Etomidate-induced myoclonus correlates with the dysfunction of astrocytes and glutamate transporters in the neocortex of Sprague-Dawley rats.

OBJECTIVE: Etomidate-induced myoclonus is common in clinical anesthesia. Propofol and lidocaine, as other sedative hypnotic and anticonvulsant drugs, rarely induce myoclonus. The mechanism of the myoclonus remains unclear. MATERIALS AND METHODS: Eighty-four adult male Sprague-Dawley (SD) rats anesthetized intravenously with etomidate, propofol, or lidocaine plus etomidate were observed of the behavioral changes at 0, 1, 2, 3, 4 and 5 min after anesthesia. Five minutes later, glutamate levels were measured in the cerebrospinal fluid (CSF), neocortex and hippocampus. The mRNAs and proteins expression of EAAT1, EAAT2, and GFAP in the neocortex and hippocampus were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot and immunofluorescence staining. RESULTS: Etomidate increased the mean behavioral scores at different time points and the neocortical glutamate level compared with the propofol (p=0.0283) and the lidocaine plus etomidate group (p=0.0035); The correlation analysis revealed a strong correlation between the mean behavioral score and the neocortical glutamate content (Spearman's r=0.6638, p=0.0027). No significant difference was found in the EAAT1, EAAT2, or GFAP mRNAs in the neocortex and hippocampus among three groups; etomidate decreased EAAT1 (p=0.0416 and p=0.0127) and EAAT2 (p=0.0363 and p=0.0109) proteins but increased the GFAP (p=0.0145 and p=0.0149) protein in the neocortex compared to the propofol and lidocaine plus etomidate group. Furthermore, etomidate activated GFAP-positive cells in the neocortex, but conversely inhibited proteins of EAATs in motor cortex. CONCLUSIONS: Etomidate-induced myoclonus is associated with neocortical glutamate accumulation. Suppression of the astrogliosis in neocortex and promoting extracellular glutamate uptake by regulating glutamate transporters (EAATs) in the motor cortex may be the therapeutic target for prevention of etomidate-induced myoclonus.

Serotonin-Its Synthesis and Roles in the Healthy and the Critically Ill.

Serotonin (5-hydroxytryptamine, 5-HT) plays two important roles in humans-one central and the other peripheral-depending on the location of the 5-HT pools of on either side of the blood-brain barrier. In the central nervous system it acts as a neurotransmitter, controlling such brain functions as autonomic neural activity, stress response, body temperature, sleep, mood and appetite. This role is very important in intensive care, as in critically ill patients multiple serotoninergic agents like opioids, antiemetics and antidepressants are frequently used. High serotonin levels lead to altered mental status, deliria, rigidity and myoclonus, together recognized as serotonin syndrome. In its role as a peripheral hormone, serotonin is unique in controlling the functions of several organs. In the gastrointestinal tract it is important for regulating motor and secretory functions. Apart from intestinal motility, energy metabolism is regulated by both central and peripheral serotonin signaling. It also has fundamental effects on hemostasis, vascular tone, heart rate, respiratory drive, cell growth and immunity. Serotonin regulates almost all immune cells in response to inflammation, following the activation of platelets.

Systemic delivery of human GlyR IgG antibody induces GlyR internalization into motor neurons of brainstem and spinal cord with motor dysfunction in mice.

AIMS: Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a life-threatening condition often associated with highly raised serum antibodies to glycine receptors (GlyRs); these bind to the surface of large neurons and interneurons in rodent brain and spinal cord sections and, in vitro, inhibit function and reduce surface expression of the GlyRs. The effects in vivo have not been reported. METHODS: Purified plasma IgG from a GlyR antibody-positive patient with PERM, and a healthy control (HC), was injected daily into the peritoneal cavity of mice for 12 days; lipopolysaccharide (LPS) to open the blood-brain barrier, was injected on days 3 and 8. Based on preliminary data, behavioural tests were only performed 48 h post-LPS on days 5-7 and 10-12. RESULTS: The GlyR IgG injected mice showed impaired ability on the rotarod from days 5 to 10 but this normalized by day 12. There were no other behavioural differences but, at termination (d13), the GlyR IgG-injected mice had IgG deposits on the neurons that express GlyRs in the brainstem and spinal cord. The IgG was not only on the surface but also inside these large GlyR expressing neurons, which continued to express surface GlyR. CONCLUSIONS: Despite the partial clinical phenotype, not uncommon in passive transfer studies, the results suggest that the antibodies had accessed the GlyRs in relevant brain regions, led to antibody-mediated internalization and increased GlyR synthesis, compatible with the temporary loss of function.

