In spite of its various anatomical, functional, and phylogenetic divisions, the rat cerebellum remains constant throughout, in its cellular and laminar organization. The question remains whether the microvascular supply of the cerebellum is quantitatively homogenous or not. This study aims to investigate quantitatively whether the homogeneity in cerebellar cellular architecture is reflected on the functional vascular bed in different regions of the cerebellum and to provide reliable morphometric parameters that can be used for comparative purposes with other regions in the central nervous system. A sample of 20 adult male albino rats was used. Fresh frozen 20 μm thick sections in the sagittal plane were stained for microvascular alkaline
phosphatase. Image analysis software (Global Lab Image), was used to measure circumscribed areas for the length and number density of their contained alkaline phosphatase positive microvascular profiles.
Microvascular densities in the cortical layers of the cerebellum as a whole was (76.72±30.59 count/mm2) and (231.45±82.14 mm/mm3). There was a higher microvascular density in the granular layer in comparison to the molecular layer. This was significantly higher than the densities of the white matter core excluding the deep cerebellar nuclei. The densities in the deep cerebellar nuclei were (122.86±20.38 count/mm2) and (328.22±33.45 mm/mm3). Length density did not show obvious heterogeneity in the cortical layers between different divisions of the cerebellum. Number density was significantly higher within the cortical layers of the hemisphere when compared to the vermis. A comprehensive guide for identifying rat cerebellar regions was put foreword. This guide can be useful for identifying rat cerebellum sagittal sections regardless of the level of the section or the staining method used without the need to follow an entire series of sections. The differences in microvascularity on the laminar level was correlated with the functional necessity of neurons and synapses. Neurovascular coupling appeared in its best manifestation in the deep cerebellar nuclei
where it was clear that dense microvascularity was concomitant with a densely synaptic and neuron-poor region. The cerebellar cortex as a whole, was homogenous in its microvascular length density in whichever division, anatomical, functional or phylogenetic. The predilection towards heterogeneity between vermian and hemispheric cortices as far as number density is concerned can be attributed to the complexity of branching for a given length of vessels. A combination of two morphometric parameters (microvascular length and number density) is a reasonable choice to explore the microvascular network in terms of functional needs and spatial composition