The Reality of Tonic Immobility in Victims of Sexual Violence: "I was Paralyzed, I Couldn't Move"

Tonic immobility (TI) is a state of temporary, involuntary motor inhibition that occurs in states of intense fear and has been studied among victims of sexual violence. Studies on TI are scarce and mainly focus on rape victims. The present study is a literature review of research that has examined TI in women victims of sexual violence. A database search was carried out using the Preferred data elements for systematic reviews and meta-analyses (PRISMA) method. In order to be included in the analysis, the manuscripts had to deal exclusively with research involving samples of subjects and the study analyzed TI in victims of sexual violence. In all, 11 manuscripts met the above criteria and were included in the review. Research describes that TI is characterized by two factors: fear and immobility. Quantitative research was conclusive in affirming the presence of a state of paralysis and fear in TI. The immobility factor is the determining factor in explaining the victim's lack of defense or resistance and causes effects such as trembling, physical and mental paralysis, inability to vocalize, and eye closure. In addition, TI has been correlated with long-term negative clinical manifestations as victims are more likely to suffer from post-traumatic stress disorder. These findings contribute to an understanding of TI in victims of sexual violence. Therefore, legal and care practitioners must be able to recognize TI to understand the victim's behavior, differentiate it from consent, and to be able to assist in their recovery.

Testing previously proposed models of the Tonic Immobility Scale in a peritraumatic sample of Israeli civilians: Support for a three-factor model

OBJECTIVE

Tonic immobility (TI) is a peritraumatic response to extreme threats. It is associated with trauma psychopathology and poor treatment outcomes. Yet, previous psychometric evaluations have yielded inconsistent results regarding the number of latent factors of the Tonic Immobility Scale (TIS). Moreover, the TIS has never been validated in a Hebrew-speaking population. This study had two objectives: (a) to reassess previously proposed models of the TIS to determine whether it is best represented by a one-factor model of TI, a two-factor model of TI and fear, or a three-factor model of TI, fear, and detachment; and (b) to validate the TIS in a Hebrew translation.

METHOD

A sample of Israeli adults was culled from an online survey following rocket attacks. Confirmatory factor analysis was applied to test the previously proposed models, and Pearson's correlations were used to test the association between each of the subscales representing the latent factors and psychological distress.

RESULTS

The best representation of the data was provided by a three-factor model with latent constructs of TI, fear, and detachment. All three peritraumatic responses had significant correlations with peritraumatic distress. Moreover, the internal consistency of the TIS was good for the three subscales; this supports the reliability of the Hebrew version.

CONCLUSION

This study supports using a three-factor model with latent constructs, and the scale appears to be psychometrically sound when translated into Hebrew. Future research should seek to replicate these findings in different trauma populations and should study the unique association of trauma symptomatology. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Differences among domestic chicken breeds in tonic immobility responses as a measure of fearfulness

Background

One priority for animal welfare is for animals to experience less fear, especially during human contact. For domestic animals, breeds that are less fearful may provide genetic resources to develop strains with improved welfare due to lower susceptibility to fear. Genetic predispositions inherited in these breeds might reflect the large diversity of chicken breeds. The goal of the present study was to systematically test a diverse group of chicken breeds to search for breeds that experience less fear.

Methods

Nineteen chicken breeds from commercial hybrid lines, native layer-type, meat-type and dual-purpose breeds, ornamental breeds as well as bantam breeds were tested in a standardized tonic immobility (TI) test. Chickens were manually restrained on their back, and the time to first head movement and first leg movement, the duration of TI, as well as the number of attempts needed to induce TI were measured.

Results

The TI response differed among chicken breeds (p ≤ 0.001) for naïve, mature hens. The median number of attempts required to induce TI ranged from 1 to 2 and did not differ significantly among breeds. Median durations were much more variable, with Lohmann Brown showing shortest durations (6 s, 12 s, 58 s for time to first head movement, first leg movement and total duration of TI, respectively). In contrast, medians reached the maximum of 600 s for all three measures in German Creepers. Repeated tests on the same individuals did not affect attempts needed to induce TI nor TI durations. Breeds clustered into two main groups, with layer-type native breeds and ornamental breeds having longer TI durations, and bantam, dual-purpose and meat-type native breeds having shorter TI durations.

Conclusions

Our findings provide evidence for substantial variation of fearfulness among breeds. This variation could be linked to the intended use during the breed's specific history. Knowledge and quantitative measurement of these behavioural responses provide the opportunity to improve welfare through selection and future breeding.

Genomic characterization between strains selected for death-feigning duration for avoiding attack of a beetle

Predator avoidance is an important behavior that affects the degree of adaptation of organisms. We compared the DNA variation of one of the predator-avoidance behaviors, the recently extensively studied "death-feigning behavior", between the long strain bred for feigning death for a long time and the short strain bred for feigning death for a short time. To clarify how the difference in DNA sequences between the long and short strains corresponds to the physiological characteristics of the death-feigning duration at the transcriptome level, we performed comprehensive and comparative analyses of gene variants in Tribolium castaneum strains using DNA-resequencing. The duration of death feigning involves many gene pathways, including caffeine metabolism, tyrosine metabolism, tryptophan metabolism, metabolism of xenobiotics by cytochrome P450, longevity regulating pathways, and circadian rhythm. Artificial selection based on the duration of death feigning results in the preservation of variants of genes in these pathways in the long strain. This study suggests that many metabolic pathways and related genes may be involved in the decision-making process of anti-predator animal behavior by forming a network in addition to the tyrosine metabolic system, including dopamine, revealed in previous studies.

Should Catatonia Be Conceptualized as a Pathological Response to Trauma?

ABSTRACT

Although catatonia is related to several medical conditions, catatonia as a response to trauma and posttraumatic stress disorder (PTSD) is less clear. The aim of this review is to explore the small emerging body of preliminary evidence that suggests a possible correlation between psychological trauma and catatonia. Initial data suggests a correlation between episodes of intense fear associated with trauma and PTSD and some forms of catatonic responses. Although this relationship is still speculative to be causative, it can have important implications if confirmed. This is especially salient when it is examined alongside existing studies of the response to fear in animals and the phenomenon of tonic immobility, which bears a striking resemblance to catatonia in humans. If prospective studies further support the initial findings, it could change our conceptual understanding of the etiology of a subtype of catatonia substantially while pointing to likely targets of further research to understand the biological mechanisms that underlie the illness.

Assaying Fear Memory Discrimination and Generalization: Methods and Concepts

Generalization describes the transfer of conditioned responding to stimuli that perceptually differ from the original conditioned stimulus. One arena in which discriminant and generalized responding is of particular relevance is when stimuli signal the potential for harm. Aversive (fear) conditioning is a leading behavioral model for studying associative learning and memory processes related to threatening stimuli. This article describes a step-by-step protocol for studying discrimination and generalization using cued fear conditioning in rodents. Alternate conditioning paradigms, including context generalization, differential generalization, discrimination training, and safety learning, are also described. The protocol contains instructions for constructing a cued fear memory generalization gradient and methods for isolating discrete cued-from-context cued conditioned responses (i.e., "the baseline issue"). The preclinical study of generalization is highly pertinent in the context of fear learning and memory because a lack of fear discrimination (overgeneralization) likely contributes to the etiology of anxiety-related disorders and post-traumatic stress disorder. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Tone cued fear generalization gradient Basic Protocol 2: Quantification of freezing Support Protocol: Alternate conditioning paradigms.

Aberrant Tonic Inhibition of Dopaminergic Neuronal Activity Causes Motor Symptoms in Animal Models of Parkinson's Disease

Current pharmacological treatments for Parkinson's disease (PD) are focused on symptomatic relief, but not on disease modification, based on the strong belief that PD is caused by irreversible dopaminergic neuronal death. Thus, the concept of the presence of dormant dopaminergic neurons and its possibility as the disease-modifying therapeutic target against PD have not been explored. Here we show that optogenetic activation of substantia nigra pars compacta (SNpc) neurons alleviates parkinsonism in acute PD animal models by recovering tyrosine hydroxylase (TH) from the TH-negative dormant dopaminergic neurons, some of which still express DOPA decarboxylase (DDC). The TH loss depends on reduced dopaminergic neuronal firing under aberrant tonic inhibition, which is attributed to excessive astrocytic GABA. Blocking the astrocytic GABA synthesis recapitulates the therapeutic effect of optogenetic activation. Consistently, SNpc of postmortem PD patients shows a significant population of TH-negative/DDC-positive dormant neurons surrounded by numerous GABA-positive astrocytes. We propose that disinhibiting dormant dopaminergic neurons by blocking excessive astrocytic GABA could be an effective therapeutic strategy against PD.