Glucose transporter type 1 deficiency syndrome associated with autoantibodies to glutamate receptors.

BACKGROUND: The clinical spectrum of glucose transporter type 1 deficiency syndrome (GLUT1DS) has broadened, with increasing recognition of a milder phenotype. Antibodies targeting the subunits of glutamate receptors (GluRs), including GluN1, GluN2B, and GluD2, have been detected in various neurological disorders. Anti-GluD2 antibodies in particular may be associated with cerebellar symptoms. CASE REPORT: A 3-year-5-month-old boy with normal development exhibited myoclonus refractory to antiepileptic drugs from one year ago. He developed tremor and ataxia. Cerebrospinal fluid (CSF) revealed fasting-state glucose 50 mg/dl (CSF/blood glucose ratio of 0.50). Single photon emission computed tomography with 123I-iodoamphetamine revealed hypoperfusion in the cerebellum. At age 4 years and 5 months, treatment with intravenous methylprednisolone (IVMP) relieved his symptoms and improved the cerebellar hypoperfusion. However, his symptoms reappeared at age 5 years and 1 month. Treatment with IVMP was repeated, resulting in transient disappearance of symptoms. At age 6 years and 9 months, he was diagnosed with GLUT1DS by genetic analysis, and treatment with modified Atkins diet was started with efficacy. Levels of anti-GluN1, -GluN2B, and -GluD2 antibodies in the serum and CSF were measured 4 times. All antibodies in the CSF were elevated over 2 standard deviations above controls, and the levels fluctuated along with the severity of his symptoms. The level of anti-GluD2 antibodies in CSF declined to the normal range only after starting the modified Atkins diet. CONCLUSION: Treatment with IVMP transiently improved this patient's symptoms. Levels of anti-GluR antibodies may be associated with symptom severity.

Spinal cord α-synuclein deposition associated with myoclonus in patients with MSA-C.

OBJECTIVE: To test the hypothesis that myoclonus in patients with multiple system atrophy with predominant cerebellar ataxia (MSA-C) is associated with a heavier burden of α-synuclein deposition in the motor regions of the spinal cord, we compared the degree of α-synuclein deposition in spinal cords of 3 patients with MSA-C with myoclonus and 3 without myoclonus. METHODS: All human tissue was obtained by the Massachusetts General Hospital Department of Pathology with support from and according to neuropathology guidelines of the Massachusetts Alzheimer's Disease Research Center. Tissue was stained with Luxol fast blue and hematoxylin & eosin for morphologic evaluation, and with a mouse monoclonal antibody to α-synuclein and Vectastain DAB kit. Images of the spinal cord sections were digitized using a 10× objective lens. Grayscale versions of these images were transferred to ImageJ software for quantitative analysis of 8 different regions of interest (ROIs) in the spinal cord: dorsal column, anterior white column, left and right dorsal horns, left and right anterior horns, and left and right lateral corticospinal tracts. A mixed-effect, multiple linear regression model was constructed to determine if patients with and without myoclonus had significantly different distributions of α-synuclein deposition across the various ROIs. RESULTS: Patients with myoclonus had more α-synuclein in the anterior horns (p < 0.001) and lateral corticospinal tracts (p = 0.02) than those without myoclonus. CONCLUSIONS: In MSA-C, myoclonus appears to be associated with a higher burden of α-synuclein deposition within spinal cord motor regions. Future studies with more patients will be needed to confirm these findings.

Twenty years on: Myoclonus-dystonia and ε-sarcoglycan - neurodevelopment, channel, and signaling dysfunction.

