Prenatal endotoxin exposure alters behavioural pain responses to lipopolysaccharide in adult offspring

Evidence suggests that exposure to bacterial endotoxin in early life can alter the production of pro-inflammatory cytokines in later life. This phenomenon may have significant consequences for pain and pain related behaviours as pro-inflammatory cytokines heighten pain sensitivity. This association has yet to be examined. As such, the aim of the present study was to characterize pain behaviours in adult rat offspring following prenatal endotoxin (PE) exposure. Pregnant F344 rats received endotoxin (200 µg/kg, s.c.) or saline on gestational days 16, 18 and 20. Pain thresholds were assessed in the adult PE offspring (n = 23) and control offspring (n = 24) prior to and 4 h following administration of lipopolysaccharide (LPS; 100 µg/kg, s.c.). Three assays of pain were employed — the hot plate, tail immersion and von Frey tests. Results demonstrated sex-specific effects of prenatal endotoxin on the offspring, with PE males displaying unaltered pain thresholds on the von Frey test post-LPS administration (p < 0.01), while male control offspring (n = 24) displayed the expected hyperalgesia. Male PE offspring also displayed increased pain thresholds on the tail immersion test (p < 0.01), while no change in pain sensitivity was observed in control males following LPS exposure. No difference in response was observed between the female PE and control offspring on the von Frey test, however PE female offspring displayed increased thresholds on the tail immersion test compared to baseline — an effect not observed in the control female offspring. Pain sensitivity on the hot plate test was unaffected by prenatal exposure to endotoxin. These data suggest that prenatal exposure to products associated with bacterial infection have the capacity to alter pain responses, which are evident in the adult offspring.     

Prenatal cocaine exposure alters potassium-evoked dopamine release dynamics in rat striatum

The emerging profile for the effects of prenatal cocaine exposure presents two prominent features in the exposed offspring: cognitive/attention deficits and an age-associated trend toward motor/tone abnormalities up to 2 years of age. One candidate mechanism underlying these clinical features is long-lasting alterations to dopamine (DA) neuron function. However, the impact of prenatal cocaine exposure on DA release in dopaminergic terminal fields in vivo in mature offspring is poorly understood. Long-Evans female rats were implanted with an i.v. access port, bred, and given saline or cocaine-HCl (3 mg/kg/ml) for gestational days (GD) 8-14 (1x/day), GD 15-21 (2x/day), or GD 8-21 (1x/day-GD 8-14, 2x/day-GD 15-21). Using in vivo high-speed chronoamperometric recordings, potassium-stimulated DA release was measured in striatum of anesthetized male offspring 90-150 days after birth. There was a trend toward increased potassium-evoked DA signal amplitudes in offspring exposed to cocaine at any time period examined. In offspring exposed to cocaine during GD 8-21 and GD 15-21, but not at GD 8-14, there were significant decreases in the clearance capacity of the potassium-evoked DA signal compared with control offspring. The time required to clear 80% of the evoked DA signal (T(80)) in striatum for DA was significantly prolonged (approximately 150% of control) and this effect was further increased in the mean-evoked DA concentration range for these two groups. We also measured total dopamine transporter (DAT) and tyrosine hydroxylase protein levels in these offspring by blot immunolabeling and found a small, but significant, decrease in DAT protein in striatum from offspring exposed at GD 8-21 and GD 15-21. Collectively, these data demonstrate that prenatal cocaine exposure during dopamine neuron neurogenesis has long-lasting effects on DA neuron function lasting into early adulthood which may be related in part to steady state DAT protein levels. These molecular events may be associated with established cognitive deficits and perhaps the trends seen in altered motor behavior.     

