A nitric oxide synthase inhibitor delays the formation of learning-related neural activity in the cerebellar interpositus nucleus during rabbit eyelid conditioning

Inhibiting nitric oxide synthesis with L-nitro arginine methyl ester (L-NAME) has been found to retard the acquisition of the classically conditioned rabbit eyelid response. In the present study, rabbits received an SC injection of either L-NAME (an inhibitor of nitric oxide synthase) or its inactive stereoisomer, D-NAME, an hour before each daily training session. L-NAME retarded both the acquisition of conditioned responses and associated learning-related neural activity in the interpositus nucleus. There was no effect of L-NAME on spontaneous interpositus activity recorded during a period of time before trial onset. These findings indicate that nitric oxide may play a role in neuronal processes associated with the acquisition of the classically conditioned rabbit eyelid responses.