Involvement of GABA(A) receptors in myoclonus

Tongue Biting Event in Patients with Sleep-Related Facial Mandibular Myoclonus: A Case Series Study

Background

Sleep-related facial mandibular myoclonus (SRFMM) remains rare in clinical practice. The aim of this study was to provide a comprehensive understanding of the electroclinical manner, therapeutic regimen, and prognosis of SRFMM.

Methods

Twenty-three patients who were diagnosed with SRFMM by clinical manifestation, video-electroencephalography (EEG) and electromyography over bilateral masseter and temporalis muscles were enrolled. Clinical and electrophysiological evaluation as well as follow-up information were recorded and analyzed.

Results

The cohort involved 4 infants and 19 adults with a mean onset age of 43.5 years for SRFMM, among whom 19 were male. Twenty-one patients complained of tongue injuries and disturbed night-time sleep. SRFMM in 4 patients were ascribed to oral aripiprazole, brainstem ischemia and brain trauma. In 62 SRFMM episodes, 93.5% occurred in NREM sleep and 6.5% in REM sleep, and all events were associated with EEG arousals. In 13 patients with or without clonazepam, the motor events gradually disappeared, and the rest turned to be sporadic.

Conclusion

SRFMM is a characteristic parasomnia manifested by tongue biting and accompanying facial mandibular myoclonus, leading to disrupted sleep. Besides adults, infants can also experience SRFMM with spontaneous remission. Most patients respond well to clonazepam, eventually with favorable prognosis.

Lance-Adams Syndrome: Case series and literature review

Background

Lance-Adams Syndrome (LAS) is a rare complication of successful cardiopulmonary resuscitation (CPR). It is a form of posthypoxic myoclonus characterized by action or intention myoclonus developing days to months after an hypoxic insult to the brain. LAS, especially early in a patient's clinical course, can be challenging to diagnose. Electroencephalogram (EEG) pattern of midline spike-wave discharge associated with favorable prognosis. There is no consensus in treatment of LAS but use of various anti-epileptic medications has been documented in literature.

Case Presentation

In this case series, all of the patients presented after achieving return of spontaneous circulation (ROSC) and subsequently developed myoclonus. EEG findings beyond the initial hospitalization continued to show later showed changes consistent with LAS in three of the four patients. Different combinations of AEDs were used in the management of LAS with variable success and adverse effects.

Conclusion

Our cases highlight that the characteristic EEG pattern can be useful in the diagnosis of LAS and allow for better prognostication and management in patients with posthypoxic myoclonus. We reviewed the available literature to better understand the prevalence, mechanism, clinical presentation, diagnosis, and management of LAS.

New Phenylglycinamide Derivatives with Hybrid Structure as Candidates for New Broad-Spectrum Anticonvulsants

In the present study, a focused combinatorial chemistry approach was applied to merge structural fragments of well-known TRPV1 antagonists with a potent anticonvulsant lead compound, KA-104, that was previously discovered by our group. Consequently, a series of 22 original compounds has been designed, synthesized, and characterized in the in vivo and in vitro assays. The obtained compounds showed robust in vivo antiseizure activity in the maximal electroshock (MES) test and in the 6 Hz seizure model (using both 32 and 44 mA current intensities). The most potent compounds 53 and 60 displayed the following pharmacological profile: ED₅₀ = 89.7 mg/kg (MES), ED₅₀ = 29.9 mg/kg (6 Hz, 32 mA), ED₅₀ = 68.0 mg/kg (6 Hz, 44 mA), and ED₅₀ = 73.6 mg/kg (MES), ED₅₀ = 24.6 mg/kg (6 Hz, 32 mA), and ED₅₀ = 56.3 mg/kg (6 Hz, 44 mA), respectively. Additionally, 53 and 60 were effective in the ivPTZ seizure threshold and had no influence on the grip strength and body temperature in mice. The in vitro binding and functional assays indicated a multimodal mechanism of action for 53 and 60. These molecules, beyond TRPV1 antagonism, inhibited calcium currents and fast sodium currents in patch-clamp assays. Further studies proved beneficial in vitro ADME-Tox properties for 53 and 60 (i.e., high metabolic stability, weak influence on CYPs, no neurotoxicity, etc.). Overall, 53 and 60 seem to be interesting candidates for future preclinical development in epilepsy and pain indications due to their interaction with the TRPV1 channel.