Distinct classes of low frequency ultrasonic vocalizations in rats during sexual interactions relate to different emotional states

This study examined low-frequency ultrasonic vocalizations (lUSVs) in rats during two types of sexual interactions; postejaculatory interval (PEI) and barrier - noncontact (NC) test. We report distinct classes of lUSVs that can be assigned to different emotional states; relaxation vs. frustration. Totally flat, 22-kHz calls (Class A), were observed during the relaxation state following ejaculation; characterized by immobilization or grooming during the PEI. On the other hand, two-three component lUSVs (Class B) that start at a higher frequency (45-kHz: flat, upward or short signal) and then shift to 35-23-kHz (mostly to 28-23-kHz), correspond as we assume, to arousal and frustration - active states associated with sniffing a hole or exploration during the NC test. We suggest that momentary, abrupt decreases of arousal during the frustration state correspond to Class B lUSVs. The detailed spectral analysis of the high-frequency component of two-component lUSVs is crucial for establishing the relationship between such lUSVs and the corresponding behavior and emotional states. Our studies indicate that while the two-component Class B 22-kHz lUSVs may relate to the frustration state, a single component, flat, Class A lUSV relates to the relaxation state. The results of these studies support a notion that rats emit distinct vocalization patterns, reflecting their emotional states.

Blockade of nicotinic acetylcholine receptor enhances the responsiveness to bupropion in the mouse forced swim test

The objective of the present study is to investigate the role of α4, α5, α6 or β2 nAChR subunits in the antidepressant-like effect of bupropion. Adult male mice were treated with subcutaneous acute doses of bupropion (3 and 10 mg/kg) 30 min before the forced swim test (FST) in α4, α5, α6, or β2 nAChR subunit knockout (KO) and wild-type (WT) mice. In addition, the effects of β2* antagonist dihydro-β-erythroidine (DHβE, 3 mg/kg) on antidepressant-like effects of bupropion in C57BL/6 J mice were assessed. Our results showed that baseline immobility and climbing time did not differ between KO and corresponding WT mice except for β2 KO. Bupropion significantly decreased immobility time and increased climbing time in the α4, α6 and β2 nAChR KO mice in comparison to WT littermates, indicating that lack of these nAChR subunits enhanced antidepressant effects of bupropion. On the contrary, the α5 nAChR subunit deletion did not alter the FST behavior in the bupropion-treated mice. Not only in the transgenic mice, bupropion also showed antidepressant-like effects in the WT mice. In addition, DHβE pretreatment before bupropion administration resulted in decreased immobility time and increased climbing time. Taken together, the present study provides evidence on the involvement of α4*, α6*, and β2* (* indicates possible presence of other subunits) nAChRs in the antidepressant-like effects of bupropion in the FST.

Incident experience predicts freezing-like responses in firefighters

Freezing is a defensive response to acute stress that is associated with coping and alterations in attentional processing. However, it remains unclear whether individuals in high risk professions, who are skilled at making rapid decisions in emergency situations, show altered threat-induced freezing. Here we investigated the effect of incident experience in a high risk profession on freezing. Additionally, we explored whether any effect of incident experience on freezing would be different for profession-related and -unrelated threat. Forty experienced and inexperienced firefighters were presented neutral, pleasant, related-unpleasant, and unrelated-unpleasant pictures in a passive viewing task. Postural sway and heart rate were assessed to determine freezing. Both postural and heart rate data evidenced reduced freezing upon unpleasant pictures in the experienced versus the inexperienced group. Relatedness of the unpleasant pictures did not modulate these effects. These findings indicate that higher incident experience relates to decreased threat-induced freezing, at least in a passive task context. This might suggest that primary defense responses are malleable through experience. Finally, these findings demonstrate the potential of using animal to human translational approaches to investigate defensive behaviors in relation to incident experience in high risk professions and stimulate future research on the role of freezing in resilience and coping.

The tonic immobility test: Do wild and captive golden mantella frogs (Mantella aurantiaca) have the same response?

Adaptations to captivity that reduce fitness are one of many reasons, which explain the low success rate of reintroductions. One way of testing this hypothesis is to compare an important behavioural response in captive and wild members of the same species. Thanatosis, is an anti-predator strategy that reduces the risk of death from predation, which is a common behavioral response in frogs. The study subjects for this investigation were captive and wild populations of Mantella aurantiaca. Thanatosis reaction was measured using the Tonic Immobility (TI) test, a method that consists of placing a frog on its back, restraining it in this position for a short period of time and then releasing it and measuring how much time was spent feigning death. To understand the pattern of reaction time, morphometric data were also collected as body condition can affect the duration of thanatosis. The significantly different TI times found in this study, one captive population with shorter responses, were principally an effect of body condition rather than being a result of rearing environment. However, this does not mean that we can always dismiss the importance of rearing environment in terms of behavioural skills expressed.

Amygdala inputs to prefrontal cortex guide behavior amid conflicting cues of reward and punishment

Orchestrating appropriate behavioral responses in the face of competing signals that predict either rewards or threats in the environment is crucial for survival. The basolateral nucleus of the amygdala (BLA) and prelimbic (PL) medial prefrontal cortex have been implicated in reward-seeking and fear-related responses, but how information flows between these reciprocally connected structures to coordinate behavior is unknown. We recorded neuronal activity from the BLA and PL while rats performed a task wherein competing shock- and sucrose-predictive cues were simultaneously presented. The correlated firing primarily displayed a BLA→PL directionality during the shock-associated cue. Furthermore, BLA neurons optogenetically identified as projecting to PL more accurately predicted behavioral responses during competition than unidentified BLA neurons. Finally photostimulation of the BLA→PL projection increased freezing, whereas both chemogenetic and optogenetic inhibition reduced freezing. Therefore, the BLA→PL circuit is critical in governing the selection of behavioral responses in the face of competing signals.

Microglial Acid Sensing Regulates Carbon Dioxide-Evoked Fear

BACKGROUND

Carbon dioxide (CO2) inhalation, a biological challenge and pathologic marker in panic disorder, evokes intense fear and panic attacks in susceptible individuals. The molecular identity and anatomic location of CO2-sensing systems that translate CO2-evoked fear remain unclear. We investigated contributions of microglial acid sensor T cell death-associated gene-8 (TDAG8) and microglial proinflammatory responses in CO2-evoked behavioral and physiological responses.

METHODS

CO2-evoked freezing, autonomic, and respiratory responses were assessed in TDAG8-deficient ((-/-)) and wild-type ((+/+)) mice. Involvement of TDAG8-dependent microglial activation and proinflammatory cytokine interleukin (IL)-1β with CO2-evoked responses was investigated using microglial blocker, minocycline, and IL-1β antagonist IL-1RA. CO2-chemosensitive firing responses using single-cell patch clamping were measured in TDAG8(-/-) and TDAG8(+/+) mice to gain functional insights.

RESULTS

TDAG8 expression was localized in microglia enriched within the sensory circumventricular organs. TDAG8(-/-) mice displayed attenuated CO2-evoked freezing and sympathetic responses. TDAG8 deficiency was associated with reduced microglial activation and proinflammatory cytokine IL-1β within the subfornical organ. Central infusion of microglial activation blocker minocycline and IL-1β antagonist IL-1RA attenuated CO2-evoked freezing. Finally, CO2-evoked neuronal firing in patch-clamped subfornical organ neurons was dependent on acid sensor TDAG8 and IL-1β.

CONCLUSIONS

Our data identify TDAG8-dependent microglial acid sensing as a unique chemosensor for detecting and translating hypercapnia to fear-associated behavioral and physiological responses, providing a novel mechanism for homeostatic threat detection of relevance to psychiatric conditions such as panic disorder.

Selective amotivation deficits following chronic psychosocial stress in mice

Amotivation is a major symptom of several psychiatric disorders. However, which specific motivations are most affected in various illnesses is not well understood. In major depressive disorder (MDD), anecdotal evidence suggests the motivation to explore may be especially affected, but direct evidence from either patients or animal models is lacking. To investigate the potential for, and nature of, exploratory drive deficits in MDD, we subjected mice to a chronic social defeat (CSD) manipulation that gives rise to a MDD-like behavioural ensemble, and performed a behavioural battery to examine bodyweight homeostasis, ambulation, anxiety, exploratory behaviour motivated by either novelty or fear, and short-term memory. Consistent with previous reports, we found a disruption of bodyweight homeostasis and reduced ambulation following CSD treatment, but we found no evidence for anxiogenic effects or impairments in short-term memory. Surprisingly, we also observed profoundly delayed and diminished exploration of novel, safe space following CSD, while exploration motivated by fear remained intact. These results extend our knowledge of the behavioural phenotypes in mice resulting from CSD by homing in on specific motivational drives. In MDD patients, reduced exploration could compound disease symptomatology by preventing engagement in what could be rewarding exploration experiences, and targeting deficits in the motivation to explore may represent a novel avenue for treatment.

