Differences in Production of Adrenal Steroid Hormones in Pubertal Rats Exposed to Low Doses of the Endocrine Disruptor DDT during Prenatal and Postnatal Development

Production of adrenal steroid hormones in pubertal male Wistar rats exposed to low doses of DDT during both prenatal and postnatal and only postnatal development has been investigated. Rats exposed to the disruptor prenatally and postnatally, and only postnatally were characterized by opposite changes in production of mineralocorticoids, glucocorticoids, male and female sex hormones. The study revealed that daily exposure to low doses of DDT enhanced conversion of progesterone to 17-OH-progesterone and did not exert selective antiandrogenic or proestrogenic action typical for the effect of toxic and subtoxic doses. In rats, exposed to DDT during their prenatal and postnatal development, impaired morphogenesis of the adrenal cortex and circulatory disorders in zona glomerulosa contributed to reduced aldosterone and sex steroid hormones production.     

Some Long-Lasting Neurochemical Efafects of Prenatal or Early Postnatal Exposure to Diazepam

Changes in the uptake of various neurotransmitters were measured in the frontal cortex and hippocampus of male and female rats that were exposed to diazepam through the placenta or through the mother's milk during the prenatal or early postnatal period of rapid brain development. Earlier studies from our laboratory showed that early diazepam exposure has long-lasting behavioral consequences. The present results show that prenatally diazepam-exposed rat pups show significant reduction in choline uptake in the frontal cortex at 10 days of age. At 60 days of age, both pre- and postnatally exposed males, but not females, show significant differences from controls in terms of choline uptake, whereas postnatally exposed females whose behavior was shown previously to be profoundly affected by the diazepam exposure showed significant increase in gamma-aminobutyric acid (GABA) uptake in the hippocampus and reduction of 5-hydroxytryptamine (5HT) uptake in the cortex at 60 days of age.     

Neurotoxicological Examination of the Piglet Brain after Prenatal and Postnatal Exposure to Trichlorfon

Piglets were given 10 repeated doses of the orga-nophosphorus compound trichlorfon during the postnatal period in order to examine the effect on the brain development (Experiment 1). Following prenatal exposure to trichlorfon, the ability of a presumptive hypoplastic cerebellum and cerebrum at birth, to regenerate postnatally was investigated (Experiment 2). Administration of repeated doses of trichlorfon postnatally was accompanied by only small changes in brain weights, morphology and transmitter enzyme activity (choline acetyltransferase, glutamate decarboxylase, aromatic amino acid decarboxylase) in 35 days old piglets. Animals exposed prenatally, and sacrificed at the age of 35 days, showed a significant increase in brain weights and enzyme activities. The animals did, however, not reach control values in cerebral weight, cerebellar weight or total enzyme activities. Morphological changes still showed regional loss of Purkinje cells in the cerebellum. The study clearly indicated that the pig brain was less vulnerable to trichlorfon in the postnatal period of development than when exposed to the compound prenatally.     

Perinatal olfactory learning in the domestic dog

The ability of individuals to learn about chemosensory stimuli in the prenatal, or immediate postnatal, period may be advantageous in acquiring information about "safe" foods after weaning. In this study, we examined the influence of perinatal exposure to aniseed via the mother's diet on a two-choice food test in the domestic dog. Pups were tested at 10 weeks of age following "prenatal" exposure to aniseed (the last 20 days of gestation), "postnatal" exposure to aniseed (the first 20 days after birth), "perinatal" exposure to aniseed (pre- and postnatal exposure combined), or no exposure to aniseed prenatally or postnatally (control). Perinatal exposure resulted in a significantly greater preference for the aniseed food than the other types of exposure. At 10 weeks, there was no evidence for the retention of any prenatal learning of the aniseed. It is suggested that exposure to a chemosensory stimulus across the perinatal period results in a greater effect than simply the sum of pre- and postnatal exposure due to priming of the chemosensory system via prenatal chemosensory experience. Such a system may confer survival advantages by promoting the acquisition of information about safe foods.     

