Enzalutamide induces cytotoxicity in desmoplastic small round cell tumor independent of the androgen receptor

Desmoplastic Small Round Cell Tumor (DSRCT) is a rare, pediatric cancer caused by the EWSR1::WT1 fusion protein. DSRCT predominantly occurs in males, which comprise 80-90% of the patient population. While the reason for this male predominance remains unknown, one hypothesis is that the androgen receptor (AR) plays a critical role in DSRCT and elevated testosterone levels in males help drive tumor growth. Here, we demonstrate that AR is highly expressed in DSRCT relative to other fusion-driven sarcomas and that the AR antagonists enzalutamide and flutamide reduce DSRCT growth. However, despite these findings, which suggest an important role for AR in DSRCT, we show that DSRCT cell lines form xenografts in female mice at the same rate as male mice and AR depletion does not significantly alter DSRCT growth in vitro. Further, we find that AR antagonists reduce DSRCT growth in cells depleted of AR, establishing an AR-independent mechanism of action. These findings suggest that AR dependence is not the reason for male predominance in DSRCT and that AR-targeted therapies may provide therapeutic benefit primarily through an AR-independent mechanism that requires further elucidation.

Calibration improvements expand filterscope diagnostic use

The filterscope diagnostic on DIII-D utilizes photomultiplier tubes to measure visible light emission from the plasma. The system has undergone a substantial upgrade since previous attempts to cross-calibrate the filterscope with other spectroscopic diagnostics were unsuccessful. The optics now utilize a dichroic mirror to initially split the light at nearly 99% transmission or reflectance for light below or above 550 nm. This allows the system to measure Dα emission without degrading visible light emission from the plasma for wavelengths below 550 nm (to measure Dβ, Dγ, W-I, C-III, etc.). Additional optimization of the optical components and calibration techniques reduce the error in the signal up to 10% in some channels compared to previous methods. Cross-calibration measurements with two other high resolution spectroscopic diagnostics now show excellent agreement for the first time. This expands the capabilities of the filterscope system allowing measurement of divertor detachment, emission profiles, edge-localized mode behavior, and plasma-wall interactions. It also enables direct comparisons against calculations from boundary plasma simulations. These were not possible before.

Enzalutamide Induces Cytotoxicity in Desmoplastic Small Round Cell Tumor Independent of the Androgen Receptor

Desmoplastic Small Round Cell Tumor (DSRCT) is a rare, pediatric cancer caused by the EWSR1::WT1 fusion protein. DSRCT predominantly occurs in males, which comprise 80-90% of the patient population. While the reason for this male predominance remains unknown, one hypothesis is that the androgen receptor (AR) plays a critical role in DSRCT and elevated testosterone levels in males help drive tumor growth. Here, we demonstrate that AR is highly expressed in DSRCT relative to other fusion-driven sarcomas and that the AR antagonists enzalutamide and flutamide reduce DSRCT growth. However, despite these findings, which suggest an important role for AR in DSRCT, we show that DSRCT cell lines form xenografts in female mice at the same rate as male mice and AR depletion does not significantly alter DSRCT growth in vitro. Further, we find that AR antagonists reduce DSRCT growth in cells depleted of AR, establishing an AR-independent mechanism of action. These findings suggest that AR dependence is not the reason for male predominance in DSRCT and that AR-targeted therapies may provide therapeutic benefit primarily through an AR-independent mechanism that requires further elucidation.

Mapping the Single-cell Differentiation Landscape of Osteosarcoma

The genetic and intratumoral heterogeneity observed in human osteosarcomas (OS) poses challenges for drug development and the study of cell fate, plasticity, and differentiation, processes linked to tumor grade, cell metastasis, and survival. To pinpoint errors in OS differentiation, we transcriptionally profiled 31,527 cells from a tissue-engineered model that directs MSCs toward adipogenic and osteoblastic fates. Incorporating pre-existing chondrocyte data, we applied trajectory analysis and non-negative matrix factorization (NMF) to generate the first human mesenchymal differentiation atlas. This 'roadmap' served as a reference to delineate the cellular composition of morphologically complex OS tumors and quantify each cell's lineage commitment. Projecting these signatures onto a bulk RNA-seq OS dataset unveiled a correlation between a stem-like transcriptomic phenotype and poorer survival outcomes. Our study takes the critical first step in accurately quantifying OS differentiation and lineage, a prerequisite to better understanding global differentiation bottlenecks that might someday be targeted therapeutically.

Dissociation protocols used for sarcoma tissues bias the transcriptome observed in single-cell and single-nucleus RNA sequencing

BACKGROUND

Single-cell RNA-seq has emerged as an innovative technology used to study complex tissues and characterize cell types, states, and lineages at a single-cell level. Classification of bulk tumors by their individual cellular constituents has also created new opportunities to generate single-cell atlases for many organs, cancers, and developmental models. Despite the tremendous promise of this technology, recent evidence studying epithelial tissues and diverse carcinomas suggests the methods used for tissue processing, cell disaggregation, and preservation can significantly bias gene expression and alter the observed cell types. To determine whether sarcomas - tumors of mesenchymal origin - are subject to the same technical artifacts, we profiled patient-derived tumor explants (PDXs) propagated from three aggressive subtypes: osteosarcoma (OS), Ewing sarcoma (ES), desmoplastic small round cell tumor (DSRCT). Given the rarity of these sarcoma subtypes, we explored whether single-nuclei RNA-seq from more widely available archival frozen specimens could accurately be identified by gene expression signatures linked to tissue phenotype or pathognomonic fusion proteins.

RESULTS

We systematically assessed dissociation methods across different sarcoma subtypes. We compared gene expression from single-cell and single-nucleus RNA-sequencing of 125,831 whole-cells and nuclei from ES, DSRCT, and OS PDXs. We detected warm dissociation artifacts in single-cell samples and gene length bias in single-nucleus samples. Classic sarcoma gene signatures were observed regardless of the dissociation method. In addition, we showed that dissociation method biases could be computationally corrected.

CONCLUSIONS

We highlighted transcriptional biases, including warm dissociation and gene-length biases, introduced by the dissociation method for various sarcoma subtypes. This work is the first to characterize how the dissociation methods used for sc/snRNA-seq may affect the interpretation of the molecular features in sarcoma PDXs.

