Impacts of Age and Gender on Brain Edema in a Mouse Water Intoxication Model.

Brain edema causes abnormal fluid retention and can be fatal in severe cases. Although it develops in various diseases, most treatments for brain edema are classical. We analyzed the impacts of age and gender on the characteristics of a water intoxication model that induces pure brain edema in mice and examined the model's usefulness for research regarding new treatments for brain edema. C57BL/6J mice received an intraperitoneal administration of 10% body weight distilled water, and we calculated the brain water content by measuring the brain-tissue weight immediately after dissection and after drying. We analyzed 8-OHdG and caspase-3 values to investigate the brain damage. We also applied this model in aquaporin 4 knockout (AQP4-) mice and compared these mice with wild-type mice. The changes in water content differed by age and gender, and the 8-OHdG and caspase-3 values differed by age. Suppression of brain edema by AQP4- was also confirmed. These results clarified the differences in the onset of brain edema by age and gender, highlighting the importance of considering the age and gender of model animals. Similar studies using genetically modified mice are also possible. Our findings indicate that this water intoxication model is effective for explorations of new brain edema treatments.

Ryanodine receptors are involved in the improvement of depression-like behaviors through electroconvulsive shock in stressed mice.

BACKGROUND: Electroconvulsive therapy (ECT) is effective for treating depression. However, the mechanisms underlying the antidepressant effects of ECT remain unknown. Depressed patients exhibit abnormal Ca2+ kinetics. Early stages of the intracellular Ca2+ signaling pathway involve the release of Ca2+ from the endoplasmic reticulum (ER) via Ca2+ release channels. OBJECTIVE: We considered that depression may be improved via ECT-induced normalization of intracellular Ca2+ regulation through the Ca2+ release channels. The current study aimed to investigate the effects of ECT on two Ca2+ release channels, ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP3Rs). METHODS: A mouse depression-like model subjected to water immersion with restraint stress was administered electroconvulsive shock (ECS) therapy. Their depression-like status was behaviorally and histologically assessed using forced swimming tests, novelty-suppressed feeding tests, and by evaluating neurogenesis in the hippocampal dentate gyrus, respectively. A RyRs blocker, dantrolene, was administered prior to ECS, and the changes in depression-like conditions were examined. RESULTS: The protein expressions of RyR1 and RyR3 significantly increased in the hippocampus of the mouse model with depression-like symptoms. This increase was attenuated as depression-like symptoms were reduced due to ECS application. However, pre-injection with dantrolene reduced the antidepressant effects of ECS. CONCLUSIONS: A significant increase in RyRs expression in a depression-like state and exacerbation of depression-like symptoms by RyRs inhibitors may be caused by RyRs dysfunction, suggesting overexpression of RyRs is a compensatory effect. Normalization of RyRs expression levels by ECS suggests that ECT normalizes the Ca2+ release via RyRs. Thus, normalizing the function of RyRs may play an important role in the therapeutic effect of ECT.

The protective effect and mechanism of COA-Cl in acute phase after spinal cord injury.

Spinal cord injury (SCI) induces severe motor and sensory dysfunction. We previously showed the neuroprotective effects of COA-Cl, a novel synthesized adenosine analog, in a rat stroke model. In this study, we evaluated the neuroprotective effects of COA-Cl in acute phase of SCI. SCI was induced in rats at the T9 vertebra by using a drop device. Rats were divided into acute and subacute groups. A 5-day dose of 6 mg/kg COA-Cl in saline was given to the acute group immediately after SCI and the subacute group 4 days after SCI. Motor function assessed by Basso-Beattie-Bresnahan scoring and inclined plane test improved significantly in the acute group while the subacute group did not. Histological evaluation and TUNEL staining revealed that both the cavity volume and apoptosis were significantly decreased in the acute group compared with the subacute group. In addition, pERK/ERK was increased in the acute group 7 days after SCI. These results suggest that COA-Cl exerts neuroprotective effects via the ERK pathway when administered in the acute phase after SCI, resulting in the recovery of motor function. COA-Cl could be a novel therapeutic agent for the acute phase of SCI.