The mesencephalic GCt-ICo complex and tonic immobility in pigeons (Columba livia): a c-Fos study

Tonic immobility (TI) is a response to a predator attack, or other inescapable danger, characterized by immobility, analgesia and unresponsiveness to external stimuli. In mammals, the periaqueductal gray (PAG) and deep tectal regions control the expression of TI as well as other defensive behaviors. In birds, little is known about the mesencephalic circuitry involved in the control of TI. Here, adult pigeons (both sex, n = 4/group), randomly assigned to non-handled, handled or TI groups, were killed 90 min after manipulations and the brains processed for detection of c-Fos immunoreactive cells (c-Fos-ir, marker for neural activity) in the mesencephalic central gray (GCt) and the adjacent nucleus intercollicularis (ICo). The NADPH-diaphorase staining delineated the boundaries of the sub nuclei in the ICo-GCt complex. Compared to non-handled, TI (but not handling) induced c-Fos-ir in NADPH-diaphorase-rich and -poor regions. After TI, the number of c-Fos-ir increased in the caudal and intermediate areas of the ICo (but not in the GCt), throughout the rostrocaudal axis of the dorsal stratum griseum periventriculare (SGPd) of the optic tectum and in the n. mesencephalicus lateralis pars dorsalis (MLd), which is part of the ascending auditory pathway. These data suggest that inescapable threatening stimuli such as TI may recruit neurons in discrete areas of ICo-GCt complex, deep tectal layer and in ascending auditory circuits that may control the expression of defensive behaviors in pigeons. Additionally, data indicate that the contiguous deep tectal SCPd (but not GCt) in birds may be functionally comparable to the mammalian dorsal PAG.

[Modification of the Rat Ethogram by Contagion Behavior]

The study was performed on a contagious behavior model based on drinking, behavior in rats. In the presence of familiar drink-motivated conspecific showing drinking behavior (rat-demonstrator), drink-unmotivated rat-viewer begins to demonstrate behavioral signs ofdrinking motivation that is the signs of behavioral contagion. In this paper; the changes in the ethogram of rats-viewers with behavioral contagion were studied by analyzing atransition probabilities matrix. Those animals showed a decrease in the frequency of aggression and defensive behavior patterns simultaneously with an increase in the frequency of exploratory activity, drinking and exploratory approaches to bottles as compared with the ethogram of rats-viewers with no signs of behavioral contagion when tested in the presence of familiar drink-unmotivated con specific-demonstrator.

Depressive-like immobility behavior and genotype × stress interactions in male mice of selected strains

In this study, we investigated whether basal immobility time of C57BL/6J mice, which are commonly used in transgenesis, interferes with detection of depressive-like behavior in the tail suspension test (TST) after chronic restraint stress (CRS). We included in the study mice of the C57BL/6N strain, not previously compared with C57BL/6J for behavior in the TST, and contrasted both strains with NMRI mice which exhibit low basal immobility. NMRI, C57BL/6J, and C57BL/6N male mice (n = 20 per strain) were tested under basal conditions and after CRS (2 h daily for 14 d). NMRI and C57BL/6J mice were differentiated in the TST by low and high basal immobility times, respectively, while the C57BL/6N and NMRI mice showed similar levels of basal immobility. CRS extended the immobility time of NMRI mice in the TST, whereas both C57BL/6J and C57BL/6N mice were unaffected regardless of their initial phenotype. We explored whether detailed analysis of activity microstructure revealed effects of CRS in the TST, which are not apparent in the overall comparison of total immobility time. Interestingly, unlike C57BL/6J and/6N strains which showed no sensitivity to CRS, stressed NRMI mice displayed distinct activity microstructure. In contrast to behavioral differences, all stressed mice showed significant retardation in body weight gain, decreased thymus weight and increased adrenal cortex size. However, after CRS, enlargement of the adrenal medulla was observed in both C57BL/6J and C57BL/6N mice, suggesting similar sympatho-medullary activation and stress coping mechanism in these substrains.

Imipramine protects against the deleterious effects of chronic corticosterone on depression-like behavior, hippocampal reelin expression, and neuronal maturation

We have hypothesized that a downregulation of reelin and deficient maturation of adult-born hippocampal neurons are important factors in the pathogenesis of depression. This hypothesis is based on previous work showing that depression-like behavior in rats treated with protracted corticosterone develops in concert with decreased dendritic complexity in newborn hippocampal granule neurons and decreased reelin expression in the proliferative subgranular zone of the dentate gyrus. In addition, heterozygous reeler mice with approximately 50% of normal brain levels of reelin are more vulnerable to the depressogenic effects of corticosterone than wild-type mice. The purpose of this experiment was to provide pharmacological validation for the link between reelin, neuronal maturation, and depression by examining whether the deleterious effects of corticosterone on these measures could be prevented by co-administration of the antidepressant imipramine. Rats received corticosterone injections, corticosterone injections plus either 10 or 15mg/kg imipramine injections, or vehicle injections for 21 consecutive days. They were then subjected to the forced swim test to assess depression-like behavior and sacrificed for immunohistochemical examination of immature neuron number and dendritic complexity and the presence of reelin+cells. We found that corticosterone increases depression-like behavior, decreases the number of reelin+cells in the subgranular zone, and decreases the number and complexity of immature neurons in the granule cell layer. All of these behavioral and cellular phenotypes were prevented by imipramine, providing further support for the idea that reelin is involved in the pathogenesis of depression.

Differential expression of hypothalamic fear- and stress-related genes in broiler chickens showing short or long tonic immobility

The serotonin system and the hypothalamic-pituitary-adrenal axis play important roles in modulating fear and stress-coping characteristics. Tonic immobility (TI) is a fear-related phenotype, and previously we have shown that broiler chickens showing short TI (STI) duration experience better growth performance and higher adaptability to stress. Here, we sought to further elucidate the central mechanisms underlying the phenotypic differences between chickens showing STI and long TI duration, by comparing the hypothalamic expression of genes in the serotonergic system and the hypothalamic-pituitary-adrenal axis under basal and corticosterone-exposed situations. The STI broilers had significantly lower (P < 0.01) hypothalamic expression of serotonin reuptake transporter and serotonin receptor 1A. Moreover, 11β-hydroxysteroid dehydrogenase type 2 was expressed significantly lower in STI chickens at the level of both mRNA (P < 0.01) and protein (P < 0.05). Hypothalamic expression of glucocorticoid receptor (GR) mRNA tended to be higher (P < 0.059) in long TI chickens, but the protein content was approximately 2 times higher (P < 0.01) in STI chickens. The uncoupled expression of GR mRNA and protein was associated with significantly lower (P < 0.05) expression of gga-miR-181a, gga-miR-211, and gga-miR-22, which are predicted to target GR, in STI chickens. Corticosterone administration reduced the mRNA expression of postsynaptic serotonin receptors, 5-hydroxytryptamine receptor 1B (P = 0.059) and 5-hydroxytryptamine receptor 7 (P < 0.05), yet significantly increased the protein content of 11β-hydroxysteroid dehydrogenase type 2 (P < 0.05). These results suggest that broilers of different TI phenotypes have a distinct pattern of hypothalamic expression of fear- and stress-related genes.

Role of prefrontal cortex glucocorticoid receptors in stress and emotion

BACKGROUND

Stress-related disorders (e.g., depression) are associated with hypothalamic-pituitary-adrenocortical axis dysregulation and prefrontal cortex (PFC) dysfunction, suggesting a functional link between aberrant prefrontal corticosteroid signaling and mood regulation.

METHODS

We used a virally mediated knockdown strategy (short hairpin RNA targeting the glucocorticoid receptor [GR]) to attenuate PFC GR signaling in the rat PFC. Adult male rats received bilateral microinjections of vector control or short hairpin RNA targeting the GR into the prelimbic (n = 44) or infralimbic (n = 52) cortices. Half of the animals from each injection group underwent chronic variable stress, and all were subjected to novel restraint. The first 2 days of chronic variable stress were used to assess depression- and anxiety-like behavior in the forced swim test and open field.

