Veronika Borbélyová

Animal models of autism with a particular focus on the neural basis of changes in social behaviour: an update article.

Research on autism has been gaining more and more attention. However, its aetiology is not entirely known and several factors are thought to contribute to the development of this neurodevelopmental disorder. These potential contributing factors range from genetic heritability to environmental effects. A significant number of reviews have already been published on different aspects of autism research as well as focusing on using animal models to help expand current knowledge around its aetiology. However, the diverse range of symptoms and possible causes of autism have resulted in as equally wide variety of animal models of autism. In this update article we focus only on the animal models with neurobehavioural characteristics of social deficit related to autism and present an overview of the animal models with alterations in brain regions, neurotransmitters, or hormones that are involved in a decrease in sociability.

Sex differences and sex hormones in anxiety-like behavior of aging rats

Abstract Sex differences in the prevalence of affective disorders might be attributable to different sex hormone milieu. The effects of short‐term sex hormone deficiency on behavior, especially on anxiety have been studied in numerous animal experiments, mainly on young adult rats and mice. However, sex differences in aged animals and the effects of long‐term hypogonadism are understudied. The aim of our study was to analyze sex differences in anxiety‐like behavior in aged rats and to prove whether they can be attributed to endogenous sex hormone production in males. A battery of tests was performed to assess anxiety‐like behavior in aged female, male and gonadectomized male rats castrated before puberty. In addition, the aged gonadectomized male rats were treated with a single injection of estradiol or testosterone or supplemented with estradiol for two‐weeks. Female rats displayed a less anxious behavior than male rats in most of the conducted behavioral tests except the light‐dark box. Long‐term androgen deficiency decreased the sex difference in anxiety either partially (open field, PhenoTyper cage) or completely (elevated plus maze). Neither single injection of sex hormones, nor two‐week supplementation of estradiol in gonadectomized aged male rats significantly affected their anxiety‐like behavior in the elevated plus maze. In conclusion, our results confirm sex differences in anxiety in aged rats likely mediated by endogenous testosterone production in males. Whether long‐term supplementation with exogenous sex hormones could affect anxiety‐like behavior in elderly individuals remains to be elucidated. Graphical abstract Figure. No Caption available. HighlightsAged male rats display higher anxiety‐like behavior than aged female rats.Endogenous androgens seem to be responsible for the sex differences in anxiety.Short‐term exogenous sex hormones do not reverse long‐term effects of hypogonadism.

The sex-dependent effects of letrozole on anxiety in middle-aged rats

Aromatase catalyzes the conversion of testosterone to estradiol and is involved in the physiological effects of sex hormones on brain function. Animal experiments have shown that the aromatase inhibitor, letrozole, can induce anxiety in young ovariectomized females that are used as a model of aging. Whether or not these effects would be similar in intact middle‐aged animals is unknown. The aim of our study was to analyze the effects of letrozole on anxiety in middle‐aged rats of both sexes. Fifteen month old male and female rats were treated daily with either letrozole or vehicle for 2 weeks. The elevated plus maze was used to test anxiety‐like behaviour. Sex differences were found not only in plasma concentrations of testosterone but also in the effects of letrozole treatment on plasma testosterone (P<.05). The interaction between sex and treatment was also proven in locomotor activity (P<.05) and time spent in the open arms of the elevated plus maze (P<.05). Letrozole‐treated male rats spent 95% less time in the open arms of the elevated plus maze than the control rats did (P<.05) suggesting an anxiogenic effect of aromatase inhibition. This difference was not found between letrozole‐treated and vehicle‐treated females. In contrast to previous experiments on young animals, letrozole seems to induce anxiety in male but not in female middle‐aged rats. This sex‐specific effect might be related to sex differences of oestrogen and androgen signalling in aging brains. These results should be taken into account in clinical applications of letrozole, especially in men.

Chronic renal insufficiency does not induce behavioral and cognitive alteration in rats.

