Safety and clinical activity of vascular endothelial growth factor receptor (VEGFR)-tyrosine kinase inhibitors after programmed cell death 1 inhibitor treatment in patients with metastatic clear cell renal cell carcinoma

BACKGROUND

Emerging agents blocking the programmed cell death 1 (PD-1) pathway show activity in metastatic clear cell renal cell carcinoma (mRCC). The aim of this study was to evaluate the efficacy and safety of vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR)-tyrosine kinase inhibitor (TKI) therapy after PD-1 inhibition.

PATIENTS AND METHODS

Patients with mRCC treated with anti-PD-1 antibody (aPD-1) monotherapy or in combination (with VEGFR-TKI or ipilimumab) that subsequently received VEGFR-TKI were retrospectively reviewed. The efficacy end points were objective response rate (ORR) and progression-free survival (PFS) stratified by the type of prior PD-1 regimen. Safety by the type and PD-1 exposure was also evaluated.

RESULTS

Seventy patients were included. Forty-nine patients received prior therapy with immune checkpoint inhibitors (CPIs) alone and 21 had combination therapy of aPD-1 and VEGFR-TKI. Overall, ORR to VEGFR-TKI after PD-1 inhibition was 28% (19/68) and the median PFS was 6.4 months (mo) (4.3-9.5). ORR to VEGFR-TKI after aPD-1 in combination with VEGFR-TKI was lower than that in patients treated with VEGFR-TKI after CPI alone (ORR 10% versus 36%, P = 0.039). In the multivariable analysis, patients treated with prior CPI alone were more likely to achieve an objective response than those treated with aPD-1 in combination with VEGFR-TKI (OR = 5.38; 95% CI 1.12-26.0, P = 0.03). There was a trend toward numerically longer median PFS in the VEGFR-TKI after the CPI alone group, 8.4 mo (3.2-12.4) compared with 5.5 mo (2.9-8.3) for those who had VEGFR-TKI after aPD-1 in combination with VEGFR-TKI (P = 0.15). The most common adverse events (AEs) were asthenia, hypertension, and diarrhea.

CONCLUSIONS

The efficacy and safety of VEGFR-TKIs after PD-1 inhibition were demonstrated in this retrospective study. The response rate was lower and the median progression-free survival was shorter in those patients who received prior PD-1 in combination with VEGFR-TKI. PD-1 exposure does not seem to significantly influence the safety of subsequent VEGFR-TKI treatment.

Maternal separation induces neuroinflammation and long-lasting emotional alterations in mice

Early life experiences play a key role in brain function and behaviour. Adverse events during childhood are therefore a risk factor for psychiatric disease during adulthood, such as mood disorders. Maternal separation is a validated mouse model for maternal neglect, producing negative early life experiences that result in subsequent emotional alteration. Mood disorders have been found to be associated with neurochemical changes and neurotransmitter deficits such as reduced availability of monoamines in discrete brain areas. Emotional alterations like depression result in reduced serotonin availability and enhanced kynurenine metabolism through the action of indoleamine 2, 3-dioxygenase in response to neuroinflammatory factors. This mechanism involves regulation of the neurotransmitter system by neuroinflammatory agents, linking mood regulation to neuroinmunological reactions. In this context, the aim of this study was to investigate the effects of maternal separation with early weaning on emotional behaviour in mice. We investigated neuroinflammatory responses and the state of the tryptophan-kynurenine metabolic pathway in discrete brain areas following maternal separation. We show that adverse events during early life increase risk of long-lasting emotional alterations during adolescence and adulthood. These emotional alterations are particularly severe in females. Behavioural impairments were associated with microglia activation and disturbed tryptophan-kynurenine metabolism in brain areas related to emotional control. This finding supports the preeminent role of neuroinflammation in emotional disorders.

