Sonoko Danjo

The threshold of pentylenetetrazole-induced convulsive seizures, but not that of nonconvulsive seizures, is controlled by the nitric oxide levels in murine brains.

Alterations in the NO pathway play an important role in the development of convulsive seizures via the glutamatergic and GABAergic systems in acute pentylenetetrazole (PTZ) seizure animals. We previously reported that the background NO levels under physiological conditions negatively regulate convulsive seizures, while excess NO levels under pathologic conditions positively regulate PTZ-induced convulsive seizures. In this study, the NO content in various brain regions after a single dose injection of PTZ was quantitatively and directly measured using the ex vivo X-band electron paramagnetic resonance method with an NO-trapping agent. Experimental data demonstrated the effects of NO on the convulsive seizure threshold: a 1.5-fold increase in the NO level in all brain regions compared to that observed in the control state showed proconvulsive properties without any involvement with nonconvulsive seizures. The distribution of the background NO content in the normal animals was higher in the temporal region of the cerebral cortex, including the amygdala, than in the hippocampus, cerebellum and other regions of the cerebral cortex. However, the levels of NO after the occurrence of acute PTZ-induced convulsive seizures significantly increased by more than 50% in all brain regions, thus suggesting that the NO levels in all brain regions contribute to PTZ-induced convulsions as a seizure threshold. In a pharmacological study, the inhibitor of neuronal NO synthase and antagonists of ionotropic glutamate receptors prevented PTZ-induced convulsions and excessive NO generation. In addition, therapeutic drugs, such as valproate and ethosuximide used to treat generalized seizures not only inhibited the increase in NO generation induced by PTZ, but also prevented both convulsive and nonconvulsive seizures caused by PTZ. We herein provide novel insight into the involvement of NO in PTZ-seizure susceptibility at the whole-animal level.

Pentylentetrazole-induced loss of blood–brain barrier integrity involves excess nitric oxide generation by neuronal nitric oxide synthase

Dysfunction of the blood-brain barrier (BBB) is one of the major pathophysiological consequences of epilepsy. The increase in the permeability caused by BBB failure is thought to contribute to the development of epileptic outcomes. We developed a method by which the BBB permeability can be demonstrated by gadolinium-enhanced T1 weighted imaging (GdET1WI). The present study examined the changes in the BBB permeability in mice with generalized convulsive seizures (GCS) induced by acute pentylentetrazole (PTZ) injection. At 15min after PTZ-induced GCS, the BBB temporarily leaks BBB-impermeable contrast agent into the parenchyma of the diencephalon, hippocampus and cerebral cortex in mice, and the loss of BBB integrity was gradually recovered by 24h. The temporary BBB failure is a critical link to the glutamatergic activities that occur following the injection of PTZ. PTZ activates the glutamatergic pathway via the NMDA receptor, then nitric oxide (NO) is generated by NMDA receptor-coupled neuronal NO synthase (nNOS). To examine the influence of nNOS-derived NO induced by PTZ on the increases of the BBB permeability, GdET1WI was performed using conventional nNOS gene-deficient mice with or without PTZ injection. The failure of the BBB induced by PTZ was completely protected by nNOS deficiency in the brain. These results suggest that nNOS-derived excess NO in the glutamatergic pathway plays a key role in the failure of the BBB during PTZ-induced GCS. The levels of NO synthetized by nNOS in the brain may represent an important target for the future development of drugs to protect the BBB.

Effect of levothyroxine on prolonged nocturnal sleep time and excessive daytime somnolence in patients with idiopathic hypersomnia

OBJECTIVE This study aims to examine the effect of levothyroxine, a thyroid hormone, on a prolonged nocturnal sleep and excessive daytime somnolence (EDS) in patients with idiopathic hypersomnia. METHODS In a prospective, open-label study, nine patients were enrolled. All subjects met criteria for idiopathic hypersomnia with long sleep time defined by the International Classification of Sleep Disorders, 2nd edition (ICSD-2). Subjects with sleep apnea syndrome, obesity or hypothyroidism were excluded. Sleep architecture and subjective daytime somnolence were estimated by polysomnography (PSG) and Epworth Sleepiness Scale (ESS), respectively. After baseline examinations, levothyroxine (25μg/day) was orally administered every day. Mean total sleep time, ESS score at baseline were compared with those after treatment (2, 4 and 8 weeks). RESULTS Mean age of participants was 23.8±13.7 years old. At baseline, mean total sleep time (hours) and ESS score were 12.9±0.3 and 17.8±1.4, respectively. Mean total sleep times after treatment were 9.1±0.7 and 8.5±1.0h at 4 and 8 treatment weeks, respectively. Mean ESS scores were 8.8±2.3 and 7.4±2.8 at 4 and 8 treatment weeks, respectively. One patient dropped out at the 2nd week due to poor effect. No adverse effects were noted. CONCLUSIONS After treatment with levothyroxine for over 4 weeks, prolonged sleep time and EDS were improved. Levothyroxine was effective for hypersomnia and well tolerated.

Efficacy of a new microvibration sensation measurement device at detecting diabetic peripheral neuropathy using a newly devised finger method

To investigate the efficacy of the finger method using a new microvibration sensation measurement device in the evaluation of diabetic peripheral neuropathy (DPN). A cross‐sectional study of 52 type 2 diabetic outpatients was performed. Patients were evaluated for DPN using American Diabetes Association (ADA) criteria, Michigan Neuropathy Screening Instrument, and the finger method. Patients were classified into probable DPN or non‐DPN groups, according to ADA criteria. The finger method measured peripheral neuropathy vibration (PNV) score of index and middle fingers using the new device in three procedures: PNV 1, PNV 4, and PNV 8. PNV scores ranged from 1 to 30 and were compared between the two groups. The PNV scores were significantly higher in the DPN group (P < .01). The PNV scores for right fingers of DPN and non‐DPN groups were 10.2 ± 7.4 and 3.4 ± 3.3 by PNV 1, 20 ± 4.9 and 10.7 ± 5.3 by PNV 4, and 23.2 ± 4.9 and 14.6 ± 7.8 by PNV 8. Our data suggest that the finger method performed with the new device is useful in the evaluation of DPN.