Maternal neglect with reduced depressive-like behavior and blunted c-fos activation in Brattleboro mothers, the role of central vasopressin

Early mother-infant relationships exert important long-term effects in offspring and are disturbed by factors such as postpartum depression. We aimed to clarify if lack of vasopressin influences maternal behavior paralleled by the development of a depressive-like phenotype. We compared vasopressin-deficient Brattleboro mothers with heterozygous and homozygous normal ones. The following parameters were measured: maternal behavior (undisturbed and separation-induced); anxiety by the elevated plus maze; sucrose and saccharin preference and forced swim behavior. Underlying brain areas were examined by c-fos immunocytochemistry among rest and after swim-stress. In another group of rats, vasopressin 2 receptor agonist was used peripherally to exclude secondary changes due to diabetes insipidus. Results showed that vasopressin-deficient rats spend less time licking-grooming their pups through a centrally driven mechanism. There was no difference between genotypes during the pup retrieval test. Vasopressin-deficient mothers tended to explore more the open arms of the plus maze, showed more preference for sucrose and saccharin and struggled more in the forced swim test, suggesting that they act as less depressive. Under basal conditions, vasopressin-deficient mothers had more c-fos expression in the medial preoptic area, shell of nucleus accumbens, paraventricular nucleus of the hypothalamus and amygdala, but not in other structures. In these areas the swim-stress-induced activation was smaller. In conclusion, vasopressin-deficiency resulted in maternal neglect due to a central effect and was protective against depressive-like behavior probably as a consequence of reduced activation of some stress-related brain structures. The conflicting behavioral data underscores the need for more sex specific studies.

Adolescent pre-exposure to ethanol and 3,4-methylenedioxymethylamphetamine (MDMA) increases conditioned rewarding effects of MDMA and drug-induced reinstatement

Many adolescents often take ethanol (EtOH) in combination with 3,4-methylenedioxymethylamphetamine (MDMA). In the present work, we used a mouse model to study the effect of repeated pre-exposure during adolescence to EtOH (2 g/kg), MDMA (10 or 20 mg/kg) or EtOH + MDMA on the rewarding and reinstating effects of MDMA in the conditioned place preference (CPP) paradigm. Pre-exposure to EtOH, MDMA or both increased the rewarding effects of a low dose of MDMA (1.25 mg/kg). These pre-treatments did not affect the acquisition of the CPP induced by 5 mg/kg of MDMA. However, the CPP was more persistent in mice pre-exposed to both doses of MDMA or to EtOH + MDMA20. After extinction of the CPP induced by 5 mg/kg of MDMA, reinstatement was observed in all groups with a priming dose of 2.5 mg/kg of MDMA, in the groups pre-exposed to EtOH or MDMA alone with a priming dose of 1.25 mg/kg, and in the groups pre-treated with MDMA alone with a priming dose of 0.625 mg/kg. Pre-treatment during adolescence with MDMA or EtOH induced long-term changes in the level of biogenic amines [dihydroxyphenyl acetic acid, homovanillic acid, dopamine turnover, serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in the striatum, and 5-HT and 5-HIAA in the cortex] after the first reinstatement test, although these effects depended on the dose used during conditioning. These results suggest that exposure to EtOH and MDMA during adolescence reinforces the addictive properties of MDMA.

Chronic cocaine self-administration modulates ERK1/2 and CREB responses to dopamine receptor agonists in striatal slices

