Prenatal and adult stress interplay — behavioral implications

Paeoniflorin ameliorates depressive-like behavior in prenatally stressed offspring by restoring the HPA axis- and glucocorticoid receptor- associated dysfunction

BACKGROUND

Prenatal stress (PS) can increase the risk of nervous, endocrine and metabolic diseases and induce depression in offspring. Paeoniflorin (PA) is an amorphous glucoside isolated from the aqueous extract of roots of the peony plant (Paeonia lactiflora Pall.) and exerts various pharmacological effects in the nervous system.

METHODS

Male prenatally stressed offspring were used to investigate the antidepression-like effects and possible mechanism of PA. We measured animal behavior, HPA axis, Nissil staining, and Ng expression. Additionally, we assessed the modulation of hippocampal glucocorticoid receptors (GR) nuclear translocation and SNARE complex expression by western blotting.

RESULTS

The results showed that administration of PA (15, 30, and 60 mg/kg/day, i.g.) for 28 days markedly increased sucrose intake and decreased the immobility time and the total number of crossings, center crossings, rearing, and grooming in male PS offspring. Moreover, PA significantly reduced the serum corticosterone (CORT), adrenocorticotropin (ACTH), corticotropin-releasing hormone (CRH) and hippocampal glutamate (Glu) levels in male PS offspring, which were stimulated by an increase of GR nuclear translocation. Furthermore, PA markedly increased neurogranin (Ng) protein expression in the hippocampus CA3 region in offspring. PA also markedly decreased hippocampal Glu by inhibiting SNAP25, VAMP2, Syntaxin1a and related protein expression; SNARE complex formation; and EAAT2/3, NR1, NR2A, and FKBP5 protein expression.

CONCLUSIONS

Taken together, the results of this study show that PA has antidepression-like effects in male PS offspring, partially due to the HPA axis, GR dysfunction and Glu transport system.

Effects of psychological or physical prenatal stress on attention and locomotion in juvenile rats

Background: Prenatal stress has been shown to affect the cognition of offspring, including memory and learning abilities.Methods: In the current study, the long-term effects of chronic prenatal exposure to the physical or psychological stress on locomotion and attention were evaluated by using open field test (OFT) and prepulse inhibition (PPI) of the acoustic startle reflex (ASR). In addition, the level of corticosterone was measured after the ASR trial.Results: Male and female rodents that underwent prenatal physical and psychological stress had an augmented velocity in OFT, and only male animals showed an increased ASR. Neither male nor female offsprings had an alteration in the level of corticosterone and PPI values regardless of the stress type.Conclusion: Our results revealed that exposure to stress during the development of fetus increases ASR in a sex-dependent manner. This finding might implicate the effect of prenatal stress on attention in male offspring regardless of the stress type.

Life-Course Contribution of Prenatal Stress in Regulating the Neural Modulation Network Underlying the Prepulse Inhibition of the Acoustic Startle Reflex in Male Alzheimer's Disease Mice

The prepulse inhibition (PPI) of the acoustic startle reflex (ASR), as an index of sensorimotor gating, is one of the most extensively used paradigms in the field of neuropsychiatric disorders. Few studies have examined how prenatal stress (PS) regulates the sensorimotor gating during the lifespan and how PS modifies the development of amyloid-beta (Aβ) pathology in brain areas underlying the PPI formation. We followed alternations in corticosterone levels, learning and memory, and the PPI of the ASR measures in APPNL-G-F/NL-G-F offspring of dams exposed to gestational noise stress. In-depth quantifications of the Aβ plaque accumulation were also performed at 6 months. The results indicated an age-dependent deterioration of sensorimotor gating, long-lasting PS-induced abnormalities in PPI magnitudes, as well as deficits in spatial memory. The PS also resulted in a higher Aβ aggregation predominantly in brain areas associated with the PPI modulation network. The findings suggest the contribution of a PS-induced hypothalamic-pituitary-adrenal (HPA) axis hyperactivity in regulating the PPI modulation substrates leading to the abnormal development of the neural protection system in response to disruptive stimuli. The long-lasting HPA axis dysregulation appears to be the major underlying mechanism in precipitating the Aβ deposition, especially in brain areas contributed to the PPI modulation network.