The androgen receptor is a therapeutic target in desmoplastic small round cell sarcoma

Desmoplastic small round cell tumor (DSRCT) is an aggressive, usually incurable sarcoma subtype that predominantly occurs in post-pubertal young males. Recent evidence suggests that the androgen receptor (AR) can promote tumor progression in DSRCTs. However, the mechanism of AR-induced oncogenic stimulation remains undetermined. Herein, we demonstrate that enzalutamide and AR-directed antisense oligonucleotides (AR-ASO) block 5α-dihydrotestosterone (DHT)-induced DSRCT cell proliferation and reduce xenograft tumor burden. Gene expression analysis and chromatin immunoprecipitation sequencing (ChIP-seq) were performed to elucidate how AR signaling regulates cellular epigenetic programs. Remarkably, ChIP-seq revealed novel DSRCT-specific AR DNA binding sites adjacent to key oncogenic regulators, including WT1 (the C-terminal partner of the pathognomonic fusion protein) and FOXF1. Additionally, AR occupied enhancer sites that regulate the Wnt pathway, neural differentiation, and embryonic organ development, implicating AR in dysfunctional cell lineage commitment. Our findings have direct clinical implications given the widespread availability of FDA-approved androgen-targeted agents used for prostate cancer.

Androgen receptor can promote tumour progression in desmoplastic small round cell tumour (DSRCT), an aggressive paediatric malignancy that predominantly affects young males. Here, the authors show that DSRCT is an AR-driven malignancy and sensitive to androgen deprivation therapy

Ion temperature and rotation fluctuation measurements with ultra-fast charge exchange recombination spectroscopy (UF-CHERS) in the DIII-D tokamak

An upgraded detector and several optimizations have significantly improved the Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic sensitivity to ion temperature and parallel velocity fluctuations at turbulence relevant spatio-temporal scales. Normalized broadband ion temperature and parallel velocity fluctuations down to x̃x∼1% (x = T_i, v_∥) and up to ∼450 kHz have been measured in a variety of plasmas. The multi-field nature of the CHERS technique also allows measurements of the cross-phase angles of the fluctuating fields. UF-CHERS is optimized to observe emissions from the electron exchange reaction between intrinsic C⁶⁺ and hydrogenic neutral beam injected particles near 529 nm. UF-CHERS consists of two chords separated by ∼1 cm radially, less than the turbulence correlation length in DIII-D plasmas, which enables correlated measurements to suppress incoherent electronic and photon noise. The optical components of the spectrometer include a volume-phase-holographic grating with >90% transmission between 528 and 530 nm and f/2 200-mm lenses, selected to maximize the optical efficiency and photon flux. Diffracted light from each chord is collected in eight spectral bins, each with a bandwidth of ∼0.25 nm, and detected and amplified by chilled avalanche photodiodes and custom high-gain, wide bandwidth low-noise preamplifiers to achieve the optimal signal-to-noise ratio. The resulting signals are digitized at 1 MHz, 10³-10⁴× faster than the conventional CHERS diagnostics. Spatial coverage is achieved by repositioning a motorized fiber tray between plasmas. UF-CHERS measurements will advance the understanding of turbulent ion transport and contribute to the validation of transport models and simulations.

A Human Organotypic Microfluidic Tumor Model Permits Investigation of the Interplay between Patient-Derived Fibroblasts and Breast Cancer Cells

Tumor-stroma interactions significantly influence cancer cell metastasis and disease progression. These interactions are partly comprised of the cross-talk between tumor and stromal fibroblasts, but the key molecular mechanisms within the cross-talk that govern cancer invasion are still unclear. Here, we adapted our previously developed microfluidic device as a 3D in vitro organotypic model to mechanistically study tumor-stroma interactions by mimicking the spatial organization of the tumor microenvironment on a chip. We cocultured breast cancer and patient-derived fibroblast cells in 3D tumor and stroma regions, respectively, and combined functional assessments, including cancer cell migration, with transcriptome profiling to unveil the molecular influence of tumor-stroma cross-talk on invasion. This led to the observation that cancer-associated fibroblasts (CAF) enhanced invasion in 3D by inducing expression of a novel gene of interest, glycoprotein nonmetastatic B (GPNMB), in breast cancer cells, resulting in increased migration speed. Importantly, knockdown of GPNMB blunted the influence of CAF on enhanced cancer invasion. Overall, these results demonstrate the ability of our model to recapitulate patient-specific tumor microenvironments to investigate the cellular and molecular consequences of tumor-stroma interactions. SIGNIFICANCE: An organotypic model of tumor-stroma interactions on a microfluidic chip reveals that CAFs promote invasion by enhancing expression of GPNMB in breast cancer cells.

Optimization and application of cooled avalanche photodiodes for spectroscopic fluctuation measurements with ultra-fast charge exchange recombination spectroscopy

The Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic is a highly specialized spectroscopic instrument with 2 spatial channels consisting of 8 spectral channels each and a resolution of ∼0.25 nm deployed at DIII-D to measure turbulent ion temperature fluctuations. Charge exchange emissions are obtained between 528 and 530 nm with 1 μs time resolution to study plasma instabilities. A primary challenge of extracting fluctuation measurements from raw UF-CHERS signals is photon and electronic noise. In order to reduce dark current, the Avalanche Photodiode (APD) detectors are thermo-electrically cooled. State-of-the-art components are used for the signal amplifiers and conditioners to minimize electronic noise. Due to the low incident photon power (≤1 nW), APDs with a gain of up to 300 are used to optimize the signal to noise ratio. Maximizing the APDs' gain while minimizing the excess noise factor (ENF) is essential since the total noise of the diagnostic sets a floor for the minimum level of detectable broadband fluctuations. The APDs' gain should be high enough that photon noise dominates electronic noise, but not excessive so that the ENF overwhelms plasma fluctuations. A new generation of cooled APDs and optimized preamplifiers exhibits significantly enhanced signal-to-noise compared to a previous generation. Experiments at DIII-D have allowed for characterization and optimization of the ENF vs. gain. A gain of ∼100 at 1700 V is found to be near optimal for most plasma conditions. Ion temperature and toroidal velocity fluctuations due to the edge harmonic oscillation in quiescent H-mode plasmas are presented to demonstrate UF-CHERS' capabilities.

High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of Te(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83-130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1-3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6-0.8 cm) resolution Te measurements. The high resolution subsystem branches off from the regular channels' IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2-4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters' center frequencies (250 MHz). This configuration allows for full coverage of the 83-130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a "zoomed-in" analysis of a ∼2-4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial Te measurements, which demonstrate that the desired resolution is achieved, are presented.

Intracisternal administration of glibenclamide or 5-hydroxydecanoate does not reverse the neuroprotective effect of ketogenic diet against ischemic brain injury-induced neurodegeneration

PRIMARY OBJECTIVE

To investigate the role of ATP-sensitive potassium (K(ATP)) channels in the neuroprotective effects of a ketogenic diet against cardiac arrest-induced cerebral ischemic brain injury-induced neurodegeneration.