Cocaine abuse leads to adaptations in brain reward circuits, where dopaminergic neurotransmission is a fundamental component. We hypothesized that chronic cocaine self-administration could influence dopamine D1 and D2 receptor activation of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) and cyclic adenosine monophosphate response element-binding protein (CREB) phosphorylation. Male Sprague Dawley rats were exposed to cocaine self-administration for 6-11 weeks. Brains from sham controls and cocaine rats were extracted 1 day after the last session, and slices obtained from the striatum and nucleus accumbens (NAc) were incubated in vitro with or without the D1R agonist SKF38393 or the D2R agonist quinpirole. We found that cocaine self-administration led to a reduction in the capacity of D1R to activate ERK1/2 phosphorylation as compared with control rats. Cocaine self-administration also reduced D1R agonist-induced CREB phosphorylation in striatal slices, suggesting a downregulation of D1R signaling. D2R-induced ERK1/2 phosphorylation appeared blunted in striatal slices from cocaine rats. In contrast, surprisingly, cocaine self-administration strongly potentiated D2R agonist-induced CREB phosphorylation selectively in the NAc portion of the slices. Altered agonist-induced signaling was independent of total ERK1/2 and CREB expression. Our finding that selected cellular D2R responses to CREB were strengthened by cocaine self-administration could be relevant to understand how dopaminergic receptors participate in cocaine-induced behaviors.

Adrenocortical and behavioural response to chronic restraint stress in neurokinin-1 receptor knockout mice

Brain substance P and its receptor (neurokinin-1, NK1) have a widespread brain distribution and are involved in an important number of behavioural and physiological responses to emotional stimuli. However, the role of NK1 receptors in the consequences of exposure to chronic stress has not been explored. The present study focused on the role of these receptors in the hypothalamic-pituitary-adrenal (HPA) response to daily repeated restraint stress (evaluated by plasma corticosterone levels), as well as on the effect of this procedure on anxiety-like behaviour, spatial learning and memory in the Morris water maze (MWM), a hippocampus-dependent task. Adult null mutant NK1-/- mice, with a C57BL/6J background, and the corresponding wild-type mice showed similar resting corticosterone levels and, also, did not differ in corticosterone response to a first restraint. Nevertheless, adaptation to the repeated stressor was faster in NK1-/- mice. Chronic restraint modestly increased anxiety-like behaviour in the light-dark test, irrespective of genotype. Throughout the days of the MWM trials, NK1-/- mice showed a similar learning rate to that of wild-type mice, but had lower levels of thigmotaxis and showed a better retention in the probe trial. Chronic restraint stress did not affect these variables in either genotype. These results indicate that deletion of the NK1 receptor does not alter behavioural susceptibility to chronic repeated stress in mice, but accelerates adaptation of the HPA axis. In addition, deletion may result in lower levels of thigmotaxis and improved short-term spatial memory, perhaps reflecting a better learning strategy in the MWM.

Sex-dependent effects of maternal deprivation and adolescent cannabinoid treatment on adult rat behaviour

Early life experiences such as maternal deprivation (MD) exert long-lasting changes in adult behaviour and reactivity to stressors. Adolescent exposure to cannabinoids is a predisposing factor in developing certain psychiatric disorders. Therefore, the combination of the two factors could exacerbate the negative consequences of each factor when evaluated at adulthood. The objective of this study was to investigate the long-term effects of early MD [24 hours at postnatal day (PND) 9] and/or an adolescent chronic treatment with the cannabinoid agonist CP-55,940 (0.4 mg/kg, PND 28-42) on diverse behavioural and physiological responses of adult male and female Wistar rats. We tested them in the prepulse inhibition (PPI) of the startle response and analysed their exploratory activity (holeboard) and anxiety (elevated plus maze, EPM). In addition, we evaluated their adrenocortical reactivity in response to stress and plasma leptin levels. Maternal behaviour was measured before and after deprivation. MD induced a transient increase of maternal behaviour on reuniting. In adulthood, maternally deprived males showed anxiolytic-like behaviour (or increased risk-taking behaviour) in the EPM. Adolescent exposure to the cannabinoid agonist induced an impairment of the PPI in females and increased adrenocortical responsiveness to the PPI test in males. Both, MD and adolescent cannabinoid exposure also induced sex-dependent changes in plasma leptin levels and body weights. The present results indicate that early MD and adolescent cannabinoid exposure exerted distinct sex-dependent long-term behavioural and physiological modifications that could predispose to the development of certain neuropsychiatric disorders, though no synergistic effects were found.

Behavioral and endocrine consequences of simultaneous exposure to two different stressors in rats: interaction or independence?

