Central and peripheral neurochemical alterations and immune effects of prenatal ethanol exposure in rats

How neuroactive factors mediates immune responses during pregnancy: An interdisciplinary view

Pregnancy, from insemination to parturition, is a highly complex but well-orchestrated process that requires various organs and systems to participate. Immune system and neuroendocrine system are important regulators in healthy pregnancy. Dozens of neuroactive factors have been detected in human placenta, whether they are locally secreted or circulated. Among them, some are vividly studied such as corticotropin-releasing hormone (CRH), human chorionic gonadotropin (hCG), transforming growth factor-β (TGF-β), progesterone and estrogens, while others are relatively lack of research. Though the neuroendocrine-immune interactions are demonstrated in some diseases for decades, the roles of neuroactive factors in immune system and lymphocytes during pregnancy are not fully elucidated. This review aims to provide an interdisciplinary view on how the neuroendocrine system mediate immune system during pregnancy process.

Prenatal alcohol exposure reduces 5-HT concentration in mouse intestinal muscle and mucosa

The influence of prenatal alcohol exposure on the serotoninergic system in the brain has been well studied, however its influence on the serotoninergic system in the gastrointestinal system remains unknown. The objective of the study was to use a mouse model of prenatal alcohol exposure to investigate the effects on serotonin and its metabolites and precursors in colonic tissue. This study used treatment of mouse breeding harems with 5% ethanol with saccharin via drinking water throughout pregnancy and compared the results with a saccharin control group. Tryptophan, serotonin (5-HT) and 5- hydroxyindoleacetic acid (5-HIAA) concentrations were measured in the longitudinal muscle myenteric plexus (LMMP) and mucosa of intestinal tissue by high-performance liquid chromatography (HPLC). Decreased 5-HT concentrations in mucosa and LMMP (females only) were observed in prenatally exposed mice compared to controls. Increases in mucosal and LMMP tryptophan concentration were only observed in prenatally exposed female mice. In conclusion, prenatal alcohol exposure causes a decrease in conversion of tryptophan to 5-HT in both muscle and mucosa although the effect is more pronounced in females. The observed sex difference may be related to changes associated with the estrous cycle.

Prenatal alcohol exposure alters the course and severity of adjuvant-induced arthritis in female rats

Prenatal alcohol exposure (PAE) has adverse effects on the development of numerous physiological systems, including the hypothalamic-pituitary-adrenal (HPA) axis and the immune system. HPA hyper-responsiveness and impairments in immune competence have been demonstrated. The present study investigated immune function in PAE females utilizing an adjuvant-induced arthritis (AA) model, widely used as a model of human rheumatoid arthritis. Given the effects of PAE on HPA and immune function, and the known interaction between HPA and immune systems in arthritis, we hypothesized that PAE females would have heightened autoimmune responses, resulting in increased severity of arthritis, compared to controls, and that altered HPA activity might play a role in the immune system changes observed. The data demonstrate, for the first time, an adverse effect of PAE on the course and severity of AA in adulthood, indicating an important long-term alteration in functional immune status. Although overall, across prenatal treatments, adjuvant-injected animals gained less weight, and exhibited decreased thymus and increased adrenal weights, and increased basal levels of corticosterone and adrenocorticotropin, PAE females had a more prolonged course of disease and greater severity of inflammation compared to controls. In addition, PAE females exhibited blunted lymphocyte proliferative responses to concanavalin A and a greater increase in basal ACTH levels compared to controls during the induction phase, before any clinical signs of disease were apparent. These data suggest that prenatal alcohol exposure has both direct and indirect effects on inflammatory processes, altering both immune and HPA function, and likely, the normal interactions between these systems.

