Nucleus Pigmentosus Pontus?
Afferent projections to the rat locus coeruleus demonstrated by retrograde and anterograde tracing with cholera-toxin B subunit and Phaseolus vulgaris leucoagglutinin
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The Locus ceruleus, also spelled locus coeruleus, (Latin for 'the blue bit') is a nucleus in the brain stem (inferior to the cerebellum in the caudal midbrain/rostral pons) apparently responsible for the physiological reactions involved in stress and panic.
The locus coeruleus is a melanin containing, blue nucleus which resides in the on the dorsal wall of the upper pons, surrounded by the fourth ventricle. This nucleus is one of the main sources of norepinephrine in the brain, and is composed of mostly medium sized neurons. The melanin granules inside the LC are what contribute to its blue color and is also known as the nucleus pigmentosus pontus (which means heavy pigment in cells, located on the pons). The neuromelanin is formed by the polymerization of norepinephrine and is analagous to the black dopamine based neuromelanin in the substantia nigra.
The projections of this nucleus reach far and wide, innervating the spinal cord, the brain stem, cerebellum, the hypothalamus, the thalamic relay nuclei, amygdala, the basal telecephalon and the cortex. The norepinephrine from the LC has an excitatory effect on most of the brain, mediating arousal, and priming the brain’s neurons to be activated by stimuli. It has been said that a single noradrenergic neuron can innervate, via its branches, the entire cerebral cortex.
The locus coeruleus receives afferents from the hypothalamus, which makes sense as this is the main homeostatic control center of the brain, and an arousal system should know how to properly respond to changes in homeostasis. The cingulate gyrus and the amygdala, the two centers for the more emotional side of pain, and stress also innervate the LC. This innervation is logical, as sometimes emotional pain or stress can cause noradrenergic responses. The cerebellum and afferents from the raphe nuclei also project to the LC, particularly the raphe pontis and raphe dorsalis.
The locus ceruleus is widely studied in relation to clinical depression, panic disorder and anxiety. Some antidepressant medications including Reboxetine, Venlafaxine and Bupropion as well as ADHD medication Atomoxetine are believed to act on neurons in this area. This area of the brain is also intimately involved in REM sleep.
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