Locus coeruleus.

The locus coeruleus (LC) contains norepinephrine (NE)-synthesizing neurons that send diffuse projections throughout the central nervous system. The LC-NE system has a major role in arousal, attention and stress responses. In the brain, NE may also contribute to long-term synaptic plasticity, pain modulation, motor control, energy homeostasis and control of local blood flow. The LC is severely affected in neurodegenerative disorders including Parkinson disease (PD). Involvement of the noradrenergic neurons of the LC precedes that of dopaminergic neurons of the substantia nigra pars compacta and has been increasingly recognized as a potential major contributor to cognitive manifestations in early PD, particularly impaired attention. Abnormal noradrenergic signaling may also potentially contribute to motor manifestations of the disease.This makes the LC-NE system a major contributor to the pathobiology and potential target for therapy of PD.