Aldina Venerosi

Behavioral and electrophysiological effects of the adenosine A2A receptor antagonist SCH 58261 in R6/2 huntington's disease mice

The effect of chronic treatment with the selective adenosine A2A receptor antagonist SCH 58261 on the behavioral and electrophysiological alterations typical of R6/2 mice (a transgenic mouse model of Huntingtons disease, HD), has been studied. Starting from 5 weeks of age, R6/2 and wild type (WT) mice were treated daily with SCH 58261 (0.01 mg/kg i.p.) for 7 days. In the following weeks, the ability of mice to perform in the rotarod, plus maze and open field tests were evaluated. In addition, with electrophysiological experiments in corticostriatal slices we tested whether the well-known increased NMDA vulnerability of R6/2 mice was prevented by SCH 58261 treatment. We found that chronic treatment with SCH 58262: i) fully prevented the alterations in emotional/anxious responses displayed by R6/2 mice; ii) did not prevent the impairment in motor coordination; iii) abolished the increase in NMDA-induced toxicity observed in the striatum of HD mice. On balance, targeting A2A receptors seems to have some beneficial effects in HD even though, given the complexity of A2A receptor pharmacology and HD pathogenesis, further studies are necessary to clarify whether A2A receptor antagonists have therapeutic potential in HD.

Long-term effects on hypothalamic neuropeptides after developmental exposure to chlorpyrifos in mice.

Background Increasing evidence from animal and human studies indicates that chlorpyrifos (CPF), similar to other organophosphorus insecticides still widely used, is a developmental neurotoxicant. Developmental exposure to CPF in rodents induces sex-dimorphic behavioral changes at adulthood, including social and agonistic responses, which suggests that CPF may interfere with maturation of neuroendocrine mechanisms. Objectives We assessed the hypothesis that CPF affects the levels of neurohypophyseal hormones acting as modulators of social behavior in mammals, such as oxytocin (OT), arginine vasopressin (AVP), and prolactin (PRL). Methods Pregnant female mice were orally administered with either vehicle (peanut oil) or 3 or 6 mg/kg CPF on gestational day (GD) 15 to GD18, and offspring were treated subcutaneously with either vehicle or 1 or 3 mg/kg CPF on postnatal days (PNDs) 11 to PND14. Dose levels were chosen to avoid systemic toxicity and inhibition of brain acetylcholinesterase. Offspring were sacrificed at 5 months of age, and expression of OT, AVP, and PRL was analyzed in the hypothalamus by Western blot or enzyme-linked immunosorbent assay (ELISA) analysis. Results Both male and female mice showed dose-related enhancement of OT expression, with males presenting the more intense effect. AVP expression was significantly reduced in male mice at the higher prenatal and postnatal dose. We observed no significant effect on PRL expression in either sex. Overall, outcomes were mainly attributable to fetal exposure, whereas postnatal doses appeared to potentiate the prenatal effects. Conclusions Our data indicate that developmental exposure to CPF may permanently interfere with specific key signaling proteins of the hypothalamic peptidergic system, with time-, dose-, and sex-related effects still evident at adulthood.

Sex dimorphic behaviors as markers of neuroendocrine disruption by environmental chemicals: The case of chlorpyrifos

The complexity of the neuroendocrine level of investigation requires the assessment of behavioral patterns that extend beyond the reproductive functions, which are age- and sex-specific in rodents, described by defined clusters of behavioral items regulated by genetic, hormonal, and epigenetic factors. The study of social behavior in laboratory rodents reveals sex-dimorphic effects of environmental chemicals that may be undetected either by a traditional neurotoxicological approach or referring to the classical definition of endocrine disrupting chemicals. Here we review data on the neurobehavioral effects of developmental exposure to the non-persistent organophosphorus insecticide chlorpyrifos, whose neurotoxic activity at low doses is currently a matter of concern for childrens health. In mice exposed to chlorpyrifos in utero and/or in early development social/emotional responses are differently affected in the two sexes in parallel with sex-dependent interference on hypothalamic neuroendocrine pathways regulating social behaviors (vasopressin, oxytocin, and steroid regulated systems). Through the analysis of complex sex-dimorphic behavioral patterns we show that neurotoxic and endocrine disrupting activities of CPF overlap. This widely diffused organophosphorus pesticide might thus be considered as a neuroendocrine disruptor possibly representing a risk factor for sex-biased neurodevelopmental disorders in children.

Prolonged perinatal AZT administration and early maternal separation: effects on social and emotional behaviour of periadolescent mice.