Myoclonus-dystonia is a clinical syndrome characterized by a typical childhood onset of myoclonic jerks and dystonia involving the neck, trunk, and upper limbs. Psychiatric symptomatology, namely, alcohol dependence and phobic and obsessive-compulsive disorder, is also part of the clinical picture. Zonisamide has demonstrated effectiveness at reducing both myoclonus and dystonia, and deep brain stimulation seems to be an effective and long-lasting therapeutic option for medication-refractory cases. In a subset of patients, myoclonus-dystonia is associated with pathogenic variants in the epsilon-sarcoglycan gene, located on chromosome 7q21, and up to now, more than 100 different pathogenic variants of the epsilon-sarcoglycan gene have been described. In a few families with a clinical phenotype resembling myoclonus-dystonia associated with distinct clinical features, variants have been identified in genes involved in novel pathways such as calcium channel regulation and neurodevelopment. Because of phenotypic similarities with epsilon-sarcoglycan gene-related myoclonus-dystonia, these conditions can be collectively classified as "myoclonus-dystonia syndromes." In the present article, we present myoclonus-dystonia caused by epsilon-sarcoglycan gene mutations, with a focus on genetics and underlying disease mechanisms. Second, we review those conditions falling within the spectrum of myoclonus-dystonia syndromes, highlighting their genetic background and involved pathways. Finally, we critically discuss the normal and pathological function of the epsilon-sarcoglycan gene and its product, suggesting a role in the stabilization of the dopaminergic membrane via regulation of calcium homeostasis and in the neurodevelopmental process involving the cerebello-thalamo-pallido-cortical network. © 2019 International Parkinson and Movement Disorder Society.

[VOLTAGE-GATED CALCIUM CHANNELS: CLASSIFICATION AND PHARMACOLOGICAL PROPERTIES (PART I).]

Calcium influx though voltage-gated calcium channels mediate a huge amount of physiological events and cellular responses. Numerous scientific reports indicate that calcium channels are involved in synaptic transmission, neurotransmitter release, regulation of gene expression, cellular membrane voltage oscillations, pacemaker activity, secretion of specific substances from nerve and secretory cells, morphological differentiation, activation of calcium-dependent enzymes, etc. This review represents the modern classification, molecular structure, physiological and pharmacological properties of voltage-gated calcium channels expressed in mammalian cells.

The association between seizure predisposition and inflammation in a rat model of fatty liver disease.

The association between inflammation and the induction of seizures is well-known. It has been reported that non-alcoholic fatty liver disease (NAFLD) is associated with a pro-inflammatory state, and systemic inflammation may trigger central nervous system inflammation. This study aims to identify the impact of inflammation in a rat model of fatty liver on the propensity and severity of pentylenetetrazol (PTZ)-induced seizures. Twenty-four male Sprague-Dawley rats were divided into four groups. Groups 1 and 2 were administered a 35 % fructose solution over 8 weeks to induce the development of fatty liver while Groups 3 and 4 were fed normally as controls. Groups 1 and 3 were given 70 mg/kg PTZ, determining Racine Convulsion Scores (RCS) and onset times of the first myoclonic jerks (FMJ). Groups 2 and 4 were administered 35 mg/kg of PTZ, then EEG recordings were obtained to evaluate spike percentages. TNF-α levels in brain and liver tissues were also measured. While RCS's of fatty liver rats were higher than the control group (p > 0.05) as well as spike percentages (p < 0.05), FMJ onset time was significantly shorter. TNF-α levels in liver and brain tissues of the rats with NAFLD were significantly higher than the control rats. We found that rats with NAFLD demonstrated decreased seizure thresholds, possibly due to increased cytokine levels systemically and within the central nervous system. As such, epilepsy patients taking medications that may predispose the development of NAFLD must be carefully managed to prevent the possibility of increased seizure episodes.

The epidemiological, clinical, and laboratory features of sporadic Creutzfeldt-Jakob disease patients in China: surveillance data from 2006 to 2010.

BACKGROUND: Creutzfeldt-Jakob disease (CJD) is a rare, rapidly progressive fatal central nervous system disorder, which consists of three main catalogues: sporadic, familial, and iatrogenic CJD. METHODOLOGY/PRINCIPAL FINDINGS: In China, the surveillance for CJD started in 2006, covering 12 provincial Centers for Disease Control and Prevention (CDCs) and 15 hospitals. From 2006 to 2010, 624 suspected patients were referred to China CJD surveillance. The epidemiological, clinical and laboratory features of sporadic CJD (sCJD) were analysed. Both groups of probable and possible sCJD showed highest incidences in the population of 60 to 69 year-olds. The most common presenting symptoms were progressive dementia and mental-related symptoms (neurological symptoms including sleeping turbulence, depression, anxiety and stress). Among the four main clinical manifestations, myoclonus was more frequently observed in the probable sCJD patients. About 2/3 of probable sCJD cases showed positive 14-3-3 in CSF and/or periodic sharp wave complexes (PSWC) in electroencephalography (EEG). The presence of myoclonus was significantly closely related with the appearance of PSWC in EEG. Polymorphisms of codon 129 in PRNP of the notified cases revealed a highly predominant M129M genotype in Han Chinese. Among 23 genetic human prion diseases, ten were D178N/M129M Fatal familial insomnia (FFI) and five were T188K genetic CJD (gCJD), possibly indicating a special distribution of gCJD-related mutations in Han Chinese. CONCLUSION: From the period of 2006 to 2010, 261 patients were diagnosed as sCJD and 23 patients were diagnosed as genetic human prion diseases in China. The epidemiological, clinical and laboratory analysis data were consistent with the characteristics of sporadic CJD, which provide insight into the features of CJD in China.

