Anxiety

    

Anxiety

 Anxiety, whether it is for men or animals, has positive values, as it represents an alarm bell against potentially harmful situations and induces body reactions and behaviors suitable for dealing with anxiety-producing events and dynamics. Avoiding or escaping negative situations, i.e. those that generate anxiety, represents an adaptive behavior useful in terms of the survival of the species. However, in humans, but also in animals, anxiety often passes from its adaptive, i.e. useful, aspects to non-adaptive ones, as anxious reactions are generalized to a series of 'neutral' situations. Usually, it is the environment and external stimuli that cause anxiety, but in some cases, it can originate from internal stimuli - for example, acceleration or deceleration of the heart rate, an increase in lactic acid or carbon dioxide - which are not connected to a real risk situation, but trigger anxious reactions. It is for these reasons that researchers study anxiety at the animal level: comparative studies can in fact not only shed light on the internal and external signals that induce anxiety reactions and on the psychobiological mechanisms involved in anxious behaviors, but also on pharmacological treatments which can reduce anxiety reactions and therefore break a vicious circle in which the state of anxiety is extended to non-anxious situations or to all the experiences of an individual. carbon dioxide - which is not connected to a real risk situation, but triggers anxious reactions. It is for these reasons that researchers study anxiety at the animal level: comparative studies can in fact not only shed light on the internal and external signals that induce anxiety reactions and on the psychobiological mechanisms involved in anxious behaviors, but also on pharmacological treatments which can reduce anxiety reactions and therefore break a vicious circle in which the state of anxiety is extended to non-anxious situations or to all the experiences of an individual. carbon dioxide - which are not connected to a real risk situation, but triggers anxious reactions. It is for these reasons that researchers study anxiety at the animal level: comparative studies can in fact not only shed light on the internal and external signals that induce anxiety reactions and on the psychobiological mechanisms involved in anxious behaviors, but also on pharmacological treatments which can reduce anxiety reactions and therefore break a vicious circle in which the state of anxiety is extended to non-anxious situations or to all the experiences of an individual.

Experimental models

The study of anxiety states in animals is linked to two types of experimental 'models', in which the anxiety-producing stimuli are respectively linked to 'internal' or 'external' factors.

a)     Models related to interoceptive factors (internal stimuli). In these experimental situations, drugs that generate anxiety are used. The prototype of these substances is a drug that induces convulsions in high doses: pentylenetetrazole or carbimazole. When administered in small doses to humans, it induces strong uncomfortable situations, the impression that something catastrophic could happen at any moment. Pentylenetetrazole also causes strong feelings of anxiety in laboratory animals, detectable both in terms of spontaneous behavior (restlessness, aggressiveness or tendency to withdraw) and in terms of already induced behavior modifications. For example.,

    Other substances such as strychnine, amphetamine, or beta-carbolines also induce feelings of anxiety in animals, which can be reduced or canceled through the administration or self-administration of anxiolytics. Most of these effects are linked to the action of anxiety-producing substances on the receptor of a particular nervous mediator, GABA (γ-aminobutyric acid, gamma-amino-butyric acid): not only the benzodiazepines act on it, as they exert their anxiolytic, but also endogenous molecules that induce anxiety, beta-carbolines, and substances such as pentylenetetrazole. Other sensations of intense anxiety can be caused by an increase in lactate (lactic acid produced, for example, by muscular work) and carbon dioxide: this can trigger man the so-called panic attack syndrome and intense anxiety behaviors in animals. The study of these dynamics between nervous mediators, humoral factors, and anxious behaviors in animals has made it possible to better understand the role of nervous mediators - GABA, norepinephrine, and serotonin - in anxious phenomena and to produce more selective anxiolytic substances.

b)     Models linked to exteroceptive stimuli (external factors). Ethologists have developed various animal models of anxious states, linked, respectively, to the environmental situation, to early experiences, to cognitive factors, to genetic predispositions. As far as the environmental situation is concerned, it can be anxiety-provoking depending on the characteristics and social dynamics of the species considered: generally rodents, which are used in the laboratory in psychobiological research, show anxiety when placed in a new environment, devoid of shelter, strongly illuminated.