Nrg1 deficiency modulates the behavioural effects of prenatal stress in mice

Little is known about the exact genes that confer vulnerability or resilience to environmental stressors during early neurodevelopment. Partial genetic deletion of neuregulin 1 (Nrg1) moderates the neurobehavioural effects of stressors applied in adolescence and adulthood, however, no study has yet examined its impact on prenatal stress. Here we examined whether Nrg1 deficiency in mice modulated the impact of prenatal stress on various behaviours in adulthood. Male heterozygous Nrg1 mice were mated with wild-type female mice who then underwent daily restraint stress from days 13 to 19 of gestation. Surprisingly, prenatal stress had overall beneficial effects by facilitating sensorimotor gating, increasing sociability, decreasing depressive-like behaviour, and improving spatial memory in adulthood. Such benefits were not due to any increase in maternal care, as prenatal stress decreased nurturing of the offspring. Nrg1 deficiency negated the beneficial behavioural effects of prenatal stress on all measures except sociability. However, Nrg1 deficiency interacted with prenatal stress to trigger locomotor hyperactivity. Nrg1 deficiency, prenatal stress or their combination failed to alter acute stress-induced plasma corticosterone concentrations. Collectively these results demonstrate that Nrg1 deficiency moderates the effects of prenatal stress on adult behaviour, but it does so in a complex, domain-specific fashion.

Antidepressive-like effect of imperatorin from Angelica dahurica in prenatally stressed offspring rats through 5-hydroxytryptamine system

Adolescence is a time of continued brain maturation, particularly in limbic and cortical regions, which undoubtedly plays a role in the physiological and emotional changes. Prenatally stressed offspring rats were used to investigate the potential antidepressive-like effects of imperatorin (IMP) extracted from the root of radix angelica. After 4 weeks of treatment of IMP, behavioral tests (sucrose-preference test, forced-swimming test, and open-field test) were measured. 5-hydroxytryptamine (5-HT) concentration in the hippocampus and frontal cortex was measured using an enzyme-linked immunosorbent assay. Serotonin transporters (5-HTT) and 5-HT1A receptor (5-HT1AR) mRNA expression in the hippocampus and frontal cortex were also determined by real-time PCR. Administration with IMP (15 and 30 mg/kg/day, intragastrically) for 28 days markedly increased the percentage of sucrose (anhedonia), decreased the immobility time, and increased the number of total crossings, center crossings, rearing, and grooming in the male prenatally stressed offspring. Meanwhile, we found that 5-HT concentration in the hippocampus and frontal cortex was significantly increased in the IMP-treated group. Subsequently, we found significantly decreased 5-HTT and increased 5-HT1AR mRNA expressions in the hippocampus and frontal cortex after IMP treatment in the prenatally stressed male offspring. IMP showed antidepressive-like effects and increased 5-HT concentration in male prenatally stressed offspring, suggesting that IMP could be of therapeutic use in preventing depressive-like behavior in adolescence.

Olfactory Bulbectomy in Methamphetamine-Treated Rat Mothers Induces Impairment in Somatic and Functional Development of Their Offspring

Olfactory bulbectomy in rodents is considered a putative model of depression. Depression is often associated with drug addiction. Our previous studies demonstrated that methamphetamine (MA) administration to rat mothers affects both, mothers and their pups. The aim of the present study was to examine the effect of bulbectomy, as a model of depression, and MA administration on behavior of rat mothers and postnatal development of their pups. Adult female Wistar rats were randomly divided into two groups: bulbectomized (OBX) and sham-operated (SH). A period of 20 days was allowed for the development of the depressive-like phenotype. Animals were tested in the motor activity test and 2 % sucrose preference for anhedonia and hyperactive locomotor response to a novel environment, respectively. After then females were impregnated. Pregnant females were exposed to daily subcutaneous (s.c.) injection of MA (5 mg/kg) or saline (SA) during the entire gestation period. Postnatally, maternal behavior and pup development was examined. The effect of a challenge dose of MA (1 mg/kg, s.c.) on behavior was further examined in adult male offspring. Our results showed no differences in the maternal behavior as a matter of bulbectomy, only OBX rats slept more than all the SH controls. Pups from OBX mothers were born with lower birthweight and gained less weight during the postnatal development than pups from SH controls. Both, bulbectomy and MA administration, delayed the eyes opening. As a matter of functional development of the pups, maternal OBX procedure impaired the performance in the Bar-holding test, but only in saline group. OBX/SA group was the worst in the Bar-holding test relative to all the other groups. In addition, pups from OBX mothers dropped more boluses during the Bar-holding test, suggesting that they were more stressed. In adult male offspring, bulbectomy increased immobility only in the SA/SA group. Prenatal MA exposure increased locomotion, while decreasing immobility. In addition, challenge dose of MA in adulthood increased distance traveled, locomotion, rearing, and average and maximal velocity, while decreasing immobility and grooming. In conclusion, our results suggest that depressive-like phenotype of rat mothers induces impairment in somatic and functional development of their male offspring.

