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1.
Subunit composition of voltage- and Ca2+-sensitive high-conductance K+ channels (BK channels) in dentate gyrus (DG) of Krushinskii-Molodkina (KM) rats, genetically prone to audiogenic seizures, was compared with that of normal Wistar rats, resistant to sound effects. Additionally, long-lasting changes in protein expression of α- and β4-subunits in DG of KM rats after audiogenic kindling (model of temporal lobe epilepsy) was investigated. Western blot analysis revealed no differences between the levels of the pore-forming α-subunit expression in DG of KM and Wistar rats. In contrast, the level of brain-specific auxiliary β4-subunit in DG of KM rats was increased twofold in comparison to that in Wistar rats. It is likely that the observed changes in the BK channel α/β4 subunits ratio can prevent the development of excessive neuronal exitability in DG of KM rats. The results obtained on the model of audiogenic kindling (20 convulsion fits) confirmed this assumption. Thus, α-subunit expression levels in DG of KM rats on day 3 and 14 after the last seizure were increased 2.5 times in comparison with intact KM rats. The expression level of β4 in DG of KM rats 3 days after kindling was reduced to 30% of the control level. On day 14 after finishing audiogenic kindling, a further reduction of β4 protein expression level occurred. We suggest that the changes in the subunit composition of BK channels in DG following chronic seizures can alter functional properties of DG as a physiological filter, which normally prevents the propagation of epileptiform activity in the hippocampus.  相似文献   

2.
The influence of cortisone (1.5 mg per 100 g of body weight, daily, for 10 days) on the neuro-muscular system was studied in rats in situ. The action potentials of the nerve and muscle were recorded with the extracellular electrodes. The rest potentials (RP) of the muscle fibers and the miniature end-plate potentials (MEPP) were recorded with the intracellular glass microelectrodes. A decrease of the RP and the MEPP amplitude, and an increase of the MEPP frequency and prolongation of the neuromuscular transmission time were revealed in rats given daily doses of cortisone, 1.5 mg/100 g of body weight, during 10 days; reliability of the neuro-muscular transmission (acceleration of the fall of the muscle action potential amplitude during tetanus) proved to decrease under the action of cortisone.  相似文献   

3.
Previous studies indicate that Long-Evans rats can be operantly trained to discriminate inspired CO(2) concentrations as low as 0.5%. This ability has been proposed to be due to the presence of CO(2)-sensitive olfactory receptors that contain the enzyme carbonic anhydrase (CA). The objectives of the present study were as follows: 1) to determine whether Zucker rats could be operantly conditioned to discriminate low concentrations of CO(2) from control air and 2) to determine the rats' CO(2) detection thresholds before and after nasal perfusion of mammalian Ringers or methazolamide, a CA inhibitor. Rats were operantly trained to discriminate between 25% CO(2) and control air (0% CO(2)) and were then subjected to various CO(2) concentrations (0.5-12.5%) to determine their CO(2) detection thresholds. The average (+/-standard error of mean) baseline CO(2) detection threshold of 7 Zucker rats was 0.48 +/- 0.07% CO(2), whereas the average CO(2) detection thresholds after nasal perfusion of either mammalian Ringers or 10(-2) M methazolamide were 1.41 +/- 0.30% and 5.92 +/- 0.70% CO(2), respectively. The average CO(2) detection threshold after methazolamide was significantly greater (P<0.0001) than the baseline detection threshold. These findings demonstrate that like Long-Evans rats, Zucker rats can be trained to discriminate low concentrations of CO(2) and that inhibition of nasal CA reduces the ability of the rats to detect low concentrations (3.5% and below) but not higher concentrations of CO(2) (12.5%). These results add to the growing evidence that olfactory neurons exhibiting CA activity are CO(2) chemoreceptors sensitive to physiological concentrations of CO(2).  相似文献   

