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).

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.

The relationship between tonic immobility and the development, severity, and course of posttraumatic stress disorder: Systematic and meta-analytic literature review.

BACKGROUND: Tonic immobility (TI) is a reflexive, involuntary response that causes motor inhibition, vocal suppression, and analgesia. TI is elicited by extreme fear and perception of entrapment in a life-threatening situation. Research suggests that TI is a frequent peritraumatic response and may be related to subsequent posttraumatic stress disorder (PTSD). However, findings are mixed and, as of yet, no systematic or meta-analytic review examining associations between TI and PTSD has been published. OBJECTIVE: We systematically and meta-analytically reviewed the literature and investigated whether TI is associated with the development, severity, and course of PTSD. Additionally, we evaluated whether different types of traumatic events are differentially associated with TI, and whether TI severity differs according to sex. METHODS: A systematic literature search was conducted using Embase, PubMed, PsycINFO, and Scopus. Meta-analyses were performed on the included articles. RESULTS: We identified 27 eligible articles. We found a significant association between TI and PTSD symptom severity (r = 0.39, 95% CI: 0.34-0.44; p < .0001). TI was more severe among females (Cohen's d=0.37, 95% CI: 0.25-0.48; p < .0001) and was more often elicited in situations involving interpersonal violence. We found limited longitudinal data to perform a meta-analysis of the association between TI and the development and/or course of PTSD. However, the literature available seems to support the role of TI in both the development and course of PTSD. CONCLUSIONS: Peritraumatic TI is associated with PTSD symptom severity, occurs more often during interpersonal violence, and is more severe among females. More longitudinal research is needed to investigate the role of TI in psychopathology development and course.

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.

Tonic immobility (freezing) during sexual and physical assaults produces stronger memory effects than other characteristics of the assaults.

Tonic immobility (TI) is a phylogenetically conserved, passive, obligatory defense mechanism commonly engaged during sexual and physical assaults. During TI, people become immobile while remaining conscious and later reexperience intrusive memories of both their assault and of its accompanying immobility. Here we show that this well-studied biological process has powerful effects on memory and other processes. Participants had experienced either a serious sexual (n = 234) or physical (n = 137) assault. For both the assault and its accompanying immobility, the standard measure of the peritraumatic severity of TI correlated between .40 and .65 with post-assault effects on memory, including memory of the assault and memory of the immobility, the two memory-based self-concept measures of self-blame and event centrality, and post-assault anxiety and depression. The correlations with TI were much higher than other peritraumatic characteristics commonly used to predict and describe posttraumatic effects in assaults and other traumas. The results suggest that TI should be considered for a broader, more biologically based and ecologically valid understanding of the effects of trauma on memory and memory-based reactions.

Dominance and inheritance patterns of mobility and death feigning in beetle strains selected for moving activity.

Reciprocal crossing of different strains is a suitable method to investigate the dominance and inheritance of a focal trait. Herein, we performed reciprocal crossing among strains of Tribolium castaneum exhibiting a genetically high (H strain) and low (L strain) moving activity and investigated the related heritable factors in the F1 and F2 generations. We also evaluated death-feigning behavior, which negatively responded to artificial selection for moving activity in T. castaneum. The results obtained for the F1 generation suggest that low moving activity and short duration of death feigning were dominant. In the F2 generation, movement and death feigning exhibited continuous segregation. The distribution of each trait value in the F2 generation differed from that in the parental generation, and no individuals transgressing the distribution of trait values in the parental generation emerged in the F2 generation. These results suggest that the genetic correlation between movement and death-feigning behavior is controlled in a polygenic manner. Moreover, the examination of the proportions of both behaviors (high vs. low moving activity and long vs. short death-feigning duration) in the F1 generation revealed that the two behaviors may be controlled by the maternal genotype, suggesting that the gene(s) that control movement and death feigning are located on the sex chromosome in T. castaneum.

Muito além do trauma: uma investigação sobre o papel das reações peritraumáticas sobre o transtorno de estresse pós-traumático / Beyond the trauma: an investigation of the role of peritraumatic reactions on posttraumatic stress disorder