Very Early Initiation Reduces Benefits of Poststroke Rehabilitation Despite Increased Corticospinal Projections.

Background. Although the effect of rehabilitation is influenced by aspects of the training protocol, such as initiation time and intensity of training, it is unclear whether training protocol modifications affect the corticospinal projections. Objective. The present study was designed to investigate how modification of initiation time (time-dependency) and affected forelimb use (use-dependency) influence the effects of rehabilitation on functional recovery and corticospinal projections. Methods. The time-dependency of rehabilitation was investigated in rats forced to use their impaired forelimb immediately, at 1 day, and 4 days after photothrombotic stroke. The use-dependency of rehabilitation was investigated by comparing rats with affected forelimb immobilization (forced nonuse), unaffected forelimb immobilization (forced use), and a combination of forced use and skilled forelimb training beginning at 4 days after stroke. Results. Although forced use beginning 1 day or 4 days after stroke caused significant functional improvement, immediate forced limb use caused no functional improvement. On the other hand, a combination of forced use and skilled forelimb training boosted functional recovery in multiple tasks compared to simple forced use treatment. Histological examination showed that no treatment caused brain damage. However, a retrograde tracer study revealed that immediate forced use and combination training, including forced use and skilled forelimb training, increased corticospinal projections from the contralesional and ipsilesional motor cortex, respectively. Conclusions. These results indicate that although both very early initiation time and enhanced skilled forelimb use increased corticospinal projections, premature initiation time hampers the functional improvement induced by poststroke rehabilitation.

Effects of intravesicular loading of a Ca2+ chelator and depolymerization of actin fibers on neurotransmitter release in frog motor nerve terminals.

Ca2+ -induced Ca2+ release (CICR) via type-3 ryanodine receptor enhances neurotransmitter release in frog motor nerve terminals. To test a possible role of synaptic vesicle in CICR, we examined the effects of loading of EGTA, a Ca2+ chelator, into synaptic vesicles and depolymerization of actin fibers. Intravesicular EGTA loading via endocytosis inhibited the ryanodine sensitive enhancement of transmitter release induced by tetanic stimulation and the associated rises in intracellular-free Ca2+ ([Ca2+ ]i : Ca2+ transients). Latrunculin A, a depolymerizer of actin fibers, enhanced both spontaneous and stimulation-induced transmitter release, but inhibited the enhancement of transmitter release elicited by successive tetanic stimulation. The results suggest a possibility that the activation of CICR from mobilized synaptic vesicles caused the enhancement of neurotransmitter release.

Improvement of motor function induced by skeletal muscle contraction in spinal cord-injured rats.

BACKGROUND: The involvement of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) in functional recovery after spinal cord injury (SCI) by treadmill training has been suggested. The precise mechanism is poorly understood. However, muscle-derived bioactive molecules (myokines) are known to be produced by muscle contraction. Although BDNF is a myokine and is considered to be a potential mediator of neuroplasticity following exercise, its contribution to motor function recovery after SCI has not yet been described in detail. PURPOSE: To investigate the role of muscle contraction in motor function recovery after SCI, with a focus on BDNF. STUDY DESIGN: Male Sprague-Dawley rats (aged 8-9 weeks) were used to establish the SCI model. Percutaneous electrical muscle stimulation (10 mA, 2 Hz, 10 minutes) was applied to both hindlimbs of the rats immediately after SCI. The stimulation was performed once per day for 4 weeks. The sham, SCI only (SCI), and SCI with electrical muscle stimulation (SCI+ES) groups were compared. METHODS: Spinal cord injury was induced by dropping a 20 g rod with an apex diameter of 2 mm from a height of 25 mm onto the spine of an anesthetized rat at the T9 level. Motor function was assessed using the Basso-Beattie-Bresnahan Locomotor Scale, inclined plane test, and rotarod test. One week after injury, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were counted at the injury epicenter, and the level of BDNF was measured in both the spinal cord and the anterior tibial muscle. Four weeks after injury, the cavity volume of the epicenter and the level of phosphorylated growth-associated protein 43 in the spinal cord were measured. RESULTS: Significantly improved Basso-Beattie-Bresnahan scores and inclined plane test results were observed in the SCI+ES group compared with those in the SCI group at 4 weeks post-SCI. We also observed a decrease in the cavity volume and an increase in phosphorylated growth-associated protein 43 levels in the SCI+ES group. Electrical muscle stimulation decreased the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells in the epicenter and increased the levels of BDNF in the spinal cord and lower limb muscles at 1 week post-SCI. CONCLUSIONS: Electrical muscle stimulation improved motor function and increased BDNF levels in both the muscles and the spinal cords of rats subjected to SCI. Muscle contraction-induced BDNF expression might be involved in motor recovery during rehabilitation. CLINICAL RELEVANCE: Our study provides experimental evidence for a possible therapeutic role of peripheral electrical muscle stimulation to enhance motor recovery after SCI.

