Ruei-Feng Chen

Dynamic changes of touch- and laser heat-evoked field potentials of primary somatosensory cortex in awake and pentobarbital-anesthetized rats

In this investigation, changes of mechanical- (MEP) and laser-evoked potentials (LEP) in rat primary somatosensory cortex during the course of pentobarbital (PB) anesthesia were examined. Temporal analysis of changes in the magnitude and latency of MEP and LEP, EEG activity, gross motor behaviors, and the tail flick response following laser stimulation before, during, and after PB administration (50 mg/kg, i.p.) was performed and correlated in chronically implanted rats. During the wakeful condition, there were two major cortical components each following mechanical stimulation (MEP1 and MEP2, n=17) and laser stimulation (LEP1 and LEP2, n=10), respectively. After PB administration, the positive peak in MEP1 was enhanced, and all other components disappeared. These components returned with different time courses. Two hours after PB administration, when the rat had spontaneous movements and flexor reflexes, LEP2 showed reversed polarity. MEP2 returned gradually 3 h after PB administration when the rat regained its ability to execute coordinated movements. After 4 h, LEP1 began to reappear and LEP2 returned to its negative polarity. We found that PB facilitated Abeta fiber-related cortical evoked potential (MEP1), while differentially inhibited Adelta and C fiber-related components (MEP2, LEP1 and LEP2). Characterization of these anesthesia-induced changes in cortical output may be useful in studying the neural basis of tactile and pain sensations.

Comparison of touch- and laser heat-evoked cortical field potentials in conscious rats

Field potentials and multiunit activities from chronically implanted cortical electrodes were used to study tactile and nociceptive information processing from the tail of the rat. Fourteen stainless steel screws implanted in the skull were used as electrodes to record field potentials in different cortical areas. Electrical, mechanical, and laser pulses were applied to the tail to induce evoked cortical field potentials. Evoked responses were compared before and after sodium pentobarbital anesthesia (50 mg/kg, i.p.). In both electrical- and mechanical-evoked potential (EEP and MEP) studies, two major peaks were found in the conscious animal. The polarity of the late component was modified after pentobarbital anesthesia. In the laser-evoked potential (LEP) study, two distinct negative peaks were found. Both peaks were very sensitive to anesthesia. Following quantitative analysis, our data suggest that the first positive peak of EEP and MEP corresponded to the activation of the Abeta fiber, the second negative peak of MEP and the first peak of LEP corresponded to Adelta fiber activation, while the second peak of LEP corresponded to C fiber activation. The absolute magnitudes of all cortical components were positively related to the intensity of the stimulation. From spatial mapping analysis, a localized concentric source of field potential was observed in the primary somatosensory cortex (SI) only after activation of the Abeta fiber. Larger responsive cortical areas were found in response to Adelta and C fiber activation. In an intracortical recording experiment, both tactile and nociceptive stimulation evoked heightened unit activity changes at latencies corresponding to respective field potentials. We conclude that different cortical areas are involved in the processing of A and C fiber afferent inputs, and barbiturate anesthesia modifies their processing.

A multichannel system for recording and analysis of cortical field potentials in freely moving rats

A system has been developed to record and analyze the cortical electrical activity from 16 different sites in freely moving rats. The hardware includes a 16-channel amplifier system whose high input impedance, low noise, small size, light weight and shielded multistrand connecting cable allow high quality multichannel recording of field potentials. The software developed for this system consists of data acquisition, data analysis and topographic mapping of cortical-evoked potentials as well as electroencephalograms. Cortical field potentials evoked by CO2-laser stimulation were compared between wakeful and pentobarbital-treated conditions. To investigate the background interference produced by sleep spindle, three kinds of reference-free methods (the Wilson, local average and weighted average methods) were utilized to compare the coherence between field potentials obtained from two cerebral hemispheres using monopolar vs. reference-free recordings.

