Distribution Of The Extracellular Calcium-Sensing Receptors In The Cardiovascular Regulatory Regions In The Rat Brain

Decrease of calcium in the cerebrospinal fluid (CSF) raises blood pressure whereas increase of calcium lowers it. Although these phenomena have been known for more than 50 years, precise mechanism has not fully been understood. We examined whether the extracellular calcium-sensing receptor (CaSR), that was originally cloned from the parathyroid cells and later found in the brain, contributes to the blood pressure regulation by the calcium in the CSF. Cardiovascular regulatory neurons were identified by immunohistochemical detection of c-fos, a marker for cellular activation, in response to a rise in blood pressure by intravenous infusion of phenylephrine for 1 hr. Distribution of CaSR was identified using double immunostaining technique in the same brain section. Many neurons in the caudal ventrolateral medulla (CVLM) showed both of c-fos and CaSR-like immunoreactivity. These results indicate that an increase of calcium in the CSF may activate depressor neurons in the CVLM through CaSR on them.