Cross-generational effect of prenatal morphine exposure on neurobehavioral development of rat pups

Prenatal exposure to opiates can have devastating effects on the development of human fetuses and may induce long-term physical and neurobehavioral changes during postnatal maturation. The present study was aimed at identifying cross-generational effects of prenatal morphine exposure in Sprague-Dawley rats. Pregnant rats were injected subcutaneously with either saline or morphine (10 mg/kg) twice daily during gestational days 11-18. Litter size, percentage of males and females, anogenital distances (AGDs), righting reflex, and body weight were assessed in prenatally morphine-exposed pups (first generation) and their offspring (second generation). Both prenatally morphine-exposed pups and offspring of prenatally morphine-exposed dams exhibited an increased latency to right. Additionally, second generation pups were slower in righting than first generation pups. During the early postnatal period the second generation pups weighed less than the first generation regardless of drug exposure. The AGDs of second generation male pups were decreased relative to the first generation. Our data provide important novel information about the trans-generational effects of maternal opiate abuse that may be useful for understanding/evaluating the teratogenic effects of prenatal opiate exposure.     

Prenatal and early sucking influences on dietary preference in newborn, weaning, and young adult cats

Early experiences are of potential importance in shaping long-term behavior. This study examined the relative influence of prenatal and/or early postnatal experience of chemosensory stimuli on subsequent olfactory and dietary preferences of cats as newborns, at 9-10 weeks, and at 6 months. Cats were exposed to vanillin or 4-ethylguaiacol via their mother's diet either prenatally, postnatally, perinatally (prenatal and postnatal), or experienced no exposure to the stimuli (control). Newborns were given a two-choice olfactory test between the familiar "odor" and no odor; 9-10 week olds were tested for their preference between two food treats, one flavored with the familiar stimulus and the other unflavored; at 6 months, cats were given a choice of two bowls of food, one flavored with the familiar stimulus and the other unflavored. At all ages, cats preferred the familiar, and avoided the unfamiliar, stimulus. Perinatal exposure exerted the strongest influence on preference. Prenatal exposure influenced preference at all ages and postnatal exposure exerted a stronger effect as the cat aged. We conclude that long-term chemosensory and dietary preferences of cats are influenced by prenatal and early (nursing) postnatal experience, supporting a natural and biologically relevant mechanism for the safe transmission of diet from mother to young.     

产前轻微应激易化由围产期注射引起的行为改变并弱化奥氮平的作用

产前母体处于应激状态下,可以削弱子代的神经系统对外界不良刺激影响的抵抗能力．但产前应激状态是否可以影响抗精神疾病药物对动物行为的增益作用,目前还没有明确的结论．此外,在动物实验中,动物需要经常接受注射操作,注射操作本身是否会影响动物行为,尚未有相关研究．在本实验中,探索了产前轻微应激状态、围产期注射操作和抗精神疾病药物对动物行为可能的交互影响．母鼠在经历产前轻微应激状态后生产子代,雄性仔鼠在围产期(日龄第7, 9, 11天)不接受注射或接受盐水或奥氮平注射(2 mg/kg,腹腔注射)．在其亚成年期(日龄第35天)和成年期(日龄第60天),观察其社交和嗅觉辨识行为,分析了总探索时间和对新旧刺激的偏好程度两个参数．我们发现,围产期重复注射操作可以改变产前应激组大鼠在社交和嗅觉辨识实验中的偏好程度,对无应激组大鼠没有影响．奥氮平注射可以增长无应激组大鼠在社交活动中的总探索时间,对应激组大鼠没有影响．研究表明,产前轻微应激状态可以易化诸如围产期注射操作等不良环境刺激导致的行为异常,并减弱抗精神疾病药物的对神经系统的影响．     

Studies concerning the effects of low level prenatal X-irradiation on postnatal growth and adult behaviour in the Wistar rat

