Taste aversion learning in preweanling rats exposed to alcohol prenatally

The effects of prenatal alcohol exposure on the development of a conditioned taste aversion were examined in preweanling rat pups. Mothers of these pups were fed isocaloric liquid diets containing either 35 or 0% ethanol-derived calories (EDC) from gestation days 6 through 20. A pair-feeding procedure was employed, and an ad lib lab chow control group was also included. At 5, 10, or 15 days of age, pups were infused with a saccharin solution through a cannula implanted in the oral cavity. Half of the pups in each group were then injected with lithium chloride (LiCl), which served as the poisoning agent, and the other half with sodium chloride (NaCl) as a control. Animals were subsequently tested for a conditioned aversion to the saccharin solution. At 15 days of age, all of the pups in the LiCl-poisoned group demonstrated a conditioned taste aversion to the saccharin solution, but the degree of this aversion was less in alcohol-exposed offspring. At 10 days of age, a taste aversion was learned, although it was not as strong as that shown by 15-day-old pups, and it appeared to be learned equally well by all of the prenatal treatment groups. At 5 days of age, there was marginal support for taste aversion learning. Again, it did not interact with prenatal treatment. The ontogenic differences in taste aversion learning exhibited by alcohol-exposed offspring relative to controls are discussed in terms of altered hippocampal development.     

Suckling deficits in rat pups exposed to alcohol in utero

With the aid of a pair-feeding procedure, two groups of pregnant Long-Evans rats were fed a liquid diet containing 35% or 0% ethanol-derived calories during days 6-20 of gestation. A third group was allowed free access to standard lab chow and water throughout pregnancy. At 6-7 or 9-10 days of age, suckling performance by male and female offspring representing the three prenatal treatment groups was examined. The test stimulus was a 6-10-day postparturient, anesthetized dam in which milk letdown was prevented. Compared to both pair-fed and lab chow controls, alcohol-exposed animals exerted a lower maximum suckling pressure, spent less time suckling during the test session, and displayed an altered suckling pattern. These data are consistent with existing clinical and experimental evidence documenting sucking deficits following prenatal alcohol exposure and are discussed in terms of prenatal alcohol-induced CNS impairment.     

Dietary sodium manipulation during critical periods in development sensitize adult offspring to amphetamines

This study examined critical periods in development to determine when offspring were most susceptible to dietary sodium manipulation leading to amphetamine sensitization. Wistar dams (n = 6-8/group) were fed chow containing low (0.12% NaCl; LN), normal (1% NaCl; NN), or high sodium (4% NaCl; HN) during the prenatal or early postnatal period (birth to 5 wk). Offspring were fed normal chow thereafter until testing at 6 mo. Body weight (BW), blood pressure (BP), fluid intake, salt preference, response to amphetamine, open field behavior, plasma adrenocorticotropin hormone (ACTH), plasma corticosterone (Cort), and adrenal gland weight were measured. BW was similar for all offspring. Offspring from the prenatal and postnatal HN group had increased BP, NaCl intake, and salt preference and decreased water intake relative to NN offspring. Prenatal HN offspring had greater BP than postnatal HN offspring. In response to amphetamine, both prenatal and postnatal LN and HN offspring had increased locomotor behavior compared with NN offspring. In a novel open field environment, locomotion was also increased in prenatal and postnatal LN and HN offspring compared with NN offspring. ACTH and Cort levels 30 min after restraint stress and adrenal gland weight measurement were greater in LN and HN offspring compared with NN offspring. These results indicate that early life experience with low- and high-sodium diets, during the prenatal or early postnatal period, is a stress that produces long-term changes in responsiveness to amphetamines and to subsequent stressors.     