The nigrostriatal pathway in Creutzfeldt-Jakob disease.

Parkinsonism, chorea, and dystonia are well-known clinical manifestations of Creutzfeldt-Jakob disease (CJD), but lesions of the nigrostriatal pathway have never been thoroughly studied. We performed a detailed neuropathologic study of the nigrostriatal pathway in 15 sporadic CJD and 2 variant CJD cases that included clinical correlations and assessment of neuron subtype loss, distribution of prion protein, alpha-synuclein, ubiquitin, and 14-3-3 aggregation. We found evidence of nigrostriatal pathway damage in these CJD cases. Dopaminergic neurons and striatal outflow neurons were markedly affected in sporadic CJD, whereas cholinergic interneurons were spared. In cases of CJD with chorea or myoclonus, there was less presynaptic dopaminergic loss than in cases of CJD with parkinsonism. The 2 variant CJD cases with parkinsonism or chorea showed severe cholinergic interneuron loss in the caudate and putamen, a pattern that differed from that found in sporadic CJD. alpha-Synuclein, ubiquitin, and 14-3-3 aggregation coexisted with prion protein aggregation, thereby generating mixed pathological features. These findings suggest a possible pathophysiological overlap of abnormal protein aggregation in CJD and Parkinson disease.

Reduced striatal D2 receptor binding in myoclonus-dystonia.

PURPOSE: To study striatal dopamine D(2) receptor availability in DYT11 mutation carriers of the autosomal dominantly inherited disorder myoclonus-dystonia (M-D). METHODS: Fifteen DYT11 mutation carriers (11 clinically affected) and 15 age- and sex-matched controls were studied using (123)I-IBZM SPECT. Specific striatal binding ratios were calculated using standard templates for striatum and occipital areas. RESULTS: Multivariate analysis with corrections for ageing and smoking showed significantly lower specific striatal to occipital IBZM uptake ratios (SORs) both in the left and right striatum in clinically affected patients and also in all DYT11 mutation carriers compared to control subjects. CONCLUSIONS: Our findings are consistent with the theory of reduced dopamine D(2) receptor (D2R) availability in dystonia, although the possibility of increased endogenous dopamine, and consequently, competitive D2R occupancy cannot be ruled out.

MR spectroscopy findings in Lafora disease.

PURPOSE: Our aim was to investigate the [(1)H] MR spectroscopy (MRS) findings of Lafora Disease (LD), which is a disabling form of progressive myoclonic epilepsy. METHODS: Twelve patients diagnosed with LD and 12 control subjects underwent MRS studies with single-voxels of 8 cc obtained in the frontal lobe, pons, and cerebellum. The metabolites and NAA/Cr, NAA/Cho, Cho/Cr, mI/Cr ratios were calculated. Subgroup analysis was also done between 5 patients with EPM2B and 6 patients with EPM2A mutations. Two investigators scored neurological symptom severity. RESULTS: We found a statistically significant difference of NAA/Cho ratio in LD patients compared with normal controls in cerebellum (P= 0.04). In addition, both myoclonus and ataxia scores showed significant correlation with NAA/Cho ratios in the pons (P= 0.03, P= 0.04) and in the cerebellum (P= 0.04, P= 0.01), respectively. CONCLUSION: We conclude that the cerebellum is the mostly affected structure in LD and there are significant correlations of MRS findings with some clinical parameters. The differences in the group may be related to different genetic mutations besides disease duration and other clinical variables. MRS studies could provide insights about the severity of the involvement of LD.

Memantine-induced myoclonus and delirium exacerbated by trimethoprim.

