[Peptides and anxiety]

The discovery of the role of neuropeptides in information processing within the central nervous system has brought a new dimension in the research for biological basis of affective disorders and mental diseases. Various peptides with a high binding affinity for benzodiazepine receptors have been isolated but none of them can be considered as a true endogenous ligand. Various peptides present agonist or antagonist activities in different pharmacological tests for anxiolytic activity but their main effects are different. Naloxone is able to antagonize several effects of benzodiazepines in animals and humans, which suggests that endorphins are involved in anxiolytic properties of these drugs. Neuropeptides may have anxiogenic or anxiolytic-like action related to the neuroendocrine modulation of acquisition and retention of adaptive behaviours in stress situations. In addition neuropeptides such as alpha-MSH, bombesin and mainly CRF may regulate neurohormonal responses to stress. Finally evidence is presented to suggest that neuropeptides may be involved in the critical stages of emotional development, to allow associations between visceral changes and inner representation of significant environmental stimuli. The modulation by ACTH peptides of the imprinting process in birds is an example of such a possibility.