α‐Phenyl‐n‐tert‐butyl‐nitrone attenuates lipopolysaccharide‐induced brain injury and improves neurological reflexes and early sensorimotor behavioral performance in juvenile rats

Our previous study showed that treatment with α‐phenyl‐n‐tert‐butyl‐nitrone (PBN) after exposure to lipopolysaccharide (LPS) reduced LPS‐induced white matter injury in the neonatal rat brain. The object of the current study was to further examine whether PBN has long‐lasting protective effects and ameliorates LPS‐induced neurological dysfunction. Intracerebral (i.c.) injection of LPS (1 mg/kg) was performed in postnatal day (P) 5 Sprague Dawley rat pups and PBN (100 mg/kg) or saline was administered intraperitoneally 5 min after LPS injection. The control rats were injected (i.c.) with sterile saline. Neurobehavioral tests were carried out from P3 to P21, and brain injury was examined after these tests. LPS exposure resulted in severe brain damage, including enlargement of ventricles bilaterally, loss of mature oligodendrocytes, impaired myelination as indicated by the decrease in myelin basic protein immunostaining, and alterations in dendritic processes in the cortical gray matter of the parietal cortex. Electron microscopic examination showed that LPS exposure caused impaired myelination as indicated by the disintegrated myelin sheaths in the juvenile rat brain. LPS administration also significantly affected neurobehavioral functions such as performance in righting reflex, wire hanging maneuver, cliff avoidance, negative geotaxis, vibrissa‐elicited forelimb‐placing test, beam walking, and gait test. Treatment with PBN, a free radical scavenger and antioxidant, provided protection against LPS‐induced brain injury and associated neurological dysfunction in juvenile rats, suggesting that antioxidation might be an effective approach for therapeutic treatment of neonatal brain injury induced by infection/inflammation.

Protective Effect of Caffeic Acid on Paclitaxel Induced Anti-Proliferation and Apoptosis of Lung Cancer Cells Involves NF-κB Pathway

Caffeic acid (CA), a natural phenolic compound, is abundant in medicinal plants. CA possesses multiple biological effects such as anti-bacterial and anti-cancer growth. CA was also reported to induce fore stomach and kidney tumors in a mouse model. Here we used two human lung cancer cell lines, A549 and H1299, to clarify the role of CA in cancer cell proliferation. The growth assay showed that CA moderately promoted the proliferation of the lung cancer cells. Furthermore, pre-treatment of CA rescues the proliferation inhibition induced by a sub-IC50 dose of paclitaxel (PTX), an anticancer drug. Western blot showed that CA up-regulated the pro-survival proteins survivin and Bcl-2, the down-stream targets of NF-κB. This is consistent with the observation that CA induced nuclear translocation of NF-κB p65. Our study suggested that the pro-survival effect of CA on PTX-treated lung cancer cells is mediated through a NF-κB signaling pathway. This may provide mechanistic insights into the chemoresistance of cancer calls.

Algorithmic complexity as an index of cortical function in awake and pentobarbital-anesthetized rats

This study introduces algorithmic complexity to measure characteristics of brain functions. The EEG of the rat was recorded with implanted electrodes. The normalized complexity value was relatively independent of data length, and it showed a simpler and easier calculation characteristic than other non-linear indexes. The complexity index revealed significant differences among awake, asleep, and anesthetized states. It may be useful in tracking short-term and long-term changes in brain functions, such as anesthetized depth, drug effects, or sleep-wakefulness.

Intracellular zinc release-activated ERK-dependent GSK-3β–p53 and Noxa–Mcl-1 signaling are both involved in cardiac ischemic-reperfusion injury.

Oxidative stress and nitrosative stress are both suggested to be involved in cardiac ischemia-reperfusion (I/R) injury. Using time-lapse confocal microscopy of cardiomyocytes and high-affinity O2−• and Zn2+ probes, this study is the first to show that I/R, reactive oxygen species (ROS), and reactive nitrogen species (RNS) all cause a marked increase in the [O2−•]i, resulting in cytosolic and mitochondrial Zn2+ release. Exposure to a cell-penetrating, high-affinity Zn2+i chelator, TPEN, largely abolished the Zn2+i release and markedly protected myocytes from I/R-, ROS-, RNS-, or Zn2+/K+ (Zn2+i supplementation)-induced myocyte apoptosis for at least 24 h after TPEN removal. Flavonoids and U0126 (a MEK1/2 inhibitor) largely inhibited the myocyte apoptosis and the TPEN-sensitive I/R- or Zn2+i supplement-induced persistent extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, dephosphorylation of p-Ser9 on glycogen synthase kinase 3β (GSK-3β), and the translocation into and accumulation of p-Tyr216 GSK-3β and p53 in, the nucleus. Silencing of GSK-3β or p53 expression was cardioprotective, indicating that activation of the ERK–GSK-3β–p53 signaling pathway is involved in Zn2+-sensitive myocyte death. Moreover, the ERK-dependent Noxa–myeloid cell leukemia-1 (Mcl-1) pathway is also involved, as silencing of Noxa expression was cardioprotective and U0126 abolished both the increase in Noxa expression and in Mcl-1 degradation. Thus, acute upstream Zn2+i chelation at the start of reperfusion and the use of natural products, that is, flavonoids, may be beneficial in the treatment of cardiac I/R injury.

