[Biochemical aspects of anxiety].

Alterations in biological systems may influence or accompany the symptoms of anxiety in human beings. Several biological systems such as the hypothalamic-pituitary-adrenal axis and the catecholaminergic systems may play important roles in the modulation of anxiety. The noradrenergic nucleus locus coeruleus may provide a useful model for the study and treatment of human feelings of fear, vigilance, alarm and anxiety. Substances that act selectively on this system, such as clonidine, may have anxiolytic properties. Furthermore, recent advances in the understanding of other neurotransmitter systems may have important implications. For example, the discovery of specific brain receptors for benzodiazepines (BDZ) and their endogenous ligands may result in more selective treatment of some conditions of pathological anxiety. The possible involvement of adenosine in the mode of action of both BDZ and methylxanthines such as caffeine may explain the antagonistic effects of these compounds.