Lance Adams syndrome: two cases report and literature review

Hypoxic myoclonus, also known as Lance Adams syndrome, is a rare syndrome that results from the serious brain damage caused by cerebral hypoxia that often follows cardiopulmonary resuscitation. This current case report describes two patients with post-hypoxic myoclonus, both of whom received cardiopulmonary resuscitation. The neurological symptoms of these two patients were significantly improved by the administration of clonazepam and sodium valproate sustained-release tablets. The report presents a literature review detailing the pathogenesis, diagnosis and treatment of Lance Adams syndrome. The timely diagnosis and treatment of Lance Adams syndrome can significantly improve the quality of life of patients. Valproic acid, clonazepam and other antiepileptic drugs can be used. Whether levetiracetam is effective for cortical myoclonus requires further clinical study.

Lance Adams Syndrome: A Rare Case Presentation of Myoclonus From Chronic Hypoxia Secondary to COVID-19 Infection

Coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) and since the outbreak, many neurological features and syndromes are reported with this multi-organ viral infection. Lance-Adams syndrome (LAS) also referred to as chronic post hypoxic myoclonus is defined as action myoclonus which can occur as generalized, focal, or multifocal repeated myoclonic motor movements which involve the face, trunk, or extremities and it is one of the neurological complications that are related to COVID-19 infection. LAS is reported as a delayed complication of cardiac arrest, which causes cerebral hypoxia leading to myoclonus. We report a case of a 58-year-old male patient diagnosed as a case of LAS secondary to hypoxia occurring because of COVID-19 without cardiac arrest and to the best of our knowledge it is the second case reported with this similar mechanism. Moreover, we discuss the possible pathophysiological relationship between LAS and COVID-19 and various treatment strategies. Eventually, we review the related articles in the literature regarding the LAS and various types of myoclonus associated with COVID-19 infection.

Electroclinical Features of Sleep-Related Head Jerk

STUDY OBJECTIVES

To evaluate clinical and electrophysiological features of sleep-related head jerk (SRHJ) and electromyographic activity of superficial neck muscles during head jerk.

METHODS

Totally, 850 cases with video-polysomnography recording were collected, among which 50 presented with SRHJ. In these 50 patients, 15 underwent electromyography (EMG) check on bilateral sternocleidomastoid (SCM) and trapezius muscles as well as chin, while 35 had only chin EMG check. Further, the sensitivity and specificity of the both EMGs were calculated and compared.

RESULTS

Six among the 50 SRHJ patients had a primary complaint of involuntary head jerks associated with impaired sleep. Approximately 76.1% of head jerks occurred during REM sleep with the median head jerk index of 5.9/h, 64.5% of which were associated with electroencephalogram arousals and 66.4% with body movements. One patient showed SRHJ predominantly in NREM sleep but also in wakefulness. Surface EMG of SCM/trapezius muscles showed a sensitivity of 92% and a specificity of 97.8%, whereas chin EMG had a sensitivity of 14.5% and a specificity of 98.8%.

CONCLUSION

SRHJ was associated with electroencephalogram arousals and might interfere with sleep. Surface EMG of SCM/trapezius muscles exhibited a good accuracy in the revelation of SRHJ.

Transcranial magnetic stimulation as a tool to understand genetic conditions associated with epilepsy

Advances in genetics may enable a deeper understanding of disease mechanisms and promote a shift to more personalised medicine in the epilepsies. At present, understanding of consequences of genetic variants mainly relies on preclinical functional work; tools for acquiring similar data from the living human brain are needed. Transcranial magnetic stimulation (TMS), in particular paired-pulse TMS protocols which depend on the function of cortical GABAergic interneuron networks, has the potential to become such a tool. For this report, we identified and reviewed 23 publications on TMS studies of cortical excitability and inhibition in 15 different genes or conditions relevant to epilepsy. Reduced short-interval intracortical inhibition (SICI) and reduced cortical silent period (CSP) duration were the most commonly reported findings, suggesting abnormal GABA_A - (SICI) or GABA_B ergic (CSP) signalling. For several conditions, these findings are plausible based on established evidence of involvement of the GABAergic system; for some others, they may inform future research around such mechanisms. Challenges of TMS include lack of complete understanding of the neural underpinnings of the measures used: hypotheses and analyses should be based on existing clinical and preclinical data. Further pitfalls include gathering sufficient numbers of participants, and the effect of confounding factors, especially medications. TMS-EEG is a unique perturbational technique to study the intrinsic properties of the cortex with excellent temporal resolution; while it has the potential to provide further information of use in interpreting effects of genetic variants, currently the links between measures and neurophysiology are less established. Despite these challenges, TMS is a tool with potential for elucidating the system-level in vivo functional consequences of genetic variants in people carrying genetic changes of interest, providing unique insights.