Age and gender differences in response to neonatal ethanol withdrawal and polyamine challenge in organotypic hippocampal cultures

BACKGROUND

Polyamines are synthesized and released in high concentrations during CNS development. These agents can potentiate N-methyl-D-aspartate receptor (NMDAR) function and appear to play an important role in CNS development. Previous work has shown that polyamine release is increased during ethanol withdrawal (EWD). This likely promotes NMDAR overactivity and contributes to neurotoxicity during EWD, however, little is known regarding such effects in early neonatal brain. The present study compared the effects of EWD and polyamine exposure on toxicity in hippocampal slice cultures derived from postnatal day 2 (PND 2) or postnatal day 8 (PND 8) day-old rats. Due to changes in NMDAR subtypes and response to polyamines, we predicted that slices taken from PND 2 pups would be more sensitive to EWD and polyamine challenge.

METHODS

Organotypic hippocampal slice cultures were obtained from neonatal rats either 2 or 8 days of age (PND 2 or PND 8). Five days after explantation, cultures were exposed to ETOH (50 mM- typically subthreshold for EWD induced cell death) for 10 days and then withdrawn from ETOH for 24-hour in the presence of 100 microM of the polyamine spermidine and/or 100 microM ifenprodil, an NMDAR antagonist that blocks the NMDAR that is the most sensitive to polyamine modulation. Cytotoxicity was measured after 24-hour by visualization of propidium iodide (PI) fluorescence.

RESULTS

There were clear age and gender-dependent differences in response to EWD and to polyamines. EWD produced significant increases in PI uptake in all subregions (CA1, CA3 and DG) of cultures derived from PND 2 pups, but not PND 8 pups. Exposure of cultures to spermidine for 24-hour also produced significant increases in cytotoxicity in all 3 regions of PND 2 cultures with no gender differences. In contrast, there were both gender and region-specific differences in response to spermidine in cultures from PND 8. While the CA1 region of both sexes displayed increased cytotoxicity following spermidine exposure, only females showed increased cytotoxicity in the CA3 region while the DG appeared relatively insensitive to spermidine. Exposure to spermidine during EWD produced enhanced toxicity in all 3 hippocampal subregions in tissue from both PND 2 and PND 8 rats and this was reduced or prevented by co-exposure to ifenprodil. Of interest, the PND 2 hippocampus was significantly more sensitive than the PND 8 hippocampus to the toxic effects of EWD and to spermidine during EWD in the DG and CA3 regions.

CONCLUSIONS

Hippocampal slice cultures derived from PND 2 rats were more sensitive to the toxic effects of both EWD and EWD + spermidine exposure than were those derived from PND 8 rats. These findings are similar to recent behavioral data collected from our lab showing greater sensitivity to ETOH's behavioral teratogenic effects when ETOH exposure in vivo occurred during the first postnatal week relative to the second postnatal week. Ifenprodil's ability to block the toxic effects of spermidine during EWD suggests that excess activity of NR2B subunits of the NMDAR contributed to the excitatory and cytotoxic effects of EWD plus spermidine. While no sex differences in toxicity were observed in cultures taken from pups during the first postnatal week, these data do suggest that later in neonatal life (i.e., the second postnatal week), the female hippocampus may be more sensitive to polyamine-induced neurotoxicity than males.

Prenatal ethanol exposure: Sex differences in anxiety and anxiolytic response to a 5-HT1A agonist

