ABSTRACT
Cell bodies of noradrenergic neurons are located in the pons and medulla. The most caudal groups, A1 and A2, send their axons into the spinal cord where they form synapses with the terminals of primary afferents. Noradrenergic neurons are small with fine, highly branched axons that ramify widely. The axons bear varicosities along their length, but they do not form close synaptic contacts, so release noradrenaline (NA) some distance from their targets. The major noradrenergic cell group is the locus ceruleus which contributes most of the axons of the dorsal noradrenergic bundle and projects to the cerebellum. Adrenoceptors are metabotropic receptors that are activated by both NA and epinephrine. Activity of the noradrenergic neurons cells causes a globally synchronized release of NA throughout much of the brain which acts to modulate neuron responses to input from other transmitters. Arousal is regulated by the widely distributed noradrenergic neurons.
