Biomedical subjects

Fu-Zen Shaw

Publications and source records attributed to Fu-Zen Shaw.

15 recordsLinked to original sources

PubMed2006

Effects of rosiglitazone on global ischemia-induced hippocampal injury and expression of mitochondrial uncoupling protein 2.

We investigate the effect of rosiglitazone, a ligand for peroxisome proliferator-activated receptor-gamma (PPARgamma) with anti-inflammatory and anti-oxidative actions, on hippocampal injury and its roles in mitochondrial uncoupling protein 2 (UCP2) expression caused by transient global ischemia (TGI) in rats. Increased UCP2 expression was observed in mitochondria of hippocampal CA1 2-24h after TGI/reperfusion, with maximal expression levels at 6-18h. Administration of rosiglitazone to hippocampus 30min prior to the onset of TGI further enhanced mitochondrial UCP2 expression 2-6h following TGI/reperfusion. Rats subjected to TGI/reperfusion displayed a significant increase in lipid peroxidation, based on increased malondialdehyde (MDA) levels, in hippocampal CA1 mitochondria 2-6 h after reperfusion. Rosiglitazone significantly attenuated TGI/reperfusion-induced lipid peroxidation and suppressed hippocampal CA1 neuronal death based on the surviving neuronal counts. In conclusion, our results provide correlative evidence for the "PPARgamma-->UCP2-->neuroprotection" cascade in ischemic brain injury.

Animals↗

PubMed2006

7-12 Hz high-voltage rhythmic spike discharges in rats evaluated by antiepileptic drugs and flicker stimulation.

Paroxysmal 7- to 12-Hz high-voltage rhythmic spike (HVRS) or spike-wave discharges often appear in several particular strains of rats. However, functional hypotheses of these 7-12 Hz high-voltage cortical oscillations (absence seizure vs. idling mu rhythm) are inconclusive. The mu rhythm can be provoked by flicker stimulation (FS) in most people, but FS is less effective at eliciting absence epileptic activity. Therefore FS and antiepileptic drugs were used to verify the role of HVRS activity in Long-Evans rats with spontaneous HVRS discharges and Wistar rats without spontaneous HVRS discharges. The occurrence of HVRS discharges was significantly reduced by antiabsence drugs (ethosuximide, valproic acid, and diazepam) in dose-dependent manners, but high-dose carbamazepine displayed little effect. On the other hand, oscillation frequencies and durations of spontaneous HVRS discharges were not altered by FS. Under asynchronous brain activity, many FSs (>60%) elicited small-amplitude mu-rhythm-like activity in the barrel cortex concomitant with FS-related rhythms in the occipital cortex and resulted in significant augmentation of 7-12 Hz power in the parietal region. Furthermore, a large portion of FSs (>60%) revealed increase of 7-12 Hz power of the parietal cortex after ethosuximide administration (100 mg/kg ip) in Long-Evans rats. Similar FS-elicited phenomena also appeared in Wistar rats. Characteristics of FS-elicited mu-rhythm-like activities were consistent with those observed in humans, and they remarkably differed from those of spontaneous HVRS discharges. These results support the hypothesis that HVRS activity in Long-Evans rats may be an absence-like seizure activity rather than the mu rhythm.

Action Potentials↗

PubMed2006

Modulation of somatosensory evoked potentials during wake-sleep states and spike-wave discharges in the rat.

STUDY OBJECTIVE: To clarify the cortical evoked responses in the primary somatosensory cortex of the rat under states of waking, slow-wave sleep (SWS), paradoxical sleep (PS), and spike-wave discharges (SWDs), which are associated with absence seizure. DESIGN: Somatosensory evoked potentials (SEPs) in response to single- and paired-pulse stimulations under waking, SWS, PS, and SWDs were compared. SEPs to a single-pulse stimulus with regard to cortical spikes of sleep spindles and SWDs were also evaluated. PARTICIPANTS: Twenty Long Evans rats. INTERVENTIONS: Single- and paired-pulse innocuous electrical stimulations were applied to the tail of rats with chronically implanted electrodes in the primary somatosensory cortex and neck muscle under waking, SWS, PS, and SWDs. MEASUREMENTS AND RESULTS: SEPs displayed distinct patterns under waking/PS and SWS/SWDs. The short-latency P1-N1 wave of the SEP was severely impeded during SWDs but not in other states. Reduction of the P1-N1 magnitude to the second stimulus of the paired-pulse stimulus for interstimulus intervals of < or = 300 milliseconds appeared in waking and PS states, but the decrease occurred only at particular interstimulus intervals under SWS. Interestingly, augmentation was found under SWDs. Moreover, cyclic augmentation of the P1-N1 magnitude was associated with spindle spikes, but cyclic reduction was observed with SWD spikes. CONCLUSION: Changes in SEPs are not only behavior dependent, but also phase locked onto ongoing brain activity. Distinct short-term plasticity of SEPs during sleep spindles or SWDs may merit further studies for seizure control and tactile information processing.