RESEARCH DESIGN

Male Sprague Dawley rats were randomly divided into three groups and were fed with a ketogenic diet for 25 days before being subjected to a cardiac arrest-induced cerebral ischemia for 8 minutes 30 seconds. Four hours before cardiac arrest-induced cerebral ischemia, one group was intracisternally injected with glibenclamide, a plasma membrane K(ATP) channel blocker. The second group was injected with 5-hydroxydecanoate, a mitochondrial K(ATP) channel blocker. The third group was without the pre-treatment with K(ATP) channel antagonist. Nine days after the cardiac arrest, rats were sacrificed. Fluoro-jade (FJ) staining was used to evaluate cerebral ischemic neurodegeneration in the rat brain sections.

MAIN OUTCOMES AND RESULTS

The number of FJ-positive degenerating neurons in the CA1 area of the hippocampus, the cerebellum and the thalamic reticular nucleus of the ketogenic diet-fed rats with or without glibenclamide or 5-hydroxydecanoate pre-treatment before cardiac arrest-induced cerebral ischemia is zero.

CONCLUSIONS

The results suggest that K(ATP) channels do not play a significant role in the neuroprotective effects of the ketogenic diet against cardiac arrest-induced cerebral ischemic injury-induced neurodegeneration.

Novel THAP1 sequence variants in primary dystonia

BACKGROUND

THAP1 encodes a transcription factor (THAP1) that harbors an atypical zinc finger domain and regulates cell proliferation. An exon 2 insertion/deletion frameshift mutation in THAP1 is responsible for DYT6 dystonia in Amish-Mennonites. Subsequent screening efforts in familial, mainly early-onset, primary dystonia identified additional THAP1 sequence variants in non-Amish subjects.

OBJECTIVE

To examine a large cohort of subjects with mainly adult-onset primary dystonia for sequence variants in THAP1.

METHODS

With high-resolution melting, all 3 THAP1 exons were screened for sequence variants in 1,114 subjects with mainly adult-onset primary dystonia, 96 with unclassified dystonia, and 600 controls (400 neurologically normal and 200 with Parkinson disease). In addition, all 3 THAP1 exons were sequenced in 200 subjects with dystonia and 200 neurologically normal controls.

RESULTS

Nine unique melting curves were found in 19 subjects from 16 families with primary dystonia and 1 control. Age at dystonia onset ranged from 8 to 69 years (mean 48 years). Sequencing identified 6 novel missense mutations in conserved regions of THAP1 (G9C [cervical, masticatory, arm], D17G [cervical], F132S [laryngeal], I149T [cervical and generalized], A166T [laryngeal], and Q187K [cervical]). One subject with blepharospasm and another with laryngeal dystonia harbored a c.-42C>T variant. A c.57C>T silent variant was found in 1 subject with segmental craniocervical dystonia. An intron 1 variant (c.71+9C>A) was present in 7 subjects with dystonia (7/1,210) but only 1 control (1/600).

CONCLUSIONS

A heterogeneous collection of THAP1 sequence variants is associated with varied anatomical distributions and onset ages of both familial and sporadic primary dystonia.

Hemifacial spasm producing tremor-like movements of the head

Tremor is defined as involuntary rhythmic oscillation and is produced by muscle contractions. Hemifacial spasm is rapid involuntary muscle contractions on one side of the face in the distribution of the VIIth nerve. We present a severe case of hemifacial spasm that produces a head-nodding tremor-like movements.

Evidence for effectiveness of botulinum toxin for hyperhidrosis

Hyperhidrosis refers to excessive and uncontrollable sweating beyond that is required to return body temperature to normal. Although a broad spectrum of treatment modalities are available including topical and systemic therapies, iontophoresis, and surgical interventions, their efficacy are usually short-term or are associated with unacceptable side effects. Recently, chemodenervation using botulinum toxin has emerged as a safe and effective treatment for both primary palmar and axillary hyperhidrosis in several clinical trials. In this article, we utilized the scale developed by the Therapeutics and Technology Assessment (TTA) subcommittee of the American Academy of Neurology evaluating current evidence supporting the use of botulinum toxin for the treatment of primary focal hyperhidrosis. As a result, there is a strong evidence to support the efficacy of botulinum toxin type A in axillary (Level A evidence) and palmar (Level B evidence) hyperhidrosis.

Brivaracetam is superior to levetiracetam in a rat model of post-hypoxic myoclonus

In the present study, we evaluated the anti-seizure and anti-myoclonic activity of levetiracetam and brivaracetam in an established rat model of cardiac arrest-induced post-hypoxic myoclonus. We found that brivaracetam (0.3 mg/kg, the minimal effective dose) was more potent than levetiracetam (3 mg/kg, the minimal effective dose) against post-hypoxic seizures. The anti-seizure activity of both compounds occurred 30 min following intraperitoneal (i.p.) administration and was maintained over the entire 150 min post-dose observation period. Both brivaracetam and levetiracetam significantly reduced auditory stimulated post-hypoxic myoclonus from a dose 0.3 mg/kg. At that dose, the anti-myoclonic activity of brivaracetam was already maximal whereas it continued to increase in a dose-relation manner with levetiracetam, suggesting that brivaracetam is a more potent agent. The onset and the duration of anti-myoclonic activity of both compounds were similar. These findings demonstrate that brivaracetam possesses more potent anti-seizure and anti-myoclonic activity than levetiracetam in an established rat model of cardiac arrest-induced post-hypoxic myoclonus.

Evidence for the effectiveness of botulinum toxin for spasmodic dysphonia from high-quality research designs

The practice of evidence-based medicine promotes use of the knowledge ascertained from high quality research designs. The objective of this review was to determine what evidence has been provided from high quality research designs (e.g., randomized control trials or high quality prospective, matched group cohort studies), through December of 2006, relative to the effectiveness of botulinum toxin for treating spasmodic dysphonia. Results of the review indicated that no new high quality (Class I or Class II) studies have been published since 2001. One Class I study has been published since 1973, which found significant treatment effects for acoustic and perceptual variables of vocal function. Four Class II studies have been published during this same time frame, all finding significant treatment effects, though the nature of studied factors was variable between investigations. Based on the quality of evidence scale used, botulinum toxin can be considered an effective treatment for adductor spasmodic dysphonia.

Ropinirole 24-hour prolonged release: randomized, controlled study in advanced Parkinson disease

OBJECTIVE

To evaluate the efficacy of ropinirole 24-hour prolonged release (ropinirole 24-hour) as an adjunct to levodopa in patients with Parkinson disease (PD) and motor fluctuations.

METHODS

In a double-blind, placebo-controlled, 24-week study, 393 subjects with PD were randomized to ropinirole 24-hour (n = 202) or placebo (n = 191). The primary outcome measure was reduction in hours of daily "off" time.

