Citalopram amplifies the influence of living conditions on mood in depressed patients enrolled in the STAR*D study.

Selective serotonin reuptake inhibitors (SSRIs), the most commonly prescribed antidepressant drugs, have a variable and incomplete efficacy. In order to better understand SSRI action, we explored the hypothesis that SSRIs do not affect mood per se but amplify the influence of the living conditions on mood. To this aim, we exploited the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) data set, selected a subpopulation of 591 patients with an overlapping clinical history and analyzed treatment outcome according to dosage -20 or 40 mg per day of citalopram. We found that sociodemographic characteristics affected treatment response in the same direction in the two dose groups, but these effects reached statistical significance only in the 40 mg per day dose group. In the latter, higher improvement rate was associated with having a working employment status (P=0.0219), longer education (P=0.0053), high income (P=0.01) or a private insurance (P=0.0031), and the higher remission rate was associated with having a working employment status (P=0.0326) or longer education (P=0.0484). Moreover, the magnitude of the effect of the sociodemographic characteristics on mood, measured as the percent of patients showing a positive outcome when exposed to favorable living conditions, was much greater-up to 37-fold-in the 40 compared to the 20 mg per day dose group. Overall, our results indicate that citalopram amplifies the influence of the living conditions on mood in a dose-dependent manner. These findings provide a potential explanation for the variable efficacy of SSRIs and might lead to the development of personalized strategies aimed at enhancing their efficacy.

Fluoxetine effects on molecular, cellular and behavioral endophenotypes of depression are driven by the living environment.

Selective serotonin reuptake inhibitors (SSRIs) represent the most common treatment for major depression. However, their efficacy is variable and incomplete. In order to elucidate the cause of such incomplete efficacy, we explored the hypothesis positing that SSRIs may not affect mood per se but, by enhancing neural plasticity, render the individual more susceptible to the influence of the environment. Consequently, SSRI administration in a favorable environment promotes a reduction of symptoms, whereas in a stressful environment leads to a worse prognosis. To test such hypothesis, we exposed C57BL/6 mice to chronic stress in order to induce a depression-like phenotype and, subsequently, to fluoxetine treatment (21 days), while being exposed to either an enriched or a stressful condition. We measured the most commonly investigated molecular, cellular and behavioral endophenotypes of depression and SSRI outcome, including depression-like behavior, neurogenesis, brain-derived neurotrophic factor levels, hypothalamic-pituitary-adrenal axis activity and long-term potentiation. Results showed that, in line with our hypothesis, the endophenotypes investigated were affected by the treatment according to the quality of the living environment. In particular, mice treated with fluoxetine in an enriched condition overall improved their depression-like phenotype compared with controls, whereas those treated in a stressful condition showed a distinct worsening. Our findings suggest that the effects of SSRI on the depression- like phenotype is not determined by the drug per se but is induced by the drug and driven by the environment. These findings may be helpful to explain variable effects of SSRI found in clinical practice and to device strategies aimed at enhancing their efficacy by means of controlling environmental conditions.

Consistent behavioral phenotype differences between inbred mouse strains in the IntelliCage.

The between-laboratory effects on behavioral phenotypes and spatial learning performance of three strains of laboratory mice known for divergent behavioral phenotypes were evaluated in a fully balanced and synchronized study using a completely automated behavioral phenotyping device (IntelliCage). Activity pattern and spatial conditioning performance differed consistently between strains, i.e. exhibited no interaction with the between-laboratory factor, whereas the gross laboratory effect showed up significantly in the majority of measures. It is argued that overall differences between laboratories may not realistically be preventable, as subtle differences in animal housing and treatment will not be controllable, in practice. However, consistency of strain (or treatment) effects appears to be far more important in behavioral and brain sciences than the absolute overall level of such measures. In this respect, basic behavioral and learning measures proved to be highly consistent in the IntelliCage, therefore providing a valid basis for meaningful research hypothesis testing. Also, potential heterogeneity of behavioral status because of environmental and social enrichment has no detectable negative effect on the consistency of strain effects. We suggest that the absence of human interference during behavioral testing is the most prominent advantage of the IntelliCage and suspect that this is likely responsible for the between-laboratory consistency of findings, although we are aware that this ultimately needs direct testing.