4.
The meridian phenomena are closely associated with the neuro-muscular function. Our experiments show that meridian phenomenon, acupoint stimulation-induced generating-sensations along meridians (GSM), does exist in some volunteers, and the subjects can describe the characteristics of the feelings and the route of GSM. Simultaneously, GSM is often accompanied with progressive myoelectric activity along the meridian which is able to be recorded objectively. Brachial plexus anesthesia and regional neuro-muscular block may arrest these responses while the neuro-muscular blocking agent may stop neuromuscular transmission at the motor end-plate rather than check GSM. The facts reveal that GSM probably depends on muscular activity and is involved in the secondary neuro-muscular excitation propagating along the longitudinal axis of muscles. These findings suggest that the myoelectric activities constitute the foundation of secondarily generating-sensation propagating along the longitudinal orientation of limbs (muscles), or along the meridian.  相似文献   

5.
6.
Sublethal stress stimuli such as systemic endotoxin treatment can induce tolerance of the brain to subsequent ischemic stress, which results in a decreased infarct size. Based on this evidence, we hypothesized that lipopolysaccharide (LPS)-induced preconditioning could protect hippocampal neurons in epileptic rats. To test this hypothesis, the anticonvulsant effect of a low dose of LPS against seizures elicited by pilocarpine hydrochloride was measured. Using the pilocarpine model of temporal lobe epilepsy and LPS-preconditioning, we also investigated hippocampal pathology in the rat brain. Based on the behavioural observations conducted, it can be assumed that the preconditioning procedure used may decrease seizure excitability in epileptic rats. However, determination of the seizure excitability threshold needs to be elaborated. Qualitative and quantitative analyses of histological brain sections in the LPS-preconditioned rats showed markedly decreased intensity of neurodegenerative changes in the CA1, CA3 and DG hippocampal fields. The tendency was observed in all the periods of the pilocarpine model of epilepsy. We suggest that preconditioning with LPS may have neuroprotective effects in the CA1, CA3 and DG hippocampal sectors; however, it has no influence on the course of the seizures in rats in the pilocarpine model of epilepsy.  相似文献   

7.

In most vertebrates, red blood cell carbonic anhydrase (RBC CA) plays a critical role in carbon dioxide (CO2) transport and excretion across epithelial tissues. Many early-diverging fishes (e.g., hagfish and chondrichthyans) are unique in possessing plasma-accessible membrane-bound CA-IV in the gills, allowing some CO2 excretion to occur without involvement from the RBCs. However, implications of this on RBC CA function are unclear. Through homology cloning techniques, we identified the putative protein sequences for RBC CA from nine early-diverging species. In all cases, these sequences contained a modification of the proton shuttle residue His-64, and activity measurements from three early-diverging fish demonstrated significantly reduced CA activity. Site-directed mutagenesis was used to restore the His-64 proton shuttle, which significantly increased RBC CA activity, clearly illustrating the functional significance of His-64 in fish red blood cell CA activity. Bayesian analyses of 55 vertebrate cytoplasmic CA isozymes suggested that independent evolutionary events led to the modification of His-64 and thus reduced CA activity in hagfish and chondrichthyans. Additionally, in early-diverging fish that possess branchial CA-IV, there is an absence of His-64 in RBC CAs and the absence of the Root effect [where a reduction in pH reduces hemoglobin’s capacity to bind with oxygen (O2)]. Taken together, these data indicate that low-activity RBC CA may be present in all fish with branchial CA-IV, and that the high-activity RBC CA seen in most teleosts may have evolved in conjunction with enhanced hemoglobin pH sensitivity.

  相似文献   

8.
Unsubstituted aromatic, heterocyclic and perfluoroalkylic sulfonamides possessing the general formula RSO 2 NH 2 act as powerful inhibitors of the zinc enzyme carbonic anhydrase (CA). Unsaturated primary/substituted sulfonamides have never been investigated for their interaction with the enzyme. Here it is shown that such compounds, and more precisely allyl-sulfonamide and trans -styrene sulfonamide possessing the above general formula (with R=CH 2 =CH-CH 2 - and C 6 H 5 -CH=CH-, respectively) behave as nanomolar inhibitors of the physiologically relevant isozymes CA I and CA II. Some other derivatives of these two leads (incorporating Si(IV), Ge(IV) and B(III) moieties among others) were also synthesized and investigated for their interaction with CA, but showed decreased affinity for both isozymes. The structure-activity relationship for this class of CA inhibitors is discussed. Furthermore, it was observed that allylsulfonyl chloride is a strong CA inactivator, probably by reacting with amino acid residues critical for the catalytic cycle.  相似文献   