The neuroendocrine response to stress under the effect of drugs: Negative synergy between amphetamine and stressors

There have been numerous studies into the interaction between stress and addictive drugs, yet few have specifically addressed how the organism responds to stress when under the influence of psychostimulants. Thus, we studied the effects of different acute stressors (immobilization, interleukin-1β and forced swimming) in young adult male rats simultaneously exposed to amphetamine (AMPH, 4 mg/kg SC), evaluating classic biological markers. AMPH administration itself augmented the plasma hypothalamic-pituitary-adrenal (HPA) hormones, adrenocorticotropin (ACTH) and corticosterone, without affecting plasma glucose levels. By contrast, this drug dampened the peripheral HPA axis, as well as the response of glucose to the three stressors. We also found that AMPH administration completely blocked the forced swim-induced expression of the corticotropin-releasing hormone (hnCRH) and it partially reduced c-fos expression in the paraventricular nucleus of the hypothalamus (PVN). Indeed, this negative synergy in the forced swim test could even be observed with a lower dose of AMPH (1mg/kg, SC), a dose that is usually received in self-administration experiments. In conclusion, when rats that receive AMPH are subjected to stress, a negative synergy occurs that dampens the prototypic peripheral physiological response to stress and activation of the PVN.

Histone Deacetylase Gene Expression Following Binge Alcohol Consumption in Rats and Humans

BACKGROUND

Alcohol binge drinking is one of the most common patterns of excessive alcohol use and recent data would suggest that histone deacetylases (HDACs) gene expression profiling could be useful as a biomarker for psychiatric disorders.

METHODS

This study aimed to characterize the gene expression patterns of Hdac 1-11 in samples of rat peripheral blood, liver, heart, prefrontal cortex, and amygdala following repeated binge alcohol consumption and to determine the parallelism of Hdac gene expression between rats and humans in peripheral blood. To accomplish this goal, we examined Hdac gene expression following 1, 4, or 8 alcohol binges (3 g/kg, orally) in the rat, in patients who were admitted to the hospital emergency department for acute alcohol intoxication, and in rats trained in daily operant alcohol self-administration.

RESULTS

We primarily found that acute alcohol binging reduced gene expression (Hdac1-10) in the peripheral blood of alcohol-naïve rats and that this effect was attenuated following repeated alcohol binges. There was also a reduction of Hdac gene expression in the liver (Hdac2,4,5), whereas there was increased expression in the heart (Hdac1,7,8) and amygdala (Hdac1,2,5). Additionally, increased blood alcohol concentrations were measured in rat blood at 1 to 4 hours following repeated alcohol binging, and the only group that developed hepatic steotosis (fatty liver) were those animals exposed to 8 alcohol binge events. Finally, both binge consumption of alcohol in humans and daily operant alcohol self-administration in rats increased Hdac gene expression in peripheral blood.

CONCLUSIONS

Our results suggest that increases in HDAC gene expression within the peripheral blood are associated with chronic alcohol consumption, whereas HDAC gene expression is reduced following initial exposure to alcohol.

Adaptation of the hypothalamus-pituitary-adrenal axis to daily repeated stress does not follow the rules of habituation: A new perspective

Repeated exposure to a wide range of stressors differing in nature and intensity results in a reduced response of prototypical stress markers (i.e. plasma levels of ACTH and adrenaline) after an acute challenge with the same (homotypic) stressor. This reduction has been considered to be a habituation-like phenomenon. However, direct experimental evidence for this assumption is scarce. In the present work we demonstrate in adult male rats that adaptation of the hypothalamus-pituitary-adrenal (HPA) axis to repeated stress does not follow some of the critical rules of habituation. Briefly, adaptation was stronger and faster with more severe stressors, maximally observed even with a single exposure to severe stressors, extremely long-lasting, negatively related to the interval between the exposures and positively related to the length of daily exposure. We offer a new theoretical view to explain adaptation to daily repeated stress.

Effects of topiramate on ethanol-cocaine interactions and DNA methyltransferase gene expression in the rat prefrontal cortex

BACKGROUND AND PURPOSE

Recent and ongoing clinical studies have indicated that topiramate (Topamax®) could be effective in treating ethanol or cocaine abuse. However, the effects of topiramate on the co-administration of ethanol and cocaine remain largely unknown.