The effects of maternal corticosterone levels on offspring behavior in fast- and slow-growth garter snakes (Thamnophis elegans)

During embryonic development, viviparous offspring are exposed to maternally circulating hormones. Maternal stress increases offspring exposure to corticosterone and this hormonal exposure has the potential to influence developmental, morphological and behavioral traits of the resulting offspring. We treated pregnant female garter snakes (Thamnophis elegans) with low levels of corticosterone after determining both natural corticosterone levels in the field and pre-treatment levels upon arrival in the lab. Additional measurements of plasma corticosterone were taken at days 1, 5, and 10 during the 10-day exposure, which occurred during the last third of gestation (of 4-month gestation). These pregnant snakes were from replicate populations of fast- and slow-growth ecotypes occurring in Northern California, with concomitant short and long lifespans. Field corticosterone levels of pregnant females of the slow-growth ecotype were an order of magnitude higher than fast-growth dams. In the laboratory, corticosterone levels increased over the 10 days of corticosterone manipulation for animals of both ecotypes, and reached similar plateaus for both control and treated dams. Despite similar plasma corticosterone levels in treated and control mothers, corticosterone-treated dams produced more stillborn offspring and exhibited higher total reproductive failure than control dams. At one month of age, offspring from fast-growth females had higher plasma corticosterone levels than offspring from slow-growth females, which is opposite the maternal pattern. Offspring from corticosterone-treated mothers, although unaffected in their slither speed, exhibited changes in escape behaviors and morphology that were dependent upon maternal ecotype. Offspring from corticosterone-treated fast-growth females exhibited less anti-predator reversal behavior; offspring from corticosterone-treated slow-growth females exhibited less anti-predator tail lashing behavior.     

Paternal alcohol consumption: effects of age of testing and duration of paternal drinking in mice

Male mice consumed liquid alcohol diets containing 25, 20, 15, 10, 5, or 0% ethanol-derived calories (EDC). Animals receiving the 20-0% EDC diets were pair-fed to those consuming the 25% EDC diet. After 7 weeks of consumption males were bred to nontreated females. Offspring were tested for activity at 16-20 and 75 days of age. Offspring sired by alcohol-consuming males did not differ from controls in litter size, birth weight, or weight at weaning, but were less active than controls on several measures of activity. Many of these decreases were best defined in terms of linear trends. However, these differences were evident only for animals tested prior to 20 days of age for most activity measures. In a second experiment adult males continued to consume alcohol for another 7 weeks and were bred again. Offspring of this second breeding were tested for activity at 16 days of age and were compared with offspring sired by the same father from the previous breeding. Offspring sired after this longer duration of paternal alcohol consumption did not differ significantly from controls in any of the above-mentioned variables.     

Prenatal alcohol exposure reduces the proportion of newly produced neurons and glia in the dentate gyrus of the hippocampus in female rats

Prenatal alcohol exposure (PAE) alters adult neurogenesis and the neurogenic response to stress in male rats. As the effects of stress on neurogenesis are sexually dimorphic, the present study investigated the effects of PAE on adult hippocampal neurogenesis under both nonstressed and stressed conditions in female rats. Pregnant females were assigned to one of three prenatal treatments: (1) alcohol (PAE)—liquid alcohol (ethanol) diet ad libitum (36% ethanol-derived calories); (2) pair-fed—isocaloric liquid diet, with maltose–dextrin substituted for ethanol, in the amount consumed by a PAE partner (g/kg body wt/day of gestation); and (3) control—lab chow ad libitum. Female offspring were assigned to either nonstressed (undisturbed) or stressed (repeated restraint stress for 9 days) conditions. On day 10, all rats were injected with bromodeoxyuridine (BrdU) and perfused either 24 hours (cell proliferation) or 3 weeks (cell survival) later. We found that PAE did not significantly alter cell proliferation or survival, whereas females from the pair-fed condition exhibited elevated levels of cell survival compared to control females. Importantly, however, the proportion of both new neurons and new glial cells in the hippocampal dentate gyrus was reduced in PAE compared to control females. Exposure to stress did not alter neurogenesis in any of the prenatal treatment groups. In summary, compared to females from the control condition, prenatal dietary restriction enhanced the survival of new neurons, whereas PAE altered the differentiation of newly produced cells in the adult dentate gyrus. Alterations in hippocampal neurogenesis following PAE may contribute to learning and memory deficits seen in individuals with fetal alcohol spectrum disorders.     