Increasing Evidence for the Use of Sodium Oxybate in Multi-Drug-Resistant Lance-Adams Syndrome

Background

Treatment of posthypoxic myoclonus (PHM) can be a challenge in patients not responsive to first-line medications. PMH is a rare condition that has a dramatic impact on patients' quality of life. Refractory cases are not uncommon.

Case report

We report a patient with PHM non-responsive to conventional treatments who showed a dramatic improvement with sodium oxybate (SBX). Cases of PHM treated with SBX reported in the literature were reviewed.

Discussion

Resting and stimulus-induced myoclonus respond robustly to SBX, with significant improvement in patients' quality of life. SBX may be considered in patients with PHM resistant to first-line medications.

Effect of Tadalafil on Seizure Threshold and Activity of Antiepileptic Drugs in Three Acute Seizure Tests in Mice

Tadalafil, a selective phosphodiesterase type 5 inhibitor, is a long-acting oral agent for the treatment of erectile dysfunction of multiple etiologies. Although generalized tonic-clonic seizures were reported in a healthy man after taking tadalafil, the influence of tadalafil on seizure susceptibility has not been studied so far. Therefore, the aim of the present study was to investigate the effect of tadalafil on seizure threshold as well as on the activity of some first- and second-generation antiepileptic drugs in three acute seizure tests in mice. The obtained results showed that tadalafil, at the highest dose tested (20 mg/kg), significantly decreased the threshold for the first myoclonic twitch in the intravenous pentylenetetrazole (i.v. PTZ) seizure test. It did not affect the threshold for generalized clonic seizure and forelimb tonus in the i.v. PTZ, for tonic hindlimb extension in the maximal electroshock seizure threshold test, and for psychomotor seizure in the 6-Hz-induced seizure threshold test. Tadalafil did not alter the anticonvulsant activity of any of the studied antiepileptic drugs in electrically induced seizure tests. Interestingly, tadalafil potentiated the anticonvulsant activity of clonazepam and decreased the anticonvulsant activity of oxcarbazepine in the i.v. PTZ test. These interactions were pharmacodynamic in nature, as tadalafil did not alter clonazepam and oxcarbazepine concentrations both in serum and brain tissue. Furthermore, neither tadalafil alone nor its combinations with the studied antiepileptic drugs produced any significant impairment of motor coordination (assessed in the chimney test), muscular strength (investigated in the grip-strength test), and long-term memory (assessed in the passive avoidance task). In conclusion, tadalafil may increase the risk of myoclonic seizure and decrease the anticonvulsant efficacy of oxcarbazepine. Further studies are warranted to evaluate the safety of tadalafil usage in patients with epilepsy.

Lance–Adams syndrome: A special case of a mother

Predicting the neurological outcome in survivors of cardiorespiratory arrest is difficult. A distinction has been made between acute and chronic posthypoxic myoclonus, called myoclonic status epilepticus and Lance–Adams syndrome (LAS), respectively, with the acute condition carrying a bad prognosis. Here, we report a case of a 37-year-old female who developed seizures after a successful cardiopulmonary resuscitation. The available literature on such cases is very rare and has generally mentioned a poor outcome. However, our patient was successfully managed and showed clinical features of LAS. Thus, making an early diagnosis and proper management of hypoxic brain insults is positively related to improving the patient's functional outcome.