    A classic test such as the open field (open field) is based precisely on these environmental characteristics, which induce the animal to freeze in the corners or along the walls of the perimeter surrounding the 'field', in the grip of a mild state of anxiety. Under the effect of tranquilizers, however, the animals move in the center of the field, explore it and do not have physiological reactions typical of anxiety. Situations in which an animal is placed in a group of other animals that know each other or those in which a mouse or rat is separated from its group are also anxiety-provoking. Another anxiety-provoking situation is that linked to the separation of the baby from the mother: both emit calls in the initial phase of the separation, which is defined as the 'protest phase' and which is not unlike the one that J. Bowlby (1953) describes in relation to the dynamics that occur in the human species during the traumatic separations between the baby and the mother. This separation was studied in primates by HF Harlow and S. Suomi, who demonstrated that it induces anxious states, and enhances the search for maternal substitutes (inanimate mannequins that simulate the shapes of an adult animal, leading to stereotypies and maladaptive behaviors. Early traumatizing experiences can also produce an increase in anxious behavior in adults in rodents. At the animal level, there are models of anxiety linked to the interpretation of frustrating experiences, i.e. to cognitive factors: one of the most studied techniques is that defined as ' executive monkey', involved in 'managerial' decisions. The experimental model is based on the use of two monkeys, both subjected to a stressful experience such as receiving 'negative' stimuli - a sudden breath of air on the face or a mild electric shock - which are not painful but annoying. Of the two monkeys, the 'manager' can postpone the stressful event over time, while the other can do nothing to ward off the negative stimulus: it is precisely the first that gradually manifests an increasing state of anxiety, which is linked to its activity' decision-making' and which, over time, is also generalized to other situations.

    Finally, it remains to be observed that the reactivity to environmental stimuli, to stressful situations and in general to novelties, strictly depends on individual factors, subject to genetic characteristics. This has led to the selection of strains of calm or anxious dogs, and above all of strains of rodents that show high or low anxiety responses in the presence of new environments or intruders, such as the Maudsley strains, selected by British comparative psychology scholars . The selection of anxious or non-anxious strains has allowed to deepen the role of both the limbic system involved in emotional reactions, and of the GABA and norepinephrine receptors, more or less evident depending on the strains. Populations of monkeys more or less resistant to environmental traumas have also been selected in primates, endowed with anxious or relaxed behaviors. Using these strains an experimental model of anxiety defined learned helplessness has been developed: in these cases the animal is not able to escape, oppose or control a situation anxiety, so over time can develop both a state of depression and a state of anxiety, or both. This model presents notable analogies with the various cases in which anxious responses or other forms of neurosis develop in humans, determined by the impossibility of exercising control over events through autonomous decisions.

PSYCHOBIOLOGICAL BASIS OF ANXIETY

    All organisms, including individuals of our species, tend towards survival, that is, to remain alive and to transmit life to the next generation. The way we act to achieve this goal is rather elementary: we look for those situations that contribute to survival and reproduction. On the other hand, we try to avoid anything that could threaten our well-being and that of our offspring. This does not mean that living beings always and deliberately evaluate each of their actions in terms of survival: as soon as an organism perceives a threat to its vital interests, it reacts immediately and instinctively. In humans, as well as in other mammals, the perception of danger is accompanied by physiological responses, such as

    According to scientists, these three types of reaction define anxiety: a response that therefore contains physiological (increased heart rate), cognitive (concentration) and behavioral (escape) aspects. The anxious reaction, in the variety of its manifestations, has a strong biological basis. Research on animals and humans suggests that evolution has preprogrammed organisms to react to danger with anxiety; it also shows how the delicate physiological systems involved in the mechanism of anxiety interact with each other. Undoubtedly, there is much more to anxiety than just genetic and physiological physical components. The learning experience determines under which circumstances the individual becomes anxious and cognitive processes are called into question in relation to the information about the danger. Not all members of a species are equally anxious and this certainly applies to humans: we differ in our tendency to fear a particular danger. Some of us get scared more easily than others, and if so, many studies suggest it's a genetic mutation.

    Twin research has been the most widely used tool to investigate the extent to which genetic factors may explain variations in anxiety. Identical, monozygotic (MZ) twins share genes and sociocultural backgrounds. Nonidentical, dizygotic (DZ) twins have only partially overlapping genetic makeup while sharing the environment to the same extent as monozygotic twins. If the similarity in terms of anxiety, between twin and cotwin, is greater in monozygotic than in dizygotic, this reasonably implies the existence of genetic factors involved in this process. A number of studies, based on a variety of anxiety indices, actually demonstrate that monozygotic twins are more alike than dizygotic twins, even in the case of anxiety disorders.