Occipital Artery Function during the Development of 2-Kidney, 1-Clip Hypertension in Rats

This study compared the contractile responses elicited by angiotensin II (AII), arginine vasopressin (AVP), and 5hydroxytryptamine (5-HT) in isolated occipital arteries (OAs) from sham-operated (SHAM) and 2-kidney, 1-clip (2K-1C) hypertensive rats. OAs were isolated and bisected into proximal segments (closer to the common carotid artery) and distal segments (closer to the nodose ganglion) and mounted separately on myographs. On day 9, 2K-1C rats had higher mean arterial blood pressures, heart rates, and plasma renin concentrations than SHAMrats. The contractile responses toAIIwere markedly diminished in both proximal and distal segments of OAs from2K-1C rats as compared to those fromSHAMrats. The responses elicited by AVP were substantially greater in distal than in proximal segments of OAs from SHAM rats and that AVP elicited similar responses in OA segments from2K-1C rats. The responses elicited by 5-HT were similar in proximal and distal segments fromSHAMand 2K-1C rats. These results demonstrate that continued exposure to circulating AII and AVP in 2K-1C rats reduces the contractile efficacy of AII but not AVP or 5-HT. The diminished responsiveness to AII may alter the physiological status of OAs in vivo.