RESULTS

The GR knockdown confined to the infralimbic PFC caused acute stress hyper-responsiveness, sensitization of stress responses after chronic variable stress, and induced depression-like behavior (increased immobility in the forced swim test). Knockdown of GR in the neighboring prelimbic PFC increased hypothalamic-pituitary-adrenocortical axis responses to acute stress and caused hyperlocomotion in the open field, but did not affect stress sensitization or helplessness behavior.

CONCLUSIONS

The data indicate a marked functional heterogeneity of glucocorticoid action in the PFC and highlight a prominent role for the infralimbic GR in appropriate stress adaptation, emotional control, and mood regulation.

Evidences for the agmatine involvement in antidepressant like effect of bupropion in mouse forced swim test

Although bupropion has been widely used in the treatment of depression, the precise mechanism of its therapeutic actions is not fully understood. The present study investigated the role of agmatine in an antidepressant like effect of bupropion in mouse forced swim test. The antidepressant like effect of bupropion was potentiated by pretreatment with agmatine (10-20mg/kg, ip) and by the drugs known to increase endogenous agmatine levels in brain viz., l-arginine (40 μg/mouse, icv), an agmatine biosynthetic precursor, ornithine decarboxylase inhibitor, dl-α-difluoromethyl ornithine hydrochloride, DFMO (12.5 μg/mouse, icv), diamine oxidase inhibitor, aminoguanidine (6.5 μg/mouse, icv) and agmatinase inhibitor, arcaine (50 μg/mouse, icv) as well as imidazoline I1 receptor agonists, moxonidine (0.25mg/kg, ip) and clonidine (0.015 mg/kg, ip) and imidazoline I2 receptor agonist, 2-(2-benzofuranyl)-2-imidazoline hydrochloride, 2-BFI (5mg/kg, ip). Conversely, prior administration of I1 receptor antagonist, efaroxan (1mg/kg, ip) and I2 receptor antagonist, idazoxan (0.25mg/kg, ip) blocked the antidepressant like effect of bupropion and its synergistic combination with agmatine. These results demonstrate involvement of agmatine in the antidepressant like effect of bupropion and suggest agmatine and imidazoline receptors as a potential therapeutic target for the treatment of depressive disorders.

Comparison of the long-term consequences of withdrawal from repeated amphetamine exposure in adolescence and adulthood on information processing and locomotor sensitization in mice

Repeated administration of the indirect dopamine receptor agonist amphetamine (AMPH) produces robust locomotor sensitization and additional behavioral abnormalities. Accumulating evidence suggests that the developmental timing of drug exposure can critically influence this effect. The present study compared the consequences of withdrawal from repeated AMPH exposure in adolescence and adulthood on information processing and locomotor sensitization in C57BL/6 mice. Animals were injected daily with AMPH (1 or 2.5 mg/kg) or vehicle on 7 consecutive days starting either from postnatal day 35 to 42, or from postnatal day 70 to 77, following which they were given a 4 week withdrawal period before behavioral and pharmacological testing commenced. We found that withdrawal from the higher dose of AMPH (2.5 mg/kg/day) given either in adolescence or adulthood similarly disrupted selective associative learning as measured by the latent inhibition paradigm. None of the AMPH withdrawal groups displayed alterations in sensorimotor gating in the form of prepulse inhibition. Withdrawal from adult AMPH exposure at both doses induced marked locomotor sensitization, whereas adolescent pre-treatment with the higher (2.5 mg/kg/day) but not lower (1 mg/kg/day) dose of AMPH potentiated the locomotor-enhancing effects of acute AMPH re-challenge. Our study suggests that withdrawal from repeated AMPH exposure in adolescence and adulthood has similar consequences on selective associative learning, but the two manipulations differ with respect to their efficacy to induce long-term locomotor sensitization to the drug. The latter finding supports the hypothesis that the precise developmental timing determines, at least in part, the impact on long-term dopamine-associated sensitization processes.

Responses of brain and behavior to changing day-length in the diurnal grass rat (Arvicanthis niloticus)

Seasonal affective disorder (SAD) is a major depressive disorder that recurs in the fall and winter when day-length gets short. It is well accepted that day-length is encoded by the principal circadian clock located in the suprachiasmatic nucleus (SCN), but very little is known about day-length encoding in diurnal mammals. The present study utilized the grass rat, Arvicanthis niloticus, to investigate how the circadian system responds to photoperiodic changes in a diurnal mammal that shows day-length-dependent mood changes. The animals were initially housed in equatorial day-length (12h, EP) followed by either long (16h, LP) or short (8h, SP) photoperiods. The LP animals showed an expansion of the peak phase of the PER1 and PER2 rhythm in the SCN as well as an extended behavioral active phase. In contrast, the SP animals did not show any compression of their active phase nor a change in the peak duration of PER1 or PER2 expression, compared to those in EP. The results suggest that the circadian system in the diurnal grass rats is less responsive when day-length gets short compared to when it gets longer. The depression-like behaviors were assessed using sweet solution preference (SSP) and forced swimming test (FST). Animals in the SP group showed decreased SSP and increased immobility time in FST as compared to the EP group, suggesting a depressive phenotype. The present study serves as the first step toward exploring the role that the circadian system plays in SAD using a diurnal rodent model.

Japanese quail's genetic background modulates effects of chronic stress on emotional reactivity but not spatial learning

Chronic stress is known to enhance mammals' emotional reactivity and alters several of their cognitive functions, especially spatial learning. Few studies have investigated such effects in birds. We investigated the impact of a two-week stress on Japanese quail's emotional reactivity and spatial learning. Quail is an avian model widely used in laboratory studies and for extrapolation of data to other poultry species. As sensitivity to chronic stress can be modulated by intrinsic factors, we tested juvenile female Japanese quail from three lines, two of them divergently selected on tonic immobility duration, an indicator of general fearfulness. The different emotional reactivity levels of quail belonging to these lines can be revealed by a large variety of tests. Half of the birds were submitted to repeated unpredictable aversive events for two weeks, whereas the other half were left undisturbed. After this procedure, two tests (open field and emergence tests) evaluated the emotional reactivity of treated and control quails. They were then trained in a T-maze for seven days and their spatial learning was tested. The chronic stress protocol had an impact on resting, preening and foraging in the home cage. As predicted, the emotional reactivity of treated quails, especially those selected for long tonic immobility duration, was higher. Our spatial learning data showed that the treatment enhanced acquisition but not memorization. However, intrinsic fearfulness did not seem to interact with the treatment in this test. According to an inverted U-shaped relationship between stress and cognition, chronic stress can improve the adaptability of birds to a stressful environment. We discussed the mechanisms possibly implied in the increase of emotional reactivity and spatial abilities.

Voluntary exercise offers anxiolytic potential and amplifies galanin gene expression in the locus coeruleus of the rat

Although exercise improves anxiety in humans, it is controversial whether exercise is anxiolytic in rodents. We tested the hypothesis that stress influences the effect of exercise on anxiety-like and defensive behaviors. To explore the neurobiological mechanisms of exercise, we also examined whether exercise alters gene expression for the stress-related peptide galanin. Rats were housed in the presence or absence of a running wheel for 21 d. A subset of these rats were (1) not injected or received a single high, dose of the β-carboline FG7142 (inverse agonist at the benzodiazepine receptor site) immediately prior to testing or (2) were injected repeatedly with vehicle or FG7142 during the last 10d of exercise. On day 22, anxiety-like and defensive behaviors were measured in the elevated plus maze, shock probe defensive burying, and defensive withdrawal tests. Locus coeruleus prepro-galanin mRNA was measured by in situ hybridization. Exercise and sedentary rats that were not injected exhibited similar behavior in all tests, whereas FG7142 injected immediately prior to the test battery produced intense avoidance and immobility consistent with an anxiety-like response. However, exercise produced anxiolytic-like and active defensive behaviors in the test battery relative to the sedentary condition in rats injected repeatedly with vehicle or FG7142. Exercise also increased prepro-galanin mRNA in the locus coeruleus relative to sedentary controls. These data suggest that the emergence of enhanced adaptive behavior after chronic voluntary exercise is influenced by stress. Our data support a role for galanin in the beneficial consequences of wheel running.

