Thiago M. Reis-Silva

Single early prenatal lipopolysaccharide exposure impairs striatal monoamines and maternal care in female rats

AIMS Environmental information received by a mother can induce a phenotype change in her offspring, commonly known as a maternal effect (trans-generational effect). The present work verified the effects of lipopolysaccharide (LPS), which mimics bacterial infection, on maternal care and on the activity of related brain areas in F1 offspring, i.e., female rats that were prenatally exposed to LPS. MAIN METHODS Pregnant rats received 100μg/kg of LPS intraperitoneally on gestational day (GD) 9.5. Female offspring of the F1 generation were mated to naïve males and were evaluated during their lactation period for open field, maternal and aggressive behaviors. Striatal and hypothalamic dopamine and serotonin levels and turnover were also evaluated. Furthermore, astrocyte protein expression in the nucleus accumbens (NA) was analyzed in F1 females to assess LPS-induced neuroinflammation. KEY FINDINGS Prenatal LPS did not change open field behavior but impaired both maternal and maternal aggressive behaviors in the F1 generation. LPS exposure also reduced both striatal levels of dopamine and serotonin and its metabolites, but induced no changes in NA astrocyte expression. SIGNIFICANCE We suggested that the observed impairments in the F1 females were a consequence of a motivational change induced by prenatal LPS, as (1) no changes in motor activity were observed, (2) prenatal LPS-exposure was reported by our group to induce motivational impairments in males, and (3) the existence of a strong connection between striatal dopaminergic activity and motivation-oriented activities. The present findings strongly indicate a maternal effect for prenatal LPS, at least for the F1 generation.

Zinc Prevents Sickness Behavior Induced by Lipopolysaccharides after a Stress Challenge in Rats

Sickness behavior is considered part of the specific beneficial adaptive behavioral and neuroimmune changes that occur in individuals in response to infectious/inflammatory processes. However, in dangerous and stressful situations, sickness behavior should be momentarily abrogated to prioritize survival behaviors, such as fight or flight. Taking this assumption into account, we experimentally induced sickness behavior in rats using lipopolysaccharides (LPS), an endotoxin that mimics infection by gram-negative bacteria, and then exposed these rats to a restraint stress challenge. Zinc has been shown to play a regulatory role in the immune and nervous systems. Therefore, the objective of this study was to examine the effects of zinc treatment on the sickness response of stress-challenged rats. We evaluated 22-kHz ultrasonic vocalizations, open-field behavior, tumor necrosis factor α (TNF-α), corticosterone, and brain-derived neurotrophic factor (BDNF) plasma levels. LPS administration induced sickness behavior in rats compared to controls, i.e., decreases in the distance traveled, average velocity, rearing frequency, self-grooming, and number of vocalizations, as well as an increase in the plasma levels of TNF-α, compared with controls after a stressor challenge. LPS also decreased BDNF expression but did not influence anxiety parameters. Zinc treatment was able to prevent sickness behavior in LPS-exposed rats after the stress challenge, restoring exploratory/motor behaviors, communication, and TNF-α levels similar to those of the control group. Thus, zinc treatment appears to be beneficial for sick animals when they are facing risky/stressful situations.

Long-lasting monoaminergic and behavioral dysfunctions in a mice model of socio-environmental stress during adolescence.

HighlightsStress during adolescence compromises the capacity of the HPA axis ability to properly respond to a stressor in adulthood.Socio‐environmental stress during adolescence causes non‐adaptive rearrangement in the CNS.Long‐lasting changes in neural pathways and behavior in stressed adolescent male mice. ABSTRACT Adolescence is one of the critical periods of development and has great importance to health for an individual as an adult. Stressors or traumatic events during this period are associated with several psychiatric disorders as related to anxiety or depression and cognitive impairments, but whether negative experiences continue to hinder individuals as they age is not as well understood. We determined how stress during adolescence affects behavior and neurochemistry in adulthood. Using an unpredictable paradigm (2 stressors per day for 10 days) in Balb/c mice, behavioral, hormonal, and neurochemical changes were identified 20 days after the cessation of treatment. Adolescent stress increased motor activity, emotional arousal and vigilance, together with a reduction in anxiety, and also affected recognition memory. Furthermore, decreased serotonergic activity on hippocampus, hypothalamus and cortex, decreased noradrenergic activity on hippocampus and hypothalamus, and increased the turnover of dopamine in cortex. These data suggest behavioral phenotypes associated with emotional arousal, but not depression, emerge after cessation of stress and remain in adulthood. Social‐environmental stress can induce marked and long‐lasting changes in HPA resulting from monoaminergic neurotransmission, mainly 5‐HT activity.