Although behavioral and endocrine consequences of acute exposure to stressors have been extensively studied, little is known about how simultaneous exposure to two different stressors interacts to induce short- and long-term effects. In the present experiment we studied this interaction in adult male rats exposed to cat fur odor (impregnated cloth) or immobilization on boards either separately or simultaneously. We reasoned that exposure to the odor of a potential predator while immobilized, may potentiate its negative consequences as compared to exposure to only one of the stressors. Exposure to cat odor elicited the expected reduction of activity and avoidance of the area where the impregnated cloth was located. The endocrine response (plasma levels of ACTH and corticosterone, as a measure of the hypothalamic-pituitary-adrenal axis, HPA) was markedly greater after immobilization than after cat fur odor and no additive effects were found by simultaneous exposure to both stressors. Cat odor, but not immobilization, increased anxiety-like behavior as evaluated in the elevated plus-maze 7 days after the stressors, with no evidence of enhanced HPA activation. In addition, cat odor exposure resulted in long-lasting (8 days later) fear conditioning to the box containing a clean cloth, which was reflected by hypoactivity, avoidance of the cloth area and enhanced HPA activation. All these effects were similarly observed in rats exposed simultaneously to cat odor and immobilization. In rats only exposed to immobilization, only some weak behavioral signs of fear conditioning were found, but HPA activation in response to the context paired to immobilization was enhanced to the same extent as in cat odor-exposed animals, supporting a certain degree of endocrine conditioning. The present results did not reveal important behavioral interactions between the two stressors when animals experienced both simultaneously, whereas some interactions were found regarding HPA activation. Theoretical implications are discussed.

Adaptation of the hypothalamic-pituitary-adrenal axis and glucose to repeated immobilization or restraint stress is not influenced by associative signals

Repeated exposure to the same stressor very often results in a reduction of some prototypical stress responses, namely those related to the hypothalamic-pituitary-adrenal (HPA) and sympatho-medullo-adrenal (SMA) axes. This reduced response to repeated exposure to the same (homotypic) stressor (adaptation) is usually considered as a habituation-like process, and therefore, a non-associative type of learning. However, there is some evidence that contextual cues and therefore associative processes could contribute to adaptation. In the present study we demonstrated in two experiments using adult male rats that repeated daily exposure to restraint (REST) or immobilization on boards (IMO) reduced the HPA (plasma levels of ACTH and corticosterone) and glucose responses to the homotypic stressor and such reduced responses remained intact when all putative cues associated to the procedure (experimenter, way of transporting to the stress room, stress boxes, stress room and colour of the restrainer in the case of REST) were modified on the next day. Therefore, the present results do not favour the view that adaptation after repeated exposure to a stressor may involve associative processes related to signals predicting the imminence of the stressors, but more studies are needed on this issue.

A single footshock causes long-lasting hypoactivity in unknown environments that is dependent on the development of contextual fear conditioning

Exposure to a single session of footshocks induces long-lasting inhibition of activity in unknown environments that markedly differ from the shock context. Interestingly, these effects are not necessarily associated to an enhanced anxiety and interpretation of this hypoactivity remains unclear. In the present experiment we further studied this phenomenon in male Sprague-Dawley rats. In a first experiment, a session of three shocks resulted in hypoactivity during exposure, 6-12days later, to three different unknown environments. This altered behaviour was not accompanied by a greater hypothalamic-pituitary-adrenal (HPA) activation, although greater HPA activation paralleling higher levels of freezing was observed in the shock context. In a second experiment we used a single shock and two procedures, one with pre-exposure to the context before the shock and another with immediate shock that did not induce contextual fear conditioning. Hypoactivity and a certain level of generalization of fear (freezing) to the unknown environments only appeared in the group that developed fear conditioning, but no evidence for enhanced anxiety in the elevated plus-maze was found in any group. The results suggest that if animals are able to associate an aversive experience with a distinct unknown environment, they would display more cautious behaviour in any unknown environment and such strategy persists despite repeated experience with different environments. This long-lasting cautious behaviour was not associated to greater HPA response to the unknown environment that was however observed in the shock context. The present findings raised some concerns about interpretation of long-lasting behavioural changes caused by brief stressors.