OBJECTIVE: To report a case of myoclonus and delirium seen in a patient taking a combination of memantine and trimethoprim. CASE SUMMARY: A 78-year-old woman was admitted to the medical center in October 2007 with rapid deterioration of Alzheimer's dementia and progressive myoclonus. In 2003, donepezil 5 mg/day had been initiated and her disease slowly progressed. In 2006, memantine 10 mg twice daily was added. Myoclonic activity and delirium were noted in 2007 when a urinary tract infection (UTI) was treated with double-strength trimethoprim/sulfamethoxazole (TMP/SMX 160 mg/800 mg). After discontinuation of TMP/SMX, the patient's condition returned to baseline level. Several weeks later, trimethoprim 100 mg daily was added for UTI prophylaxis. Within weeks, spontaneous generalized myoclonic activity resumed to the extent that the patient was unable to walk. She became increasingly delirious. A week before admission, levodopa/carbidopa 250 mg/100 mg was added for presumptive restless legs syndrome and the patient became extremely delirious and combative, requiring hospitalization. Because of the striking similarity of dose-related toxicities reported with amantadine, a slightly different aminoadamantane, memantine was withheld. Trimethoprim was discontinued due to a likely interaction with memantine. Donepezil and famotidine were withheld due to questions of therapeutic necessity. After 3 days, the myoclonus had completely resolved and the patient was no longer agitated or combative during the remainder of her hospitalization. She was cooperative and ambulatory and was discharged. DISCUSSION: Memantine is cleared primarily through the kidneys and should be renally dosed. Drugs that interfere with elimination-that is, other drugs utilizing the organic cation transporter-2 in the tubule, such as trimethoprim, metformin, or imipramine-may lead to drug accumulation. Our patient, who had impaired renal function, developed severe myoclonus and delirium after trimethoprim was added to therapy with memantine. As there were no reports of myoclonus and delirium with this drug combination and because of the structural, pharmacologic, and pharmacokinetic similarities between the aminoadamantanes memantine and amantadine, we researched similar dual adverse effects reported with amantadine. Amantadine has led to the same adverse effects noted in our patient, not only in patients with renal impairment, but also in one patient when trimethoprim was added to a stable dose of amantadine. CONCLUSIONS: This is the first reported case of a drug interaction between memantine and trimethoprim, which resulted in clinically significant myoclonus and delirium. Clinicians should be aware of this potential interaction, since there have been reports of this adverse effect with the use of amantadine. Because memantine chemically and pharmacologically resembles amantadine, it is quite possible that their toxicities are similar.

Cerebral glucose metabolism in oculopalatal tremor.

No study adopted the statistical parametric mapping (SPM) analyses of (18)F-fluorodeoxy glucose (FDG) PET in a large number of patients with oculopalatal tremor (OPT). To determine regional cerebral glucose metabolism in patients with OPT, nine patients with OPT underwent FDG-PET of the brain. Their glucose metabolism was compared with that of 50 normal controls (NC) by using SPM analyses. Three patients had bilateral and six showed unilateral pseudohypertrophic degeneration of the inferior olivary nucleus (ION) on MRI. Compared with NC, OPT patients did not show any metabolic derangement in the anterolateral medulla where the pseudohypertrophic ION locates. Instead, six patients with unilateral ION changes had hypometabolism in ipsilesional pontine tegmentum and hypermetabolism in contralesional thalamus. Their metabolic changes did not depend on the lateralization of ION changes. Our study failed to present any metabolic evidence for the role of ION in the generation of OPT. In part, the failure might originate from the different pathomechanism between OPT and pure palatal tremor or sensitivity/specificity issues of PET and SPM analyses. But, our results suggest that impaired cell groups of the paramedian tract and thalamic tremor cells may contribute to the generation of OPT.

[Involvement of endogenous histamine in modulatory effect of morphine on seizure susceptibility in mice].