EXPERIMENTAL APPROACH

We studied the effects of topiramate, in Wistar rats, on operant ethanol self-administration with the co-administration of cocaine (i.p.). The psychomotor effects of topiramate were examined before ethanol self-administration and cocaine exposure. Blood samples were collected to analyse ethanol and cocaine metabolism (blood ethanol levels and benzoylecgonine). Quantitative real-time PCR was used to characterize the gene expression in the prefrontal cortex.

KEY RESULTS

Topiramate prevented the cocaine-induced increased response to ethanol in a dose-dependent manner without causing any motor impairment by itself. This effect was observed when topiramate was administered before ethanol access, but not when topiramate was administered before the cocaine injection. Topiramate did not block cocaine-induced psychomotor stimulation. Topiramate reduced blood ethanol levels but did not affect cocaine metabolism. Ethanol increased the gene expression of DNA methyltransferases (Dnmt1 and Dnmt3a), the corepressor Dnmt1-associated protein 1 (Dmap1), and the RNA methyltransferase Trdmt1. These effects were prevented by topiramate or cocaine. Gene expression of histone deacetylase-2 and glutamate receptor kainate-1 were only increased by cocaine treatment. Topiramate and cocaine co-administration caused an up-regulation of dopamine (Drd1, Th) and opioid (Oprm1) receptor genes. Topiramate showed a tendency to alter episodic-like memory.

CONCLUSIONS AND IMPLICATIONS

Topiramate is an effective inhibitor of the cocaine-induced increase in operant ethanol self-administration.

Stress-induced sensitization: the hypothalamic-pituitary-adrenal axis and beyond

Exposure to certain acute and chronic stressors results in an immediate behavioral and physiological response to the situation followed by a period of days when cross-sensitization to further novel stressors is observed. Cross-sensitization affects to different behavioral and physiological systems, more particularly to the hypothalamus-pituitary-adrenal (HPA) axis. It appears that the nature of the initial (triggering) stressor plays a major role, HPA cross-sensitization being more widely observed with systemic or high-intensity emotional stressors. Less important appears to be the nature of the novel (challenging) stressor, although HPA cross-sensitization is better observed with short duration (5-15 min) challenging stressors. In some studies with acute immune stressors, HPA sensitization appears to develop over time (incubation), but most results indicate a strong initial sensitization that progressively declines over the days. Sensitization can affect other physiological system (i.e. plasma catecholamines, brain monoamines), but it is not a general phenomenon. When studied concurrently, behavioral sensitization appears to persist longer than that of the HPA axis, a finding of interest regarding long-term consequences of traumatic stress. In many cases, behavioral and physiological consequences of prior stress can only be observed following imposition of a new stressor, suggesting long-term latent effects of the initial exposure.

Sex differences in the long-lasting effects of a single exposure to immobilization stress in rats

In male rats, a single exposure to a severe stressor such as immobilization (IMO) results in marked activation of the HPA axis and reduction of body weight gain. In addition, the HPA response to the same (homotypic) stressor is reduced, whereas the response to a different (heterotypic) stressor is enhanced for days. Although sex differences in the responsiveness of the HPA axis have been described, there are few studies about the influence of sex on long-lasting effects of stress. Thus, we have compared the consequences of a single exposure to IMO in male and female rats. Females showed a similar ACTH response to the first IMO associated with higher corticosterone, but they were more resistant than males to stress-induced loss of body weight. Unstressed females showed higher resting levels of ACTH and corticosterone, but they did not show the increase in the resting levels of HPA hormones observed in males on the day after IMO. During exposure to a different stressor (open-field) two days after IMO, enhanced corticosterone response and hypoactivity was observed in males, but not in females. Finally, a second exposure to IMO 8 days after the first one resulted in a reduction of the HPA response and of the negative impact on body weight as compared to the first exposure, and this protective effect was greater in females. In sum, IMO-exposed females showed a greater reduction of the response to a second IMO and appear to be more resistant than males to some of the negative impacts of IMO.