Maternal obesity alters adiposity and monoamine function in genetically predisposed offspring

The impact of maternal obesity on brain monoamine function in adult offspring of dams selectively bred to express diet-induced obesity (DIO) or diet resistance (DR) was assessed by making dams obese or lean during gestation and lactation. After 12 wk on chow and 4 wk on a 31% fat diet, offspring hypothalamic nucleus size and [(3)H]nisoxetine binding to norepinephrine transporters (NET) and [(3)H]paroxetine binding to serotonin transporters (SET) were measured. Offspring of obese DIO dams became more obese than all other groups, but maternal obesity did not alter weight gain in DR offspring (25). Maternal obesity was associated with 10-17% enlargement of ventromedial nuclei (VMN) and dorsomedial nuclei in both DIO and DR offspring. Offspring of obese DIO dams had 25-88% lower NET binding in the paraventricular nuclei (PVN), arcuate nuclei, VMN, and the central amygdalar nuclei, while offspring of obese DR dams had 43-67% higher PVN and 90% lower VMN NET binding and a generalized increase in SET binding across all hypothalamic areas compared with other groups. Thus maternal obesity was associated with alterations in offspring brain monoamine metabolism, which varied as a function of genotype and the development of offspring obesity.     

Maternal gestational androgens are associated with decreased juvenile play in white-faced marmosets (Callithrix geoffroyi)

Exposure to androgens during prenatal development shapes both physiological and behavioral developmental trajectories. Notably, in rhesus macaques, prenatal androgen exposure has been shown to increase rough-and-tumble play, a prominent behavioral feature in males during the juvenile period in primates. While macaques are an Old World, polygamous species with marked sexually dimorphic behavior, New World callitrichine primates (marmosets and tamarins) live in cooperative breeding groups and are considered to be socially monogamous and exhibit minimal sexual dimorphism in social play, which suggests that androgen may affect this species in different ways compared to macaques. In addition, we previously described considerable variation in maternal androgen production during gestation in marmosets. Here we tested the association between this variation and variation in offspring rough-and-tumble play patterns in both males and females. We measured testosterone and androstenedione levels in urine samples collected from pregnant marmoset mothers and then observed their offspring's play behavior as juveniles (5-10 months of age). In contrast to findings in rhesus macaques, hierarchical regression analyses showed that higher gestational testosterone levels, primarily in the second semester, were associated with decreased rough-and-tumble play in juveniles, and this relationship appears to be driven more so by males than females. We found no reliable associations between gestational androstenedione and juvenile play behavior. Our findings provide evidence to suggest that normative variation in levels of maternal androgen during gestation may influence developmental behavioral trajectories in marmosets in a way that contradicts previous findings in Old World primates.     

Prenatal alcohol exposure reduces the proportion of newly produced neurons and glia in the dentate gyrus of the hippocampus in female rats

Prenatal alcohol exposure (PAE) alters adult neurogenesis and the neurogenic response to stress in male rats. As the effects of stress on neurogenesis are sexually dimorphic, the present study investigated the effects of PAE on adult hippocampal neurogenesis under both nonstressed and stressed conditions in female rats. Pregnant females were assigned to one of three prenatal treatments: (1) alcohol (PAE)—liquid alcohol (ethanol) diet ad libitum (36% ethanol-derived calories); (2) pair-fed—isocaloric liquid diet, with maltose–dextrin substituted for ethanol, in the amount consumed by a PAE partner (g/kg body wt/day of gestation); and (3) control—lab chow ad libitum. Female offspring were assigned to either nonstressed (undisturbed) or stressed (repeated restraint stress for 9 days) conditions. On day 10, all rats were injected with bromodeoxyuridine (BrdU) and perfused either 24 hours (cell proliferation) or 3 weeks (cell survival) later. We found that PAE did not significantly alter cell proliferation or survival, whereas females from the pair-fed condition exhibited elevated levels of cell survival compared to control females. Importantly, however, the proportion of both new neurons and new glial cells in the hippocampal dentate gyrus was reduced in PAE compared to control females. Exposure to stress did not alter neurogenesis in any of the prenatal treatment groups. In summary, compared to females from the control condition, prenatal dietary restriction enhanced the survival of new neurons, whereas PAE altered the differentiation of newly produced cells in the adult dentate gyrus. Alterations in hippocampal neurogenesis following PAE may contribute to learning and memory deficits seen in individuals with fetal alcohol spectrum disorders.     