O Transtorno de Estresse Pós-Traumático (TEPT) é uma condição debilitante que impacta significativamente a qualidade de vida dos seus portadores. Dentre vários fatores de risco para o TEPT, as reações peritraumáticas (RP), como a imobilidade tônica peritraumática (ITP), dissociação (DP) e reações físicas de pânico (RFP), estão entre as mais investigadas. No entanto, a maioria dos estudos avaliou essas RP separadamente, e o elo entre elas e o TEPT ainda não foi bem compreendido. Portanto, essa tese teve como objetivos: (i) estimar simultaneamente o efeito das três RP sobre o TEPT utilizando um instrumento validado; e (ii) avaliar se há efeito indireto da ITP sobre o TEPT mediado pelo sentimento de culpa/vergonha. Utilizamos modelagem de equações estruturais para analisar dados de 3211 participantes do Rio de Janeiro e de São Paulo. Tratamos as RP como variáveis latentes, selecionando desconfundidores específicos para cada reação. Nossas exposições foram as RP, sendo TEPT o desfecho. Calculamos odds ratios e intervalos de confiança de 95%. Utilizamos o Bayesian Information Criterion para comparar o ajuste de modelos não aninhados. Quando analisadas separadamente, todas as RP alcançaram significância estatística. No entanto, apenas DP (ORDP=1,8; IC95%:1,3-2,4) e RFP (ORRFP=2,5; IC95%:1,8-3,4) permaneceram estatisticamente significativas quando incluímos as três reações em um modelo com seus respectivos desconfundidores e correlações entre elas. Os resultados sugeriram um possível efeito da ITP sobre o TEPT (ORITP=1,4; IC95%:1,0-1,9). As interações entre as RP não foram estatisticamente significativas. Ao investigarmos o sentimento de culpa/vergonha como mediador entre ITP e TEPT, o efeito indireto alcançou apenas significância estatística limítrofe (ORITP(TNIE)=1,1; IC95%:1,0-1,2). Os efeitos direto (ORITP(PNDE)=1,3; IC95%: 0,8-1,8) e total (ORITP(TE)=1,4; IC95%:0,9-1,9) para ITP perderam significância quando todas as RP, seus desconfundidores e correlações entre elas fizeram parte do mesmo modelo. As demais RP, no entanto, permaneceram estatisticamente significativas (ORDP=1,7; IC95%:1,3-2,3 e ORRFP=2,5; IC95%:1,8-3,4). Nossos resultados mostraram que a DP e as RFP aumentaram o risco de TEPT mesmo quando consideradas em conjunto. A ITP pode ter efeito sobre o risco de TEPT, mas esse achado deve ser interpretado com cautela devido a significância limítrofe dessa RP em nosso modelo final. Também não identificamos uma mediação significativa entre ITP e TEPT pelos sentimentos de culpa/vergonha. Contudo, a significância limítrofe encontrada para o efeito indireto demanda investigações adicionais. Nossos achados reforçam a ideia de que as reações peritraumáticas devem ser analisadas e compreendidas como ocorrências simultâneas. Também seria oportuno que estudos envolvendo culpa/vergonha, ITP e TEPT focalizassem traumas caracterizados por aprisionamento e impossibilidade de escapar, dado que estas experiências são apontadas como mais susceptíveis para desencadear a ITP. (AU)

Posttraumatic stress disorder (PTSD) is a debilitating condition that greatly impacts quality of life. Among several PTSD risk factors, peritraumatic reactions (PR) such as peritraumatic tonic immobility (PTI), dissociation (PD) and physical panic reactions (PPR) are some of the most investigated. However, several studies have assessed these PR separately, and the pathway connecting them to PTSD is not well understood. Therefore, this thesis aimed to: (i) simultaneously estimate the effect of the three PR on PTSD using a validated instrument; and (ii) assess if there is an indirect effect of PTI on PTSD mediated by feelings of guilt/shame. We used structural equation modelling to analyse data from 3211 participants from Rio de Janeiro and São Paulo. We treated the PR as latent variables and selected specific confounders for each reaction. Our exposures were the PR, and PTSD was the outcome. We calculated odds ratios and 95% confidence intervals for each analysis. We also employed the Bayesian Information Criterion to compare the goodness of fit between non-nested models. Separately, all PR achieved statistically significant results. However, only PD (ORPD=1.8; 95%CI:1.3-2.4) and PPR (ORPPR=2.5; 95%CI:1.8-3.4) remained statistically significant when all three were included in a model with their respective confounders and correlations among all PR. Our findings suggested a possible effect of PTI on PTSD (ORPTI=1.4; 95%CI:1.0-1.9). Interactions between the PR were not statistically significant. When we investigated feelings of guilt/shame as the mediator between PTI and PTSD, the indirect effect achieved a borderline statistical significance (ORPTI(TNIE)=1.1; 95%CI:1.0-1.2). Direct (ORPTI(PNDE)=1.3; 95%CI:0.8-1.8) and total (ORPTI(TE)=1.4; 95%CI:0.9-1.9) effects lost their significance when all PR, their confounders and correlations were included in the same model. The other PR remained statistically significant (ORPD=1.7; 95%CI:1.3-2.3 and ORPPR=2.5; 95%CI:1.8-3.4). Our findings showed PD and PPR to increase the risk of PTSD even when considered in tandem. PTI could have an effect on PTSD, but this must be considered cautiously, as this PR only reached borderline significance in our final model. Feelings of guilt/shame did not significantly mediate PTI's effect on PTSD. However, a borderline statistical significance in the indirect effects warrants further investigation. Our findings reinforce the hypothesis that peritraumatic reactions should be analysed and understood as simultaneous occurrences, not as separate entities. It would also be appropriate for studies concerning guilt/shame, PTI and PTSD to focus on traumas characterized by imprisonment and feelings of inescapability, given that these experiences are allegedly more likely to trigger PTI. (AU)

