Estrogens exert profound effects on the expression of anxiety in humans and rodents; however, the directionality of these effects varies considerably within both clinical and preclinical literature. It is believed that discrepancies regarding the nature of estrogens’ effects on anxiety are attributable to the differential effects of specific estrogen receptor (ER) subtypes. In this chapter we will discuss the relative impact on anxiety and anxiety-like behavior of each of the three main ERs: ERα, which has a generally anxiogenic effect, ERβ, which has a generally anxiolytic effect, and the G-protein-coupled ER known as GPR30, which has been found to both increase and decrease anxiety-like behavior. In addition, we will describe the known mechanisms by which these receptor subtypes exert their influence on emotional responses, focusing on the hypothalamic–pituitary–adrenal axis and the oxytocinergic and serotonergic systems. The impact of estrogens on the expression of anxiety is likely the result of their combined effects on all of these neurobiological systems.

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Due to the dynamic development of molecular neurobiology and bioinformatic methods several novel brain neuropeptides have been identified and characterized in recent years. Contemporary techniques of selective molecular detection e.g. in situ Real-Time PCR, microdiffusion and some bioinformatics strategies that base on searching for single structural features common to diverse neuropeptides such as hidden Markov model (HMM) have been successfully introduced. A convincing majority of neuropeptides have unique properties as well as a broad spectrum of physiological activity in numerous neuronal pathways including the hypothalamus and limbic system. The newly discovered but uncharacterized regulatory factors nesfatin-1, phoenixin, spexin and kisspeptin have the potential to be unique modulators of stress responses and eating behaviour. Accumulating basic studies revelaed an intriguing role of these neuropeptides in the brain pathways involved in the pathogenesis of anxiety behaviour. Nesfatin-1, phoenixin, spexin and kisspeptin may also distinctly affect the energy homeostasis and modulate food intake not only at the level of hypothalamic centres. Moreover, in patients suffered from anxiety and anorexia nervosa a significant, sex-related changes in the plasma neuropeptide levels occurred. It should be therefore taken into account that the targeted pharmacomodulation of central peptidergic signaling may be potentially helpful in the future treatment of certain neuropsychiatric and metabolic disorders. This article reviews recent evidence dealing with the hypothetical role of these new factors in the anxiety-related circuits and pathophysiology of anorexia nervosa.