RESULTS

At week 24, the mean dose of ropinirole 24-hour was 18.8 mg/day with a mean reduction in daily levodopa of 278 mg. There was a mean reduction in daily "off" time of 2.1 hours in the ropinirole 24-hour group and 0.3 hours with placebo. Secondary outcome measures including change in hours and percent of daily "on" time and "on" time without troublesome dyskinesia, Unified PD Rating Scale motor and activities of daily living subscales, Beck Depression Inventory-II, PDQ-39 subscales of mobility, activities of daily living, emotional well-being, stigma and communication, and PD Sleep Scale were significantly improved at week 24 with ropinirole 24-hour. The most common adverse events (AE) with ropinirole 24-hour were dyskinesia, nausea, dizziness, somnolence, hallucinations, and orthostatic hypotension and AEs led to study withdrawal in 5% of both the active and placebo groups.

CONCLUSION

Ropinirole 24-hour was effective and well tolerated as adjunct therapy in patients with Parkinson disease (PD) not optimally controlled with levodopa. Ropinirole 24-hour demonstrated an improvement in both motor and non-motor PD symptoms, while permitting a reduction in adjunctive levodopa dose.

Botulinum toxin in blepharospasm and oromandibular dystonia: comparing different botulinum toxin preparations

Amongst all regions of the body, the craniocervical region is the one most frequently affected by dystonia. Whilst blepharospasm--involuntary bilateral eye closure--is produced by spasmodic contractions of the orbicularis oculi muscles, oromandibular dystonia may cause jaw closure with trismus and bruxism, or involuntary jaw opening or deviation, interfering with speaking and chewing. Both forms of dystonia can be effectively treated with botulinum toxin injection. This article summarizes injection techniques in both forms of dystonia and compares doses, potency and efficacy of different commercially available toxins, including Botox, Dysport, Xeomin and Myobloc/NeuroBloc.

Botulinum toxin therapy of hemifacial spasm: comparing different therapeutic preparations

Hemifacial spasm (HFS) is characterized by involuntary irregular clonic or tonic movements of the muscles innervated by cranial nerve VII on one side of the face, and is most often a result of vascular compression of the facial nerve at the root exit zone (Muscle and Nerve 1998;21:1740). Disability associated with this disorder ranges from social embarrassment to interference with vision resulting from involuntary eye closure. Treatment of HFS most often involves botulinum toxin injections, but may also include medications and surgery. We describe treatment with the three types of botulinum toxin currently commercially available--Botox, Dysport and Myobloc/NeuroBloc.

Botulinum toxin therapy of hemifacial spasm: comparing different therapeutic preparations

Hemifacial spasm (HFS) is characterized by involuntary irregular clonic or tonic movements of the muscles innervated by cranial nerve VII on one side of the face, and is most often a result of vascular compression of the facial nerve at the root exit zone (Muscle and Nerve 1998;21:1740). Disability associated with this disorder ranges from social embarrassment to interference with vision resulting from involuntary eye closure. Treatment of HFS most often involves botulinum toxin injections, but may also include medications and surgery. We describe treatment with the three types of botulinum toxin currently commercially available--Botox, Dysport and Myobloc/NeuroBloc.

Botulinum toxin therapy of laryngeal muscle hyperactivity syndromes: comparing different botulinum toxin preparations

Spasmodic dysphonia (SD) is a focal dystonia characterized by a strained, strangled voice. Botulinum toxin is a symptomatic treatment for SD and has become the mainstay of therapy over the last two decades. In this manuscript, we briefly review different laryngeal muscle hyperactivity syndromes, their injection techniques and toxins currently available. Adductor SD is the most common indication for botulinum toxin treatment in the larynx. All studies report similar results with regard to improvement, patient satisfaction and side effects. We describe different injection techniques to treat this disorder such as the percutaneous, transoral, transnasal, point-touch techniques. In abductor SD, a subtype of SD, the treatment is aimed at the posterior cricoarytenoid muscle. Other applications of botulinum toxin in the larynx include spasmodic laryngeal dyspnea and voice tremors. We also review injection techniques, the different toxin types used, and toxin doses.

Botulinum toxin in blepharospasm and oromandibular dystonia: comparing different botulinum toxin preparations

Amongst all regions of the body, the craniocervical region is the one most frequently affected by dystonia. Whilst blepharospasm--involuntary bilateral eye closure--is produced by spasmodic contractions of the orbicularis oculi muscles, oromandibular dystonia may cause jaw closure with trismus and bruxism, or involuntary jaw opening or deviation, interfering with speaking and chewing. Both forms of dystonia can be effectively treated with botulinum toxin injection. This article summarizes injection techniques in both forms of dystonia and compares doses, potency and efficacy of different commercially available toxins, including Botox, Dysport, Xeomin and Myobloc/NeuroBloc.

Botulinum toxin in blepharospasm and oromandibular dystonia: comparing different botulinum toxin preparations

Amongst all regions of the body, the craniocervical region is the one most frequently affected by dystonia. Whilst blepharospasm--involuntary bilateral eye closure--is produced by spasmodic contractions of the orbicularis oculi muscles, oromandibular dystonia may cause jaw closure with trismus and bruxism, or involuntary jaw opening or deviation, interfering with speaking and chewing. Both forms of dystonia can be effectively treated with botulinum toxin injection. This article summarizes injection techniques in both forms of dystonia and compares doses, potency and efficacy of different commercially available toxins, including Botox, Dysport, Xeomin and Myobloc/NeuroBloc.

Chorea and related disorders

Chorea refers to irregular, flowing, non-stereotyped, random, involuntary movements that often possess a writhing quality referred to as choreoathetosis. When mild, chorea can be difficult to differentiate from restlessness. When chorea is proximal and of large amplitude, it is called ballism. Chorea is usually worsened by anxiety and stress and subsides during sleep. Most patients attempt to disguise chorea by incorporating it into a purposeful activity. Whereas ballism is most often encountered as hemiballism due to contralateral structural lesions of the subthalamic nucleus and/or its afferent or efferent projections, chorea may be the expression of a wide range of disorders, including metabolic, infectious, inflammatory, vascular, and neurodegenerative, as well as drug induced syndromes. In clinical practice, Sydenham's chorea is the most common form of childhood chorea, whereas Huntington's disease and drug induced chorea account for the majority of adult onset cases. The aim of this review is to provide an up to date discussion of this disorder, as well as a practical approach to its management.

The natural history of embouchure dystonia

Focal task-specific dystonias are unusual disorders of motor control, often affecting individuals who perform complex repetitive movements. Musicians are especially prone to develop these disorders because of their training regimens and intense practice schedules. Task-specific dystonia occurring in keyboard or string instrumentalists usually affects the hand. In contrast, there have been few descriptions of musicians with task-specific dystonia affecting the muscles of the face and jaw. We report detailed clinical observations of 26 professional brass and woodwind players afflicted with focal task-specific dystonia of the embouchure (the pattern of lip, jaw, and tongue muscles used to control the flow of air into a mouthpiece). This is the largest and most comprehensively studied series of such patients. Patients developed embouchure dystonia in the fourth decade, and initial symptoms were usually limited to one range of notes or style of playing. Once present, dystonia progressed without remission and responded poorly to oral medications and botulinum toxin injection. Patients with embouchure dystonia could be separated by the pattern of their abnormal movements into several groups, including embouchure tremor, involuntary lip movements, and jaw closure. Dystonia not infrequently spread to other oral tasks, often producing significant disability. Effective treatments are needed for this challenging and unusual disorder.

