Different doses of sevoflurane facilitate and impair learning and memory function through activation of the ERK pathway and synthesis of ARC protein in the rat hippocampus.

BACKGROUND: Sevoflurane has been shown to stimulate or depress memory in adult rats; however, the cellular mechanism of this bidirectional effect has not been fully investigated. METHODS: We used an intra-hippocampal microinfusion of U0126 to suppress ERK activation. Male SD rats were randomly assigned to four groups: Sham, 0.11%SEV, 0.3%SEV and 0.3%+U0126. They received bilateral injections of U0126 or saline. Rats were anesthetized, and Inhibitory Avoidance (IA) training was performed immediately after anesthesia. The memory retention latency was observed 24 h later. In another experiment, the hippocampus was removed 45 min after IA training to assess ARC expression, the synapsin 1 protein levels and the phosphorylation level of ERK. RESULTS: Treatment with 0.11%SEV led to rapid phosphorylation of ERK, while 0.3%SEV inhibited phosphorylation; the latter change was reversed by the microinfusion of U0126 in the hippocampus. The memory latency result had similar tendencies. The local infusion of U0126 abolished the 0.3%SEV-induced memory impairment and ERK inhibition. Selective upregulations of ARC and synapsin 1 proteins were observed in the 0.3%SEV group compared with the 0.11%SEV group. CONCLUSIONS: The results indicate that different doses of sevoflurane trigger synaptic plasticity-related cytoskeleton proteins through the ERK signaling pathway. This novel modulation by inhalational agents may help to reduce their side-effects on memory function.

[Design of UV annular imaging system for atmospheric limb detection].

In order to meet the requirements of imaging the surrounding 360 degree scene at one time without rotating the optical system and satisfy the UV limb detecting, a panoramic imaging system was presented for atmospheric UV limb detection. First, considering the special working band and innovative application and proceeding from the basic principle of traditional panoramic annular lens, the curvature radius of four spherical surfaces was adjusted, combined with the detector size so that can get the best MTF. Then, based on the aberration theory, the relay lens system was designed to make up the aberration produced by panoramic annular lens. The separation of positive and negative lens combination with different refraction and Abbe number was used. The negative lens used fused silica, while the positive lens used calcium fluoride, so to correct the apochromatism. Finally, the optical system was optimized with CODE-V and the important tolerance parameters were listed, so that the subsequent processing can be requested. The design results show that the diameter of 80% encircled energy of UV panoramic limb imaging system is below 11 microm,which is smaller than the pixel size of CCD, and the MTF value of the system is higher than 0.7 @ 384 mm(-1) over all fields. These data satisfy the requirements of the system and prove the feasibility of panoramic imaging system in atmospheric UV limb detection.

The BDNF/TrkB signaling pathway is involved in heat hyperalgesia mediated by Cdk5 in rats.

BACKGROUND: Cyclin-dependent kinase 5 (Cdk5) has been shown to play an important role in mediating inflammation-induced heat hyperalgesia. However, the underlying mechanism remains unclear. The aim of this study was to determine whether roscovitine, an inhibitor of Cdk5, could reverse the heat hyperalgesia induced by peripheral injection of complete Freund's adjuvant (CFA) via the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling pathway in the dorsal horn of the spinal cord in rats. RESULTS: Heat hyperalgesia induced by peripheral injection of CFA was significantly reversed by roscovitine, TrkB-IgG, and the TrkB inhibitor K252a, respectively. Furthermore, BDNF was significantly increased from 0.5 h to 24 h after CFA injection in the spinal cord dorsal horn. Intrathecal adminstration of the Cdk5 inhibitor roscovitine had no obvious effects on BDNF levels. Increased TrkB protein level was significantly reversed by roscovitine between 0.5 h and 6 h after CFA injection. Cdk5 and TrkB co-immunoprecipitation results suggested Cdk5 mediates the heat hyperalgesia induced by CFA injection by binding with TrkB, and the binding between Cdk5 and TrkB was markedly blocked by intrathecal adminstration of roscovitine. CONCLUSION: Our data suggested that the BDNF-TrkB signaling pathway was involved in CFA-induced heat hyperalgesia mediated by Cdk5. Roscovitine reversed the heat hyperalgesia induced by peripheral injection of CFA by blocking BDNF/TrkB signaling pathway, suggesting that severing the close crosstalk between Cdk5 and the BDNF/TrkB signaling cascade may present a potential target for anti-inflammatory pain.

