Are the effects of gestational stress on motor development and cerebellar cholinesterase activity mediated prenatally?

Perinatal glucocorticoid treatment produces molecular, functional, and morphological changes in the anterior pituitary gland of the adult male rat

Stress or glucocorticoid (GC) treatment in perinatal life can induce long-term changes in the sensitivity of the hypothalamo-pituitary-adrenocortical axis to the feedback actions of GCs and, hence, in GC secretion. These changes have been ascribed largely to changes in the sensitivity of the limbic system, and possibly the hypothalamus, to GCs. Surprisingly, the possibility that early life stress/GC treatment may also exert irreversible effects at the pituitary level has scarcely been addressed. Accordingly, we have examined the effects of pre- and neonatal dexamethasone treatment on the adult male pituitary gland, focusing on the following: 1) the integrity of the acute annexin 1 (ANXA1)-dependent inhibitory actions of GCs on ACTH secretion, a process requiring ANXA1 release from folliculostellate (FS) cells; and 2) the morphology of FS cells and corticotrophs. Dexamethasone was given to pregnant (d 16-19) or lactating (d 1-7 postpartum) rats via the drinking water (1 microg/ml); controls received normal drinking water. Pituitary tissue from the offspring was examined ex vivo at d 90. Both treatment regimens reduced ANXA1 expression, as assessed by Western blotting and quantitative immunogold labeling. In particular, the amount of ANXA1 located on the outer surface of the FS cells was reduced. By contrast, IL-6 expression was increased, particularly by the prenatal treatment. Pituitary tissue from untreated control rats responded to dexamethasone with an increase in cell surface ANXA1 and a reduction in forskolin-induced ACTH release. In contrast, pituitary tissue from rats treated prenatally or neonatally with dexamethasone was unresponsive to the steroid, although, like control tissue, it responded readily to ANXA1, which readily inhibited forskolin-driven ACTH release. Prenatal dexamethasone treatment reduced the size but not the number of FS cells. It also caused a marked reduction in corticotroph number and impaired granule margination without affecting other aspects of corticotroph morphology. Similar but less marked effects on pituitary cell morphology and number were evident in tissue from neonatally treated rats. Our study shows that, when administered by a noninvasive process, perinatal GC treatment exerts profound effects on the adult pituitary gland, impairing the ANXA1-dependent GC regulation of ACTH release and altering the cell profile and morphology.

Prenatal stress reduces interneuronal connectivity in the rat cerebellar granular layer

The development and functioning of the central nervous system have been shown to be affected by maternal stress. To investigate the effects of prenatal stress on the cerebellar interneuronal connectivity, rat embryos are exposed to stress on their embryonic day (E) 7 and 14, by keeping the dam in close-fitting wire mesh cylinders, for 6 h. After completion of the cerebellar development at postnatal day (P) 30, stereological procedures were used at the light and electron microscopic level to analyze growth parameters of the granule cells and synapse-to-neuron ratios. Neither the volume fraction (V(V)) of the granular layer to whole cortex, nor the numerical density of granule cells (N(Vg)) per unit volume of granular layer was affected by exposure to stress. However, the mean granule cell nuclear diameter was significantly decreased in stressed animals. Within the neuropil region, the number and mean diameter of synaptic disc profiles were used to estimate the numerical density of synapses (N(Vs)). Synapse-to-neuron ratio was obtained by dividing N(Vs) with N(Vg), and found significantly lower in the stressed group than the control group. In addition, synaptophysin immunoreactivity showed a significant decrease (41%) in the granular layer of the cerebellum. Collectively, these results demonstrate that intrauterine stress alters the morphology of granule cells and causes a profound and fairly long-lasting deficit in their interneuronal connectivity.

The role of prenatal stress in the etiology of developmental behavioural disorders

Substantial evidence from preclinical laboratory studies indicates that prenatal stress (PS) affects the hormonal and behavioural development of offspring. In the following review, the effects of PS in rodents and non-human primates on hypothalamic-pituitary-adrenal (HPA) reactivity to stress, morphological changes in the brain, motor behaviour and learning are surveyed. PS has been found to alter baseline and stress-induced responsivity of the HPA axis and levels and distribution of regulatory neurotransmitters, such as norepinepherine, dopamine, serotonin and acetylcholine and to modify key limbic structures. In rodents and non-human primates, PS affected learning, anxiety and social behaviour. The relevance of these findings to humans is discussed with respect to (a) the effect of administration of exogenous corticosteroids in pregnancy and (b) maternal state and trait anxiety during gestation and its relation to foetal autonomic regulation as putative predisposing factors in the pathogenesis of behavioural developmental delays in children.

