AGT and Hypertension: Meanwhile, the immunohistochemical technique ensures the crucial role of the OVLT in the regulation of blood osmolality in rats, in which c-fos expression and TRPV1 protein expression levels in the neurons of the OVLT ascend in response to angiotensin II-induced hypertension, indicating that OVLT neurons are activated when exposed to high blood osmolality (Issa et al., 2012).