Effect of paliperidone and risperidone on extracellular glutamate in the prefrontal cortex of rats exposed to prenatal immune activation or MK-801

The NMDA glutamate hypofunction model of schizophrenia is based in part upon acute effects of NMDA receptor blockade in humans and rodents. Several laboratories have reported glutamate system abnormalities following prenatal exposure to immune challenge, a known environmental risk factor for schizophrenia. Here we report indices of NMDA glutamate receptor hypofunction following prenatal immune activation, as well as the effects of treatment during periadolescence with the atypical antipsychotic medications risperidone and paliperidone. Pregnant Sprague-Dawley rats were injected with polyinosinic:polycytidylic acid (poly I:C) or saline on gestational day 14. Male offspring were treated orally via drinking water with vehicle, risperidone (0.01mg/kg/day), or paliperidone (0.01mg/kg/day) between postnatal days 35 and 56 (periadolescence) and extracellular glutamate levels in the prefrontal cortex were determined by microdialysis at PD 56. Consistent with decreased NMDA receptor function, MK-801-induced increases in extracellular glutamate concentration were markedly blunted following prenatal immune activation. Further suggesting NMDA receptor hypofunction, prefrontal cortex basal extracellular glutamate was significantly elevated (p<0.05) in offspring of poly I:C treated dams. Pretreatment with low dose paliperidone or risperidone (0.01mg/kg/day postnatal days 35-56) normalized prefrontal cortical basal extracellular glutamate (p<0.05 vs. poly I:C vehicle-treatment). Pretreatment with paliperidone and risperidone also prevented the acute MK-801-induced increase in extracellular glutamate. These observations demonstrate decreased NMDA receptor function and elevated extracellular glutamate, two key features of the NMDA glutamate receptor hypofunction model of schizophrenia, during periadolescence following prenatal immune activation. Treatment with the atypical antipsychotic medications paliperidone and risperidone normalized basal extracellular glutamate. Demonstration of glutamatergic abnormalities consistent with the NMDA glutamate receptor hypofunction model of schizophrenia as an early developmental consequence of prenatal immune action provides a model to identify novel early interventions targeting glutamatergic systems which play an important role in both positive and negative symptoms of schizophrenia.     

Prenatal cocaine exposure increases heart susceptibility to ischaemia–reperfusion injury in adult male but not female rats

The present study tested the hypothesis that prenatal cocaine exposure differentially regulates heart susceptibility to ischaemia–reperfusion (I/R) injury in adult offspring male and female rats. Pregnant rats were administered intraperitoneally either saline or cocaine (15 mg kg⁻¹) twice daily from day 15 to day 21 of gestational age. There were no differences in maternal weight gain and birth weight between the two groups. Hearts were isolated from 2-month-old male and female offspring and were subjected to I/R (25 min/60 min) in a Langendorff preparation. Preischaemic values of left ventricular (LV) function were the same between the saline control and cocaine-treated hearts for both male and female rats. Prenatal cocaine exposure significantly increased I/R-induced myocardial apoptosis and infarct size, and significantly attenuated the postischaemic recovery of LV function in adult male offspring. In contrast, cocaine did not affect I/R-induced injury and postischaemic recovery of LV function in the female hearts. There was a significant decrease in PKCɛ and phospho-PKCɛ levels in LV in the male, but not female, offspring exposed to cocaine before birth. These results suggest that prenatal cocaine exposure causes a sex-specific increase in heart susceptibility to I/R injury in adult male offspring, and the decreased PKCɛ gene expression in the male heart may play an important role.     

Effects of gestational stress and neonatal handling on pain,analgesia, and stress behavior of adult mice

Stressors presented during the late prenatal and early postnatal periods can have long-term effects on offspring behavior, due to the sensitive periods in the formation of brain circuitry associated with early development. This study investigated the long-term effects of prenatal (restraint during the last week of gestation) and postnatal (daily handling for 14 days postnatal) stress, alone and in combination, on adulthood pain behavior, analgesic responses to stress and morphine, and on behavioral indices of stress reactivity. We found that all of the adult responses measured were altered by perinatal manipulations. Nociceptive thresholds were increased by prenatal or by postnatal stress in males and females; application of both stressors in combination negated these effects. Elevations in morphine analgesia were also observed in animals undergoing either perinatal stressor, but not in those who received both stressors. Behavioral and analgesic responses to stress were consistent with previous observations of reduced stress responsiveness following neonatal handling, with some sex-specific findings. Male and female handled subjects exhibited decreases in stress behavior, and both groups of female handled subjects (regardless of prenatal stress [PS] condition) exhibited decreases in stress-induced analgesia (SIA). Males, on the other hand, exhibited decreases in SIA only if they were prenatally stressed (regardless of handling condition). Thus, prenatal and postnatal stressors have differing effects on the neural circuitry underlying pain, pain inhibition, and stress behavior.     