Sex comparison on long-lasting behavioral and physiological disturbances induced by single shock experience in rats

Enhanced female vulnerability and symptom severity are described in post-traumatic stress disorder (PTSD). It remains largely unknown whether females present with more pronounced PTSD-like symptoms than males in rodent models of PTSD. A model of single electric foot-shock followed by situational reminders was used to investigate in rats the impact of sex on potential long-lasting changes in anxiety-like behavior, and in endocrine and physiological responses to stress and fearful situations. Three weeks after single shock exposure (in the dark side of a shuttle box) both male and female rats spent less time in the dark compartment of a dark-light box and in the closed arms of an elevated plus maze than non-shocked controls. Both behaviors were likely due to avoidance of places reminiscent of the initial shock context. The shock exposure had no long-term impact on social interaction behavior or on basal and restraint stress-induced increases in plasma corticosterone. Shock exposure increased sudden silence-induced freezing responses and hyperthermia during novelty stress and fear to a similar extent in both males and females and left heart rate responses unaffected. Non-shocked females generally showed a reduced response or faster recovery to baseline under stress- or fearful test conditions as compared to non-shocked males, which was likely due to differential sex-specific coping strategies. Taken together, our results suggest that, despite some baseline sex differences, both male and female rats are similarly affected in the long-term by the initial foot-shock exposure used in this particular simulation of PTSD.

Comparison of the effects of estradiol and progesterone on serotonergic function

BACKGROUND

Ovarian hormones may contribute to the vulnerability to depression, as well as to the response to antidepressants (ADs). Previously, we reported that acute systemic treatment with estradiol or progesterone blocked the ability of the selective serotonin reuptake inhibitor, fluvoxamine, to inhibit serotonin transporter function in ovariectomized rats. In this study, behavioral consequences, as well as receptor mechanisms underlying these hormonal effects, were investigated.

METHODS

Using the forced swimming test, the acute effect of estradiol and/or progesterone on fluvoxamine's AD-like effects was investigated. Using in vivo chronoamperometry, the effect of local application of estradiol or progesterone into the hippocampus of ovariectomized rats on serotonin (5-HT) clearance, as well as on the ability of fluvoxamine to slow 5-HT clearance, were investigated.

RESULTS

The decreased immobility and increased swimming caused by fluvoxamine in the forced swimming test was blocked in rats treated with estradiol and/or progesterone. Local application of estradiol, but not progesterone, slowed 5-HT clearance and both hormones blocked the ability of fluvoxamine to slow 5-HT clearance. Use of hormone receptor agonists and antagonists, revealed that the effects of estradiol are mediated by activation of membrane, as well as nuclear estrogen receptors (ER). The AD-like effect of estradiol involved ER beta and G-protein coupled receptor 30, whereas its blockade of fluvoxamine's effects was ER alpha-mediated. The effects of progesterone occurred solely by activation of intracellular progesterone receptors.

CONCLUSIONS

Targeting of ER beta or G-protein coupled receptor 30 might reveal a strategy to permit beneficial effects of estrogen without its deleterious effect on selective serotonin reuptake inhibitor efficacy.

Social isolation in adolescence alters behaviors in the forced swim and sucrose preference tests in female but not in male rats

Social interactions in rodents are rewarding and motivating and social isolation is aversive. Accumulating evidence suggests that disruption of the social environment in adolescence has long-term effects on social interactions, on anxiety-like behavior and on stress reactivity. In previous work we showed that adolescent isolation produced increased reactivity to acute and to repeated stress in female rats, whereas lower corticosterone responses to acute stress and decreased anxiety-related behavior were noted in isolated males. These results indicate a sex specific impact on the effects of social stress in adolescence. However, little is known about whether social isolation impacts behaviors related to affect and whether it does so differently in male and female rats. The present study investigated the impact of adolescent social isolation from day 30-50 of age in male and female Sprague Dawley rats on behavior in the forced swim test at the end of adolescence and in adulthood and on behavior in the sucrose preference test in adulthood. Adult female rats that were isolated in adolescence exhibited increased climbing on the first and second day of the forced swim test and showed an increased preference for sucrose compared to adult females that were group-housed in adolescence. There were no effects in male rats. The results indicate that social isolation in adolescence produces a stable and active behavioral phenotype in adult female rats.

Corticosterone microinjected into nucleus pontis oralis increases tonic immobility in rats

Tonic immobility (TI) is also known as "immobility response", "immobility reflex", "animal hypnosis", etc. It is an innate antipredatory behavior characterized by an absence of movement, varying degrees of muscular activity, and a relative unresponsiveness to external stimuli. Experimentally, TI is commonly produced by manually forcing an animal into an inverted position and restraining it in that position until the animal becomes immobile. Part of the neural mechanism(s) of TI involves the medullo-pontine reticular formation, with influence from other components of the brain, notably the limbic system. It has been observed that TI is more prolonged in stressed animals, and systemic injection of corticosterone (CORT) also potentiates this behavior. At present, the anatomical brain regions involved in the CORT modulation of TI are unknown. Thus, our study was made to determine if some pontine areas could be targets for the modulation of TI by CORT. A unilateral nucleus pontis oralis (PnO) microinjection of 1 μL of CORT (0.05 μg/1 μL) in rats resulted in clear behavioral responses. The animals had an increased duration of TI caused by clamping the neck (in this induction, besides of body inversion and restraint, there is also clamping the neck), with an enhancement in open-field motor activity, which were prevented by pretreatment injection into PnO with 1 μL of the mineralocorticoid-receptor antagonist spironolactone (0.5 μg/1 μL) or 1 μL of the glucocorticoid-receptor antagonist mifepristone (0.5 μg/1 μL). In contrast, these behavioral changes were not seen when CORT (0.05 μg/1 μL) was microinjected into medial lemniscus area or paramedian raphe. Our data support the idea that, in stressful situations, glucocorticoids released from adrenals of the prey reach the PnO to produce a hyper arousal state, which in turn can prolong the duration of TI.

Age increases anxiety and reactivity of the fear/anxiety circuit in Lewis rats

A growing body of data indicates that changes in emotional behavior occur with age. Young Lewis rats are known to display hypofunction of the HPA axis. With age the reactivity of this axis is thought to increase with a concomitant rise in anxiety. In the current study, we investigate how and if the pattern of neuronal activation (measured as c-Fos protein expression) in Lewis rat brains changes with age and in response to novel environments differing in aversiveness. We found that distinct parts of the fear/anxiety circuit (i.e., the amygdalar complex, hippocampus and hypothalamus) undergo diverse age-related changes in response to behavioral challenges. While in the hypothalamus an increase in responsivity to mild stressors was observed with age, no such effect was present in the hippocampus. The amygdalar complex (especially the medial and cortical nuclei) on the other hand exhibited an age-dependent decrease in neuronal activation to mild stressors. This was accompanied by a marked increase in anxiety not correlated with a decline in locomotor activity.

Activation of corticotropin-releasing factor receptors from the basolateral or central amygdala increases the tonic immobility response in guinea pigs: an innate fear behavior

The tonic immobility (TI) behavior is an innate response associated with extreme threat situations such as a predator attack. Several studies have provided evidence suggesting an important role for corticotropin-releasing factor (CRF) in the regulation of the endocrine system, defensive behaviors and behavioral responses to stress. TI has been shown to be positively correlated with the basal plasma levels of corticosterone. CRF receptors and neurons that are immunoreactive to CRF are found in many cerebral regions, especially in the amygdaloid complex. Previous reports have demonstrated the involvement of the basolateral amygdaloid (BLA) and central amygdaloid (CeA) nuclei in the TI response. In this study, we evaluated the CRF system of the BLA and the CeA in the modulation of the TI response in guinea pigs. The activation of CRF receptors in the BLA and in the CeA promoted an increase in the TI response. In contrast, the inhibition of these receptors via alpha-helical-CRF(9-41) decreased the duration of the TI response. Moreover, neither the activation nor inhibition of CRF receptors in the BLA or the CeA altered spontaneous motor activity in the open-field test. These data suggest that the activation of the CRF receptors in the BLA or the CeA probably potentiates fear and anxiety, which may be one of the factors that promote an increase in the TI behavior. Therefore, these data support the role of the CRF system in the control of emotional responses, particularly in the modulation of innate fear.

