Cerebrovascular reactivity after experimental subarachnoid hemorrhage (SAH) in insulin resistant (IR) rats

Abstract

IR impairs cerebrovascular reactions to several stimuli in Zucker obese (ZO) rats. However, cerebral artery responses after SAH have not been described in IR. Hemolyzed blood (300μl) or saline was infused (10μl/min) into the cisterna magna of 11–13 week‐old ZO (n=15) and lean (ZL) rats (n=15). One day later, dilator responses of the basilar artery (BA) and its side branch (SB) to acetylcholine (ACh)(10−6M), cromakalim (10−7M, 10−6M) and sodium nitroprusside (SNP)(10−7M) were recorded with intravital videomicroscopy. Saline injected ZO animals showed reduced dilation to ACh (BA=7±4% vs. 21±5%; SB=20±5% vs. 37±8%) compared to ZL rats. Blood injection blunted the response to ACh in both the ZO (BA=4±3%; SB=11±3%) and ZL rats (BA=7±2%; SB=16±4%). Cromakalim (10−6M)‐induced dilation was significantly reduced both in the blood injected ZO animals compared to the saline control (BA=11±3% vs. 27±5%; SB=23±7% vs. 43±11%), and in the blood injected ZL rats vs. its saline control (BA=24±4% vs. 29±3%; SB=39±3% vs. 58±9%). No difference in SNP reactivity was observed. In summary, cerebrovascular reactivity to both endothelium‐ and smooth muscle‐dependent stimuli is severely compromised by SAH in IR animals.