Sex-specific susceptibility to cocaine in rats with a history of prenatal stress

Across species, maternal stress during prenatal life (prenatal stress [PS]) increases the expression of health complications in the developing offspring. While numerous reports indicate that male rats with a history of PS are vulnerable to psychiatric disease-like symptoms and drugs of abuse, comparable studies with females have been more limited. Here, the effects of PS in male and female rats were compared with the use of two well-validated tests of drug abuse susceptibility — the acquisition of cocaine self-administration and the expression of sensitization to the drug's psychomotor-activating properties. When a low dose (0.2 mg/kg/infusion) was available for self-administration across 15 1-hour test sessions, drug-taking behaviors were unaffected by an individual's early-life stress history. On an escalating-doses regimen (0.3-0.5 mg/kg/infusion) of self-administration, however, exposure to PS selectively facilitated the rate of acquisition and overall drug intake of males. Conversely, cocaine-induced psychomotor sensitization was augmented by PS in females, but not males. We conclude that exposure to PS enhances the reinforcing and psychomotor-sensitizing properties of cocaine male and female rats, respectively, later in life. Thus, these results suggest that gestational stress is a sex-specific risk factor for different aspects of substance abuse.     

Differential effects of prenatal cocaine exposure on selected subunit mRNAs of the GABA(A) receptor in rabbit anterior cingulate cortex

We have previously shown that in the dopamine-rich anterior cingulate cortex (ACC), significant changes in γ-aminobutyric acid (GABA) immunoreactivity occur in the offspring of rabbits given intravenous injections of cocaine (3 mg/kg) twice daily during pregnancy. In the present study, the effects of prenatal cocaine exposure on the developmental expression of specific GABA_A receptor subunit mRNAs were investigated. We compared the distribution of the 1, β2, and γ2 subunit mRNAs in cocaine- and saline-treated offspring aged postnatal days 20 and 60 (P20, P60). At P20, prenatal cocaine exposure resulted in a significant increase in 1 subunit mRNA in ACC lamina III and a significant reduction in the amounts of the β2 subunit mRNA in ACC lamina II. No differences between cocaine- and saline-treated controls were detected for γ2 subunit mRNA levels in ACC. Although the pattern of labeling was altered in cocaine-exposed animals, Nissl sections revealed no differences in lamination, indicating that the changes in GABA_A subunit mRNAs could not be attributed to abnormal cytoarchitectonics. In P60 brains, no significant differences were observed between cocaine- and saline-treated material, indicating that the observed differences were transient. Collectively, our data show that prenatal cocaine exposure elicits differential, lamina-specific changes in mRNA levels encoding selected subunits of the GABA_A receptor. Since these changes occur during a critical period when fine tuning of synaptic organization is achieved by processes of selective elimination or stabilization of synapses, we suggest that specific subunit mRNAs of the GABA_A receptor play a role in cortical development.     

Effects of prenatal exposure to cocaine on conditional discrimination learning in adult rats.

Adult male rats that were gestationally exposed to cocaine and control offspring were trained on an instrumental conditioning task for assessment of the acquisition and reversal of an appetitive conditional discrimination based on olfactory cues. Offspring were derived from Sprague-Dawley dams that had received subcutaneous injections of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on Gestational Days 8-20, pair-fed (PF) dams that were injected with saline, nutritional control dams (NC) that had received saline injections, and nontreated control dams (LC). There were no differences among the prenatal treatment groups in acquisition of the barpress response or response rate throughout all phases of training. All prenatal treatment groups required approximately the same number of sessions to criterion on the initial odor discrimination. In contrast, adult C40 offspring required more sessions to acquire the reversal of the conditional discrimination than did animals from the other treatment groups (PF, NC, and LC). In addition, even at criterion performance for acquisition of the reversal discrimination, C40 animals exhibited lower accuracy on the first 10 responses and made significantly more errors before the first reward. Taken together with previous results, these findings suggest that gestational exposure to cocaine results in long-lasting alterations in performance on conditioning tasks that are evident early in life and that persist into adulthood.     