Effects of maternal stress on development and behaviour in rat offspring

Retrospective studies suggest that gestational stress in humans can delay the attainment of developmental milestones, increase the incidence of allergic reactions and respiratory infections and cause behavioural abnormalities in the children. Our studies and others have shown that prenatal stress in rats can mimic several of these developmental and behavioural alterations. These include a suppression of immune function, but also enhanced sensitivity to allergens. Prenatally-stressed rats, like children, show a reduced propensity for social interaction and increased anxiety in intimidating or novel situations. They have physiological and behavioural alterations consistent with depressive symptoms, including a phase-shift in their circadian rhythm for corticosterone, sleep abnormalities, and greater acquisition of learned helplessness under appropriate conditions. Prenatally-stressed male rats also show demasculinisation and feminisation of their sexual behaviour. The developmental and behavioural abnormalities in prenatally-stressed offspring may be mediated by alterations in the activity of endogenous opioids or neurosteroids, since several of them can be corrected by maternal administration of an opioid antagonist or by drugs like diazepam and allopregnanolone that modulate GABA transmission.

Developmental effects of intermittent prenatal exposure to 1,1,1-trichloroethane in the rat

The effects of daily three 1-h exposures to 7000 ppm 1,1,1-trichloroethane (TCE) on physical and behavioral development were examined in Sprague-Dawley rats exposed during the last week of gestation. A sham group was exposed to filtered air. Offspring of both groups were fostered to untreated dams. No significant group differences were detected in total maternal weight gain or food and water consumption, but differences were observed in initial litter characteristics, including a longer gestation period in the TCE group, a smaller number of litters delivered in the TCE group, and fewer live pups per litter in the TCE group. At birth, the total litter weight was less in the TCE group, but there was no significant difference in average pup weight. Pups prenatally exposed to TCE did not differ from shams in day of eye opening, pinnae detachment, or incisor eruption. The TCE group weighed less the first 2 weeks of life, was impaired in its ability to perform the inverted screen, negative geotaxis, and vertical screen tests, and had less forelimb grip strength. Locomotor activity was reduced in the TCE group, and the ratio of brain to body weight was reduced in TCE-exposed offspring. These data provide evidence for neurobehavioral teratogenicity of intermittent prenatal exposure to high concentrations of TCE in rats.

Effect of gestational stress on maternal behavior in response to cage transfer and handling of pups in two strains of rat

The influence of gestational stress was determined on the mother's behavior in two rat strains after a disturbance in her routine. Daily 10 min observations were made for 9 days postpartum in Sprague-Dawley (S-D) and Sabra (SB) rats after transfer of the maternal cage to another room or transient pup removal. In response to cage transfer, SB spent much more time than S-D rats in nursing, licking and sitting on their pups, but less time in individual activities. The direction of effect of gestational stress depended on the strain and particular behavior. The duration of nursing was increased in S-D but decreased in SB rats, while that of pup-licking was increased in SB and unchanged or decreased in S-D. Pup-removal reduced the total amount of pup-directed behavior in control and stressed mothers of both strains and eliminated any differences resulting from gestational stress seen in response to cage transfer. It is concluded that the degree and direction of effect of gestational stress on the partition of time by a nursing mother between pup-directed and other behaviors during the early postnatal period is strongly influenced by the strain of rat and the conditions under which it is assessed.

Prenatal stress effects are partially ameliorated by prenatal administration of the neurosteroid allopregnanolone

