Cholecystokinin and learning and memory processes.

Cholecystokinin (CCK) is a classical brain-gut peptide that exerts a variety of physiological actions in the gastrointestinal tract and central nervous system. CCK occurs in several molecular forms of varying aminoacid length, the sulphated octapeptide (CCK-8) being the predominant form in the brain. CCK mediates its effects through interaction with specific receptors subdivided in two subtypes--CCK-A (present in the periphery and in few selected brain nuclei) and CCK-B (the predominant receptor subtype in the brain). CCK is implicated in variety of behavioral functions as satiety, anxiety, exploratory and locomotor activity and learning and memory. After a brief description of the distribution, molecular forms, release, inactivation, etc. of CCK in the brain, the present review summarizes the recent data on the role of CCK in learning and memory. The memory-enhancing effects of CCK have been demonstrated in various types of memory. Data showing that CCK-A receptors mediate mnemonic while CCK-B receptors mediate amnestic effects are also presented.