Constraint-induced movement therapy improves efficacy of task-specific training after severe cortical stroke depending on the ipsilesional corticospinal projections.

Descending spinal pathways (corticospinal, rubrospinal, and reticulospinal) are believed to contribute to functional recovery resulting from rehabilitative training after stroke. However, the contribution of each pathway remains unclear. In the current study, we investigated rehabilitation-induced functional recovery and remodelling of the descending spinal pathways after severe cortical stroke in rats followed by 3 weeks of various rehabilitation [constraint-induced movement therapy (CIMT), skilled forelimb reaching, rotarod, and treadmill exercise]. Following photothrombotic stroke, 96% of corticospinal neurons in the ipsilesional motor cortex were destroyed. Despite the preservation of 82% of total spinal projection neurons (e.g. rubrospinal and reticulospinal projection neurons), rats showed persistent and severe disability, especially in skilled motor function. In this severe stroke model, only CIMT promoted functional recovery, associated with increased corticospinal projections from the peri-infarct motor cortex. Rehabilitation-induced recovery was reversed when the restored corticospinal neurons were destroyed by a second stroke. These data indicate that training-induced functional recovery is dependent on ipsilesional corticospinal projections, which highlights the importance of using strategies to enhance survival, axonal remodelling, or regeneration of corticospinal neurons to effectively restore function in severely affected stroke patients.

Rehabilitative skilled forelimb training enhances axonal remodeling in the corticospinal pathway but not the brainstem-spinal pathways after photothrombotic stroke in the primary motor cortex.

Task-specific rehabilitative training is commonly used for chronic stroke patients. Axonal remodeling is believed to be one mechanism underlying rehabilitation-induced functional recovery, and significant roles of the corticospinal pathway have previously been demonstrated. Brainstem-spinal pathways, as well as the corticospinal tract, have been suggested to contribute to skilled motor function and functional recovery after brain injury. However, whether axonal remodeling in the brainstem-spinal pathways is a critical component for rehabilitation-induced functional recovery is not known. In this study, rats were subjected to photothrombotic stroke in the caudal forelimb area of the primary motor cortex and received rehabilitative training with a skilled forelimb reaching task for 4 weeks. After completion of the rehabilitative training, the retrograde tracer Fast blue was injected into the contralesional lower cervical spinal cord. Fast blue-positive cells were counted in 32 brain areas located in the cerebral cortex, hypothalamus, midbrain, pons, and medulla oblongata. Rehabilitative training improved motor performance in the skilled forelimb reaching task but not in the cylinder test, ladder walk test, or staircase test, indicating that rehabilitative skilled forelimb training induced task-specific recovery. In the histological analysis, rehabilitative training significantly increased the number of Fast blue-positive neurons in the ipsilesional rostral forelimb area and secondary sensory cortex. However, rehabilitative training did not alter the number of Fast blue-positive neurons in any areas of the brainstem. These results indicate that rehabilitative skilled forelimb training enhances axonal remodeling selectively in the corticospinal pathway, which suggests a critical role of cortical plasticity, rather than brainstem plasticity, in task-specific recovery after subtotal motor cortex destruction.