Bone Health in Postmenopausal Women Treated with Adjuvant Aromatase Inhibitors for Early Breast Cancer: 12 Months Follow-Up

Background:The use of aromatase inhibitors (AI) in the adjuvant setting for postmenopausal women with receptor-positive breast cancer is well established. The AI treatment has been associated with decline in bone mineral density (BMD), and increased bone turnover markers. We designed a prospective study to evaluate the effect of oral bisphosphonates (BP) on vertebral and non vertebral fractures (VF), bone turnover markers (bTM), BMD, and quality of life (QoL) in postmenopausal women receiving adjuvant AI for hormone receptor positive early breast cancer.Material and methods:Postmenopausal, receptor-positive breast cancer women treated with AI as initial therapy [Letrozol (LET)] or after 2 or 5 years of tamoxifen [switched to exemestane (EXE)] were included. Patients were stratified by lumbar spine, femoral neck and total hip BMD to receive open-label treatment with BP, alendronate or risedronate, (if osteoporosis [T-score<-2,5] or osteopenia [T-score<-2.0] and 1 major risk factor, defined as group of high risk of fracture) or calcium and vitamin D supplementation (if normal BMD or T-score>-2.0 and no major risk factor). Levels of 25-OH vitamin D, N-telopeptide (NTx), bone alkaline phosphatase (bALP) and osteocalcin (OC) were measured at baseline, 3, 12 and 24 moths, and BMD and thoracic and lumbar spine X-rays were assesed at baseline, 1 and 2 years. QoL was evaluated by ECOS-16 questionnaire and a visual analogue scale used to evaluate arthralgia. Results:from 03/2006 to 03/2009, 261 patients have been included and 117 have completed >12 month follow up. All the bTM increased after 12 months of AI treatment and a significant decrease on BMD was also observed (Table 1). This effect is reverted with oral BP treatment, maintaining the BMD level and reducing the bTM. With the AI introduction QoL of patients became worse, and the BP treatment did not improve neither arthralgia nor bone pain. Osteoporotic fractures were recorded at baseline in 12.3% of women (4.2% VF and 7.7% non VF).Conclusions:AI treatment increased bone turnover, decreased BMD and QoL. Of note, BP use decreased bone turnover, has neutral effect in BMD and does not improve QoL. This study suggests that the current recommendation of the use of BP should be revisited to consider including all postmenopausal women treated with adjuvant AI to avoid increased bone turnover and bone mass decrease.Table 1. BMD at baseline, 12 months and changes  Without BP (n=76)  With BP (n=41)  BMD value (g/cm2)AIBasal12 month% change / pBasal12 month% change / pFemoral NeckLET0.7650.751- 1.96 / 0.020.6480.657+ 1.61 / NS EXE0.7560.749- 0.6 / NS0.6260.644+ 2.63 / 0.013Lumbar spineLET0.9900.969- 2.36 / 0.00010.8150.813- 0.17 / NS EXE0.9570.940- 1.57 / 0.0430.8110.814+ 0.86 / NS 

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3175.

Do odors from different cats induce equivalent unconditioned and conditioned responses in rats?

Since cats are predators of rats and mice, interest in the consequences of exposure to cat-associated odors has increased in the last decade, particularly regarding the development of putative animal models of post-traumatic stress disorder (PTSD). Although in the literature there are some comments on the variability of the effects depending on the individual cat used, there are no reports on this subject. In the present study, we demonstrated, using male Sprague-Dawley rats and cloths impregnated with fur/skin odors from three different cats (one ovariectomized female and two intact males), that the unconditioned endocrine (release of corticosterone) and behavioral (inhibition of activity and avoidance of the cloth area) responses to the presence of the cat odors were statistically significant and similar among the three cats. The conditioned behavioral response to a clean cloth, studied 7 days after the initial exposure to odors, was also evident with the three cats, with minor differences among them. In contrast, only the fur odor from one of the male cats clearly increased anxiety-like behavior in the elevated plus-maze 6 days later. These data indicate that: (i) evaluation of unconditioned and conditioned responses to cat odors does not appear to strongly predict long-lasting increases in anxiety-like behavior; and, therefore, both types of responses are partially dissociated; and (ii) differences among cats mainly affected the induction of long-lasting changes in anxiety-like behavior. The ultimate reasons for these differences are not known, but their characterization is critical for a proper understanding of putative PTSD models.

