Distribution of Neuropeptide Y, C-Terminal Flanking Peptide of NPY and Galanin and Coexistence with Catecholamine in the Locus coeruleus of Normal Human, Alzheimer's Dementia and Parkinson's Disease Brains
The study demonstrates the presence of neuropeptide Y (NPY)-, C-terminal flanking peptide of NPY (C-PON)-, and galanin (GA)-immunoreactive (-i) neurons and axons in the locus coeruleus in normal adult human brain and in brains of patients with senile dementia of the Alzheimer type (SDAT) and Parkinson''s disease (PD) as well as evidence for the coexistence of peptides with catecholamines in individual locus coeruleus neurons. The morphology of C-PON-i neurons is analysed in detail with a computer-assisted program. They are either multipolar neurons with round or multiangular somata, or ''bipolar'' neurons with major dendrites issuing from the two poles of fusiform cell bodies, and represent small- to medium-sized locus coeruleus neurons. In the controls, C-PON-i and NPY-i neuron numbers are highest rostrally, lower in the middle and lowest in the caudal locus coeruleus. GA-i neurons are more frequent caudally. C-PON-i neuron numbers are decreased in old normal adult brains compared to young brains. NPY-i and GA-i neuron numbers are very low in all age groups. The axonal networks are densest rostrally. C-PON-i and NPY-i axons possess larger varicosities and thicker intervaricose segments than GA-i axons. Both the peptidergic neuronal systems and the innervation pattern are detrimentally altered in SDAT and PD, more so in the latter than in the former cases. In SDAT, some C-PON-i locus coeruleus neurons display morphological alterations resembling those encountered in tyrosine hydroxylase (TH)-i neurons in the same cases, with blurred somatic outlines, misshapen cell bodies and foreshortened dendrites. However, the alterations are generally less severe than those of the TH-i neurons and many C-PON-i neurons appear to be entirely normal. Relative to the number of TH-i neurons, the numbers of peptide-i neurons are higher in SDAT than in controls, and often more neurons are located caudally. Peptide-i axonal networks are less dense, and the remaining C-PON-i and NPY-i axons are tortuous and have larger varicosities than normal. In PD, the changes of C-PON-i neuronal morphology are as severe as in the TH-i neuron population, with rounded cell bodies and loss of dendritic arbors; the peptide-i innervation is reduced. The alterations in the peptide-i systems of the locus coeruleus, especially the increase in the numbers of neurons in SDAT, may be interpreted in terms of a plasticity of the aged brain.