Prenatal dexamethasone exposure affects anxiety-like behaviour and neuroendocrine systems in an age-dependent manner

Prenatal stress has been reported to alter the development of the central nervous system functions. This alteration is thought to be partly caused by increased fetal exposure to glucocorticoid. To clarify how prenatal stress affects neuroendocrine systems and behaviour in an age-dependent manner, we administered a synthetic glucocorticoid, dexamethasone, as a stressor to pregnant rats at gestational days 16–21 and examined the developmental changes in behaviour, hypothalamic corticotropin-releasing factor mRNA expression, corticosterone response and glucocorticoid receptor expression in male offspring. Prenatal dexamethasone exposure decreased corticotropin-releasing factor mRNA in the hypothalamus and disturbed the plasma corticosterone response to restraint stress in the offspring at postnatal week 4 (PW4). In contrast, it was not until PW10 that increased anxiety-like behaviour emerged in the dexamethasone-exposed offspring. In association with the acquisition of increased anxiety-like behaviour at PW10, glucocorticoid receptor expression was decreased in the amygdala in dexamethasone-exposed offspring at PW7 and PW10. Thus, our longitudinal analysis suggests that prenatal exposure to glucocorticoid hampers neuroendocrinological development in the offspring during early life, and that this disturbance results in the induction of increased anxiety-like behaviour in adulthood.     

Prenatal stress interacts with prepuberal social isolation to reduce male copulatory behavior

Male offspring of female rats exposed to the stress of restraint and high intensity light during Day 14–21 of gestation were weaned when 22 days old into individual cages (social isolation) or into group cages with 2 other males (social rearing). Copulatory behavior was reduced by prenatal stress or social isolation alone and was absent in males exposed to both stress and prepuberal isolation. Adult therapy consisting of living with young females restored copulatory behavior in some stressed males only if they were reared prepuberally in a social environment. Stressed isolates showed chronic deficits in sexual behavior relative to controls. The study indicates that prenatal stress and prepuberal social isolation can interact to determine adult copulatory potentials in male rats.     

Prenatal cocaine exposure increases anxiety,impairs cognitive function and increases dendritic spine density in adult rats: influence of sex

Cocaine exposure during pregnancy can impact brain development and have long-term behavioral consequences. The present study examined the lasting consequences of prenatal cocaine (PN-COC) exposure on the performance of cognitive tasks and dendritic spine density in adult male and female rats. From gestational day 8 to 20, dams were treated daily with 30 mg/kg (ip) of cocaine HCl or saline. At 62 days of age, offspring were tested consecutively for anxiety, locomotion, visual memory and spatial memory. PN-COC exposure significantly increased anxiety in both sexes. Object recognition (OR) and placement (OP) tasks were used to assess cognitive function. Behavioral tests consisted of an exploration trial (T1) and a recognition trial (T2) that were separated by an inter-trial delay of varying lengths. Male PN-COC subjects displayed significantly less time investigating new objects or object locations during T2 in both OR and OP tasks. By contrast, female PN-COC subjects exhibited impairments only in OR and only at the longest inter-trial delay interval. In addition, gestational cocaine increased dendritic spine density in the prefrontal cortex and nucleus accumbens in both genders, but only females had increased spine density in the CA1 region of the hippocampus. These data reveal that in-utero exposure to cocaine results in enduring alterations in anxiety, cognitive function and spine density in adulthood. Moreover, cognitive deficits were more profound in males than in females.     

