Selectively bred rodents as models of depression and anxiety

Stress related diseases such as depression and anxiety have a high degree of co morbidity, and represent one of the greatest therapeutic challenges for the twenty-first century. The present chapter will summarize existing rodent models for research in psychiatry, mimicking depression- and anxiety-related diseases. In particular we will highlight the use of selective breeding of rodents for extremes in stress-related behavior. We will summarize major behavioral, neuroendocrine and neuronal parameters, and pharmacological interventions, assessed in great detail in two rat model systems: The Flinders Sensitive and Flinders Resistant Line rats (FSL/FRL model), and rats selectively bred for high (HAB) or low (LAB) anxiety related behavior (HAB/LAB model). Selectively bred rodents also provide an excellent tool in order to study gene and environment interactions. Although it is generally accepted that genes and environmental factors determine the etiology of mental disorders, precise information is limited: How rigid is the genetic disposition? How do genetic, prenatal and postnatal influences interact to shape adult disease? Does the genetic predisposition determine the vulnerability to prenatal and postnatal or adult stressors? In combination with modern neurobiological methods, these models are important to elucidate the etiology and pathophysiology of anxiety and affective disorders, and to assist in the development of new treatment paradigms.

Comprehensive gene-based association study of a chromosome 20 linked region implicates novel risk loci for depressive symptoms in psychotic illness

BACKGROUND

Prior genomewide scans of schizophrenia support evidence of linkage to regions of chromosome 20. However, association analyses have yet to provide support for any etiologically relevant variants.

METHODS

We analyzed 2988 LD-tagging single nucleotide polymorphisms (SNPs) in 327 genes on chromosome 20, to test for association with schizophrenia in 270 Irish high-density families (ISHDSF, N = 270 families, 1408 subjects). These SNPs were genotyped using an Illumina iSelect genotyping array which employs the Infinium assay. Given a previous report of novel linkage with chromosome 20p using latent classes of psychotic illness in this sample, association analysis was also conducted for each of five factor-derived scores based on the Operational Criteria Checklist for Psychotic Illness (delusions, hallucinations, mania, depression, and negative symptoms). Tests of association were conducted using the PDTPHASE and QPDTPHASE packages of UNPHASED. Empirical estimates of gene-wise significance were obtained by adaptive permutation of a) the smallest observed P-value and b) the threshold-truncated product of P-values for each locus.

RESULTS

While no single variant was significant after LD-corrected Bonferroni-correction, our gene-dropping analyses identified loci which exceeded empirical significance criteria for both gene-based tests. Namely, R3HDML and C20orf39 are significantly associated with depressive symptoms of schizophrenia (P(emp)<2×10⁻⁵) based on the minimum P-value and truncated-product methods, respectively.

CONCLUSIONS

Using a gene-based approach to family-based association, R3HDML and C20orf39 were found to be significantly associated with clinical dimensions of schizophrenia. These findings demonstrate the efficacy of gene-based analysis and support previous evidence that chromosome 20 may harbor schizophrenia susceptibility or modifier loci.

The relation between depression and parkin genotype: the CORE-PD study

BACKGROUND

Mutations in parkin are a known genetic risk factor for early onset Parkinson's disease (EOPD) but their role in non-motor manifestations is not well established. Genetic factors for depression are similarly not well characterized. We investigate the role of parkin mutations in depression among those with EOPD and their relatives.

METHODS

We collected psychiatric information using the Patient Health Questionnaire and Beck Depression Inventory II on 328 genotyped individuals including 88 probands with early onset PD (41 with parkin mutations, 47 without) and 240 first and second-degree relatives without PD.

RESULTS

Genotype was not associated with depression risk among probands. Among unaffected relatives of EOPD cases, only compound heterozygotes (n = 4), and not heterozygotes, had significantly increased risk of depressed mood (OR = 14.1; 95% CI 1.2-163.4), moderate to severe depression (OR = 17.8; 95% CI 1.0-332.0), depression (score ≥ 15) on the Beck Depression Inventory II (BDI-II) (OR = 51.9; 95% CI 4.1-657.4), and BDI-II total depression score (β = 8.4; 95% CI 2.4-11.3) compared to those without parkin mutations.

