On the existence of mechanoreceptors within the neurovascular unit of the mammalian brain
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We describe a set of perivascular interneurons (PINs) with series of fibro-vesicular complexes (FVCs) throughout the gray matter of the adult rabbit and rat brains. PIN–FVCs are ubiquitous throughout the brain vasculature as detected in Golgi-impregnated specimens. Most PINs are small, aspiny cells with short or long (> 1 mm) axons that split and travel along arterial blood vessels. Upon ramification, axons form FVCs around the arising vascular branches; then, paired axons run parallel to the vessel wall until another ramification ensues, and a new FVC is formed. Cytologically, FVCs consist of clusters of perivascular bulbs (PVBs) encircling the precapillary and capillary wall surrounded by end-feet and the extracellular matrix of endothelial cells and pericytes. A PVB contains mitochondria, multivesicular bodies, and granules with a membranous core, similar to Meissner corpuscles and other mechanoreceptors. Some PVBs form asymmetrical, axo-spinous synapses with presumptive adjacent neurons. PINs appear to correspond to the type 1 nNOS-positive neurons whose FVCs co-label with markers of sensory fiber-terminals surrounded by astrocytic end-feet. The PIN is conserved in adult cats and rhesus monkey specimens. The location, ubiquity throughout the vasculature of the mammalian brain, and cytological organization of the PIN–FVCs suggests that it is a sensory receptor intrinsic to the mammalian neurovascular unit that corresponds to an afferent limb of the sensorimotor feed-back mechanism controlling local blood flow.
KeywordsReceptor Blood vessels Perivascular organ End-foot Central blood flow
This work was supported by CONACyT, Grant 1782 to LC and JL-S and by Universidad Nacional Autónoma de México, PAPIIT Grant IG200117 to LC and JL-S. The transgenic hGFAP-GFP mouse line was a generous gift from Dr. Helmut Kettenmann. Authors appreciate the numerous suggestions made from Dr. Carlos Cepeda on our manuscript and thank Gema Martínez-Cabrera, Carlos Lozano-Flores Flores, Lourdes Palma, Elsa Nydia Hernández-Ríos, Martín García, and Rafael Olivares for providing technical assistance. The thorough revision of our manuscript by Jessica González Norris and American Journal Experts is also appreciated.
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