Spontaneous and orienting-exploratory motor activity in rats with hereditary arterial hypertension

In rats of spontaneously hypertensive line (SHR) in comparison with normotensive animals of WKY line an increased activity was revealed in new surroundings in conditions of open illuminated space, and reduced activity in limited darkened space with weakened extinction of activity. Male SHR rats had a higher daily motor activity and SHR females--a lower level of defecation. The revealed behavioural changes testify to an enhancement of investigatory motivation and weakening of "fear" in SHR rats as well as to increased excitatory and decreased inhibitory processes in these animals. Behavioural characteristics of SHR rats reflect an increased reactivity of their nervous system which may be connected with the mechanisms of the increase of arterial pressure.     

The exploratory behavior in an open field and in a burrowing chamber of rats with different predispositions to stress]

The peculiarities of oriental research behavior and correlation between activities of catecholaminergic and serotoninergic brain systems dependently on their stress resistance degree were investigated in Wistar rats. The experiments showed that resistant (R) to a sound stimulus rats differed from nonresistant (NR) ones by increased research activity under moderate stress in the open field test and by decreased research behavior level in the cell chamber test. The biochemical analysis of biogenic amines in different brain structures revealed increased norepinephrine levels in stress R rats, and increased dopamine and serotonin levels in NR ones. The findings suggest that inborn behavior regulation in animals with different stress resistance is determined by different correlations between serotonin-dopamine and norepinephrine brain systems activities.     

Data on lipid metabolism in the genetically obese Zucker rat

We assayed various lipid fractions as well as some intermediate metabolites and adenine nucleotides in the liver and the blood of the genetically obese Zucker rat (fa/fa) and compared their values with the corresponding ones obtained for nonobese controls and for Sprague-Dawley rats.Results for the two latter groups were similar, and differed greatly from those for the obese rats. The obese rats had hepatomegaly due mainly to high levels of triglycerides. The plasma of the obese animals contained high levels of triglycerides, phospholipids, cholesterol, and nonesterified fatty acids. Obese rats had slightly higher levels of ketone bodies than nonobese rats. In the liver of obese rats, we observed a decreased level of citrate/g and an elevated malate level. Levels of adenine nucleotides were similar in all rats.     

Learning in rats with differing emotional responsiveness and its relation to brain monoamines

The ability for learning was studied in two groups of Wistar line rats divided by susceptibility to the audiogenic stress-stimulation as compared with the monoamines level in various brain structures. The best ability to learn avoidance reaction in a shuttlebox was shown by animals non-resistant to the stress stimulus as compared with the resistant rats, which correlated positively with the exploratory activity in "the open field". The distinct feature of the animals non-resistant to the stress stimulation consisted in a higher reactivity of the monoamine systems, mainly of the noradrenergic system. This group of animals was also characterized by a higher dopamine content and a lower noradrenaline content in the brain-stem. Decreased activity of the brain dopamine-beta-hydroxylase in animals non-resistant to the stress stimulus, has been suggested.     

Juvenile social subjugation induces a sex-specific pattern of anxiety and depression-like behaviors in adult rats

Child abuse is the most significant environmental risk factor for the development of mood disorders, which occur twice as frequently in women as in men. To determine whether juvenile social subjugation (JSS) of rats induces mood disorder-like symptoms, we exposed 28 day-old male and female rats to daily aggressive acts from aggressive male residents. Each rat received pins, kicks, and dominance postures from the resident for 10 min per day for 10 days. When the rats were adults, we tested their anxiety- and depression-like behaviors. In addition, we measured circulating basal and stress-evoked corticosterone (CORT) levels, and weighed the adrenal glands. Although the amount of JSS was indistinguishable between males and females, females were nonetheless more severely affected by the experience. Subjugated females became immobile more quickly during forced swim tests, and made fewer investigatory approaches during the social interaction test than control females. Juvenile social subjugation increased closed arm time in the elevated plus maze of males and females, but the effect of social subjugation was greater in females. Finally, stress-evoked CORT levels were significantly higher, and adrenal gland weights were significantly heavier, in subjugated females relative to their controls and to subjugated males. Our results demonstrate that JSS increases depression- and anxiety-like behaviors and sensitizes the stress response system in a sex-specific manner.     

