The review article focuses in the differential activation of the hypothalamic - pituitary - adrenal (HPA) axis in generalized anxiety and panic. The results of experimental studies that assayed adrenocorticotropic hormone, cortisol and prolactin show that real-life panic attacks as well as those induced by selective panicogenic agents, such as lactate and carbon dioxide, do not activate the HPA axis. Accordingly, experiments carried out in two animal models of panic, namely electrical stimulationof the dorsal periqueductal gray matter of the rat and the escape fron the open arm of the elevated T maze, have shown that in neither case stress hormones are incrased in the plasma. Also in humans, reported results have shown that neither cortisol nor prolactin levels were increased following simulated public speaking, an experimental task that has been related to panic, in either healthy volunteers or partients with panic disorder diagnosis. Therefore, although anxiety activates both the HPA and the sympatho-adrenal axes.