This study utilized a novelty-induced suppression of feeding task to examine anxiety-like behaviour and the anxiolytic effects of the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), in rats prenatally exposed to ethanol. Adult offspring from ethanol exposed (E), pair-fed control (PF) and ad libitum-fed control (C) dams were habituated to a novel palatable food for 21 days and measures of baseline feeding obtained. On day 22 (d 22), animals received either 8-OH-DPAT (0.06 mg/kg) or vehicle (0.9% NaCl) and feeding behaviour in the home cage or a novel cage was observed. Factor analyses revealed that feeding behaviour on d 21 (habituation) and d 22 (test day) are reflective of two different affective states, and that the single factor that emerged for novel cage testing on d 22 likely reflects the anxiety evoked by the novel test condition. Analyses of variance on the variables loading significantly onto the factors support the suggestion that the novel environment is anxiogenic for both females and males, and that 8-OH-DPAT acts as an anxiolytic. However, although both females and males showed alterations in behaviours (latency, amount, duration of feeding) reflective of anxiety, 8-OH-DPAT had anxiolytic effects primarily in females. Importantly, prenatal ethanol exposure altered several aspects of behavior in this task. Both E females and males consumed less than their control counterparts on d 21, suggesting a possible delay or deficit in response habituation. During home cage testing on d 22, overall feeding rate was slower in E than in C females, and E males consumed less than PF and C males. In addition, a smaller percentage of E than PF and C females fed in the novel environment, and latency to feed was significantly increased in E compared to control females. These findings indicate that prenatal ethanol exposure results in increased anxiety-like behaviour in adulthood, and that prenatal ethanol-induced hyponeophagia may be, at least in part, mediated by the 5-HT1A receptor. This study is one of the first to demonstrate specific increases in anxiety-like behaviour in animals prenatally exposed to ethanol, and further supports the utility of the novelty-induced suppression of feeding task in assessing anxiety and the effectiveness of anxiolytic agents.

Prenatal ethanol preferentially enhances reactivity of the dopamine D1 but not D2 or D3 receptors in offspring

Reports of prenatal ethanol (ETOH) effects on the dopamine system are inconsistent. In an attempt to clarify this issue, dams were given 35% ethanol-derived calories as the sole nutrient source in a liquid diet from the 10th through the 20th day of gestation (ETOH). Controls were pair-fed (PF) an isocaloric liquid diet or given ad libitum access to laboratory chow (LC). Prenatal exposure to both liquid diets reduced body weight of offspring relative to LC controls, more so for ETOH than for PF exposure. Prenatal ETOH also decreased litter size and viability, relative to both LC and PF control groups. On postnatal days 21-23, male and female offspring were given an injection of saline vehicle or one of eight specific dopamine receptor agonists or antagonists. Immediately after injection subjects were placed in individual observation cages, and over the following 30 min, eight behaviors (square entries, grooming, rearing, circling, sniffing, yawning, head and oral movements) were observed and quantified. No prenatal treatment effects on drug-induced behaviors were observed for dopamine D2 (Apomorphine, DPAT or Quinpirole) or D3 (PD 152255, Nafadotride, Apo or Quin effects on yawning) receptor agonists or antagonists, or for the vehicle control. In contrast, prenatal treatment effects were seen with drugs affecting the dopamine D1 receptor. Both D1 agonists (SKF 38393) and antagonists (SCH 23390 and high doses of spiperone) altered behaviors, especially oral and sniffing behaviors, in a manner which suggested enhanced dopamine D1 drug sensitivity in both ETOH and PF offspring relative to LC controls. These results suggest that at this age, both sexes experience a prenatal undernutrition-linked increase in the behavioral response to dopamine D1 agonists and antagonists, which can be intensified by gestational exposure to alcohol.

Preweaning experience as a modifier of prenatal drug effects in rats and mice--a review

The effects of preweaning experience in rats and mice on neuroendocrine and behavioral end points and their implications for prenatal drug effects are reviewed. The hypothalamo-pituitary-adrenal axis and the dopaminergic system were shown to be affected. Behavior related to hippocampal, adrenocortical functions and to the benzodiazepine receptor system was also modified. Other paradigms (nociception, conditioned taste aversion) exhibited susceptibility to such preweaning manipulations also. The effects of these early experiences seem to be mediated through complex factors including neuroendocrine responses of the pup to hypothermia and a permanent alteration of mother-infant interactions, with subsequent effects on neuroendocrine functions that are important for postnatal brain organization. Studies of interactions between prenatal drug effects and preweaning manipulations have been performed only with ethanol. When extending this work to other compounds, the systems and functions described above may provide some guidance in looking for possible interactions. In most cases the preweaning manipulations alleviated the effects of prenatal ethanol exposure. These findings may have important implications regarding the controversy about environmental influences affecting the outcome of exposure to neurobehavioral teratogens.