Epigenetic control of neurobehavioural plasticity: the role of neurotrophins.

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are two neurotrophins involved in the differentiation, growth and maintenance of selected peripheral and central populations of neuronal cells, during development and at adulthood. Furthermore, neuronal activity enhances expression and action of these neurotrophins, modifying synaptic transmission and connectivity. Neurotrophin production has been shown to be experience-dependent. In particular, during early developmental phases, experiences such as maternal deprivation or exposure to an enriched environment markedly affect NGF and BDNF levels. At adulthood, psychosocial stress has been shown to markedly alter NGF and BDNF levels, both in plasma and selected brain areas, including the hypothalamus and hippocampus. These results have been extended to humans, showing that NGF levels are enhanced by emotional stress induced by parachute jumping. Overall, these findings suggest a role of neurotrophins as factors mediating both short- and long-term effects of experience on brain structure and function.

Transgenic and knock-out mouse pups: the growing need for behavioral analysis.

Few laboratories working with transgenic and knockout mice analyze the neurobehavioral consequences of genetic manipulation in early ontogeny. However, the study of behavioral endpoints during the early postnatal period in genetically modified mice is important not only to assess possible developmental abnormalities, but also to better understand and disentangle the effects of genetic manipulations in adulthood. We propose that the assessment of neurobehavioral development represents an appropriate strategy to identify possible compensatory and/or unexpected effects. Nowadays, a large number of experimental protocols that take into account the practical constraints imposed by the peculiar physiological and behavioral responses of an immature subject are available to assess the neurobehavioral profile of developing mice. While this knowledge should be applied to the field of transgenic and knock-out mice in general, it should be recommended, in particular, for the study of mouse models of neurodevelopmental disorders.

Ultrasonic vocalisation emitted by infant rodents: a tool for assessment of neurobehavioural development.

Ultrasonic vocalisations (USVs) emitted by altricial rodent pups are whistle-like sounds with frequencies between 30 and 90 kHz. These signals play an important communicative role in mother-offspring interaction since they elicit in the dam a prompt response concerning caregiving behaviours. Both physical and social parameters modulate the USV emission in the infant rodent. Recently, a more detailed analysis of the ultrasonic vocalisation pattern, considering the spectrographic structure of sounds has allowed a deeper investigation of this behaviour. In order to investigate neurobehavioural development, the analysis of USVs presents several advantages, mainly: (i) USVs are one of the few responses produced by very young mice that can be quantitatively analysed and elicited by quantifiable stimuli; (ii) USV production follows a clear ontogenetic profile from birth to PND 14-15, thus allowing longitudinal neurobehavioural analysis during very early postnatal ontogeny. The study of this ethologically-ecologically relevant behaviour represent a valid model to evaluate possible alterations in the neurobehavioural development of perinatally treated or genetically modified infant rodents. Furthermore, the role played by several receptor agonists and antagonists in modulating USV rate makes this measure particularly important when investigating the effects of anxiogenic and anxiolytic compounds, and emotional behaviour in general.

Learning performances, brain NGF distribution and NPY levels in transgenic mice expressing TNF-alpha.

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine involved in a variety of neurobiological activities including changing behavior and regulation of both neurotrophin and neuropeptide levels. In this study we used two lines of transgenic mice overexpressing brain TNF-alpha characterized by neurological deficits (line Tg6074) or phenotypically normal (line TgK3). We analyzed whether or not impairments in learning and memory processes due to TNF-alpha overexpression were associated with changes in endogenous brain NGF, NPY and beta-amyloid. The results indicate that full TNF-alpha transgene expression disrupted the learning capabilities of transgenic mice (both Tg6074 and TgK3). NGF decreased in the hippocampus of both transgenic mice whereas hippocampal NPY slightly potentiated in Tg6074. The decrease in NGF is correlated with deficits in spatial learning and memory whereas inflammation in the brain of Tg6074 could be responsible of the hippocampal increase in NPY. As a whole, these results show that transgenic mice overexpressing TNF-alpha in the brain represent a useful model for studying neuronal degeneration and brain inflammatory processes.