Stuck in a Moment: Tonic Immobility Predicts Poor Quality of Life in Treated PTSD Patients.

BACKGROUND: Posttraumatic stress disorder (PTSD) is a prevalent and disabling multisystem disorder, with significant physical and psychiatric morbidity and poor quality of life (QOL). Although peritraumatic reactions - tonic immobility and dissociation - are established predictors of PTSD severity and development, there is a dearth of investigation assessing the impact of peritraumatic reactions on QOL of PTSD patients. Quality of life has become increasingly important in health care and research as a reliable outcome measure. It comprises psychological, physical, social and environmental domains, providing important information about the impact of diseases on patient's life. This study aims to investigate the impact of peritraumatic tonic immobility and peritraumatic dissociation on QOL of PTSD civilian outpatients. SUBJECTS AND METHODS: It is a cross-sectional study of 50 victims of urban violence with current PTSD, recruited in a specialized outpatient clinic. Instruments used were: Structured Clinical Interview IV, Peritraumatic Dissociative Experiences Questionnaire, Tonic Immobility Scale and WHOQOL-BREF (psychological, physical, social and environmental domains). Linear regression models were fitted to evaluate the impact of peritraumatic reactions - tonic immobility and dissociation - on WHOQOL-BREF scores. We controlled for sex as potential confounding. RESULTS: The severity of peritraumatic tonic immobility negatively impacted on psychological and environment domains of quality of life. For each additional point on the Tonic Immobility Scale, there was a decreased of 0.8 points on the scores of these domains of WHOQOL-BREF. Neither the peritraumatic reactions showed effects on physical nor social domains. Possible limitations of this study include cross-sectional design, relatively small sample size of tertiary center outpatients and recall bias. CONCLUSIONS: Peritraumatic tonic immobility is related to poor quality of life, adding new insights about the relationship between this immobility reaction and PTSD.

Tonic immobility is associated with posttraumatic stress symptoms in healthcare professionals exposed to COVID-19-related trauma.

The Coronavirus Disease 2019 (COVID-19) pandemic has exposed healthcare workers (HCW) to traumatic situations that might lead to the development of posttraumatic stress disorder (PTSD). An important vulnerability factor for PTSD is the peritraumatic tonic immobility (TI) reaction, an involuntary and reflexive defensive response evoked by an intense and inescapable threat. TI is largely understudied in humans and has not been investigated during trauma related to COVID-19. For HCW, the pandemic context might be experienced as an intense and potentially inescapable threat, i.e., an overwhelming situation. Here, we investigated if TI response occurred during traumatic events related to the pandemic and its association with posttraumatic stress symptoms (PTSS). An online survey of 1001 HCW investigated COVID-19-related traumatic experiences, TI and PTSS. TI was reported for all types of traumatic events, and multivariate regression models revealed that TI was significantly associated with PTSS severity. HCW who reported high TI scores exhibited an increase of 9.08 times the probability of having a probable diagnosis of PTSD. Thus, TI was evoked by pandemic-related traumatic situations and associated with PTSS severity and higher odds of a PTSD diagnosis. Tonic immobility occurrence should be screened, and psychoeducation about its reflexive biological nature should be introduced.

Responses to artificial selection for locomotor activity: A focus on death feigning in red flour beetle.