In humans, chronic kidney disease (CKD) is associated with cognitive decline, increase in anxiety, or depression. The underlying mechanisms of these changes remain unclear. The aim of this study was to elucidate whether and how experimentally induced long-term CKD affects cognitive functions in rats. Thirty male Wistar rats underwent 5/6 nephrectomy (5/6 Nx), an established model of CKD, or sham surgery. Development of CKD was monitored using biochemical analyses and confirmed by renal histology. Behavioral tests of anxiety, depression and spatial behavior were performed before, and at 3 and 9 months after the surgery. CKD in 5/6 Nx rats was characterized by significant decrease of renal function, e.g., glomerular filtration rate, and progressive glomerulosclerosis, tubular atrophy, and interstitial fibrosis; and increased plasma uremic toxins. Mortality was higher in 5/6 Nx rats in comparison with controls. Compared to control group, the surviving 5/6 Nx rats presented similar general locomotor activity, depression traits, and spatial abilities (p=0.43, p=0.84, p=0.71, respectively). At 9 months, lower anxiety in the light-dark box test was observed in 5/6 Nx rats if compared with the control group (p=0.02). Despite the development of progressive CKD in 5/6 Nx rats, no expected behavioral changes were observed. Further experimental studies associating behavioral responses to severity of CKD are definitely needed to confirm the solely psychosocial aspect background of CKD-associated cognitive impairment in humans.

No effect of testosterone on behavior in aged Wistar rats

In men, aging is accompanied by a gradual decline in androgen secretion. Studies suggest beneficial effects of endogenous and exogenous testosterone on affective behavior and cognitive functions. The aim of this study was to describe behavioral and cognitive sex differences and to analyze the effects of long-term androgen deficiency in aged male rats. Thirty-months old rats divided into three groups (males, females and males gonadectomized as young adults) underwent a battery of behavioral tests assessing locomotor activity, anxiety, memory, anhedonia, sociability and depression-like behavior. No major effect of gonadectomy was found in any of the analyzed behavioral measures in male rats. The only consistent sex difference was confirmed in depression-like behavior with longer immobility time observed in males. In an interventional experiment, a single dose of testosterone had no effect on gonadectomized male and female rats in the forced swim test. In contrast to previous studies this comprehensive behavioral phenotyping of aged rats revealed no major role of endogenous testosterone. Based on our results long-term hypogonadism does not alter the behavior of aged male rats, neither does acute testosterone treatment. Whether these findings have any consequences on androgen replacement therapy in aged men remains to be elucidated.

Does rat fetal DNA induce preeclampsia in pregnant rats

Cell-free fetal DNA in maternal circulation is higher during preeclampsia. It is unclear whether it is the cause or the consequence of the disease. The aim of this study was to prove whether injected rat fetal DNA induces preeclampsia-like symptoms in pregnant Wistar rats. They received daily i.p. injections of water or rat fetal DNA (400 μg) from gestation day 14 to 18. Blood pressure, proteinuria, placental and fetal weight were measured at gestation day 19. Plasma DNase activity, proteinuria and creatinine clearance were assessed. There was no significant difference in any of the measured parameters. The results of this study do not confirm the hypothesis that fetal DNA might induce preeclampsia. This is in contrast to others using human fetal DNA in mice. Further studies should be focused on the effects of fetal DNA from the same species protected from DNase activity.

17β-Estradiol treatment reversed left ventricular dysfunction in castrated male rats: an echocardiographic study

No data are available on heart function in chronic testosterone deficiency and on the effect of estrogen treatment. Eighteen 4-week-old male Lewis rats were randomly divided into 3 groups (n = 6): 1 group of sham-operated rats and 2 groups of castrated rats. Sixty-six weeks after surgery, 1 castrated group received a dose of 17β-estradiol (10 μg/kg per day) and the remaining 2 groups received a placebo subcutaneously for 14 days. Left ventricular (LV) systolic and diastolic functions were measured by transthoracic echocardiography. Castration decreased LV ejection fraction (9%) and fractional shortening (15%) and deteriorated LV diastolic function (94%). 17β-Estradiol treatment increased LV ejection fraction (15%) and fractional shortening (31%) and improved LV diastolic function (48%). Plasma testosterone concentrations were decreased in both castrated groups. In conclusion, chronic testosterone deficiency induced LV systolic and diastolic dysfunction; these disorders were reversed by short-term treatment with 17β-estradiol.

Does long-term androgen deficiency lead to metabolic syndrome in middle-aged rats?

