Fig. 4.

Astrocytes and glioma cells regulate vascular tone a Astro-cytes regulate vascular tone by releasing vasoactive molecules that act on vascular smooth muscle cells (VSCM). The generation of these substrates is dependent on astrocyte activation via increased [Ca^2+]i. Raised [Ca²⁺]_i activates phospholipase A₂, which converts membrane phospholipids (PL) into arachidonic acid (AA). AA is either released directly or metabolized further into prostaglandins (PG) or epox-yeicosatrienoic acids (EETs). In addition, increased [Ca²⁺]_i causes activation of K_Ca channels expressed on the astrocyte, leading to the release of potassium (K⁺). b In the invading glioma cell, K⁺ release through K_Ca channels elicits changes in vascular tone. Glioma cells could also be releasing other vasoactive molecules, such as PGs or EETs, that act on VSMCs