Pair-fed Offspring Research Articles

Prenatal exposure to alcohol impairs social play behavior in adolescent male mice

Prenatal ethanol exposure affects brain development and causes neural impairment, leading to both cognitive and behavioral consequences in the offspring. Therefore, the aim of this study was to investigate the impact of prenatal exposure to small amounts of alcohol on social play behavior in adolescent male offspring. Swiss mice were prenatally exposed to ethanol by feeding pregnant dams with a liquid diet containing 25% alcohol-derived calories during gestation (alcohol group). They were then compared to both pair-fed dams that received an isocaloric liquid diet containing 0% alcohol-derived calories (pair-fed group) and dams with ad libitum access to a liquid control diet (control group). Additionally, maternal behavior was evaluated in terms of neural activation indexed via c-fos expression in the prefrontal cortex. Although dams exposed to alcohol during pregnancy did not alter their maternal behavior, the offspring presented a decrease in their social play behavior compared with both control and pair-fed offspring. The decrease in social play behavior may be associated with a decrease in number of c-fos-positive cells in the prefrontal cortex. The exposure to small amounts of alcohol during intrauterine development causes both a deficit in social play behavior and a reduction in the neuronal activity seen in the prefrontal cortex.

Full‐gestational exposure to nicotine and ethanol augments nicotine self‐administration by altering ventral tegmental dopaminergic function due to NMDA receptors in adolescent rats

In adult rats, we have shown full-gestational exposure to nicotine and ethanol (Nic + EtOH) augmented nicotine self-administration (SA) (increased nicotine intake) compared to pair-fed (PF) offspring. Therefore, we hypothesized that full-gestational exposure to Nic + EtOH disrupts control of dopaminergic (DA) circuitry by ventral tegmental area (VTA) NMDA receptors, augmenting nicotine SA and DA release in nucleus accumbens (NAcc) of adolescents. Both NAcc DA and VTA glutamate release were hyper-responsive to intra-VTA NMDA in Nic + EtOH offspring versus PF (p = 0.03 and 0.02, respectively). Similarly, DA release was more responsive to i.v. nicotine in Nic + EtOH offspring (p = 0.02). Local DL-2-Amino-5-phosphonopentanoic acid sodium salt (AP5) (NMDA receptor antagonist) infusion into the VTA inhibited nicotine-stimulated DA release in Nic + EtOH and PF offspring. Nicotine SA was augmented in adolescent Nic + EtOH versus PF offspring (p = 0.000001). Daily VTA microinjections of AP5 reduced nicotine SA by Nic + EtOH offspring, without affecting PF (p = 0.000032). Indeed, nicotine SA in Nic + EtOH offspring receiving AP5 was not different from PF offspring. Both VTA mRNA transcripts and NMDA receptor subunit proteins were not altered in Nic + EtOH offspring. In summary, adolescent offspring exposed to gestational Nic + EtOH show markedly increased vulnerability to become dependent on nicotine. This reflects the enhanced function of a subpopulation of VTA NMDA receptors that confer greater nicotine-induced DA release in NAcc. We hypothesized that concurrent gestational exposure to nicotine and ethanol would disrupt the control of VTA dopaminergic circuitry by NMDA receptors. Resulting in the augmented nicotine self-administration (SA) in adolescent offspring.

Hyperactivity, increased nicotine consumption and impaired performance in the five-choice serial reaction time task in adolescent rats prenatally exposed to nicotine

Prenatal exposure to nicotine has been linked to accelerated risk for different psychiatric disorders, including conduct disorder, attention deficit hyperactivity disorder (ADHD) and drug abuse. We examine a potential link between prenatal nicotine exposure, hyperactivity, anxiety, nicotine consumption, and cognitive performance in rats. Adolescent offspring of females exposed during pregnancy to 0.06 mg/ml nicotine solution as the only source of water and of a group of pair-fed females, used as a control for anorexic effects of nicotine, were evaluated in a battery of tests, including locomotor activity, the elevated plus maze, two-bottle free-choice nicotine solution consumption, the five-choice serial reaction time test (5-CSRTT) and a delay-discounting test. All tests were conducted between postnatal day (PND) 25 and PND 50. Nicotine-exposed animals expressed hyperactivity, increased number of open arms entries in the elevated plus maze and increased numbers of anticipatory responses in the 5-CSRTT. Decreased aversion for nicotine solution in the free-choice test and decreased numbers of omission errors in the 5-CSRTT were observed both in nicotine-exposed and pair-fed offspring. Neither nicotine exposure nor pair-feeding had an effect on impulsive choice in a delay-discounting test. Our study confirms deleterious effects of prenatal nicotine exposure on important aspects of behaviour and inhibitory control in adolescent rats and supports epidemiological findings that show increased levels of symptoms of ADHD and related disorders among those whose mothers smoked during their pregnancy. It also suggests a link between food restriction during pregnancy and addiction-related behaviours in offspring.