CONCLUSIONS

Relatives of EOPD cases with compound heterozygous mutations and without diagnosed PD may have a higher risk of depression compared to relatives without parkin mutations. These findings support evidence of a genetic contribution to depression and may extend the phenotypic spectrum of parkin mutations to include non-motor manifestations that precede the development of PD.

Life stressors and 5-HTTLPR interaction in relation to midpregnancy depressive symptoms among African-American women

OBJECTIVE

In earlier analyses of nonHispanic White women we found a stronger relation between abuse history and midpregnancy elevated depressive symptoms in women with the serotonin transporter (5-HTTLPR) S/S genotype. Here, we focus on African-American women (N=698). Our inquiry is motivated by racial differences in depression diagnosis/treatment, stressors, and frequency of major 5-HTTLPR alleles (S, LA, LG).

MATERIALS AND METHODS

Stressful life events (lifetime) and depressive symptoms (current) were ascertained at 15-27 weeks gestation. A Center for Epidemiological Studies Depression Score of more than or equal to 18 was considered 'elevated'. Life events were scored together and separated into six subconstructs. 5-HTTLPR genotypes were grouped as follows: (i) L and S alleles, (ii) S-LG equivalence ('triallelic to biallelic'), and (iii) LA/LA, all others, S/S ('high/intermediate/low'). Odds ratios (OR) for 'elevated' depressive symptoms-life events (total and subconstructs) relations were calculated for each genotype grouping.

RESULTS

The prevalence of 'elevated' depressive symptoms did not vary by genotype. The relation between stressful life events and 'elevated' depressive symptoms was stronger in S/S compared with LA/LA genotype (interaction P=0.11). Of the six subconstructs, only abuse showed a statistically significant gene-environment interaction. The OR for the abuse-'elevated' depressive symptoms association was greater for S/S vs. LA/LA genotype (interaction P=0.03) and in the 'triallelic to biallelic' grouping (interaction P=0.04). In the 'high/intermediate/low' grouping, 'low' (S/S) had a higher OR (5.5) than both 'intermediate' and 'high' (ORs≤2.3) (interaction P=0.10).

CONCLUSIONS

These results show the importance of examining racial groups, specific stressful events, and different 5-HTTLPR genotype groupings when exploring gene-environment interactions in depression.

Maternal depression and anxiety are associated with altered gene expression in the human placenta without modification by antidepressant use: implications for fetal programming

We sought to determine if maternal depression, anxiety, and/or treatment with selective serotonin reuptake inhibitors (SSRIs) affect placental human serotonin transporter (SLC6A4), norepinephrine transporter (SLC6A2), and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) gene expression. Relative mRNA expression was compared among placental samples (n = 164) from healthy women, women with untreated depression and/or anxiety symptoms during pregnancy, and women who used SSRIs. SLC6A4 expression was significantly increased in placentas from women with untreated mood disorders and from women treated with SSRIs, compared to controls. SLC6A2 and 11β-HSD2 expression was increased in noncontrol groups, though the differences were not significant. SLC6A4, SLC6A2, and 11β-HSD2 expression levels were positively correlated. The finding that maternal depression/anxiety affects gene expression of placental SLC6A4 suggests a possible mechanism for the effect(s) of maternal mood on fetal neurodevelopmental programming. SSRI treatment does not further alter the elevated SLC6A4 expression levels observed with exposure to maternal depression or anxiety.

Interactive effects of corticotropin releasing hormone receptor 1, serotonin transporter linked polymorphic region, and child maltreatment on diurnal cortisol regulation and internalizing symptomatology

Within an allostatic load framework, the effect of Gene × Environment (G × E) interactions on diurnal cortisol regulation and internalizing symptomatology were investigated. Variation in the corticotropin releasing hormone receptor 1 (CRHR1) TAT haplotype and serotonin transporter linked polymorphic region (5-HTTLPR) was determined in a sample of maltreated (n = 238, 21.4% with early physical and sexual abuse) and nonmaltreated (n = 255) children (M age = 10.08) participating in a summer research camp. Internalizing and depressive symptoms were assessed by other and self-report. G × E effects for CRHR1 and maltreatment and early abuse on diurnal cortisol regulation were observed; CRHR1 variation was related to cortisol dysregulation only among maltreated children. Early abuse and high internalizing symptoms also interacted to predict atypical diurnal cortisol regulation. The interaction of CRHR1, 5-HTTLPR, and child maltreatment (G × G × E) identified a subgroup of maltreated children with high internalizing symptoms who shared the same combination of the two genes. The findings support an allostatic load perspective on the effects of the chronic stress associated with child maltreatment on cortisol regulation and internalizing symptomatology as moderated by genetic variation.

