Cholecystokinin-induced anxiety in rats: relevance of pre-experimental stress and seasonal variations.

The anti-exploratory action of caerulein appears to be dependent on the pre-experimental stress of rats. Moreover, the seasonal variations of exploratory behaviour of rats are evident in the plus-maze model of anxiety. The reduced exploratory activity in summer appears to be related to the elevated density of CCK and 5-HT2 receptors in the brain.