Evidence for widespread effects of noradrenaline on axon terminals in the rat frontal cortex

Noradrenaline, apparently working through activation of beta-adrenergic receptors, alters the state of phosphorylation of a substantial proportion of synapsin I in rat frontal cortex. Since synapsin I is enriched in virtually all axon terminals in this brain region, the results indicate that noradrenaline, a sparsely distributed neurotransmitter, affects a large number of axon terminals in this region. The results also suggest that noradrenaline receptors are present on a substantial percentage of all axon terminals in the cerebral cortex, despite the low density of noradrenergic fibers present. The data support the view that noradrenaline may serve a paracrine function.