Rat meningeal and brain microvasculature pericytes co-express the vesicular glutamate transporters 2 and 3.

Pericytes are small cells that are apposed to brain and meningeal microvasculature and control capillary contraction, thereby regulating local cerebral perfusion. Pericytes respond to exogenously applied glutamate in vitro and express metabotropic glutamate receptors. However, it is unclear if pericytes have the capacity to release glutamate. We therefore determined whether pericytes express vesicular glutamate transporters (VGLUTs), which are considered to be unambiguous markers of cells that use glutamate as an intercellular signaling molecule. Leptomeningeal and brain microvasculature-associated pericytes of the adult rat, as defined by the presence of NG2 proteoglycan, expressed both VGLUT2- and VGLUT3-immunoreactivity, but did not express VGLUT1. Consistent with the hypothesis that pericytes release glutamate, VGLUT2- and VGLUT3-immunoreactivities appeared to be localized to secretory vesicles. These results suggest that glutamate is released from pericytes of the leptomeninges and brain microvasculature, and demonstrate for the first time the co-localization of VGLUT2 and VGLUT3.