Peripheral inflammatory hyperalgesia is exacerbated in rats with metabolic disorders induced by a fructose diet.

This study explored the effects of fructose-induced obesity and metabolic disorders on peripheral inflammatory hyperalgesia, employing quantitative sensory testing with the von Frey test and measuring paw edema to assess inflammatory responses. Wistar rats were administered water or 10% fructose solution ad libitum over a period of 5 weeks. After intraplantar administration of inflammatory agents such as carrageenan (1 mg/paw), lipopolysaccharide (LPS; 100 µg/paw), or prostaglandin E2 (PGE2, 100 ng/paw), we conducted mechanical hyperalgesia tests and paw edema evaluations. The fructose diet resulted in dyslipidemia, elevated insulin and leptin plasma levels, insulin resistance, and increased epididymal and retroperitoneal adiposity compared to control animals. In response to inflammatory agents, the fructose group displayed significantly enhanced peripheral hyperalgesia and more pronounced paw edema. Our results demonstrate that fructose not only contributes to the development of obesity and metabolic disorder but also exacerbates peripheral inflammatory pain responses by enhancing prostaglandin sensitivity.

Neuromodulator hydrogen sulfide attenuates sickness behavior induced by lipopolysaccharide.

Sickness behavior reflects a state of altered physiology and central nervous system function that occurs during systemic infection or inflammation, serving as an adaptive response to illness. This study aims to elucidate the role of hydrogen sulfide (H2S) in regulating sickness behavior and neuroinflammatory responses in a rat model of systemic inflammation. Adult male Wistar rats were treated with lipopolysaccharide (LPS) to induce sickness behavior. Intracerebroventricular (i.c.v.) pretreatments included aminooxyacetic acid (AOAA), an inhibitor of H2S synthesis, and sodium sulfide (NaHS), an H2S donor. Behavioral assays were conducted, along with the assessment of astrocyte activation, as indicated by GFAP expression in the hypothalamus. Pretreatment with NaHS mitigated LPS-induced behavioral changes, including hypophagia, social and exploratory deficits, without affecting peripheral cytokine levels, indicating a central modulatory effect. AOAA, conversely, accentuated certain behavioral responses, suggesting a complex role of endogenous H2S in sickness behavior. These findings were reinforced by a lack of effect on plasma interleukin levels but significant reduction in GFAP expression. Our findings support the central role of H2S in modulating neuroinflammation and sickness behavior, highlighting the therapeutic potential of targeting H2S signaling in neuroinflammatory conditions.

Influence of maternal immune activation on autism-like symptoms and coping strategies in male offspring.

Maternal immune activation (MIA) caused by exposure to pathogens or inflammation during critical periods of gestation increased susceptibility to neurodevelopmental disorders, including autism, in the offspring. In the present work, we aimed to provide characterization of the long-term consequences on anxiety-like behavior and cardiovascular stress response of MIA in the offspring. This study aimed to evaluate the effect of MIA by lipopolysaccharide (LPS) in adult male offspring. In our study, the animals were subjected to a range of behavioral and physiological tests, including the elevated plus maze, social interaction, cat odor response, open field behavior, contextual fear conditioning, and cardiovascular responses during restraint stress. In the offspring of MIA, our study unveiled distinct anxious behaviors. This was evident by fewer entries into the open arms of the maze, diminished anti-thigmotaxis in the open field, and a decrease in social interaction time. Moreover, these rats showed heightened sensitivity to cat odor, exhibited prolonged freezing during fear conditioning, and presented elevated 22 Hz ultrasonic vocalizations. Notably, during restraint stress, these animals manifested an augmented blood pressure response, and this was associated with an increase in c-fos expression in the locus coeruleus compared to the control group. These findings collectively underline the extensive behavioral and physiological alterations stemming from MIA. This study deepens our understanding of the significance of maternal health in predisposing offspring to neurobehavioral deficits and psychiatric disorders.

Curcumin attenuates LPS-induced sickness behavior and fever in rats by modulating Nrf2 activity.

Lipopolysaccharide (LPS) is a potent inducer of inflammation, triggering behavioral changes and fever. The present study aimed to evaluate whether pretreatment with curcumin prevents the behavioral changes and fever induced by LPS through the modulation of nuclear factor-erythroid 2 related factor 2 (Nrf2). Male Wistar rats received either vehicle or LPS and after 2 h, the behavioral responses were assessed through open field test (OFT), social interaction test, forced swim test (FST), and food intake assessment. The febrile response was assessed by telemetry after vehicle or LPS injection to evaluate the effect of curcumin on the thermoregulatory response during the immunological challenge. The pretreatment with curcumin at doses of 50 and 100 mg/kg prevented the reduction of distance traveled on OFT, increased the immobility time of FST, impaired social withdrawal, decreased food intake, and induced fever. In addition, at these doses, it was possible to observe a significant decrease in the plasma levels of cytokines and an increase in Nrf2 translocation to the cell nucleus during the immunological challenge. Our data provide further evidence of curcumin's ability to prevent LPS-induced sickness behavior and fever possibly by a mechanism related to the modulation of Nrf2 translocation.

Hyperactivation of the amygdala correlates with impaired social play behavior of prepubertal male rats in a maternal immune activation model.