Gestational exposure to bisphenol A and cross-fostering affect behaviors in juvenile mice

Bisphenol-A (BPA) is a component of polycarbonate resins, and, lately, concern has been raised about its potential negative effects on human health. BPA is an estrogen analog and, in addition, it can act as a DNA hypomethylator. We examined the effects of gestational exposure to BPA on several behaviors in C57BL/6J mice. Because BPA affects maternal care, which, may have long-lasting effects on offspring behavior, we tested mice raised by either biological or fostered dams. Both diet and dam affected behavior in juvenile mice in a social novelty task and the elevated plus maze (EPM). In a social novelty task, the amount of time spent interacting with an adult male was affected by sex and gestational diet, but only in juveniles raised by a foster dam. Control females spent less time sniffing a novel adult than did control males or females exposed to BPA during gestation. In the EPM, juveniles reared by foster dams and exposed to BPA during gestation spent less time in the distal half of the open arm as compared with juveniles gestated on a control diet. Adult offspring raised by their biological dams showed the same response pattern; gestational BPA increased anxiety as compared with control diet. Our results show that prenatal BPA exposure affects social behavior and anxiety in the EPM. Moreover, some facet(s) of the infant–maternal interaction may modify these effects.     

Behavioral effects of prenatal folate deficiency in mice

BACKGROUND: Folate supplementation decreases the incidence of birth defects such as neural tube defects (NTDs). We and others have shown that gestational dietary folate deficiency that does not produce overt NTDs can alter fetal neural histology. Accordingly, murine offspring were examined for the possible functional consequences of prenatal folate deficiency. METHODS: CD-1 mice were fed a diet of chow containing 400, 600, or 1200 nmol of folic acid/kg of chow for eight weeks prior to breeding and until GD18, at which time all dams were placed on folate-replete chow. Behavioral tests of male and female offspring included righting reflex, negative geotaxis, forelimb hanging, motor coordination, open field activity, and elevated plus maze activity. RESULTS: Of greatest significance, the adult offspring that were prenatally folate-deficient exhibited more anxiety-related behavior in the elevated plus maze. Offspring of the 400 nmol of folic acid/kg of chow diet group exhibited significantly shorter durations in the open arms and longer durations in the closed arms. Further, these two behaviors were dose-related. There was also a trend for the prenatally folate-deficient adult mice to exhibit more thigmotaxis (wall-hugging) behavior in the open field, entering the central area less frequently than controls. There were few other differences in tested behaviors between folate-deficient and folate-replete mice. CONCLUSIONS: Prenatal folate deficiency that is repleted at birth can manifest later with increased anxiety 9-12 weeks after birth.     

Prenatal Ethanol Exposure Decreases GAP-43 Phosphorylation and Protein Kinase C Activity in the Hippocampus of Adult Rat Offspring

Abstract: Consumption of moderate quantities of ethanol during pregnancy produces deficits in long-term potentiation in the hippocampal formation of adult offspring. Protein kinase C (PKC)-mediated phosphorylation of the presynaptic protein GAP-43 is critical for the induction of long-term potentiation. We tested the hypothesis that this system is affected in fetal alcohol-exposed (FAE) rats by measuring GAP-43 phosphorylation and PKC activity in the hippocampus of adult offspring of rat dams that had consumed one of three diets throughout gestation: (a) a 5% ethanol liquid diet, which produced a maternal blood ethanol concentration of 83 mg/dl (FAE); (b) an isocalorically equivalent 0% ethanol diet (pair-fed); or (c) lab chow ad libitum. Western blot analysis using specific antibodies to PKC-phosphorylated GAP-43 revealed that FAE rats had an ∼50% reduction in the proportion of phosphorylated GAP-43. Similarly, we found that PKC-mediated incorporation of ³²P into GAP-43 was reduced by 85% in hippocampal slices from FAE rats compared with both control groups. FAE animals also showed a 50% reduction in total hippocampal PKC activity, whereas the levels of six major PKC isozymes did not change in any of the diet groups. These results suggest that GAP-43 phosphorylation deficits in rats prenatally exposed to moderate levels of ethanol are not due to alterations in the expression of either the enzyme or substrate protein, but rather to a defect in kinase activation.     

