Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023380 (lethargy)
 5,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In chicks with cannulae chronically implanted into the III cerebral ventricle, the effects of a single dose (10 micrograms) of beta-endorphin on GABA and free glutamic acid content, GAD and GABA-T activities in the diencephalon, brain-stem and brain hemispheres were studied at the time of maximal behavioural stuporous state and analgesia. A significant decrease in GABA concentration both in the diencephalon and brain-stem, accompanied by a significant increase in GABA-T activity in the same areas, was shown to occur. No changes were observed in GAD activity and in glutamic acid content in the studied areas of the brain. In conclusion, present experiments suggest that some central effects of a beta-endorphin may be due to an interference with GABA-ergic transmission.
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PMID:Effects of intraventricular beta-endorphin on GABA system in some areas of chick brain. 52 83

The GABAergic agonist, muscimol, and antagonists, picrotoxin and bicuculline, have been studied in rats with chronic portacaval shunts and in rats developing hepatic encephalopathy after massive ischemic necrosis due to hepatic artery ligation within 48 hr of a portacaval shunt. After the chronic portacaval shunt and to a lesser extent in normal rats intraventricular muscimol resulted in chewing and eating behavior, ataxia and loss of balance that lasted 2 to 3 hr. Lethargy, stupor and coma did not occur. Intraventricular saline had no effect. Bicuculline i.p. lessened the effects of the muscimol. In rats developing hepatic encephalopathy, intraventricular muscimol shortened the time to precoma and coma by approximately 40%. Bicuculline i.p. counteracted this effect of muscimol significantly. However, neither bicuculline nor picrotoxin given alone altered the times to precoma (Stage III), coma (Stage IV) or death. While hepatic encephalopathy in this experimental model is susceptible to GABAergic effects, its natural progression does not appear to be due to GABA.
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PMID:In vivo studies of GABAergic effects in experimental hepatic encephalopathy. 375 44

We encountered an apparent bilateral internuclear ophthalmoplegia (INO) in a stuporous patient who used narcotics and benzodiazepines and had taken phenytoin sodium for drug-withdrawal seizures. The INO was promptly reversed by administration of the narcotic antagonist naloxone, which binds opiate receptors. This suggests the INO resulted from a specific toxic effect of narcotics, but opiate receptors have not been anatomically demonstrated within the medial longitudinal fasciculus or associated structures. Stimulation of inhibitory GABA-ergic (alpha-aminobutyric acid) vestibulo-ocular fibers may have been related to INO in this case.
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PMID:Bilateral internuclear ophthalmoplegia reversed by naloxone. 683 Apr 74

In previous work we have shown that GABAB receptors are required for expression of absence seizures in the lethargic (lh/lh) mouse model; that lh/lh mice have increased numbers of GABAB binding sites compared to nonepileptic littermates (designated +/+); and that the magnitude of the increased number of GABAB receptors in lh/lh mice correlated positively with the frequency of absence seizures. We performed this study to delineate the neural network in which GABAB receptors regulate absence seizures in lh/lh mice. We designed three successive screens which had to be passed by a candidate neuronal population before it could be considered a member of the neural network in which GABAB receptors regulate absence seizures. First, the neuronal populations in lh/lh mice had to have enriched GABAB binding sites compared to homologous populations in matched nonepileptic controls; baclofen-displaceable 3H-GABA binding was measured in autoradiograms for this screen. Second, the candidate populations had to generate spike-wave discharges (SWDs) during absence seizures in lh/lh mice; bipolar recording electrodes implanted into candidate neuronal structures were used in this screen. Third, the candidate populations had to demonstrate GABAB receptor-mediated regulation of absence seizures in lh/lh mice; microinjections of a GABAB agonist [(-)-baclofen] and antagonist (CGP 35348) were used for this screen. In this study we found that anterior ventral lateral thalamic nucleus (VLa), nucleus reticularis thalami (NRT), nucleus reuniens (RE) passed all three screens, and hence are members of the neural network in which GABAB receptors regulate absence seizures in lh/lh mice.
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PMID:Neural network of structures in which GABAB receptors regulate absence seizures in the lethargic (lh/lh) mouse model. 747 90