The Role of Endogenous Neurogenesis in Functional Recovery and Motor Map Reorganization Induced by Rehabilitative Therapy after Stroke in Rats.

BACKGROUND AND OBJECTIVE: Endogenous neurogenesis is associated with functional recovery after stroke, but the roles it plays in such recovery processes are unknown. This study aims to clarify the roles of endogenous neurogenesis in functional recovery and motor map reorganization induced by rehabilitative therapy after stroke by using a rat model of cerebral ischemia (CI). METHODS: Ischemia was induced via photothrombosis in the caudal forelimb area of the rat cortex. First, we examined the effect of rehabilitative therapy on functional recovery and motor map reorganization, using the skilled forelimb reaching test and intracortical microstimulation. Next, using the same approaches, we examined how motor map reorganization changed when endogenous neurogenesis after stroke was inhibited by cytosine-ß-d-arabinofuranoside (Ara-C). RESULTS: Rehabilitative therapy for 4 weeks after the induction of stroke significantly improved functional recovery and expanded the rostral forelimb area (RFA). Intraventricular Ara-C administration for 4-10 days after stroke significantly suppressed endogenous neurogenesis compared to vehicle, but did not appear to influence non-neural cells (e.g., microglia, astrocytes, and vascular endothelial cells). Suppressing endogenous neurogenesis via Ara-C administration significantly inhibited (~50% less than vehicle) functional recovery and RFA expansion (~33% of vehicle) induced by rehabilitative therapy after CI. CONCLUSIONS: After CI, inhibition of endogenous neurogenesis suppressed both the functional and anatomical markers of rehabilitative therapy. These results suggest that endogenous neurogenesis contributes to functional recovery after CI related to rehabilitative therapy, possibly through its promotion of motor map reorganization, although other additional roles cannot be ruled out.

Neural network remodeling underlying motor map reorganization induced by rehabilitative training after ischemic stroke.

Motor map reorganization is believed to be one mechanism underlying rehabilitation-induced functional recovery. Although the ipsilesional secondary motor area has been known to reorganize motor maps and contribute to rehabilitation-induced functional recovery, it is unknown how the secondary motor area is reorganized by rehabilitative training. In the present study, using skilled forelimb reaching tasks, we investigated neural network remodeling in the rat rostral forelimb area (RFA) of the secondary motor area during 4weeks of rehabilitative training. Following photothrombotic stroke in the caudal forelimb area (CFA), rehabilitative training led to task-specific recovery and motor map reorganization in the RFA. A second injury to the RFA resulted in reappearance of motor deficits. Further, when both the CFA and RFA were destroyed simultaneously, rehabilitative training no longer improved task-specific recovery. In neural tracer studies, although rehabilitative training did not alter neural projection to the RFA from other brain areas, rehabilitative training increased neural projection from the RFA to the lower spinal cord, which innervates the muscles in the forelimb. Double retrograde tracer studies revealed that rehabilitative training increased the neurons projecting from the RFA to both the upper cervical cord, which innervates the muscles in the neck, trunk, and part of the proximal forelimb, and the lower cervical cord. These results suggest that neurons projecting to the upper cervical cord provide new connections to the denervated forelimb area of the spinal cord, and these new connections may contribute to rehabilitation-induced task-specific recovery and motor map reorganization in the secondary motor area.

Exercise in the Early Stage after Stroke Enhances Hippocampal Brain-Derived Neurotrophic Factor Expression and Memory Function Recovery.

