5-HT2 RECEPTOR INVOLVEMENT IN CONDITIONED OLFACTORY LEARNING IN THE NEONATE RAT PUP

These experiments addressed the role of 5-HT2 receptors in conditioned olfactory learning. Ritanserin, a 5-H-2A/2C antagonist, was injected subcutaneously into postnatal day (PND) 7 pups before or after conditi oned olfactory training to a peppermint odor. When the pups were teste d for olfactory preference on PND 8, those injected with ritanserin be fore training failed to acquire an odor preference whereas those injec ted after training learned. This suggested that the 5-HT2 receptor is required only in the acquisition of conditioned olfactory learning. In jection of ritanserin directly into the olfactory bulb before training also blocked preference for the peppermint odor. In pups that had dep letion of the 5-HT input to the bulb, subcutaneous injection of a 5-HT 2A/2C agonist was sufficient to maintain conditioned olfactory learnin g, confirming the importance of 5-HT in learning.