Cat odor causes long-lasting contextual fear conditioning and increased pituitary-adrenal activation, without modifying anxiety

A single exposure to a cat or cat odors has been reported by some groups to induce contextual and auditory fear conditioning and long-lasting changes in anxiety-like behaviour, but there is no evidence for parallel changes in biological stress markers. In the present study we demonstrated in male rats that exposure to a novel environment containing a cloth impregnated with cat fur odor resulted in avoidance of the odor, lower levels of activity and higher pituitary-adrenal (PA) response as compared to those exposed to the novel environment containing a clean cloth, suggesting increased levels of stress in the former animals. When re-exposed 9 days later to the same environment with a clean cloth, previously cat fur exposed rats again showed avoidance of the cloth area and lower levels of activity, suggesting development of contextual fear conditioning, which again was associated with a higher PA activation. In contrast, unaltered both anxiety-like behaviour and PA responsiveness to an elevated plus-maze were found 7 days after cat odor exposure. It is concluded that: (i) PA activation is able to reflect both the stressful properties of cat fur odor and odor-induced contextual fear conditioning; (ii) development of cat odor-induced contextual fear conditioning is independent of the induction of long-lasting changes in anxiety-like behaviour; and (iii) greater PA activation during exposure to the odor context is not explained by non-specific sensitization of the PA axis caused by previous exposure to cat fur odor.

The predictive and prognostic value of serum CA 125 kinetics and CA 125 nadir during paclitaxel/platinum based chemotherapy in patients with advanced ovarian carcinoma

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Background: The tumor marker CA 125 is an accurate and reliable marker for monitoring the response to treatment and detecting early relapse in epithelial ovarian cancer (EOC). The aim of this retrospective study is to analyze the predictive and prognostic value of CA 125 kinetics and the implications of the different levels of CA 125 within the normal range after chemotherapy (CT). Methods: Between 1996 and 2008, 127 patients (pts) were treated with standard CT regimen for FIGO stage IIb-IV EOC. Median age was 64 years (24–87). Tumors were classified: 70 (55%) serous, 24 (19%) poorly differentiated, 14 (11%) endometrioid and 19 (15%) clear cell carcinoma. FIGO stage: 12 (9%) II; 95 (75%) III; and 20 (16%) IV. Tumor grade: 1 (1%) G1; 11 (9%) G2; and 115 (90%) G3. Residual disease after initial surgery: 52 (41%) optimal <2cm and 39 (31%) suboptimal. After surgery, 117 (92%) of the pts received a median of 6 cycles/patient with platinum based (cisplatin or carboplatin) CT in combination with paclitaxel. Median follow-up was 31 months. 93 (73%) pts achieved levels <35 U/ml after CT. Survival analyses for disease-free survival (DFS) and overall survival (OS) used univariate (Kaplan-Meier) and multivariate (Cox) model. Results: For 127 stage IIb-IV pts, 88 (69%) relapsed and 60 (47%) died from EOC. The median DFS for 3 groups 1, 2 and 3, was 34, 20, 14 months, respectively (p < 0.0001). The median OS for 3 groups was 7.5, 3 and 3 years, respectively (p < 0.0001). Pre-CT Ca 125 (p < 0.002), and time to negativization (p < 0.043) all had a univariate prognostic value for DFS and OS. In Cox models, FIGO stage (p < 0.0001) and nadir concentration (p < 0.0001) were the most powerful prognostic factors for DFS and OS. We found no differences in DFS and OS related to time to nadir. Conclusions: Serum CA 125 kinetics during early CT has a strong predictive and prognostic relevance for patients with advanced EOC. Within normal range, the differences between CA 125 levels could add prognostic information, stratify pts according to the risk of progression and would be a useful tool when performing consolidation CT in future clinical trials.