The role of the cerebellum in the pathogenesis of cortical myoclonus

The putative involvement of the cerebellum in the pathogenesis of cortical myoclonic syndromes has been long hypothesized, as neuropathological changes in patients with cortical myoclonus have most commonly been found in the cerebellum rather than in the suspected culprit, the primary somatosensory cortex. A model of increased cortical excitability due to loss of cerebellar inhibitory control via cerebello-thalamo-cortical connections has been proposed, but evidence remains equivocal. Here, we explore this hypothesis by examining syndromes that present with cortical myoclonus and ataxia. We first describe common clinical characteristics and underlying neuropathology. We critically view information on cerebellar physiology with regard to motorcortical output and compare findings between hypothesized and reported neurophysiological changes in conditions with cortical myoclonus and ataxia. We synthesize knowledge and focus on neurochemical changes in these conditions. Finally, we propose that the combination of alterations in inhibitory neurotransmission and the presence of cerebellar pathology are important elements in the pathogenesis of cortical myoclonus.

Lance-adams syndrome

It is not common for a patient who survives cardiac arrest to experience significant neurologic impairment such as acute and chronic post-hypoxic myoclonus, known as Lance-Adams syndrome. This syndrome is predominantly characterized by myoclonus that starts days to weeks after cardiopulmonary resuscitation in patients who regained consciousness. Although several cases of LAS were reported, the decisive treatment method has not been established. We report a 43 year old man with Lance-Adams syndrome who showed long-term improvement through treatment with anti-myoclonic agents and participation in a rehabilitation program.

Brain regions and genes affecting myoclonus in animals

Myoclonus is defined as large-amplitude rhythmic movements. Brain regions underlying myoclonic jerks include brainstem, cerebellum, and cortex. Gamma-aminobutyric acid (GABA) appears to be the main neurotransmitter involved in myoclonus, possibly interacting with biogenic amines, opiates, acetylcholine, and glycine. Myoclonic jumping is a specific subtype seen in rodents, comprising rearing and hopping continuously against a wall. Myoclonic jumping can be seen in normal mouse strains, possibly as a result of simply being put inside a cage. Like other types, it is also triggered by changes in GABA, 5HT, and dopamine neurotransmission. Implicated brain regions include hippocampus and dorsal striatum, possibly with respect to D(1) dopamine, NMDA, and δ opioid receptors. There is reason to suspect that myoclonic jumping is underreported due to insufficient observations into mouse cages.

Lance-adams syndrome

Lance-Adams syndrome (LAS) is a rare complication of successful cardiopulmonary resuscitation and is often accompanied by action myoclonus. LAS is seen in patients who have undergone a cardiorespiratory arrest, later regained consciousness, and then developed myoclonus days or weeks after the event. Less than 150 cases of LAS have been reported in the worldwide medical literature. Here, we present a 32-year-old man who suffered from myoclonus after hypoxic brain damage due to hanging himself. This case was diagnosed as Lance-Adams syndrome according to a history of hypoxic brain damage, the clinical features, and the neuroimages such as brain SPECT. Making an early diagnosis and properly managing LAS is positively related to improving the patient's functional outcome. If patients have posthypoxic myoclonus after successful cardiopulmonary resuscitation, we should consider the diagnosis of LAS and initiate a proper rehabilitation program.

Triad stimulation frequency for cortical facilitation in cortical myoclonus

BACKGROUND

Abnormally enhanced cortical rhythmic activities have been reported in patients with cortical myoclonus. We recently reported a new triad-conditioning transcranial magnetic stimulation (TMS) method to detect the intrinsic rhythms of the primary motor cortex (M1). Triad-conditioning TMS revealed a 40-Hz intrinsic rhythm of M1 in normal subjects. In this investigation, we study the motor cortical facilitation induced by rhythmic triple TMS pulses (triad-conditioning TMS) in patients with cortical myoclonus.

METHODS

Subjects were 7 patients with cortical myoclonus (28-74 years old) and 13 healthy volunteers (30-71 years old). Three conditioning stimuli over M1 at the intensity of 110% active motor threshold preceded the test TMS at various interstimulus intervals corresponding to 10-200 Hz. The resulting amplitudes of conditioned motor evoked potentials recorded from the contralateral hand muscle were compared with those evoked by the test stimulus alone.