Ethanol sensitivity in rats: effect of prenatal stress

The present study examined whether sensitivity to ethanol could be altered by prenatal stress exposure. Pregnant female rats were handled during the third week of gestation and the offspring were tested for ethanol sensitivity as adults. Compared to control offspring, the following characteristic responses to acute ethanol were significantly attenuated in prenatally stress-exposed rats: the decreases in body temperature, motor coordination and startle amplitude, and the increases in circulating corticosterone and free fatty acids. Ethanol-induced impairment of swim performance, in contrast, was potentiated in these animals. Since no differences were found in blood or breath ethanol levels, the rate of ethanol metabolism was probably not affected by prenatal stress. Rather, the altered responses appear to result from long-term changes in central nervous system sensitivity to ethanol.     

The behavioral response to novelty is altered in rats neonatally exposed to cocaine

It has recently been suggested that the effects of in utero cocaine exposure may result in subtle deficits related to a challenging environment, including exposure to novelty or stress. This study used a neonatal drug-exposure model to examine the behavioral response to a novel environment in rodents. Subjects were artificially reared (AR) from postnatal Days 4-10. There were four treatment groups; AR 40 mg/kg/day cocaine, AR 20 mg/kg/day cocaine, AR control group receiving no drug, and a normally reared control. In Experiment 1, subjects were tested for their preference of maternal home-cage or clean wood-chip odors in a T-maze on postnatal Day 15. Subjects from all treatment groups preferred the maternal odor. In Experiment 2, subjects were habituated to four familiar odors and tested with a novel odor in an open field (postnatal Days 16-21). Neonatal exposure to 20 mg/kg/day cocaine led to an overall increase in exploratory behavior during testing, whereas 40 mg/kg/day did not, supporting the hypothesis that developmental exposure to cocaine at some doses may alter the offspring's response to a changing environment.     

Effects of prenatal stress on formalin-induced acute and persistent pain in adult male rats

Behavioral responses of 90-day-old male offspring from female Wistar rats exposed to restraint stress during the last week of pregnancy were studied in the formalin test. Specific biphasic behavioral response characterized acute (phase 1) and persistent tonic pain (phase 2). The intensity of nociceptive responses (evaluated by the number of flexions+ shakings and by the duration of paw licking) in prenatally stressed rats changed only during phase 2. During interphase, facilitation of the flexion+shakings pattern (but not the licking pattern) in response to nociceptive stimulation was seen. The response intensity during phase 1 and the duration of both phases remained unchanged. Our findings suggest that prenatal stress modulates nociceptive sensitivity in 90-day-old offspring: it affects the duration of tonic (inflammatory), but not of acute pain. It is concluded that different mechanisms are responsible for the effects of prenatal stress on acute and persistent pain in the formalin test.     

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.     

Effects of Prenatal Exposure to Buspirone and Stress on Measures of the Pain Response in Inflammation and Depression-Like Behavior in Adult Rats

New data were obtained from prenatally stressed adult rats on the complex mediation of the anxiolytic, antidepressant, and antinociceptive effects of prenatal administration of the 5-HT_1A receptor buspirone. Buspirone (3 mg/kg, 1 ml) was given to female rats from days 9 to 20 of pregnancy and, during the last week, 10 min before immobilization stress. Behavioral measures of tonic pain responses in the formalin test and the depression-like state in the forced swimming test were studied in the adult offspring of both genders. The target was selected on the basis of existing published data on the involvement of 5-HT_1A receptors in the mechanisms of prenatal stress, in the formation of the ascending component of the nociceptive system, in the development of depression-like states, and in the processing of nociceptive information. Prenatal stress was found to increase the duration of licking patterns and immobilization, i.e., measures of tonic pain and depression in rats, in both genders. Buspirone decreased these measures in prenatally stressed rats in both tests as compared with values in prenatally stressed rats not exposed to buspirone. Buspirone was found to normalize measures of the tonic pain response modified by prenatal stress; the significant reductions in measures of the depression-like state suggest differences in the mechanisms of the antidepressant and antinociceptive effects of buspirone.     

