Intravenous mannitol (IV-M) is widely administered in the clinic to lower intracranial pressure in patients with brain trauma and stroke. However, intracarotid arterial mannitol (ICA-M) is known to potently open the blood-brain barrier (BBB) to serum protein tracers such as the Evans blue dye (EBD). In this study, we aimed to determine the potential effect of IV-M on BBB permeability to EBD and a small molecular tracer sodium fluorescein dye (NaF). Rats received intravenous EBD/NaF injections, and after a 30-min equilibration time, they received mannitol (20%, 0.5 g/kg) through either route of administration. At 90 min after the mannitol injection, the rats were perfused to rid their circulations of the tracers, and the tracers extravasated into the brain parenchyma were measured by photospectrometry. As expected, ICA-M considerably increased EBD extravasation into the rat forebrain regions, including the motor cortex (P=0.0069), the striatum (P=0.0097), and the hippocampus (P=0.0281; student's t-test). In marked contrast, IV-M exerted no effect on EBD extravasation into these forebrain regions. To increase the power of the IV-M study, we repeated the experiments in two independent trials of experiments (n=6-9/group/trial) and found the same result. Finally, consistent with no effect on EBD extravasation, IV-M had no effect on NaF extravasation into the rat forebrain. In conclusion, we report direct evidence that IV-M, at a dose used clinically, in contrast to the same dose of ICA-M, exerted no effect on BBB permeability to protein and small molecular tracers.

The development of the blood-brain barrier (BBB) against permeability to inert tracers, such as Evans blue dye (EBD), occurs quite early on at embryonic stages (before E13-E15), and the BBB remains resistant to EBD between E15 and early adulthood (P20-P30). Here, we aimed to examine the changes in EBD permeability at a later stage in development, specifically comparing young rats (P20) with adult rats (P86). We found markedly higher EBD extravasation into the forebrains of adult rats compared with those of the young rats (P=0.0132; Student's t-test). In contrast, there was no difference in EBD extravasation to the liver, suggesting no change in vascular permeability in peripheral tissues. Furthermore, EBD extravasation into the cerebellum was less prominent than that into the forebrain, suggesting that the disruption of the BBB was brain-region specific. In conclusion, we found a specific increase in EBD extravasation in the mature forebrain, and the protocol that we used may be a good template for studying developmental disruption of the BBB.

ObjectiveA variety of ion channels have been implicated in breast cancer proliferation and metastasis. Voltage-gated K+ (Kv) channels not only cause repolarization in excitable cells, but are also involved in multiple cellular functions in non-excitable cells. In this study we investigated the role of Kv channels in migration of BT474 breast cancer cells. MethodsTranswell technique was used to separate migratory cells from non-migratory ones and these two groups of cells were subject to electrophysiological examinations and microfluorimetric measurements for cytosolic Ca2+. Cell migration was examined in the absence or presence of Kv channel blockers. ResultsWhen compared with non-migratory cells, migratory cells had much higher Kv current densities, but rather unexpectedly, more depolarized membrane potential and reduced Ca2+ influx. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of Kv1.1, Kv1.3, Kv1.5, Kv2.1, Kv3.3, Kv3.4 and Kv4.3 channels. Cell migration was markedly inhibited by tetraethylammonium (TEA), a delayed rectifier Kv channel blocker, but not by 4-aminopyridine, an A-type Kv channel blocker. ConclusionsTaken together, our results show that increased Kv channel expression played a role in BT474 cell migration, and Kv channels could be considered as biomarkers or potential therapeutic targets for breast cancer metastasis. The mechanism(s) by which Kv channels enhanced migration appeared unrelated to membrane hyperpolarization and Ca2+ influx.

Abstract:Background: Although diphenidol has long been deployed as an anti-emetic and anti-vertigo drug, its mechanism of action remains unclear. In particular, little is known as to how diphenidol affects neuronal ion channels. Recently, we showed that diphenidol blocked neuronal voltage-gated Na + channels, causing spinal blockade of motor function, proprioception and nociception in rats. In this work, we investigated whether diphenidol could also affect voltage-gated K + and Ca 2+ channels. Methods: Electrophysiological experiments were performed to study ion channel activities in two neuronal cell lines, namely, neuroblastoma N2A cells and differentiated NG108-15 cells. Results: Diphenidol inhibited voltage-gated K + channels and Ca 2+ channels, but did not affect store-operated Ca 2+ channels. Conclusion: Diphenidol is a non-specific inhibitor of voltage-gated ion channels in neuronal cells.