BACKGROUND: Exercise in the early stage after stroke onset has been shown to facilitate the recovery from physical dysfunction. However, the mechanism of recovery has not been clarified. In this study, the effect of exercise on spatial memory function recovery in the early stage was shown, and the mechanism of recovery was discussed using a rat model of brain embolism. METHODS: Intra-arterial microsphere (MS) injection induced small emboli in the rat brain. Treadmill exercise was started at 24 hours (early group) or 8 days (late group) after MS injection. The non-exercise (NE) and sham-operated groups were included as controls. Memory function was evaluated by the Morris water maze test, and hippocampal levels of brain-derived neurotrophic factor (BDNF) were measured by enzyme-linked immunosorbent assays. To further investigate the effect of BDNF on memory function, BDNF was continuously infused into the hippocampus via implantable osmotic pumps in the early or late stage after stroke. RESULTS: Memory function significantly improved only in the early group compared with the late and the NE groups, although hippocampal BDNF concentrations were temporarily elevated after exercise in both the early and the late groups. Rats infused with BDNF in the early stage exhibited significant memory function recovery; however, rats that received BDNF infusion in the late stage showed no improvement. CONCLUSION: Exercise elevates hippocampal BDNF levels in the early stage after cerebral embolism, and this event facilitates memory function recovery.

COA-Cl, a Novel Synthesized Nucleoside Analog, Exerts Neuroprotective Effects in the Acute Phase of Intracerebral Hemorrhage.

BACKGROUND: A previous study in our laboratory showed the neuroprotective effects of COA-Cl, a novel synthesized adenosine analog, in a rat cerebral ischemia model. The purpose of the present study was to evaluate the neuroprotective effects of COA-Cl in intracerebral hemorrhage (ICH), another common type of stroke, and investigate potential mechanisms of action. METHODS: Adult Sprague-Dawley rats received an injection of 100 µl autologous whole blood into the right basal ganglia. COA-Cl (30 µg/kg) was injected intracerebroventricularly 10 minutes after ICH. A battery of motor deficit tests were performed at 1 day, 3 days, 5 days, and 7 days after ICH. To investigate the mechanism of action, brain water content, TUNEL staining and 8-OHdG immunostaining, and ELISA (to assess oxidative stress) were used. RESULTS: COA-Cl treatment significantly attenuated sensorimotor deficits and reduced brain edema 1 day after ICH. Furthermore, the numbers of perihematomal TUNEL- and 8-OHdG-positive cells were significantly decreased in COA-Cl treated ICH rats. CONCLUSIONS: These results indicate that COA-Cl has neuroprotective effects in ICH. Furthermore, our study provides evidence that COA-Cl may reduce oxidative stress, which may be one mechanism underlying its neuroprotective effects.

Ryanodine receptors contribute to the induction of ischemic tolerance.

Ischemic tolerance (IT) is induced by a variety of insults to the brain (e.g., nonfatal ischemia, heat and hypoxia) and it provides a strong neuroprotective effect. Although the mechanisms are still not fully elucidated, Ca(2+) is regarded as a key mediator of IT. Ryanodine receptors (RyRs) are located in the sarcoplasmic/endoplasmic reticulum membrane and are responsible for the release of Ca(2+) from intracellular stores. In brain, neuronal RyRs are thought to play a role in various neuropathological conditions, including ischemia. The purpose of the present study was to investigate the involvement of RyRs in IT. Pretreatment with a RyR antagonist, dantrolene (25mg/kg, i.p), blocked IT in a gerbil global ischemia model, while a RyR agonist, caffeine (100mg/kg, i.p), stimulated the production of IT. In vitro, using rat hippocampal cells, short-term oxygen/glucose deprivation induced preconditioning and RyR antagonists, dantrolene (50 and 100 µM) and ryanodine (100 and 200 µM) prevented it. RyR protein and mRNA levels were transiently decreased after induction of IT. These results suggest that RyRs are involved in the induction of ischemic tolerance.