No significant financial relationships to disclose.

Exposure to severe stressors causes long-lasting dysregulation of resting and stress-induced activation of the hypothalamic-pituitary-adrenal axis

Exposure to some predominantly emotional (electric shock) and systemic (interleukin-1beta) stressors has been found to induce long-term sensitization of the hypothalamic-pituitary-adrenal (HPA) responsiveness to further superimposed stressors. Since exposure to immobilization on wooden boards (IMO) is a severe stressor and may have interest regarding putative animal models of post-traumatic stress disorders (PTSD), we have characterized long-lasting effects of a single exposure to IMO and other stressors on the HPA response to the same (homotypic) and to novel (heterotypic) stressors and the putative mechanisms involved. A single exposure to IMO caused a long-lasting reduction of peripheral and central responses of the HPA axis, likely to be mediated by some brain areas, such as the lateral septum and the medial amygdala. This desensitization is not explained by changes in negative glucocorticoid feedback, and, surprisingly, it is positively related to the intensity of the stressors. In contrast, the HPA response to heterotypic stressors (novel environments) was enhanced, with maximal sensitization on the day after IMO. Sensitization progressively vanished over the course of 1-2 weeks and was not modulated by IMO-induced corticosterone release. Moreover, it could not be explained by changes in the sensitivity of the HPA axis to fast or intermediate/delayed negative feedback, as evaluated 1 week after exposure to IMO, using shock as the heterotypic stressor. Long-lasting stress-induced behavioral changes reminiscent of enhanced anxiety and HPA sensitization are likely to be parallel but partially independent phenomena, the former being apparently not related to the intensity of stressors.

A single exposure to immobilization causes long-lasting pituitary-adrenal and behavioral sensitization to mild stressors

We have previously reported that a single exposure to immobilization (IMO) in rats causes a long-term desensitization of the hypothalamic-pituitary-adrenal (HPA) response to the same (homotypic) stressor. Since there are reports showing that a single exposure to other stressors causes sensitization of the HPA response to heterotypic stressors and increases anxiety-like behavior, we studied in the present work the long-term effects of IMO on behavioral and HPA response to mild superimposed stressors. In Experiments 1 and 2, adult male Sprague-Dawley rats were subjected to 2 h of IMO and then exposed for 5 min to the elevated plus-maze (EPM) at 1, 3 or 7 days after IMO. Blood samples were taken at 15 min after initial exposure to the EPM. Increases in anxiety-like behavior and HPA responsiveness to the EPM were found at all times post-IMO. Changes in the resting levels of HPA hormones did not explain the enhanced HPA responsiveness to the EPM (Experiment 3). In Experiments 4 and 5, we studied the effects of a single exposure to a shorter session of IMO (1 h) on behavioral and HPA responses to a brief and mild session of foot-shocks done 10 days after IMO. Neither previous IMO nor exposure to shocks in control rats modified behavior in the EPM. However, a brief session of shocks in previously IMO-exposed rats dramatically increased anxiety in the EPM. HPA and freezing responses to shocks were similar in control and previous IMO groups. Therefore, a single exposure to IMO appears to induce long-lasting HPA and behavioral sensitization to mild superimposed stressors, although the two responses are likely to be at least partially independent. Long-term effects of IMO on the susceptibility to stress-induced endocrine and emotional disturbances may be relevant to the characterization of animal models of post-traumatic stress.

Characterization of central and peripheral components of the hypothalamus-pituitary-adrenal axis in the inbred Roman rat strains