Fifty-nine pregnant Wistar strain rats were sham irradiated or subjected to a 0.1 or 0.2 Gy exposure of X-radiation on the 9th or 17th day of gestation. Twenty-seven of the females were killed at term for teratologic analysis. The remaining mothers raised their young. At 60 days of age the 252 offsprings were randomly assigned three of six tests: open field, swimming, hanging, activity wheel, water T-maze, or conditioned avoidance response. Male offspring exposed at the 0.2 Gy level exhibited retarded growth only during the first few weeks of postnatal life. Female offspring exposed on the 17th day to 0.2 Gy X-radiation were growth retarded throughout the test period. Postnatal growth rates, however, were not significantly different between the irradiated and control groups. There were no significant alterations in adult behaviour due to prenatal X-irradiation. There were sex differences in activity wheel and forelimb hanging performance, unrelated to radiation exposure. These results indicate that prenatal low level X-irradiation on the 9th or 17th day of gestation does not result in significant alterations in adult behavioural performance in the rat, but prenatal growth retardation persists postnatally. Growth may be a more sensitive indicator of the effects of prenatal exposure to X-radiation than postnatal behaviour.     

Influence of pre- and postnatal exposure of rats to 2.45-GHz microwave radiation on neurobehavioral function

Rats exposed to microwaves prenatally (2,450 MHz, 10 mW/cm2, 3 h/day, days 5-20 of gestation) or perinatally (same as above plus days 2-20 postnatally) were examined by a neurobehavioral test battery on postnatal days 30 and 100. Body mass, locomotor activity, startle to acoustic and air-puff stimuli, fore- and hindlimb grip strength, negative geotaxis, reaction to thermal stimulation, and swimming endurance were assessed. The prenatally and the perinatally exposed rats (male and female) weighted more than sham-exposed rats at 30, but not at 100, days of age. In addition, the perinatally exposed animals had less swimming endurance at 30, but not at 100, days of age relative to sham-exposed rats. For the other measures, only the air-puff startle response was altered and was limited to the prenatally exposed female pups; ie, at postnatal day 30, the startle response was increased in magnitude, and at postnatal day 100, the response was decreased. No other reliable effects were observed. In a second experiment, rats treated as described above were examined for alterations in body mass, locomotor activity, reaction to air-puff stimuli, reaction to thermal stimulation, and swimming endurance at postnatal days 30-36. Again, perinatally exposed rats were larger in body mass and had less swimming endurance compared with sham-exposed rats. The latency to the air-puff startle response was longer in female pups exposed prenatally. These data indicate that altered endurance and gross motor activity result from perinatal exposure to microwave irradiation.     

Influences of pre- and postnatal testosterone treatment on defeminization of sexual receptivity in pigs

Sexual receptivity was evaluated in female and male pigs that had experienced varying periods of exposure to testosterone pre- and postnatally. For prenatal exposure, pregnant sows were treated with testosterone propionate (TP) from Day 29-35 or Day 39-45 of gestation at a dosage that caused virilization of the external genitalia of their female offspring. Eighty-three percent of the females that received TP prenatally had regular estrous cycles, but reached puberty later than control females. Only 26% of the females that received TP both pre- and postnatally (4-6 mo of age) were observed in estrus by 10 mo of age. After ovariectomy and acute treatment with estradiol benzoate (EB), the proportion of females that showed the immobilization response (receptivity) was similar for all groups of females independent of pre- or postnatal TP treatment. Females treated prenatally from Day 39-45 showed the immobilization response for fewer days after treatment with a high dosage of EB than did controls. On the basis of these observations, we conclude that receptivity in female pigs is not affected greatly by testosterone treatment at the stages of development that were investigated. Males castrated at birth and treated with a single injection of EB after 9.5 mo showed the immobilization response. In contrast, few males castrated at 8 mo or castrated at birth and treated with TP from 3 to 6 mo showed the immobilization response after EB treatment. These observations provide direct evidence for a postnatal component of testosterone-dependent defeminization of receptivity in male pigs.     

