Aging and motor learning: a possible role for norepinephrine in cerebellar plasticity.

Norepinephrine is known to act as a neuromodulator in the cerebellar cortex because it can increase the effect of neurotransmitters such as GABA. This neuromodulatory effect of NE is a possible substrate for an effect of NE on cerebellar plasticity. Cerebellar plasticity can be examined by studying the learning of motor skills. A rod walking paradigm is used in our laboratory for such investigations. Learning of this rod walking task is impaired in rats that are depleted of central stores of NE and in rats that have received the beta-adrenergic antagonist propranolol. In addition, in aged rats there is a correlation between the loss of beta-adrenergic receptor mediated neuromodulatory actions of NE in the cerebellum with a decreased ability to learn the rod walking task. Taken together this information supports a role for NE in cerebellar plasticity and suggest that the beta-adrenergic receptor is important for this plasticity.