Neuropeptides and Behavioural and Physiological Stress Response: The Role of Vasopressin and Related Peptides

Abstract

Classical views on stress mechanisms maintain that the activation of the adrenal medulla and the cortex represent the major neuroendocrine aspects of stress. The functional significance of these hormones in both physiological and behavioural stress responses have been repeatedly emphasized (e.g. Mason, 1968; Selye, 1976; Bohus, 1984; Oliverio, 1987; etc.). Besides these stress hormones of the first generation a new class of neuroendocrine principles emerged that also serve stress functions (Bohus, 1984). These second generation consists of long known pituitary and their target hormones (e.g. prolactin, vasopressin, oxytocin, growth hormone, gonadotrophins, testosterone, thyroid-stimulating hormone, thyroxine; see Bohus, 1984; Oliverio, 1987) with a recently established stress function. In addition, newly discovered hormones such as the endorphins and enkephalins (e.g. Guillemin et al., 1977; Amir et al., 1980) and of hypothalamic neuroendocrine factors such as the Corticotropin-Releasing Hormone (CRH) from the hypothalamus (e.g. Koob, 1985) belongs to the family of stress hormones. For the majority of the pituitary and hypothalamic hormones neuronal cell bodies and axons with terminals can be localized in a number of brain regions outside the hypothalamus (see Nieuwenhuys, 1985). Accordingly, the brain should be added to the neuroendocrine compartment of the body: the brain is both a source and target of these hormones. These hormones with oligo- or polypeptide structures, are designated as neuropeptides both because of their action on nervous tissue (De Wied, 1987) and their neuronal origin (Bloom, 1987).