Altered sensitivity to NMDA following developmental lead exposure in rats.

Early Pb exposure is known to disrupt the development of the hippocampus and result in deficits in learning and memory capacities and altered seizure susceptibility. The excitatory amino acid, NMDA, is found in high concentrations in the hippocampus and has been implicated in learning and memory functions and seizure activity. Rat pups nursed mothers exposed to high (4%), moderate (0.4%), or low (0.05%) levels of PbCO3 in their diet, or a Na2CO3 control diet from postnatal day 1 (P1) to P25. Rat pups were injected with varying doses of NMDA on P15 or P25. Control animals showed a characteristic slowly developing response to NMDA, usually including tail twitches and wet dog shakes at approximately 10 and 40 mg/kg at P15 and P25, respectively, with status epilepticus and death occurring at 40 and 80 mg/kg. Lead-exposed animals displayed an altered sensitivity to NMDA, with high and medium Pb animals showing the onset of behavioral signs and death at lower NMDA doses, the degree of which being dependent on the level of Pb exposure. Low Pb-exposed animals showed a more variable and attenuated response to NMDA. The data are discussed in terms of the possible mechanisms of Pb neurotoxicity.     

Developmental thermoregulatory deficits in prenatal ethanol exposed long- and short-sleep mice.

Sensitivity to alcohol may influence the severity of prenatal alcohol effects. To examine this hypothesis, the ontogeny of thermoregulation was measured in prenatal ethanol exposed offspring of mice selected for differences in alcohol sensitivity. Pregnant long-sleep (LS) and short-sleep (SS) mice were exposed to 3 or 4 g/kg ethanol or an isocaloric amount of maltose-dextrin twice per day from day 7 through 18 of pregnancy. Doses were given six hours apart via gavage. Nonintubated lab chow controls were included for both genotypes. Offspring were fostered at birth to lactating mice of an outbred strain. Offspring temperatures were measured at 0, 60, and 120 min away from the nest on alternating days from 7 through 21 days of age. LS and SS offspring prenatally exposed to the high ethanol dose showed lower temperatures at the 60 and 120 min time points on each day of testing compared to all other treatment groups. Temperatures of offspring prenatally exposed to the low ethanol dose did not differ from controls. These results suggest a relatively steep dose-response curve for thermoregulatory deficits in LS and SS offspring prenatally exposed to alcohol. Genetically-based alcohol sensitivity did not influence the effects of prenatal alcohol exposure on this response.     

Daily,limited access to methamphetamine self-administration during pregnancy leads to increased methamphetamine sensitivity in adult offspring

Methamphetamine use by women, even throughout pregnancy, is common. But there is limited knowledge about the effects in prenatally methamphetamine-exposed children. This study investigated how prenatal methamphetamine exposure in rats, via maternal i.v. self-administration, affected the sensitivity of adult offspring to methamphetamine in comparison with controls. The offspring were generated from dams either self-administering methamphetamine daily under limited-access conditions prior to and throughout pregnancy, or their respective saline-yoked control dams. Spontaneous and methamphetamine-induced locomotor activity was assessed in male and female offspring of both exposure groups after a range of methamphetamine doses. In a separate group of offspring, acquisition of i.v. methamphetamine self-administration, responding under fixed and progressive ratio schedules of methamphetamine reinforcement, and reinstatement of extinguished drug-seeking behavior were assessed. Methamphetamine dose-dependently increased locomotor activity in both exposure groups. However, methamphetamine-exposed males showed significantly enhanced locomotor activity compared with controls at 1 mg/kg, and methamphetamine-exposed females showed significantly enhanced locomotor activity compared with controls at 3.2 mg/kg. Methamphetamine-exposed offspring of both sexes acquired methamphetamine self-administration faster and showed overall higher levels of methamphetamine-induced reinstatement compared with controls. Taken together, these results indicate that prenatal methamphetamine exposure to relatively low levels alters methamphetamine sensitivity in male and female adult offspring.     

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 mineralcorticoid receptor expression between groups.