Nahoko Kasai

In vivo analysis of hydrogen peroxide and lipid radicals in the striatum of rats under long-term administration of a neuroleptic.

It has been hypothesized that free radicals play a causative role in tardive dyskinesia, which is an inveterate movement disorder caused by chronic administration of neuroleptics. To verify this hypothesis, rats were reared while being regularly treated with water containing a neuroleptic, haloperidol (HPD), for 1 year (HPD group). The changes in the striatal hydrogen peroxide content of the rats in the HPD and control groups were measured by using a Pt-disk microelectrode while the animals were in a freely moving state following intraperitoneal administration of HPD (HPD challenge). We also performed electron spin resonance (ESR) detection of lipid radicals in the striatum before the HPD challenge. HPD challenge led to significant elevation of the intrastriatal hydrogen peroxide in all animals, but the elevation in the HPD group was smaller than that in the control group. However, in the HPD group, marked ESR signals of intrastriatal lipid radicals were observed. We think that these results support the hypothesis on the role of free radicals in tardive dyskinesia.

Discrimination of odorants of definite concentrations by using plasma-organic-film-coated QCR sensors

Abstract Odorant-discrimination experiments were conducted for the major single-odor substances in various types of botanical species such as fruits and flowers by using a gas-sensing system consisting of a sensor array of quartz crystal resonators (QCRs) and a pattern-recognition technique. The sensing devices were fabricated by radio-frequency sputtering of biomaterials or polymers on to the QCRs. The 22 tested odorants of definite concentration, 0.1–64 ppm, were well discriminated by principal component analysis, using the sensors steady-state and dynamic properties as parameters. From the 1-nearest-neighbor method, introduced to evaluate the discrimination capability, the best discrimination was obtained, using the frequency changes in QCRs for longer than 10 min and the time constant of adsorption at 5 min as parameters, with the success rate of 83%. This system is thus highly reliable for discriminating trace amounts of odorants.

Odorant detection capability of QCR sensors coated with plasma deposited organic films

Odorant-detection experiments were conducted on major single-odor substances in various types of botanical species. The sensing devices we used were quartz-crystal resonators (QCRs), radio-frequency (RF) sputtered with amino acids or polymers. The odorants were generated at very low concentrations (ppb level) by using the diffusion-tube method. The tested odorants were detected at concentrations between 0.3 and 940 ppb. These deposited films had high partition coefficients for the odorants, confirming their high sensitivity to organic vapors, especially to terpenoids. This indicates that the odorant solvation is due to odorant-film interaction related to Gibbs free energy.

Hydrogen peroxide augmentation in a rat striatum after methamphetamine injection as monitored in vivo by a Pt-disk microelectrode.

We fabricated a Pt-disk microelectrode (diameter 30 microns) to conduct differential double-pulse amperometry (first step: 750 mV, 1 s; second step: 1,100 mV, 1 s) to detect hydrogen peroxide in the brain of a freely moving animal. This measurement determined hydrogen peroxide (detection limit, 0.03 microM) without any observable influence from other oxidizable species, such as dopamine (DA), ascorbic acid, or uric acid. The electrode was implanted into the right striatum of a rat. After intraperitoneal injection of methamphetamine (MAP), hydrogen peroxide concentrations were directly detected while the behavioral changes were monitored. MAP injection led to significant augmentation of hydrogen peroxide, the elevation of which depended on the dose of MAP. This is consistent with a previous report on the increase of DA-release caused by amphetamines and indirect evidence of the production of hydrogen peroxide via DA-metabolism.

Effects of aging on radiofrequency-sputtered polyethylene film

The effects of aging on polyethylene film deposited by radiofrequency sputtering on a quartz crystal microbalance were examined by measuring its resonance frequency and conductance, and by measuring the contact angle of the film to distilled water. The film sputtering was observed using in situ optical emission spectroscopy. The fabricated film was observed using atomic force microscopy, and analyzed using Fourier transform-infrared and electron spin-resonance spectroscopies. The longer the film was exposed to air, its weight increased and the film became softer. Increase in hydrophilicity of the surface, decrease in spin concentration in the film, and enrichment of the oxygenated moieties in the film were observed. These indicate that the film structure is reconstructed by the reactions between radical sites in the film and reactive species in the air, such as oxygen and water, and by the movement of hydrophilic moieties inside the film towards the surface. When stored in vacuum, the film hardened and oxidation slowered.

Increase of central nitric oxide during pentylenetetrazol-induced seizures in rats

This agrees with previous report^.^-^ However, recent time-based analysis of changes in extracellular GABA concentration during seizures was not conclusive. Our result strongly suggests that the change in extracellular GABA concentration is not a time-dependent but a state-dependent phenomenon.6 An interesting finding in our study was the drastic decrement of the extracellular GABA concentration compared to the glutamate concentration during the transitional phase before secondary generalization. It is thought that extracellular GABA acts as an inhibitory neurotransmitter. If this is true, the relative decrement of extracellular GABA compared to glutamate in the hippocampus contributes to seizure propagation through the hippocampus to the other brain structures and causes secondary generalized seizures as a result of disinhibition of the hippocampal neurons.