Pharmacogenetics and the pharmacological management of depression

Depression is a chronic disease seen in many healthcare settings. Current pharmacological treatment options are successful in two-thirds of patients. One CYP450 enzyme, CYP2D6, is responsible for the metabolism of 30% of all drugs including many antidepressants. Phenotypes of metabolizer status affect antidepressant treatment outcomes and adverse drug reactions.

Serotonin transporter genotype modulates the association between depressive symptoms and amygdala activity among psychiatrically healthy adults

Recent attempts to understand the biological bases of depression vulnerability have revealed that both the short allele of the serotonin transporter-linked polymorphic region (5-HTTLPR) and activity in the amygdala are associated with depression. Other studies have reported amygdala hyperactivity associated with the 5-HTTLPR short allele, linking the genetic and neuroimaging lines of research and suggesting a mechanism whereby the short allele confers depression risk. However, fewer investigations have examined the associations among depression, 5-HTTLPR variability, and amygdala activation in a single study. The current study thus investigated whether 5-HTTLPR genotype modulates the association between depressive symptoms and amygdala activity among psychiatrically healthy adults. Regional cerebral blood flow was measured with perfusion fMRI during a task-free scan. We hypothesized differential associations between depressive symptoms and amygdala activity among individuals homozygous for the short allele and individuals homozygous for the long allele. Both whole brain analyses and region-of-interest analyses confirmed this prediction, revealing a significant negative association among the long allele group and a trend of positive association among the short allele group. These results complement existing reports of short allele related amygdala hyperactivity and suggest an additional neurobiological mechanism whereby the 5-HTTLPR is associated with psychiatric outcomes.

Chronic variable physical stress during the peripubertal-juvenile period causes differential depressive and anxiogenic effects in the novelty-seeking phenotype: functional implications for hippocampal and amygdalar brain-derived neurotrophic factor and the mossy fibre plasticity

Experimentally naive rats show variance in their locomotor reactivity to novelty, some displaying higher (HR) while others displaying lower (LR) reactivity, associated with vulnerability to stress. We employed a chronic variable physical stress regimen incorporating intermittent and random exposures of physical stressors or control handling during the peripubertal-juvenile period to assess interactions between stress and the LRHR phenotype in depressive- and anxiety-like behaviors on the forced swim and social interaction tests, respectively. A decrease in immobility in the forced swim test along with a decrease in social contact in the social interaction test were observed in the juvenile HRs, coupled with increases in brain-derived neurotrophic factor (BDNF) mRNA in the hippocampus and in the basolateral amygdala with chronic variable physical stress. In contrast, an increase in immobility in the forced swim test and a decrease in social contact was observed in the LR counterparts coupled with an increase in the BDNF mRNA in the basolateral amygdala following chronic variable physical stress. Furthermore, chronic physical stress led to increased H3 and H4 acetylation at the P2 and P4 promoters of the hippocampal BDNF gene in the HR rats that is associated with increased suprapyramidal mossy fibre (SP-MF) terminal field volume. In contrast, chronic variable physical stress led to decreased H4 acetylation at the P4 promoter, associated with decreased SP-MF volume in the LR rats. These findings show dissociation in depressive- and anxiety-like behaviors following chronic variable physical stress in the juvenile HR animals that may be mediated by increased levels of BDNF in the hippocampus and in the amygdala, respectively. Moreover, chronic variable physical stress during the peripubertal-juvenile period results in opposite effects in depressive-like behavior in the LRHR rats by way of inducing differential epigenetic regulation of the hippocampal BDNF gene that, in turn, may mediate mossy fibre sprouting.