RESULTS

The facilitation at 25 ms (40 Hz) observed in normal subjects was absent in patients with cortical myoclonus. Instead, triad-conditioning TMS induced facilitation at a 40 ms interval (25 Hz) in cortical myoclonus.

DISCUSSIONS

This change in the timing of facilitation may be explained by a shift of the most preferential intrinsic rhythm of M1, or by some dysfunction in the interneuronal network in cortical myoclonus.

Use of antiepileptic drugs for hyperkinetic movement disorders

Many studies investigated the use of antiepileptic drugs (AEDs) in several neurological diseases other than epilepsy. These neurological disorders, usually, involve neuronal excitability through the modulating of ion channels, receptors and intracellular signaling pathways, and are the targets of the AEDs. This article provides a review of the clinical efficacy of both conventional and newer AEDs in hyperkinetic movement disorders. Some of these indications for AEDs have been established, while others are under investigation. The modulation of GABAergic transmission may explain the neuronal hyper-excitability that underlies some forms of hyperkinetic movement disorders. So, AEDs able to increase GABAergic neurotransmission may play a role in hyperkinetic movement disorders treatment. Therefore, AEDs could represent a useful therapeutic option in the management of hyperkinetic movement disorders where the available treatments are ineffective.

A Patient with Intractable Posthypoxic Myoclonus (Lance-Adams Syndrome) Treated with Sodium Oxybate

Posthypoxic myoclonus is a rare and devastating complication of near-fatal cardiopulmonary arrest. Despite treatment with available anti-myoclonic agents, some patients may recover cognitively but remain completely disabled by severe myoclonus. We report a 16-year-old patient with severe treatment-refractory posthypoxic myoclonus, which improved markedly with administration of the drug sodium oxybate.

Lance-Adams syndrome: a report of two cases

Chronic post-hypoxic myoclonus, also known as Lance-Adams syndrome (LAS), is a rare complication of successful cardiopulmanry resuscitation often accompanied by action myoclonus and cerebellar ataxia. It is seen in patients who have undergone a cardiorespiratory arrest, regained consciousness afterwards, and then developed myoclonus days or weeks after the event. Worldwide, 122 cases have been reported in the literature so far, including 1 case of Chinese. Here we report 2 Chinese LAS patients with detailed neuroimagings. Cranial single photon emission computed tomography (SPECT) of patient 1, a 52-year-old woman, showed a mild hypoperfusion in her left temporal lobe, whereas patient 2, a 54-year-old woman, manifested a mild bilateral decrease of glucose metabolism in the frontal lobes and a mild to moderate decrease of the N-acetyl aspartate (NAA) peak in the bilateral hippocampi by cranial [(18)F]-fluorodeoxyglucose positron emission tomographic (PET) scan and cranial magnetic resonance spectroscopy (MRS), respectively. We also review the literature on the neuroimaging, pathogenesis, and treatment of LAS.

Post-hypoxic animal model of myoclonus

Post-hypoxic myoclonus is a form of myoclonus frequently caused by cardiac arrest. Development of an animal model may facilitate understanding of the condition and its treatments. We describe an animal model of post-hypoxic myoclonus developed in our laboratory through cardiac arrest, initially induced by chemical and later by mechanical obstruction of major cardiac vessels. These animals respond to valproate, clonazepam and 5-hydroxytrytophan reminiscent of its human counterpart. We review their behavioral, pharmacological and neuropathological features. Therapy developed for myoclonus in this model may be helpful for myoclonus from other etiologies such as corticobasal degeneration, Lewy-body disorders, Creutzfeld-Jacob disease, Alzheimer's disease.

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.