Prenatal exposure to anti-HIV drugs. long-term neurobehavioral effects of lamivudine (3TC) in CD-1 mice.

The present study was aimed at investigating the long-term effects of prenatal exposure to lamivudine (3TC), an antiretroviral drug used in clinical practice alone or in combination with zidovudine (AZT) to prevent mother-to-child transmission of the HIV virus. Pregnant CD-1 mice were given per os twice daily either 3TC at different doses (125, 250, or 500 mg/kg) or vehicle solution (NaCl 0. 9%) from pregnancy day 10 to delivery. Offspring behavior was examined on postnatal day 35 in a 20-min social interaction test. At adulthood different behavioral endpoints were analyzed, including locomotor activity and exploration in an open field following administration of the muscarinic antagonist scopolamine (2 mg/kg), spatial learning in either radial arm or Morris water maze, virgin female behavior in a maternal induction test, and pain sensitivity in a hot-plate test (52 +/- 0.1 degrees C). Our findings confirm the low neurotoxicity of 3TC in comparison to AZT. However some significant behavioral alterations were found, namely (1) a decrease in immobility in the open field test, (2) an increase in the responsiveness to scopolamine shown by the 500-mg/kg 3TC mice (sniffing behavior) in the open field, and (3) a longer escape latency in the first day of the reversal phase in the Morris task (particularly marked in the 250-mg/kg treatment group). No significant changes in either pain sensitivity, social/affiliative, or maternal behavior were found, although a higher occurrence of aggressive behavior toward foster pups was noted in both 125- and 500-mg/kg 3TC females.

Long-term effects of prenatal 3'-azido-3'-deoxythymidine (AZT) exposure on intermale aggressive behaviour of mice.

RATIONALE: AZT treatment of seropositive pregnant women and their neonates has been widely used due to its effectiveness in reducing vertical transmission of HIV, but medium- and long-term effects of AZT on neurobehavioural development and adult responding are still poorly described. OBJECTIVE: The aim of the present study was to evaluate the long-term effects of prenatal AZT treatment on aggressive behaviour of adult male mice. METHODS: Pregnant CD-1 mice were given saline vehicle, 0.4, or 0.8 mg/ml AZT in their drinking water from gestation day 10 to delivery. Social-aggressive types of interaction were assessed in their male offspring following a 4-week isolation period. Two groups of subjects were used, each undergoing a different type of test: test 1 consisted of a single 20-min encounter with an isolated same-strain opponent on postnatal day (PND) 90, while in test 2 (PND 150) subjects were paired for 10 min for 5 consecutive days with a non-isolated opponent. RESULTS: Slight changes in both aggressive and defensive components of the male-specific agonistic pattern were evident only in test 1, AZT mice displaying a limited increase of aggressive behaviour compared to their controls. CONCLUSIONS: Although the long-term effects of prenatal AZT on social behaviour are limited, they may be of some relevance for paediatricians in order to plan a follow-up of infants, children and adolescents exposed in utero to antiretroviral drugs.

Neurobehavioral effects of prenatal lamivudine (3TC) exposure in preweaning mice.

The present study provides a characterization of the behavioral changes induced in preweaning mice by prenatal exposure to lamivudine (3TC), an antiviral drug recently entered in the clinical practice to treat HIV patients. Pregnant CD1 mice were given per os bidaily either 3TC at different doses (125, 250, or 500 mg/kg) or vehicle solution (saline 0.9%) from pregnancy day 10 to delivery. Data on reproductive performance, such as gestation length, litter size, and offspring viability, were collected. Offspring were then examined for a series of different somatic and behavioral end points, including sensorimotor development, ontogenetic pattern of ultrasonic vocalization, passive avoidance learning, and locomotor activity. In the absence of gross changes in somatic and sensorimotor development, a slight change in ultrasound emission was found on postnatal day (PND) 3, with 125 and 500 mg/kg 3TC-treated offspring emitting a lower number of ultrasounds. Learning and retention performances of a passive-avoidance task on PND 20-21 were unaffected by 3TC treatment, while decreased habituation in an automated locomotor activity test was evident in male offspring exposed to 250 and 500 mg/kg 3TC.