Zidovudine (AZT) is an effective treatment in preventing perinatal transmission of HIV-1; however, a continuous re-evaluation of the risk-benefit ratio of human exposure to this drug is suggested by both clinical and animal studies. The objective of this study was to assess the medium and long-term effects of pre-postnatal AZT treatment on mouse social and emotional behaviour and the possible interactions between AZT exposure and disruptions in the mother-infant relationship. Pregnant CD-1 mice were administered per os with AZT (160 mg/kg) from pregnancy day 10, throughout delivery, to lactation day 10. In half of the litters, the offspring was separated from the mother for 3 h from postnatal days 2 (PND2) to PND14. On PND35, a 30-min social interaction test was performed and corticosterone levels were measured at the end of the session. On PND80, long-term effects of AZT on emotionality were assess by means of an elevated plus-maze. Results indicate that, on PND35, previous AZT exposure affected social behaviour of the experimental subjects, reducing aggressive interactions in males, while decreasing investigative behaviours in females. At adulthood, AZT inhibited exploratory behaviour in the plus-maze while increasing the frequency of risk-assessment postures in male mice. As for maternal deprivation, this early manipulation exerted a pro-aggressive effect in adolescent male mice, deprived subjects being overall characterised by higher activity levels and a deficit in habituation, an effect also observed in the plus-maze. A significant interaction between AZT and maternal deprivation was found for affiliative behaviours. As for corticosterone levels, no AZT effect was found, while maternal deprivation tended to reduce elevations of this hormone in response to stressful stimuli. Overall results from this study indicate that both AZT exposure and maternal deprivation induced gender-dependent changes in social and emotional behaviour both during adolescence and at adulthood.

Effects of Prenatal AZT on Mouse Neurobehavioral Development and Passive Avoidance Learning

Recent evidence has shown that perinatal administration of zidovudine (AZT) to HIV-infected mothers reduces the risk of maternal-infant transmission of the virus. Treatment of pregnant seropositive women with AZT is becoming a common medical practice, despite the paucity of information about the potential neurotoxic/behavioral-teratogenic effects of AZT on the developing organism. The aim of the present study is to evaluate in mice the short-, medium-, and long-term effects of prenatal exposure to AZT on neurobehavioral development. Pregnant mice were given 0.2, 0.4, and 2.0 mg/ml AZT in drinking water from day 10 of gestation to delivery. Offsprings viability was severely affected in the 2.0 mg/ml AZT group. Thus, behavioral analysis was carried out in offspring of 0.2 and 0.4 mg/ml AZT-treated females only. Some limited but significant alterations were found, such as stunted body weight, delayed appearance of the pole-grasping reflex, and a slight impairment in the acquisition phase of a passive avoidance response. Moreover, sexual differences in some items of the social behavior repertoire appeared to be affected by AZT treatment.

Acute global anoxia during C-section birth affects dopamine-mediated behavioural responses and reactivity to stress.

Perinatal asphyxia may induce major neurological deficits shortly after birth as well as neurological/behavioural disorders later in development. We used a rat model of global perinatal asphyxia to model acute intrauterine asphyxia around the time of birth. Caesarean section was performed in rats and their pups, still in uterus horns, were placed into a water bath at 37 degrees C for periods of 0, 10 or 20 min. Pups were then given to surrogate mothers, and examined for long-term behavioural effects of the perinatal asphyctic insult. Behavioural assessment included analysis of novelty seeking behaviour at adolescence, while spatial discrimination abilities, response to both an acute and a chronic stress, and the effects of the full D1 receptor agonist SKF 82958 on open field behaviour were assessed at adulthood. Overall, no marked abnormalities were found in the novelty seeking test, in the ability to discriminate spatial changes in the test environment and in physiological response to stress. However, adult rats subjected to severe perinatal asphyxia (20 min) showed lower activity level and lower stereotyped behaviour after the administration of SKF 82958 in an open field test. These results support the observations from human and animal studies that perinatal insult can produce long-term dysfunction of dopaminergic neurotransmission, and points to the need of more thorough examination of the potential effects of perinatal asphyxia on hypothalamic-pituitary-adrenal (HPA) axis. Altogether, the present findings suggest that the present 20 min perinatal asphyxia model might serve for the study of neurodevelopmental disorders associated with perinatal insults.

Increased Brain Levels of F2-Isoprostane Are an Early Marker of Behavioral Sequels in a Rat Model of Global Perinatal Asphyxia

Perinatal asphyxia is a major cause of immediate and postponed brain damage in the newborn. It may be responsible for several delayed neurologic disorders and, in this respect, early markers of brain injury would be relevant for therapeutic intervention as well as for identification of infants at high risk for developmental disabilities. Biochemical measurements (brain F2-isoprostane levels) and behavioral tests (ultrasonic vocalization pattern on postnatal days (pnd) 5, 8, and 11, spontaneous motor behaviors on pnd 7 and 12, and homing response on pnd 10) were performed in a rat model of global perinatal asphyxia in the immature neonate. Caesarean section was performed in rats and the pups, still in uterus horns, were placed into a water bath at 37°C for either 10 or 20 min. Caesarean delivered pups were used as controls. Pups experiencing severe (20 min), in contrast to those undergoing the 10 min, asphyctic insult presented with detectable abnormalities including early (two hours after the insult) increase in brain F2-isoprostane (a direct marker of oxidative injury) without detectable changes in PGE2, COX-2 and iNOS levels, and delayed physical (reduced weight gain on pnd 5 and thereafter) and behavioral disturbances (alterations in ultrasound emission on pnd 11 and spontaneous motricity levels mainly). These findings suggest that increased brain F2-isoprostane levels shortly after the asphyctic insult are predictive of delayed behavioral disturbances in the newborn rat. The present 20-min asphyxia model might serve for the assessment of preventive and curative strategies to treat neurologic/behavioral disturbances associated with perinatal asphyxia.

