Altered expression of cyclooxygenase-2, presenilins and oxygen radical scavenging enzymes in a rat model of global perinatal asphyxia.

Cyclooxygenase-2 (COX-2) and presenilin (PSEN) 1 and 2 genes are regulated during development as well as in pathological conditions associated to hypoxia. In this study, we investigated their patterns of expression during the first 2 weeks of postnatal life in a rat model of moderate global perinatal asphyxia that we have previously reported to be characterized by early oxidative stress and delayed behavioral alterations. In the hippocampus, global perinatal asphyxia induced an early up-regulation COX-2 mRNA (postnatal day, pnd, 1), which preceded those of PSEN 1 and 2 genes, observed at pnd 4. At pnd 11, the expression of all three genes was decreased compared to control animals. In addition, we analyzed the expression of the scavenging enzymes catalase, copper/zinc- and manganese-superoxide dismutase. As for COX-2, the three enzymes were up-regulated in the hippocampus at pnd 1 and returned at or below baseline by pnd 4. In the cortex, only PSEN 1 and 2 showed a moderate up-regulation at pnd 1 followed by a down-regulation at pnd 11. These findings suggest that moderate perinatal hypoxic episodes are associated with a dysregulation of the several genes involved in brain development and anti-oxidant defenses, which follows a rapid and transient oxidative stress. Such alterations are particularly evident in the hippocampus and could represent an adaptive response to the hypoxic condition. The delayed down-regulation of the scavenging enzymes could set the ground for brain damage and delayed behavioral alterations and further support the potential benefit of early anti-oxidant treatments in a short therapeutic window soon after birth.

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 degrees 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.

Developmental exposure to chlorpyrifos alters reactivity to environmental and social cues in adolescent mice.

Neonatal mice were treated daily on postnatal days (pnds) 1 through 4 or 11 through 14 with the organophosphate pesticide chlorpyrifos (CPF), at doses (1 or 3 mg/kg) that do not evoke systemic toxicity. Brain acetylcholinesterase (AChE) activity was evaluated within 24 h from termination of treatments. Pups treated on pnds 1-4 underwent ultrasonic vocalization tests (pnds 5, 8, and 11) and a homing test (orientation to home nest material, pnd 10). Pups in both treatment schedules were then assessed for locomotor activity (pnd 25), novelty-seeking response (pnd 35), social interactions with an unfamiliar conspecific (pnd 45), and passive avoidance learning (pnd 60). AChE activity was reduced by 25% after CPF 1-4 but not after CPF 11-14 treatment. CPF selectively affected only the G(4) (tetramer) molecular isoform of AChE. Behavioral analysis showed that early CPF treatment failed to affect neonatal behaviors. Locomotor activity on pnd 25 was increased in 11-14 CPF-treated mice at both doses, and CPF-treated animals in both treatment schedules were more active when exposed to environmental novelty in the novelty-seeking test. All CPF-treated mice displayed more agonistic responses, and such effect was more marked in male mice exposed to the low CPF dose on pnds 11-14. Passive avoidance learning was not affected by CPF. These data indicate that developmental exposure to CPF induces long-term behavioral alterations in the mouse species and support the involvement of neural systems in addition to the cholinergic system in the delayed behavioral toxicity of CPF.

Developmental exposure to the antiretroviral drug zidovudine increases brain levels of brain-derived neurotrophic factor in mice.

We analyzed brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) protein content in the central nervous system (CNS) of developing and adult mice exposed to the antiretroviral agent zidovudine (AZT) during prenatal and early postnatal period. Pregnant CD-1 mice received per os twice daily AZT (160 mg/kg) or vehicle from gestation day 10 until lactation day 7. BDNF and NGF contents were measured by enzyme immunoassays in male and female offspring on day 7, 21 or 60. In AZT-exposed females, BDNF levels were significantly increased in the hippocampus (days 7 and 21), in the cortex (day 60) and in the hypothalamus (day 21), while in males AZT exposure increased BDNF in the cortex on day 21. These findings support the hypothesis that developmental AZT exposure interferes with CNS development.

NGF induces appearance of adult-like response to spatial novelty in 18-day male mice.

We investigated the effects of Nerve Growth Factor (NGF) administration on the maturation of reactivity to spatial and non-spatial novelty in developing mice. CD-1 mice of both sexes received intracerebral administration of NGF on postnatal day (pnd) 15, and their response to object displacement (spatial novelty) and object substitution (object novelty) were assessed in a spatial open-field with four objects on pnd 18 or 28. On pnd 18, NGF induced only in males precocious appearance of spatial novelty discrimination, while increasing choline acetyltransferase activity in neocortex and hippocampus of both sexes. The behavioral and neurochemical effects disappeared by pnd 28. NGF triggers adult-like responding to spatial novelty in developing mice and such effect is gender-specific.

Long-term effects of developmental exposure to zidovudine on exploratory behavior and novelty discrimination in CD-1 mice.

Long-term changes in exploratory, social and agonistic behavior have been reported in rodents following developmental exposure to zidovudine (AZT), an agent commonly administered to pregnant seropositive women and their neonates to prevent HIV-1 transmission. The present study evaluates the effects of either prenatal or prolonged AZT treatment on spatial and nonspatial novelty discrimination in mice, using an open-field test with four objects, in which responses to both spatial rearrangement of familiar objects and object novelty are assessed. AZT (160 mg/kg) or Saline was given orally twice daily to pregnant mice from gestational days (GD) 10 to 19 (Experiment 1) or from GD 10 to lactation day 10 (Experiment 2). Offspring of both sexes were tested on postnatal day (PND) 28, 45 or 70. Depending on treatment schedule, AZT altered different behavioral responses, males being more affected than females. The prenatal treatment (Experiment 1) reduced exploration of the objects at all ages considered and increased wall and top rearing at ages 45 and 70. Following prolonged treatment (Experiment 2), AZT offspring were markedly more active than controls and displayed more wall rearing at age 70 while showing lower grooming frequency at all ages. Both AZT and control mice failed to respond to object rearrangement at adulthood, a discrepancy from previous data, which is discussed in relation to perinatal stress effects.