Previously, we have shown a significant increase in number of GABAB receptor binding sites in neocortex and thalamus of lethargic (lh/lh) mice, a mutant strain exhibiting absence seizures. This study was performed to test our hypothesis that presynaptic GABAB receptors would inhibit [3H]GABA release to a greater degree in lh/lh mice compared with their nonepileptic littermates (designated +/+). Synaptosomes isolated from neocortex and thalamus of age-matched male lh/lh and +/+ mice were similar in uptake of [3H]GABA. In the neocortical preparation, baclofen dose-dependently inhibited [3H]GABA release evoked by 12 mM KCl, an effect mediated by GABAB receptors. The maximal inhibition (Imax) value was significantly greater (80%) in lh/lh than +/+ mice, whereas the IC50 (3 microM) was unchanged. In the thalamic preparation, the effect of baclofen (50 microM) was 58% less robust in lh/lh mice. Other effects mediated by GABAB receptors (inhibitions in Ca2+ uptake and cyclic AMP formation) were also significantly reduced in thalamic synaptosomes from lh/lh mice. These data suggest a greater presynaptic GABAB receptor-mediated effect in neocortex and a reduced effect in thalamic nuclei of lh/lh mice. It is possible that selective effects of presynaptic GABAB receptors or GABA release in neocortex and thalamic nuclei of lh/lh mice may contribute to mechanisms underlying absence seizures.
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PMID:GABAB receptor-mediated effects in synaptosomes of lethargic (lh/lh) mice. 759 94

Susceptibility to audiogenic seizures (AGS) is observed during ethanol withdrawal (ETX). The pontine reticular formation (PRF) is implicated in the propagation pathway for AGS during ETX. The present study examined the changes in single PRF neuronal firing patterns produced by ethanol and during ETX following repeated intragastrically administered ethanol. Microwire electrode bundles were implanted into PRF and single neuronal responses in freely moving rats were examined. During initial ethanol administration the animals were stuporous, and spontaneous and acoustically-evoked PRF neuronal firing were reduced significantly. During ETX the animals were susceptible to AGS and displayed agitated and irritable behavior. At this time a significant increase in spontaneous and acoustically-evoked PRF neuronal firing was observed. Repetition-induced response attenuation (habituation) of PRF neuronal responses was significantly diminished during ETX, leading to an exaggerated acoustic startle response, which may be a physiological basis for AGS. Previous reports indicate that ethanol enhances the effects of GABA and decreases the effects of glutamate. The PRF neuronal firing increases during EXT in the present study may involve the down-regulation of GABAA receptors and supesensitivity of glutamate receptors reported to occur during ETX, which could contribute to AGS susceptibility. The PRF neuronal firing increases observed in the present study in concord with previous observation of AGS blockade by PRF microinjections during ETX further support an important role of this brain region in the propagation of AGS during ethanol withdrawal.
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PMID:Increased responsiveness of pontine reticular formation neurons associated with audiogenic seizure susceptibility during ethanol withdrawal. 785 Apr 71

The neuropsychological effects of the GABA-reuptake blocker, tiagabine-HCl, were tested in an open trial of 22 adult patients with refractory partial epilepsy followed by a double-blind, placebo-controlled, cross-over trial in 12 subjects. Nineteen patients completed the initial open titration and fixed-dose phase of the study and 11 patients completed the double-blind phase. The median daily tiagabine dose was 32 mg during the open fixed dose and 24 mg during the double-blind periods. Neuropsychological evaluation did not show any significant effect on cognitive function in the open or double-blind phases. In this group of patients no statistically significant difference in the frequency of the total number of seizures or complex partial seizures was found in the open or double-blind stages. Seizure severity was significantly less in the open fixed dose than in the baseline period, but was not significantly different between the two double-blind periods. Reported side effects were transient, most commonly aggression/irritability, lethargy, headache and drowsiness. No significant EEG changes were observed.
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PMID:Neuropsychological effects of tiagabine, a potential new antiepileptic drug. 804 51

This study begins to explore possible mechanisms underlying the role of GABAB receptors in absence seizures in lethargic (lh/lh) mice. To test the hypothesis that alterations intrinsic to the GABAB receptor underlie enhanced synaptic activation of these receptors in absence seizures, we measured GABA-displaceable [3H]baclofen binding to neocortical plasma membranes prepared from lh/lh and wild (+/+) age-matched congenic mice. The number (Bmax) of binding sites was significantly greater (20%) in lh/lh (4.2 pmol/mg protein, n = 43 pairs, P < 0.02) than in +/+ mice (3.3 pmol/mg protein) in an age-independent manner. Interestingly, the subset of lh/lh mice with greater seizure frequency (40-70 seizures/15 min, measured by bipolar electrodes implanted into neocortex; n = 11) had a significantly greater Bmax (P < 0.003) than the subset with lower seizure frequency (1-10 seizures/15 min; n = 11). The equilibrium dissociation constant (Kd) was unchanged (60 nM in both). The Kd of both strains was inhibited to an equal degree by the nonhydrolysable GTP analogue 5'-guanylimido-diphosphate [Gpp(NH)p]. The increased number of GABAB binding sites was selective, because binding to NMDA sites ([3H]glutamate binding) and to GABAA sites ([3H]muscimol binding) was not significantly different in the two strains. These data suggest that the increased number of GABAB receptors in lh/lh mice underlies enhanced synaptic activation of these receptors. Together with evidence that GABAB receptor activation can produce disinhibition, our data support a role for GABAB receptors in the expression of absence seizures in lh/lh mice.
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PMID:Increased number of GABAB receptors in the lethargic (lh/lh) mouse model of absence epilepsy. 838 8

