Beschreibung:
<jats:p>Pre‐exposure to L‐arginine (L‐arg, micropipette) preconditions individual arteriolar networks by 15 minutes after the pre‐exposure interval. Preconditioning is seen as a change in response to L‐arg from constriction to dilation (Microcirculation, 2007:14, 739–751). We hypothesized that tissue bath pre‐exposure to L‐arg would precondition all arterioles uniformly at a common threshold concentration. The cheek pouch of anesthetized (70 mg/kg pentobarbital) male hamsters (n=10) was prepared for intravital microscopy. Diameter change was measured as a function of L‐arg (5 min, 10–11‐ 10‐7M), either without preconditioning (PC, control) or with PC (15 min of L‐arg 10–11‐ 10‐7M) followed by a 15 min waiting period. Data was obtained from each sequential branch point of the network (1st, 2nd, 3rd, last), and at 3 segments in each bifurcation (Feed, Feed continuation, Branch). At low L‐arg, all arterioles constricted ± PC. The dose of L‐arg to PC all networks (Initiation Threshold) was ∼10‐7M. Separately, we examined the test dose of L‐arg where dilation was first seen (Experimental Threshold, ET). ET did not vary by branch vs. feed designation. ET varied along the length of network; ET upstream was ∼ 10‐7M while downstream was lower (∼10‐10M). We conclude that network position predicts the extent of altered arteriolar vasoactive responses for tissue bath preconditioning. (AHA 0655908T)</jats:p>