individual chemically-identified 5-HT-containing neurones in the DRN were modulated by STN HFS, and that the majority were inhibited but some were activated and some failed to respond. These data extend previous findings of modulation of the 5-HT system by STN HFS but suggest a destabilisation of the 5-HT system rather than simple inhibition as indicated previously. Although the mechanism is not yet known, such changes may contribute to the psychiatric side-effects of STN stimulation in some PD patients.

Quantitative evaluation of the effects of subthalamic stimulation on gait in Parkinson's disease patients using principal component analysis

BACKGROUND

Principal component analysis (PCA) was applied to the ground reaction force (GRF) for evaluating the deep brain stimulation of the subthalamic nucleus (DBS-STN) effects in Parkinson's disease (PD) subjects with and without medication.

METHODS

Ten subjects who underwent DBS-STN were evaluated under the following four conditions: without treatment (mof-sof), with stimulation (mof-son), with medication (mon-sof), and with both treatments (mon-son). A control group of 30 subjects was also evaluated. PCA was applied separately on each GRF component. Broken stick criterion selected eight principal components (PC) from vertical GRF and one from each horizontal GRF. A standard distance was calculated using these 10 PCs and the gait speed to measure how far the PD group's gait was from the normal pattern.

RESULTS

The standard distance allowed classifying normal and PD subjects in the mof-sof condition with 100% accuracy, sensitivity, and specificity. The same distance was calculated for mon-sof, mof-son, and mon-son conditions. The smallest mean standard distance was found in the mon-son condition, which was significantly different from mof-sof (Friedman test with Dunn post-hoc, p < .05).

CONCLUSION

PCA allowed the quantitative evaluation of treatment effects, indicating that DBS-STN improves the GRF pattern in PD subjects, primarily in the medication on state.