Inhibition of aberrant cyclin-dependent kinase 5 activity attenuates isoflurane neurotoxicity in the developing brain.

Aberrant CDK5 activity is implicated in a number of neurodegenerative disorders. Isoflurane exposure leads to neuronal apoptosis, and subsequent learning and memory defects in the developing brain. The present study was designed to examine whether and how CDK5 activity plays a role in developmental isoflurane neurotoxicity. Rat pups and hippocampal neuronal cultures were exposed to 1.5% isoflurane for 4 h. The protein and mRNA levels of CDK5, p35 and p25 were detected by western blot and QReal-Time PCR. CDK5 activity was evaluated in vitro using Histone H1 as a substrate. Roscovitine (an inhibitor of CDK5) was applied before isoflurane treatment, cleaved Caspase-3, Bcl-2, Bax, MEF2 and phospho-MEF2A-Ser-408 expressions were determined. Dominant-Negative CDK5 was transfected before isoflurane treatment. Neuronal apoptosis was evaluated by Flow cytometry (FCM) and TUNEL-staining. Cognitive functions were assessed by Morris water maze. We found that isoflurane treatment led to an aberrant CDK5 activation due to its activator p25 that was cleaved from p35 by calpain. Inhibition of CDK5 activity with Roscovitine enhanced Bcl-2, and decreased cleaved Caspase-3 and Bax expressions. In addition, isoflurane exposure resulted in a decrease of MEF2 and increase of phospho-MEF2A-Ser-408, which were rescued by Roscovitine or Dominant-Negative CDK5 transfection. Dominant-Negative CDK5 transfection also decreased the percentage of TUNEL-positive cells in isoflurane neurotoxicity. Moreover, Roscovitine remarkably alleviated the learning and memory deficits induced by postnatal isoflurane exposure. These results indicated that aberrant CDK5 activity-dependent MEF2 phosphorylation mediates developmental isoflurane neurotoxicity. Inhibition of CDK5 overactivation contributes to the relief of isoflurane neurotoxicity in the developing brain.

[Optimum design of imaging spectrometer based on toroidal uniform-line-spaced (TULS) spectrometer].

Based on the geometrical aberration theory, a optimum-design method for designing an imaging spectrometer based on toroidal uniform grating spectrometer is proposed. To obtain the best optical parameters, twice optimization is carried out using genetic algorithm(GA) and optical design software ZEMAX A far-ultraviolet(FUV) imaging spectrometer is designed using this method. The working waveband is 110-180 nm, the slit size is 50 microm x 5 mm, and the numerical aperture is 0.1. Using ZEMAX software, the design result is analyzed and evaluated. The results indicate that the MTF for different wavelengths is higher than 0.7 at Nyquist frequency 10 lp x mm(-1), and the RMS spot radius is less than 14 microm. The good imaging quality is achieved over the whole working waveband, the design requirements of spatial resolution 0.5 mrad and spectral resolution 0.6 nm are satisfied. It is certificated that the optimum-design method proposed in this paper is feasible. This method can be applied in other waveband, and is an instruction method for designing grating-dispersion imaging spectrometers.

Increased synaptophysin is involved in inflammation-induced heat hyperalgesia mediated by cyclin-dependent kinase 5 in rats.