This study examined the effects of exposure to prenatal stress on young and adult rats, and whether the concomitant administration of an anxiolytic neurosteroid, allopregnanolone (3-alpha-hydroxy-5 alpha-pregnan-20-one), could ameliorate some of the behavioral dysfunctions associated with prenatal stress. Pregnant dams were assigned to one of five treatment groups on gestational day 14. These groups were exposed to either 1) restraint for 45 min three times daily; 2) a vehicle injection twice daily; 3) 5 mg/kg allopregnanolone twice daily; 4) restraint with allopregnanolone injections; or 5) nonhandled controls. Assays for plasma allopregnanolone concentrations indicated that exogenous allopregnanolone injections significantly raised circulating levels to a comparable degree in gestational day 20 dams and their fetuses. At 7 days of age, however, subjects prenatally exposed to allopregnanolone either alone or with restraint now had lower circulating levels compared to the other groups, suggesting some negative compensatory change. Behavioral results suggested that the effects of prenatal stress on affective behaviors (ultrasonic vocalizations emitted after a brief maternal separation at 7 days of age, and plus-maze behavior at 70 days of age) could be reversed by coadministration of allopregnanolone. When locomotor activity was assessed at 16 and 60 days of age, no comparable reversal effect was observed. In fact, the allopregnanolone groups had results similar to those of the restraint alone group. Thus, for some neuronal systems, allopregnanolone may exert either a direct teratogenic effect or an indirect effect due to neurosteroid-induced behavioral changes in the pregnant dam.

Does prenatal stress impair coping and regulation of hypothalamic-pituitary-adrenal axis?

Prenatally stressed (PS) human infants and experimental animals show attentional deficits, hyperanxiety and disturbed social behavior. Impaired coping in stressful situations in adult PS monkeys and rodents is associated with dysregulation of the HPA axis, characterized by decreased feedback inhibition of corticotropin-releasing hormone (CRH) and prolonged elevation of plasma glucocorticoids in response to stress. PS rats have higher levels of CRH in the amygdala, fewer hippocampal glucocorticoid receptors and less endogenous opioid and GABA/BDZ (benzodiazepine) inhibitory activity. The mechanisms by which maternal stress induce these long-lasting changes in the developing fetal neuroaxis remain to be elucidated. It is suggested that impaired coping in stressful situations and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, result from the action of maternal hormones released during stress on the developing fetus. The similarities in coping behavior and dysregulation of the HPA axis in PS animals to those in humans with depression, suggest that gestational stress, at a critical time during fetal development, may increase the propensity to develop this condition.

Developmental consequences of intermittent and continuous prenatal exposure to 1,1,1-trichloroethane in mice

The effects of 1,1,1-trichloroethane (TCE) on physical and behavioral development were examined in CD-1 mice prenatally exposed under two regimens. In the first study, pregnant mice were exposed to either 2,000 ppm TCE or filtered air for 17 hrs. during gestational days (GD) 12-17. A third group remained untreated. The results revealed no differences on pregnancy outcome. TCE-exposed pups gained less weight, exhibited delays in developmental landmarks and acquisition of the righting reflex, had poorer performance on tests of motor coordination and exhibited delays in negative geotaxis relative to sham or untreated pups. A second experiment was designed to more closely parallel the intermittent, acute, high-concentration pattern of solvent abuse. Pregnant mice were exposed for 60 min. to 8,000 ppm TCE or sham placement in exposure chambers three times/day during GD's 12-17. The results were very similar to what were obtained in the more continuous exposure study. TCE-exposed pups gained less weight, had delays in developmental landmarks and acquisition of the righting reflex and exhibited weaker grip strength, poorer negative geotaxis and less rooting intensity in comparison to sham pups. These data provide evidence for the behavioral and developmental teratogenicity of prenatal TCE exposure late in gestation.

Influence of prenatal maternal stress on the immunocompetence of the offspring

To evaluate the effects of prenatal maternal stress on the development of humoral immunocompetence in the offspring and on their hormonal and immunologic responses to postnatal stress, gravid Sprague-Dawley rats were exposed daily on gestational days 15-21 to prenatal environmental stress [(PES) 15 unsignaled, inescapable electric foot-shocks (0.05 mA for 0.5 s)] or prenatal psychological stress [(PPS) pregnant rats were placed in the nonelectrified section of the apparatus and allowed to see, hear, and smell a nonpregnant partner being environmentally stressed]. Pregnant controls (PC) were placed in the apparatus for 30 min. Serum corticosterone (CCS) and immunoglobulin G (IgG) levels were measured in the offspring every 7 days from birth to postnatal day (PND) 28. On PND 29-33, offspring were environmentally stressed; hormonal and immune status were determined on PND 34. Levels of IgG were reduced in PES and PPS offspring on PND 0 and in PES offspring on PND 7 and 28. These changes were unrelated to differences in CCS and did not reflect altered maternal-pup interactions or nutritional factors. Postnatal stress was immunosuppressive in PC pups but did not alter immune parameters in PPS offspring. In PES females, postnatal stress was also immunosuppressive. However, in PES males with already reduced IgG levels postnatal stress enhanced immune function. These data provide the first experimental evidence that prenatal maternal stress can alter immune parameters in the rat offspring.