Maternal obesity is necessary for programming effect of high-fat diet on offspring

We tested the hypothesis that maternal consumption of dietary fat, independent from obesity, increases serum leptin in neonatal pups and predisposes them to adult obesity. Female rats either were fed a high-fat (HF) diet or a low-fat (LF) diet or were fed the HF diet but pair fed (PF) to the caloric intake of the LF group for 4 wk before breeding and throughout gestation and lactation. Dams consuming the HF diet had increased adiposity and were hyperphagic. At weaning, pups born to obese dams had significantly higher body fat and serum leptin levels and reduced insulin tolerance compared with offspring of LF-fed dams. Pups were weaned onto a chow diet until 8 wk of age, when they were then fed either HF or LF diet. At 18 wk of age, offspring from obese HF dams weighed more than offspring from nonobese LF or PF dams, and offspring eating HF diet weighed significantly more than those eating LF diet. Consequently, HF-fed offspring of obese HF dams weighed the most and LF-fed offspring from obese HF dams were similar in weight to HF-fed offspring from nonobese LF dams. These data suggest that maternal obesity exerts an independent effect on offspring body weight that is of similar magnitude as the effect of the offspring's adult diet. Furthermore, there was no difference in body weight between the nonobese LF and PF offspring on either diet. Together, these data suggest that maternal adiposity, and not dietary fat per se, induces hyperleptinemia and insulin resistance in offspring, as well as an increased body weight that persists into adulthood.

Prenatal ethanol preferentially enhances reactivity of the dopamine D 1 but not D 2 or D 3 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 D 2 (Apomorphine, DPAT or Quinpirole) or D 3 (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 D 1 receptor. Both D 1 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 D 1 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 D 1 agonists and antagonists, which can be intensified by gestational exposure to alcohol.

Gender differences in the effect of prenatal alcohol exposure on the hypothalamic-pituitary-adrenal axis response to immune signals.

Immature (3 week old) rat offspring of alcohol (E)-fed dams show a blunted ACTH response to immune signals such as interleukin-1 beta (IL-1 beta) and endotoxin (LPS). In contrast, mature offspring respond to physical stresses with an exaggerated activation of their hypothalamic-pituitary-adrenal (HPA) axis. The present work was aimed at determining if there was a differential influence of prenatal E exposure on the HPA axis responses to various stressors or if, alternatively, sexual maturation modified these responses. When administered IL-1 beta at 5 weeks age, E-treated intact male offspring released less ACTH, compared to control (C) or pair-fed (PF) animals. However, they showed an augmented response to LPS and a local inflammatory process induced by turpentine injection. At this same age, intact E females secreted significantly more ACTH in response to IL-1 beta, LPS and turpentine, than C or PF offspring. By 9 weeks of age, both E males and E females exhibited larger (p < .05) ACTH responses to all three immune stimuli. In order to determine whether sex steroids modulate the influence of E in females, ovariectomy was done prior to puberty. This treatment decreased the difference in the ACTH released by E and C rats in response to IL-1 beta, LPS and turpentine. These results show that while immature rats exposed to E prenatally released less ACTH in response to cytokines than C or PF animals did, this response was qualitatively reversed after puberty. At that time, the larger amounts of ACTH secreted by E offspring, compared to the other groups, were reminiscent of the hyperactive response of the HPA axis when these offspring were exposed to physical stress. Interestingly, removal of circulating ovarian steroids prevented the influence of E from being exerted. This suggests the presence of a functional relationship between the pathways influenced by prenatal E and those influenced by female sex steroids, that are important in regulating the activity of the HPA axis.

Chronic prenatal ethanol exposure alters the normal ontogeny of choline acetyltransferase activity in the rat septohippocampal system.

In animal models of fetal alcohol syndrome (FAS), the hippocampus has been shown to be especially sensitive to the effects of prenatal ethanol exposure, exhibiting neuronal loss and alterations in neuritic process elaboration. We have characterized the influence of chronic prenatal ethanol treatment (CPET) on the postnatal expression of choline acetyltransferase (ChAT) in the hippocampus and the septal area that contains neurons that provide the primary cholinergic innervation to the hippocampus. On gestation days 1-22, pregnant rats were either fed an ethanol-containing liquid diet, pair-fed a calorically equivalent sucrose-containing diet, or given rat chow ad libitum. In Chow control animals, the ontogenetic progression of ChAT activity in the septal area and hippocampus was characterized by a significant period of upregulation during the 2nd and 3rd postnatal weeks, exhibiting and an approximate 5-fold increase (septal area) and 7-fold increase (hippocampus) by postnatal day 21 (P21). At P14, ethanol exposure reduced septal and hippocampal ChAT activity levels, compared with those of pair-fed offspring. ChAT activity reached control levels by P21 in ethanol-exposed pups, suggesting that the earlier decline in activity may reflect a delay in the ontogenetic upregulation. In addition, there was a trend toward increased septal and hippocampal ChAT activities at P1 and P7 in both liquid diet groups. This liquid diet-stimulated increase may mask the effects of ethanol on early postnatal ChAT expression in the septohippocampal system. The results suggest that prenatal ethanol exposure may influence factors that regulate the developmental expression of ChAT in the septohippocampal system.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal cocaine exposure on postnatal growth patterns of male Wistar rats.

