Method of Intra‐Arterial Administration in a transient MCAO Rat model to mimic the treatment of the human patient
Authors: Goodwin Sarah , Roberts Jill , Pennypacker Keith , Fraser Justin 
Published: April 2020

Endovascular thrombectomy is routinely performed in patients undergoing a large vessel occlusion. This process not only allows for the removal of a blood clot but also for the selective delivery of potential therapeutics directly to the site of injury. The intra‐arterial (IA) route of drug administration in the mouse was developed to bridge the gap between animal stroke treatments and clinical stroke therapy. We have previously shown this delivery method targets the site of injury while blunting systemic effects that have proven problematic with intraperitoneal routes. Here, we adapted the IA method for use in rats, combining it with a clinically relevant large vessel occlusion stroke model (MCAO). Our goal was to characterize variances in the model in order to optimize potential therapeutic delivery methods to the ipsilaterally affected hemisphere. Male and female Sprague‐Dawley rats (4 months of age) were subjected to placement of micro‐angio tubing at the bifurcation of the common carotid artery (CCA), with delivery through the internal carotid artery (ICA). We then determined the optimal infusion rate and volume using injection of India ink and evaluation of vascular distribution within the brain and the liver. Importantly, we found the infusion rate and volume varied depending on sex and body weight. India ink was selectively delivered to the ipsilateral side of the brain in males (370–460 g) at 4 μl/min with a max volume of 25 μl and in females (250–300 g) at 2.5 μl/min with a max volume of 25 μl. Following these guidelines, no ink was observed in the liver of these animals, indicating reduced systemic circulation of administered compounds. We then performed a 5‐hour transient MCAO, on male and female Sprague‐Dawley rats (4 months of age), to mimic human stroke, since 5 hours is the average time from the clinical presentation of stroke to the thrombectomy procedure. A silicone coated monofilament was advanced till resistance was felt, occluding the MCA territory. At the 5 hour time point, we removed the monofilament and inserted the mico‐angio tubing at the same entry point on the bifurcation of the CCA. We performed variant injections using different volumes and rates, measuring delivery of dye (India Ink) and rate of induced subarachnoid hemorrhage. A rate of 4 ul/min with a max volume of 25 ul was optimal in males, and a rate of 2.5 ul/min with a max volume of 25 ul was optimal in females. The results showed that, even with a large vessel occlusion, and removal of the monofilament (recanalization), the IA injection using these sex‐specific rates and volumes resulted in appropriate limited dye delivery without ruptured subarachnoid hemorrhage. This IA method is ideally suited for combination with the MCAO stroke model and mirrors the human patient undergoing an endovascular thrombectomy. This model provides an investigative opportunity to test neuroprotective drugs and other pharmacotherapies.

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University of Kentucky Center for Advanced Translational Stroke Science, Surgery Core