Hypertensive effects of central angiotensin II infusion and restraint stress are reduced with age

Benedek Erdos..and Nihal Tumer Introduction: It is well known that the risk of cardiovascular disease increases with age, and that blood pressure regulation specifically decreases with age. This deregulation can then account for age-related increases in hypertension which is correlated to morbidity and mortality. Angiotensin II is is a primary regulator in BP, through the alterations in baroreflex sensitivity and stress-induced sympathetic nervous system responses. However, the effects of age on Ang II mechanisms are unknown. It has already been shown that inhibition of Ang II type 1 (AT1) can reduce age related increases in the risk of cardiovascular disease. Here the authors look to study the effect of Ang II on BP, HR, sBRS and central oxidative stress and their differences in young and old rats. Methods: -Spontaneous baroreflex sensativity test -Restraint stress test -Western Blot -Reverse transcriptase-PCR -Electron paramagnetic resonance Results: -Resting MAP were increased in older rats with a decrease in HR and locomotor activity. After an AngII infusion in young and old rats show an increase in both cohorts in MAP, however the increase was stunted in the older rats compared to the young. Post infusion showed that HR increased in both cohorts equally. And finally varition of HR was reduced by 50% in the older cohort. -Throughout the entire study telometry systems were used to study sBRS and found that older rats had decreased sBRS compared to young rats, and after AngII infusions this SBRS was significantly reduced in the young rats. -After performing restraint stress tests, MAP, and HR responses were recorded. It was found that HR and MAP both had a rapid increase. After the addition of an AT1 inhibitor they found that stress-induced MAP elevations were reduced significantly in both groups. HR on the other had did not have any significant change after AT1 inhibition. Later, evaluation of hypothalamic tissues found decreased AT1 receptor protein and mRNA levels in older animals. ~JI