Effects of essential fatty acid administration on cardiovascular responses to stress in the rat

This study examined the effects of 18:2(n-6), 18:3(n-6), 20:4(n-6) and 18:3(n-3) on cardiovascular responses to isolation stress in male rats. Group-acclimated rats were fasted for 2 days, then placed on a fat-free diet. Two wk later animals were divided into six groups (six animals per group) and given eight-wk intraperitoneal osmotic pumps releasing 1.47 X 10(-7) mol/hr of either olive oil (OL), or of 18:2(n-6), 18:3(n-6), 20:4(n-6) or 18:3(n-3) in OL. Another group received dummy pumps. Two wk after pump implantation, animals were isolated for four wk. Blood pressure (BP), heart rate and body weight were followed before and during stress. Following the stress period, animals were assessed for cardiovascular reactivity to norepinephrine (NOR) and angiotensin (ANG). Prior to isolation, 18:3(n-6) lowered BP vs OL (p less than 0.01). Stress increased BP within 24 hr in all groups except 18:3(n-6) and 20:4(n-6). Treatment with 20:4(n-6) vs OL prevented the BP rise (p less than 0.001) only for the first two wk of stress. Administration of 18:3(n-6) vs OL prevented any BP increase over the four-wk stress period (p less than 0.001). Stress increased heart rate in all groups except 20:4(n-6). Heart rate was lowered by 18:3(n-6) vs OL (p less than 0.01) before and during stress. Vascular reactivity to NOR was unaffected by treatment, but OL and 18:3(n-6) decreased responses to ANG infusion. These data suggest that 18:3(n-6) supplementation attenuates cardiovascular responses to chronic stress, and that delta 6- and delta 5-desaturase activity are inhibited during chronic psychological stress.