Whole-organism performance, including locomotor activity, is an important fitness trait in many animals. Locomotor activity is often classified into sprint speed and locomotor endurance and differences in sprint speed and locomotor endurance affect on other traits such as life-history traits. Previous studies found that locomotor endurance, sprint speed and brain dopamine (DA) levels are correlated with artificial selection for death feigning (an anti-predator behaviour that we refer to as 'death-feigning syndrome') in some insect species. Thus, if the syndrome has a genetic basis, death feigning, sprint speed and brain DA levels may be affected by artificial selection for locomotor endurance. We artificially selected for locomotor endurance over 10 generations in the red flour beetle Tribolium castaneum, and established higher (H) and lower activity (L) strains, then compared their death-feigning behaviour, sprint speed and brain DA levels. H-strain beetles exhibited significantly shorter duration of death-feigning, and significantly higher sprint speeds, suggesting variation in death-feigning syndrome. Surprisingly, although brain DA expression affects various animal behaviours, we found no significant differences in the brain DA expressions of H- and L-strain beetles. Thus, our results imply genetic correlations between locomotor endurance, sprint speed and death feigning, but not with brain DA expression, suggesting that differences in the biogenic amine results of our and previous studies may reflect differences in behavioural expression mechanisms.

Environmental, ecological and methodological factors of Tonic Immobility (TI) modulation.

Modulation of Tonic Immobility (TI) concerns environmental and individual factors. TI is modulated by processes of habituation and sensitization. In poikilotherm frog and lizard, TI duration is much shorter at usual environmental temperatures and is potentiated at higher or lower temperatures, as the last resource for survival. During ontogeny, age may differentially affect TI susceptibility to the induction procedures, as in the case of newborn ectothermic and older endothermic rabbits. TI duration displays a daily rhythm, with longer TI in the night. Its resistance to habituation indicates that in the dark TI is the most prominent defense against nocturnal predators. In all studied species, there is synchronization of the prey's defensive responses with the feeding activity of predators. Ecological factors and exposure to different anthropogenic environmental pressures may alter morphology, behavior and TI in wild populations. TI duration has been associated with a genomic region comprising the dystrophin gene on quail chromosome 1.

Neurophysiological mechanisms involved in tonic immobility (TI).

This chapter summarizes the main neurophysiological characteristics of tonic immobility (TI), in many susceptible species of mammals and birds. During TI, cortical EEG shows high voltage slow waves whose amount is affected by events preceding TI induction and is positively correlated with TI duration. The pattern of hippocampal activity helps to predict TI onset and TI termination. Both polysynaptic flexor and monosynaptic heteronymous reflexes are depressed independently from the EEG activity. Brain metabolism, signaled by glycogen mobilization and glucose utilization, indicates a reduced neuronal activity during TI. Learned avoidance responses to shock can be extinguished during TI and recover after TI. Moreover, during TI animals may learn how to avoid the shock by a motor response that may be followed by TI interruption. Decortication, decerebellation and telencephalic sections do not affect TI characteristics, whereas ponto-mesencephalic sections abolish both righting reflexes and TI.

Neuroendocrine correlates of stress and tonic immobility.

Threatening stimuli challenging animal homeostasis are the primary events triggering defensive responses, including TI. The stress-response system (allostasis) is signaled by increased corticosteroid basal levels. In bird animal lines genetically selected for stress-induced corticosterone, there is a covariation between stress physiology and coping styles. Rabbit studies, in which the effects of TI are dissociated from those of induction per se, support the view that TI takes part in the homeostatic stress-response system. An increase of corticosterone is recorded just after the end of the induction procedure but not in the corresponding groups in which induction is followed by TI, suggesting a recovery process during TI. Similarly to corticosterone but in opposite direction, testosterone plasma levels decrease following induction and recover during TI. Recovery mechanisms are also suggested in two bird genotypes selected for long and short TI duration. The positive relation between corticosterone levels and TI duration has been confirmed after exogenous corticosterone administration.

Autonomic correlates of defense responses, including tonic immobility (TI).

Animal models of autonomic correlates of defense behavior range from fish to mammals. There is however no study reporting heart and respiratory rate, blood pressure and body temperature simultaneously recorded in the same animal in association to different forms of immobility in response to threat: freezing, restraint-sustained immobility and tonic immobility (TI). In a prey/ predator context freezing behavior is associated with bradycardia and no change in blood pressure but in other conditions (e.g., extreme stressful stimuli) may be associated with tachycardia and hypertension. Restraint-sustained immobility does not affect blood pressure but may reduce heart rate according to the type of stimulus and mechanical pressure. Blood pressure and heart rate oscillate during TI induction and adjust at basal levels during TI, sometimes gradually decreasing below basal levels. In conclusion, in all these passive defense responses, the immobility is not due to a blood pressure collapse.

Tonic immobility as a survival, adaptive response and as a recovery mechanism.

