PMC

A. TAGs of CT without vasodilator group (CT_pre) was lower (steeper downslope) than those of vasodilator groups (CT_iv and CT_sub) on LAD and LCX (p = 0.051 for LAD, 0.005 for LCX). Whereas, those of RCA showed no significant difference (p = 0.600). B. CT with intravenous vasodilator (CT_iv) showed higher proxHU than that of CT_pre or CT_sub, especially in LCX (p = 0.013). LAD and RCA showed same trends, but no statistically significant difference was observed (p = 0.418 for LAD, 0.101 for RCA). CT_iv = CT with intravenous vasodilator, CT_pre = CT without vasodilator, CT_sub = CT with sublingual vasodilator, LCX = left circumflex artery, RCA = right coronary artery

Different paradigms represented in (i) to (iv) show different ways in which vasodilators can inhibit each other to create redundancy. i), a more singular relationship between vasodilator interactions where (A) inhibits (B), which can inhibit (C), which can inhibit (D). (D) is shown to be able to inhibit a vasodilator (C) because, if it did not, then inhibiting (D) alone should show a significant decrease in vasodilatation because there would be no redundant system to fill in for (D) if it was inhibited. ii), shows a scenario where one vasodilator can inhibit more than one vasodilator: (A) can inhibit both (B) and (C). (B) and (C) are shown to interact as well. If they did not, there would be no redundant system to replace the effects of (B) or (C) and inhibiting either (B) or (C) would result in a significant decrease in vasodilatation. iii), a slightly more integrated system of inhibition that is a variation of (A) where each vasodilator interacts with another vasodilator. iv), a more integrated network of vasodilator interactions where one group of interacting vasodilators can also interact with another group of interacting vasodilators. These are just a few potential relationships out of many, depending on how many vasodilators are involved and also on the complexity of the redundant networks.

Sixty-nine-year-old female. Postruptured right internal carotid artery aneurysm clipping. Angiography was done on the seventh day after the subarachnoid hemorrhage. Red, yellow, and green indicate the internal carotid artery, the middle cerebral artery, and the anterior cerebral artery, respectively. (a) Time-density curve for contrast medium for preintra-arterial injection of vasodilator. (b) Integration curve for contrast medium for the preintra-arterial injection of vasodilator. (c) Time-density curve for contrast medium for the postintra-arterial injection of vasodilator. (d) Integration curve for contrast medium for the postintra-arterial injection of vasodilator.

The PNA responses are determined in young and old A) intact, B) ovariectomized (OVX), and C) ovariectomized and estrogen replaced (OVX+E2) female rats. A. There was an age-related difference in vasodilator responses between young and old INTACT female rats. Blockade with L-NAME significantly reduced vasodilation in both groups (P<0.05) and abolished the age-related difference in the vasodilator response. The combined blockade with L-NAME and Indo further reduced PNA vasodilation in the young rats (P<0.05). B. There were no differences in the vasodilator response between young and old OVX rats under any of the three conditions. Blockade with L-NAME significantly reduced vasodilation in both groups (P<0.05), and the combined blockade further diminished vasodilation in both OVX groups (P<0.05). C. There were no differences in vasodilator responses between young and old OVX+E2 rats under any of the three conditions. Inhibition with L-NAME significantly reduced vasodilation in both groups (P<0.05), whereas the combined L-NAME & Indo blockade had no further effect than L-NAME alone. Values are means ± S.E; n = 9–11 animals per group. *Indicates the vasodilator response is significantly different between groups (P<0.05).