Mechanisms associated with cyclin-dependent kinase 5 (Cdk5)-mediated heat hyperalgesia induced by inflammation remain undefined. This study was designed to examine whether Cdk5 mediates heat hyperalgesia resulting from peripheral injection of complete Freund's adjuvant (CFA) in the spinal dorsal horns of rats by interacting with synaptophysin, a well known membrane protein mediating the endocytosis-exocytosis cycle of synaptic vesicles as a molecular marker associated with presynaptic vesicle membranes. The role of Cdk5 in mediating synaptophysin was examined through the combined use of behavioral approaches, imaging studies, and immunoprecipitation following CFA-induced inflammatory pain. Results showed that Cdk5 colocalized with both synaptophysin and soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs) consisting of VAMP-2, SNAP-25, and syntaxin 1A in spinal dorsal horn of rats. Increased synaptophysin expression of spinal cord horn neurons post intraplantar injection of CFA coincided with increased duration of heat hyperalgesia lasting from 6 h to 3 d. Intrathecal administration of roscovitine, a Cdk5 specific inhibitor, significantly depressed synaptophysin expression during peak heat hyperalgesia and heat hyperalgesia induced by peripheral injection of CFA. Data presented in this report indicated that calpain activity was transiently upregulated 6 h post CFA-treatment despite previous reports suggesting that calpain was capable of cleaving p35 into p25. Results from previous studies obtained by other laboratories demonstrated that significant changes in p35 expression levels within spinal cord horn neurons were not observed in the CFA-treated inflammatory pain model although significant upregulation of Cdk5 kinase was observed between 2 h to 7 d. Therefore, generation of p25 occurred in a calpain-independent fashion in a CFA-treated inflammatory pain model. Our results demonstrated that increased synaptophysin levels were involved in heat hyperalgesia mediated by Cdk5 in spinal cord dorsal horns of CFA-treated rats, suggesting that inhibiting abnormal activation of Cdk5-synaptophysin may present a novel target for diminishing inflammatory pain.

Post-training intra-basolateral amygdala infusions of norepinephrine block sevoflurane-induced impairment of memory consolidation and activity-regulated cytoskeletal protein expression inhibition in rat hippocampus.

Considerable evidence indicates that the noradrenergic system of the basolateral amygdala (BLA) participates in the consolidation of various types of emotionally arousing memories. We previously reported that administration of an anesthetic-dose of sevoflurane immediately after continuous multiple-trail inhibition avoidance (CMIA) training impaired memory consolidation. This experiment investigated whether posttraining noradrenergic activation of the BLA is sufficient to reverse the memory impairing effect of sevoflurane. Adult male Sprague-Dawley rats received bilateral injections of norepinephrine (NE 0.3, 1.0, or 3.0 µg/0.5 µl) or normal saline (NS 0.5 µl) immediately after training in a CMIA paradigm. Subsequently, the rats were exposed to sevoflurane (2% inspired) or air for 2h. Norepinephrine produced a dose-dependent enhancement of memory consolidation on a 24-h retention test. The highest dose of NE tested (3.0 µg/0.5 µl) blocked sevoflurane-induced impairment of memory consolidation and reversed the inhibitory effect of sevoflurane on activity-regulated cytoskeletal protein (Arc) expression in the hippocampus 2h after training. These findings provide evidence that the mechanism mediating the memory-impairing effect of sevoflurane involves a network interaction between the BLA noradrenergic system and modulation of Arc protein expression in the hippocampus.

Sevoflurane impairs memory consolidation in rats, possibly through inhibiting phosphorylation of glycogen synthase kinase-3ß in the hippocampus.