In this conclusive chapter, we review findings giving support to the hypothesis that TI represents an adaptive, survival response to threatening situations. In models of prey-predator interactions, in vertebrates and invertebrates, there are evidence that immobility per se contributes to survival, as the predator loses interest for a prey in which TI is experimentally induced. TI duration is also reciprocally modulated by the evaluation of the risk factors in the environment, and by the opportunity to reach a safe refuge. This supports the adaptive value of TI and suggests that, during TI, the animal may be transiently aware of the environmental situation. As for the adaptive value of TI, genetic correlations with other behavioral systems contributing to fitness (e.g., mating) are taken into account. Moreover, neurophysiological and endocrine findings in mammals support our hypothesis that TI activates the mechanisms responsible for recovery from disruptive experiences and body lesions.

Synthesis of defense response characteristics.

In previous chapters, the available theories and experimental findings related to animals' defense responses have been reported and discussed in detail. This chapter reports their comprehensive synthesis, considering the main immobility-related responses in defense. Within the same modality (i.e., immobility) different kinds of immobility may in fact correspond to different functions and motivations, as proved by their neurobiological correlates profile.

Neurochemical anatomy of dorsal and tonic immobility responses.

The dorsal immobility response (DIR) and the tonic immobility response (TIR) are cutaneo-motor reflexes typically triggered when a prey is seized. The neurochemical basis of the DIR appears to pass through the basal ganglia via dopaminergic fibers, while the neurochemical basis of the TIR appears to include a circuit comprising the amygdala, the periaqueductal gray (PAG), the dorsal raphe, and the nucleus magnus raphe (NMR) via glutamatergic, serotonergic, cholinergic, GABAergic, and opioid fibers. For the DIR, the basal ganglia also seem to be involved in regard to estradiol, while for the TIR, the HPA axis appears involved at the level of the amygdala and the oral pontine reticular nucleus.

The Tonic Immobility Scale in adolescent and young adult rape victims: Support for three-factor model.

OBJECTIVE: A substantial number of sexual assault victims report experiencing some form of peritraumatic tonic immobility (TI). A self-report questionnaire that is widely used to assess TI retrospectively is the Tonic Immobility Scale (TIS). This study explored the factor structure of the TIS in a clinical sample of adolescent and young adults. METHOD: The sample comprised 131 female rape victims, aged 13-25, who were referred for specialized trauma-focused treatment. An exploratory factor analysis (EFA) was performed. RESULTS: The EFA showed support for a three-factor model, with factors TI, Fear, and Detachment. Item correlations ranged from .32 to .57 for TI, from .14 to .35 for Fear, and .29 for the two Detachment items. CONCLUSIONS: We found support for a three-factor solution distinguishing TI, fear, and detachment, suggesting the need to further develop the TIS with different subscales in varying age groups and clinical samples. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

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.

Differential effects of the novel neurosteroid hypnotic (3ß,5ß,17ß)-3-hydroxyandrostane-17-carbonitrile on electroencephalogram activity in male and female rats.

BACKGROUND: We recently showed that a neurosteroid analogue, (3ß,5ß,17ß)-3-hydroxyandrostane-17-carbonitrile (3ß-OH), induced hypnosis in rats. The aim of the present study was to evaluate the hypnotic and anaesthetic potential of 3ß-OH further using electroencephalography. METHODS: We used behavioural assessment and cortical electroencephalogram (EEG) spectral power analysis to examine hypnotic and anaesthetic effects of 3ß-OH (30 and 60 mg kg-1) administered intraperitoneally or intravenously to young adult male and female rats. RESULTS: We found dose-dependent sex differences in 3ß-OH-induced hypnosis and EEG changes. Both male and female rats responded similarly to i.p. 3ß-OH 30 mg kg-1. However, at the higher dose (60 mg kg-1, i.p.), female rats had two-fold longer duration of spontaneous immobility than male rats (203.4 [61.6] min vs 101.3 [32.1] min), and their EEG was suppressed in the low-frequency range (2-6 Hz), in contrast to male rats. Although a sex-dependent hypnotic effect was not confirmed after 30 mg kg-1 i.v., female rats appeared more sensitive to 3ß-OH with relatively small changes within delta (1-4 Hz) and alpha (8-13 Hz) bands. Finally, 3ß-OH had a rapid onset of action and potent hypnotic/anaesthetic effect after 60 mg kg-1 i.v. in rats of both sexes; however, all female rats and only half of the male rats reached burst suppression, an EEG pattern usually associated with profound inhibition of thalamocortical networks. CONCLUSIONS: Based on its behavioural effects and EEG signature, 3ß-OH is a potent hypnotic in rats, with female rats being more sensitive than male rats.