Differential effects of social defeat in rats with high and low locomotor response to novelty

We compared the response to repeated social defeat in rats selected as high (HR) and low (LR) responders to novelty. In experiment 1, we investigated the behavioral and neuroendocrine effects of repeated social defeat in HR-LR rats. By the last defeat session, HR rats exhibited less passive-submissive behaviors than LR rats, and exhibited higher corticosterone secretion when recovering from defeat. Furthermore, in the forced swim test, while HR defeated rats spent more time immobile than their undefeated controls, LR rats' immobility was unaffected by defeat. In experiment 2, we compared the effects of repeated social defeat on body, adrenal, thymus, and spleen weights in HR-LR rats; moreover, we compared the effects of repeated social defeat on stress related molecules gene expression in these two groups of rats. Our results show that HR rats exhibited a decrease in thymus weight after repeated social defeat that was not present in LRs. Analyses of in situ hybridization results found HR-LR differences in 5-HT(2a) mRNA levels in the parietal cortex and 5-HT(1a) mRNA levels in the dorsal raphe. Moreover, LR rats had higher glucocorticoid receptor (GR) mRNA expression than HR rats in the dentate gyrus, and repeated social defeat decreased this expression in LR rats to HR levels. Finally, hippocampal mineralcorticoid receptor (MR)/GR ratio was reduced in HR rats only. Taken together, our results show a differential response to social defeat in HR-LR rats, and support the HR-LR model as a useful tool to investigate inter-individual differences in response to social stressors.

Correlations between neuron activity in the sensorimotor cortex of the right and left hemispheres in rabbits during a defensive dominant and "animal hypnosis"

A latent focus of excitation with a rhythmic nature (a defensive dominant focus) was created in the CNS of rabbits. The focus was formed by threshold electrocutaneous stimulation of the left forelimb using series of impulses consisting of 15-20 stimuli with interstimulus intervals of 2 sec. The linked activity of cells in the sensorimotor cortex of the right and left hemispheres was analyzed. When cross-correlation histograms of the spike activity of sensorimotor cortex neurons in the left hemisphere were constructed and analyzed in relation to spikes of high and intermediate amplitude recorded in the right hemisphere, the linked activity of 15% and 23% of neuron pairs, respectively, showed predominance of a rhythm equal or close to the stimulation rhythm used to form the dominant focus. When the appearance times of spikes from neurons in the sensorimotor cortex of the right hemisphere were analyzed in relation to spikes of high and intermediate amplitude recorded in the cortex of the left hemisphere, predominance of 2-sec rhythms was seen in the linked activity of only 3% and 10% of neuron pairs, respectively. After induction of "animal hypnosis," differences between the hemispheres in relation to this measure leveled out.

Dynamics of changes in electrical activity in the rabbit cerebral cortex during sequential sessions of "animal hypnosis"

The dynamics of changes in individual electrical activity rhythms in the premotor, sensorimotor, and temporal-parietal areas of the cortex in both hemispheres were studied in chronic experiments in rabbits during sequential sessions of "animal hypnosis." These experiments showed that during the first session of "animal hypnosis," significant changes in electrical activity occurred only in the premotor area of the cortex of the right hemisphere, where there were increases in spectral power in the delta-1 and delta-2 ranges and decreases in spectral power in other ranges of electrical activity. Subsequent sessions of "animal hypnosis" formed increasing changes in electrical activity, which were particularly marked in cortical areas in the right hemisphere. Significant changes in spectral power in the delta and theta ranges of electrical activity in cortical areas did not arise at the beginning of the hypnotic state, but after 4-6 min. During the third session of "animal hypnosis," the course of electrical activity in the alpha and beta rhythms in the premotor and sensorimotor areas of the cortex became wave-like in nature.

Biogenic amines, caffeine and tonic immobility in Tribolium castaneum

Biogenic amines are physiologically neuroactive substances that affect behavioural and physiological traits in invertebrates. In the present study, the effects of dopamine, octopamine, tyramine and serotonin on tonic immobility, or death-feigning, were investigated in Tribolium castaneum. These amines were injected into the abdomens of beetles artificially selected for long or short duration of tonic immobility. In beetles of the long strains, the durations of tonic immobility were shortened by injection of dopamine, octopamine and tyramine, and the effects of these amines were dose-dependent. On the other hand, serotonin injection did not affect the duration of tonic immobility. In the short-strain beetles that rarely feign death, no significant effects of the amines were found on the duration of tonic immobility. Brain expression levels of octopamine, tyramine and serotonin did not differ between long- and short-strain beetles, in contrast to the higher dopamine levels in short strains previously reported. Caffeine decreased the duration of death-feigning in both oral absorption and injection experiments. It is known that caffeine activates dopamine. Therefore, the present results suggest that the duration of tonic immobility is affected by dopamine via the dopamine receptor in T. castaneum.

Depressive-like-behavior and proinflamatory interleukine levels in the brain of rats submitted to pneumococcal meningitis

Bacterial meningitis due to Streptococcus pneumoniae is associated with a significant mortality rate and persisting neurologic sequelae including sensorymotor deficits, seizures, and impairments of learning and memory. The presence of proliferating bacteria within the subarachnoid and ventricular space compartments triggers an intense inflammatory host response. Proinflammatory mediators released in the process include tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and all of which have been shown to contribute to the development of brain injury in bacterial meningitis. The animals underwent a magna cistern tap receiving either 10muL sterile saline as a placebo or an equivalent volume of a S. pneumoniae suspension at the concentration 5x10(9)cfu/mL. Ten days after induction we evaluated depressive-like behavior by using the forced swimming test and verified the levels of the TNF-alpha, IL-1beta, IL-6 and CINC-1 in the brain of rats induced to pneumococcal meningitis. In the forced swimming test we observed a significant increase in the immobility time in the meningitis group compared to the sham group (p<0.05). The TNFlevels were found increased in the prefrontal cortex (p<0.05, F=4.921), but not hippocampus. The IL-6, CINC-1 and IL-1beta levels presented no alteration in both prefrontal cortex and hippocampus 10 days after meningitis induction by S. pneumoniae. These findings suggest that the meningitis model could be a good research tool for the study of the biological mechanisms involved in the behavioral alterations secondary to pneumococcal meningitis.

[Interaction of stationary excitation foci in the rabbit brain]

Influence of "animal hypnosis" on the motor polarization dominanta created by direct anodic current applied on the left sensorimotor cortex of the rabbit ("left" dominanta) was studied in chronic experiments. Animal behavior and electrophysiological characteristics were recorded. It was impossible to elicit the "animal hypnosis" during the optimum of the "left" dominanta. The state of "animal hypnosis" could be easily elicited against the background of the latent focus of the "left" dominanta on the next day after its formation. The "animal hypnosis" restored the "left" dominanta after its extinction. It was accompanied by formation of a new pattern of the cortical EEG coherence in the delta range, which was different from the patterns characteristic of each kind of dominanta. After the "animal hypnosis" session, the formation of the "left" dominanta produced two kinds of nonstable foci. During testing, the "left" dominanta reached its optimum and then inhibited the tonic activity of the right forelimb characteristic of the "animal hypnosis". The interaction of the "animal hypnosis" and the dominant foci in the left and right sensorimotor cortex were different.

[Correlations of activity of neurons of sensorimotor cortex of the right and left brain hemispheres of rabbits during defensive dominant and "animal hypnosis"]

A hidden excitation focus of the rhythmic nature (a rhythmic defensive dominant focus) was produced in the rabbit's CNS. The focus was formed by means of threshold electrodermal stimulation of the left forelimb by series of pulses consisting of 15-20 stimuli with 2 s intervals between the pulses. Correlated activity of cells in the sensorimotor cortex of the right and left brain hemispheres was analyzed. In cases when crosscorrelation histograms were constructed by the results of the analysis of discharges of the left-side cortical of neurons regarding high- and middle-amplitude pulses in a right hemisphere, 15 and 23 % of correlated neural pairs, respectively, revealed the prevalence of the rhythm identical or close to the initial rhythm of stimulation that formed the hidden excitation focus. In contrast, in cases when the same analysis was applied to the right-side cortical neurons regarding high- and middle-amplitude discharges in the left hemisphere, prevalence of the dominant 2-second rhythm was revealed in correlated activity of only 3 and 10% of neural pairs, respectively. After the exposure to "animal hypnosis" procedure, the distinctions between the brain in this parameter were eliminated.

Ankle exercise and venous blood velocity

Ankle exercise increases venous blood velocity while supine, but the effect of ankle exercise on venous blood velocity while sitting is not known. In this investigation, we test the hypothesis that venous blood velocity can be increased while sitting by repetitive dorsiflexion of the foot. Time-averaged peak velocity (TAPV) in the popliteal vein of 20 healthy male volunteers was measured by pulsed Doppler ultrasound at rest and during ankle exercise in the supine and sitting positions. Right popliteal vein TAPV while supine at rest was 11 cm/second (sec) (95% confidence interval [CI] =9-13 cm/sec) and with ankle exercise it increased to 24 cm/sec (95% CI =20-28 cm/sec) (p<0.0001). With sitting at rest, right popliteal vein blood TAPV decreased from 11 cm/sec to 3 cm/sec (95% CI = 2-4 cm/sec) (p<0.0001). With ankle exercise while sitting, right popliteal vein TAPV increased to 18 cm/sec (95% CI =15-21 cm/sec) (p<0.0001). In conclusion, in both the supine and sitting positions, ankle exercise increased venous blood velocity, thereby transiently reducing a tendency toward venous stasis. Such ankle exercise might be useful in the prevention of stasis-induced deep venous thrombosis.