OBJECTIVE: To investigate the modulatory effects of morphine on the susceptibility to pentylenetetrazole-induced seizures, and the involvement of endogenous histamine in this process. METHODS: Both the wild-type (WT) mice and histidine decarboxylase (a key enzyme for histamine biosynthesis) deficient (HDC-KO) mice were subcutaneously injected with different doses of morphine, and 1 hour later the pentylenetetrazole solution (1.5 %) was infused into the tail vein at a constant rate of 0.3 ml/min. The minimal dose of pentylenetetrazole (mg/kg) needed to induce myoclonic jerks and clonus convulsion was recorded as the thresholds of seizures. RESULT: In WT mice, morphine dose-dependently decreased the thresholds of both myoclonic jerks and clonus convulsion. In HDC-KO mice, morphine at 10 mg/kg only significantly decreased the threshold of myoclonic jerks from (38.6 +/-2.9)mg/kg to (32.5 +/-0.7)mg/kg, but had no significant effect on the threshold of clonus convulsion [from (51.8 +/-2.1)mg/kg to (47.6 +/-1.2)mg/kg]. In addition, the value of decreased myoclonic jerks (15.8 +/-1.4)% and clonus convulsion (8.3 +/-0.9)% thresholds were much lower in HDC-KO mice than in WT mice [(26.1 +/-2.5)% and (20.8 +/-2.4)%, respectively]. CONCLUSION: Morphine can decrease the thresholds of pentylenetetrazole in induction of seizure, and the endogenous histamine may be involved in this process.

NMDA receptor-mediated excitotoxicity contributes to the cerebral hypoxic injury of a rat model of posthypoxic myoclonus.

Cardiac arrest-induced cerebral hypoxic injury could induce posthypoxic movement disorders. Here we investigated the effects of memantine, an NMDA receptor channel blocker, on the neurodegeneration occurred in an established rat model of posthypoxic myoclonus. We found that administration of memantine for 7 days significantly reduced cerebral hypoxia-induced neurodegeneration in the CA1 of the hippocampus, the reticular thalamic nucleus (RTN) and the primary fissure of the cerebellum of the posthypoxic animals. The results suggest that the neurodegeneration observed in specific areas of the brain of the posthypoxic rats is contributed by NMDA receptor-mediated excitotoxicity.

Glucose utilization in the inferior cerebellar vermis and ocular myoclonus.

In a patient with symptomatic ocular myoclonus, the authors observed the regional cerebral metabolic rate of glucose use (rCMRGlu) before and after successful treatment with clonazepam. Even after the symptoms resolved, the rCMRGlu in the hypertrophic olive increased persistently, whereas that in the inferior cerebellar vermis contralateral to the hypertrophic olive decreased. The inferior cerebellar vermis, belonging to the vestibulocerebellar system, may be associated with the generation of symptomatic ocular myoclonus.

Some genetic and biochemical aspects of myoclonus.

Can a gene defect be responsible for the occurrence in an individual, at a particular age, of such a muscle twitch followed by relaxation called: "myoclonus" and defined as sudden, brief, shock-like movements? Genetic defects could indeed determine a subsequent cascade of molecular events (caused by abnormal encoded proteins) that would produce new aberrant cellular relationships in a particular area of the CNS leading to re-built "myoclonogenic" neuronal networks. This can be illustrated reviewing some inherited neurological entities that are characterized by a predominant myoclonic picture and among which a clear gene defect has been identified. In the second part of this chapter, we will also propose a new point of view on how some structural genes could, under certain conditions, when altered, produced idiopathic generalized epilepsy with myoclonic jerks, taking juvenile myoclonic epilepsy (JME) and the myoclonin (EFHC-1) gene as examples.

Post-hypoxic myoclonus induces Fos expression in the reticular thalamic nucleus and neurons in the brainstem.

Post-hypoxic myoclonus is a movement disorder characterized by brief, sudden involuntary muscle jerks. Although the mechanism underlying this disorder remains unclear, earlier pharmacological studies indicated that aberrant activity of specific neuronal circuitry in the central nervous system causes this disorder. In the present study, Fos protein, an immediate-early gene product, was used as a marker of neuronal activity to identify the brain nuclei possibly involved in post-hypoxic myoclonus. We found that Fos protein was immunologically detected in the reticular thalamic nucleus (RT), the medial longitudinal fasciculus (MLF) as well as in the locus coeruleus (LC) and the periventricular gray substance (PVG) in post-hypoxic rats that developed myoclonus in response to auditory stimuli. Fos was not detected in these nuclei from rats that underwent 4 min of cardiac arrest without myoclonus. Electrolytic lesions of the RT or MLF but not the LC/PVG significantly reduced auditory stimulated myoclonus in the post-hypoxic rats. The results suggest that neuronal activity in the RT and the MLF plays a contributing role in post-hypoxic myoclonus.