Sex differences in the behavioural and hypothalamic-pituitary-adrenal response to contextual fear conditioning in rats

In recent years, special attention is being paid to sex differences in susceptibility to disease. In this regard, there is evidence that male rats present higher levels of both cued and contextual fear conditioning than females. However, little is known about the concomitant hypothalamic-pituitary-adrenal (HPA) axis response to those situations which are critical in emotional memories. Here, we studied the behavioural and HPA responses of male and female Wistar rats to context fear conditioning using electric footshock as the aversive stimulus. Fear-conditioned rats showed a much greater ACTH and corticosterone response than those merely exposed to the fear conditioning chamber without receiving shocks. Moreover, males presented higher levels of freezing whereas HPA axis response was greater in females. Accordingly, during the fear extinction tests, female rats consistently showed less freezing and higher extinction rate, but greater HPA activation than males. Exposure to an open-field resulted in lower activity/exploration in fear-conditioned males, but not in females, suggesting greater conditioned cognitive generalization in males than females. It can be concluded that important sex differences in fear conditioning are observed in both freezing and HPA activation, but the two sets of variables are affected in the opposite direction: enhanced behavioural impact in males, but enhanced HPA responsiveness in females. Thus, the role of sex differences on fear-related stimuli may depend on the variables chosen to evaluate it, the greater responsiveness of the HPA axis in females perhaps being an important factor to be further explored.

Behavioral and neuroendocrine consequences of juvenile stress combined with adult immobilization in male rats

Exposure to stress during childhood and adolescence increases vulnerability to developing several psychopathologies in adulthood and alters the activity of the hypothalamic-pituitary-adrenal (HPA) axis, the prototypical stress system. Rodent models of juvenile stress appear to support this hypothesis because juvenile stress can result in reduced activity/exploration and enhanced anxiety, although results are not always consistent. Moreover, an in-depth characterization of changes in the HPA axis is lacking. In the present study, the long-lasting effects of juvenile stress on adult behavior and HPA function were evaluated in male rats. The juvenile stress consisted of a combination of stressors (cat odor, forced swim and footshock) during postnatal days 23-28. Juvenile stress reduced the maximum amplitude of the adrenocorticotropic hormone (ACTH) levels (reduced peak at lights off), without affecting the circadian corticosterone rhythm, but other aspects of the HPA function (negative glucocorticoid feedback, responsiveness to further stressors and brain gene expression of corticotrophin-releasing hormone and corticosteroid receptors) remained unaltered. The behavioral effects of juvenile stress itself at adulthood were modest (decreased activity in the circular corridor) with no evidence of enhanced anxiety. Imposition of an acute severe stressor (immobilization on boards, IMO) did not increase anxiety in control animals, as evaluated one week later in the elevated-plus maze (EPM), but it potentiated the acoustic startle response (ASR). However, acute IMO did enhance anxiety in the EPM, in juvenile stressed rats, thereby suggesting that juvenile stress sensitizes rats to the effects of additional stressors.

Comparison of the effects of single and daily repeated immobilization stress on resting activity and heterotypic sensitization of the hypothalamic-pituitary-adrenal axis

Acute exposure to severe stressors causes marked activation of the hypothalamic-pituitary-adrenal (HPA) axis that is reflected on the day after higher resting levels of HPA hormones and sensitization of the HPA response to novel (heterotypic) stressors. However, whether a single exposure to a severe stressor or daily repeated exposure to the same (homotypic) stressor modifies these responses to the same extent has not been studied. In this experiment, we studied this issue in adult male Sprague-Dawley rats daily exposed for seven days to a severe stressor such as immobilization on boards (IMO). A first exposure to 1 h IMO resulted in a marked activation of the HPA axis as reflected in plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone, and such activation was significantly reduced after the seventh IMO. On the day after the first IMO, higher resting levels of ACTH and corticosterone and sensitization of their responses to a short exposure to an open-field (OF) were observed, together with a marked hypoactivity in this environment. Repeated exposure to IMO partially reduced hypoactivity, the increase in resting levels of HPA hormones and the ACTH responsiveness to the OF on the day after the last exposure to IMO. In contrast, corticosterone response was gradually increased, suggesting partial dissociation from ACTH. These results indicate that daily repeated exposure to the same stressor partially reduced the HPA response to the homotypic stressor as well as the sensitization of HPA axis activity observed the day after chronic stress cessation.