Ultrasonic vocalizations elicit orienting and associative reactions in preweanling mice.

On postnatal days (PND) 12 and 13, 90 male Swiss CD-1 mice were tested for orientation to 3 intensities of recorded ultrasounds while climbing an inclined wire grid surface. Motor responses and vocalization to replayed ultrasounds (55-75 kHz) of 20-, 40-, and 60-dB SPL indicated an intensity dependence. In Experiment 2, 138 pups were exposed to either contingent or noncontingent pairings of recorded ultrasounds of 55-75 kHz, averaging 40 dB, and mild inescapable footshocks, or taped vocalizations or footshocks only on PND 12, 14, or 16. At PND 18, subjects were tested for passive avoidance following exposure to the taped ultrasounds only upon entry into the dark side of a black-white compartment. Results suggested only overall, nonspecific effects of pretreatment to elicit responses antagonistic to motor activity. In Experiment 3, 36 pups at PND 15 were tested for passive avoidance with the ultrasound recordings of 40- or 80-dB onset upon entry to the dark compartment; a third group had no ultrasound exposure. A significant intensity effect confirmed that the ultrasounds had prepotent properties.

Effects of prenatal zidovudine treatment on learning and memory capacities of preweanling and young adult mice.

The present study analyzed the short and long-term effects of prenatal zidovudine (AZT) exposure on learning and memory capacities of CD-1 mice. Two tasks normally used in rodents were used, namely a passive avoidance step-through task and a Morris navigation task. AZT (0, 0.4, and 0.8 mg/ml) was administered via drinking water to pregnant CD-1 females from day 10 of gestation to delivery. Data on reproductive performance, such as gestation length, litter size, and pup mortality were collected. Avoidance learning in the offspring was tested on postnatal day (PND) 15, while spatial learning performances in the Morris water maze were obtained on PND 45. Retention of the passive avoidance response was mildly impaired in the offspring exposed to the 0.8 mg/ml AZT solution, whereas spatial learning on PND 45 was unaffected.

Effects of prenatal AZT on mouse neurobehavioral development and passive avoidance learning.

Recent evidence has shown that perinatal administration of zidovudine (AZT) to HIV-infected mothers reduces the risk of maternal-infant transmission of the virus. Treatment of pregnant seropositive women with AZT is becoming a common medical practice, despite the paucity of information about the potential neurotoxic/behavioral-teratogenic effects of AZT on the developing organism. The aim of the present study is to evaluate in mice the short-, medium-, and long-term effects of prenatal exposure to AZT on neurobehavioral development. Pregnant mice were given 0.2, 0.4, and 2.0 mg/ml AZT in drinking water from day 10 of gestation to delivery. Offspring's viability was severely affected in the 2.0 mg/ml AZT group. Thus, behavioral analysis was carried out in offspring of 0.2 and 0.4 mg/ml AZT-treated females only. Some limited but significant alterations were found, such as stunted body weight, delayed appearance of the pole-grasping reflex, and a slight impairment in the acquisition phase of a passive avoidance response. Moreover, sexual differences in some items of the social behavior repertoire appeared to be affected by AZT treatment.

Ultrasonic vocalizations by infant laboratory mice: a preliminary spectrographic characterization under different conditions.

During the first 2 to 3 weeks of life, isolated neonatal mice emit ultrasonic vocalizations, with various conditions such as hypothermia or olfactory or tactile stimulation eliciting this behavior. Although it is known that pup vocalizations stimulate prompt expression of maternal behavior, the communicative role of infant ultrasonic calls is still a matter of investigation. A fine-grained spectrographic analysis of ultrasonic calls emitted by pups exposed to different conditions was performed. Forty 8-day-old outbred CD-1 mice (Mus musculus) were isolated from their mothers and littermates and randomly exposed to one of the following conditions: (a) odor from the nest, (b) social isolation, (c) low temperature-isolation, (d) tactile stimulation, or (e) odor from a conspecific adult male. Upon consideration of the spectrogram typology and emission frequency interval, it appears that the conditions under which vocalizations are emitted influence the sound characteristics of call production.