The distribution of dopamine-beta-hydroxylase, neuropeptide Y and galanin in locus coeruleus neurons

The locus coeruleus (LC) is composed of noradrenaline-producing neurons that project widely throughout the neuraxis. Subpopulations of LC neuron perikarya have been shown to contain neuropeptide Y (NPY) and galanin (GAL). In the major terminal fields of LC projections, the cerebral cortex, dorsal thalamus and cerebellar cortex, there are differing plexuses of dopamine-beta-hydroxylase (DBH), NPY and GAL immunoreactive axons. DBH immunoreactive plexuses are found in all areas which conform in appearance to previous demonstrations of noradrenaline localization by fluorescence histochemistry. In contrast, there are few NPY immunoreactive axons in thalamus and cerebellum, and the cortical plexus, while similar to the DBH immunoreactive plexus, is not affected by 6-hydroxydopamine treatment. Similarly, there are few GAL immunoreactive axons in either cerebral cortex, dorsal thalamus or cerebellar cortex. Transection of ascending LC axons results in accumulation of DBH but not NPY or GAL immunoreactivity proximal to the lesion. These observations indicate that NPY and GAL are distributed differently in LC neurons from noradrenaline and DBH.