Sex-dependent effects of an early life treatment in rats that increases maternal care: vulnerability or resilience?

Early life stress (ELS) in rodents has profound long-term effects that are partially mediated by changes in maternal care. ELS not only induces “detrimental” effects in adulthood, increasing psychopathology, but also promotes resilience to further stressors. In Long-Evans rats, we evaluated a combination of two procedures as a model of ELS: restriction of bedding during the first post-natal days and exposure to a “substitute” mother. The maternal care of biological and “substitute” mothers was measured. The male and female offspring were evaluated during adulthood in several contexts. Anxiety was measured by the elevated plus-maze (EPM), acoustic startle response (ASR) and forced swim test (FST). In other group of animals, novelty-seeking was measured (activity in an inescapable novel environment, preference for novel environments and exploration of novel objects). Plasmatic ACTH and corticosterone in basal conditions and in response to stress were also measured. Cognitive impulsivity was assessed by a delay-discounting paradigm, and impulsive action, attention and compulsive-like behavior by a five choice serial reaction time task (5CSRTT). ELS decreased pup body weight and increased the care of the biological mother; however, the “substitute” mother did not exhibit overt maltreatment. A mixture of “detrimental” and “beneficial” effects was shown. In the 5CSRTT, attention was impaired in both genders, and in females, ELS increased compulsive-like behavior. Novel object exploration was only increased by ELS in males, but the preference for novel spaces decreased in both genders. Baseline anxiety (EPM and ASR) and recognition memory were not affected. Unexpectedly, ELS decreased the ACTH response to novelty and swim stress and increased active coping in the FST in both genders. Cognitive impulsivity was decreased only in females, but impulsive action was not affected. The enhancement in maternal care may “buffer” the effects of ELS in a context-dependent manner.

Pilot-scale road subbase made with granular material formulated with MSWI bottom ash and stabilized APC fly ash: environmental impact assessment

A granular material (GM) to be used as road sub-base was formulated using 80% of weathered bottom ash (WBA) and 20% of mortar. The mortar was prepared separately and consisted in 50% APC and 50% of Portland cement. A pilot-scale study was carried on by constructing three roads in order to environmentally evaluate the performance of GM in a real scenario. By comparing the field results with those of the column experiments, the overestimations observed at laboratory scale can be explained by the potential mechanisms in which water enters into the road body and the pH of the media. An exception was observed in the case of Cu, whose concentration release at the test road was higher. The long-time of exposure at atmospheric conditions might have favoured oxidation of organic matter and therefore the leaching of this element. The results obtained showed that immobilization of all heavy metals and metalloids from APC is achieved by the pozzolanic effect of the cement mortar. This is, to the knowledge of the authors, the only pilot scale study that is considering reutilization of APC as a safe way to disposal.

Individual differences and the characterization of animal models of psychopathology: a strong challenge and a good opportunity

Despite the development of valuable new techniques (i.e., genetics, neuroimage) for the study of the neurobiological substrate of psychiatric diseases, there are strong limitations in the information that can be gathered from human studies. It is thus critical to develop appropriate animal models of psychiatric diseases to characterize their putative biological bases and the development of new therapeutic strategies. The present review tries to offer a general perspective and several examples of how individual differences in animals can contribute to explain differential susceptibility to develop behavioral alterations, but also emphasizes methodological problems that can lead to inappropriate or over-simplistic interpretations. A critical analysis of the approaches currently used could contribute to obtain more reliable data and allow taking full advantage of new and sophisticated technologies. The discussion is mainly focused on anxiety-like and to a lower extent on depression-like behavior in rodents.

