Is shorter transient middle cerebral artery occlusion (t-MCAO) duration better in stroke experiments on diabetic female Sprague Dawely rats?

Aim: To determine optimal duration of transient middle cerebral artery occlusion (t-MCAO) for a stroke model in female diabetic Sprague-Dawley (SD) rats.

Methods: Streptozotocin-induced type-1 diabetic SD female rats (n = 25, 12 weeks old, five groups; n = 5 per group) were subjected to different duration of t-MCAO (20, 30, 45, 60 and 90 minutes) followed by reperfusion. A control group of rats without diabetes (n = 5) was subjected to 30 minutes of t-MCAO followed by reperfusion. Twenty-four hours after reperfusion, infarct volumes were evaluated by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

Results: Intra-ischaemic reductions of regional cerebral blood flow (rCBF) were similar in all groups (68-75% of baseline values). Reperfusion was significantly impaired in the 90-minute ischaemia group (56-62% vs 80-125% in other groups). Twenty minutes of t-MCAO induced a small infarct (3 ± 5% of ischaemic hemisphere). Thirty minutes of ischaemia produced a significantly larger infarct (46 ± 6%). In the 45 and 60 minute groups, ischaemia infarct was 52 ± 5% and 59 ± 3% of the ischaemic hemisphere, respectively. Ischaemia of 90' led to a massive stroke (89 ± 6% of ischaemic hemisphere encompassing the whole striatum (22 ± 3%) and almost the whole MCA irrigated cortex area (67 ± 6%)). Thirty minutes of t-MCAO did not produce stroke in the control group.

Conclusion: The diabetic rat stroke model should be different from the non-diabetic, because female type-1 diabetic SD rats are highly sensitive to brain ischaemia and it is necessary to significantly shorten the duration of t-MCAO, optimally to 30 minutes.