Prenatal lipopolysaccharide disrupts maternal behavior, reduces nest odor preference in pups, and induces anxiety: studies of F1 and F2 generations.

The present study analyzed the transgenerational effects of lipopolysaccharide (LPS; 100 μg/kg) administration on gestational day 18 (GD18) of parental generation on maternal-pups interaction of F1 and F2 generations. Also the long term behavioral effects were observed in male of F2 generation. In F1 generation, the reproductive performance, maternal behavior, maternal aggressive behavior, and general activity in the open field in adulthood were analyzed. In F2 generation, body weight at birth and at weaning, nest odor preference, and general activity in the open field and elevated plus maze in adulthood were assessed. Compared to controls, results showed that in the F1 generation, prenatal LPS exposure (1) increased the latency to full maternal behavior, but all of the females grouped the pups and presented full maternal behavior, (2) reduced the total time boxing and fighting, increased the frequency of retrieving the pups, and increased the number of bites, and (3) did not affect reproductive performance or general activity. In F2 generation, compared with controls, the LPS group exhibited (1) a decrease in body weight at weaning, (2) a decrease in nest odor preference, (3) a decrease in the percentage of time spent in the open arms, a decrease in the percentage of time spent in the center, and an increase in the time spent in the closed arms in the elevated plus maze, and (Huang et al.) no affect behavior in the open field. Prenatal LPS exposure improved maternal care in the F1 generation with regard to nursing and pup survival but did not improve the motivational parameters of maternal behavior likely because of a reduction of maternal stimulation by the pups. In the F2 generation, the reduction of nest odor preference in the pups suggests a less maternal recognition. In adulthood, these rats exhibited increased anxiety-like behavior. These data did not result from motor alterations because rats in both the F1 and F2 generations did not show alterations in open field behavior. This transfer of information across generations likely occurred through nongenetic means because the endotoxin was administered at the end of pregnancy. These results may have implications for clinical therapeutics in human disorders and evolution.

Prenatal exposure to integerrimine N-oxide enriched butanolic residue from Senecio brasiliensis affects behavior and striatal neurotransmitter levels of rats in adulthood.

Pyrrolizidine alkaloids (PAs) are toxins that are exclusively biosynthesized by plants and are commonly present in foods and herbs. PAs are usually associated with poisoning events in livestock and human beings. The aim of the present study was to evaluate the behavioral and neurochemical effects of prenatal exposure to PA integerrimine N‐oxide of rats in adulthood. Pregnant Wistar rats received integerrimine N‐oxide from the butanolic residue of Senecio brasiliensis by gavage on gestational days 6–20 at doses of 3, 6 and 9 mg/kg. During adulthood of the offspring, the following behavioral tests were performed: open‐field, plus‐maze, forced swimming, catalepsy and stereotypy. Histological analyses and monoamine levels were measured. Male offspring from dams that were exposed to 9 mg/kg showed an increase in locomotion in the open‐field test, an increased frequency of entries and time spent in open arms in elevated plus‐maze test, as well as decreased swimming time. In the female offspring from dams that were exposed to 9 mg/kg, there was an increased time of climbing in forced swimming and intensity of stereotyped behavior. The histological study indicates an increase in the number of multinucleated cells in the liver (6 and 9 mg/kg). In neurotransmitter analysis, specifically in the striatum, we observed change in dopamine and serotonin levels in the middle dose. Thus, our results indicate that prenatal exposure to integerrimine N‐oxide changed behavior in adulthood and neurotransmitter levels in the striatum. Our results agree with previous studies, which showed that integerrimine N‐oxide impaired physical and neurobehavioral development in childhood that can persist until adulthood.

Prenatal exposure to integerrimine N-oxide impaired the maternal care and the physical and behavioral development of offspring rats

Plants that contain pyrrolizidine alkaloids (PAs) have been reported as contaminants of pastures and food, as well as being used in herbal medicine. PAs are responsible for poisoning events in livestock and human beings. The aim of this present study was to evaluate effects of prenatal exposure to integerrimine N‐oxide, the main PA found in the butanolic residue (BR) of Senecio brasiliensis, on both physical and behavioral parameters of Wistar rat offspring. The toxicity and maternal behavior were also evaluated. For this, pregnant Wistar rats received integerrimine N‐oxide from the BR of Senecio brasiliensis, by gavage, on gestational days 6–20 (during organogenesis and fetal development period) at doses of 3, 6 and 9 mg/kg. During treatment, maternal body weight gain, and food and water intake were evaluated. After parturition, maternal behavior and aggressive maternal behavior were analyzed. In addition, physical development and behavioral assessments were observed in both male and female pups. Results showed that prenatal exposure to integerrimine N‐oxide of S. brasiliensis induced maternal toxicity, impairment in maternal behavior and aggressive maternal behavior, mainly in the highest dose group. Between sexes comparison of pups showed loss of body weight, delayed physical development such as pinna detachment, hair growth, eruption of incisor teeth, eye and vaginal openings. These pups also showed a delay of palmar grasp, surface righting reflex, negative geotaxis and auditory startle reflexes. Thus, prenatal exposure to integerrimine N‐oxide induces maternal toxicity, impairment of maternal care and delayed in physical and behavioral development of the offspring.