Neonatal handling reverses behavioral abnormalities induced in rats by prenatal stress

The aim of this study was to see whether neonatal handling can reverse the behavioral deficits induced in rats by unpredictable prenatal stress. Rats (24) were exposed to random noise and light stress (RS) on a random basis throughout pregnancy. Half the litters of RS and control (C) dams were subjected to neonatal handling (NH), 3' daily for 21 days. Behavioral measures, open field in both sexes and plus maze test in females only were conducted at 1.5-2 months, and spatial lateralization by amphetamine-induced rotation, in females at 3 months. RS caused significant increases in emotionality and timidity (higher incidence of defecation and less time in open arms of plus maze), and a change in directional bias towards the left. NH completely reversed all these behavioral abnormalities in RS rats but had little effect in C. It is concluded that NH can influence postnatal development of brain organisation in the opposite direction to that induced by prenatal stress.

Alterations in behavioral and striatal dopamine asymmetries induced by prenatal stress

We investigated the effects of maternal noise and light stress, randomly applied throughout pregnancy, on the development of behavioral and neurochemical asymmetries in the rat offspring. This form of maternal stress resulted in a rightward positioning of the tail of both sexes soon after birth as opposed to the leftward bias in controls. At adulthood, prenatally stressed offspring showed a change in directional bias compared to controls with a preponderance of left turns after amphetamine. In the males, this was expressed as a reduction in directional preference, while in females a reversal occurred of their dominant turning direction from right (controls) to left. We also observed a reduction in dopamine turnover rates in the left corpora striata of stressed offspring of both sexes. Again, in the females, this change was particularly marked and resulted in a reversal towards the right hemisphere. The findings from this study are consistent with the possibility that the alterations in cerebral asymmetries induced by prenatal stress may underly the decrease in the ability of the offspring to cope with anxiety provoking situations.

Reductions in maternal food and water intake account for prenatal stress effects on neurobehavioral development in B6D2F2 mice

This study evaluated the role of stress-induced reductions in food intake in pregnant B6D2F1 mice in the production of developmental abnormalities in the offspring. One group of dams underwent one hour of physical restraint stress twice daily from days 12 to 17 of gestation. A second group was not restrained but, during this period, each dam was pair-fed to a weight-matched partner in the stressed group. A third group was left undisturbed and allowed unlimited access to lab chow and water. The restraint stress procedure reduced the average daily food and water intake in the dams, resulting in lower maternal weights, with the unstressed pair-fed group being affected more severely than the stressed group. The offspring of both the stressed and pair-fed dams were lighter than the offspring of the dams fed ad lib on day 20 postconception, and exhibited lower brain weights on day 32 postconception. Neurobehavioral development, as assessed on a battery of sensorimotor tests on day 32 postconception, was retarded in the prenatally stressed pups in comparison to the ad lib pups, while the pair-fed pups did not differ from either group. There were no differences among any of the groups on day 50 body or brain weight, body or tail length, anogenital distance, or locomotion, rearing and defecation in the open field.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal stress on vulnerability to stress in prepubertal and adult rats

This study investigated the hypotheses that unpredictable prenatal stress has effects on the offspring, similar to those induced by perinatal administration of glucocorticoids and increases the vulnerability to stressful situations at adulthood. Rats were exposed to random noise and light stress throughout pregnancy. Offspring were tested for the development of spontaneous alternation behavior (SA) and at adulthood, their response to novel or aversive situations, open field, extinction and punishment following acquisition of an appetitive response and two-way active avoidance, were assessed. In prenatally stressed rats, the development of SA was significantly delayed. On repeated exposure to an open field they were less active; control rats had elevated plasma corticosterone (CCS) on days 2 and 4 of open field exposure, while prenatally stressed rats had significantly raised plasma CCS after each exposure (days 1-8). Furthermore, punishment-induced suppression of an appetitive response was enhanced. Acquisition of active avoidance was faciliated in female but reduced in male prenatally stressed offspring. It is suggested that random prenatal noise and light stress may cause impairment of development of hippocampal function which lasts into adulthood. This impairment is manifested as an increase in vulnerability and a decrease in habituation to stressful stimuli.