C-section birth per se or followed by acute global asphyxia altered emotional behaviour in neonate and adult rats

Birth complications such as perinatal asphyxia are considered risk factors for later neurobehavioural disorders. Behavioural analysis of animal models may help to clarify the contribution of particular patterns of early hypoxia and their combination to psychiatric morbidity. Wistar rats underwent caesarean section (c-section) alone or c-section followed by asphyxia, the latter induced by placing pups still in uterus horns into a water bath at 37 degrees C for 20 min. Vaginally delivered pups were used as controls. Frequency of ultrasound emissions was analysed following isolation at a lower temperature than that of the home nest (23+/-0.5 degrees C) and reunion with their mother (3 min) on postnatal day (PND) 13 (maternal potentiation test). A sex-dependent effect of hypoxia was observed, with higher production of ultrasounds in hypoxic males. Caesarean-delivered pups produced significantly more ultrasounds than those vaginally delivered. At adolescence (PND 35) rats underwent a 25 min social interaction test with a conspecific of the same sex and age. Significant alterations in investigative behaviour (inclusive of: nose, anogenital, body sniffing, and following) were evident in caesarean-delivered rats of both sexes, but not in rats experiencing perinatal asphyxia. At adulthood, auditory, and context conditioned responses, analysed in a fear conditioning test, were not markedly affected either by c-section or c-section plus hypoxia. However, hypoxic rats emitted significantly more 22 kHz ultrasounds than c-section or vaginally delivered rats during the training session. In conclusion, differential effects appear to be brought about by c-section and by hypoxia mainly related to emotional/anxious responses.

Prenatal exposure to anti-HIV drugs: Neurobehavioral effects of zidovudine (AZT) + lamivudine (3TC) treatment in mice

BACKGROUND The new antiretroviral treatments that combine the zidovudine (AZT) regimen with lamivudine (3TC) appear as a cost-effective alternative to the current AZT monotherapy to prevent mother-to-fetus transmission of the HIV-1 virus. Recent evidence in uninfected children raised concern about the long-term effects of perinatal exposure to AZT and 3TC, especially when used in combination. Animal studies indicated behavioral changes in offspring exposed perinatally to both AZT and 3TC, whereas no animal data are available on the effects of the perinatal exposure to the AZT + 3TC combination on neurodevelopment. METHODS Pregnant CD-1 mice received p.o. AZT + 3TC (160 and 500 mg/kg, respectively) or vehicle solution (NaCl 0.9%) twice daily from gestational day 10 to delivery. Maternal reproductive endpoints such as pregnancy length, abortion, litter size, sex ratio, and offspring viability were assessed. Pups were scored for different somatic and behavioral endpoints, including sensorimotor development, homing performance on postnatal day (PND) 10, passive-avoidance testing (PND 22-23), locomotor activity (PND 23), and social interaction (PND 35). RESULTS While no effects were observed on maternal reproductive endpoints, treated pups showed a long-lasting reduction of body weight and a slightly delayed maturation of placing and grasping reflexes and pole grasping. No effects on passive-avoidance or locomotor activity were found. AZT + 3TC-treated mice showed selective alterations in the social interaction test; the treated female offspring also displayed a significant reduction of affiliative interactions. CONCLUSIONS The combination of AZT and 3TC (1) induced small, but more marked, effects on somatic and sensorimotor development than either of these drugs administered separately; and (2) affected juvenile social behavior.

Neonatal basal forebrain cholinergic hypofunction affects ultrasonic vocalizations and fear conditioning responses in preweaning rats.

The present study investigated the effects of intracebroventricular injections of 192 IgG-saporin in 7-day-old rats on (i) ultrasound vocalizations (USVs) on postnatal day (pnd) 13 following isolation and reunion with the mother and (ii) fear conditioning on pnd 18-19 recording both freezing and other behavioural responses as well as USVs. On pnd 13 lesioned and control pups showed comparable USV baseline values; a brief reunion with the mother induced a significant increase in USVs in all rats (maternal potentiation). On pnd 18, during the fear conditioning training, 192 IgG-saporin rats emitted a lower number of USVs. On pnd 19 all rats showed a stronger conditioned response (with full inhibition of locomotion) to auditory than to contextual cues. Surprisingly, lesioned rats showed a stronger fear-conditioned response to contextual cues than controls. These results suggest that early selective removal of the cholinergic basal forebrain paradoxically enhances hippocampally dependent fear-conditioned responses on pnd 19.