Involvement of GABA(A) receptors in myoclonus

Alterations in multiple neurochemical systems have been reported in animal and human studies of posthypoxic myoclonus. It is impossible, however, to establish causative relationships between the observed changes and the myoclonic movements from these studies. Therefore, to establish causative links between neurochemical changes and myoclonus, ligands that target neurotransmitter systems that are altered in posthypoxic myoclonus were microinjected into the lateral ventricles of normal rats to identify the changes that can produce myoclonus. Of the ligands that were tested, only the GABA(A) antagonists produced myoclonus after intracerebroventricular administration, suggesting the importance of disinhibition of GABAergic systems in myoclonus. To further examine the role of GABA in myoclonus, GABAergic antagonists were microinjected into the nucleus reticularis of the thalamus (NRT), an area of the brain in which extensive pathologic changes are seen in posthypoxic animals. GABA(A), but not GABA(B), antagonists produced myoclonus after microinjection into the NRT. Earlier investigators have further reported the ability of GABA(A) antagonists to produce myoclonus after microinjection into the caudate. The data therefore suggest that disruption of activity at GABA(A) receptors at any one of a number of levels in the neural axis can produce myoclonus.

Animal model of posthypoxic myoclonus: II. Neurochemical, pathologic, and pharmacologic characterization

The sudden, brief, shock-like, involuntary movements caused by active muscular contractions or inhibitions characterize myoclonus. It is manifested in a wide variety of pathologic conditions affecting the brain, spinal cord, or peripheral nerves, and is thought to be related to neuronal hyperexcitability. The pathology, physiology, and pharmacology of myoclonus are not well understood as a result of the rarity of the disorder in people and the lack of a suitable animal model. Posthypoxic myoclonus is a major myoclonus syndrome which occurs as a result of severe cerebral ischemia/hypoxia. There has been tremendous interest in the development of a suitable animal model that reflects the etiology and clinical pathology of posthypoxic myoclonus. Recently, we have developed a new animal model of posthypoxic myoclonus in which rats were subjected to a mechanically induced cardiac arrest procedure. Herein, we describe the neurochemical, pharmacologic, and pathologic characteristics of this animal model of posthypoxic myoclonus.

Animal models of myoclonus: an overview

Attempts to characterize the mechanism(s) associated with myoclonus have led to the development of several naturally occurring and pharmacologically based animal models of myoclonus. Congenital disorders in animals that result in myoclonic seizures have been found in subpopulations of baboons that exhibit photoresponsive myoclonus and in herds of Hereford cattle that possess a fatal, autosomal-inherited imbalance in spinal glycine neurotransmission. Pharmacologically based models of myoclonus use a variety of approaches to product myoclonic seizures in test animals.

Effect of riluzole on the neurological and neuropathological changes in an animal model of cardiac arrest-induced movement disorder

Posthypoxic myoclonus and seizures precipitate as secondary neurological consequences in ischemic/hypoxic insults of the central nervous system. Neuronal hyperexcitation may be due to excessive activation of glutamatergic neurotransmission, an effect that has been shown to follow ischemic/hypoxic events. Therefore, riluzole, an anticonvulsant that inhibits the release of glutamate by stabilizing the inactivated state of activated voltage-sensitive sodium channels, was tested for its antimyoclonic and neuroprotective properties in the cardiac arrest-induced animal model of posthypoxic myoclonus. Riluzole (4-12 mg/kg i.p.) dose-dependently attenuated the audiogenic seizures and action myoclonus seen in this animal model. Histological examination using Nissl staining and the novel Fluoro-Jade histochemistry in cardiac-arrested animals showed an extensive neuronal degeneration in the hippocampus and cerebellum. Riluzole treatment almost completely prevented the neuronal degeneration in these brain areas. The neuroprotective effect was more pronounced in hippocampal pyramidal neurons and cerebellar Purkinje cells. These effects were seen at therapeutically relevant doses of riluzole, and the animals tolerated the treatment well. These findings indicate that the pathogenesis of posthypoxic myoclonus and seizure may involve excessive activation of glutamate neurotransmission, and that riluzole may serve as an effective pharmacological agent with neuroprotective potential for the treatment of neurological conditions associated with cardiac arrest in humans.

BotB (botulinum toxin type B): evaluation of safety and tolerability in botulinum toxin type A-resistant cervical dystonia patients (preliminary study)

Botulinum toxin (BTX) injection is considered the treatment of choice for patients with cervical dystonia (torticollis). We conducted a pilot, open-label, dose-escalation study with BTX type B in 12 patients who no longer responded clinically to injections with BTX type A. At the doses tested, BTX type B was safe and well tolerated without evidence of dose-limiting toxicity in this patient population. Mild-to-moderate adverse events generally resolved quickly and included asthenia, pain, nausea, dysphagia, hypertonia, and tremor. No serious adverse events or antibodies to type-B treatment were reported. Low-dosing-session (100-899 units) and high-dosing-session (900-1,500 units) groups were defined based on units administered per dosing session. Toronto Western Spasmodic Torticollis Rating Scale-Severity Scale (TWSTRS-Severity), Patient Analogue Pain Scale, and Physician and Patient Global Assessment Scales were measured during this study. The TWSTRS-Severity mean maximum percent improvement from baseline demonstrated a 9.9% versus 28.8% difference between the low-dose and high-dose groups, respectively. EFfectiveness was noted for the high-dose group on the Patient Analogue Pain Scale but not on the Global Assessment Scales.

Neuroprotective effects of the strychnine-insensitive glycine site NMDA antagonist (R)-HA-966 in an experimental model of Parkinson's disease

The neuroprotective effects of (R)-HA-966 and (S)-HA-966 (3-amino-1-hydroxy-2-pyrrolidinone) were examined in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced animal model of Parkinson's disease. Systemic pretreatment of C57 black mice with the strychnine-insensitive glycine site antagonist, (R)-HA-966 (3-30 mg/kg, i.p.), dose-dependently attenuated MPTP-induced depletion of striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC). Pretreatment with (R)-HA-966 also significantly protected the degeneration of tyrosine hydroxylase-positive neurons in the substantia nigra of mice treated with MPTP and alleviated the acute behavioral changes caused by the neurotoxin. In contrast, the other racemic form, (S)-HA-966, neither prevented the neurochemical depletions nor the neuronal injury caused by MPTP. These results indicate that excitatory mechanisms of neurodegeneration are involved in the pathophysiology of Parkinson's disease, and that strychnine-insensitive glycine site NMDA antagonists may serve as dopaminoprotective agents which intervene in the progressive neurodegeneration in Parkinson's disease.