Sevoflurane administration impairs memory processes in both humans and animals. Increasing evidence suggests that enhancement of the phosphorylation state of glycogen synthase kinase-3ß (GSK-3ß), as a result of acute administration of lithium chloride (LiCl), may enhance memory consolidation. The current experiments examined whether GSK-3ß phosphorylation was involved in mediating the memory impairing effects of posttraining sevoflurane on inhibitory avoidance (IA) retention. In experiment 1, adult male Sprague-Dawley rats were exposed to sevoflurane (0.5%, 1%, or 2%) for 2h immediately after training in a continuous multiple-trail IA paradigm. Sevoflurane (2% inspired) induced significant impairment of retention performance on a 24-h test and inhibited phosphorylation of GSK-3ß in the hippocampus 2h after training. In experiment 2, administration of LiCl (100mg/kg, intraperitoneally) 30 min before IA training not only blocked the sevoflurane-induced impairment of consolidation, but also reversed the inhibitory effect of sevoflurane on GSK-3ß phosphorylation in the hippocampus. Collectively, these findings support the hypothesis that sevoflurane exposure can impair consolidation of IA memory in rats. Sevoflurane-induced amnesia may be due, at least in part, to suppression of GSK-3ß phosphorylation in the hippocampus.

[Analysis and experimental validation of signal-to-noise for limb imaging spectrometer].

Limb imaging spectrometer is an important new remote sensor for research and application. Signal-to-noise ratio (SNR) is one of the key parameters to quantitatively evaluate the image quality and radiometric performance of an imaging spectrometer. The estimation and testing of SNR are very important for developing an imaging spectrometer. From the perspectives of radiative transmission and energy conversion, the SNR model is proposed, and the SNR equation of dispersive-type limb imaging spectrometer is derived, and the SNR values under several observing conditions for an limb imaging spectrometer prototype developed are theoretically evaluated based on atmospheric radiative transfer code MODTRAN 4.0. The results show that the SNR of the prototype under typical viewing geometry is not less than 8. As experimental validation, SNR testing was performed using an internally illuminated integrating sphere, and the experimental results have proved the correctness of this theoretical model.

Bilateral inhibition of gamma-aminobutyric acid type A receptor function within the basolateral amygdala blocked propofol-induced amnesia and activity-regulated cytoskeletal protein expression inhibition in the hippocampus.

BACKGROUND: It has been reported that bilateral lesions of the basolateral amygdala complex (BLA) blocked propofol-induced amnesia of inhibitory avoidance (IA) training. Based on these results, the authors hypothesized that the amnesia effect of propofol was partly due to its impairment of memory formation in the hippocampus through activating the BLA gamma-aminobutyric acid type A receptor function. The authors determined the changes in activity-regulated cytoskeleton-associated protein (Arc) expression to be an indicator of IA memory formation. METHODS: Male Sprague-Dawley rats received bilateral injection of bicuculline methiodide (10, 50, or 100 pmol/0.5 microl) or saline (0.5 microl) into the BLA. Fifteen minutes later, the rats were intraperitoneally injected with either propofol (25 mg/kg) or saline. After 5 min, the one-trial IA training was conducted. Rats intraperitoneally infused with saline served as controls and only received saline injections into the BLA. Twenty-four hours later, the IA retention latency was tested. Separate groups of rats treated the same way were killed either 30 min after IA training for hippocampal Arc mRNA measurement or after 45 min for protein level quantification. RESULTS: The largest dose of bicuculline methiodide (100 pmol) not only blocked the propofol-induced amnesia but also reversed the inhibition effect of propofol on Arc protein expression in the hippocampus (P < 0.05). However, the mRNA level of Arc showed no significant changes after propofol and bicuculline methiodide administration. CONCLUSIONS: The amnesic effect of propofol seems to involve the modulation of Arc protein expression in the hippocampus, occurring through a network interaction with the BLA.

Effects of ketamine, midazolam, thiopental, and propofol on brain ischemia injury in rat cerebral cortical slices.