Alcohol deters the outgrowth of serotonergic neurons at midgestation

We have previously demonstrated that treatment of pregnant C57BL mice from gestation days 8 to 14 with alcohol with 20% ethanol-derived calories (EDC) reduced the number of serotonin (5-HT) neurons and retarded their migration in the fetal brains. In the present study, we obtained similar results with the use of 25% EDC and extended our previous findings by demonstrating that besides the alteration of the number of 5-HT neurons, prenatal alcohol exposure also affects their projecting fibers in their early development. Pregnant C57BL mice were divided into an alcohol-exposed (ALC) group given 25% EDC (4.49%, v/v), a pair-fed group to the ethanol-fed group (PF) and a chow-fed group (Chow). The PF and Chow groups served as controls. Our results showed that in the ALC group, when compared with the control groups, prenatal alcohol exposure with 25% EDC reduced the number of 5-HT-immunoreactive neurons in both the median and dorsal raphe, and the amount of 5-HT-immunoreactive fibers in the medial forebrain bundle (MFB). The diameter of the 5-HT-immunoreactive MFB was also reduced as a result of treatment. No significant differences of the above parameters were found between the PF and Chow groups. The previous and present work confirmed that alcohol reduces the normal formation and growth of 5-HT neurons in the midbrain. Furthermore, the projection of 5-HT fibers, in density as well as in distribution, is reduced in the major trajectory bundle. This may affect the amount of 5-HT fibers available to the forebrain. In light of the importance of the 5-HT system in brain development, alcohol may affect the growth of the forebrain through its effect on 5-HT signaling.     

Sedentary behavior during postnatal life is determined by the prenatal environment and exacerbated by postnatal hypercaloric nutrition

The discovery of a link between in utero experience and later metabolic and cardiovascular disease is one of the most important advances in epidemiology research of recent years. There is now increasing evidence that alterations in the fetal environment have long-term consequences on metabolic and endocrine pathophysiology in adult life. This process has been termed "fetal programming," and we have shown that undernutrition of the mother during gestation leads to obesity, hypertension, hyperphagia, hyperinsulinemia, and hyperleptinemia in offspring. Using this model of maternal undernutrition throughout pregnancy, we investigated whether prenatal influences may lead to alterations in postnatal locomotor behavior, independent of postnatal nutrition. Virgin Wistar rats were time mated and randomly assigned to receive food either ad libitum (ad libitum group) or at 30% of ad libitum intake (undernourished group). Offspring from UN mothers were significantly smaller at birth than AD offspring. At weaning, offspring were assigned to one of two diets [control or hypercaloric (30% fat)]. At ages of 35 days, 145 days, and 420 days, voluntary locomotor activity was assessed. At all ages studied, offspring from undernourished mothers were significantly less active than offspring born of normal birth weight for all parameters measured, independent of postnatal nutrition. Sedentary behavior in programmed offspring was exacerbated by postnatal hypercaloric nutrition. This work is the first to clearly separate prenatal from postnatal effects and shows that lifestyle choices themselves may have a prenatal origin. We have shown that predispositions to obesity, altered eating behavior, and sedentary activity are linked and occur independently of postnatal hypercaloric nutrition. Moreover, the prenatal influence may be permanent as offspring of undernourished mothers were still significantly less active compared with normal offspring at an advanced adult age, even in the presence of a healthy diet throughout postnatal life.     

