Cerebellar norepinephrine modulates learning of delay classical eyeblink conditioning: evidence for post-synaptic signaling via PKA.

The neurotransmitter norepinephrine (NE) has been shown to modulate cerebellar-dependent learning and memory. Lesions of the nucleus locus coeruleus or systemic blockade of noradrenergic receptors has been shown to delay the acquisition of several cerebellar-dependent learning tasks. To date, no studies have shown a direct involvement of cerebellar noradrenergic activity nor localized the post-synaptic response to cerebellar beta-noradrenergic receptor signaling. Using ipsilateral, localized infusions into cerebellar lobule HVI and interpositus (IP), we have established that blocking beta-noradrenergic receptors with propranolol significantly impairs acquisition of conditioned responses. Furthermore, interrupting activation of cAMP-dependent PKA in the cerebellum using Rp-cAMPS completely prevents acquisition. However, neither blocking beta-adrenergic receptors nor blocking PKA activation significantly interferes with performance of established conditioned responses when administered after the learned response is formed.