Hippocampal neurogenesis and dendritic plasticity support running-improved spatial learning and depression-like behaviour in stressed rats

Exercise promotes hippocampal neurogenesis and dendritic plasticity while stress shows the opposite effects, suggesting a possible mechanism for exercise to counteract stress. Changes in hippocampal neurogenesis and dendritic modification occur simultaneously in rats with stress or exercise; however, it is unclear whether neurogenesis or dendritic remodeling has a greater impact on mediating the effect of exercise on stress since they have been separately examined. Here we examined hippocampal cell proliferation in runners treated with different doses (low: 30 mg/kg; moderate: 40 mg/kg; high: 50 mg/kg) of corticosterone (CORT) for 14 days. Water maze task and forced swim tests were applied to assess hippocampal-dependent learning and depression-like behaviour respectively the day after the treatment. Repeated CORT treatment resulted in a graded increase in depression-like behaviour and impaired spatial learning that is associated with decreased hippocampal cell proliferation and BDNF levels. Running reversed these effects in rats treated with low or moderate, but not high doses of CORT. Using 40 mg/kg CORT-treated rats, we further studied the role of neurogenesis and dendritic remodeling in mediating the effects of exercise on stress. Co-labelling with BrdU (thymidine analog) /doublecortin (immature neuronal marker) showed that running increased neuronal differentiation in vehicle- and CORT-treated rats. Running also increased dendritic length and spine density in CA3 pyramidal neurons in 40 mg/kg CORT-treated rats. Ablation of neurogenesis with Ara-c infusion diminished the effect of running on restoring spatial learning and decreasing depression-like behaviour in 40 mg/kg CORT-treated animals in spite of dendritic and spine enhancement. but not normal runners with enhanced dendritic length. The results indicate that both restored hippocampal neurogenesis and dendritic remodelling within the hippocampus are essential for running to counteract stress.

Depressive symptoms evaluated by the Calgary Depression Scale for Schizophrenia (CDSS): genetic vulnerability and sex effects

The present study compares the occurrence of depressive symptoms evaluated by the Calgary Depression Scale for Schizophrenia (CDSS) in patients of Multiplex (MS) and Simplex Schizophrenia families (SS). The Positive and Negative Syndrome Scale (PANSS) was used to evaluate psychopathology. A total of 206 paranoid schizophrenia patients were studied according DSM-IV criteria. The Family Interview for Genetic Studies (FIGS) was used to study the families. A result in the FIGS for a positive family history of schizophrenia was referred as MS (patients); its lack as SS (patients). CDSS scores were compared among MS and SS patients and possible sex differences intra- and inter-groups were explored. In the analysis of our sample (30) 19% of the total persons with schizophrenia group was depressed. The depressive symptoms measured by the CDSS were higher in females and the MS males group. Males from MS group showed more depressive symptoms than males from SS group. No differences with females from both groups were found. Findings in this study underscore the importance of gender and family history in understanding the heterogeneity of schizophrenia. This study suggests that sex and familiar history are important to consider in studying depressive symptoms.

SLC6A4 methylation modifies the effect of the number of traumatic events on risk for posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is a common and debilitating mental disorder that occurs following exposure to a traumatic event. However, most individuals do not develop PTSD following even a severe trauma, leading to a search for new variables, such as genetic and other molecular variation, associated with vulnerability and resilience in the face of trauma exposure.

METHOD

We examined whether serotonin transporter (SLC6A4) promoter genotype and methylation status modified the association between number of traumatic events experienced and PTSD in a subset of 100 individuals from the Detroit Neighborhood Health Study.

RESULTS

Number of traumatic events was strongly associated with risk of PTSD. Neither SLC6A4 genotype nor methylation status was associated with PTSD in main effects models. However, SLC6A4 methylation levels modified the effect of the number of traumatic events on PTSD after controlling for SLC6A4 genotype. Persons with more traumatic events were at increased risk for PTSD, but only at lower methylation levels. At higher methylation levels, individuals with more traumatic events were protected from this disorder. This interaction was observed whether the outcome was PTSD diagnosis, symptom severity, or number of symptoms.

CONCLUSIONS

Gene-specific methylation patterns may offer potential molecular signatures of increased risk for and resilience to PTSD.

