Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ethanol is metabolized in the brain by catalase/H2O2 to yield acetaldehyde and by an ethanol-inducible form of cytochrome P450 (P450 IIE1) in a reaction that yields oxygen radicals. Within the cytoplasm of serotonergic axon terminals these metabolic pathways together provide conditions for the endogenous synthesis of 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline (1), by reaction of acetaldehyde with unbound 5-hydroxytryptamine (5-HT), and for the oxygen radical-mediated oxidation of this alkaloid. The major initial product of the hydroxyl radical (HO.)-mediated oxidation of 1 in the presence of free glutathione (GSH), a constituent of nerve terminals and axons, is 8-S-glutathionyl-1-methyl-1,2,3,4-tetrahydro-beta-carboline-5,6-dione (6). When administered into the brains of mice, 6 is a potent toxin (LD50 = 2.9 microg) and evokes episodes of hyperactivity and tremor. Compound 6 binds at the GABA(B) receptor and evokes elevated release and turnover of several neurotransmitters. Furthermore, the GABA(B) receptor antagonist phaclofen attenuates the behavioral response caused by intracerebral administration of 6. These observations suggest that 6 might be an inverse agonist at the GABA(B) receptor site. Accordingly, it is speculated that ethanol drinking might potentiate formation of 6 that contributes to elevated release of several neurotransmitters including dopamine (DA) and endogenous opioids in regions of the brain innervated by serotonergic axon terminals. Subsequent interactions of DA and opioids with their receptors might be related to the initial development of dependence on ethanol. Redox cycling of 6 (and of several putative secondary metabolites) in the presence of intraneuronal antioxidants and molecular oxygen to produce elevated fluxes of cytotoxic reduced oxygen species might contribute to the degeneration of serotonergic pathways. Low levels of 5-HT in certain brain regions of the rat predisposes these animals to drink or augments drinking. Accordingly, 6, formed as a result of ethanol metabolism in the cytoplasm of certain serotonergic axon terminals, might contribute to the initial development of dependence on ethanol, by mediating DA and opioid release, and long-term preference and addiction to the fluid as a result of the progressive degeneration of these neurons.
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PMID:Putative oxidative metabolites of 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline of potential relevance to the addictive and neurodegenerative consequences of ethanol abuse. 916 Jul 98

The globus pallidus occupies a critical position in the 'indirect' pathway of the basal ganglia and, as such, plays an important role in the modulation of movement. In recent years, the importance of the globus pallidus in the normal and malfunctioned basal ganglia is emerging. However, the function and operation of various transmitter systems in this nucleus are largely unknown. GABA is the major neurotransmitter involved in the globus pallidus. By means of electrophysiological recording, immunohistochemistry and behavioral studies, new information on the distribution and functions of the GABAergic neurotransmission in the rat globus pallidus has been generated. Morphological studies revealed the existence of GABA(A) receptor, including its benzodiazepine binding site, and GABA(B) receptor in globus pallidus. At subcellular level, GABA(A) receptors are located at the postsynaptic sites of symmetric synapses (putative GABAergic synapses). However, GABA(B) receptors are located at both pre- and postsynaptic sites of symmetric, as well as asymmetric synapses (putative excitatory synapses). Consistent with the morphological results, functional studies showed that activation of GABA(B) receptors in globus pallidus reduces the release of GABA and glutamate by activating presynaptic auto- and heteroreceptors, and hyperpolarizes pallidal neurons by activating postsynaptic receptors. In addition to GABA(B) receptor, activation of GABA(A) receptor benzodiazepine binding site and blockade of GABA uptake change the activity of globus pallidus by prolonging the duration of GABA current. In agreement with the in vitro effect, activation of GABA(B) receptor, GABA(A) receptor benzodiazepine binding site and blockade of GABA uptake cause rotation in behaving animal. Furthermore, the GABA system in the globus pallidus is involved in the etiology of Parkinson's disease and regulation of seizures threshold. It has been demonstrated that the abnormal hypoactivity and synchronized rhythmic discharge of globus pallidus neurons associate with akinesia and resting tremor in parkinsonism. Recent electrophysiological and behavioral studies indicated that the new anti-epileptic drug, tiagabine, is functional in globus pallidus, which may present more information to understand the involvement of globus pallidus in epilepsy.
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PMID:GABAergic neurotransmission in globus pallidus and its involvement in neurologic disorders. 1532 74

Harmaline-induced tremor in rodents is a model of essential tremor. We utilized a novel assay to quantify tremor activity in mice and found that tremor activity was dependent on harmaline dose. The first-line clinical essential tremor treatments propranolol, primidone and gabapentin and gamma-hydroxybutyrate (GHB) significantly attenuated harmaline-induced tremor. The anticonvulsants valproate and carbamazepine and the mood stabilizer lithium suppressed harmaline-induced tremor. The gamma-amino-butyric acid (GABA) receptor subtype A receptor agonist muscimol attenuated harmaline-induced tremor. By contrast, the GABA(B) receptor agonist R-baclofen increased tremor at the lowest dose tested, but had no effects at higher doses. Administration of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists phencyclidine or 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine hydrogen maleate (MK-801) attenuated harmaline-induced tremor. The competitive NMDA antagonist D-4-[(2E)-3-phosphono-2-propenyl]-2-piperazinecarboxylic acid (d-CPPene) dose-dependently blocked harmaline-induced tremor, as did the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium salt (NBQX). The metabotropic glutamate subtype 5 (mGlu5) receptor antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP) was inactive against tremor. The dopamine reuptake inhibitor GBR12909 and the dopamine D(1)/D(2) receptor agonist apomorphine attenuated harmaline-induced tremor. Follow-up studies indicated that dopamine D(2)/D(3) but not dopamine D(1) receptor activation likely mediates the effects of apomorphine and GBR12909. Administration of compounds with sedative side-effects had no effect on tremor activity. In summary, the present data confirm the pharmacological validity of harmaline-induced tremor in mice, quantified via a novel assay, as an animal model of essential tremor. Further, these data provide additional evidence for the roles of ionotropic glutamate, GABA(A) and dopamine D(2)/D(3) receptors in the neurobiology of harmaline-induced tremor.
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PMID:Pharmacological characterization of harmaline-induced tremor activity in mice. 1949 22