CALCA and brain ischemia: Some studies have shown that in the acute phase of subarachnoid hemorrhage (SAH), the contraction of cerebral artery to endothelin-1 and 5-hydroxytryptamine increases, and the vasoconstriction induced by depolarization is significantly increased, while the secretion of endogenous CGRP into cerebrospinal fluid (CSF) is considered to have a protective effect on cerebral ischemia associated with vasospasm (Bründl et al., 2021; Li et al., 2021).