Ivermectin reduces motor coordination, serum testosterone, and central neurotransmitter levels but does not affect sexual motivation in male rats

Ivermectin (IVM) is a macrocyclic lactone used for the treatment of parasitic infections and widely used in veterinary medicine as endectocide. In mammals, evidence indicates that IVM interacts with γ-aminobutyric acid (GABA)-mediated chloride channels. GABAergic system is involved in the manifestation of sexual behavior. We previously found that IVM at therapeutic doses did not alter sexual behavior in male rats, but at a higher dose, the appetitive phase of sexual behavior was impaired. Thus, we investigated whether the reduction of sexual behavior that was previously observed was a consequence of motor or motivational deficits that are induced by IVM. Data showed significant decrease in striatal dopaminergic system activity and lower testosterone levels but no effects on sexual motivation or penile erection. These findings suggest IVM may activate the GABAergic system and reduce testosterone levels, resulting in a reduction of motor coordination as consequence of the inhibition of striatal dopamine release.

Prenatal lipopolysaccharide exposure affects sexual dimorphism in different germlines of mice with a depressive phenotype

The objective of the present study was to investigate whether prenatal lipopolysaccharide (LPS) administration modifies the expression of depressive and non-depressive-like behavior in male and female mice across two generations. The sexual dimorphism of these mice was also examined in the open-field test. Male and female mice of the parental (F0) generation were selected for depressive- or non-depressive-like behavioral profiles using the tail suspension test (TST). Animals with similar profiles were matched for further mating. On gestation day (GD) 15, pregnant F0 mice received LPS (100μg/kg, i.p.) and were allowed to nurture their offspring freely. Adult male and female of the F1 generation were then selected according to behavioral profiles and observed in the open field. Male and female mice of the two behavioral profiles were then mated to obtain the F2 generation. Adults from the F2 generation were also behaviorally phenotyped, and open field behavior was assessed. Male mice that were selected for depressive- and non-depressive-like behaviors and treated or not with LPS in the parental generation exhibited similar proportions of behavioral profiles in both filial lines, but LPS exposure increased the number of depressive-like behavior. An effect of gender was observed in the F1 and F2 generations, in which male mice were more sensitive to the intergenerational effects of LPS in the TST. These data indicate that prenatal LPS exposure on GD15 in the F0 generation influenced the transmission of depressive- and non-depressive-like behavior across filial lines, with sexual dimorphism between phenotypes.

Conditional Deletion ofRic-8bin Olfactory Sensory Neurons Leads to Olfactory Impairment

The olfactory system can discriminate a vast number of odorants. This ability derives from the existence of a large family of odorant receptors expressed in the cilia of the olfactory sensory neurons. Odorant receptors signal through the olfactory-specific G-protein subunit, Gαolf. Ric-8b, a guanine nucleotide exchange factor, interacts with Gαolf and can amplify odorant receptor signal transduction in vitro. To explore the function of Ric-8b in vivo, we generated a tissue specific knock-out mouse by crossing OMP-Cre transgenic mice to Ric-8b floxed mice. We found that olfactory-specific Ric-8b knock-out mice of mixed sex do not express the Gαolf protein in the olfactory epithelium. We also found that in these mice, the mature olfactory sensory neuron layer is reduced, and that olfactory sensory neurons show increased rate of cell death compared with wild-type mice. Finally, behavioral tests showed that the olfactory-specific Ric-8b knock-out mice show an impaired sense of smell, even though their motivation and mobility behaviors remain normal. SIGNIFICANCE STATEMENT Ric-8b is a guanine nucleotide exchange factor (GEF) expressed in the olfactory epithelium and in the striatum. Ric-8b interacts with the olfactory Gαolf subunit, and can amplify odorant signaling through odorant receptors in vitro. However, the functional significance of this GEF in the olfactory neurons in vivo remains unknown. We report that deletion of Ric-8b in olfactory sensory neurons prevents stable expression of Gαolf. In addition, we demonstrate that olfactory neurons lacking Ric-8b (and consequently Gαolf) are more susceptible to cell death. Ric-8b conditional knock-out mice display impaired olfactory guided behavior. Our results reveal that Ric-8b is essential for olfactory function, and suggest that it may also be essential for Gαolf-dependent functions in the brain.