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Effect of decreased glucose concentration on cerebrovascular tone in vitro
M W Swafford1, S Raty, W F Childres
1Department of Anesthesiology, Baylor College of Medicine, Houston, Texas.
Abstract:
We studied the effect of decreased glucose concentration on cerebrovascular tone in vitro. Segments of rat middle cerebral arteries (MCA) were isolated, cannulated at both ends with glass micropipettes, and pressurized to 85 mm Hg. Decreasing the glucose in the extraluminal bath and luminal perfusate from 5.5 mmol/L to 1.0 or 0.5 mmol/L for 1.5 hours each had no significant effect on the diameter of the arteries. When all the glucose was removed from the extraluminal bath and luminal perfusate for 1.5 hours, the MCA dilated by 23% [252 +/- 24 (SD) microns to 311 +/- 7 microns (P < .5, n = 7)]. This dilation was 80% of the maximum dilation produced by removal of Ca+2 from the bathing solutions. Neither removal of the endothelium nor inhibition of the ATP-sensitive K channels with 10(-5) mol/L glibenclamide altered the response of the isolated MCA to the removal of glucose. We conclude that rat MCA are relatively more resistant to substrate limitation compared to the brain as a whole.
Insights
Decreasing glucose levels did not affect rat middle cerebral arteries (MCA) diameter. Complete glucose removal caused significant MCA dilation, indicating resistance to substrate limitation.
Area of Science:
- Neuroscience
- Vascular Biology
- Physiology
Background:
- Cerebrovascular tone is crucial for regulating cerebral blood flow.
- Glucose is the primary energy substrate for the brain.
- Understanding substrate limitations on cerebrovascular tone is important for neurological health.
Purpose of the Study:
- To investigate the in vitro effect of decreased glucose concentration on rat middle cerebral arteries (MCA) tone.
- To determine the MCA's response to varying levels of glucose deprivation.
Main Methods:
- Segments of rat MCA were isolated and pressurized in vitro.
- Glucose concentration in the extraluminal and luminal perfusate was systematically decreased.
- Arterial diameter changes were measured under different glucose conditions.
Main Results:
- Decreasing glucose from 5.5 mmol/L to 1.0 or 0.5 mmol/L had no significant effect on MCA diameter.
- Complete glucose removal resulted in a 23% dilation of MCA, reaching 80% of maximum Ca+2-depletion-induced dilation.
- Endothelium removal or ATP-sensitive K+ channel inhibition did not alter the dilation response to glucose removal.
Conclusions:
- Rat MCAs exhibit relative resistance to substrate limitation compared to the brain overall.
- The MCA's response to glucose deprivation involves mechanisms independent of the endothelium or ATP-sensitive K+ channels.