9.
Unsubstituted aromatic, heterocyclic and perfluoroalkylic sulfonamides possessing the general formula RSO2NH2 act as powerful inhibitors of the zinc enzyme carbonic anhydrase (CA). Unsaturated primary/substituted sulfonamides have never been investigated for their interaction with the enzyme. Here it is shown that such compounds, and more precisely allyl-sulfonamide and trans-styrene sulfonamide possessing the above general formula (with R=CH2=CH-CH2- and C6H5-CH=CH-, respectively) behave as nanomolar inhibitors of the physiologically relevant isozymes CAI and CAII. Some other derivatives of these two leads (incorporating Si(IV), Ge(IV) and B(III) moieties among others) were also synthesized and investigated for their interaction with CA, but showed decreased affinity for both isozymes. The structure-activity relationship for this class of CA inhibitors is discussed. Furthermore, it was observed that allylsulfonyl chloride is a strong CA inactivator, probably by reacting with amino acid residues critical for the catalytic cycle.  相似文献   

10.
Hind-limb perfusion was used to investigate alterations of alpha and beta receptor-mediated metabolic effects in cold-adapted (CA) rats. The response to beta receptor stimulation by isoproterenol in the isolated hind-limbs of CA rats was slightly diminished. Oxygen consumption and lactate production were reduced in CA rats after beta receptor stimulation. Noradrenalin infusion caused less vasoconstriction in CA rats than in the controls (CO). Desensitization of alpha and beta receptors due to chronic sympathetic overstimulation may be the underlying cause of these observations. Compared with the controls, metabolism was enhanced in perfused hind-limbs of CA rats with an active nervous system. Decreased vascular resistance due to the lower perfusion pressure in CA rats might contribute to this increased metabolism.  相似文献   

11.

Introduction

Cardiac arrest (CA) and hemorrhagic shock (HS) are two clinically relevant situations where the body undergoes global ischemia as blood pressure drops below the threshold necessary for adequate organ perfusion. Resistance to ischemia/reperfusion (I/R) injury is a characteristic of hibernating mammals. The present study sought to determine if arctic ground squirrels (AGS) are protected from systemic inflammation and multi organ damage after CA- or HS-induced global I/R and if, for HS, this protection is dependent upon their hibernation season.

Methods

For CA, rats and summer euthermic AGS (AGS-EU) were asphyxiated for 8 min, inducing CA. For HS, rats, AGS-EU, and winter interbout arousal AGS (AGS-IBA) were subject to HS by withdrawing blood to a mean arterial pressure of 35 mmHg and maintaining that pressure for 20 min before reperfusion with Ringers. For both I/R models, body temperature (Tb) was kept at 36.5–37.5°C. After reperfusion, animals were monitored for seven days (CA) or 3 hrs (HS) then tissues and blood were collected for histopathology, clinical chemistries, and cytokine level analysis (HS only). For the HS studies, additional groups of rats and AGS were monitored for three days after HS to access survival and physiological impairment.

Results

Rats had increased serum markers of liver damage one hour after CA while AGS did not. For HS, AGS survived 72 hours after I/R whereas rats did not survive overnight. Additionally, only rats displayed an inflammatory response after HS. AGS maintained a positive base excess, whereas the base excess in rats was negative during and after hemorrhage.