Adaptation, Physiological↗

PubMed2005

Facilitation of sensory and motor recovery by thermal intervention for the hemiplegic upper limb in acute stroke patients: a single-blind randomized clinical trial.

BACKGROUND AND PURPOSE: Thermal stimulation (TS) is commonly used in orthopedic rehabilitation, but the role of TS in the facilitation of sensorimotor recovery in hemiplegic patients remains unknown. This study addressed the issue of TS intervention in the facilitation of functional outcomes. METHODS: Forty-six stroke survivors were randomly assigned to standard rehabilitation treatment and standard treatment plus TS (30 minutes daily for 6 weeks). Twenty-nine patients completed the experiment. Six measures, including Brunnstrom stage, modified motor assessment scale, grasping strength, angles of wrist extension and flexion, sensation by monofilament, and muscle tone by modified Ashworth scale, were performed weekly to evaluate sensory and motor functional outcomes. RESULTS: The performance of Brunnstrom stage and wrist extension and sensation were improved significantly after TS intervention. Recovery rates of 6 measures after TS were significantly higher than those of the control, except for grasping. Similar muscle tones were found in both groups. CONCLUSIONS: TS on the paretic hand significantly enhances the recovery of several aspects of sensory and motor functions in hemiplegic stroke patients.

Analysis of Variance↗

PubMed2005

Sleep-related vagotonic effect of zolpidem in rats.

RATIONALE: Zolpidem is a relatively new nonbenzodiazepine sedative-hypnotic. The effects of zolpidem on autonomic functions remain unclear. OBJECTIVES: The aim of this study was to evaluate the effects of zolpidem on sleep and related cardiac autonomic modulations as compared with triazolam in Wistar-Kyoto rats. METHODS: Continuous power spectral analyses of electroencephalogram (EEG), electromyogram, and heart rate variability were performed on freely moving rats during daytime sleep. The consciousness states were classified into active waking (AW), quiet sleep (QS), and paradoxical sleep (PS). Drugs were administered via gavage and data within 2 h were analyzed. RESULTS: All zolpidem (ZP3, 3 mg/kg; ZP30, 30 mg/kg) and triazolam (TZ0.075, 0.075 mg/kg; TZ0.75, 0.75 mg/kg) groups had longer accumulated QS time and averaged QS duration as compared with the vehicle control. The accumulated QS time and averaged QS duration of ZP3 were similar to those of TZ0.075. Significant suppressions of PS time were noted in all drug groups except ZP3. During QS, ZP3 and ZP30 exhibited significant increases of magnitude and percentage of EEG delta power, whereas TZ0.075 and TZ0.75 did not. Heart period and high-frequency power of heart rate variability increased significantly in ZP3 during all sleep-wake states. Both parameters, however, did not increase but even decreased in ZP30, TZ0.075, and TZ0.75. CONCLUSIONS: Zolpidem not only caused a longer and deeper sleep but also led to an elevated cardiac vagal activity at a specific dose in the rat.

Animals↗

PubMed2004

Relation between activities of the cortex and vibrissae muscles during high-voltage rhythmic spike discharges in rats.

