Tropisetron, a 5-HT(3) receptor antagonist, enhances object exploration in intact female rats

The effects of a 5-HT(3) receptor antagonist, tropisetron, on cognitive functions were evaluated using the object-recognition test in estrous (postovulatory) and in diestrous female rats. Recognition was measured by the ability of rats to discriminate between a familiar and a new object in a T-maze after a 3-h delay. Rats from both stages spent equivalent amounts of time exploring the objects on trial 1. Three hours after trial 1, trial 2 (test trial) was initiated. Before the test trial, rats were injected with either saline or 1.5 or 2.5 mg/kg tropisetron. During the test trial, one arm of a T-maze contained an object from trial 1 (familiar) and a new object (novel) was introduced into the other arm. Rats from both stages responded to tropisetron by showing a greater percentage of time exploring the novel object. These findings indicate that tropisetron facilitates cognition in female rats by improving the recognition of familiar information.