AIM: To compare the effects of ketamine, midazolam, thiopental, and propofol on brain ischemia by the model of oxygen-glucose deprivation (OGD) in rat cerebral cortical slices. METHODS: Cerebral cortical slices were incubated in 2 % 2,3,5-triphenyltetrazolium chloride (TTC) solution after OGD, the damages and effects of ketamine, midazolam, thiopental, and propofol were quantitatively evaluated by ELISA reader of absorbance (A) at 490 nm, which indicated the red formazan extracted from slices, lactic dehydrogenase (LDH) releases in the incubated supernate were also measured. RESULTS: Progressive prolongation of OGD resulted in decreases of TTC staining. The percentage of tissue injury had a positive correlation with LDH releases, r=0.9609, P<0.01. Two hours of reincubation aggravated the decrease of TTC staining compared with those slices stained immediately after OGD (P<0.01). These four anesthetics had no effects on the TTC staining of slices. Ketamine completely inhibited the decrease of A value induced by 10 min of OGD injury. High concentrations of midazolam (10 micromol/L) and thiopental (400 micromol/L) partly attenuated this decrease. Propofol at high concentration (100 micromol/L) enhanced the decrease of A value induced by 10 min of OGD injury (P<0.01). CONCLUSION: Ketamine, high concentration of midazolam and thiopental have neuroprotective effects against OGD injury in rat cerebral cortical slices, while high concentration of propofol augments OGD injury in rat cerebral cortical slices.

[The influences of propofol on different kinds of brain injuries in rat brain slices].

OBJECTIVE: To investigate the effects of propofol on the three kinds of brain injuries induced by metabolic disorder, neurotoxicity of excitatory amino acid, and oxygen-derived free radicals in rat cerebral cortical and hippocampal slices. METHODS: Slices of rat cerebral cortex and hippocampus were made and incubated in normal artificial cerebrospinal fluid (nACSF). Then the rat cerebral cortical and hippocampal slices were divided into 2 categories: propofol group, the slices in which were co-incubated with 5, 50, or 100 micro mol/L propofol for 3 hours, and 3 experimental injury groups. Each experimental injury group was further subdivided into 3 subgroups including the slices of 4 rats. Two hours after normal incubation the slices were co-incubated with 2,3,5-triphenyltetrazolium chloride (TTC). Formazan, the red crystal product were extracted, and ELISA reader was used to read the absorbance at 490 nm (A(490)) so as to quantitatively evaluate the degree of injury. RESULTS: The values of A(490) of the slices co-incubated with propofol of different concentrations were not significantly different. Compared with those of the control subgroups, the values A490 were significantly decreased in the cerebral cortical and hippocampus slices damaged by OGD, glutamate, and H(2)O(2) injuries (all P < 0.01). The values of A(490) in the subgroups of low and middle concentrations (5 and 50 micro mol/L) of propofol plus OGD or glutamate injury were not significantly different from those of the subgroups of OGD or glutamate injury alone, both in cerebral cortical and hippocampal slices. However, the values of A(490) in the subgroups of high concentration of propofol (100 micro mol/L) plus OGD or glutamate injury was further decreased (P < 0.01). The values of A(490) in the subgroups of low and middle concentrations of propofol plus H(2)O(2) injury were significantly higher than those of the injury subgroup (all P < 0.01), however, however, the values of A490 in the high concentration propofol plus H(2)O(2) injury subgroup were significantly lower than those of the control group (all P < 0.01), even lower than that of the subgroup of H(2)O(2) injury alone. CONCLUSION: Propofol has a neuroprotective effect against hydrogen peroxide injury at low and middle concentrations. Propofol of low and middle concentrations does not improve the decrease of the value of A(490). however, propofol of high concentration augments the oxygen-glucose deprivation and glutamate injuries both in the rat cerebral cortical slices and hippocampal slices.

[The role of neuronal nicotinic acetylcholine receptors in the mechanisms of general anesthesia].

Neuronal nicotinic acetylcholine receptors (nnAChRs) are members of the ligand-gated ion channel superfamily, and widely expressed in the central and peripheral nervous systems with many subunits. NnAChRs have been represented novel targets for a wide variety of therapeutic agents based on their complex functions. It is known that both central and peripheral nnAChRs are sensitive to various types of general anesthetics, among those, barbiturates, ketamine, volatile and gaseous anesthetics depress nnAChRs at or below clinical concentrations. It is possible that inhibition of nnAChRs is one of factors involved in the mechanisms of general anesthesia.