Perinatal exposure to 19-Nor-17α-ethynyltestosterone (norethindrone) influences morphology and aggressive behavior of female mice

Pregnant mice were injected with 50 or 100 μg of the synthetic progestin 19-nor-17α-ethynyltestosterone (NET) on Days 14 through 17 of gestation. Others received only the vehicle or were left undisturbed. Exposure to NET during the prenatal period increased anogenital distance of the female offspring as measured on Day 60 but did not influence the duration of adult testosterone (T) exposure required to activate male-like intraspecific fighting behavior. In a second experiment, female mice were exposed to NET either prenatally, postnatally (Day 1), or pre- and postnatally. Exposure during both pre- and postnatal periods increased anogenital distance but only the exposure during the postnatal period enhanced later behavioral sensitivity to the aggression-activating property of T. Thus, NET is similar to testosterone in its ability to virilize morphology and behavior, although, at the dosages administered, behavioral alternation only occurred as a result of treatment during the neonatal period.     

Alteration in the Postnatal Ontogeny of Cerebellar Norepinephrine Content Following Chronic Prenatal Carbon Monoxide

The postnatal ontogeny of norepinephrine content in the cortex and cerebellum was determined in rats exposed prenatally to a chronic low level of carbon monoxide (150 parts per million). In the cerebellum, norepinephrine concentration and total norepinephrine content among carbon monoxide-exposed rats were consistently elevated over that of control rats from the second through the sixth postnatal weeks. In the cortex, norepinephrine concentration and total norepinephrine content among carbon monoxide-exposed rats did not differ from that of control rats over the same period. These results identify the cerebellum as a region whose postnatal development is altered by prenatal exposure to low levels of carbon monoxide-induced hypoxia.     

Species Differences in Dopamine Transporters: Postmortem Changes and Glycosylation Differences

Abstract: The apparent molecular masses of photoaffinity-labeled dopamine transporters (DATs) from rat, human, dog, and primate kidney COS cells expressing the rat DAT1 cDNA differ. Sequences predicted from cDNA cloning reveal only one amino acid difference between the length of the rat and human DAT but one less site for potential N-linked glycosylation in the human DAT. Possible posttranslational and postmortem bases for species differences in DAT molecular mass were explored. Rat DAT proteins from striata subjected to ∼5 h of postmortem delay modeled after the human postmortem delay process revealed small but consistent losses in apparent molecular mass and in cocaine analogue binding; the DAT molecular mass displayed no further losses for up to 30 h of model postmortem treatment. Degradative postmortem changes could thus contribute to molecular mass differences between rat and human DATs. Neuraminidase treatment reduced the apparent molecular mass of native rat DAT but not that of the rat DAT expressed in COS cells, suggesting that the sugars added to the DAT expressed in COS cells were different than those added to the rat brain striatal transporter. These differences could account for the somewhat higher K_m values for expressed DAT cDNA in COS cells when compared with the wild-type striatal transporter. These results are in accord with the differences in number of predicted N-linked glycosylation sites between rat and human DATs and with cell-type specificity in transporter posttranslational processing.     

Prenatal Amphetamine-Induced Dopaminergic Alteration in a Gender- and Estrogen-Dependent Manner

Prenatal exposure to amphetamine induces changes in dopamine receptors in mesolimbic areas and alters locomotor response to amphetamine during adulthood. Sex differences have been reported in amphetamine-induced brain activity and stress sensitivity. We evaluated the effects of prenatal amphetamine exposure on locomotor activity, dopamine receptors and tyrosine hydroxylase mRNA expression in nucleus accumbens and caudate-putamen in response to amphetamine challenge in adult female and male rats. The role of estrogen in the response to restraint stress was analyzed in ovariectomized, prenatally amphetamine-exposed rats. Pregnant rats were treated with d-amphetamine during days 15–21 of gestation. Nucleus accumbens and caudate-putamen were processed for mRNA determination by real-time PCR. In nucleus accumbens, higher mRNA dopamine (D3) receptor expression was found in basal and d-amphetamine-challenge conditions in female than male, and prenatal amphetamine increased the difference. No sex differences were observed in caudate-putamen. Basal saline-treated females showed higher locomotor activity than males. Amphetamine challenge in prenatally amphetamine-exposed rats increased locomotor activity in males and reduced it in females. In nucleus accumbens, estrogen diminished mRNA D1, D2 and D3 receptor expression in basal, and D1 and D3 in ovariectomized stressed rats. Estrogen prevented the increase in tyrosine hydroxylase expression induced by stress in ovariectomized prenatally exposed rats. In conclusion, estrogen modulates mRNA levels of D1, D2 and D3 receptors and tyrosine hydroxylase expression in nucleus accumbens; prenatal amphetamine-exposure effects on D3 receptors and behavioral responses were gender dependent.