Paroxysmal 5- to 12-Hz high-voltage rhythmic spike (HVRS) activities, which are accompanied by whisker twitching (WT), are found in Long Evans rats, but the function of these HVRS activities is still debated. In four major functional hypotheses of HVRS discharges, i.e., alpha tremor, attention/mu rhythm, idling/mu rhythm, and absence seizure, the first two hypotheses emphasize WT behavior in HVRS bouts. Whisker movement is primarily determined by activation of intrinsic and extrinsic muscles. To clarify the role of WT in HVRS activities, simultaneous recording of the activities from the cortex and intrinsic/extrinsic and neck muscles were performed. Most HVRS bouts (68.8%) revealed no time-locked WT behavior in a 2-h recording session. In addition, WT primarily arose from active protraction due to activation of intrinsic muscles followed by passive retraction. A small portion of WT resulted from activation of both vibrissae muscles with dynamic frequency-dependent phase shifts. Onset of the rhythmic vibrissae EMG significantly lagged behind HVRS onset, and the mean duration of vibrissae muscle activity was one-third to a one-half of a HVRS bout. Moreover, a greater number of HVRS bouts were associated with a longer HVRS duration and higher oscillation frequency. Oscillation frequencies of HVRS activities without WT behavior were significantly lower than those with WT. Under peripheral sensory/motor blockade by xylocaine injection, oscillation frequencies of HVRS bouts significantly decreased, but no remarkable changes in the number or duration of HVRS bouts were observed. Compared with vibrissa muscle activity during WT and exploratory whisking, the duration of muscular activity in each cycle was apparently longer during whisking bouts. Based on these results, overemphasis of the role of WT on HVRS activities might not be appropriate. Instead, HVRS discharges may be associated with absence seizure or idling state. In addition, peripheral inputs, including WT, may elevate the oscillation frequency of HVRS bouts. Moreover, different muscular controls may exist between WT and whisking.

Action Potentials↗

PubMed2004

Changes in sleep patterns in spontaneously hypertensive rats.

STUDY OBJECTIVES: To explore whether spontaneous hypertension is associated with a change in sleep pattern in rats. DESIGN: Adult male spontaneously hypertensive rats (SHR) were compared to normotensive Wistar-Kyoto rats (WKY) on their normal daytime sleep pattern. PARTICIPANTS: Ten WKY and 10 SHR. INTERVENTIONS: All rats had electrodes implanted for polygraphic recordings. Weeks later, a 5-hour daytime sleep-weakfulness recording session was analyzed. MEASUREMENTS AND RESULTS: Electroencephalogram and electromyogram signals were subjected to continuous power spectral analysis, from which mean power frequency of the electroencephalogram and power of the electromyogram were quantified. Active waking (AW), quiet sleep (QS), and paradoxical sleep (PS) were defined every 8 seconds from corresponding mean power frequency and electromyogram power readings. Analysis of heart-rate variability was derived from the electrocardiogram signals. Macrostructural analysis of sleep revealed that SHR were characterized by fewer QS and PS episodes and eventually shorter accumulated QS and PS times as compared to WKY. SHR also had more QS-to-AW transitions but fewer QS-to-PS transitions. Microstructural analysis revealed that SHR were associated with more-frequent interruptions during QS. Analysis of heart-rate variability indicated that SHR had similar R-R intervals and lower high-frequency (0.6-2.4 Hz) power but a higher ratio of low-frequency (0.06-0.6 Hz) power to high-frequency power during the daytime recording as compared to WKY. CONCLUSIONS: As compared to WKY, SHR may have less sleep time, poorer sleep quality, and a greater tendency to wake up from QS. Such changes in sleep may be concomitant with cardiac autonomic changes. Our methodology offers a convenient yet effective way to study the constitution, sequence, and interruption of sleep in the rat.

Animals↗

PubMed2003

Sleep-related sympathovagal imbalance in SHR.

The role of the autonomic nervous system in spontaneous hypertension during each stage of the sleep-wake cycle remains unclear. The present study attempted to evaluate the differences in cardiac autonomic modulations among spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto rats (WKY), and Sprague-Dawley rats (SD) across sleep-wake cycles. Continuous power spectral analysis of electroencephalogram, electromyogram, and heart rate variability was performed in unanesthetized free moving rats during daytime sleep. Frequency-domain analysis of the stationary R-R intervals (RR) was performed to quantify the high-frequency power (HF), low-frequency power (LF)-to-HF ratio (LF/HF), and normalized LF (LF%) of heart rate variability. WKY and SD had similar mean arterial pressure, which is significantly lower than that of SHR during active waking, quiet sleep, and paradoxical sleep. Compared with WKY and SD, SHR had lower HF but similar RR, LF/HF, and LF% during active waking. During quiet sleep, SHR developed higher LF/HF and LF% in addition to lower HF. SHR ultimately exhibited significantly lower RR accompanied with higher LF/HF and LF% and lower HF during paradoxical sleep compared with WKY. We concluded that significant cardiac sympathovagal imbalance with an increased sympathetic modulation occurred in SHR during sleep, although it was less evident during waking.