[Molecular changes in inbred mice with individual vulnerability vs resilience to stress-induced depressive-like state]

The C57BL/6 mice were subjected to a chronic combined stress which resulted in the induction of a depressive-like state. The occurrence of a depressive-like state was defined by a decrease in sensitivity to the reward determined by the diminished preference of sweetened solutions over regular drinking water. Such decrease is generally considered as a sign of an unhedonic-like state: one of the key features of clinical depression. Applied here, the paradigm in mice allows unhedonia induction in a subpopulation of stressed animals (54% in the current study); remaining mice are regarded as resilient to stress-induced hedonic deficit. The resilient subgroup is taken, therefore, as a "functional control" for those effects of stress that are not accompanied by development of the stress-induced depressive-like state in mice. The analysis of the mRNA extracted from the hippocampi of stress-subjected and home-cage control mice enabled the assessment of gene expression level of over 13 000 genes. This study showed that unhedonic mice are characterized by an up-regulation of 278 and down-regulation of 174 genes related mostly to the CNS development and functions, inter-cellular interactions and signalling, neurological disorders, apoptosis and behavioural regulation. Resilient animals demonstrated up-regulation of 924 and down-regulation of only 29 genes that control formation of cell assemblies, molecular transport, CNS functioning, neurological disorders and various biochemical reactions. Thus, gene expression profiles in the hippocampus of susceptible vs resilient to stress-induced unhedonia inbred subgroups of animals are strictly distinct in both quantity and quality.

Phenotype in parkinsonian and nonparkinsonian LRRK2 G2019S mutation carriers

OBJECTIVES

Using a family study design, we describe the motor and nonmotor phenotype in probands with LRRK2 G2019S mutations and family members and compare these individuals to patients with idiopathic Parkinson disease (iPD) and unrelated controls.

METHODS

Probands with G2019S mutations and their first-degree relatives, subjects with iPD, and unrelated control subjects were identified from 4 movement disorders centers. All underwent neurologic examinations and tests of olfaction, color vision, anxiety, and depression inventories.

RESULTS

Tremor was more often a presenting feature among 25 individuals with LRRK2-associated PD than among 84 individuals with iPD. Subjects with LRRK2-PD had better olfactory identification compared with subjects with iPD, higher Beck Depression Inventory scores, and higher error scores on Farnsworth-Munsell 100-Hue test of color discrimination. Postural or action tremor was more common among 29 nonmanifesting mutation carriers compared with 53 noncarriers within the families. Nonparkinsonian family members had higher Unified Parkinson's Disease Rating Scale motor scores, more constipation, and worse color discrimination than controls, regardless of mutation status.

CONCLUSIONS

Although tremor is a more common presenting feature of LRRK2-PD than iPD and some nonmotor features differed in degree, the phenotype is largely overlapping. Postural or action tremor may represent an early sign. Longitudinal evaluation of a large sample of nonmanifesting carriers will be required to describe any premotor phenotype that may allow early diagnosis.

Smoking is associated with, but does not cause, depressed mood in pregnancy--a mendelian randomization study

Smokers have a higher prevalence of major depressive episodes and depressive symptoms than the general population, but whether this association is causal, or is due to confounding or reverse causation is uncertain because of the problems inherent in some epidemiological studies. Mendelian randomization, in which a genetic variant is used as a surrogate for measuring exposure, is an approach which may be used to better understand this association. We investigated the rs1051730 single nucleotide polymorphism in the nicotine acetylcholine receptor gene cluster (CHRNA5-CHRNA3-CHRNB4), associated with smoking phenotypes, to determine whether women who continued to smoke were also more likely to report a low mood during pregnancy. We found among women who smoked pre-pregnancy, those with the 1051730 T allele smoked more and were less likely to quit smoking during pregnancy, but were also less likely to report high levels of depressed mood at 18 weeks of pregnancy (per allele OR = 0.84, 95%CI 0.72 to 0.99, p = 0.034). The association between genotype and depressed mood was limited to women who were smokers prior to pregnancy, with weak evidence of an interaction between smoking status and genotype (p = 0.07). Our results do not support a causal role of smoking on depressed mood, but are consistent with a self-medication hypothesis, whereby smoking is used to alleviate symptoms of depression. A replication study using multiple genetic variants which influence smoking via different pathways is required to confirm these findings and provide evidence that the genetic variant is reflecting the effect of quitting smoking on depressed mood, and is not directly affecting mood.

