Graves' disease (GD) is an autoimmune disorder with genetic predisposition. IL-13 is an important mediator of antiinflammatory immune responses and is expressed in the thyroid and orbit. The aim of the present study was to investigate whether IL-13 gene polymorphisms are associated with the development of GD. IL-13 gene polymorphisms were studied in Japanese GD patients (n = 310) and healthy control subjects without antithyroid autoantibodies or a family history of autoimmune disorders (n = 244). A C/T polymorphism at position -1112 of the promoter region was measured using the direct sequencing method, and an Arg(130)Gln (G2044A) polymorphism in exon 4 was examined using the PCR-restriction fragment length polymorphism method. There was a significant decrease in -1112T allele frequency in GD patients compared with controls (16% vs. 23%; P = 0.0019). The frequency of the 2044A allele on exon 4 also appeared lower in GD patients compared with controls. Haplotype analysis showed a significant decrease in the -1112T/2044A haplotype in GD patients. There was no association between IL-13 gene polymorphisms and ophthalmopathy, severity, or serum IgE levels. In conclusion, IL-13 gene polymorphisms are associated with GD susceptibility in Japan.

Catechol-O-methyltransferase (COMT) is an enzyme that inactivates catecholamines, including levodopa. An amino acid change (Val-108-Met) in the COMT protein has been found to result in a change from high to low enzyme activity. In the present study, we genotyped 121 Japanese patients with Parkinson’s disease (PD) and 100 controls. Comparison of the allele frequencies revealed that homozygosity for the low-activity allele was significantly more common among PD patients than the controls (p = 0.047, odds ratio = 3.23). In addition, homozygosity for the low-activity allele was overrepresented in PD patients that exhibited the ‘wearing-off’ phenomenon (p = 0.045, odds ratio = 3.82) or dyskinesia (p = 0.030, odds ratio = 4.80) compared with controls, although these differences were not significant after Bonferroni’s correction. Our results may help understand the mechanism that cause complications of levodopa therapy in PD patients.

Intracellular and voltage-clamp studies were carried out to clarify the mechanism for spontaneous firing activity in neurons of the suprachiasmatic nucleus (SCN) of rat hypothalamic brain slices in vitro. SCN neurons displayed spontaneously firing action potentials that were preceded by a depolarizing pre-potential and followed by a short spike after-hyperpolarization (AHP). Injection of inward current with a duration longer than 50 ms resulted in a depolarizing voltage "sag" on hyperpolarizing electrotonic potentials. The inward rectification was depressed by bath application of caesium (1 mM) but not by barium (500 microM). SCN neurons also showed a rebound depolarization associated with spike discharge (anodal break) in response to relaxation of hyper polarizing current injection. The rebound depolarization was reduced by nominally zero calcium. Cadmium (500 microM), cobalt (1 mM) or caesium (1 mM) but not nicardipine also depressed the rebound depolarization. Under voltage-clamp conditions, hyperpolarizing steps to membrane potentials negative to approximately -60 mV caused an inward rectifier current, probably H current (IH), which showed no inactivation with time. Bath application of caesium (1-2 mM) suppressed IH. Caesium (2 mM) depressed the slope of the depolarizing spike pre-potential, resulting in a prolongation of the interspike interval of tonic firing neurons. We conclude that both the inward rectifier current, IH, and the low-threshold calcium current contribute to the spike prepotential of spontaneous action potentials in firing neurons of the rat SCN.

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Intracellular recordings were made from neurons in the dorsolateral septal nucleus (DLSN) of rat brain slices. Lowering the concentration of extracellular glucose resulted in a concentration-dependent membrane hyperpolarization associated with a cessation of spontaneous firing. The amplitude of the excitatory postsynaptic potential (EPSP), inhibitory postsynaptic potential (IPSP), and late hyperpolarizing potential (LHP) evoked by a single stimulus applied to the fimbrial/fornix pathway was decreased when the concentration of glucose was reduced to 0-2 mM. Substitution of glucose with 2-deoxy-D-glucose (11 mM), an antimetabolite of glucose substrate, mimicked the effects of glucose depletion. Mannoheptulose (10-20 mM), a potent hexokinase blocker, and dinitrophenol (50 microM), a potent inhibitor of oxidative phosphorylation, produced both the hyperpolarization and inhibition of postsynaptic potentials, even in the presence of 11 mM glucose. The sulphonylureas, glibenclamide (10 microM) and tolbutamide (1 mM), did not antagonize the hyperpolarization and the inhibition of the postsynaptic potentials produced by glucose depletion. The amplitude of membrane depolarizations produced by pressure application of glutamate (10 mM) and the membrane hyperpolarizations produced by pressure application of either muscimol (1 mM) or baclofen (1 mM) were almost unchanged, even when glucose was reduced to 1-2 mM. These results indicate that intracellular glucose metabolism regulates the function of septal neurons, not only by changing the resting membrane potential, but also by presynaptically affecting neurotransmission between the hippocampal formation and the lateral septum.