Genetic predisposition to catatonic behaviour and methylphenidate sensitivity in rats

To study the relationship between three animal models of schizophrenia, i.e. genetically determined akinetic catatonia, stereotypies induced by amphetamine-like psychostimulators, and behavioural changes in chronic intoxication with such stimulators, the frequency of different types of reactions to a functional amphetamine analogue, methylphenidate, was studied in wild Norway rats, non-selected Wistar rats, and Wistar rats bred for predisposition to akinetic catatonia. A positive relationship between the predisposition to catatonia and the level of stereotypies in a single methylphenidate administration was found in wild rats, but not in Wistar bred for catatonia (the latter differed from the non-selected rats in a higher frequency of “hyperactive” reactions). A closer study of catatonia in laboratory rats permitted subdivision into several types—occurring in selected and non-selected rats both naturally and as a result of chronic intoxication with amphetamines. It was found in non-selected Wistar rats that there is a positive relationship between some of these types and an increased stereotypy level in repeated methylphenidate administration. It is concluded that the natural akinetic catatonia and the chronic intoxication with amphetamines are two homologous varieties of the same model of schizophrenia, while the stereotypies are characteristics of this model. Studies of monoamine oxidase (MAO) activity imply a cortical component in the predisposition to akinetic catatonia.     

The dynamic behavioral changes in rats after destruction of the locus coeruleus]

Destruction of locus coeruleus (LC) was conducted in adult rats (male rats of the Wistar line, 250-300 g) electrolytically or by means of 6-hydroxydopamine (6-OHDA). Behaviour of the intact animals sham-operated and of rats with destructed LC was evaluated before and every week after the operation during 5 weeks. Statistically significant alterations in the behaviour were revealed only in the initially low-active rats. These animals were characterized firstly, by low motor and exploratory activity in all tests (open field and automated devices), disturbance of the reactivity to novelty--only in one week after the operation with subsequent compensation of shifts; secondly, by low level of investigatory activity in the open field and absence of habituation to the repetitive tests--from the 21-st day after the operation.     

Rat behavior in a light/dark chamber: place preference task

After a 6-week social isolation (from 22nd to 70th day from birth) male Wistar rats (a sibship, 10 animals), were tested for 20 min in a light/dark box in order to reveal behavioral features of choice of their spatial localization in unknown conditions. Socially deprived rats significantly differed from control animals in longer time of the room choice, higher number of entries of the light section, and higher number of rearings, which was probably explained by their higher anxiety and lack of experience to estimate unexpected stimuli and select a response. The mean level of behavioral activity during exploration of the box defined by the number of elementary operations per minute remained constant and was significantly higher in the socially deprived rats than in the control animals.     

Object familiarization and novel-object preference in rats

We investigated whether object familiarization was related to novel-object preference in the novel-object preference (NOP) test in rats. In Experiment 1, we found that no significant correlation existed between the time spent investigating 2 identical copies of a sample object and the degree of preference for a novel object. In Experiment 2, rats investigated 2 identical sample objects for a total of 5, 30, 60, 90 or 120 s. Investigatory preference for the novel object was compared to chance expectancy as well as between the groups. Only the 90-s group and the 120-s group displayed above-chance investigatory preference for the novel object, but novel-object preference for these 2 groups did not differ from each other, suggesting that a minimal amount of sample object investigation is necessary for rats to develop a novel-object preference, beyond which no increase in novel-object preference was found. In Experiments 3 and 4, normal rats and rats with hippocampal lesions were given repeated test trials, with the same sample object presented with a different novel object, at 24-h and (Experiment 3) and 35-s intervals (Experiment 4). In both experiments, novel-object preference did not increase in magnitude with repeated sample object exposures, suggesting that increased familiarity with the sample object does not result in increased novel-object preference. Rats with lesions of the dorsal hippocampus showed an unreliable investigatory preference for the novel object. These results are discussed in terms of the potential limitations of the NOP test as a tool for the assessment of object-recognition memory in rats.     

Differences in the capacity of male odours to affect investigatory behaviour and different urinary marking patterns in two strains of mice,selectively bred for high and low aggressiveness.

The investigatory behaviour of male and female mice on sawdust soiled by male mice with different levels of aggressiveness was studied in two experiments. To investigate whether high and low aggressive males show different urinary marking patterns, a third experiment was set up. The strains TA(Turku Aggressive) and TNA (Turku Nonaggressive) have been developed by selective breeding. The TA-soiled bedding discouraged investigation by male mice, while females avoided TNA-soiled areas. Also the urine marking patterns differed between the high aggressive TA and low aggressive TNA males. The results indicate that the urine marking behaviour and the odour communication system in the TA and TNA males correlate with their hereditarily determined disposition for aggressive behaviour.     