Several studies performed in outbred Roman high- and low-avoidance lines (RHA and RLA, respectively) have demonstrated that the more anxious line (RLA) is characterized by a higher hypothalamic-pituitary-adrenal (HPA) response to certain stressors than the less anxious one (RHA). However, inconsistent results have also been reported. Taking advantage of the generation of an inbred colony of RLA and RHA rats (RHA-I and RLA-I, respectively), we have characterized in the two strains not only resting and stress levels of peripheral HPA hormones but also central components of the HPA axis, including CRF gene expression in extra-hypothalamic areas. Whereas resting levels of ACTH and corticosterone did not differ between the strains, a greater response to a novel environment was found in RLA-I as compared to RHA-I rats. RLA-I rats showed enhanced CRF gene expression in the paraventricular nucleus (PVN) of the hypothalamus, with normal arginin-vasopressin gene expression in both parvocellular and magnocellular regions of the PVN. This enhanced CRF gene expression is not apparently related to altered negative corticosteroid feedback as similar levels of expression of brain glucorticoid and mineralocorticoid receptors were found in the two rat strains. CRF gene expression tended to be higher in the central amygdala and it was significantly higher in the dorsal region of the bed nucleus of stria terminalis (BNST) of RLA-I rats, while no differences appeared in the ventral region of BNST. Considering the involvement of CRF and the BNST in anxiety and stress-related behavioral alterations, the present data suggest that the CRF system may be a critical neurobiological substrate underlying differences between the two rat strains.

Long-term neuroendocrine and behavioural effects of a single exposure to stress in adult animals

There is now considerable evidence for long-lasting sequels of stress. A single exposure to high intensity predominantly emotional stressors such as immobilisation in wooden-boards (IMO) induces long-term (days to weeks) desensitization of the hypothalamic-pituitary-adrenal (HPA) response to the same (homotypic) stressor, whereas the response to novel (heterotypic) stressors was enhanced. In addition, long-lasting changes in behaviour have been described after a single exposure to brief or more prolonged sessions of shocks, predator, predator odour, underwater stress or a combination of three stressors on 1 day. The most consistent changes are reduced entries into the open arms of the elevated plus-maze and enhanced acoustic startle response, both reflecting enhanced anxiety. However, it is unclear whether there is any relationship between the intensity of the stressors, as evaluated by the main physiological indexes of stress (e.g. HPA axis), the putative traumatic experience they represent and their long-term behavioural consequences. This is particularly critical when trying to model post-traumatic stress disorders (PTSD), which demands a great effort to validate such putative models.

Litter size affects emotionality in adult male rats

The role of natural variations in pre-weaning litter size in rodent adult emotionality and the importance of maternal care as a possible mediating factor have been frequently neglected. To address these issues, maternal behaviour of Sprague-Dawley dams differing in natural number of pups was studied for the first seven postnatal days. Later, adult behaviour of representative male offspring was studied in the elevated plus-maze, the circular corridor, the dark-light box and the forced swimming test. Three groups of offspring were selected in function of the number of littermates: L<10 group (less than 10 pups per dam), L10-15 (between 10 and 15 pups per dam) and L>15 group (more than 15 pups per dam). L<10 litters showed a reduced habituation of activity across time in a circular corridor and as compared to L>15 litters, L<10 litters showed a lower activity during the first 5 min of exposure to the circular corridor. L<10 litters had also higher signs of anxiety in the elevated plus-maze, in comparison to the other two groups. In addition, L<10 litters showed in the forced swimming test reduced struggling and more mild swimming behavior than the other two groups. These abnormalities in L<10 litters are not explained by maternal behavior since they received individually more maternal care than L>15, as assessed by total licking-grooming observed during the whole observation period divided by number of pups. Although previous data from several laboratories have demonstrated that low maternal care is associated with heightened emotionality at adulthood, the present results suggest an important contribution of spontaneous litter size to adult emotional behavior that cannot be explained by concomitant changes in maternal care.

Differential effects of stress and amphetamine administration on Fos-like protein expression in corticotropin releasing factor-neurons of the rat brain