Interferon-gamma and tumor necrosis factor-alpha mediate the upregulation of indoleamine 2,3-dioxygenase and the induction of depressive-like behavior in mice in response to bacillus Calmette-Guerin

Although the tryptophan-degrading enzyme, indoleamine 2,3-dioxygenase (IDO), is a pivotal mediator of inflammation-induced depression, its mechanism of regulation has not yet been investigated in this context. Here, we demonstrate an essential role for interferon (IFN)gamma and tumor necrosis factor (TNF)alpha in the induction of IDO and depressive-like behaviors in response to chronic immune activation. Wild-type (WT) control mice and IFNgammaR(-/-) mice were inoculated with an attenuated form of Mycobacterium bovis, bacille Calmette-Guérin (BCG). Infection with BCG induced an acute episode of sickness that was similar in WT and IFNgammaR(-/-) mice. Increased immobility during the forced swim and tail suspension tests occurred in WT mice 7 d after BCG inoculation but was entirely absent in IFNgammaR(-/-) mice. In WT mice, these indices of depressive-like behavior were associated with chronic upregulation of IFNgamma, interleukin(IL)-1beta, TNFalpha, and IDO. Proinflammatory cytokine expression was elevated in BCG-infected IFNgammaR(-/-) mice as well, but upregulation of lung and brain IDO mRNA was completely abolished. This was accompanied by an attenuation of BCG-induced TNFalpha mRNA and the lack of an increase in plasma kynurenine/tryptophan ratio in the BCG-inoculated IFNgammaR(-/-) mice compared with WT controls. Pretreatment of mice with the TNFalpha antagonist, etanercept, partially blunted BCG-induced IDO activation and depressive-like behavior. In accordance with these in vivo data, IFNgamma and TNFalpha synergized to induce IDO in primary microglia. Together, these data demonstrate that IFNgamma, with TNFalpha, is necessary for induction of IDO and depressive-like behavior in mice after BCG infection.

[The dynamics of modification of electrical activity of the rabbit brain during consistent "animal hypnosis" series]

The dynamics of modification of individual rhythms of electrical activity in both hemispheres was studied under condition of chronic experiments in rabbits during "animal hypnosis" sessions. It was shown that, after the first "animal hypnosis" session, significant changes in the spectral power of electrical activity appeared only in the right premotor cortical area. They consisted in an increase in the spectral power of the delta1 and delta2 rhythms and a decrease in the spectral power of the other rhythms. During the next "animal hypnosis" sessions, changes in the electrical activity became stronger, especially in the right hemisphere. Significant changes in the spectral power of the delta and theta rhythms appeared not at the beginning of the "animal hypnosis" session but 4-6 min later. During the third "animal hypnosis" session, the power of the alpha and beta rhythms in the premotor and sensorimotor cortical areas of both hemispheres varied in an undulatory way.

Genetic differences in coping strategies in response to prolonged and repeated restraint in Japanese quail divergently selected for long or short tonic immobility

Exposure to fearful situations elicits behavioral and Hypothalamic-Pituitary-Adrenal (HPA) axis responses characteristic of the coping response of individual animals to counteract environmental challenges. The aim of this study was to investigate behavioral and corticotropic responses concomitantly following prolonged or repeated restraint stress by placing two genotypes of Japanese quail divergently selected for long (LTI) or short (STI) duration of tonic immobility (TI) in a crush cage. In our study, STI quail exhibited higher corticosterone (CORT) levels than LTI quail in response to prolonged restraint. STI quail struggled sooner and much more than LTI quail, and struggling behavior in STI quail progressively decreased during the course of restraint whereas LTI quail displayed very little struggling behavior in the crush cage. LTI quail are thus more likely to adopt a passive behavior coping strategy upon exposure to threat whereas STI quail behave more as active copers. The corticosterone responses shown by LTI and STI quail under restraint stress suggest that adrenocortical correlates of coping behavior in these genotypes of quail may be different from the coping styles previously described in other species. Repeated restraint slightly decreased CORT responses to stress in all experimental groups, but more markedly in male STI quail, whereas adrenal sensitivity and maximum adrenal corticosterone response capacity did not change in any group. On the other hand, neither behavioral habituation nor sensitization processes occurred in the context of repeated restraint in female and male LTI quail and female STI quail, whereas the decreases observed in some behavioral responses were interpreted to be the result of a habituation process in male STI quail.

Behavioral effects of dietary cholesterol in rats tested in experimental models of mild stress and cognition tasks

Abnormalities in serum cholesterol levels of patients with mood disorders have been identified in epidemiological studies. However, evidence for an influence of dietary cholesterol on behavioral models is poor. Here, we investigated the behavioral changes of Wistar male rats fed a 2% cholesterol-enriched diet for 2 months in experimental models of depression and anxiety, such as the forced swim test (FST) paradigm and the novelty-induced grooming sampling test (NGT). The correlation between behavioral depression and impaired cognitive capacity was also examined testing rats in the Morris water maze (MWM) task one day after the FST. Different groups of rats fed various dietary regimens, were subjected to acute or repeated treatment (14 days) with clomipramine hydrochloride (50 or 25 mg/kg), diazepam (1 mg/kg) or with the peripheral benzodiazepine receptors (PBRs) antagonist, isoquinoline PK11195 (1 mg/kg) injected intraperitoneally (i.p.). Rats fed the cholesterol-enriched diet showed a significant decrease of grooming score in the NGT and of immobility time in the FST in comparison to animals fed a standard diet. Furthermore, the anxiolytic and antidepressant effects of diazepam and clomipramine were not affected by the different diets. Only after repeated treatment, PK11195 impaired the performance of animals fed a standard diet in the FST, and exhibited an anxiolytic-like profile in animals fed either the cholesterol-enriched or the standard diet. The improved performance in the FST was followed by a better learning performance in the acquisition phase of the MWM. These results suggest that effects of cholesterol-enriched diet on the behavioral reaction of rats in experimental models of mild stress may involve PBRs. They deserve attention in order to clarify the clinical correlation between plasma cholesterol levels and mood disorders in humans.

Implication of neuropeptide-Y Y2 receptors in the effects of immune stress on emotional, locomotor and social behavior of mice

Neuropeptide Y (NPY) is involved in the regulation of emotional behavior, and there is indirect evidence for a role of NPY in the cerebral responses to peripheral immune challenge. Since the NPY receptors involved in these reactions are not known, we investigated the effect of Escherichia coli lipopolysaccharide (LPS) on emotional, locomotor and social behavior, body temperature and circulating corticosterone in female Y2 (Y2-/-) and Y4 (Y4-/-) receptor knockout mice. LPS (0.1mg/kg injected IP 2.5h before testing) increased rectal temperature in control and Y4-/- mice to a larger degree than in Y2-/- animals. Both Y2-/- and Y4-/- mice exhibited reduced anxiety-related and depression-like behavior in the open field, elevated plus-maze and tail suspension test, respectively. While depression-like behavior was not changed by LPS, anxiety-related behavior was enhanced by LPS in Y2-/-, but not control and Y4-/- animals. Y2-/- mice were also particularly susceptible to the effect of LPS to attenuate locomotor behavior and social interaction with another mouse. The corticosterone response to LPS was blunted in Y2-/- mice which presented elevated levels of circulating corticosterone following vehicle treatment. These data show that Y2-/- mice are particularly sensitive to the effects of LPS-evoked immune stress to attenuate locomotion and social interaction and to increase anxiety-like behavior, while the LPS-induced rise of temperature and circulating corticosterone is suppressed by Y2 receptor knockout. Our observations attest to an important role of endogenous NPY acting via Y2 receptors in the cerebral response to peripheral immune challenge.

Peritraumatic tonic immobility predicts a poor response to pharmacological treatment in victims of urban violence with PTSD

INTRODUCTION

Tonic immobility is the last defense against predation in animals and is characterized by paralysis and analgesia. In humans, it has only been reported in women victims of sexual abuse.

OBJECTIVE

This study evaluated the prevalence of peritraumatic tonic immobility (PTI) in patients with PTSD and investigated its association with response to treatment.