Dissociation of the motor effects of (+)-pentazocine from binding to sigma 1 sites

Radioligand binding and behavioral studies were conducted to determine whether a relationship existed between the motor effects produced by (+)-pentazocine and its binding to sigma sites. Scatchard analyses revealed decreased [3H](+)-pentazocine binding in middle aged rats (5-6 months old) compared to young adult rats (2-3 months old). However, there was no difference between the extent of circling behavior or dystonia produced by microinjection of (+)-pentazocine into the substantia nigra or red nucleus in the older animals compared to the young adult rats. There was also a significant decrease in [3H](+)-pentazocine binding in rats chronically treated with haloperidol. Again, however, despite the reduction in [3H](+)-pentazocine binding, there was no difference between the extent of dystonia produced by unilateral intrarubral microinjection of (+)-pentazocine into animals chronically treated with haloperidol vs. saline. The postural changes produced by (+)-pentazocine could not be attenuated with coadministration of the putative sigma receptor antagonist BD1047 (N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino) ethylamine), or the opiate receptor antagonist naloxone. However, the (+)-opiate, (+)-nordihydrocodeinone, partially attenuated the postural effects of (+)-pentazocine, despite its very low affinity for sigma 1, sigma 2, or opiate receptors. Taken together with previous studies, the results suggest that [3H](+)-pentazocine is a potent and selective probe for sigma 1 binding sites, but the in vivo effects of (+)-pentazocine cannot be fully attributed to actions through these sites. Some of the in vivo effects of (+)-pentazocine appear to involve other binding sites that are not detected under the conditions normally used in in vitro assays.

Antimyoclonic effect of gabapentin in a posthypoxic animal model of myoclonus

The antimyoclonic property of the novel antiepileptic drug, gabapentin (1-(aminomethyl) cyclohexane acetic acid), was tested in cardiac arrest-and p,p'-DDT(1,1,1-trichloro-2,2-bis (p-chlorophenyl)ethane)-induced animal models of myoclonus. Gabapentin dose-dependently attenuated myoclonus in posthypoxic rats for more than 3 h. The drug was also found to be effective in controlling the early stages of seizures following the anoxic insult. In contrast, the drug was ineffective in controlling either myoclonus or seizures in p,p'-DDT-treated animals. These results suggest that gabapentin can be used used as an effective therapeutic agent in an acute hypoxia/ischemia-induced neurological disorder. The data further indicate that distinct neurological mechanisms may be operating in the expression of myoclonus among posthypoxic and p,p'-DDT-induced animal models.

Effects of GABA uptake inhibitors on posthypoxic myoclonus in rats

Male Sprague-Dawley rats developed posthypoxic myoclonus following 10-min cardiac arrest and resuscitation. Previous results showed that dysfunction of central GABAergic neurotransmission may contribute to the disease. In current studies, effects of GABA uptake inhibitors, guvacine hydrochloride (1,2,5,6-tetrahydro-3-pyridine carboxylic acid hydrochloride) and (+/-)-cis-4-hydroxynipecotic acid ([+/-]-cis-4-hydroxy-3-piperidine carboxylic acid), in the pathophysiology of posthypoxic myoclonus were investigated. Administration of guvacine (1 or 10 mg/kg, IP) or nipecotic acid (0.5 or 5 mg/kg, IP) significantly attenuated myoclonus scores of the animals. Tolerance to antimyoclonus effects of these two compounds did not develop after chronic administration (twice a day for 14 days) of guvacine (10 mg/kg, IP) or nipecotic acid (5 mg/kg, IP). On the other hand, tolerance was noticed with clonazepam (2.5 mg/kg, IP twice a day for 7 days). The results indicate that guvacine or nipecotic acid may be used in combination with (at reduced doses) or as alternatives to clonazepam to treat patients with the disease so as to reduce tolerance phenomenon usually associated with clonazepam.

Astrocyte-derived growth factor (S100 beta) and motor function in rats following cardiac arrest

Following 10-min cardiac arrest and resuscitation, the central serotonergic system and motor function of rats were found to be affected and later on restored. Astrocyte-derived growth factor (S100 beta) is known to promote survival and neurite outgrowth of serotonergic neurons. In the present study, brain levels of S100 beta were investigated with quantitative immunoblot analysis at various time points following cardiac arrest. Significant reductions of S100 beta were found in the cerebral cortex (30%), midbrain (35%), and cerebellum (46%) of rats 3 days postcardiac arrest. In contrast, at 14 and > 45 days, significant increases of S100 beta were detected in the cerebral cortex (57%; 81%), midbrain (70%; 97%), and cerebellum (84%; 157%). The results indicate that reactive astrocytosis and elevated levels of S100 beta may participate in the recovery processes following hypoxic-ischemic insults to the brain.

Chronic treatments with 5-HT1A agonists attenuate posthypoxic myoclonus in rats

Following 10 min cardiac arrest and resuscitation, male Sprague-Dawley rats developed posthypoxic myoclonus. This phenomenon peaked at 14 days and disappeared by 60 days after cardiac arrest. From previous results, the 5-hydroxytryptamine (5-HT) system was implicated in the pathogenesis of the disease. In the present study, we investigated the involvement of 5-HT1A receptors in posthypoxic myoclonus in rats. Single injections of 5-HT1A agonists, buspirone (5 and 10 mg/kg body wt.) or 8-OH-DPAT (1, 2, and 4 mg/kg), had no effect on either the intensity or time course of the disease. In contrast, multiple injections (twice a day for 7 or more days) of buspirone (10 mg/kg) or 8-OH-DPAT (4 mg/kg) significantly attenuated the myoclonus scores of animals (p < 0.05). The results indicate that chronic stimulation of 5-HT1A receptors in the brain may accelerate endogenous compensatory mechanisms and shorten the time course of the disease.

Regulation of tyrosine protein kinase receptor Trk-B and motor function in rats following cardiac arrest

Following 10 min cardiac arrest and resuscitation, male Sprague-Dawley rats developed posthypoxic myoclonus. Sixty days later, the motor function of the animals was restored. In the present study, we investigated brain levels of tyrosine protein kinase receptor Trk-B with quantitative immunoblot analysis at various time points following cardiac arrest. In the frontal cortex, a significant reduction of Trk-B was found in rats 3 days (53%) after cardiac arrest, whereas significant increases were detected in rats 14 (124%) and an average 60 days (98%) after cardiac arrest. In the striatum, significant increases were found in rats 3 (389%), 14 (483%), and 60 days (521%) after resuscitation. In contrast, significant reductions of Trk-B were detected in the cerebellum of rats 3 (46%), 14 (22%), and 60 days (18%) after cardiac arrest. The results indicate that regulation of Trk-B may vary in different brain regions and have important roles in recovery processes following hypoxic-ischemic insults to the brain.

