Differential density of blood vessels in the mesencephalon of Macaque brain stem

The blood vessels (BV) of the brain stem show different patterns of development, and nutrient requeriments, metabolism and the activity of the different nuclei of the mesencephalon differ from one nucleus to another. The density of BV indirectly explains the blood flow intensity and physiological activity of the nuclei, and may explain the varying degrees of vulnerability of neurons to pathologies. To ascertain the different vascular densities of the mesencephalic nuclei, in the present work we used stereological methods to measure BV density in the Ventral Tegmental Area (VTA), the Substantia Nigra pars compacta (SNpc), the A8 Catecholaminergic Cell group (A8), the Periaqueductal Grey Matter (PAG) and the Locus Coeruleus (LC) of two intact macaques. The results pointed to a high density of BV in the LC; a low density in the SNpc, and an intermediate density in the VTA, A8 and PAG. These results confirm the high blood metabolism of the LC and suggest that the vulnerability of SNpc neurons may be related to the observed low density of BV.