Common genetic influences on depression, alcohol, and substance use disorders in Mexican-American families

Multiple genetic and environmental factors influence the risk for both major depression and alcohol/substance use disorders. In addition, there is evidence that these illnesses share genetic factors. Although, the heritability of these illnesses is well established, relatively few studies have focused on ethnic minority populations. Here, we document the prevalence, heritability, and genetic correlations between major depression and alcohol and drug disorders in a large, community-ascertained sample of Mexican-American families. A total of 1,122 Mexican-American individuals from 71 extended pedigrees participated in the study. All subjects received in-person psychiatric interviews. Heritability, genetic, and environmental correlations were estimated using SOLAR. Thirty-five percent of the sample met criteria for DSM-IV lifetime major depression, 34% met lifetime criteria for alcohol use disorders, and 8% met criteria for lifetime drug use disorders. The heritability for major depression was estimated to be h(2) = 0.393 (P = 3.7 × 10(-6)). Heritability estimates were higher for recurrent depression (h(2) = 0.463, P = 4.0 × 10(-6)) and early onset depression (h(2) = 0.485, P = 8.5 × 10(-5)). While the genetic correlation between major depression and alcohol use disorders was significant (ρ(g) = 0.58, P = 7 × 10(-3)), the environmental correlation between these traits was not significant. Although, there is evidence for increased rates of depression and substance use in US-born individuals of Mexican ancestry, our findings indicate that genetic control over major depression and alcohol/substance use disorders in the Mexican-American population is similar to that reported in other populations.

Behavioural phenotyping of knockout mice for the sigma-1 (σ₁) chaperone protein revealed gender-related anxiety, depressive-like and memory alterations

The sigma-1 (σ₁) protein regulates calcium homeostasis and acts as an endoplasmic reticulum chaperone. It can be activated by ligands which impact memory, depression, anxiety or addiction processes. We here characterized the behavioural phenotype of knockout (KO) mice for the σ₁ protein. Two-month old male σ₁⁻/⁻ mice showed signs of anxiety in the open-field, passive avoidance or elevated plus-maze test, but other activity or memory responses were unchanged. Female σ₁⁻/⁻ mice showed deficits in spontaneous alternation or water-maze learning. Twelve-month old σ₁⁺/⁻ female mice showed deficits in alternation and σ₁⁻/⁻ mice in avoidance escape latency. Two- and 14-month old female σ₁⁻/⁻ mice showed decreased plasma 17β-estradiol levels. Treatment with 17β-estradiol (0.1, 0.2 mg/kg i.p.) reversed the spatial memory deficits in young and aged mice. Male σ₁ KO mice showed enhanced response in the forced swimming test. Igmesine, a σ₁ agonist, failed to decrease immobility in σ₁ KO mice. Fluoxetine and sertraline were more efficient in σ₁ KO mice, an effect likely related to their σ₁ antagonist activity. Imipramine, desipramine and amitriptyline were equally active. σ₁ protein invalidation therefore affected stress or anxiety response but not memory in males. Changes in steroid tonus in female animals led, however, to memory impairments that increased with age.

Oxytocin receptor gene and depressive symptoms associated with physiological reactivity to infant crying

Both the oxytocin receptor (OXTR) gene and depressive symptoms have been associated with parenting behaviour. The OXTR GG genotype has been suggested to be related to more sensitive parenting, whereas depressive symptoms may affect sensitivity negatively. We examined the role of OXTR and the influence of depressive symptoms in explaining differences in physiological reactivity to infant crying. Heart rate responses of 40 healthy females without children (age 19-47 years, randomly selected half of twin pairs) were measured during the presentation of three episodes of infant cry sounds. Participants with the presumably more efficient variant of the oxytonergic system gene (OXTR GG) had more pronounced physiological reactivity to repeated cry sounds, except when they showed more symptoms of depression. Results were replicated in the second half of the twin sample. This is the first study to suggest effects of OXTR genotype on physiological reactivity to infant crying. Depressive symptoms may however suppress the effect of the OXTR GG genotype.

Behaviour of a genetic mouse model of depression in the learned helplessness paradigm

RATIONALE

H/Rouen (displaying a helpless phenotype in the tail suspension test) mice exhibiting features of depressive disorders and NH/Rouen (displaying non-helpless phenotype) mice were previously created through behavioural screening and selective breeding. Learned helplessness (LH), in which footshock stress induces a coping deficit, models some aspects of depression in rodents, but so far, fewer LH studies have been performed in mice than in rats.

OBJECTIVES

To study H/Rouen and NH/Rouen in the LH paradigm.