The purpose of this study was to investigate basic parameters regarding the postnatal effects of prenatal exposure to cocaine. Timed-pregnant Wistar rats were injected SC with 60 mg/kg body weight/day of cocaine from gestational day 8 to 22. Control females were nonmanipulated and given food and lib; saline females received saline injections and pair-fed received saline and were nutritionally controlled to the cocaine-treated rats. Litters were restricted to 8 pups, weighed every other day until postnatal day (PND) 30 and every week from PND 30 to PND 90. The rats were perfused at PND 14, 30, and 90. The adequacy of adjustment of the logistic and Gompertz models to the body weights of the offspring was tested for the whole experimental period. The results from the Gompertz curve showed a higher growth rate and less time to reach 37% of expected mature body mass for the offspring of cocaine and pair-fed dams as compared with that of control and saline dams. No significant differences in the estimated adult weight were found among the experimental groups. The allometric relationship between forebrain and body weight is described by two postnatal growth phases with a first phase of rapid growth between PND 14 and 30 and a decelerating phase between PND 30 and 90. This relationship was not different among the experimental groups; however, the cocaine and pair-fed offspring showed a constant deficit in the forebrain weight as compared with the control and saline offspring.(ABSTRACT TRUNCATED AT 250 WORDS)

Prenatal ethanol exposure: Effects on androgen and nonandrogen dependent behaviors and on gonadal development in male rats

Prenatal exposure to alcohol may impair gonadal and behavioral development in male rats, possibly via reduction of perinatal androgenization. We examined locomotor activity on postnatal day 18 (PND 18), which is not influenced by perinatal androgens and juvenile play and testicular development (testes weight), which are dependent on perinatal androgen exposure, in rats whose dams consumed ethanol during pregnancy. Male offspring of pair-fed and lab chow-fed dams served as controls. Despite reduced anogenital distance at birth, indicating compromised perinatal androgenization, fetal ethanol-exposed males did not exhibit demasculinization of play behavior. Hyperactivity in fetal ethanol-exposed males indicated that the treatment regimen was sufficient to produce behavioral deficits. Testes weight was reduced in both ethanol-exposed and pair-fed offspring, indicating that nutritional deficits associated with maternal ethanol intake may impair normal gonadal development in male rats. The findings suggest that fetal ethanol exposure may influence gonadal development but not necessarily affect a gonadal hormone-dependent behavior.

The effects of prenatal cocaine exposure on spontaneously active midbrain dopamine neurons in adult male offspring: an electrophysiological study

In this study, the technique of extracellular single unit recording was used to examine the effect of prenatal cocaine exposure on the number of spontaneously active dopamine (DA) cells in the substantia nigra pars compacta (SNC or A9) and the ventral tegmental area (VTA or A10) of male Sprague-Dawley rats on postnatal days 56–68. In addition, the effect of the direct DA receptor agonist (±)-apomorphine (APO) on the basal firing rate of A10 DA cells was also determined. A significant decrease in the number of spontaneously active A10 DA cells was observed in offspring whose dams were treated with 40 mg/kg/day of cocaine s.c. from gestational days 8–20 when compared with offspring of pair-fed and non-treated control dams. The number of spontaneously active A9 DA cells was significantly decreased in the offspring of cocaine-exposed dams when compared to pair-fed offspring. In contrast, there were no significant differences among the three prenatal groups regarding the sensitivity of spontaneously active A10 DA cells to APO (2–64 μg/kg, i.v.). Overall, our results suggest that in utero cocaine exposure may alter presynaptic DA activity in offspring long after their exposure has been terminated.