Conclusions

Regardless of season, AGS are resistant to organ damage, systemic inflammation, and multi organ damage after systemic I/R and this resistance is not dependent on their ability to become decrease Tb during insult but may stem from an altered acid/base and metabolic response during I/R.  相似文献   

12.
A stable isotope dilution method is described that allows measurement of cholic acid (CA) kinetics, that is, pool size, fractional turnover rate (FTR), and synthesis rate in mice, rats, and humans. Decay of administered [2,2,4,4-2H4]CA enrichment was measured in time in 50-microl plasma samples by gas-liquid chromatography/electron capture negative chemical ionization-mass spectrometry, applying the pentafluorobenzyl-trimethylsilyl derivative. The kinetic data expressed species-dependent differences. The CA pool sizes were 16.8 +/- 2.1, 10.6 +/- 1.2, and 2.4 +/- 0.7 micromol/100 g body weight for mice, rats, and humans, respectively. The FTR values were 0.44 +/- 0.03, 0.88 +/- 0.10, and 0.46 +/- 0.14 per day for mice, rats, and humans. The corresponding synthesis rates were 7.3 +/- 1.6, 9.3 +/- 0.1, and 1.0 +/- 0.2 micromol/100 g body weight per day. The human data agreed well with literature data obtained by conventional isotope dilution techniques. For rats and mice these are the first reported isotope dilution data. The method was validated by confirmation of isotopic equilibrium between biliary CA and plasma CA in the rat. Its applicability was demonstrated by the observation of increased CA FTR and CA synthesis rate in rats fed cholestyramine, which is known to increase fecal bile acid excretion. The presented stable isotope dilution method enables the determination of CA kinetic parameters in small plasma samples. The method can be applied in unanesthetized rodents with an intact enterohepatic circulation and may also be valuable when studying the development of human neonatal bile acid kinetics.  相似文献   

13.
Electrically evoked hippocampal afterdischarges are used as a model of partial epileptic seizures with a complex symptomatology and for testing anticonvulsants and toxic substances. Stimulating electrodes were implanted in the dorsal hippocampus of 16 laboratory rats and when the animals had recovered they were stimulated (15-s series, 8 Hz, pulse length 1 ms) with a voltage double the threshold value for a tissue response. The following features of the evoked afterdischarge were evaluated: the duration of the first phase of the afterdischarge, the duration of the non-active interphase, the duration of the second phase and the number of "wet dog shakes" (a constant accompaniment of hippocampal afterdischarges). Localization of the electrodes in the CA1 (n = 7) and CA3 (n = 7) region of the hippocampus made no difference to these parameters and in both cases the measured and evaluated data were the same. The afterdischarges were always accompanied by a marked orientation reaction. The study showed that when using macroelectrodes to stimulate the dorsal hippocampus, their localization in the CA1/CA3 is not of critical importance.  相似文献   

14.
We studied the effect of different levels of hypoxia (10, 12 or 13, 15, and 18% O2) on the sleep-waking pattern (SWP) and the maximum-minimum core temperature of warm-acclimated (WA) and cold-acclimated (CA) rats at their neutral temperature, 29 degrees C. Whereas the SWP of WA rats showed a trend toward increasing disruption as the degree of hypoxia increased, CA rats exhibited no such trend. The effect was chiefly on the frequency of state changes and less on epoch durations. The SWP of WA rats was more vulnerable to hypoxia than that of CA rats. Maximum and minimum body temperatures of WA and CA rats were not significantly affected by O2 lack down to 10% inspired O2. We conclude that in the rat 1) hypoxia primarily affects the neural mechanism that governs the frequency of changes in sleep-waking states; 2) the extent of alterations in SWP's depends on the ambient temperature to which the rats are acclimated; and 3) hypoxia does not significantly affect deep body temperature at the animal's neutral temperature.  相似文献   