     

Single early prenatal lipopolysaccharide exposure impairs striatal monoamines and maternal care in female rats

AimsEnvironmental information received by a mother can induce a phenotype change in her offspring, commonly known as a maternal effect (trans-generational effect). The present work verified the effects of lipopolysaccharide (LPS), which mimics bacterial infection, on maternal care and on the activity of related brain areas in F1 offspring, i.e., female rats that were prenatally exposed to LPS.Main methodsPregnant rats received 100 μg/kg of LPS intraperitoneally on gestational day (GD) 9.5. Female offspring of the F1 generation were mated to naïve males and were evaluated during their lactation period for open field, maternal and aggressive behaviors. Striatal and hypothalamic dopamine and serotonin levels and turnover were also evaluated. Furthermore, astrocyte protein expression in the nucleus accumbens (NA) was analyzed in F1 females to assess LPS-induced neuroinflammation.Key findingsPrenatal LPS did not change open field behavior but impaired both maternal and maternal aggressive behaviors in the F1 generation. LPS exposure also reduced both striatal levels of dopamine and serotonin and its metabolites, but induced no changes in NA astrocyte expression.SignificanceWe suggested that the observed impairments in the F1 females were a consequence of a motivational change induced by prenatal LPS, as (1) no changes in motor activity were observed, (2) prenatal LPS-exposure was reported by our group to induce motivational impairments in males, and (3) the existence of a strong connection between striatal dopaminergic activity and motivation-oriented activities. The present findings strongly indicate a maternal effect for prenatal LPS, at least for the F1 generation.     

Long term effects of prenatal cocaine exposure on bone in rats

Prenatal exposure to cocaine has been shown to produce a variety of effects on skeletal development and mineralization in humans, mice, and rats. The effects of cocaine on bone cell function and mineral metabolism pre- and postnatally are poorly understood. The present study examined the long term effects of prenatal cocaine exposure on femoral growth and mineralization in male rats. Pregnant rats were given 80 or 100 mg cocaine hydrochloride/kg during days 7-20 of gestation. At birth, body weights of pups born to these females were significantly decreased compared to normal and pair-fed controls. At the termination of the study (32 weeks), body weights of offspring from C100-treated females were still lower than normal. Long term effects of prenatal exposure to cocaine on femoral growth were most pronounced in offspring of C80-treated females. Femur dry weight, ash weight, organic matrix weight and density were significantly reduced in these animals compared to normal or pair-fed controls. The apparent osteopenic effects of prenatal exposure to cocaine suggests some long term postnatal impact on bone cell or mineral metabolism. Previous studies of cocaine use during pregnancy in humans and animals have focused primarily on physical and behavioral defects in offspring. The present findings indicate that prenatal exposure to cocaine may also have long term consequences to the skeleton.     

Rapid substrate-induced down-regulation in function and surface localization of dopamine transporters: rat dorsal striatum versus nucleus accumbens

