Gender and age-related differences in morphometric characteristics of neurons in human brain substantia nigra

Introduction. Age-related morphological changes in the brain and those taking place in Parkinson disease (PD) are similar in their nature but differ in intensity. Quantitative evaluation of the neurons’ characteristics in substantia nigra pars compacta (SNc) in men and women during aging will allow to use obtained values as a reference while studying PD.

Objective: to study gender- and age-related morphometric characteristics of neurons in SNc of the human brain.

Materials and methods. Morphometric evaluation of SNc neurons in autopsy human brain specimens (n=12) of normal aging men and women (aged 52–87 years) was performed. The sections were stained with cresyl violet and for thyrosine hydroxylase (dopamine marker). A total number of neurons and number of dopaminergic neurons in particular in ventral and dorsal regions of SNc were counted; cellular and nuclear size was also estimated.

Results. In the aging brain, the most pronounced morphological changes occur in the medial, lateral, and intermediate segments of the ventral region of SNc. In the medial segment, the overall neuronal density was decreased by 33%, while in the lateral and intermediate segments of the ventral region of SNc it was decreased by 23%. In the medial and in the lateral and intermediate segments, density of the dopaminergic neurons was decreased by 28% and 24% respectively. Survived neurons showed increased cellular size and reduced nuclear size. In women, basic morphometric characteristics of neurons in the lateral and intermediate segments of the ventral region of SNc were higher than in men.

Conclusions. In normal aging, involution of the brain structures in SNc is more pronounced in its ventral region. Interestingly, involution occurs more slowly in a female brain than in a male brain.