Evaluation of biomolecular distributions in rat brain tissues by means of ToF-SIMS using a continuous beam of Ar clusters.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) provides detailed chemical structure information and high spatial resolution images. Therefore, ToF-SIMS is useful for studying biological phenomena such as ischemia. In this study, in order to evaluate cerebral microinfarction, the distribution of biomolecules generated by ischemia was measured with ToF-SIMS. ToF-SIMS data sets were analyzed by means of multivariate analysis for interpreting complex samples containing unknown information and to obtain biomolecular mapping indicated by fragment ions from the target biomolecules. Using conventional ToF-SIMS (primary ion source: Bi cluster ion), it is difficult to detect secondary ions beyond approximately 1000 u. Moreover, the intensity of secondary ions related to biomolecules is not always high enough for imaging because of low concentration even if the masses are lower than 1000 u. However, for the observation of biomolecular distributions in tissues, it is important to detect low amounts of biological molecules from a particular area of tissue. Rat brain tissue samples were measured with ToF-SIMS (J105, Ionoptika, Ltd., Chandlers Ford, UK), using a continuous beam of Ar clusters as a primary ion source. ToF-SIMS with Ar clusters efficiently detects secondary ions related to biomolecules and larger molecules. Molecules detected by ToF-SIMS were examined by analyzing ToF-SIMS data using multivariate analysis. Microspheres (45 µm diameter) were injected into the rat unilateral internal carotid artery (MS rat) to cause cerebral microinfarction. The rat brain was sliced and then measured with ToF-SIMS. The brain samples of a normal rat and the MS rat were examined to find specific secondary ions related to important biomolecules, and then the difference between them was investigated. Finally, specific secondary ions were found around vessels incorporating microspheres in the MS rat. The results suggest that important biomolecules related to cerebral microinfarction can be detected by ToF-SIMS.

Delayed administration of the nucleic acid analog 2Cl-C.OXT-A attenuates brain damage and enhances functional recovery after ischemic stroke.

2Cl-C.OXT-A (COA-Cl) is a novel nucleic acid analog that enhances angiogenesis through extracellular signal-regulated kinase 1 or 2 (ERK1/2) activation. ERK1/2 is a well-known kinase that regulates cell survival, proliferation and differentiation in the central nervous system. We performed in vitro and in vivo experiments to investigate whether COA-Cl can attenuate neuronal damage and enhance recovery after brain ischemia. In primary cortical neuron cultures, COA-Cl prevented neuronal injury after 2h of oxygen-glucose deprivation. COA-Cl increased phospho-ERK levels in a dose-dependent manner and COA-Cl-induced neuroprotection and ERK1/2 activation was inhibited by suramin or PD98059. The effect of COA-Cl was evaluated in vivo with 60min of middle cerebral artery occlusion combined with bilateral common carotid artery occlusion. COA-Cl or saline was injected intracerebroventricularly 5min after reperfusion. COA-Cl significantly reduced infarct volume and improved neurological deficits upon injection of 15 or 30µg/kg COA-Cl. Moreover, COA-Cl reduced the number of TUNEL positive cells in ischemic boundary, while rCBF was not significantly changed by COA-Cl administration. We also evaluated the effect of delayed COA-Cl administration on recovery from brain ischemia by continuous administration of COA-Cl from 1 to 8 days after reperfusion. Delayed continuous COA-Cl administration also reduced infarct volume. Furthermore, COA-Cl enhanced peri-infarct angiogenesis and synaptogenesis, resulting in improved motor function recovery. Our findings demonstrate that COA-Cl exerts both neuroprotective and neurorestorative effects over a broad therapeutic time window, suggesting COA-Cl might be a novel and potent therapeutic agent for ischemic stroke.

Changes in the lactate threshold during treadmill exercise after microsphere-induced infarction in rats.

The aim of this study was to clarify changes in the lactate threshold (LT) in the acute period after cerebral infarction. Cerebral infarction was induced by the injection of microspheres (MS) into the right internal carotid artery. To estimate the degree of neurologic deficit caused by surgery, the behaviors of all rats were evaluated in terms of typical symptoms of stroke in rats. The rotarod test was used to evaluate equilibrium function. Rats were forced to perform stepwise treadmill exercises, and serial changes in blood lactate concentration were measured for determination of the LT. The average treadmill speed at the LT and the rotarod test performance in MS rats was significantly lower than those in sham-operated rats on postsurgery day 2. However, although neurologic deficits disappeared on postsurgery day 7 in MS rats, LT level and rotarod test performance were significantly lower than in sham-operated rats. These results suggest that the decrease in LT in the acute period after cerebral infarction might be induced by impaired equilibrium function. Other possibilities are discussed as well.