The effect of gonadectomy on interhemispheric asymmetry in rats

The influence was studied of the gonadectomy in the newborn and mature male and female rats on functional interhemispheric asymmetry of the reaction of avoidance of pain scream of another rat ("emotional resonance"), and motor and investigatory activity in the open field. Consecutive inactivation of the hemispheres was realized by K+ spreading depression. It has been shown that neonatally gonadectomized rats have no interhemispheric asymmetry of the studied reactions. In male rats gonadectomized in mature state, interhemispheric asymmetry of "the emotional resonance" reaction is not significant and in the motor and investigatory activity in the open field, in contrast to intact animals, the right hemisphere is dominant and not the left one. Ovariectomy of mature female rats led to the increase of the dominance of the left hemisphere in the control of "the emotional resonance" and change of the right hemispheric dominance in the control of the motor and investigatory activity in the open field for the left hemispheric one. Gonadectomy of male and female mature rats had an opposite effect on the functioning of the right hemisphere: facilitating in male rats and inhibitory in female ones.     

Induced Responses in Phenolic Metabolism in Two Norway Spruce Clones after Wounding and Inoculations with Ophiostoma polonicum,a Bark Beetle-Associated Fungus

Two Norway spruce (Picea abies Karst.) clones, one resistant and the other susceptible to mass inoculation with Ophiostoma polonicum Siem., were compared with regard to their phenolic compositions and chalcone synthase (CHS) and stilbene synthase activities of their phloem before and at 6 and 12 d after artificial inoculation with sterile malt agar or O. polonicum. In unwounded phloem, the resistant clone differed from the susceptible clone by the presence of taxifolin glycoside, lower concentrations of stilbene glycosides, and higher CHS activity. After inoculation, (+)-catechin concentration and CHS activity dramatically increased around the wound, particularly in the resistant clone. Stilbene synthase activity also increased, but more slowly and to a lower level, whereas the concentrations of stilbenes remained stable. Tanning ability decreased in the susceptible clone, whereas it remained stable in the resistant one. It is proposed that the induced phenolic response of Norway spruce phloem consists of an activation of the phenolic pathway, finally leading to tannins and insoluble polymers. It is suggested that resistance to O. polonicum depends on the ability of the tree to easily activate the flavonoid pathway.     

疏肝补肾法对疲劳大鼠的学习和记忆力之影响

目的：探讨疏肝补肾法对疲劳大鼠学习和记忆力及对海马CA1区神经颗粒素（Neurogranin,Ng）的mRNA表达变化的影响。方法：成年雄性Spargue-Dawley大鼠36只,随机分为模型组（MG）、对照组（CG）、和疏肝补肾组（LK）。采用复合模型：运动疲劳模型与睡眠剥夺法造疲劳大鼠模型。运用Y迷宫进行学习和记忆力的测试。以Real-timePCR技术分析海马CA1区神经颗粒素的mRNA表达。结果：Y迷宫实验显示用药后大鼠的学习和记忆能力优于模型组,而疏肝补肾组大鼠在正确反应率、错误反应次数、达标所需训练次数和总反应时间皆与模型组有差异（分别为P〈0.01、P〈0.01、P〈0.05和P〈0.05）,其NgmRNA在海马CA1区的表达也显着高于模型组（P〈0.01）。结论：复合模型会造成大鼠学习和记忆能力受损。疏肝补肾法能显着影响疲劳大鼠的学习记忆能力及海马CA1区Ng的mRNA表达。     

Oxidative stress--mediated alterations in glucose dynamics in a genetic animal model of type II diabetes