Maternal infection during pregnancy is an environmental risk factor for neurodevelopmental dysfunction, such as autism spectrum disorder (ASD). This study investigated the effect of maternal immune activation (MIA) on the behavior profile of prepubertal offspring and whether MIA alters the neuronal activation pattern of brain areas related to social play behavior. Pregnant Wistar rats received 500 µg/kg of lipopolysaccharide or saline solution on gestational day 16. Their offspring were tested using behavioral tasks to capture some of the core and associated ASD-like symptoms. Neuronal activation, indexed via c-fos expression after social play behavior, was evaluated in several brain areas. MIA had a number of adverse effects on dams and reduced the number of successful births and litter size. MIA induced sex-specific autistic-like features by a reduction in ultrasonic vocalizations in response to separation from the mother and nest, reduction in discrimination between neutral odors and their nest odor, moderate effect in stereotypies in the hole-board test, impaired risk assessment phenotype, and reduction in social play behavior without changes in locomotor activity only in prepubertal male offspring. A decrease in social play behavior may be associated with a decrease in the number of c-fos-positive cells in the prefrontal cortex and striatum, but hyperactivation of the basolateral and basomedial amygdala. Prenatal immune challenge results in ASD-like symptoms such as impaired risk assessment behavior, communication, and social interactions in male prepubertal offspring. Impaired social play behavior is correlated with neuronal hyperactivation in the amygdala.

Maternal overweight induced by reduced litter size impairs the behavioral neurodevelopment of offspring.

AIMS: We assessed the influence of maternal overweight on the behavioral neurodevelopment of male and female offspring in prepubertal age by reducing the litter size. MAIN METHODS: To reduce litter size in Wistar rats, the offspring of generation 0 (G0) were culled for 12 pups (6 males and 6 females: normal litter, NL-G1) or 4 pups (2 males and 2 females: small litter, SL-G1). In G1 dams, overweight was characterized, maternal behavior and locomotor activity were assessed. At G2, we quantified the ultrasonic vocalizations in post-natal day 5 (PND5); we evaluated olfactory discrimination in the homing behavior test on PND13; and in PND28-32 (prepubertal age), we performed the following tests: social play behavior, hole board, object recognition, and open field. At the end of the experiments, hippocampus and prefrontal cortex were dissected to quantify the synaptophysin by western blotting. KEY FINDINGS: Our data demonstrated that a reduction in litter size was able to induce maternal overweight without altering the parameters related to overweight in the offspring. The SL-G2 offspring showed deficits in early social communication, olfactory discrimination, social play behavior, and the exploration of objects, in addition to increasing repetitive and stereotyped movements. There were also changes in the synaptophysin levels in the hippocampus and prefrontal cortex of the offspring from reduced litter dams. In conclusion, maternal overweight caused by litter reduction impairs behavioral neurodevelopment, inducing autism-like symptoms in the offspring. SIGNIFICANCE: This study alerts the public about the negative consequences of maternal overweight in the descendants.

Maternal separation increases pain sensitivity by reducing the activity of serotonergic neurons in the dorsal raphe nucleus and noradrenergic neurons in locus coeruleus.

Animals subjected to early life maternal separation exhibit increased sensitivity to chemical, thermal, and mechanical stimuli during adulthood. However, the mechanism by which maternal separation can alter pain sensitivity in adulthood has not yet been investigated. Thus, we aimed to evaluate the activity of serotonergic and noradrenergic neurons and the effect of serotonin (5-HT) and noradrenaline (NA) reuptake inhibitors in male and female Wistar rats subjected to maternal separation. This study consisted of two experiments: 1) to confirm whether maternal separation increased pain sensitivity (n = 8 per group) and to evaluate the activity of serotonergic neurons in the dorsal raphe nucleus and noradrenergic neurons in locus coeruleus in animals subjected to maternal separation in comparison to controls (n = 6 per group); and 2) to evaluate the effect of fluoxetine (a selective 5-HT reuptake inhibitor) and desipramine (a NA reuptake inhibitor) on sensitivity to chemical stimulation using formalin in animals subjected to maternal separation (n = 8 per group). Our findings indicated that maternal separation increases an animal's sensitivity to painful chemical stimulation and reduces the activity of 5-HT and NA neurons. In addition, acute pretreatment with a 5-HT or NA reuptake inhibitor prevented the increased response to painful stimulation induced by maternal separation. In conclusion, maternal separation increases pain sensitivity by reducing the activity of serotonergic neurons in the dorsal raphe nucleus and noradrenergic neurons in locus coeruleus. This study contributes to possible treatments for pain in individuals exposed to early life stress.

Neonatal overnutrition programming impairs cholecystokinin effects in adultmale rats.

Overfeeding and rapid weight gain during early life are risk factors for the development of obesity in adulthood. This metabolic malprogramming may be mediated by endocrine disturbances during critical periods of development. Cholecystokinin (CCK) acts on the central nervous system by elevating thermogenesis and the activity of anorectic neurons, modulating overall energy balance. Therefore, we tested the hypothesis that postnatal overfeeding impaired CCK effects. Pups were raised in either a litter of three (neonatal overnutrition/small litter group) or 12 (controls/normal litter group) pups per dam to study the effects of postnatal overfeeding on the central and peripheral CCK systems in adulthood. Rats raised in small litters became overweight during lactation and remained overweight as adults, with increased adiposity and plasma levels of lipids, glucose, insulin, and leptin. Neonatally over-nourished rats showed attenuation of gastric emptying and anorexigenic response to CCK, suggesting that offspring from the SL group may present CCK resistance as adult male rats. Consistent with this idea, overweight rats displayed impaired central response in c-Fos immunoreactivity on the nucleus tractus solitarius, area postrema, paraventricular nucleus, central amygdala, arcuate nucleus, and dorsomedial hypothalamus in response to peripheral CCK at adulthood. The small litter group of adult male rats also exhibited reduced norepinephrine- and CCK-stimulated thermogenesis. Unresponsiveness to the effects of CCK may contribute to overweight and metabolic dysfunctions observed in postnatally over-nourished adult rats. Thus, the involvement of an impaired CCK system, among other neurohormonal failures, may contribute to the development of obesity.