Animals↗

PubMed2003

Dynamic changes of gamma activities of somatic cortical evoked potentials during wake-sleep states in rats.

Somatic evoked potentials (SEPs) from three brain sites elicited by electrical stimulation in 10 rats were recorded throughout wake-sleep states with intrinsic changes in temporal architectures under different vigilance states. Based on the patterns of spontaneous brain and muscle activities, three characteristic vigilance states could be classified: awake, slow-wave sleep (SWS), and paradoxical sleep (PS). Spontaneous gamma activities prominently appeared under awake and PS states, but less under SWS. SEP was filtered out via a zero-phase highpass filter (20 Hz) to extract the gamma activity of the SEP (gammaSEP). Gamma oscillations of SEPs were clearly observed and were reset by extrinsic electrical stimulation under awake and PS, but not under SWS state. Dynamic changes of gammaSEPs during wake-sleep states were also confirmed by multiple single-trial spectral analyses. Moreover, gamma oscillations were initiated at the parietal site, and the speed of its propagation in both frontal and occipital directions was significantly different. In addition, a clear two-component architecture of SEPs was observed under awake and PS states, and the gamma rhythmic activity was associated with the second component. Because gamma oscillations are related to feature binding in the waking state, evoked gammaSEPs in PS may be related to sensory integration analogous to the awake ones. By contrast, a long-lasting biphasic component of SEPs, which might be associated with augmenting response, was observed during SWS. Based on these results, the sleeping brain continuously monitors and selectively processes incoming flow. Our results also strongly support a two-stage information processing taking place in the cortex during sleep.

Animals↗

PubMed2003

Is spontaneous high-voltage rhythmic spike discharge in Long Evans rats an absence-like seizure activity?

A distinct high-voltage rhythmic spike (HVRS) discharge characterized by a barrage of negative spikes oscillating at 5-12 Hz was observed in chronically implanted Long Evans rats. Spontaneous HVRS discharges were exhibited in 90% of 40 Long Evans rats and occurred during sudden arrest of ongoing behavior (immobility) with occasional facial/whisker twitching. However, the function of HVRS discharges in Long Evans rats remains inconclusive to date and has been associated with alpha tremor/mu rhythm, attentive mu wave, and absence seizure. To elucidate the function of HVRS discharges in Long Evans rats, several experiments were performed. In a 6-h recording session (12:00-18:00), HVRS activities primarily occurred in several specific vigilance states, being particularly abundant in a short-lasting period before vigilance changes. Several characteristics, such as durations, oscillatory frequencies, and interspike intervals (ISIs) of HVRS discharges, were altered during wake-sleep states. Oscillatory frequencies were negatively correlated with durations of HVRS segments. In addition, ISIs of a HVRS episode exhibited a crescendo-decrescendo pattern. These variable ISIs could explain why a negative correlation was found between oscillatory frequencies and durations of HVRS episodes. Moreover, HVRS discharges were demonstrated to have widespread and near-synchronous distribution to bilateral cortical areas. In addition, innocuous electrical stimuli were unable to stop ongoing HVRS discharges. By contrast, noxious stimuli elicited behavioral arousal and immediately terminated most HVRS discharges. Cortical-evoked potentials in response to mild electrical stimulation under HVRS discharges were different from those under waking state but resemble those under slow-wave sleep with a smaller magnitude. Moreover, the temporal and spectral characteristics of spontaneous HVRS activities were analogous to those of seizure activities induced by penicillin and pentylenetetrazol. The incidence of spontaneous HVRS discharges was significantly decreased by ethosuximide administration. Based on these results, HVRS discharge might not be associated with a voluntary mu-rhythm behavior, instead it behaves as an absence-like seizure activity. These results were also collaborated using other genetic absence-seizure rats, such as WAG/Rij and GAERS rats. Possible mechanisms for the generation and termination of paroxysmal HVRS discharges are also discussed.

Animals↗

PubMed2003

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.

Action Potentials↗

PubMed2003

Reticular thalamic responses to nociceptive inputs in anesthetized rats.