Corticotropin releasing factor (CRF) appears to be critical for the control of important aspects of the behavioral and physiological response to stressors and drugs of abuse. However, the extent to which the different brain CRF neuronal populations are similarly activated after stress and drug administration is not known. We then studied, using double immunohistochemistry for CRF and Fos protein, stress and amphetamine-induced activation of CRF neurons in cortex, central amygdala (CeA), medial parvocellular dorsal, and submagnocellular parvocellular regions of the paraventricular nucleus of the hypothalamus (PVNmpd and PVNsm, respectively) and Barrington nucleus (Bar). Neither exposure to a novel environment (hole-board, HB) nor immobilization (IMO) increased Fos-like immunoreactivity (FLI) in the CeA, but they did to the same extent in cortical regions. In other regions only IMO increased FLI. HB and IMO both failed to activate CRF+ neurons in cortical areas, but after IMO, some neurons expressing FLI in the PVNsm and most of them in the PVNmpd and Bar were CRF+. Amphetamine administration increased FLI in cortical areas and CeA (with some CRF+ neurons expressing FLI), whereas the number of CRF+ neurons increased only in the PVNsm, in contrast to the effects of IMO. The present results indicate that stress and amphetamine elicited a distinct pattern of brain Fos-like protein expression and differentially activated some of the brain CRF neuronal populations, despite similar levels of overall FLI in the case of IMO and amphetamine.

Microtubule-regulatory phosphoproteins and NER system are involved in platinum and paclitaxel-based chemotherapy resistance in ovarian cancer

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Background: The treatment of ovarian cancer is hindered by intrinsic resistance to platinum and paclitaxel-based chemotherapy (CT). Nucleotide excision repair system plays a central role in DNA repair and is related with resistance to platinum compounds. Excision repair cross-complementation 1 (ERCC1) and 3 (ERCC3) genes confer a differential sensitivity to CT. OP18/stathmin and mDIA are involved in regulation of microtubules dynamics and may represent a mechanism of resistance to paclitaxel. Both mechanisms have been recently investigated in ovarian cancer (OC). Methods: Formalin and paraffin-embedded tissues obtained from 33 patients with advanced OC were retrospectively collected to investigate ERCC1, ERCC3, OP18, and mDIA mRNA levels by quantitative RT- PCR. All patients received a median of 6 cycles platinum based CT in combination with taxanes. Median age was 62 years. Tumors were classified: 52% serous, 9% endometrioid, 27% clear cell, and 12% poorly differentiated carcinomas. FIGO stage: 4 (12%) stage II, 19 (58%) stage III, and 10 (30%) stage IV. 12 chemoresistant tumors (time to recurrence (TTR) < 6 months) and 21 chemosensitive tumors (TTR = 6 months) were analyzed. Median follow-up was 31 months. Results: An increase in mRNA levels was consistently observed in the chemoresistent group: 1.9-fold increased in ERCC1 and 1.6-fold increased in ERCC3. Both genes exhibited comparable expression levels. Statistically significant differences on ERCC1 and ERCC3 mRNA levels were encountered when chemoresistant and chemosensitive tumors were compared (p=0.01 and p= 0.03, respectively). Statistically differences on OP18 mRNA levels were found when chemoresistant and chemosensitive tumors were compared (p=0.05). No differences in mDIA mRNA levels were encountered. Conclusions: Our results suggest that determination of ERCC1-ERCC3 before chemotherapy is potentially useful to predict the effectiveness of platinum-based therapy. Microtubule drug resistance in OC may be associated with altered OP18/stathmin expression. Novel treatment approaches based on molecular markers could be useful predictors of response and could identify targets for therapeutic strategies. Further studies are required.

No significant financial relationships to disclose.

Environmental enrichment effects in social investigation in rats are gender dependent

Environmental enrichment (E) can change neuronal structure, improves learning in various tasks and increases cerebral plasticity. However, no E effects were found in a test measuring social olfactory discrimination memory and, although they have been mainly measured in males, gender differences have been reported in other tests. The aims of the present study were to evaluate gender differential effects of E in the social discrimination paradigm which also involves social olfactory discrimination and in the elevated plus-maze test (EPM) for measuring anxiety. E procedure consisted of a combination of social and physical factors; groups of 11-12 Sprague-Dawley rats were separated by sex in large cages with physical stimulus for a period of 8 weeks starting immediately after weaning. Differential gender E effects appeared in the social exploratory patterns: enriched males showed increased exploratory behaviour towards juvenile rats in comparison to control males, whereas no differences were found in females. No effects of E in social discrimination memory were observed. In the EPM, both enriched male and female rats showed less anxious behaviour than non-enriched animals.