The effects of 5-2500 microM concentrations of neutral ammonium salts on the binding of ligands to components of the GABAA receptor complex were investigated. [3H]Flunitrazepam binding to the benzodiazepine receptor was enhanced by ammonium (10-500 microM), but not sodium tartrate with EC50 = 98 microM and Emax = 31%. Further increasing ammonium tartrate concentrations (500-2500 microM) decreased [3H]flunitrazepam binding to control levels. The ammonium tartrate-induced increase in [3H]flunitrazepam binding was manifested as a 50% decrease in Kd. Furthermore, GABA increased the potency of ammonium tartrate in enhancing [3H]flunitrazepam binding by 63%. [3H]Ro 15-1788 and [3H]Ro 15-4513 binding to the benzodiazepine receptor was not significantly enhanced by ammonium tartrate (Emax approximately 13%). Ammonium tartrate also increased, then decreased the binding of 500 nM [3H]muscimol to the GABAA receptor (EC50 = 52 microM, Emax = 30%) in a concentration-dependent manner, but had no effect on [3H]SR 95-531 binding (Emax < 16%). The ammonium tartrate-induced alterations in [3H]muscimol binding were demonstrated in saturation assays as the loss of the high affinity binding site and a 27% increase in the Bmax of the low affinity binding site. These results indicate that ammonia biphasically enhances, then returns ligand binding to both the GABA and benzodiazepine receptor components of the GABAA receptor complex to control levels in a barbiturate-like fashion. This suggests that ammonia may enhance GABAergic neurotransmission at concentrations commonly encountered in hepatic failure, an event preceding the suppression of inhibitory neuronal function observed at higher (> 1 mM) ammonia concentrations. This increase in GABAergic neurotransmission is consistent with the clinical picture of lethargy, ataxia and cognitive deficits associated with liver failure and congenital hyperammonemia.
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PMID:Modulation of ligand binding to components of the GABAA receptor complex by ammonia: implications for the pathogenesis of hyperammonemic syndromes. 878 94

4-Aminobutyrate aminotransferase (GABA-transaminase, GABA-T, EC 2.6.1.19) deficiency (McKusick 137150), an inborn error of GABA degradation, has until now been documented in only a single Flemish child. Compared to the other defects of GABA degradation, succinic semialdehyde dehydrogenase (SSADH, EC 1.2.1.24) deficiency with > 150 patients (McKusick 271980) and pyridoxine-dependent seizures with > 100 patients ('putative' glutamic acid decarboxylase (GAD, EC 4.1.1.15) deficiency; McKusick 266100), GABA-T deficiency is very rare. We present a summary of the clinical, biochemical, enzymatic and molecular findings on the index proband, and a recently identified second patient, with GABA-T deficiency. The phenotype in both included psychomotor retardation, hypotonia, hyperreflexia, lethargy, refractory seizures and electroencephalographic abnormalities. In an effort to elucidate the molecular basis of GABA-T deficiency, we isolated and characterized a 1.5 kb cDNA encoding human GABA-T, in addition to a 41 kb genomic clone which encompassed the GABA-T coding region. Standard methods of cloning and sequencing revealed an A-to-G transition at nucleotide 754 of the coding region in lymphoblast cDNAs derived from the index proband. This mutation resulted in substitution of an invariant arginine at amino acid 220 by lysine. Expression of the mutant in E. coli, followed by isolation and enzymatic characterization of the recombinant protein, revealed an enzyme whose Vmax was reduced to 25% of wild-type activity. The patient and father were heterozygous for this allele; the second allele in the patient remains unidentified. Genomic Southern analysis revealed that the second proband most likely harbours a deletion in the 3' region of the GABA-T gene.
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PMID:4-Aminobutyrate aminotransferase (GABA-transaminase) deficiency. 1040 78


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