METHOD

Victims of urban violence with PTSD diagnosed through the SCID-IV (n=23) underwent a naturalistic pharmacological treatment according to the recommended guidelines for PTSD. The Post-Traumatic Stress Disorder Checklist--Civilian Version (PCL-C) and the Clinical Global Impressions (CGI) Severity scores were applied at baseline and endpoint. PTI was assessed using the Tonic Immobility Scale.

RESULTS

PTI was reported by both genders in 43% of the sample. Patients with PTI responded significantly poorly to treatment than those without it, either considering the PCL-C or the CGI scores.

LIMITATIONS

This study probed PTI retrospectively and was based on a small sample recruited in a tertiary clinic.

CONCLUSIONS

We have expanded the scope of the two previous investigations on PTI by showing its occurrence also in men and during non-sexual violence. In addition, the finding of a significant relationship between PTI and poor response to treatment of PTSD indicates that PTI may carry a prognostic value in this disorder and suggests that PTI should be routinely assessed in traumatized patients.

Intensity and duration of corticosterone response to stressful situations in Japanese quail divergently selected for tonic immobility

Two genotypes of Japanese quail have been divergently selected since the 1980s for long (LTI) or short (STI) duration of tonic immobility [Mills, A.D., Faure, J.M., 1991. Divergent selection for duration of tonic immobility and social reinstatement behavior in Japanese quail (Coturnix coturnix japonica) chicks. J. Comp. Psychol. 105(1), 25-38.], an unlearnt catatonic state characteristic of a behavioral fear response ([Jones, R.B., 1986. The tonic immobility reaction of the domestic fowl: a review. World's Poult. Sci. J. 42(1), 82-97.]; [Mills, A.D., Faure, J.M., 1991. Divergent selection for duration of tonic immobility and social reinstatement behavior in Japanese quail (Coturnix coturnix japonica) chicks. J. Comp. Psychol. 105(1), 25-38.]). The results of several behavioral tests conducted in LTI and STI quail have led to the conclusion that LTI quail are more fearful than STI quail [Faure, J.M., Mills, A.D., 1998. Improving the adaptability of animals by selection. In: Grandin, T. (Eds.), Genetics and the behavior of domestic animals. Academic Press, San Diego, pp. 235-264.]). However, few studies to date have focused on the Hypothalamic-Pituitary-Adrenal (HPA) axis response to stressful situations in LTI and STI quail, although the HPA axis is involved in fear responses [Siegel, H.S., 1971. Adrenals, Stress and the Environment. World's Poult. Sci. J. 27, 327-349.]. The corticosterone (CORT) response to various putatively stressful situations was therefore assessed in LTI and STI genotypes of quail in order to investigate their HPA axis reactivity to stress. Repeated induction of TI or 1 min manual restraint induced significant and comparable increases in CORT levels in both genotypes as a TI response. On the other hand, higher CORT responses were found in STI than in LTI quail when the manual restraint period lasted for 2 min or after restraint in a crush cage. Maximum CORT responses and genotype differences were maintained throughout the latter test even when it lasted for 120 min. Investigation of the CORT response to a single TI episode showed that CORT levels at the end of TI were negatively correlated with TI duration. Other experimental contexts consisting of isolation in a familiar or novel environment or the presentation of a novel object induced slight but significant and comparable increases in CORT response in both genotypes, whereas change of cagemates did not. In conclusion, the present findings indicate that differences in HPA axis response are observed between LTI and STI genotypes when quail are submitted to intense stressors, resulting in a high and prolonged CORT response. By contrast, plasma corticosterone concentrations do not differ between STI and LTI quail in response to stressful situations of lower intensity, which evoke responses limited in amplitude and duration. Genetic selection for divergent duration of TI has thus affected the HPA axis response to stress, and LTI and STI quail constitute an interesting model to investigate genetic variability of HPA axis activity in birds. More specifically, these genotypes of quail could be used to investigate the occurrence of functional differences at different levels of the HPA axis in order to explain the present findings.

Effects of chronic and acute stressors and CRF on depression-like behavior in mice

The effects of chronic footshock (CFS) on behavioral responses of CD1 mice to acute footshock and restraint were studied in tests commonly used to assess antidepressant treatments. Adult male mice were subjected to 20 min of footshock daily for 14-16 days, and then tested in the tail suspension test (TST) and the forced swim test (FST). CFS treatment did not alter immobility in the TST when mice were tested before the footshock on that day. However, when the TST was performed after the footshock, immobility decreased in both control and CFS mice. In the FST, chronic footshock significantly increased the time spent floating when mice were tested before footshock on that day. However, when the FST was performed immediately after the footshock, floating decreased in the CFS mice, but not in previously unshocked mice. Restraint, shortly before the FST, decreased floating in both CFS and unshocked mice. Thus, CFS induced depression-like activity in the FST, but not in the TST, whereas acute footshock or restraint immediately before testing induced antidepressant-like effects in both the TST and the FST. In unshocked mice, intracerebroventricular corticotropin-releasing factor (CRF) consistently decreased immobility in the TST and the FST, with significant effects at the 100ng dose. The same dose of CRF depressed activity in the open field, so that these changes in immobility are unlikely to reflect a change in overall activity. CRF thus mimicked the effects of the acute stressors in the TST and the FST. Responses to icv CRF were attenuated by chronic footshock suggesting that CFS desensitizes the brain to CRF. CFS treatment did not alter basal concentrations of ACTH and corticosterone in blood plasma. Acute footshock increased the plasma concentrations of the hormones but in CFS mice these responses were attenuated, significantly for plasma ACTH. Acute footshock activated brain dopamine, norepinephrine and serotonin metabolism, and increased tryptophan concentrations in the brain. In CFS mice, these responses were attenuated, significantly for hypothalamic NE.

Preproenkephalin knockout mice show no depression-related phenotype

Clinical, preclinical, and pharmacological studies have suggested that decreased enkephalin tone is associated with depression-like symptoms and increase in enkephalin signaling could have a therapeutic value in the treatment of depression. In this study we demonstrate that, surprisingly, animals lacking enkephalin (preproenkephalin, Penk1(-/-)) showed no depression-related phenotype in the Porsolt forced swimming or tail suspension tests. Moreover, Penk1(-/-) mice had a lower frequency of depression-related behavior in stress-induced hypoactivity and ultrasonic vocalization models of depression, similar to animals treated with antidepressant drugs, although this effect was specific to the genetic background. In addition, there was no significant difference in the efficacy of antidepressant reference compounds in wild-type and knockout animals. Nialamide and amitriptyline were even slightly more effective in animals with genetic deletion of Penk1, whereas the minimal effective dose of imipramine and fluoxetine was the same in the two genotypes. The dual peptidase inhibitor RB-101 was also effective in Penk1(-/-) as well as in Penk1(-/-)/Pdyn(-/-) animals, although its efficacy was somewhat reduced compared with wild-type animals. This result was also surprising because the antidepressant effects of RB-101 were thought to be due to the elevation of enkephalin levels.

Activation of the mGlu7 receptor elicits antidepressant-like effects in mice

RATIONALE

Broad evidence indicates that modulation of the glutamatergic system could be an efficient way to achieve antidepressant activity. Metabotropic glutamate receptor (mGlu receptor) ligands seem to be promising agents to treat several central nervous system disorders, including psychiatric ones.

OBJECTIVES

The aim of our study was to investigate potential antidepressant-like activity of the first, selective, and bio-available mGlu7 receptor agonist, AMN082 (N,N'-dibenzyhydryl-ethane-1,2-diamine dihydrochloride), in wild-type (WT) and mGlu7 receptor knock-out (KO) mice.

MATERIALS AND METHODS

The forced swim test (FST) and the tail suspension test (TST) in mice were used to assess antidepressant-like activity of AMN082.

RESULTS

We found that AMN082, administered IP, induced a dose-dependent decrease in the immobility time of WT animals in the FST and TST, suggesting antidepressant-like potency of an mGlu7 receptor agonist. Moreover, AMN082 did not change the behaviour of mGlu7 receptor KO mice compared to WT littermates in the TST, while imipramine, used as a reference control, significantly reduced their immobility, indicating an mGlu7 receptor-dependent mechanism of the antidepressant-like activity of AMN082. However, at high doses, AMN082 significantly decreased spontaneous locomotor activity of both mGlu7 receptor KO mice and WT control animals, suggesting off-target activity of AMN082 resulting in hypo-locomotion.

CONCLUSIONS

These results strongly suggest that activation of the mGlu7 receptor elicits antidepressant-like effects.