Prenatal ethanol exposure reduces the effects of excitatory amino acids in the rat hippocampus

Chronic alcohol ingestion during pregnancy can lead to the Fetal Alcohol Syndrome (FAS), a disorder marked by learning disabilities. A rat model of FAS was used by introducing pregnant Sprague-Dawley rats to a liquid diet containing 35% ethanol-derived calories (E), while a second group was pair-fed an isocaloric liquid diet without ethanol (P). A third group of pregnant dams received ad libitum lab chow (C). At parturition, pups from the E and P groups were cross-fostered by C mothers and all groups received lab chow. During adulthood, male offspring were sacrificed and hippocampal and prefrontal cortical slices were prelabeled with [3H] inositol. Phosphoinositide (PI) hydrolysis was determined by measuring the accumulation of [3H]inositol phosphates in the presence of LiCl in response to activation of various excitatory amino acid (EAA) receptors. In hippocampal slices, ibotenate- and quisqualate-induced PI hydrolysis was reduced in E compared to P and C animals. Moreover, the inhibitory effect of N-methyl-D-aspartate (NMDA) on carbachol-induced PI hydrolysis, evident in P and C animals, was completely abolished in the hippocampus of E animals. In contrast, in the prefrontal cerebral cortex, this inhibitory effect of NMDA prevailed even in the E animals. The evidence suggest that prenatal ethanol exposure alters the activity of EAA receptors in the hippocampal generation of 2nd messengers.     

Prenatal and early postnatal dietary sodium restriction sensitizes the adult rat to amphetamines

Acute sodium deficiency sensitizes adult rats to psychomotor effects of amphetamine. This study determined whether prenatal and early life manipulation of dietary sodium sensitized adult offspring to psychomotor effects of amphetamine (1 or 3 mg/kg ip) in two strains of rats. Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) dams were fed chow containing low NaCl (0.12%; LN), normal NaCl (1%; NN), or high NaCl (4%; HN) throughout breeding, gestation, and lactation. Male offspring were maintained on the test diet for an additional 3 wk postweaning and then fed standard chow thereafter until testing began. Overall, blood pressure (BP), total fluid intake, salt preference, and adrenal gland weight were greater in SHR than in WKY. WKY LN offspring had greater water intake and adrenal gland weight than did WKY NN and HN offspring, whereas WKY HN offspring had increased BP, salt intake, and salt preference compared with other WKY offspring. SHR HN offspring also had increased BP compared with other SHR offspring; all other measures were similar for SHR offspring. The low-dose amphetamine increased locomotor and stereotypical behavior compared with baseline and saline injection in both WKY and SHR offspring. Dietary sodium history affected the rats' psychomotor response to the higher dose of amphetamine. Injections of 3 mg/kg amphetamine in both strains produced significantly more behavioral activity in the LN offspring than in NN and HN offspring. These results show that early life experience with low-sodium diets produce long-term changes in adult rats' behavioral responses to amphetamine.     

Preferential alcoholic embryopathy: effects of liquid diets.

Our initial report of a preferential expression of experimental alcoholic embryopathy affecting the male offspring contiguous in utero to male siblings of Long-Evans rats was based on gavage administration of alcohol to pregnant rats without regard to isocaloric, pair-fed exposure paradigms. In this study, pregnant Long-Evans rats were given 35% ethanol-derived calories (EDC) in one of two different liquid diets: 1) a liquid alcohol diet based on Sustacal, a flavored liquid food formulated for human nutritional standards; and 2) a high-protein liquid rodent diet devised by Lieber and DeCarli (L&D). The diets were administered from day 6 to 15 of gestation. Pregnant rats were pair-fed liquid diets containing 0% EDC, but isocalorically balanced to 35% EDC with either sucrose (Sustacal) or maltose-dextrin (L&D). A fifth group of pregnant rats was given access ad libitum to standard certified laboratory rodent diet and served as free-fed controls. On day 20 of gestation, all pregnant rats were euthanized and the products of conception examined by standard teratologic techniques. Pregnant animals fed Sustacal-based diets consistently consumed fewer calories per kilogram body weight per day from day 6 to 15 of gestation (i.e., they were significantly calorie-deprived during pregnancy) as compared with the standard laboratory-diet-fed controls or those consuming L&D diets. Body weights of rats consuming Sustacal diets (both 0 and 35% EDC) were significantly lower throughout gestation when compared with all other groups. Higher (> 150 mg/dl) blood alcohol levels were attained by rats consuming 35% EDC in Sustacal diet as compared with L&D (100 mg/dl) diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Does gestational temperature or prenatal sex ratio influence development of sexual dimorphism in a viviparous skink?