Effects of selective serotonergic ligands on posthypoxic audiogenic myoclonus

Male Sprague-Dawley rats underwent cardiac arrest and resuscitation, subsequently exhibiting posthypoxic myoclonus. The audiogenic posthypoxic myoclonus in these animals could be attenuated with the following drugs: 5-hydroxytryptophan (5-HTP, serotonin [5-HT] precursor), N-(3-trifluoro-methylphenyl)piperazine hydrochloride (TFMPP, 5-HT1B/1C/2 agonist), (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrobromide (DOI, 5-HT2 agonist), and 1-(m-chlorophenyl)-biguanide hydrochloride (m-CPBG, 5-HT3 agonist). In contrast, the following drugs were ineffective: (+/-)-8-hydroxy-dipropylaminotetralin hydrobromide (8-OH-DPAT, 5-HT1A agonist), buspirone hydrochloride (5-HT1A agonist), 7-trifluoromethyl-4(4-methyl-l-piperazinyl)-pyrrolo[1,2- a]quinoxaline maleate (CGS 12066B, 5-HT1B agonist), ketanserin tartrate (5-HT2 antagonist), methysergide maleate (5-HT2 antagonist), fluoxetine (5-HT uptake blocker), and saline (vehicle). The data suggest that enhancement of serotonergic activity, particularly through 5-HT2 and 5-HT3 receptors, have therapeutic potential for the treatment of posthypoxic myoclonus.

Evidence for the involvement of histamine in the antidystonic effects of diphenhydramine

Although diphenhydramine hydrochloride is known to eliminate or reduce the symptoms of dystonia in human patients with acute dystonic reactions and idiopathic torsion dystonia, its mechanism of action is still unclear. In the present study, we show that the antihistamine properties of diphenhydramine may contribute to its beneficial effects. Acute dystonic reactions were produced in rats with unilateral microinjection of haloperidol into the red nucleus as previously described. Similar to the pattern in humans, this effect could be attenuated by coadministration of diphenhydramine. Unilateral microinjection of histamine itself into the rat red nucleus produced dystonic postures (torticollis) in a dose-dependent manner, demonstrating that a histamine dysfunction could contribute to the pathophysiology of dystonia. The torticollis produced by histamine could be significantly attenuated with coadministration of the H1 antagonists diphenhydramine or pyrilamine or the H2 antagonist cimetidine. These effects are thought to be mediated through the red nucleus because significantly more torticollis was observed when histamine was injected into the red nucleus rather than surrounding mid-brain areas, the substantia nigra, or the lateral ventricle. The present data, taken together with studies in humans, suggest the involvement of histamine in some types of dystonia. Furthermore, the red nucleus and related motor pathways may have a more important role in dystonia than previously thought.

Characterization of two novel sigma receptor ligands: antidystonic effects in rats suggest sigma receptor antagonism

The novel sigma receptor ligands, N(-)[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino)ethylamine (BD1047) and 1(-)[2-(3,4-dichlorophenyl)ethyl]-4-methylpiperazine (BD1063), were characterized in rats using binding assays and behavioral studies. In radioligand binding studies, the novel ligands showed marked selectivity for sigma binding sites, generally having a 100-fold or better affinity for sigma sites compared to nine other tested receptors (opiate, phencyclidine, muscarinic, dopamine, alpha 1-, alpha 2-, beta-adrenoceptor, 5-HT1, 5-HT2); the only exception was the affinity of BD1047 for beta-adrenoceptors. Competition assays further revealed that the drugs interacted with both sigma 1 and sigma 2 binding sites. Although both drugs had preferential affinities for sigma 1 sites, BD1047 exhibited a higher affinity for sigma 2 sites than BD1063. In behavioral studies, BD1047 and BD1063 had no effects on their own when unilaterally microinjected into the red nucleus of rats, but both compounds attenuated the dystonia produced by the high affinity sigma ligands, di-o-tolylguanidine (DTG) and haloperidol. BD1047 and BD1063 dose-dependently attenuated the dystonia produced by DTG, suggesting a receptor-mediated mechanism, and the dose curve for DTG was shifted to the right in the presence of the novel ligands. BD1047 and BD1063 appear to act as antagonists at sigma sites and may represent promising new tools for probing other functional effects associated with sigma binding sites.

Alterations of brain levels of phosphoinositidase-C-linked Gq alpha/G11 alpha proteins and motor function in rats after cardiac arrest

BACKGROUND AND PURPOSE

Phosphoinositidase-C-linked Gq alpha and G11 alpha proteins have only recently been characterized. Second messenger systems are known to be affected by hypoxia-ischemia. However, the effects of hypoxia-ischemia on the brain levels of Gq alpha and G11 alpha proteins are not known. Therefore, in the present studies, the effects of hypoxia-ischemia on Gq alpha and G11 alpha proteins in rats were investigated with quantitative immunoblot analysis.

METHODS

Cardiac arrest was induced in male Sprague-Dawley rats by an intracardial injection of KCl. Resuscitation began 10 minutes afterwards. At various time points after resuscitation, animals were killed and the cerebral cortex, striatum, and cerebellum were dissected. Levels of Gq alpha and G11 alpha proteins were investigated by quantitative immunoblot analysis.

RESULTS

At 1, 2, 4, and 6 hours after resuscitation, Gq alpha and G11 alpha protein levels remained unaltered. However, a significant reduction of these proteins was seen in the cerebral cortex and cerebellum of rats 3 and 14 days after cardiac arrest, with partial recovery by an average of 60 days. In contrast, no significant change was detected in the striatum.

CONCLUSIONS

These observations indicate that phosphoinositidase-C-linked signal transduction pathways may be attenuated after hypoxic-ischemic insults to the brain, and that this phenomenon, together with many other factors, may contribute to the expression of motor dysfunction in rats after cardiac arrest.

Diphenhydramine is effective in the treatment of idiopathic dystonia

OBJECTIVE

To assess the effectiveness of diphenhydramine hydrochloride (Benadryl) in the treatment of patients with idiopathic truncal dystonia.

DESIGN

Before-and-after trial.

SETTING

University referral center.

PATIENTS

Five consecutive patients with idiopathic truncal dystonia who were poorly treated with conventional pharmacotherapies. No patients were withdrawn from the trial for adverse side effects.

INTERVENTIONS

Treatments with diphenhydramine hydrochloride (50 mg intravenously or up to 500 mg/kg orally). Follow-up for up to 20 months.