Long-Term Sertraline Intake Reverses the Behavioral Changes Induced by Prenatal Stress in Rats in a Sex-Dependent Way

Early life stress is a major factor underlying the vulnerability to respond to stressful events later in life. The present study attempted to evaluate the role of prenatal stress affecting the development of stress-related disorders and their reversion by postnatal exposure to Sertraline (SERT), a front-line medication for medication for posttraumatic stress disorder (PTSD) in humans. To achieve this, adult male and female prenatally stressed (PS) or unstressed (Controls) offspring rats, following oral chronic treatment with SERT (5 mg/kg/day; from 1 month to 4 months old), or not, were studied prior to and after a traumatic event. First, anxiety-like behavior during the prepulse inhibition (PPI) test, a modulation of the startle reflex, was examined in all animals. Subsequently, the animals were subjected to a session of mild inescapable footshocks (IS; 0.35 mA, 5 s) in a shuttle box that was followed by 4 days of situational reminders in the aversive context. Prior to the footshocks no effects of PS or SERT were shown, and no changes in PPI and the habituation to the shuttle box were found. After them, PS led animals to exhibit behavioral alterations. When compared to the Controls, PS animals of both sexes displayed less rearing activity in the aversive environment. PS males responded less to footshock delivery and, in most of the animals, fear extinction was impaired. Moreover, the early postnatal exposure to SERT lessened the behavioral impact of PS in females, while in males it had no effect. Current results extend previous data from our laboratory, showing that PS heightened vulnerability to stress later on, and that SERT acts differently in males and females.

Behavioural outcomes of adult female offspring following maternal stress and perinatal fluoxetine exposure

Depression, anxiety, and stress are common in pregnant women. One of the primary pharmacological treatments for anxiety and depression is the antidepressant fluoxetine (Flx). Maternal stress, depression, and Flx exposure are known to effect neurodevelopment of the offspring, however, their combined effects have been scarcely studied, especially in female offspring. The present study investigated the combined effects of maternal stress during pregnancy and perinatal exposure to Flx on the behaviour of female mice as adults.

METHODS

Mouse dams were exposed to either chronic unpredictable stress (embryonic (E) day 7 to E18), or FLX (E15- postnatal day 12), or a combination of stress and FLX or left untreated. At two months of age, the female offspring went through a comprehensive behavioural test battery.

RESULTS

Maternal stress led to increased activity and alterations of prepulse inhibition in the adult female offspring. Maternal treatment with Flx had a potentially beneficial effect on spatial memory. The combination of prenatal stress and perinatal Flx exposure did not interact in their effects. These results suggest that gestational Flx exposure may have a limited negative impact on female offspring.

The effects of sertraline administration from adolescence to adulthood on physiological and emotional development in prenatally stressed rats of both sexes

Sertraline (SERT) is a clinically effective Selective Serotonin Reuptake Inhibitor (SSRI) known to increase and stabilize serotonin levels. This neurotransmitter plays an important role in adolescent brain development in both rodents and humans, and its dysregulation has been correlated with deficits in behavior and emotional regulation. Since prenatal stress may disturb serotoninergic homeostasis, the aim of this study was to examine the long-lasting effects of exposure to SERT throughout adolescence on behavioral and physiological developmental parameters in prenatally stressed Wistar rats. SERT was administered (5 mg/kg/day p.o.) from the age of 1-3 months to half of the progeny, of both sexes, of gestating dams stressed by use of a restraint (PS) or not stressed. Our data reveal that long-term SERT treatment slightly reduced weight gain in both sexes, but reversed the developmental disturbed "catch-up" growth found in PS females. Neither prenatal stress nor SERT treatment induced remarkable alterations in behavior and had no effects on mean startle reflex values. However, a sex-dependent effects of PS was found: in males the PS paradigm slightly increased anxiety-like behavior in the open field, while in females, it impaired startle habituation. In both cases, SERT treatment reversed the phenomena. Additionally, the PS animals exhibited a disturbed leukocyte profile in both sexes, which was reversed by SERT. The present findings are evidence that continuous SERT administration from adolescence through adulthood is safe in rodents and lessens the impact of prenatal stress in rats.

