The fear hypothesis and tonic immobility (TI) modulation: Early studies in chickens.

The hypothesis that fear is involved in the mechanisms of tonic immobility (TI) has been supported by early studies conducted in newborn and adult chickens. The susceptibility to TI changes during development in parallel to other fear responses. TI duration increases following exposure before induction to threatening stimuli such as electric shock, loud sound, stuffed sparrow hawk, as well as in unfamiliar conditions applied before and/or during testing.

Neural circuits of fear and defensive behavior.

Innate fear-related behavioral responses have evolved as strategies for survival. The neural circuits responsible for defensive responses, studied mainly in rodents, have been substantially preserved across evolution. Amygdala collects sensory information (visual, auditory and olfactory) in the cortical division and conveys it to the striatal output division.

Introduction to defensive behavior in vertebrates.

In this introductory chapter we describe the ethological basis of defensive behavior, including tonic immobility (TI). The defensive repertoire activated in response to threatening stimuli, both in natural and experimental conditions, consists of a system of interrelated behaviors influenced by two main dimensions, as distance from the threat and escapable/inescapable context. When the active strategy of escape is not feasible, passive immobility forms are adopted, the latter representing substitutes of actual escape.

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.

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.

Pain control in tonic immobility (TI) and other immobility models.

This chapter deals with the mechanisms modulating pain during TI and other immobility responses in different animal species. In mammals the presence of high voltage slow waves in the electroencephalogram during TI suggests the activation of the thalamic gate, a mechanism blocking all sensory information, including pain. In rabbits TI transiently suppresses all the behavioral responses to persistent nociceptive stimulation by the activation of an opioid mechanism outlasting TI offset by 1h.

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.

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.

Neuromediators and defensive responses including tonic immobility (TI): Brain areas and circuits involved.

Serotonin, acetylcholine and GABA are the neuromediators most involved in tonic immobility (TI). TI duration, in fact, decreases in rabbits following systemic serotonin administration and in guinea pigs following serotonin microinjection administration into the amygdala owing to the activation of fear-related GABAergic inhibitory mechanisms. On the other hand, repeated TI inductions in rabbits and guinea pigs reduce brain serotonin turnover in several brain areas.

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.

The neuroethological approach to defense in rabbit.

In this chapter we review the neuroethological approach correlating behavior and dorsal hippocampal activity recorded in rabbits in laboratory conditions or in a semi-natural enclosure and exposed to intra and interspecific confrontations. Behaviors of the same modality, i.e.

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.

Defensive responses in invertebrates: Evolutionary and neural aspects.

Lower invertebrates exhibit both morphological and behavioral defensive responses to aversive stimuli, characterized by withdrawal. Typical immobility responses are "sinking" in Rotifers and "crumpling" in Cnidaria. They also display individual adaptation and phenotypic plasticity but not tonic immobility (TI).

Cardiovascular correlates of human emotional vasovagal syncope differ from those of animal freezing and tonic immobility.

It has been suggested that vertebrate freezing and tonic immobility (TI) represent the antecedents of human emotional vasovagal syncope. When a prey detects an approaching predator, it suddenly interrupts its ongoing activity and behaves according to the predator's distance. A prey enters TI when the fight or flight reaction is not feasible and the animal is captured.

Developmental exposure to low levels of ethinylestradiol affects social play in juvenile male rats.

Juvenile social play contributes to the development of adult social and emotional skills in humans and non-human animals and is therefore a useful endpoint to study the effects of endocrine disrupters on behavior in animal models. Ethinylestradiol (EE), a widely produced, powerful synthetic estrogen is widespread in the environment mainly because it is a component of the contraceptive pill. To understand whether clinical or environmental exposure to EE during critical perinatal periods can affect male social play, we exposed 72 male Sprague-Dawley rats to EE or vehicle either during gestation (from gestation day (GD) 5 through 20) or during lactation (from postnatal day (PND) 1 through 21).

Offline consolidation of spatial memory: Do the cerebellar output circuits play a role? A study utilizing a Morris water maze protocol in male Wistar rats.

To address whether the cerebellum takes part to spatial memory consolidation related to navigation, male Wistar rats were trained daily (4 days), in a Morris water maze to found a submerged escape platform by use of distal cues (place training test). Retention of the allocentric map was evaluated in the probe test (without platform), before the place test. Bilateral shutdown of deep cerebellar nuclei was carried by infusion of the GABA-A agonist muscimol (0.

Developmental Exposure to Low Levels of Ethinylestradiol Affects Play Behavior in Juvenile Female Rats.

Juvenile social play contributes to the development of adult social and emotional skills in humans and non-human animals, and is therefore a useful endpoint to study the effects of endocrine disrupters on behavior in animal models. Ethinylestradiol (EE) is a widely produced, powerful synthetic estrogen that is widespread in the environment mainly because is a component of the contraceptive pill. In addition, fetuses may be exposed to EE2 when pregnancy is undetected during contraceptive treatment.

Developmental Exposure to Very Low Levels of Ethynilestradiol Affects Anxiety in a Novelty Place Preference Test of Juvenile Rats.

Ethinylestradiol (EE), a synthetic mimic of 17β-estradiol, is widespread in the environment because of its use as a contraceptive. In mammals, recent research highlighted behavioral, physiological, and morphological effects of exposition to EE (this xenoestrogen). We studied if developmental exposure to environmental-like, low doses of EE affects measures of anxiety in Sprague-Dawley rats.

Enriched environment and the recovery from inflammatory pain: Social versus physical aspects and their interaction.

In this study, we aimed at comparing the effect of the social versus the physical enrichment of the environment on inflammatory pain. Hence, a rat model of carrageenan-induced knee inflammation was used. Four housing conditions were investigated: a physically enriched environment (PE), a socially enriched environment (SE), an enriched environment (EE) (i.

Why public health agencies cannot depend on good laboratory practices as a criterion for selecting data: the case of bisphenol A.

Background: In their safety evaluations of bisphenol A (BPA), the U.S. Food and Drug Administration (FDA) and a counterpart in Europe, the European Food Safety Authority (EFSA), have given special prominence to two industry-funded studies that adhered to standards defined by Good Laboratory Practices (GLP).

Environmental-like exposure to low levels of estrogen affects sexual behavior and physiology of female rats.

Xenoestrogens are endocrine-disrupting chemicals that mimic the action of endogenous estrogen hormones. Effects of xenoestrogen on aquatic wildlife are well documented, whereas the experimental evidence for impairment of reproductive behavior and physiology in mammals after exposure to xenoestrogens has been debated. The strongest arguments against such studies have been that the route, time course, and intensity of exposure did not simulate environmental exposure and that the chemicals tested have additional nonestrogenic toxic effects, hindering generalization of actual xenoestrogenic effects.

In vivo effects of bisphenol A in laboratory rodent studies.

Concern is mounting regarding the human health and environmental effects of bisphenol A (BPA), a high-production-volume chemical used in synthesis of plastics. We have reviewed the growing literature on effects of low doses of BPA, below 50 mg/(kg day), in laboratory exposures with mammalian model organisms. Many, but not all, effects of BPA are similar to effects seen in response to the model estrogens diethylstilbestrol and ethinylestradiol.

Altered reproductive success in rat pairs after environmental-like exposure to xenoestrogen.

Endocrine-disrupting compounds (EDCs) have the capacity of altering the normal function of the endocrine system. EDCs have shown dramatic effects on the reproductive biology of aquatic wildlife and may affect human reproduction as well. Studies on EDCs in mammalian species have often investigated the effects of short-term, high doses on male and female reproductive physiology.