15.
Abstract: Chronic administration of ethanol to rats on an intermittent regimen, for 60 repeated intoxicating doses and repeated withdrawal episodes, results in a long-lasting kindling phenomenon. This involves an increasing severity of withdrawal, including a reduced threshold to seizures produced by the GABAA antagonist, pentylenetetrazol. We have shown previously that muscimol-evoked 36Cl efflux and paired-pulse inhibition (involving GABAA-mediated recurrent inhibition) were decreased persistently in the CA1 region of hippocampal slices from chronic intermittent ethanol (CIE)-treated rats. We now report elevated levels of mRNA in forebrain for the α4 subunit of the GABAA receptor (GABAR), considered to be a constituent of pharmacologically and physiologically novel subtypes of GABARs. Using in situ hybridization with digoxigenin-labeled RNA probes, we show that at 2 days withdrawal, 60-dose CIE leads to a significant 30% increase in α4 subunit mRNA levels in the dentate gyrus, 46% increase in the CA3, and 26% increase in the CA1 regions. In contrast, there was no significant change in the mRNAs for the α5 subunit or glutamic acid decarboxylase 67 in the same regions. This study suggests that GABAR subunit-selective alterations occur after CIE treatment, possibly resulting in the alteration of the subunit composition of GABARs, with presumably altered physiological functions. This plasticity of GABARs may contribute to the increased withdrawal severity, reduced hippocampal inhibition, and increased seizure susceptibility of this animal model of human alcohol dependence.  相似文献   

16.
Combretastatin A-4 disodium phosphate (CA4P) is a vascular disrupting agent known to mediate its effects primarily on tumor blood vessels. CA4P has previously been shown to induce a significant increase in mean arterial blood pressure and in hemoglobin concentration in mice. In the present study, we examined whether this is associated with a general leakage of water into certain tissues or with changes in renal water handling. Munich-Wistar rats received either CA4P (30 mg/kg body wt) or saline intraperitoneally as a bolus injection. One hour later, hemoglobin concentration and mean blood pressure increased significantly. MRI showed no significant changes in tissue water content following CA4P administration. However, urine output and salt excretion increased 1 h after CA4P treatment, without changes in urinary and medullary osmolality. Aquaporin 2 (AQP2) mRNA levels in kidney inner medulla did not change 1 h after CA4P treatment, but semiquantitative confocal laser-scanning microscopy analysis demonstrated a decrease in phosphorylated AQP2 (pS256-AQP2) apical distribution within the collecting ducts of CA4P-treated rats compared with the characteristic apical localization in control rats. Furthermore, we demonstrated that CA4P cause disruption of microtubules and a weaker apical labeling of pS256-AQP2 in collecting duct principal cells within 1 h. In conclusion, our data indicate that water escapes from the vascular system after CA4P treatment, and it may take place primarily through a renal mechanism. The CA4P-mediated increase in urine output seems to be a local effect in the collecting ducts due to reduced AQP2 trafficking to the apical plasma membrane.  相似文献   

17.
Evidence for increased calpain activity has been described in the hippocampus of rodent models of temporal lobe epilepsy. However, it is not known whether calpains are involved in the cell death that accompanies seizures. In this work, we characterized calpain activation by examining the proteolysis of calpain substrates and in parallel we followed cell death in the hippocampus of epileptic rats. Male Wistar rats were injected with kainic acid (10 mg/kg) intraperitoneally and killed 24 h later, after development of grade 5 seizures. We observed a strong Fluoro-Jade labeling in the CA1 and CA3 areas of the hippocampus in the rats that received kainic acid, when compared with saline-treated rats. Immunohistochemistry and western blot analysis for the calpain-derived breakdown products of spectrin showed evidence of increased calpain activity in the same regions of the hippocampus where cell death is observed. No evidence was found for caspase activation, in the same conditions. Treatment with the calpain inhibitor MDL 28170 significantly prevented the neurodegeneration observed in CA1. Taken together, our data suggest that early calpain activation, but not caspase activation, is involved in neurotoxicity in the hippocampus after status epilepticus .  相似文献   

18.
The meridian phenomena are closely associated with the neuro-muscular function. Our experiments show that meridian phenomenon, acupoint stimulation-induced generating-sensations along meridians (GSM), does exist in some volunteers, and the subjects can describe the characteristics of the feelings and the route of GSM. Simultaneously, GSM is often accompanied with progressive myoelectric activity along the meridian which is able to be recorded objectively. Bra-chial plexus anesthesia and regional neuro-muscular block may arrest these responses while the neuro-muscular blocking agent may stop neuromuscular transmission at the motor end-plate rather than check GSM. The facts reveal that GSM probably depends on muscular activity and is involved in the secondary neuro-muscular excitation propagating along the longitudinal axis of muscles. These findings suggest that the myoelectric activities constitute the foundation of secondarily generating-sensation propagating along the longitudinal orientation of limbs  相似文献   