Is elevated norepinephrine an etiological factor in some cases of schizophrenia?

A number of hypotheses have been put forth regarding the etiology of schizophrenia, including the dopamine hypothesis, NMDA receptor hypofunction hypothesis, and others. A lesser known theory is that elevated noradrenergic signaling plays a causative role in the disease. This paper briefly re-examines the merits of this hypothesis, including as it relates to some recently published studies. Several lines of evidence are investigated, including: endogenous level studies of norepinephrine (NE); modulation of the disease by noradrenergic drugs; association of the disease with bipolar disorder and hypertension, since these latter two conditions may involve elevated NE transmission; and effects of psychological stress on the disease, since stress can produce elevated release of NE. For many of these lines of evidence, their relationship with prepulse inhibition of startle is examined. A number of these studies support the hypothesis, and several suggest that elevated NE signaling plays a particularly prominent role in the paranoid subtype of schizophrenia. If the hypothesis is correct for some persons, conventional pharmaceutical treatment options, such as use of atypical antipsychotics (which may themselves modulate noradrenergic signaling), may be improved if selective NE transmission modulating agents are added to or even substituted for these conventional drugs.

Chronic high-fat diet increases acute neuroendocrine stress response independently of prenatal dexamethasone treatment in male rats

OBJECTIVE

Intrauterine growth restriction (IUGR) has been associated with metabolic disorders later in life such as obesity and diabetes as well as psychiatric disorders such as depression and schizophrenia. Therefore, we wanted to investigate whether behavioural, metabolic or neuroendocrine abnormalities could be provoked or exacerbated by a high-fat diet (HFD) in an experimental model of IUGR.

METHODS

Pregnant dams were exposed to dexamethasone (DEX) in the third gestational week to induce IUGR. Late adolescent male offspring of DEX- and vehicle-treated dams were then fed a HFD or standard chow for 8 weeks and subjected to a variety of assessments.

RESULTS

Only diet affected the hypothalamus-pituitary-adrenal (HPA) axis stress response, as HFD doubled the observed corticosterone levels following acute restraint. HFD and prenatal DEX exposure concomitantly exacerbated depressive-like behaviour in the forced swim test, even though no interaction was seen. Prenatal DEX treatment tended to increase the basal acoustic startle response (ASR), while an interaction between HFD and DEX was present in the ASR pre-pulse inhibition suggestive of fundamental changes in neuronal gating mechanisms. Metabolic parameters were only affected by diet, as HFD increased fasting glucose and insulin levels.

CONCLUSION

We conclude that chronic HFD may be more important in programming of the HPA axis stress responsiveness than an adverse foetal environment and therefore potentially implies an increased risk for developing psychiatric and metabolic disease.

Effects of duration and timing of prenatal stress on hippocampal myelination and synaptophysin expression

The relationship between prenatal stress (PS) exposure and neurodevelopmental deficits remains inconclusive, especially when assessing the role of PS duration and timing and sex-dependent effects. This study explored a sex-specific association between the duration and timing of exposure and the outcomes of PS-induced neurotoxicity in hippocampal microstructure, synaptophysin expression, and neurobehavioral performance in rats. Pregnant rats were randomly assigned to control, PS-ML (exposed to prenatal restraint stress in the mid-to-late period of pregnancy), or PS-L (exposed in the late period of pregnancy) groups, and offspring in each group were divided into two subgroups by sex. Surface-righting reflex test, cliff avoidance test and Morris water maze test showed that neurodevelopmental levels were reduced in PS-treated pups but without significant sex differences. On postnatal day 22, hippocampal microstructure was examined by electron microscopy, and the expression of hippocampal synaptophysin was assessed by western blot. Abnormal ultrastructural appearance of hippocampal neurons and myelin sheaths, more degenerating neurons and higher G-ratios were found in young PS-ML and PS-L rats as well as reduced expression of hippocampal synaptophysin, although PS-ML pups were more greatly affected than PS-L, with males showing slightly greater impairments than females. These findings suggest that hippocampal hypo-myelination and decreased synaptophysin expression in neurodevelopment may be a duration and time-dependent effect of prenatal stress exposure, modified slightly by sex.