Prenatal exposure to cocaine disrupts cocaine-induced conditioned place preference in rats

Cocaine-induced conditioned place preference (CPP) was tested in adult offspring of Sprague-Dawley dams that had been injected subcutaneously with 40 mg/kg/3cc cocaine HCl (C40) daily from gestational days 8–20, pair-fed (PF) dams injected with saline, and nontreated control (LC) dams. C40 and PF dams gained significantly less weight than LC dams, although offspring body weights did not differ among the three prenatal treatment groups at birth or in adulthood. Significant place conditioning was obtained in LC and PF offspring when either 2.0 or 5.0 mg/kg of cocaine was paired with the designated place. In contrast, C40 offspring did not exhibit place conditioning at either training dose. Yet, all animals exposed to 5 mg/kg of cocaine during conditioning exhibited less activity during the test (when no cocaine was given) than controls given unpaired exposures to the apparatus and cocaine and C40 offspring did not differ from LC and PF offspring in this respect. Therefore, despite their lack of a conditioned place preference for cocaine, rats that had been exposed gestationally to cocaine nevertheless revealed an effect of cocaine during conditioning in one aspect of their test behavior. Possible explanations for the lack of cocaine-induced place preference in these animals include a learning deficit or a change in cocaine's effectiveness as a reward.

Prenatal cocaine exposure in the Long-Evans rat: II. Dose-dependent effects on offspring behavior

Pregnant Long-Evans rats were injected daily with 40, 60, 80 or 100 mg/kg cocaine HCl (SC, 2% solution) from gestational days 7–20 (sperm positive = day 0). Daily doses were split with half given between 9:00–10:00 a.m. and half between 3:00–4:00 p.m. An ad lib-fed group as well as nutritional control groups that were pair-fed to the 80 and 100 mg/kg cocaine dams were also evaluated (N = 11–18 litters/group). The negative geotactic reaction of the offspring, evaluated from day 2–14 (birth = day 0), showed no group differences. Spontaneous alternation behavior in a T-maze showed no evidence of perseveration in any group on either day 21 or day 80. Most cocaine-treated offspring showed an altered preference in turning right versus left on day 21. Activity monitor behavior showed that the cocaine-treated and pair-fed offspring were hypoactive on day 20. Some degree of hypoactivity was still evident on day 49, but absent on day 80. The passive avoidance behavior of day 19 offspring showed no group differences in acquisition of task learning. The 100 mg/kg cocaine offspring did show significantly poorer retention of task learning 48 hr later. On day 80, no group differences were seen in passive avoidance behavior. Acquisition of an active avoidance behavior on day 80 was significantly poorer in the 100 mg/kg cocaine group.

Prenatal ethanol and ontogeny of pituitary-adrenal responses to ethanol and morphine

The development of pituitary-adrenal activity was examined in the offspring of rat dams fed a 5.0% w/v ethanol-containing liquid diet or pair-fed an isocaloric diet, as a nutritional control, from day 8 of gestation to parturition. Serum corticosterone responses of the pups to challenges with ethanol (1.5 g/kg) or morphine (3.0 mg/kg) were determined at 5, 7, 10, 12 and 18 days of age. The pituitary-adrenal axis of normal neonates was activated by the drugs at each age, with a characteristic biphasic developmental pattern in which a trough occurred at day 7. The overall pattern was unaffected by prenatal ethanol exposure or pair-feeding. However, both prenatal treatments intensified the trough. Already on day 5 and also on day 7, corticosterone responses of both the ethanol-exposed and pair-fed offspring to ethanol were significantly lower than responses of normal pups. Additionally, on day 7, ethanol-exposed offspring had significantly lower responses to ethanol than pair-fed offspring and significantly lower responses to morphine than normal pups. Thus, both the prenatal ethanol and pair-feeding treatments suppressed pituitary-adrenal responsiveness of 5 and 7 day-old neonates to the drug challenges. This is in marked contrast to our previous findings for adult prenatally ethanol-exposed offspring whose pituitary-adrenal responses to the same drugs, as well as to other stressors, are consistently enhanced in comparison to pair-fed derived rats, whose responses in adulthood no longer differ from normals.

Recovery of spinal cord volume in postnatal rats following prenatal exposure to morphine.

A previous study has shown that the spinal volume of 18-day fetal rats is decreased by 20% after maternal administration of morphine on gestation days 12-18. In the present study, the volume of the first thoracic spinal cord segment was measured in offspring of morphine or saline-injected and pairfed dams on days 6, 15 and 80 postnatally. The following volumes were measured within the segment: hemisegment, gray matter, white matter, dorsal horn, ventral horn and length. On the sixth day postnatally, the hemisegment, gray matter and dorsal horns are significantly reduced in morphine-treated and pairfed offspring. By the fifteenth day postnatally, only the gray/white ratio is reduced while the length of the segment is significantly increased in morphine-treated fetuses. The spinal measurements in pairfed offspring are normal by 15 days postnatally. These results indicate that the effect of morphine on developing spinal cord may be partially due to undernutrition; however, morphine causes a more pronounced and longer-lasting effect than undernutrition alone.