Inhibition of type A GABA receptors by L-type calcium channel blockers

Modulation of type A GABA receptors (GABAA) by L-type Ca++ channel blockers was investigated. The dihydropyridines nifedipine and nitrendipine, and the phenylalkylamine verapamil inhibited recombinant rat alpha1beta2gamma2 receptors recorded from human embryonic kidney (HEK) 293 cells; nifedipine at low concentrations also elicited modest stimulatory effects on GABA-gated current. The IC50 for GABA current inhibition was lowest for nitrendipine (17.3 +/- 1.3 microM), so subsequent studies were focused on further exploring its mechanism and possible site of action. When co-applied with GABA, nitrendipine had minimal effects on initial current amplitude, but significantly enhanced current decay rate. Nitrendipine-mediated inhibition was subunit-selective, as its IC50 was 10-fold lower in alpha1beta2 receptors. Nitrendipine's effect in recombinant human alpha1beta2gamma2 receptors was similar (IC50=23.0 +/- 1.3 microM) to that observed in rat receptors of the same configuration, indicating the site of action is conserved in the two species. The inhibitory effects were dependent on channel gating, were independent of transmembrane voltage, and were also observed in GABAA receptors recorded from hypothalamic brain slices. The pharmacologic mechanism of inhibition by nitrendipine was non-competitive, indicating it does not act at the GABA binding site. Nitrendipine block was retained in the presence of the benzodiazepine antagonist flumazenil, indicating it does not interact at the benzodiazepine site. The actions of nitrendipine were not affected by a mutation (beta2T246F) that confers resistance to the channel blocker picrotoxin, and they were not altered in the presence of the picrotoxin site antagonist alpha-isopropyl-alpha-methyl-gamma-butyrolactone, demonstrating nitrendipine does not act at the picrotoxin site of the GABAA receptor. Possible interaction of nitrendipine with the Zn++ site was also eliminated, as mutation of beta2 H267 to A, which confers resistance to Zn++, had no effect on nitrendipine-mediated inhibition. Our data suggest some of the central effects of dihydropyridines may be due to actions at GABAA receptors. Moreover, the effects may be mediated through interaction with a novel modulatory site on the GABAA receptor.

Tremor of the mouth floor and anti-glutamic acid decarboxylase autoantibodies

Involuntary movements of the mouth can present as palatal tremor, which is frequently associated with hypertrophy of the inferior olivary nucleus and can be accompanied by contraction of other muscles of the head. We report the case of a 39-year-old man with autoimmune thyroiditis and diabetes who complained of involuntary rhythmic tremor involving the muscles of the floor of the mouth, which interfered with breathing and swallowing. Cerebrospinal fluid (CSF) examination showed the presence of oligoclonal bands and screening for anti-neuronal antibodies revealed high titres of anti-glutamic acid decarboxylase autoantibodies (GAD-Ab). Tremor responded to treatment with benzodiazepines. The correlation between the tremor and antibody positivity is unclear although an alteration of the gabaergic system mediated by the antibodies may be hypothesised on the basis of an inflammatory CSF profile.

Similarities in Mechanisms and Treatments for Epileptic and Nonepileptic Myoclonus

Myoclonus is a disordered movement that may be an ictal phenomenon or may be due to various injuries in brain and spinal cord motor structures. Many epileptic and nonepileptic myoclonic conditions are associated with abnormalities in inhibitory neurotransmission. gamma-Aminobutyric acid type A (GABA(A))-receptor antagonists may trigger myoclonus. Several antiepilepsy drugs (AEDs) effective against myoclonic seizures [valproic acid (VPA), clonazepam (CZP), levetiracetam (LEV)] enhance GABAergic neurotransmission and improve myoclonic movement disorders. Together these associations suggest links between episodic disorders involving synchronous cortical discharges (seizures) and hyperkinetic movement disorders.

Similarities in Mechanisms and Treatments for Epileptic and Nonepileptic Myoclonus

Myoclonus is a disordered movement that may be an ictal phenomenon or may be due to various injuries in brain and spinal cord motor structures. Many epileptic and nonepileptic myoclonic conditions are associated with abnormalities in inhibitory neurotransmission. γ-Aminobutyric acid type A (GABAA)-receptor antagonists may trigger myoclonus. Several antiepilepsy drugs (AEDs) effective against myoclonic seizures [valproic acid (VPA), clonazepam (CZP), levetiracetam (LEV)] enhance GABAergic neurotransmission and improve myoclonic movement disorders. Together these associations suggest links between episodic disorders involving synchronous cortical discharges (seizures) and hyperkinetic movement disorders.