19.
Glucocorticoid-glutamatergic interactions have been proposed as a potential model to explain stress-mediated impairment of cognition. However, it is unknown whether glucocorticoid-zincergic interactions are involved in this impairment. Histochemically reactive zinc (Zn(2+)) is co-released with glutamate from zincergic neurons. In the present study, involvement of synaptic Zn(2+) in stress-induced attenuation of CA1 LTP was examined in hippocampal slices from young rats after exposure to tail suspension stress for 30s, which significantly increased serum corticosterone. Stress-induced attenuation of CA1 LTP was ameliorated by administration of clioquinol, a membrane permeable zinc chelator, to rats prior to exposure to stress, implying that the reduction of synaptic Zn(2+) by clioquinol participates in this amelioration. To pursue the involvement of corticosterone-mediated Zn(2+) signal in the attenuated CA1 LTP by stress, dynamics of synaptic Zn(2+) was checked in hippocampal slices exposed to corticosterone. Corticosterone increased extracellular Zn(2+) levels measured with ZnAF-2 dose-dependently, as well as the intracellular Ca(2+) levels measured with calcium orange AM, suggesting that corticosterone excites zincergic neurons in the hippocampus and increases Zn(2+) release from the neuron terminals. Intracellular Zn(2+) levels measured with ZnAF-2DA were also increased dose-dependently, but not in the coexistence of CaEDTA, a membrane-impermeable zinc chelator, suggesting that intracellular Zn(2+) levels is increased by the influx of extracellular Zn(2+). Furthermore, corticosterone-induced attenuation of CA1 LTP was abolished in the coexistence of CaEDTA. The present study suggests that corticosterone-mediated increase in postsynaptic Zn(2+) signal in the cytosolic compartment is involved in the attenuation of CA1 LTP after exposure to acute stress.  相似文献   

20.
目的通过观察2型糖尿病大鼠海马CA1区神经生长因子(NGF)和胆碱乙酰转移酶(ChAT)表达的改变,研究花生油对2型糖尿病大鼠海马神经元NGF及ChAT表达的影响,探讨花生油在防治糖尿病脑病中的作用。方法 60只健康雄性SD大鼠随机分为4组:正常对照组(C组)、2型糖尿病组(T2DM组)、2型糖尿病给予2 mL花生油组(T2DM+2 mL组)及2型糖尿病给予5 mL花生油组(T2DM+5 mL组)。其中C组给予正常饮食,糖尿病组大鼠给予高脂饮食喂养,2个月后,按25 mg/kg体质量腹腔注射链脲佐菌素(STZ)制成2型糖尿病模型,T2DM组、T2DM+2 mL组及T2DM+5 mL组大鼠继续给予高脂饮食。糖尿病造模1个月后处死全部大鼠,行脑冰冻切片,用免疫组织化学方法检测各组大鼠海马CA1区NGF和ChAT的表达。结果 (1)T2DM组大鼠海马CA1区NGF表达比C组明显降低(P〈0.05),T2DM+2 mL组及T2DM+5 mL组大鼠海马CA1区NGF表达均明显高于未给予花生油的T2DM组(P〈0.05)。(2)T2DM组大鼠海马CA1区ChAT表达显著低于C组(P〈0.05),T2DM+2 mL组和T2DM+5 mL组大鼠海马CA1区ChAT表达均明显高于未给予花生油的T2DM组(P〈0.05)。结论 2型糖尿病大鼠海马CA1区神经生长因子表达降低,胆碱能神经元数量减少,这可能是2型糖尿病脑病发生的原因之一。花生油能增加2型糖尿病大鼠海马区内神经生长因子表达,促进胆碱能神经元存活,表明花生油具有一定的保护大鼠糖尿病脑病的作用。  相似文献   

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