Opposite regulation of brain angiotensin type 1 and type 2 receptors in cold-induced hypertension

Rats exposed chronically to mild cold (5°C/41°F) develop hypertension. This cold-induced hypertension (CIH) is an environmentally induced, non-surgical, non-pharmacological and non-genetic model for studying hypertension in rats. The blood renin angiotensin system (RAS) appears to play a role in both initiating and maintaining the high blood pressure in CIH. The goal of the present study was to evaluate the role of brain angiotensin type 1 and type 2 receptors (AT 1 R and AT 2 R) in CIH. Sprague–Dawley adult male rats were used. Thirty-six rats were kept in a cold room at 5°C and the other 36 were kept at 24°C as controls. Systolic blood pressure (SBP) was recorded by tail cuff. The SBP was elevated in rats exposed to cold within 1 week ( n=12, P>0.05), significantly increased at 3 weeks ( P