The dopamine transporter (DAT) substrates dopamine, d-amphetamine (AMPH), and methamphetamine are known to rapidly and transiently reduce DAT activity and/or surface expression in dorsal striatum and heterologous expression systems. We sought to determine if similar substrate-induced regulation of DATs occurs in rat nucleus accumbens. In dorsal striatum synaptosomes, brief (15-min) in vitro substrate pre-exposure markedly decreased maximal [³H]dopamine uptake velocity whereas identical substrate pre-exposure in nucleus accumbens synaptosomes produced a smaller, non-significant reduction. However, 45 min after systemic AMPH administration, maximal ex vivo [³H]dopamine uptake velocity was significantly reduced in both brain regions. Protein kinase C inhibition blocked AMPH's down-regulation of DAT activity. DAT synaptosomal surface expression was not modified following either the brief in vitro or in vivo AMPH pre-exposure but was reduced after a longer (1-h) in vitro pre-exposure in both brain regions. Together, our findings suggest that relatively brief substrate exposure results in greater down-regulation of DAT activity in dorsal striatum than in nucleus accumbens. Moreover, exposure to AMPH appears to regulate striatal DATs in a biphasic manner, with an initial protein kinase C-dependent decrease in DAT-mediated uptake velocity and then, with longer exposure, a reduction in DAT surface expression.     

Disturbed testicular descent in the rat after prenatal exposure to the antiandrogen flutamide.

Exposure of rats in utero to the anti-androgen flutamide resulted in feminization of the external genitalia that was noticeable at birth. This exposure also resulted in a high degree of cryptorchidism during adulthood. In most affected animals, testes were lying in 'ovary position' close to the caudal pole of the ipsilateral kidney. Cryptorchidism occurred despite normal prenatal development of the gubernacular cones and the transformation of these structures, postnatally, into muscular cremaster sacs. Inter- and intralitter variation in the response to prenatal exposure to flutamide was observed as well as intra-individual variation. Cryptorchidism frequently occurred unilaterally with right side cryptorchidism predominating. Cryptorchidism occurred in association with marked suppression of the growth of the ipsilateral epididymis and deferent duct. The possibility is considered that the poor development or absence of these structures contributes to cryptorchidism. Intra-individual variation supports the concept of the local nature of the influence of testis hormones in stabilization and further differentiation of the ipsilateral Wolffian duct derivatives. Cryptorchidism was enhanced when rats were treated postnatally with testosterone or oestradiol. The effect of testosterone was unexpected in view of the generally held hypothesis that androgens enhance testis descent. The effect of oestradiol was as expected: other animal models have been described in which induction of cryptorchidism by oestradiol occurs. Additional treatment with oestradiol caused further suppression of growth of the epididymis and deferent duct. The response to prenatal exposure to flutamide was not altered by further injections of flutamide postnatally. Such injections were without effect in males not exposed to flutamide prenatally except for minor, but statistically significant, testicular enlargement during adulthood. A model is thus presented that describes cryptorchidism as an endogenous developmental disorder.     

Prenatal testosterone exposure leads to hypertension that is gonadal hormone-dependent in adult rat male and female offspring

Prenatal testosterone exposure impacts postnatal reproductive and endocrine function, leading to alterations in sex steroid levels. Because gonadal steroids are key regulators of cardiovascular function, it is possible that alteration in sex steroid hormones may contribute to development of hypertension in prenatally testosterone-exposed adults. The objectives of this study were to evaluate whether prenatal testosterone exposure leads to development of hypertension in adult males and females and to assess the influence of gonadal hormones on arterial pressure in these animals. Offspring of pregnant rats treated with testosterone propionate or its vehicle (controls) were examined. Subsets of male and female offspring were gonadectomized at 7 wk of age, and some offspring from age 7 to 24 wk received hormone replacement, while others did not. Testosterone exposure during prenatal life significantly increased arterial pressure in both male and female adult offspring; however, the effect was greater in males. Prenatal androgen-exposed males and females had more circulating testosterone during adult life, with no change in estradiol levels. Gonadectomy prevented hyperandrogenism and also reversed hypertension in these rats. Testosterone replacement in orchiectomized males restored hypertension, while estradiol replacement in ovariectomized females was without effect. Steroidal changes were associated with defective expression of gonadal steroidogenic genes, with Star, Sf1, and Hsd17b1 upregulation in testes. In ovaries, Star and Cyp11a1 genes were upregulated, while Cyp19 was downregulated. This study showed that prenatal testosterone exposure led to development of gonad-dependent hypertension during adult life. Defective steroidogenesis may contribute in part to the observed steroidal changes.