Cholecystokinin receptor subtypes: role in the modulation of anxiety-related and reward-related behaviours in animal models.

Cholecystokinin (CCK) is an abundant and widely distributed neuropeptide that plays a modulatory role in a variety of behaviours. This paper focuses on the role of CCK in modulating anxiety-related and reward-related behaviours in key brain regions of the amygdala and mesolimbic dopamine system, respectively. The role of CCK in mediating aspects of these behaviours has been studied in a variety of behavioural paradigms, but inconsistent results have led to confusion regarding the precise role of the receptor subtypes in mediating behaviour. The confusion in the literature may come in part from the diverse behavioural paradigms that are used, the differences in regional effects of CCK manipulations in different areas and at different receptor subtypes in these areas and the dependence of the behavioural outcome on the baseline state of arousal of the animal. Evidence on the role of CCK in anxiety-related and reward-related behaviours in various animal models indicates that CCK-B receptors in the basolateral amygdala are important mediators of anxiety-related behaviours and that CCK-A and CCK-B receptors in the nucleus accumbens are important in mediating different aspects of reward-related behaviour. Emphasis is placed upon the role of CCK as a neuromodulator that is recruited only under conditions of high frequency neuronal firing.