Effects of hippocampal administration of a cannabinoid receptor agonist WIN 55,212-2 on spontaneous object and place recognition in rats.

Involvement of hippocampal cannabinoid receptors in short-term memory was investigated in rats using spontaneous object and place recognition memory tasks. Rats were allowed to explore the field in which two identical objects were presented. Then after a delay period, they were placed again in the same field in which one of the two objects was replaced by another object (object recognition task) or moved to another place (place recognition task), and their exploration behavior to these objects were analyzed. Activation of hippocampal cannabinoid receptors by an agonist WIN 55,212-2 (1-2 microg/side) dose-dependently decreased the exploration of object in a new place, while it did not affect the exploration of a new object. Disruptive effect of WIN 55,212-2 on place recognition was antagonized by the pretreatment with a cannabinoid receptor antagonist AM 281 (2mg/kg, i.p.). Results suggest that hippocampal cannabinoid receptors play an important role in place recognition or spatial memory.