MAIN OUTCOME MEASURE

Dystonia evaluation.

RESULTS

Diphenhydramine therapy was associated with minimal side effects, and it was most effective in treating patients with dystonia who experienced lightning jerks. Treatment with intravenous diphenhydramine may have a predictive value on a future response to oral therapy.

CONCLUSION

Diphenhydramine should be considered a therapeutic option for idiopathic truncal dystonia with lightning jerks.

Association between brain indole levels and severity of posthypoxic myoclonus in rats

We have previously reported the presence of posthypoxic, audiogenic myoclonus in rats after cardiac arrest and the ability of the 5-HT precursor, 5-HTP, to attenuate these muscle jerks. In addition, we have recently shown that 5-HT2 and 5-HT3 agonists can reduce the severity of myoclonus in these animals, suggesting a deficiency in serotonergic neurotransmission. In the present study, the levels of 5-HTP, 5-HT, and 5-HIAA were measured in seven regions of the brain in myoclonic and normal rats to identify the areas of the brain in which a serotonergic dysfunction resides. Similar to previous studies, we observed pronounced posthypoxic, audiogenic myoclonus 3 and 14 days after resuscitation from cardiac arrest, with a resolution of the abnormal movements by 45 days postarrest. HPLC measurements revealed significant changes in indole levels in the following areas of the brain: cortical 5-HIAA, striatal 5-HT, striatal 5-HIAA, hippocampal 5-HT, mesencephalic 5-HIAA, myelencephalic 5-HT, myelencephalic 5-HIAA, cerebellar 5-HTP, and cerebellar 5-HT. The changes in striatal 5-HT, cortical 5-HIAA, and mesencephalic 5-HIAA appear most relevant to the pathophysiology of posthypoxic myoclonus because regression analyses showed significant correlations between the myoclonus scores of the animals and the levels of these indoles. Based on the observed pattern of results, we postulate a dysfunction in serotonergic lateral (cortical) and far lateral (extrapyramidal) ascending pathways in posthypoxic myoclonus.

Strychnine-insensitive glycine site antagonists attenuate a cardiac arrest-induced movement disorder

Male Sprague-Dawley rats underwent experimentally induced cardiac arrest and resuscitation, subsequently exhibiting involuntary jerking movements (myoclonus) with salient features similar to the human form of the disorder. The novel strychnine-insensitive glycine site antagonists ACEA-1011 (5-chloro-7-trifluoromethyl-1,2,3,4-tetrahydroquinoxaline-2,3,-dio ne) and ACEA-1021 (5-nitro-6,7-dichloro-quinoxalinedione) significantly attenuated the myoclonus in cardiac-arrested rats. (+)-HA-966, (+/-)-HA-966 (3-amino-1-hydroxy-2-pyrrolidinone), and felbamate (2-phenyl-1,3-propanediol dicarbamate) were also effective. Although the drugs vary in their selectivity for strychnine-insensitive glycine sites, they all possess antagonist activity at these sites. Vehicle injections (saline, dimethyl sulfoxide, water) were without effect and no obvious side effects were observed with any of the ligands tested in this study. Since hyperexcitability in the central nervous system is thought to underlie myoclonus, the attenuation of excitatory amino acid neurotransmission through antagonism of strychnine-insensitive glycine sites provides a logical mechanism of action for the antimyoclonic effects observed herein.

Animal models of myoclonus

This is a comprehensive review of animal models of myoclonus with particular emphasis on posthypoxic myoclonus and other newer chemically induced models. A stimulus-sensitive myoclonus was developed by experimentally inducing cardiac arrest in rats. The etiology, pharmacology, and neurochemistry associated with this model are consistent with posthypoxic myoclonus in humans. The complex etiology of posthypoxic myoclonus and the effectiveness of diverse pharmacological therapies in this movement disorder suggest that multiple interactive neurological mechanisms are operative. The p,p'-DDT-induced animal model of myoclonus differs from posthypoxic myoclonus in terms of its neurochemical and pathophysiological mechanisms. Also, micro-injection of compounds that modulate specific neurotransmitter systems in select brain regions induces myoclonus in normal animals, suggesting that these chemically induced models may be useful in understanding the intricate neurochemical and neuroanatomical mechanisms associated with myoclonus. The experimental evidence demonstrates that these novel animal models of myoclonus have salient neurological characteristics, reasonable predictability of novel antimyoclonic agents, and pathophysiological similarities to the disorder in humans. Thus, these animal models of myoclonus have the potential to provide us with valuable information about the disorder that is not readily obtainable by other means.

Expression of Bcl-2 and Bax in the frontoparietal cortex of the rat following cardiac arrest

Following 10-min cardiac arrest and resuscitation, male Sprague-Dawley rats developed posthypoxic myoclonus. This phenomenon peaked at 14 days and disappeared by 45 days after cardiac arrest. The mechanisms for the initial dysfunction and later restoration of motor function are not completely known. In the present study, involvement of Bcl-2 and Bax in these phenomena was investigated. In the frontoparietal cortex, both bcl-2 and bax mRNA levels were significantly increased 1, 3, 7, 14, and 28 days postresuscitation. bax mRNA levels continued to be high 45 days postcardiac arrest, whereas bcl-2 mRNA levels were returned to control levels. The apoptotic cells were found in layers IV to VI of the frontoparietal cortex of rats 3 days postcardiac arrest. These results indicate that after cardiac arrest, the initial rise of Bax levels may mediate apoptosis and neurodegeneration in the rat brain. At later time points, increased levels of Bcl-2 may contribute to recovery of motor function in posthypoxic rats.

Involvement of 5-HT2 receptors in posthypoxic stimulus-sensitive myoclonus in rats

We have previously reported that rats exhibited audiogenic myoclonus at 3 days after cardiac arrest. This phenomenon peaked at 14 days, gradually tapered off at older ages, and disappeared in most rats by 60 days following cardiac arrest. Because treatment with the 5-HT2-selective agonist, (+/-)-1-2,5-dimethoxy-4-iodophenyl-2-aminopropane (DOI) significantly attenuated audiogenic myoclonus in these postcardiac-arrest rats, the involvement of 5-HT2 receptors in posthypoxic stimulus-sensitive myoclonus was suggested. In the current study, we, therefore, examined the binding properties of 5-HT2 receptors in the rat bain at various time points following cardiac arrest. The affinity constant of [3H]ketanserin binding to 5-HT2 receptors in cortical membranes of rats did not change. In contrast, Bmax values were found to be reduced at 3 and 14 days after cardiac arrest with some recovery after 60 days. Taken together with previous results, these results indicate that hypoactivity of central 5-HT2 neurotransmission may underlie the development of posthypoxic stimulus-sensitive myoclonus in rats.