Distribution of large terminal inputs from the primary and secondary somatosensory cortices to the dorsal thalamus in the rodent

The present study was undertaken to determine the precise projection pattern from the primary (S1) and secondary (S2) somatosensory cortices to the posterior nuclear proper (POm) and ventroposterior thalamic nuclei (VP). The POm was previously shown to receive large boutons arising exclusively from layer V of the S1 barrel region. This descending input was proposed to play a key role, namely, as a driver, in shaping the receptive property of POm neurons. To determine whether other body parts and the S2 also contribute such unique inputs to the dorsal thalamus, anterograde neuroanatomical tracers were focally deposited in the S1 and S2 forepaw and whisker regions of rats and C57BL6‐Tg (GFPm)/Thy1 transgenic mice. Our major findings were that, 1) irrespective of body representations, both the S1 and the S2 provided corticothalamic large terminals to the POm with comparable morphological characteristics and 2) descending large terminals were also noted in particular subzones within the VP, including boundary and caudal areas. We concluded, based on these findings, that the rodent VP has three partitions: the rostral VP innervated by small corticothalamic terminals, the caudal VP with both corticothalamic small and large terminals, and a surrounding shell region, which also contained large terminals. Furthermore, assuming that the large terminal has a drivers role, we propose that particular subzones in the VP may play a role as a multiple‐order thalamic relay so that they can simultaneously coordinate with first‐ and higher‐order relays in the thalamocortical circuitry for processing somatosensory information. J. Comp. Neurol. 518:2592–2611, 2010.

A simple and effective process for noise reduction of multichannel cortical field potential recordings in freely moving rats

Simple and useful steps, i.e. placing a grounded plate under the recording chamber as well as using multiple reference electrodes, are introduced here for obtaining reliable low-noise recordings of brain activity in freely moving rats. A general circuit model was built to analyze the electrical interference of both single-grounded and two-reference ground-free recording configurations. In both simulated and realistic conditions under two recording states, 60-Hz magnitude was in the microvolt range. Moreover, the noise was significantly reduced by shortening the distance between the subject and the grounded plate under the recording chamber. Furthermore, in chronically implanted rats, average 60-Hz interference of multichannel electroencephalograms of two-reference ground-free recordings (3.74 +/- 0.18 microV) was significantly smaller than that of the single-grounded condition (9.03 +/- 1.98 microV). Thus, we demonstrated that a lower-noise recording can be achieved by a two-reference configuration and a closely-placed metal grounded plate in an open-field circumstance. As compared to the use of a Faraday cage, this simple procedure is of benefit for long-term behavioral tracking with a video camera and for pharmacological experiments.

Blood vessel epicardial substance (BVES) regulates epidermal tight junction integrity through atypical protein kinase C

Background: The regulatory mechanisms of Bves in tight junction integrity is not fully understood. Results: Both aPKC and Bves are indispensable for claudin expression in cell membrane of zebrafish keratinocytes. Conclusion: Bves works in coordination with aPKC to regulate claudin formation and stability. Significance: Bves may play an important role in regulating tight junction integrity through aPKC. Bves is widely observed in the cell junction of the skin, epicardium, intestine, and cornea of both developmental embryos and mature adults. However, it is not clear how Bves confers its role in intercellular adhesion. Here, we identified the zebrafish bves (zBves) and found that the epidermal barrier function could be disrupted after knockdown of Bves, and these zBves morphants were sensitive to osmotic stress. A loss of zBves would affect the partitioning defective protein (PAR) junctional complex identified by the rescue experiment with tjp-2/ZO-2 or the PAR complex (par-3, par-6, and prkci/atypical (a)PKC) mRNAs, in which the survival rate of embryos increased 11, 24, 25, and 28%, respectively, after injection with junctional components; the tjp-2 and aPKC mRNA-rescued embryos also had 24 and 45% decreases in the defective rate. Immunofluorescent studies demonstrated that the aggregation of aPKC around the cell junctions had disintegrated in zBves morphants. However, the expression and assembly of zBves were not influenced by aPKC-MO. These results indicate that a loss of zBves affects the proteins involved in the pathway of the PAR junctional complex, especially aPKC, and both aPKC and Bves are indispensable to claudin expression.