RESULTS

When CD1 mice were submitted to footshock with various training durations and shock intensities, the most suitable parameters to induce a behavioural deficit were 0.3 mA and four training sessions. A significantly longer latency to escape shocks was found in male H/Rouen mice compared to male NH/Rouen mice. On the other hand, once shocked, NH/Rouen mice showed more severe coping deficits than H/Rouen mice. In addition, a sub-chronic treatment with fluoxetine lacked efficacy in NH/Rouen mice, whereas it improved performances in H/Rouen mice. We also found that a shock reminder at day 8, subsequent to inescapable shocks, maintained helplessness for 20 days. Finally, female H/Rouen mice responded to chronic fluoxetine administration after 10 days of treatment, while a 20-day treatment was necessary to improve the behavioural deficit in H/Rouen male mice.

CONCLUSION

H/Rouen and NH/Rouen lines displayed different despair-related behaviour in the LH paradigm. Fluoxetine had beneficial effects after sub-chronic or chronic but not acute treatment of H/Rouen mice, thus providing a pharmacological validation of the protocols.

Revisiting the effect of marital support on depressive symptoms in mothers and fathers: a genetically informed study

This article uses a genetically informed design to evaluate whether (1) the well-documented association between marital support and depressive symptoms is accounted for by genetic and/or shared environmental selection, (2) gender differences are found after controlling for selection effects, and (3) parenthood moderates any nonshared environmental relation between depressive symptoms and marital support. We used a sample of 1,566 pairs of same-sexed, married twins from the Australian Twin Registry to evaluate our hypotheses that (1) the predicted effect of marital support on depressive symptoms is not fully an artifact of selection, (2) the etiological sources accounting for this effect differ between husbands and wives, and (3) parenthood status moderates the effect of marital support on depressive symptoms adjusting for selection effects. The results support the first hypotheses. However, after controlling for selection, the effect of marital support on depressive symptoms was not significantly different for husbands and wives. Parenthood moderated the effect of marital support, such that after controlling for selection, marital support is more strongly associated with depressive symptoms for full-time parents than nonfull-time parents.

Development by environment interactions controlling tryptophan hydroxylase expression

Tryptophan hydroxylase is the rate-limiting enzyme in the biosynthesis of serotonin (5-hydroxytryptamine; 5-HT). Two isoforms of tryptophan hydroxylase, derived from different genes, tph1 and tph2, have been identified. The tph1 isoform is expressed in peripheral tissues, whereas tph2 is brain and neuron-specific. Recent studies suggest that tph2 expression and brain serotonin turnover are upregulated in depressed suicide patients, and drug-free depressed patients, respectively. Increased tph2 expression could result from genetic influences, early life developmental influences, adverse experience during adulthood, or interactions among these factors. Studies in rodents support the hypothesis that interactions between early life developmental influences and adverse experience during adulthood play an important role in determining tph2 expression. In this review, we highlight the evidence for the effects of adverse early life experience and stressful experience during adulthood on both tph1 and tph2 expression.

[Effects of ginsenosides on hypothalamic-pituitary-adrenal function and brain-derived neurotrophic factor in rats exposed to chronic unpredictable mild stress]

Gingseng is commonly used in traditional Chinese medicine community for the treatment of depression-like disorders. Ginsenosides is considered to be the major active components of ginseng. Previous studies have demonstrated that ginsenosides produced antidepressant-like action in various mouse models of behavioral despair. The present study aimed to examine whether ginsenosides could affect the chronic unpredictable mild stress (CUMS)-induced depression in rats. The mechanism(s) underlying the antidepressant-like action was investigated by measuring serum corticosterone level, glucocorticoid receptor (GR), mineralocorticoid receptor (MR) and brain-derived neurotrophic factor (BDNF) mRNA levels in brain tissues. CUMS, being lasted for 6 weeks, caused depression-like behavior in rats, as indicated by the significant decrease in sucrose consumption and increase in immobility time in the forced swim test. Whereas serum corticosterone level was significantly increased in rats exposed to CUMS, expressions of GR mRNA in hippocampus, and BDNF mRNA in hippocampus and frontal cortex, were decreased in CUMS-treated rats. Daily intragastric administration of ginsenosides (12.5, 25, 50 mg x kg(-1)) during the six weeks of CUMS significantly suppressed behavioral and biochemical changes induced by CUMS. However, there was no significant difference in MR mRNA level among groups. The results suggest that the antidepressant-like action of ginsenosides is likely mediated by modulating the function of hypothalamic- pituitary -adrenal axis and increasing the expression of BDNF in brain tissues.