Emetic stimulation inhibits the swallowing reflex in decerebrate rats.

The effects of emetic stimulation on the swallowing reflex were investigated in decerebrated rats. Hypoxia, gastric distension and LiCl administration were used as emetic stimulations. The swallowing reflex was elicited by electrical stimulation of the superior laryngeal nerve (SLN, 20 Hz, 3-5 V, 0.3 ms duration) for 20 s. To examine the effect of hypoxia, nitrogen gas was inhaled under artificial ventilation. There were significantly fewer swallows during a decrease in PO(2) than under air ventilation (p<0.05). The number of swallows during 3-ml stomach distension was significantly lower than that before distension (p<0.05). Intravenous administration of LiCl (100 mg/kg) also significantly reduced the number of swallows (p<0.05). The combination of SLN stimulation and emetic stimuli occasionally produced burst activity of abdominal muscles, which might be associated with the gag reflex. Both the gag and swallowing reflexes are well known to be mediated by the nucleus of the solitary tract. The physiological roles of the gag reflex and the swallowing reflex are considered to be reciprocal. Taken together, these results suggest that emetic stimulation inhibits the swallowing pattern generator via the nucleus of the solitary tract, which in turn facilitates the gag reflex.

Differences in autonomic responses between subjects with and without nausea while watching an irregularly oscillating video.

Prodromal signs such as cardiac rhythm disturbance and changes in gastric motility are generally induced before and during nausea in humans. These autonomic reactions were compared in subjects who were or were not experiencing nausea. Nausea was induced by having the subjects view a movie of oscillating pictures. Seventeen healthy volunteers were asked to relax their muscles and watch the movie. Electrogastrogram (EGG), electrocardiogram (ECG), palmar and metopic perspiration, digital blood flow and thoracic movement related to respiration were simultaneously measured while the subjects viewed the movie. A total of 11 of 17 subjects complained of nausea after watching the movie. The characteristic changes in their autonomic responses during exposure to the movie were as follows. The power of the EGG, heart rate and metopic perspiration significantly increased compared to those before watching the movie. The respiratory cycle gradually increased during and even after watching the movie. In contrast, no significant changes in the power of the EGG, heart rate and metopic perspiration were observed in the remaining six subjects who did not experience nausea. The role of the autonomic nervous system in nausea is discussed. These results suggest that these symptoms regarding the sympathetic nervous system could actually be defensive reactions against the sensation of nausea.

Evaluation of basic performance and applicability of a newly developed in vivo nitric oxide sensor.

Direct measurement of nitric oxide (NO) is of great importance and value for both in vitro and in vivo studies on dynamic NO bioactivity. Here, we evaluated the basic performance of a newly developed NO sensor (Innovative Instruments, Inc.). Unlike other NO sensors, the new NO sensor has a highly durable, gas-permeable coating and is affected much less by electrical interference due to its integrated structure where working and reference electrodes are combined in a single element. Calibration with NO gas showed high sensitivity of about 580 pA per nmol-NO l(-1) (the detection limit 0.08 nmol-NO l(-1), S/N = 3). This sensor also showed high selectivity (25,000 times and more) to NO, compared with NO-related reagents such as L-arginine, N(G)-monomethyl-L-arginine, acetylcholine, nitroglycerin (NTG) and tetrahydrobiopterin as well as dissolved oxygen. As an in vivo application, the sensor was located in the anaesthetized rat abdominal aorta to measure NTG-derived plasma NO. lntra-aortic infusion of 0.5 mg NTG caused a measurable increase in plasma NO level (2.0 +/- 2.2 nmol l(-1), mean +/- SD, n = 3). In conclusion, the new NO sensor demonstrated a satisfying performance for both in vitro and in vivo applications.