Pallidal administrations of gabazine and 5-AVA affect pressure-induced behavioral disorders in rats

The aim of this work was to study the role of pallidal GABAa and GABAb neurotransmission in the behavioral disorders induced by pressure. The effects of GABAb antagonist 5-aminovalleric acid (5-AVA) or GABAa antagonist gabazine administrations in the globus pallidus (GP) on locomotor and motor hyperactivity (LMA) and myoclonia expressions in the model of the rat submitted to 8 MPa of helium-oxygen breathing mixture were analyzed. The administration of GABAa antagonist gabazine enhances the occurrence of the epileptic seizures, slightly increases LMA but decreases myoclonia. In contrast, the administration of GABAb antagonist 5-AVA decreases both LMA and myoclonia during the compression and the beginning of the holding time at 8 MPa. These data indicate that some behavioral disorders induced by pressure are in relation with GABAergic neurotransmission and establish clearly that GABAa and GABAb receptor mediations have distinct functions in the GP of the rat.

Myoclonus and its disorders

This article defines myoclonus, describes the numerous causes of myoclonus, and summarizes various classification schemes. The electrodiagnostic characteristics and pathophysiology of this movement disorder are described. Treatment of the various forms of myoclonus is also discussed.

An impairment in sniffing contributes to the olfactory impairment in Parkinson's disease

Although the presence of an olfactory impairment in Parkinson's disease (PD) has been recognized for 25 years, its cause remains unclear. Here we suggest a contributing factor to this impairment, namely, that PD impairs active sniffing of odorants. We tested 10 men and 10 women with clinically typical PD, and 20 age- and gender-matched healthy controls, in four olfactory tasks: (i) the University of Pennsylvania smell identification test; (ii and iii) detection threshold tests for the odorants vanillin and propionic acid; and (iv) a two-alternative forced-choice detection paradigm during which sniff parameters (airflow peak rate, mean rate, volume, and duration) were recorded with a pneomatotachograph-coupled spirometer. An additional experiment tested the effect of intentionally increasing sniff vigor on olfactory performance in 20 additional patients. PD patients were significantly impaired in olfactory identification (P < 0.0001) and detection (P < 0.007). As predicted, PD patients were also significantly impaired at sniffing, demonstrating significantly reduced sniff airflow rate (P < 0.01) and volume (P < 0.002). Furthermore, a patient's ability to sniff predicted his or her performance on olfactory tasks, i.e., the more poorly patients sniffed, the worse their performance on olfaction tests (P < 0.009). Finally, increasing sniff vigor improved olfactory performance in those patients whose baseline performance had been poorest (P < 0.05). These findings implicate a sniffing impairment as a component of the olfactory impairment in PD and further depict sniffing as an important component of human olfaction.

Prolonged exposure to hypobaric hypoxia transiently reduces GABA(A) receptor number in mice cerebral cortex

The central nervous system is severely affected by hypoxic conditions, which produce alterations in neural cytoarchitecture and neurotransmission, resulting in a variety of neuropathological conditions such as convulsive states, neurobehavioral impairment and motor CNS alterations. Some of the neuropathologies observed in hypobaric hypoxia, corresponding to high altitude conditions, have been correlated with a loss of balance between excitatory and inhibitory neurotransmission, produced by alterations in glutamatergic and GABAergic receptors. In the present work, we have studied the effect of chronic hypobaric hypoxia (506 hPa, 18 h/day x 21 days) applied to adult male mice on GABA(A) receptors from cerebral cortex, to determine whether hypoxic exposure may irreversibly affect central inhibitory neurotransmission. Saturation curves for [3H]GABA specifically bound to GABA(A) receptors in isolated synaptic membranes showed a 30% decrease in maximal binding capacity after hypoxic exposure (Bmax control, 4.70+/-0.19, hypoxic, 3.33+/-0.10 pmol/mg protein), with no effect on GABA binding sites affinity (Kd control: 159.3+/-13.3 nM, hypoxic: 164.2+/-15.1 nM). Decreased B(max) values were observed up to the 10th post-hypoxic day, returning to control values by the 15th post-hypoxic day. Pharmacological properties of GABA(A) receptor were also affected by hypoxic exposure, with a 45 to 51% increase in the maximal effect by positive allosteric modulators (pentobarbital and 5alpha-pregnan-3alpha-ol-20-one). We conclude that long-term hypoxia produces a significant but reversible reduction on GABA binding to GABA(A) receptor sites in cerebral cortex, which may reflect an adaptive response to this sustained pathophysiological state.