Insulin resistance, characterized by an inexorable decline in skeletal muscle glucose utilization and/or an excessive hepatic glucose production, constitutes a major pathogenic importance in a cluster of clinical disorders including diabetes mellitus, hypertension, dyslipidemia, central obesity and coronary artery disease. A novel concept suggests that heightened state of oxidative stress during diabetes contributes, at least in part, to the development of insulin resistance. Several key predictions of this premise were subjected to experimental testing using Goto-Kakizaki (GK) rats as a genetic animal model for non-obese type II diabetes. Euglycemic-hyperinsulinemic clamp studies with an insulin infusion index of 5 mU/kg bw/min were used to measure endogenous glucose production (EGP), glucose infusion rate (GIR), glucose disposal rate (GDR) and skeletal muscle glucose utilization index (GUI). Moreover, the status of oxidative stress as reflected by the urinary levels of isoprostane and protein carbonyl formation were also assessed as a function of diabetes. Post-absorptive basal EGP and circulating levels of insulin, glucose and free fatty acid (FFA) were elevated in GK rats, compared to their corresponding control values. In contrast, steady state GIR and GDR of the hyperglycemic/hyperinsulinemic animals were reduced, concomitantly with impaired insulin's ability to suppress EGP. Insulin stimulated [3H]-2-deoxyglucose (2-DG) uptake (a measure of glucose transport activity) by various types of skeletal muscle fibers both in vivo and in vitro (isolated muscle, cultured myoblasts) was diminished in diabetic GK rats. This diabetes-related suppression of skeletal muscle glucose utilization was associated with a decrease in insulin's ability to promote the phosphorylation of tyrosine residues of insulin receptor substrate-1 (IRS-1). Similarly, the translocation of GLUT-4 from intracellular compartment to plasma membrane in response to insulin was also reduced in these animals. Oxidative stress-based markers (e.g. urinary isoprostane, carbonyl-bound proteins) were elevated as a function of diabetes. Nullification of the heightened state of oxidative stress in the GK rats with alpha-lipoic acid resulted in a partial amelioration of the diabetes-related impairment of the in vivo and in vitro insulin actions. Collectively, the above data suggest that 1) insulin resistance in GK rats occurs at the hepatic and skeletal muscle levels, 2) muscle cell glucose transport exhibited a blunted response to insulin and it is associated with a major defect in key molecules of both GLUT-4 trafficking and insulin signaling pathways, 3) skeletal muscle insulin resistance in GK rats appears to be of genetic origin and not merely related to a paracrine or autocrine effect, since this phenomenon is also observed in cultured myoblasts over several passages and finally heightened state of oxidative stress may mediate the development of insulin resistance during diabetes.     

Study on the optimum number of trials and intensity of unconditioned stimulants and strain difference in the two-way shuttle-box avoidance test using rats

In order to determine the optimun conditions suitable for a number of trials and the intensity of unconditioned stimulant (US) in the two-way shuttle-box avoidance test in Sprague-Dawley strain rats, which are used most frequently in reproduction studies, conditioned avoidance response was observed under various conditions for 30 and 60 trials and the low and high US levels. Investigation was also conducted in Wistar rats under a high US level with 30 and 60 trials. Latency time of the escape response in Sprague-Dawley rats was shortened with increasing trials. Body weight gains of both strains of rats in the high US level with the 60-trial group decreased during the observation period. These findings suggest that the high US level with the 60-trial group is not suitable for the two-way shuttle-box avoidance test. The rate and latency time of the avoidance response were lower in Wistar rats than in Sprague-Dawley rats, although those of the escape response were higher. Significant changes in the following were observed, mainly from first to third sessions: the avoidance rate of all groups in strains of rats, escape rate of 60-trial group in Sprague-Dawley rats, avoidance and escape latency time of the 60-trial groups in both strains of rats and escape latency time of the 30-trial group in Sprague-Dawley strain rats.     

Variation in gene expression of inflammatory cytokines in leukocyte-derived cells of high-fat-diet-induced insulin-resistant rats

A high-fat diet is thought to enhance inflammation in various tissues by increasing insulin resistance. In this study, we determined the mRNA levels of inflammatory cytokines in leukocyte-derived cells in the blood of rats with high-fat-diet-induced insulin resistance. Feeding rats a high-fat diet for 77 d induced moderate insulin resistance, which was determined by increased plasma glucose and insulin concentrations, following an oral glucose tolerance test. The interleukin (IL)-1beta mRNA level was higher in the insulin-resistant rats than in control rats at the fasting stage, whereas the tumor necrosis factor (TNF)-alpha mRNA level was greatly elevated at 180 min after glucose administration in the insulin-resistant rats. The results suggest that feeding rats a high-fat diet enhances the expression of fasting IL-1beta and postprandial TNF-alpha genes in leukocyte-derived cells.     

Variation in Gene Expression of Inflammatory Cytokines in Leukocyte-Derived Cells of High-Fat-Diet-Induced Insulin-Resistant Rats

A high-fat diet is thought to enhance inflammation in various tissues by increasing insulin resistance. In this study, we determined the mRNA levels of inflammatory cytokines in leukocyte-derived cells in the blood of rats with high-fat-diet-induced insulin resistance. Feeding rats a high-fat diet for 77 d induced moderate insulin resistance, which was determined by increased plasma glucose and insulin concentrations, following an oral glucose tolerance test. The interleukin (IL)-1β mRNA level was higher in the insulin-resistant rats than in control rats at the fasting stage, whereas the tumor necrosis factor (TNF)-α mRNA level was greatly elevated at 180 min after glucose administration in the insulin-resistant rats. The results suggest that feeding rats a high-fat diet enhances the expression of fasting IL-1β and postprandial TNF-α genes in leukocyte-derived cells.     