Effects of prenatal stress on pregnancy and human development: mechanisms and pathways

A growing body of research shows that prenatal stress can have significant effects on pregnancy, maternal health and human development across the lifespan. These effects may occur directly through the influence of prenatal stress-related physiological changes on the developing fetus, or indirectly through the effects of prenatal stress on maternal health and pregnancy outcome which, in turn, affect infant health and development. Animal and human studies suggest that activation of the maternal stress response and resulting changes in endocrine and inflammatory activity play a role in the aetiology of these effects. Ongoing research is focusing on clarifying these mechanisms, understanding the role of racial and cultural factors in these effects, and examining the epigenetic and transgenerational influences of prenatal stress.

Caffeine-induced activated glucocorticoid metabolism in the hippocampus causes hypothalamic-pituitary-adrenal axis inhibition in fetal rats

Epidemiological investigations have shown that fetuses with intrauterine growth retardation (IUGR) are susceptible to adult metabolic syndrome. Clinical investigations and experiments have demonstrated that caffeine is a definite inducer of IUGR, as children who ingest caffeine-containing food or drinks are highly susceptible to adult obesity and hypertension. Our goals for this study were to investigate the effect of prenatal caffeine ingestion on the functional development of the fetal hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis and to clarify an intrauterine HPA axis-associated neuroendocrine alteration induced by caffeine. Pregnant Wistar rats were intragastrically administered 20, 60, and 180 mg/kg·d caffeine from gestational days 11–20. The results show that prenatal caffeine ingestion significantly decreased the expression of fetal hypothalamus corticotrophin-releasing hormone. The fetal adrenal cortex changed into slight and the expression of fetal adrenal steroid acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (P450scc), as well as the level of fetal adrenal endogenous corticosterone (CORT), were all significantly decreased after caffeine treatment. Moreover, caffeine ingestion significantly increased the levels of maternal and fetal blood CORT and decreased the expression of placental 11β-hydroxysteroid dehydrogenase-2 (11β-HSD-2). Additionally, both in vivo and in vitro studies show that caffeine can downregulate the expression of fetal hippocampal 11β-HSD-2, promote the expression of 11β-hydroxysteroid dehydrogenase 1 and glucocorticoid receptor (GR), and enhance DNA methylation within the hippocampal 11β-HSD-2 promoter. These results suggest that prenatal caffeine ingestion inhibits the development of the fetal HPA axis, which may be associated with the fetal overexposure to maternal glucocorticoid and activated glucocorticoid metabolism in the fetal hippocampus. These results will be beneficial in elucidating the developmental toxicity of caffeine and in exploring the fetal origin of adult HPA axis dysfunction and metabolic syndrome susceptibility for offspring with IUGR induced by caffeine.

Prescient human fetuses thrive

Fetal detection of adversity is a conserved trait that allows many species to adapt their early developmental trajectories to ensure survival. According to the fetal-programming model, exposure to stressful or hostile conditions in utero is associated with compromised development and a lifelong risk of adverse health outcomes. In a longitudinal study, we examined the consequences of prenatal and postnatal exposure to adversity for infant development. We found increased motor and mental development during the 1st year of life among infants whose mothers experienced congruent levels of depressive symptoms during and after pregnancy, even when the levels of symptoms were relatively high and the prenatal and postnatal environments were unfavorable. Congruence between prenatal and postnatal environments prepares the fetus for postnatal life and confers an adaptive advantage for critical survival functions during early development.

Effects of chronic maternal stress on hypothalamo-pituitary-adrenal (HPA) function and behavior: no reversal by environmental enrichment

Maternal stress during pregnancy is linked to increased risk for impaired behavioral and emotional development and affective disorders in children. In animal models, acute periods of prenatal or postnatal stress have profound effects on HPA function and behavior in adult offspring. However, few animal studies have determined the impact of chronic exposure to stress throughout the perinatal period. The objective of this study was to determine the effects of chronic maternal stress (CMS) during the 2nd half of pregnancy and nursing on HPA function, locomotor behavior and prepulse inhibition in adult guinea pig offspring, as well as to determine whether environmental enrichment (EE) could reverse the effects of CMS. Guinea pigs were exposed to a random combination of variable stressors every other day over the 2nd half of gestation and from postnatal day (pnd) 1 until weaning (pnd25). Following weaning, offspring were housed in either standard conditions or EE. In both adult male and female offspring, there was no effect of CMS on basal or activated HPA function. CMS significantly increased locomotor activity in an open-field in male offspring, though no effect was observed in females. In female offspring, CMS disrupted PPI; however there was no effect on male PPI. EE had a number of effects on HPA function and behavior but in most cases these were independent of the influence of CMS. EE significantly elevated basal cortisol levels in male offspring at pnd70, whereas in female offspring, EE interacted with CMS to elevate basal cortisol levels from pnd35 to pnd70. In female offspring, EE decreased locomotor activity. In males, EE enhanced PPI; however in female offspring EE disrupted PPI. In conclusion, while CMS had minimal effects on HPA function, there were significant long-term sex-specific effects on behavior. EE did not reverse the effects observed as a result of CMS, but rather modified HPA function and behavior independently of CMS. Further, there was significant interaction of CMS with EE that resulted in elevation of basal HPA function in female offspring. These data, combined with previous studies from our laboratory, suggest that acute phases of maternal stress in late pregnancy may have greater long-term effects on HPA function and related behaviors than prolonged chronic maternal stress.