Prenatal sex ratio (through exposure to hormones from siblings in utero) can influence sexually dimorphic traits of many mammals; but research on viviparous reptiles has contrasting outcomes, which have yet to be resolved. The thermal environment experienced during gestation has a strong effect on the phenotype of reptiles, but whether this thermal effect overrides that of prenatal sex ratio has yet to be explored. We experimentally investigated whether the gestation temperature, or litter sex ratio, influences sexually dimorphic traits (head width and axilla-groin length) in a viviparous skink (Oligosoma maccanni). We found that gestation temperature had a significant influence on sexually dimorphic traits of neonates, and at 3 months of age still influenced head width. We found no evidence that traits in either sex were masculinized or feminized in response to litter sex ratio. The development of external sexual dimorphisms increased gradually (all thermal regimes pooled), with neonates showing no sexual dimorphism, 3-month-old juveniles showing some sexual dimorphism in head width, and adults having stronger, but incompletely separated, sexual dimorphism for both traits. We suggest that the overlap in sexually dimorphic traits of adult O. maccanni (and perhaps other reptiles) may be better explained by natural variation in temperatures experienced during embryonic development, rather than hormonal effects arising from litter sex ratio. The interaction of hormones and temperature during gestation and the effect of these factors on sexual dimorphism within reptiles deserve further exploration.     

Teratogenic and postnatal developmental studies of morphine in Sprague-Dawley rats

The teratogenic and postnatal developmental effects of morphine exposure during pregnancy were studied in Sprague-Dawley rats in three separate experiments using chronically implanted osmotic minipumps in order to avoid respiratory depression. In the first experiment, the teratogenic effects of three different morphine dosages were studied: a low dose (10 mg/kg/day), an intermediate dose (35 mg/kg/day), and a high dose (70 mg/kg/day). On day 5 of gestation, osmotic minipumps that deliver their contents at a constant rate for 15 days were implanted subcutaneously on the back of the rats. On day 20 of gestation, cesarean sections were performed, reproductive indices were determined, and fetuses were examined externally and then preserved for subsequent visceral and skeletal examinations. The pregnancy rate was significantly reduced at the intermediate and high doses to 57% and 6%, respectively (control, 83%). No teratogenic effects were observed at any dosage, but growth retardation was present in the intermediate-dose group. In the second experiment, postnatal survival of the offspring of dams treated with either normal saline, morphine (35 mg/kg/day), or the synthetic opioid, fentanyl (500 micrograms/kg/day) were studied. Offspring of morphine-treated dams had a significantly higher mortality rate, which peaked at 56% within 2 days. No effect was seen after fentanyl treatment. In the third experiment, pups of morphine-treated dams were cross-fostered by saline-treated dams; the postnatal mortality in offspring of morphine-treated dams remained high (62%). Our results indicate that doses of morphine up to 35 mg/kg/day delivered by osmotic minipumps are not teratogenic in rats but cause other adverse fetal effects that result in increased postnatal mortality.     

Evolution of viviparity in cold-climate lizards: testing the maternal manipulation hypothesis

We used a cold-climate viviparous lacertid lizard (Eremias prezwalskii) as a model system to test the maternal manipulation hypothesis. Twenty-four gravid females collected from a population in Inner Mongolia (northern China) were maintained in the laboratory for the whole gestation length, with 12 allowed to bask for 14-h daily and the other 12 for 10-h daily. Females selected lower body temperatures but did not thermoregulate more precisely when gravid. The mean gestation length was shorter in females provided with longer basking opportunity. Neonates in the two treatments differed in tail length and the number of ventral scales but not in other examined morphological traits, with offspring born in the 14-h treatment having longer tails but fewer ventral scales. Offspring were sexually dimorphic at birth, with females being smaller in tail length, head length and fore-limb length but having more ventral scales than males of the same size. Offspring born in the 14-h treatment were not only faster runners but also grew faster than did offspring born in the 10-h treatment. Our data validate the main predictions of the maternal manipulation hypothesis that females should shift selected body temperatures during gestation to provide optimal thermal conditions for developing embryos and that phenotypic traits determined by maternal thermoregulation should enhance offspring fitness. Our study is the first to demonstrate that the maternal manipulation hypothesis applies to cold-climate viviparous reptiles.