Cholecystokinin (CCK) plays an important role in both the alimentary t
ract and the central nervous system (CNS). At present it seems to be t
he most abundant neuropeptide in the CNS. This paper reviews the CCK n
euronal system and its interactions with gamma-aminobutyric acid (GABA
) and serotonin (5-hydroxytryptamine; 5-HT). In addition, its putative
role in anxiety will be discussed on the basis of animal data and stu
dies in healthy volunteers and panic disorder patients. According to t
hese investigations, the CCK4 challenge test fulfills most criteria fo
r an ideal panicogenic agent and evidence has been found that CCKB rec
eptor antagonists might possess anxiolytic properties in man.