Effects of GH deficiency and GH replacement on inter-male aggressiveness in mice

OBJECTIVE

Growth hormone (GH) has been suggested to influence aggressive behavior in several species, but no data are presently available in GH-deficient (GHD) animals. The aim of this study was to elucidate the effects of GHD on aggressive behavior in a mouse model of isolated GHD due to removal of the GHRH gene (GHRH knock out, GHRHKO), and to evaluate the effects of GH replacement.

DESIGN

We studied two groups of adult male mice: Ten GH-sufficient animals heterozygous for GHRHKO allele (HTZ), and 30 GHRHKO animals. Behavior was measured by scoring several aggression parameters after isolation, when the animal was challenged against an intruder both in neutral and home cage. Animals were then re-studied after the GHRHKO mice were left untreated (control, Ctrl), or were treated for 2 weeks with daily subcutaneous recombinant GH or with vehicle (Veh). Blood samples were collected before and after GH or Veh treatment, and assayed for serum IGF-I and testosterone.

RESULTS

The GHRHKO mice showed significantly reduced aggressiveness compared to HTZ animals. GH (but not Veh) administration normalized isolation-induced aggressive behavior in GHRHKO mice, despite lack of full serum IGF-I normalization. No difference was noted in serum testosterone levels among all groups at any of the time points.

CONCLUSIONS

These findings show that GHD reduces aggressive behavior in GHRHKO mice, that GH replacement normalizes aggressiveness, and that this behavior change is not related to an increase in serum testosterone.

Effects of neonatal systemic inflammation on blood-brain barrier permeability and behaviour in juvenile and adult rats

Several neurological disorders have been linked to inflammatory insults suffered during development. We investigated the effects of neonatal systemic inflammation, induced by LPS injections, on blood-brain barrier permeability, endothelial tight junctions and behaviour of juvenile (P20) and adult rats. LPS-treatment resulted in altered cellular localisation of claudin-5 and changes in ultrastructural morphology of a few cerebral blood vessels. Barrier permeability to sucrose was significantly increased in LPS treated animals when adult but not at P20 or earlier. Behavioural tests showed that LPS treated animals at P20 exhibited altered behaviour using prepulse inhibition (PPI) analysis, whereas adults demonstrated altered behaviour in the dark/light test. These data indicate that an inflammatory insult during brain development can change blood-brain barrier permeability and behaviour in later life. It also suggests that the impact of inflammation can occur in several phases (short- and long-term) and that each phase might lead to different behavioural modifications.

Influence of diurnal phase on startle response in adult rats exposed to dexamethasone in utero

Depression and pathological anxiety disorders are among the most prevalent neurological diseases in the world and can be precipitated and exacerbated by stress. Prenatal stress alters both behavioral and endocrine responses to stressful stimuli in later life. We have previously observed increased basal acoustic startle response (ASR) in Wistar rats exposed to stress or dexamethasone (DEX) in utero when tested during the light phase of the circadian rhythm, and decreased prepulse inhibition (PPI) in similar animals tested during the dark phase of the cycle. We speculated that this observation of increased basal startle might be influenced by diurnal phase. In the present study, adult female Sprague Dawley rats, stressed prenatally with DEX (200 μg/kg, gestational days 14-21) and postnatally by blood sampling under restraint, were tested for the ASR during both circadian phases (light and dark). Basal startle was increased in animals tested both during the light and the dark phases of the cycle. We hereby replicated our earlier findings in a new strain and laboratory, thus strengthening the validity of our model regarding prenatal stress effects on ASR in female offspring. Our results indicate that observation of increased basal ASR is not solely dependent on diurnal phase. We found no difference in hippocampal glucocorticoid and mineral corticoid receptor expression between groups.