Adaptation of the pituitary-adrenal axis to daily repeated forced swim exposure in rats is dependent on the temperature of water

Comparison of exposure to certain predominantly emotional stressors reveals a qualitatively similar neuroendocrine response profile as well as a reduction of physiological responses after daily repeated exposure (adaptation). However, particular physical components of the stressor may interfere with adaptation. As defective adaptation to stress can enhance the probability to develop pathologies, we studied in adult male rats (n = 10/group) swimming behavior (struggling, immobility and mild swim) and physiological responses (ACTH, corticosterone and rectal temperature) to daily repeated exposure to forced swim (20 min, 13 d) at 25 or 36 °C (swim25 or swim36). Rats were repeatedly blood-sampled by tail-nick and hormones measured by radioimmunoassay. Some differences were observed between the two swim temperature groups after the first exposure to forced swim: (a) active behaviors were greater in swim25 than swim36 groups; (b) swim25 but not swim36 caused hypothermia; and (c) swim36 elicited the same ACTH response as swim25, but plasma corticosterone concentration was lower for swim36 at 30 min post-swim. After daily repeated exposure, adaptation in ACTH secretion was observed with swim36 already on day 4, whereas with swim25 adaptation was not observed until day 13 and was of lower magnitude. Nevertheless, after repeated exposure to swim25 a partial protection from hypothermia was observed and the two swim conditions resulted in progressive reduction of active behaviors. Thus, daily repeated swim at 25 °C impairs adaptation of the hypothalamic-pituitary-adrenal axis as compared to swim at 36 °C, supporting the hypothesis that certain physical components of predominantly emotional stressors can interfere with the process of adaptation.

Not all stressors are equal: behavioral and endocrine evidence for development of contextual fear conditioning after a single session of footshocks but not of immobilization

Exposure of animals to footshocks (FS) in absence of any specific cue results in the development of fear to the compartment where shocks were given (contextual fear conditioning), and this is usually evaluated by time spent freezing. However, the extent to which contextual fear conditioning always develops when animals are exposed to other stressors is not known. In the present work we firstly demonstrated, using freezing, that exposure of adult rats to a single session of FS resulted in short-term and long-term contextual fear conditioning (freezing) that was paralleled by increased hypothalamic-pituitary-adrenal (HPA) activation. In contrast, using a similar design, no HPA or behavioral evidence for such conditioning was found after exposure to immobilization on boards (IMO), despite this stressor being of similar severity as FS on the basis of standard physiological measures of stress, including HPA activation. In a final experiment we directly compared the exposure to the two stressors in the same type of context and tested for the development of conditioning to the context and to a specific cue for IMO (the board). We observed the expected high levels of freezing and the conditioned HPA activation after FS, but not after IMO, regardless of the presence of the board during testing. Therefore, it can be concluded that development of fear conditioning to context or particular cues, as evaluated by either behavioral or endocrine measures, appears to be dependent on the nature of the aversive stimuli, likely to be related to biologically preparedness to establish specific associations.

Acute stress-induced sensitization of the pituitary-adrenal response to heterotypic stressors: independence of glucocorticoid release and activation of CRH1 receptors

A single exposure to some severe stressors causes sensitization of the hypothalamic-pituitary-adrenal (HPA) response to novel stressors. However, the putative factors involved in stress-induced sensitization are not known. In the present work we studied in adult male rats the possible role of glucocorticoids and CRH type 1 receptor (CRH-R1), using an inhibitor of glucocorticoid synthesis (metyrapone, MET), the glucocorticoid receptor (GR) antagonist RU38486 (mifepristone) and the non-peptide CRH-R1 antagonist R121919. In a first experiment we demonstrated with different doses of MET (40-150 mg/kg) that the highest dose acted as a pharmacological stressor greatly increasing ACTH release and altering the normal circadian pattern of HPA hormones, but no dose affected ACTH responsiveness to a novel environment as assessed 3 days after drug administration. In a second experiment, we found that MET, at a dose (75 mg/kg) that blocked the corticosterone response to immobilization (IMO), did not alter IMO-induced ACTH sensitization. Finally, neither the GR nor the CRH-R1 antagonists blocked IMO-induced ACTH sensitization on the day after IMO. Thus, a high dose of MET, in contrast to IMO, was unable to sensitize the HPA response to a novel environment despite the huge activation of the HPA axis caused by the drug. Neither a moderate dose of MET that markedly reduced corticosterone response to IMO, nor the blockade of GR or CRH-R1 receptors was able to alter stress-induced HPA sensitization. Therefore, stress-induced sensitization is not the mere consequence of a marked HPA activation and does not involve activation of glucocorticoid or CRH-R1 receptors.

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.