Mitochondrial adaptations to steatohepatitis induced by a methionine- and choline-deficient diet

Nonalcoholic fatty liver disease (NAFLD) has become common liver disease in Western countries. There is accumulating evidence that mitochondria play a key role in NAFLD. Nevertheless, the mitochondrial consequences of steatohepatitis are still unknown. The bioenergetic changes induced in a methionine- and choline-deficient diet (MCDD) model of steatohepatitis were studied in rats. Liver mitochondria from MCDD rats exhibited a higher rate of oxidative phosphorylation with various substrates, a rise in cytochrome oxidase (COX) activity, and an increased content in cytochrome aa3. This higher oxidative activity was associated with a low efficiency of the oxidative phosphorylation (ATP/O, i.e., number of ATP synthesized/natom O consumed). Addition of a low concentration of cyanide, a specific COX inhibitor, restored the efficiency of mitochondria from MCDD rats back to the control level. Furthermore, the relation between respiratory rate and protonmotive force (in the nonphosphorylating state) was shifted to the left in mitochondria from MCDD rats, with or without cyanide. These results indicated that, in MCDD rats, mitochondrial ATP synthesis efficiency was decreased in relation to both proton pump slipping at the COX level and increased proton leak although the relative contribution of each phenomenon could not be discriminated. MCDD mitochondria also showed a low reactive oxygen species production and a high lipid oxidation potential. We conclude that, in MCDD-fed rats, liver mitochondria exhibit an energy wastage that may contribute to limit steatosis and oxidative stress in this model of steatohepatitis.     

Heightened sour preferences during childhood

Basic research has revealed that the chemical sensory world of children is different from that of adults, as evidenced by their heightened preferences for sweet and salty tastes. However, little is known about the ontogeny of sour taste preferences, despite the growing market of extreme sour candies. The present study investigated whether the level of sourness most preferred in a food matrix and the ability to discriminate differences in sour intensity differed between 5- to 9-year-old children and their mothers, by using a rank-by-elimination procedure embedded in the context of a game. Mothers also completed a variety of questionnaires and children were asked several questions to assess whether children's temperament and food preferences and habits related to sour preferences. The results indicated that, although every mother and all but two of the children (92%) were able to rank the gelatins from most to least sour, more than one-third (35%) of the children, but virtually none of the adults, preferred the high levels of sour taste (0.25 M citric acid) in gelatin. Those children who preferred the extreme sour tastes were significantly less food neophobic (P < 0.05) and tended to experience a greater variety of fruits when compared with the remaining children (P = 0.11). Moreover, the children's preference for sour tastes generalized to other foods, such as candies and lemons, as reported by both children and mothers. These findings are the first experimental evidence to demonstrate that sour taste preferences are heightened during childhood and that such preferences are related to children's food habits and preferences. Further research is needed to unfold the relationship between the level of sour taste preferred and the actual consumption of sour-tasting foods and flavors in children.     

Paraquat-induced lipid peroxidation: effects of ovariectomy and estrogen receptor antagonist

Estrogen protects females against cardiovascular diseases in both receptor-dependent, genomic or non-genomic manner. Although part of the protective effects is attributed to its enhancement of nitric oxide (NO) production and antioxidant properties, in vivo evidence is difficult to establish. We thus employed paraquat (PQ)-treated rats as a model for oxidative stress and to compare oxidative damage determined by malondialdehyde (MDA) contents as index for lipid peroxidation of various tissues. Samples from aorta, lung, and liver exhibited low but detectable MDA level in intact control rats; sham operation did not but PQ-treatment significantly enhanced the MDA levels of all tissues. Different hormonal status were achieved by comparing sham-operated (sham), sham treated with estrogen receptor antagonist ICI182,780 (ICI), and ovariectomized (OVX) rats. OVX significantly reduced plasma estrogen level, ICI effectively blocked estrous cycle without reducing estrogen level. Derived from rats subjected to identical PQ treatment, MDA level was significantly higher in OVX rats than that of sham in isolated aortic rings. In lung tissues, MDA level were similar in all groups. In liver tissues, ICI rats exhibited higher level of MDA than both sham and OVX rats. These data indicated that hormonal status could affect the degree of lipid peroxidation under similar oxidative stress induced by PQ, and that not all tissues responded identically.