The present study compares nociceptive responses of neurons in the reticular thalamic nucleus (RT) to those of the ventroposterior lateral nucleus (VPL). Extracellular single-unit activities of cells in the RT and VPL were recorded in anesthetized rats. Only units with identified tactile receptive fields in the forepaw or hindpaw were studied. In the first series of experiments, RT and VPL responses to pinching with a small artery clamp were tested with the rats under pentobarbital, urethane, ketamine, or halothane anesthesia. Under all types of anesthesia, many RT units were inhibited. Second, the specificity of the nociceptive response was tested by pinching and noxious heating of the unit's tactile receptive field. Of the 39 VPL units tested, 20 were excited by both types of noxious stimuli. In sharp contrast, of the 30 RT units tested, none were excited and 17 were inhibited. In a third series of experiments, low-intensity and beam-diffused CO(2) laser irradiation was used to activate peripheral nociceptive afferents. Wide-dynamic-range VPL units responded with short- and long-latency excitations. In contrast, RT units had short-latency excitation followed by long-latency inhibition. Nociceptive input inhibited RT units in less than 500 ms. We conclude that a significant portion of RT neurons were polysynaptically inhibited by nociceptive inputs. Since all the cells tested were excited by light tactile inputs, the somatosensory RT may serve in the role of a modality gate, which modifies (i.e. inhibits) tactile inputs while letting noxious inputs pass.

Action Potentials↗

PubMed2003

Relationship between electroencephalogram slow-wave magnitude and heart rate variability during sleep in rats.

To explore whether depth of sleep is related to changes in autonomic control in rats, continuous power-spectral analysis of electroencephalogram (EEG) and heart rate variability (HRV) was performed in unanesthetized rats during normal daytime sleep. Quiet sleep (QS) was associated with an increase in high-frequency power of HRV (0.6-2.4 Hz, HF) but a decrease in low-frequency power (0.06-0.6 Hz) to HF ratio (LF/HF) compared with awakening. During QS, LF/HF was significantly and negatively correlated with delta power of EEG (0.5-4.0 Hz), whereas mean R-R interval and HF were not. As in humans, cardiac sympathetic regulation in rats is negatively related to the depth of sleep during QS, although vagal regulation is not. Our methodology offers a parallel way of studying the interaction between cerebral cortical and autonomic functions in rats.

Animals↗

PubMed2002

A low-noise flexible integrated system for recording and analysis of multiple electrical signals during sleep-wake states in rats.

A low-noise flexible system for the simultaneous recording and analysis of several electrical signals (EEG, ECG, EMG, and diaphragm EMG) from the same rat was constructed for studying changes in physiological functions during the sleep-wake cycle. The hardware in the system includes a multichannel amplifier, a video camera, a timer code generator, and a PC. A miniature buffer headstage with high-input impedance connected to a 6-channel amplifier was developed. All electrical activities devoid of 60 Hz interference could be consistently recorded by our low-cost amplifier with no shielding treatment. The analytical software was established in the LabVIEW environment and consisted of three major frames: temporal, spectral, and nonlinear analyses. These analytical tools demonstrated several distinct utilities. For example, the sleep-wake states could be successfully distinguished by combining temporal and spectral analyses. An obvious theta rhythm during rapid-eye-movement sleep (REMS) was recorded from parietal to occipital cortical areas but not from the frontal area. In addition, two types of sleep apnea with/without cardiac arrhythmias were observed under REMS condition. Moreover, the evoked potentials of the primary somatosensory cortex elicited by innocuous electrical pulses were modulated by vigilant states, especially under a slow-wave sleep state. These results show that our system delivers high-quality signals and is suitable for sleep investigations. The system can be easily expanded by combining other recording devices, like a plethysmograph. This compact system can also be easily modified and applied to other related physiological or pharmacological studies.

Animals↗

PubMed2002

Neural and cardiac activities are altered by injection of picomoles of glutamate into the nucleus ambiguus of the rat.

A quantitative evaluation of the thresholds of changes in the firing rate/pattern and depolarizing block of the neuron and the bradycardiac response by pressure microinjection of 10 mM glutamate (Glu) into the region of the nucleus ambiguus (NA) of the ventral medulla was performed in anesthetized rats. A change in neuronal activity was shown with injection of about 2 pmol of Glu. A depolarizing block of single-unit activity could be observed at 2.9 +/- 0.3 nl (approximately 30 pmol, n = 22). Maximal bradycardiac response (-50 +/- 5%) was elicited with 4.4 +/- 0.7 nl (approximately 50 pmol, n = 10), which is significantly smaller than the ranges used in previous studies. Based on these results, a safe and effective use of 10 mM Glu to induce neuronal or physiological response should be in the range of a few nanoliters and less than 100 pmol, especially for the NA.

Animals↗