ABSTRACT Evidence from clinical observational studies and animal experiments suggests that hypogonadism is associated with the metabolic syndrome. In most of the experiments, androgen deficiency is induced by gonadectomy in the adulthood and relatively short‐term effects of hypogonadism on metabolic parameters are usually observed. The purpose of this study was to evaluate the metabolic effects of long‐term androgen deficiency starting before puberty in middle‐aged male rats. The components of the metabolic syndrome were examined in male, female and gonadectomized male rats at the age of 18 months. Sex differences were observed in plasma testosterone, cholesterol, high‐density lipoproteins and also in body weight and in glycemia dynamics during oral glucose tolerance test. Gonadectomy and long‐term hypogonadism did not affect most of the analyzed metabolic parameters such as blood pressure, glycemia, plasma insulin and uric acid. The only exception was the significantly higher liver enzymes in plasma and triacylglycerol in liver found in gonadectomized males. Except low‐density lipoprotein, neither treatment of middle‐aged males and females with letrozole, nor supplementation of estradiol as the metabolite of testosterone in gonadectomized male rats changed any of the observed metabolic parameters. Our results suggest that long‐term hypogonadism started before puberty does not induce metabolic syndrome in middle‐aged male rats, but may affect the liver. Sex differences in metabolic parameters in middle‐aged rats are not mediated by testosterone. Whether hypogonadism predispose to metabolic syndrome in combination with other risk factors needs further clarification. HighlightsLong‐term hypogonadism leads to partial liver damage in aged rats.Long‐term hypogonadism does not induce metabolic syndrome in aged rats.Sex differences in metabolic parameters are not mediated by testosterone.Short‐term administration of letrozole does not affect the metabolic parameters.Short‐term supplementation of estradiol does not affect the metabolic parameters.

Deoxyribonuclease partially ameliorates thioacetamide-induced hepatorenal injury

Several recent studies have shown that liver injury is associated with the release of DNA from hepatocytes. This DNA stimulates innate immunity and induces sterile inflammation, exacerbating liver damage. Similar mechanisms have been described for acute renal injury. Deoxyribonuclease degrades cell-free DNA and can potentially prevent some of the induced tissue damage. This study analyzed the effects of thioacetamide-induced hepatorenal injury on plasma DNA in rats. Plasma DNA of both nuclear and mitochondrial origin was higher in thioacetamide-treated animals. Administration of deoxyribonuclease resulted in a mild, nonsignificant decrease in total plasma DNA and plasma DNA of mitochondrial origin but not of nuclear origin. This was accompanied by a decrease in bilirubin, creatinine, and blood urea nitrogen as markers of renal function. In conclusion, the study confirmed the hepatotoxic and nephrotoxic effect of thioacetamide. The associated increase in cell-free DNA seems to be involved in hepatorenal pathogenesis because treatment with deoxyribonuclease resulted in a partial prevention of hepatorenal injury. Further experiments will focus on the effects of long-term treatment with deoxyribonuclease in other clinically more relevant models. Clinical studies should test endogenous deoxyribonuclease activity as a potential risk determinant for kidney or liver failure.NEW & NOTEWORTHY Thioacetamide-induced hepatorenal injury resulted in higher plasma cell-free DNA. Deoxyribonuclease decreased average cell-free DNA of mitochondrial origin but not nuclear origin. Deoxyribonuclease partially prevented hepatorenal injury in rats.

Effects of fractionated whole-brain irradiation on cellular composition and cognitive function in the rat brain

Abstract Purpose: The aim of this study was investigate whether histopathological changes in the neurogenic region correlate with appropriate cognitive impairment in the experimental model of radiation-induced brain injury. Materials and methods: Adult male Wistar rats randomized into sham (0 Gy) and two experimental groups (survived 30 and 100 days after treatment) received fractionated whole-brain irradiation (one 5 Gy fraction/week for four weeks) with a total dose of 20 Gy of gamma rays. Morris water maze cognitive testing, histochemistry, immunohistochemistry and confocal microscopy were used to determine whether the cognitive changes are associated with the alteration of neurogenesis, astrocytic response and activation of microglia along and/or adjacent to well-defined pathway, subventricular zone-olfactory bulb axis (SVZ-OB axis). Results: Irradiation revealed altered cognitive functions usually at 100 days after treatment. Neurodegenerative changes were characterized by a significant increase of Fluoro-Jade-positive cells 30 days after irradiation accompanied by a steep decline of neurogenesis 100 days after treatment. A strong astrocytic response and upregulation of the activated microglia were seen in both of experimental groups. Conclusions: Results shows that fractionated irradiation led to cognitive impairment closely associated with accerelation of neuronal cell death, inhibition of neurogenesis, activation of astrocytes and microglia indicate early delayed radiation-induced changes.